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Abstract

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OBJECTIVES

Papillary muscle repositioning in functional mitral regurgitation (FMR) alleviates mitral valve (MV) tenting by reducing the distance between papillary muscle tips and MV annular plane, i.e. apical left ventricular (LV) displacement. We aimed to quantify the effect of papillary muscle repositioning on papillary muscle geometry and to evaluate whether improved papillary muscle geometry after papillary muscle repositioning translates into the global LV reverse remodelling in FMR type IIIb.

METHODS

Patients with severe FMR type IIIb were prospectively enrolled and underwent pre- and postoperative 1.5-T cardiac magnetic resonance imaging. A new variable was defined, the papillary muscle to mitral annulus distance, which quantifies the distance between papillary muscle tips and MV annular plane. All parameters were measured by 2 independent investigators.

RESULTS

A total of 63 patients were enrolled. In all patients, papillary muscle to mitral annulus distance correlated significantly with established markers of LV remodelling and MV tenting severity. In patients who underwent subannular papillary muscle repositioning procedure (surgical cohort, n = 23), preoperative median papillary muscle to mitral annulus distance was 30 mm [interquartile range (IQR): 27–34 mm] and was significantly reduced postoperatively to 25 mm (IQR: 21–27 mm) (P = 0.001). LV end-diastolic diameter was reduced from 66 mm (IQR: 60–71) preoperatively to 58 mm (IQR: 53–67) after the surgery (P = 0.001).

CONCLUSIONS

MV repair with papillary muscle repositioning results in a papillary muscle to mitral annulus distance reduction and significantly improved MV tenting parameters. Improved papillary muscle geometry after papillary muscle repositioning is associated with a global LV reverse remodelling and may, thereby, improve the prognosis of FMR patients.

Functional mitral regurgitation, Subannular mitral valve repair, Cardiac MRI, Left ventricular geometry, Left ventricular remodelling

INTRODUCTION

Functional mitral regurgitation (FMR) type IIIb is a valvular disorder that is a sequel of eccentric left ventricular (LV) remodelling. This condition causes an apico-lateral papillary muscle displacement with subsequent restrictive movement of mitral valve (MV) leaflets during the systole (i.e. tenting) and leads thereby to an inadequate and incomplete MV closure [1, 2]. The historical treatment strategy was an isolated MV annuloplasty. However, isolated MV annuloplasty does not address papillary muscle displacement and is associated with an unacceptably high recurrence rate of mitral regurgitation (MR) [3]. Alternatively, MV replacement is associated with an increased perioperative morbidity and mortality [4]. Therefore, the most appropriate treatment strategy in FMR type IIIb patients still remains controversial [5].

Different subannular techniques including papillary muscle repositioning have been developed to address papillary muscle displacement in FMR [6]. So far, short- to mid-term clinical outcomes of such subannular techniques are promising, and a significant reduction of recurrent MR > grade 2 has been achieved in comparison to isolated annuloplasty [7].

However, the proof of a positive effect of subannular MV repair on papillary muscle geometry is still lacking. In other words, there are no imaging studies demonstrating the correction of apico-lateral papillary muscle displacement after papillary muscle repositioning manoeuvres. Furthermore, it is unclear whether improved MV competence translates into global LV reverse remodelling [8]. Therefore, we aimed (i) to quantify the effect of papillary muscle repositioning on papillary muscle geometry in FMR type IIIb patients by measurement of papillary muscle distances using cardiac MR imaging and (ii) to evaluate whether improved papillary muscle geometry after papillary muscle repositioning translates into the global LV reverse remodelling in FMR type IIIb.

MATERIALS AND METHODS

Ethics statement

The institutional ethics committee approved the prospective study, and all subjects gave written informed consent (Ethical Committee of Medical Council, Hamburg, Germany; PV5382). All authors had full control of the data and the material submitted for publication.

Patients

Patients with type IIIb FMR were prospectively included between May 2017 and June 2019. Inclusion criteria were defined by (i) reduced systolic left ventricular ejection fraction <50%, (ii) LV dilatation [left ventricular end-diastolic diameter (LVEDD) >55 mm], (iii) tenting of the posterior and/or anterior MV leaflet (tenting height >10 mm) and (iv) the criteria of severe FMR with reduced systolic MV leaflet motion (i.e. EROA >20 mm2/regurgitant volume >30 ml/beat). Exclusion criteria were: (i) degenerative MV disease, (ii) simultaneous aortic valve surgery, (iii) redo procedures, (iv) severe obesity and (v) metallic foreign body or claustrophobia contraindicating magnetic resonance imaging (MRI) examination. Patients with a concomitant atrial fibrillation, a relevant tricuspid regurgitation or underlying coronary artery disease that required simultaneous procedures were not excluded.

Our institutional strategy was to regularly evaluate all FMR patients in our out-patient heart failure unit. Based on individual patient characteristics and predicted surgical risk all patients were evaluated by an institutional multidisciplinary heart team. Guideline-directed medical therapy was the primary treatment strategy in all FMR patients. Those FMR patients with persisting severe MR and New York Heart Association III–IV symptoms, despite full-dose heart failure medication, were considered as candidates for MV intervention. Therapeutic decision-making included mechanical assist device implantation, catheter-based MV therapy (e.g. percutaneous edge-to-edge procedures or transcatheter valve implantations) as well as surgical valve repair.

Surgical technique

Patients who underwent MV annuloplasty with simultaneous papillary muscle repositioning formed the ‘surgical cohort’. The ‘control group’ consisted of patients who underwent isolated MV annuloplasty without subannular repair.

Surgical access was either minimally invasive using a right anterolateral minithoracotomy and 3D guidance [9] or median sternotomy depending on concomitant cardiac procedures and patients’ comorbidities. Standard MV annuloplasty consisted of implantation of a rigid or semi-rigid complete annuloplasty ring, which was downsized by 1 size, according to the length of the anterior mitral leaflet.

The ring downsizing by 2 sizes was an established surgical technique in case of isolated annuloplasty. Given the fact that an additional papillary muscle repositioning manoeuvre for tenting correction has been implemented, the downsizing by 2 sizes was not required. A sufficient coaptation surface was created by reduction of the tenting height and ring annuloplasty has an aim of stabilizing the result of papillary muscle repositioning.

Papillary muscle repositioning was conducted by realignment of both papillary muscles using polytetrafluorethylene sutures as previously described [6]. Subannular procedures were performed by 5 experienced MV surgeons and were all supervised by the senior author of the manuscript (Evaldas Girdauskas) with 15+ years of experience. A detailed video is provided showing all surgical steps in sequence (Video 1).

Cardiac MR imaging

All FMR patients underwent baseline cardiac MRI preoperatively. Patients in the ‘surgical cohort’ and ‘control group’ underwent additionally postoperative follow-up cardiac MRI 1 year after MV surgery.

All cardiac MR imaging examinations were conducted in the same fashion at 1.5-T (Archieva; Philips Medical Systems, Best, Netherlands). The imaging protocol included an ECG-gated, standard steady-state free-precession cine MR sequence, acquired during breath holds in standard long-axis views (four-, three- and two-chamber view) and short-axis slices covering the entire left ventricle.

Cardiac MR imaging analysis

Two investigators (Martin Sinn and HR, with 6 and 2 years of experience in reading cardiac MR images, respectively) independently and blindly performed all MRI measurements repetitively 2 times, at baseline and during the follow-up using certified software (cmr42, Circle Cardiovascular Imaging Inc., Calgary, Canada). CMR parameters are given as the mean of the 2 observers.

Functional LV parameters as well as LVEDD and LV end-systolic diameter (LVESD) were measured in standard fashion on short-axis cine images and were indexed to the calculated body surface area [10].

All LV geometric parameters were measured at mid-systole. Annular diameter of the MV, tenting height (distance between the leaflet coaptation point and the mitral annular plane), tenting area (area enclosed between the annular plane and the mitral leaflets) and tenting angle of posterior and anterior mitral leaflet were all measured in the three-chamber view [11]. Interpapillary muscle distance (IPMD) was measured as the shortest distance between the tips of the PM on a short-axis slices [12].

We defined a new parameter to measure the distance from the annular plane to the tips of the papillary muscles, the so-called ‘papillary muscle to mitral annulus distance’ (PMAD): on a mid-systole three-chamber view, the distance was drawn orthogonal from the annular plane to the tip of the papillary muscle plane. Often the tip of the papillary muscle is not covered on the three-chamber view. Therefore, the plane of the papillary muscle tip was determined on short-axis slices and subsequently the cross-reference to the three-chamber view was used to determine the tip of the papillary muscle plane (Fig. 1). In the particular case where the papillary muscle plane was not parallel to the annulus plane, the mean value of PMAD was taken for the posterior and anterior papillary muscles.

Evaluation of left ventricular geometry parameters. (A) Mitral valve geometry parameters such as tenting height, annular diameter and tenting angle of posterior and anterior mitral leaflet were all measured at mid-systole in the three-chamber view. (B) Interpapillary muscle distance was taken as the shortest distance between the tips of the papillary muscles on a mid-systolic short-axis slice. (C) Papillary muscle to mitral annulus distance was drawn orthogonal to the annular plane (dashed line) on a three-chamber view whilst cross-referencing the tip of the papillary muscle on the short-axis slice. The yellow line indicates the cross-reference line for the corresponding short-axis slice (B). AD: annular diameter; ALPM: anterolateral papillary muscle; Ao: aorta; ATA: anterior tenting angle; IPMD: interpapillary muscle distance; LA: left atrium; LV: left ventricle; PMAD: papillary muscle to mitral annulus distance; PMPM: posteromedian papillary muscle; PTA: posterior tenting angle; TH: tenting height.
Figure 1:

Evaluation of left ventricular geometry parameters. (A) Mitral valve geometry parameters such as tenting height, annular diameter and tenting angle of posterior and anterior mitral leaflet were all measured at mid-systole in the three-chamber view. (B) Interpapillary muscle distance was taken as the shortest distance between the tips of the papillary muscles on a mid-systolic short-axis slice. (C) Papillary muscle to mitral annulus distance was drawn orthogonal to the annular plane (dashed line) on a three-chamber view whilst cross-referencing the tip of the papillary muscle on the short-axis slice. The yellow line indicates the cross-reference line for the corresponding short-axis slice (B). AD: annular diameter; ALPM: anterolateral papillary muscle; Ao: aorta; ATA: anterior tenting angle; IPMD: interpapillary muscle distance; LA: left atrium; LV: left ventricle; PMAD: papillary muscle to mitral annulus distance; PMPM: posteromedian papillary muscle; PTA: posterior tenting angle; TH: tenting height.

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Statistical tests

Statistical analysis was performed by using SPSS for MacOS, version 25.0 (IBM SPSS Statistics, Armonk, NY, USA). Descriptive statistics were used to outline the study population. All MR imaging data are presented as means of the measurements from the 2 observers [Martin Sinn and Haissam Ragab (HR)]. Data are given as median and interquartile range (IQR) or as mean and standard deviation (SD). Interobserver agreement was determined by using the intraclass correlation coefficient. Independent samples were compared by using Mann–Whitney U tests. Wilcoxon signed rank test was used to test paired samples, such as LV parameters before and after annuloplasty. Linear regression was used to classify MV geometry parameters employing Spearman rho. P < 0.05 was considered as a statistically significant difference. We performed a post hoc power analysis to calculate the retrospective power of the observed effects based on the sample size of patients in the surgical cohort.

RESULTS

Study population

Sixty-three patients with type IIIb FMR were prospectively enrolled. A total of 23 patients underwent MV surgery with a simultaneous papillary muscle repositioning (surgical cohort), while the remaining patients underwent an isolated MV annuloplasty (control group) (n = 12) or were treated medically (n = 28).

Characteristics of all patients (n = 63) are displayed in Table 1. This cohort [median age 65 years (IQR 55–71 years), 63% male] represents a typical patients’ cohort with cardiomyopathy and symptomatic systolic heart failure with 83% patients in New York Heart Association functional class III–IV. Cardiac MRI analysis revealed a dilated LV [median LVEDD 65 mm (IQR 61–71 mm)] and increased left ventricular end-diastolic volume index (LVEDVi) 122 ml/m2 (IQR 97–144 ml/m2) with severe MV tenting [i.e. median tenting height of 12 mm (IQR 10–14 mm) and tenting area of 218 mm2 (IQR 165–267 mm2)] and reduced systolic LV function [median left ventricular ejection fraction 36% (IQR 29–40%)].

Table 1:
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Baseline characteristics for all 63 patients

CharacteristicsAll patients, n = 63
Age at time of operation (years)65 (55–71)
Male, n (%)40 (63)
BMI (kg/m2)27 (24–30)
Concomitant diseases, n (%)
 Hyperlipidaemia31 (50)
 Smoking23 (37)
 Arterial hypertension32 (52)
 Diabetes18 (29)
 Coronary artery disease43 (69)
 Atrial fibrillation19 (31)
proBNP (ng/l)2098 (1054–5005)
NYHA III–IV, n (%)52 (83)
Ischaemic MR, n (%)42 (67)
FMR due to dilated cardiomyopathy, n (%)21 (33)
Echocardiographic parameters
 Baseline LVEF (%)35 (30–40)
 LVEDD (mm)61 (55–65)
 TAPSE (mm)18 (16–20)
 Pulmonary artery pressure (mmHg)55 (44–58)
Cardiac MRI parameters
 Tenting height (mm)12 (10–14)
 Annular diameter (mm)36 (33–41)
 Tenting area (mm2)218 (165–267)
 Ant. tenting angle (°)33 (29–37)
 Post. tenting angle (°)39 (34–46)
 IPMD (mm)26 (22–29)
 PMAD (mm)31 (27–34)
 LVEDVi (ml/BSA)122 (97–144)
 LVESVi (ml/BSA)84 (59–99)
 LVSVi (ml/BSA)42 (33–49)
 LVEF (%)36 (29–40)
 LVEDD (mm)65 (61–71)
 LVESD (mm)52 (46–61)
CharacteristicsAll patients, n = 63
Age at time of operation (years)65 (55–71)
Male, n (%)40 (63)
BMI (kg/m2)27 (24–30)
Concomitant diseases, n (%)
 Hyperlipidaemia31 (50)
 Smoking23 (37)
 Arterial hypertension32 (52)
 Diabetes18 (29)
 Coronary artery disease43 (69)
 Atrial fibrillation19 (31)
proBNP (ng/l)2098 (1054–5005)
NYHA III–IV, n (%)52 (83)
Ischaemic MR, n (%)42 (67)
FMR due to dilated cardiomyopathy, n (%)21 (33)
Echocardiographic parameters
 Baseline LVEF (%)35 (30–40)
 LVEDD (mm)61 (55–65)
 TAPSE (mm)18 (16–20)
 Pulmonary artery pressure (mmHg)55 (44–58)
Cardiac MRI parameters
 Tenting height (mm)12 (10–14)
 Annular diameter (mm)36 (33–41)
 Tenting area (mm2)218 (165–267)
 Ant. tenting angle (°)33 (29–37)
 Post. tenting angle (°)39 (34–46)
 IPMD (mm)26 (22–29)
 PMAD (mm)31 (27–34)
 LVEDVi (ml/BSA)122 (97–144)
 LVESVi (ml/BSA)84 (59–99)
 LVSVi (ml/BSA)42 (33–49)
 LVEF (%)36 (29–40)
 LVEDD (mm)65 (61–71)
 LVESD (mm)52 (46–61)

Data are median (IQR) or n (%).

BMI: body mass index; BSA: body surface area; FMR: functional mitral regurgitation; IPMD: interpapillary muscle distance; IQR: interquartile range; LVEDD/LVESD: left ventricular end-diastolic and end-systolic diameters; LVEDVi/LVESVi: left ventricular end-systolic and end-diastolic volume index; LVEF: left ventricular ejection fraction; LVSVi: left ventricular stroke volume index; MR: mitral regurgitation; NYHA: New York Heart Association; PMAD: papillary muscle to mitral annulus distance; TAPSE: tricuspid annular plane systolic excursion.

Table 1:
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Baseline characteristics for all 63 patients

CharacteristicsAll patients, n = 63
Age at time of operation (years)65 (55–71)
Male, n (%)40 (63)
BMI (kg/m2)27 (24–30)
Concomitant diseases, n (%)
 Hyperlipidaemia31 (50)
 Smoking23 (37)
 Arterial hypertension32 (52)
 Diabetes18 (29)
 Coronary artery disease43 (69)
 Atrial fibrillation19 (31)
proBNP (ng/l)2098 (1054–5005)
NYHA III–IV, n (%)52 (83)
Ischaemic MR, n (%)42 (67)
FMR due to dilated cardiomyopathy, n (%)21 (33)
Echocardiographic parameters
 Baseline LVEF (%)35 (30–40)
 LVEDD (mm)61 (55–65)
 TAPSE (mm)18 (16–20)
 Pulmonary artery pressure (mmHg)55 (44–58)
Cardiac MRI parameters
 Tenting height (mm)12 (10–14)
 Annular diameter (mm)36 (33–41)
 Tenting area (mm2)218 (165–267)
 Ant. tenting angle (°)33 (29–37)
 Post. tenting angle (°)39 (34–46)
 IPMD (mm)26 (22–29)
 PMAD (mm)31 (27–34)
 LVEDVi (ml/BSA)122 (97–144)
 LVESVi (ml/BSA)84 (59–99)
 LVSVi (ml/BSA)42 (33–49)
 LVEF (%)36 (29–40)
 LVEDD (mm)65 (61–71)
 LVESD (mm)52 (46–61)
CharacteristicsAll patients, n = 63
Age at time of operation (years)65 (55–71)
Male, n (%)40 (63)
BMI (kg/m2)27 (24–30)
Concomitant diseases, n (%)
 Hyperlipidaemia31 (50)
 Smoking23 (37)
 Arterial hypertension32 (52)
 Diabetes18 (29)
 Coronary artery disease43 (69)
 Atrial fibrillation19 (31)
proBNP (ng/l)2098 (1054–5005)
NYHA III–IV, n (%)52 (83)
Ischaemic MR, n (%)42 (67)
FMR due to dilated cardiomyopathy, n (%)21 (33)
Echocardiographic parameters
 Baseline LVEF (%)35 (30–40)
 LVEDD (mm)61 (55–65)
 TAPSE (mm)18 (16–20)
 Pulmonary artery pressure (mmHg)55 (44–58)
Cardiac MRI parameters
 Tenting height (mm)12 (10–14)
 Annular diameter (mm)36 (33–41)
 Tenting area (mm2)218 (165–267)
 Ant. tenting angle (°)33 (29–37)
 Post. tenting angle (°)39 (34–46)
 IPMD (mm)26 (22–29)
 PMAD (mm)31 (27–34)
 LVEDVi (ml/BSA)122 (97–144)
 LVESVi (ml/BSA)84 (59–99)
 LVSVi (ml/BSA)42 (33–49)
 LVEF (%)36 (29–40)
 LVEDD (mm)65 (61–71)
 LVESD (mm)52 (46–61)

Data are median (IQR) or n (%).

BMI: body mass index; BSA: body surface area; FMR: functional mitral regurgitation; IPMD: interpapillary muscle distance; IQR: interquartile range; LVEDD/LVESD: left ventricular end-diastolic and end-systolic diameters; LVEDVi/LVESVi: left ventricular end-systolic and end-diastolic volume index; LVEF: left ventricular ejection fraction; LVSVi: left ventricular stroke volume index; MR: mitral regurgitation; NYHA: New York Heart Association; PMAD: papillary muscle to mitral annulus distance; TAPSE: tricuspid annular plane systolic excursion.

The ‘surgical cohort’ consisted of 23 patients who underwent MV surgery repair with papillary muscle repositioning and had a preoperative and postoperative cardiac MRI. The postoperative follow-up cardiac MR imaging was conducted 15 months (SD 8 month) after surgery. Characteristics of the surgical cohort are displayed in Table 2. The majority suffered from ischaemic MR (74%) and 39% received an additional coronary artery bypass graft. Only moderate annular reduction to a mean value of 30 mm (SD 3 mm) was sufficient to correct secondary MR, if papillary muscle repositioning manoeuvre was included. In contrast to this finding, more extensive annular reduction to 26 mm (SD 3 mm) was required in the isolated annuloplasty subgroup.

Table 2:
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Baseline characteristics in the surgical cohort with a simultaneous papillary muscle repositioning (n = 23) and in the isolated mitral valve annuloplasty patients (n = 12)

CharacteristicsSurgical cohort, n = 23Control group, n = 12
Age at time of operation (years)69 (57–72)65 (56–72)
Male, n (%)18 (78)6 (50)
BMI (kg/m2)27 (25–30)28 (24–30)
NYHA III–IV, n (%)18 (78)8 (67)
Ischaemic MR, n (%)17 (74)8 (67)
FMR due to dilated cardiomyopathy, n (%)6 (26)4 (33)
Associated procedures
 Additional CABG9 (39)5 (42)
 Left atrial appendage closure6 (26)4 (33)
 Atrial ablation2 (9)3 (25)
Postoperative complications
 Rethoracotomy3 (13)1 (8)
 Acute kidney failure2 (15)1 (8)
 Pacemaker implantation2 (15)1 (8)
 One-year mortality0 (0)0 (0)
CharacteristicsSurgical cohort, n = 23Control group, n = 12
Age at time of operation (years)69 (57–72)65 (56–72)
Male, n (%)18 (78)6 (50)
BMI (kg/m2)27 (25–30)28 (24–30)
NYHA III–IV, n (%)18 (78)8 (67)
Ischaemic MR, n (%)17 (74)8 (67)
FMR due to dilated cardiomyopathy, n (%)6 (26)4 (33)
Associated procedures
 Additional CABG9 (39)5 (42)
 Left atrial appendage closure6 (26)4 (33)
 Atrial ablation2 (9)3 (25)
Postoperative complications
 Rethoracotomy3 (13)1 (8)
 Acute kidney failure2 (15)1 (8)
 Pacemaker implantation2 (15)1 (8)
 One-year mortality0 (0)0 (0)

Data are median (IQR) or n (%).

BMI: body mass index; CABG: coronary artery bypass graft; FMR: functional mitral regurgitation; IQR: interquartile range; MR: mitral regurgitation; NYHA: New York Heart Association.

Table 2:
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Baseline characteristics in the surgical cohort with a simultaneous papillary muscle repositioning (n = 23) and in the isolated mitral valve annuloplasty patients (n = 12)

CharacteristicsSurgical cohort, n = 23Control group, n = 12
Age at time of operation (years)69 (57–72)65 (56–72)
Male, n (%)18 (78)6 (50)
BMI (kg/m2)27 (25–30)28 (24–30)
NYHA III–IV, n (%)18 (78)8 (67)
Ischaemic MR, n (%)17 (74)8 (67)
FMR due to dilated cardiomyopathy, n (%)6 (26)4 (33)
Associated procedures
 Additional CABG9 (39)5 (42)
 Left atrial appendage closure6 (26)4 (33)
 Atrial ablation2 (9)3 (25)
Postoperative complications
 Rethoracotomy3 (13)1 (8)
 Acute kidney failure2 (15)1 (8)
 Pacemaker implantation2 (15)1 (8)
 One-year mortality0 (0)0 (0)
CharacteristicsSurgical cohort, n = 23Control group, n = 12
Age at time of operation (years)69 (57–72)65 (56–72)
Male, n (%)18 (78)6 (50)
BMI (kg/m2)27 (25–30)28 (24–30)
NYHA III–IV, n (%)18 (78)8 (67)
Ischaemic MR, n (%)17 (74)8 (67)
FMR due to dilated cardiomyopathy, n (%)6 (26)4 (33)
Associated procedures
 Additional CABG9 (39)5 (42)
 Left atrial appendage closure6 (26)4 (33)
 Atrial ablation2 (9)3 (25)
Postoperative complications
 Rethoracotomy3 (13)1 (8)
 Acute kidney failure2 (15)1 (8)
 Pacemaker implantation2 (15)1 (8)
 One-year mortality0 (0)0 (0)

Data are median (IQR) or n (%).

BMI: body mass index; CABG: coronary artery bypass graft; FMR: functional mitral regurgitation; IQR: interquartile range; MR: mitral regurgitation; NYHA: New York Heart Association.

Twelve patients formed the ‘control group’, all of them had an isolated MV annuloplasty. Only 5 control group patients underwent postoperative MRI that was performed 13 months (SD 2 month) after surgery. The remaining 7 patients withdrew study participation (n = 5) or refused postoperative MRI due to claustrophobia (n = 2). Characteristics of the control patients are given in Table 2.

Measurement and establishment of papillary muscle to mitral annulus distance

Standard geometric LV measurements and functional MV parameters are displayed in Table 1. All parameters including PMAD measurements were very reproducible between 2 investigators as demonstrated by high inter-rater agreement values (0.825–0.937) (Table 3).

Table 3:
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Interobserver agreement and intraclass correlation coefficient

THADIPMDPMADATAPTA
Arithmetic mean−0.04130.1910.7051.000−1.6390.0163
Standard deviation2.2333.2472.9803.6385.8827.386
Lower limit−4.790−6.174−5.135−6.130−13.169−14.459
Upper limit3.9656.5556.5458.1309.88914.493
ICC (absolute)0.8460.9430.9510.8950.8050.814
95% confidence interval0.746–0.9070.906–0.9660.918–0.9700.825–0.9370.675–0.8830.690–0.888
THADIPMDPMADATAPTA
Arithmetic mean−0.04130.1910.7051.000−1.6390.0163
Standard deviation2.2333.2472.9803.6385.8827.386
Lower limit−4.790−6.174−5.135−6.130−13.169−14.459
Upper limit3.9656.5556.5458.1309.88914.493
ICC (absolute)0.8460.9430.9510.8950.8050.814
95% confidence interval0.746–0.9070.906–0.9660.918–0.9700.825–0.9370.675–0.8830.690–0.888

ICC for measuring LV geometric parameters reveals excellent agreement between the 2 observers indicating a high reproducibility.

AD: annular distance; ATA: anterior tenting angle; ICC: intraclass correlation coefficient; IPMD: interpapillary muscle distance; LV: left ventricular; PMAD: papillary muscle to mitral annulus distance; PTA: posterior tenting angle; TH: tenting height.

Table 3:
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Interobserver agreement and intraclass correlation coefficient

THADIPMDPMADATAPTA
Arithmetic mean−0.04130.1910.7051.000−1.6390.0163
Standard deviation2.2333.2472.9803.6385.8827.386
Lower limit−4.790−6.174−5.135−6.130−13.169−14.459
Upper limit3.9656.5556.5458.1309.88914.493
ICC (absolute)0.8460.9430.9510.8950.8050.814
95% confidence interval0.746–0.9070.906–0.9660.918–0.9700.825–0.9370.675–0.8830.690–0.888
THADIPMDPMADATAPTA
Arithmetic mean−0.04130.1910.7051.000−1.6390.0163
Standard deviation2.2333.2472.9803.6385.8827.386
Lower limit−4.790−6.174−5.135−6.130−13.169−14.459
Upper limit3.9656.5556.5458.1309.88914.493
ICC (absolute)0.8460.9430.9510.8950.8050.814
95% confidence interval0.746–0.9070.906–0.9660.918–0.9700.825–0.9370.675–0.8830.690–0.888

ICC for measuring LV geometric parameters reveals excellent agreement between the 2 observers indicating a high reproducibility.

AD: annular distance; ATA: anterior tenting angle; ICC: intraclass correlation coefficient; IPMD: interpapillary muscle distance; LV: left ventricular; PMAD: papillary muscle to mitral annulus distance; PTA: posterior tenting angle; TH: tenting height.

To establish PMAD, we focused on the correlation between papillary muscle distances (i.e. PMAD and IPMD) and global LV remodelling parameters, as expressed by an left ventricular end-systolic volume index, LVEDVi in the all patients. The overall model showed a correlation between both IPMD and PMAD versus left ventricular end-systolic volume index (rs = 0.488, P = 0.001 and rs = 0.447, P = 0.001). A similar relationship was found between IPMD/PMAD versus LVEDVi (rs = 0.487, P = 0.001 and rs = 0.291, P = 0.033), while the correlation was weaker for PMAD (Table 4).

Table 4:
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Correlation analysis between left ventricular end-systolic and end-diastolic volume versus intrapapillary muscle distance and papillary muscle to mitral annulus distance in all 63 functional mitral regurgitation patients preoperatively

LVESVLVEDVTATH
IPMD
 Spearman‘s rho correlation coefficient (rs)0.4880.4870.1490.175
 P-Value0.0010.0010.2560.180
PMAD
 Spearman‘s rho correlation coefficient (rs)0.4470.2910.3380.272
 P-Value0.0010.0330.0090.035
LVESVLVEDVTATH
IPMD
 Spearman‘s rho correlation coefficient (rs)0.4880.4870.1490.175
 P-Value0.0010.0010.2560.180
PMAD
 Spearman‘s rho correlation coefficient (rs)0.4470.2910.3380.272
 P-Value0.0010.0330.0090.035

Both parameters, IPMD and PMAD, correlate significantly with the global LV remodelling parameters, LVESV and LVEDV. Correlation analysis between mitral valve tenting parameters (TH and TA) versus IPMD and PMAD in the whole collective. Significant correlation was found between mitral valve tenting parameters and PMAD, highlighting the association between apical papillary muscle displacement and the severity of tenting. No significant correlation was found between IPMD and mitral valve tenting parameters.

AD: annular distance; IPMD: interpapillary muscle distance; LVEDV: left ventricular end-diastolic volume; LVESV: left ventricular end-systolic volume; PMAD: papillary muscle to mitral annulus distance; TH: tenting height.

Table 4:
Open in new tab

Correlation analysis between left ventricular end-systolic and end-diastolic volume versus intrapapillary muscle distance and papillary muscle to mitral annulus distance in all 63 functional mitral regurgitation patients preoperatively

LVESVLVEDVTATH
IPMD
 Spearman‘s rho correlation coefficient (rs)0.4880.4870.1490.175
 P-Value0.0010.0010.2560.180
PMAD
 Spearman‘s rho correlation coefficient (rs)0.4470.2910.3380.272
 P-Value0.0010.0330.0090.035
LVESVLVEDVTATH
IPMD
 Spearman‘s rho correlation coefficient (rs)0.4880.4870.1490.175
 P-Value0.0010.0010.2560.180
PMAD
 Spearman‘s rho correlation coefficient (rs)0.4470.2910.3380.272
 P-Value0.0010.0330.0090.035

Both parameters, IPMD and PMAD, correlate significantly with the global LV remodelling parameters, LVESV and LVEDV. Correlation analysis between mitral valve tenting parameters (TH and TA) versus IPMD and PMAD in the whole collective. Significant correlation was found between mitral valve tenting parameters and PMAD, highlighting the association between apical papillary muscle displacement and the severity of tenting. No significant correlation was found between IPMD and mitral valve tenting parameters.

AD: annular distance; IPMD: interpapillary muscle distance; LVEDV: left ventricular end-diastolic volume; LVESV: left ventricular end-systolic volume; PMAD: papillary muscle to mitral annulus distance; TH: tenting height.

Furthermore, we aimed to demonstrate the correlation between papillary muscle distances and MV tenting parameters. However, there was no significant correlation between IPMD and severity of MV tenting (tenting area: rs = 0.149, P = 0.256; tenting height: rs = 0.175, P = 0.180). As opposed to that, PMAD correlated significantly with the MV tenting parameters (tenting area: rs = 0.338, P = 0.009; tenting height: rs = 0.272, P = 0.035) (Table 4).

Effect of subannular repair on papillary muscle to mitral annulus distance

Papillary muscle repositioning in the surgical cohort resulted in significantly decreased PMAD values [30 mm (IQR 27–34) preoperatively vs 25 mm (IQR 21–27) postoperatively] (P = 0.001) (Fig. 2). Furthermore, there was a simultaneous reduction of IPMD after papillary muscle repositioning procedure [27 mm (IQR 23–32) preoperatively vs 22 mm (IQR 18–26) postoperatively] (P = 0.038). In the control group undergoing an isolated MV annuloplasty, there was no significant change in the postoperative PMAD and IPMD, as compared to preoperative values (Table 5). Using an alpha error probability of 0.05, post hoc power analysis for PMAD revealed an actual power of 0.953.

Postoperative changes in the intrapapillary muscle distance and papillary muscle to mitral annulus distance in the study group (n = 23). Postoperatively, regional papillary muscle geometry was better restored with a significant reduction of both parameters, intrapapillary muscle distance and papillary muscle to mitral annulus distance.
Figure 2:

Postoperative changes in the intrapapillary muscle distance and papillary muscle to mitral annulus distance in the study group (n = 23). Postoperatively, regional papillary muscle geometry was better restored with a significant reduction of both parameters, intrapapillary muscle distance and papillary muscle to mitral annulus distance.

Open in new tabDownload slide

Video 1:

This intraoperative video shows the main steps of minimally invasive mitral valve repair with subannular procedure in a 59-year-old female patient with type IIIb functional mitral regurgitation. The patient suffered from severe functional mitral regurgitation (Carpentier IIIb) due to ischaemic cardiomyopathy after posterolateral NSTEMI with now moderately impaired left ventricular function. No regurgitation could be detected in the postoperative echocardiogram.

Table 5:
Open in new tab

Development of left ventricular parameters preoperatively and 1 year after mitral valve annuloplasty with simultaneous papillary muscle repositioning as compared to an isolated annuloplasty control group, measured by cardiac magnetic resonance imaging (MRI) and echocardiography

Surgical cohort
Control group
PreoperativelyOne year after surgeryP-ValuePreoperativelyOne year after surgeryP-Value
Cardiac MRI parameters
 Tenting height (mm)12 (11–13)9 (8–11)0.02312 (8–14)10 (9–12)0.684
 Annular diameter (mm)37 (36–41)30 (28–33)0.00136 (33–39)26 (25–32)0.068
 Tenting area (mm2)213 (184–267)136 (115–176)0.001224 (158–239)187 (115–171)0.068
 Ant. tenting angle (°)28 (26–32)32 (27–37)0.50632 (29–37)36 (28–42)0.456
 Post. tenting angle (°)38 (32–42)34 (26–38)0.07548 (36–55)39 (24–43)0.273
 IMPD (mm)27 (23–32)22 (18–26)0.03822 (17–27)21 (15–24)0.500
 PMAD (mm)30 (27–34)25 (21–27)0.00126 (24–28)25 (23–28)0.465
 LVEDVi (ml/BSA)131 (109–149)123 (83–145)0.08796 (82–138)93 (90–155)0.593
 LVESVi (ml/BSA)95 (60–100)81 (39–100)0.13344 (31–89)47 (37–110)0.593
 LVSVi (ml/BSA)43 (33–52)42 (35–47)0.21351 (45–55)50 (40–54)0.109
 LVEF (%)35 (29–44)33 (30–52)0.87547 (36–61)49 (31–59)0.593
 LVEDD (mm)66 (60–71)58 (53–67)0.00162 (61–67)60 (53–67)0.462
 LVESD (mm)52 (48–61)49 (40–58)0.00248 (44–62)44 (35–54)0.343
Echocardiographic parameters
 LVEF (%)36 (31–30)39 (32–43)0.46746 (34–62)45 (34–55)0.534
 LVEDD (mm)65 (56–70)58 (55–61)0.04859 (51–60)55 (56–59)0.838
 TAPSE (mm)19 (18–21)17 (16–19)0.08318 (17–20)16 (16–18)0.051
 sPAP (mmHg)55 (41–63)43 (34–52)0.03052 (49–60)46 (44–50)0.184
 Mitral regurgitation, n (%)0.001
  None (grade 0)0 (0)12 (52)0 (0)0 (00)
  Mild (grade 1)0 (0)11 (48)0 (0)4 (80)
  Moderate (grade 2)7 (30)0 (0)3 (60)1 (20)
  Severe (grade 3)16 (70)0 (0)2 (40)0 (0)
Surgical cohort
Control group
PreoperativelyOne year after surgeryP-ValuePreoperativelyOne year after surgeryP-Value
Cardiac MRI parameters
 Tenting height (mm)12 (11–13)9 (8–11)0.02312 (8–14)10 (9–12)0.684
 Annular diameter (mm)37 (36–41)30 (28–33)0.00136 (33–39)26 (25–32)0.068
 Tenting area (mm2)213 (184–267)136 (115–176)0.001224 (158–239)187 (115–171)0.068
 Ant. tenting angle (°)28 (26–32)32 (27–37)0.50632 (29–37)36 (28–42)0.456
 Post. tenting angle (°)38 (32–42)34 (26–38)0.07548 (36–55)39 (24–43)0.273
 IMPD (mm)27 (23–32)22 (18–26)0.03822 (17–27)21 (15–24)0.500
 PMAD (mm)30 (27–34)25 (21–27)0.00126 (24–28)25 (23–28)0.465
 LVEDVi (ml/BSA)131 (109–149)123 (83–145)0.08796 (82–138)93 (90–155)0.593
 LVESVi (ml/BSA)95 (60–100)81 (39–100)0.13344 (31–89)47 (37–110)0.593
 LVSVi (ml/BSA)43 (33–52)42 (35–47)0.21351 (45–55)50 (40–54)0.109
 LVEF (%)35 (29–44)33 (30–52)0.87547 (36–61)49 (31–59)0.593
 LVEDD (mm)66 (60–71)58 (53–67)0.00162 (61–67)60 (53–67)0.462
 LVESD (mm)52 (48–61)49 (40–58)0.00248 (44–62)44 (35–54)0.343
Echocardiographic parameters
 LVEF (%)36 (31–30)39 (32–43)0.46746 (34–62)45 (34–55)0.534
 LVEDD (mm)65 (56–70)58 (55–61)0.04859 (51–60)55 (56–59)0.838
 TAPSE (mm)19 (18–21)17 (16–19)0.08318 (17–20)16 (16–18)0.051
 sPAP (mmHg)55 (41–63)43 (34–52)0.03052 (49–60)46 (44–50)0.184
 Mitral regurgitation, n (%)0.001
  None (grade 0)0 (0)12 (52)0 (0)0 (00)
  Mild (grade 1)0 (0)11 (48)0 (0)4 (80)
  Moderate (grade 2)7 (30)0 (0)3 (60)1 (20)
  Severe (grade 3)16 (70)0 (0)2 (40)0 (0)

Data are median (IQR). P-values for the surgical cohort were calculated using a Wilcoxon signed-rank test. Significant differences are indicated in bold.

BSA: body surface area; IPMD: interpapillary muscle distance; IQR: interquartile range; LVEDD/LVESD: left ventricular end-diastolic and end-systolic diameters; LVEDVi/LVESVi: left ventricular end-diastolic and end-systolic volume index; LVEF: left ventricular ejection fraction; LVSVi: left ventricular stroke volume index; PMAD: papillary muscle to mitral annulus distance; sPAP: systolic pulmonary artery pressure; TAPSE: tricuspid annular plane systolic excursion.

Table 5:
Open in new tab

Development of left ventricular parameters preoperatively and 1 year after mitral valve annuloplasty with simultaneous papillary muscle repositioning as compared to an isolated annuloplasty control group, measured by cardiac magnetic resonance imaging (MRI) and echocardiography

Surgical cohort
Control group
PreoperativelyOne year after surgeryP-ValuePreoperativelyOne year after surgeryP-Value
Cardiac MRI parameters
 Tenting height (mm)12 (11–13)9 (8–11)0.02312 (8–14)10 (9–12)0.684
 Annular diameter (mm)37 (36–41)30 (28–33)0.00136 (33–39)26 (25–32)0.068
 Tenting area (mm2)213 (184–267)136 (115–176)0.001224 (158–239)187 (115–171)0.068
 Ant. tenting angle (°)28 (26–32)32 (27–37)0.50632 (29–37)36 (28–42)0.456
 Post. tenting angle (°)38 (32–42)34 (26–38)0.07548 (36–55)39 (24–43)0.273
 IMPD (mm)27 (23–32)22 (18–26)0.03822 (17–27)21 (15–24)0.500
 PMAD (mm)30 (27–34)25 (21–27)0.00126 (24–28)25 (23–28)0.465
 LVEDVi (ml/BSA)131 (109–149)123 (83–145)0.08796 (82–138)93 (90–155)0.593
 LVESVi (ml/BSA)95 (60–100)81 (39–100)0.13344 (31–89)47 (37–110)0.593
 LVSVi (ml/BSA)43 (33–52)42 (35–47)0.21351 (45–55)50 (40–54)0.109
 LVEF (%)35 (29–44)33 (30–52)0.87547 (36–61)49 (31–59)0.593
 LVEDD (mm)66 (60–71)58 (53–67)0.00162 (61–67)60 (53–67)0.462
 LVESD (mm)52 (48–61)49 (40–58)0.00248 (44–62)44 (35–54)0.343
Echocardiographic parameters
 LVEF (%)36 (31–30)39 (32–43)0.46746 (34–62)45 (34–55)0.534
 LVEDD (mm)65 (56–70)58 (55–61)0.04859 (51–60)55 (56–59)0.838
 TAPSE (mm)19 (18–21)17 (16–19)0.08318 (17–20)16 (16–18)0.051
 sPAP (mmHg)55 (41–63)43 (34–52)0.03052 (49–60)46 (44–50)0.184
 Mitral regurgitation, n (%)0.001
  None (grade 0)0 (0)12 (52)0 (0)0 (00)
  Mild (grade 1)0 (0)11 (48)0 (0)4 (80)
  Moderate (grade 2)7 (30)0 (0)3 (60)1 (20)
  Severe (grade 3)16 (70)0 (0)2 (40)0 (0)
Surgical cohort
Control group
PreoperativelyOne year after surgeryP-ValuePreoperativelyOne year after surgeryP-Value
Cardiac MRI parameters
 Tenting height (mm)12 (11–13)9 (8–11)0.02312 (8–14)10 (9–12)0.684
 Annular diameter (mm)37 (36–41)30 (28–33)0.00136 (33–39)26 (25–32)0.068
 Tenting area (mm2)213 (184–267)136 (115–176)0.001224 (158–239)187 (115–171)0.068
 Ant. tenting angle (°)28 (26–32)32 (27–37)0.50632 (29–37)36 (28–42)0.456
 Post. tenting angle (°)38 (32–42)34 (26–38)0.07548 (36–55)39 (24–43)0.273
 IMPD (mm)27 (23–32)22 (18–26)0.03822 (17–27)21 (15–24)0.500
 PMAD (mm)30 (27–34)25 (21–27)0.00126 (24–28)25 (23–28)0.465
 LVEDVi (ml/BSA)131 (109–149)123 (83–145)0.08796 (82–138)93 (90–155)0.593
 LVESVi (ml/BSA)95 (60–100)81 (39–100)0.13344 (31–89)47 (37–110)0.593
 LVSVi (ml/BSA)43 (33–52)42 (35–47)0.21351 (45–55)50 (40–54)0.109
 LVEF (%)35 (29–44)33 (30–52)0.87547 (36–61)49 (31–59)0.593
 LVEDD (mm)66 (60–71)58 (53–67)0.00162 (61–67)60 (53–67)0.462
 LVESD (mm)52 (48–61)49 (40–58)0.00248 (44–62)44 (35–54)0.343
Echocardiographic parameters
 LVEF (%)36 (31–30)39 (32–43)0.46746 (34–62)45 (34–55)0.534
 LVEDD (mm)65 (56–70)58 (55–61)0.04859 (51–60)55 (56–59)0.838
 TAPSE (mm)19 (18–21)17 (16–19)0.08318 (17–20)16 (16–18)0.051
 sPAP (mmHg)55 (41–63)43 (34–52)0.03052 (49–60)46 (44–50)0.184
 Mitral regurgitation, n (%)0.001
  None (grade 0)0 (0)12 (52)0 (0)0 (00)
  Mild (grade 1)0 (0)11 (48)0 (0)4 (80)
  Moderate (grade 2)7 (30)0 (0)3 (60)1 (20)
  Severe (grade 3)16 (70)0 (0)2 (40)0 (0)

Data are median (IQR). P-values for the surgical cohort were calculated using a Wilcoxon signed-rank test. Significant differences are indicated in bold.

BSA: body surface area; IPMD: interpapillary muscle distance; IQR: interquartile range; LVEDD/LVESD: left ventricular end-diastolic and end-systolic diameters; LVEDVi/LVESVi: left ventricular end-diastolic and end-systolic volume index; LVEF: left ventricular ejection fraction; LVSVi: left ventricular stroke volume index; PMAD: papillary muscle to mitral annulus distance; sPAP: systolic pulmonary artery pressure; TAPSE: tricuspid annular plane systolic excursion.

In line with the reduction of PMAD, there was a significant reduction of MV tenting severity after subannular MV repair (median tenting height of 12 mm preoperatively vs 9 mm postoperatively, P = 0.023). There was also a significant reduction of the MV tenting area [213 mm2 (IQR 184–267) preoperatively vs 136 mm2 (IQR 115–176) postoperatively] (P < 0.001). No significant changes in the MV tenting parameters were observed in the control group patients after an isolated MV annuloplasty (Table 5).

Global left ventricular reverse remodelling in the surgical cohort

Both LVEDD and LVESD showed a statistically significant decrease in the surgical cohort postoperatively [median LVEDD 66 mm (IQR 60–71 mm) preoperatively vs 58 mm (IQR 53–67 mm) postoperatively, P = 0.001 and median LVESD of 52 mm (IQR 48–61 mm) preoperatively vs 49 mm (IQR 40–58 mm) postoperatively, P = 0.002] (Table 5). No statistical significance was found for the postoperative reduction of indexed diastolic LV volume [median LVEDVi 131 ml (IQR 100–149) preoperatively vs 123 ml (IQR 93–145) postoperatively, P = 0.083] (Table 5). Systolic LV function remained unchanged preoperatively versus postoperatively. No significant changes in the systolic/diastolic LV volumes or diameters were postoperatively found in the control group.

DISCUSSION

Main finding

Our study reveals that MV annuloplasty with a simultaneous papillary muscle repositioning result in a reduced PMAD 1 year after subannular MV repair. This decreased PMAD translated into significantly reduced MV tenting and showed a tendency towards global LV reverse remodelling.

Papillary muscle to mitral annulus distance—a novel marker of apical papillary muscle displacement

Progressive LV remodelling in systolic heart failure is accompanied by apico-lateral papillary muscle displacement [1, 2]. In consequence of altered papillary muscle geometry, an increased tension on MV leaflets through the subannular structures occurs that causes restrictive movement of MV leaflets during the systole (i.e. tenting) and resultant FMR. Papillary muscle repositioning procedure aims to correct apical papillary muscle displacement in the eccentrically remodelled LV. Favourable clinical effects of papillary muscle repositioning procedure when improving MV competence after MV repair has been previously demonstrated (i.e. reduced MR reoccurrence, decreased residual leaflet tenting and improved 1-year outcome) [7]. However, the direct evidence of improved papillary muscle geometry following subannular repair, as demonstrated by sophisticated imaging study, is still lacking. In our current study, we used cardiac MRI to quantify apical papillary muscle displacement by measuring a new parameter- PMAD which describes the distance between papillary muscle tips and MV annulus plane (Fig. 1). For this purpose, we used the unique possibility of the MRI to cross-reference different axes with each other and could thus determine the distance as accurately as possible. The interobserver variability of PMAD measurements was tested and showed excellent reproducibility values. The technique of cross-referencing can only be performed on MR images and, therefore, this new parameter cannot be assessed with standard transthoracic or transoesophageal echocardiography.

Clinical establishment of papillary muscle to mitral annulus distance

Since PMAD is meant to be a quantitative indicator of apical papillary muscle displacement in the remodelled LV, it should ideally correlate with global LV remodelling parameters. Therefore, in the second step of our study, we correlated PMAD with the global LV size parameters as well as with MV tenting severity in the whole study cohort. Additionally, a well-known indicator of the lateral papillary muscle displacement—IPMD—was used as a control. We found that PMAD and IPMD correlated significantly and linearly with global LV size parameters (Table 4). On the other hand, MV tenting parameters (i.e. tenting height and tenting area) correlated significantly with PMAD only, while there was no significant association with IPMD (Table 4). PMAD correlated significantly with LV size parameters as well as with MV tenting severity, while IPMD correlated significantly with LV size parameters only, but not with MV tenting severity. The correlation of PMAD and MV tenting parameters was rather weak, which we ascribe to the small number of cases and to the fact that tenting is not solely dependent on PMAD but, rather, multifactorial dependent on the overall ventricular geometry. Given that fact, PMAD seems to better reflect geometric MV distortion and MV tenting severity, as compared to IPMD. This observation supports our clinical assumption that geometric MV distortion in FMR type IIIb occurs predominantly due to apical papillary muscle displacement. This finding provides the clinical background for favouring papillary muscle repositioning techniques in FMR surgery instead of papillary muscle re-approximation [13], which addresses lateral papillary muscle displacement only.

Effect of subannular repair on papillary muscle to mitral annulus distance

In the next step of our study, we compared PMAD measurements before and after subannular repair in a surgical cohort of 23 FMR patients who underwent papillary muscle repositioning procedure.

We were able to demonstrate that papillary muscle relocation procedure effectively decreased PMAD values 1 year after surgery, by reducing mean PMAD by a median of −5.6 mm as compared to preoperative distance indicating a stable reduction of apical papillary muscle displacement. This is reinforced by a fairly high statistical power of 0.953, indicating a good chance of achieving significance if the study is repeated and adding credibility to our results. In addition, IPMD was postoperatively significantly reduced by a median of −5.0 mm, which can be explained by a more medial exteriorization of polytetrafluorethylene repositioning sutures as compared to the preoperative position of both papillary muscle groups. As opposed to these findings in the subannular repair group, there was no significant effect of an isolated ring annuloplasty on PMAD and IPMD in the control group.

This postoperative decrease of PMAD and IPMD after papillary muscles repositioning procedure indicates an improved regional LV architecture in patients with an eccentric LV remodelling.

Global left ventricular reverse remodelling after subannular repair

Despite the advantageous effect of papillary muscle repositioning on the papillary muscle geometry, the question remains whether this decline in PMAD translates into a global LV reverse remodelling due to improved MV competency. For this purpose, we further analysed the surgical cohort. First, we found a significant reduction of MV tenting severity, expressed as MV tenting height and tenting area in the surgical cohort.

Our thesis is supported by the fact that global LV size parameters (i.e. LVEDD and LVESD) decreased significantly postoperatively, implying a sustainable change in global LV architecture.

Interpretation in the context of the literature

Cardiac MRI is a robust method to assess detailed LV geometry with a higher reproducibility, as compared to echocardiography [14]. This is in line with our results on interobserver reliability, which revealed an excellent agreement between the 2 observers. Especially the novel parameter PMAD showed an excellent interobserver reliability (Table 3). This accuracy of measurements in cardiac MRI gives an opportunity to detect modest changes in the LV architecture and provides reproducible imaging biomarkers to quantify LV disease.

PMAD parameter has not been analysed previously, therefore, a reasonable comparison with other studies on subannular repair in type IIIb FMR are difficult. However, several previous studies analysed postoperative changes in IPMD, which predominantly describe lateral papillary muscle displacement, after papillary muscle manoeuvres [13]. In the randomized study by Nappi and co-authors IPMD was significantly reduced after papillary muscle approximation procedure from 40.5 mm (SD 4.6 mm) at baseline to 31.1 mm (SD 2.6 mm) at 1 year postoperatively (P < 0.001) [13]. Similar to these findings, another retrospective study by Mihos et al. [15] documented a significant reduction of IPMD from 29 mm (SD 7 mm) preoperatively to 14 mm (SD 4 mm) postoperatively following papillary muscle sling manoeuvre.

Limitations

Major limitation of our study is a limited sample size of FMR type IIIb both patient groups who underwent surgery, the surgical cohort and the control group. Furthermore, the postoperative follow-up duration of the surgical cohort with 15 months (SD 8 months) is still limited to define the long-term effects of papillary muscle repositioning procedure. Therefore, our results should be validated in a larger prospective cohort with a longer postoperative follow-up.

Another limitation is that only some patients received additional CABG. Myocardial revascularization alone might also lead to reverse LV remodelling. Unfortunately, the result cannot be subdivided and the collective is too small for a multivariate analysis. Therefore, the isolated impact of MV repair with papillary muscle repositioning on reverse LV remodelling remains unclear.

CONCLUSION

Our study demonstrates that papillary muscle repositioning procedure results in a reduced papillary muscle-to-annulus distance (PMAD) in cardiac MRI following subannular MV repair. This change of papillary muscle geometry is associated with an improved MV geometry (i.e. reduced MV tenting severity) and, therefore, has the potential to improve the durability and functional outcome of MV repair and thereby to potentiate global LV reverse remodelling.

Conflict of interest: none declared.

Data Availability Statement

The data underlying this article will be shared on reasonable request to the corresponding author.

Author contributions

Martin Sinn: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Resources; Software; Validation; Visualization; Writing—original draft; Writing—review & editing. Jonas Pausch: Data curation; Formal analysis; Methodology; Writing—review & editing. Haissam Ragab: Data curation; Formal analysis; Software; Writing—review & editing. Tatiana Sequeira-Gross: Conceptualization; Writing—review & editing. Maria von Stumm: Conceptualization; Writing—review & editing. Clemens Spink: Validation; Writing—review & editing. Gerhard Adam: Supervision; Writing—review & editing. Hermann Reichenspurner: Supervision; Writing—review & editing. Peter Bannas: Supervision; Validation; Visualization; Writing—review & editing. Gunnar Lund: Conceptualization; Project administration; Supervision; Writing—review& editing. Evaldas Girdauskas: Conceptualization; Project administration; Supervision; Writing—original draft; Writing—review & editing.

Reviewer information

European Journal of Cardio-Thoracic Surgery thanks Anton Tomsic, Thierry Bove and the other, anonymous reviewer(s) for their contribution to the peer review process of this article.

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ABBREVIATIONS

    ABBREVIATIONS
     
  • FMR

    Functional mitral regurgitation

    •  
  • IPMD

    Interpapillary muscle distance

    •  
  • IQR

    Interquartile range

    •  
  • LV

    Left ventricular

    •  
  • LVEDD

    Left ventricular end-diastolic diameter

    •  
  • LVEDVi

    Left ventricular end-diastolic volume index

    •  
  • LVESD

    Left ventricular end-systolic diameter

    •  
  • MR

    Mitral regurgitation

    •  
  • MV

    Mitral valve

    •  
  • PMAD

    Papillary muscle to mitral annulus distance

    •  
  • SD

    Standard deviation

© The Author(s) 2022. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://dbpia.nl.go.kr/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Topic:
Subject
Organ Protection (Acquired Cardiac) Valve Disorders (Acquired Cardiac)
Issue Section:
CONVENTIONAL VALVE OPERATIONS
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