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Abstract

OBJECTIVES

Echocardiographic right ventricular (RV) annular parameters are probably not as reliable to evaluate the surgical success in the postoperative period after pulmonary endarterectomy (PEA), whereas RV end-diastolic/left ventricular end-diastolic area ratio (RVEDA/LVEDA ratio) could be more useful. This study examined the relationship between RV annular parameters or RVEDA/LVEDA ratio and ideal cardiac index (ICI), before and after PEA.

METHODS

Among 80 patients who underwent PEA, the relationships between RVEDA/LVEDA ratio (21 patients), or tricuspid annular plane systolic excursion (32 patients), or systolic tricuspid annular velocity (55 patients) and ICI were modelled.

RESULTS

Forty-eight hours following PEA, mean pulmonary artery pressure decreased (26 ± 6 vs 46 ± 12 mmHg, P < 0.0001) and ICI improved (2.8 ± 0.8 vs 3.0 ± 0.9 l/min/m2, P = 0.02). In contrast to the moderate association between RV annular indices and ICI in the preoperative period, no significant relationship was found in the postoperative period (r = 0.54 and 0.17 for tricuspid annular plane systolic excursion and r = 0.46 and 0.16 for systolic tricuspid annular velocity, respectively). The RVEDA/LVEDA ratio significantly decreased postoperatively (0.97 ± 0.21 vs 1.19 ± 0.43, P = 0.002) and was correlated with ICI both in preoperative and postoperative periods (r = 0.57 and 0.57, respectively). There was a significant correlation between changes in RVEDA/LVEDA ratio and changes in total pulmonary resistance

CONCLUSIONS

Improved ICI and RVEDA/LVEDA ratio reflected the surgical success of PEA and lowering of total pulmonary resistances. In contrast to the RV/left ventricular area ratio, annular RV indices associated poorly with postoperative ICI. Recognizing this limitation is important in minimizing the overdiagnosis of RV dysfunction after PEA.

Chronic thromboembolic pulmonary hypertension, Echocardiography, Annular right ventricular function indices, Right ventricular dimension, Right heart catheterization, Pulmonary endarterectomy

INTRODUCTION

Pulmonary endarterectomy (PEA) has transformed the outcomes of patients with chronic thromboembolic pulmonary hypertension (CTEPH) [1]. Patients who undergo PEA have a variable degree of right ventricular (RV) dysfunction. Postoperatively, RV failure is associated with poor outcome in the intensive care unit (ICU).

Among different annular parameters, tricuspid annular plane systolic excursion (TAPSE) and systolic tricuspid annular velocity (S’ velocity) are the most well-studied [2–4]. In patients with CTEPH, TAPSE and S’ velocity correlated well with pulmonary vascular resistances (PVR), mean pulmonary artery pressure (PAP) and cardiac output (CO) [5–7]. Moreover, TAPSE is correlated with RV area change [8, 9] and is a predictor of severe RV dysfunction in patients with pulmonary arterial hypertension [8]. RV size [evaluated by RV diameter and/or RV/left ventricular (LV) area ratio] is a reliable marker of RV dilation [4, 10] and is a factor of poor prognosis in patients with idiopathic pulmonary arterial hypertension [9]. RV/LV area ratio exhibited a correlation with CO in patients with acute respiratory distress syndrome [11] and was related to the severity of circulatory failure in patients with pulmonary embolism [12].

Several studies have shown that annular parameters decreased following cardiac surgery [3, 13, 14]. This reduction of annular parameters does not represent a decrease in RV function [15] and is not reliable in evaluating RV function following cardiac surgery [3]. Few studies to date have attributed RV annular parameters to PVR or RV ejection fraction before and after PEA [5, 16]. After PEA, the size of the RV decreases [17–19], but a relationship with CO or PVR is rarely reported [18].

The primary objective of this study was to assess the relationship between RV annular parameters and RV dimensions and CO before and during the first 3 days after PEA.

PATIENTS AND METHODS

Study design and patients

This retrospective study was approved by our Institutional Review Board (CER:2016-10). From 1 January 2015 to 31 December 2015, 125 patients underwent PEA, representing the total number of this procedure performed nationally. Surgical criteria include the severity of the patient symptoms, the severity of CTEPH, right heart dysfunction and surgical accessibility of the thrombi [1]. All patients underwent PEA as previously described [20]. Four experienced surgeons performed all procedures. Patients aged ≥18 years were eligible for inclusion in the present study if they were monitored with a pulmonary artery catheter (PAC). Exclusion criteria comprised the need for extracorporeal membrane and the absence of recorded postoperative echocardiographic data. Patients were divided into 2 groups based on whether CTEPH was severe or not, as defined by preoperative total pulmonary vascular resistance (TPR) >900 and ≤900 dynes·s/cm5, respectively [20].

Haemodynamic measurements obtained by a pulmonary artery catheter

As per institutional protocol, all patients scheduled for PEA were monitored using a PAC (Swan-Ganz CCOmbo CCO/SvO2, Edwards Lifescience, Irvine, CA, USA), which was inserted and connected to an integrated bedside monitor (Vigilance II monitor, Edwards Lifescience) for continuous monitoring of CO and mixed venous oxygen saturation. PAP and right atrial pressure were measured at end-expiration. Because a reliable capillary pressure is not always obtained in patients with severe pulmonary artery pressure (PAH), TPR was calculated as the ratio of mean PAP over CO and expressed in dynes·s/cm5 CO indexed to ideal body surface area (based on ideal weight) defined ideal cardiac index (ICI) [21]. The ideal weight was obtained by the Lorentz’s formula.

Echocardiography

Two-dimensional, colour flow and Doppler transthoracic echocardiography was performed using GE Vivid 7 (GE Healthcare, Vélizy Villacoublay, France) between the first and third postoperative day by certified echocardiographists. Although most preoperative echocardiographies were performed in our hospital (69%), some were performed in other hospitals. Preoperative echocardiographic data were kept arbitrarily, only when echocardiography was performed during the 3 preceding weeks of PAC results. Data were collected from reports of echocardiographic studies and images were not available for re-analysis.

The following echocardiographic parameters were recorded [2, 4, 10]:

  • Right ventricular end-diastolic area (RVEDA)/left ventricular end-diastolic area (LVEDA) ratio (RVEDA/LVEDA ratio), measured in end-diastole by tracing the areas of the 2 chambers in the apical four-chamber view. Moderate RV enlargement was defined by a ratio of >0.6 and severe RV enlargement by a ratio >1.0 [10].

  • TAPSE measured using M-mode on the apical four-chamber view. A TAPSE <17 mm was highly suggestive of RV systolic dysfunction [4].

  • S’ velocity measured using Tissue Doppler Imaging on the lateral tricuspid annulus; values <9.5 cm/s indicate RV systolic dysfunction [4].

  • LV ejection fraction was evaluated using the biplane modified Simpson method of discs.

Due to poor image quality or the occasional absence of a sonographer on weekends, the number of echocardiography parameters recorded varied with time. Evaluation of tricuspid regurgitation was not done.

Data collection

For each patient, we recorded age, sex, weight, body mass index, preoperative therapy for pulmonary arterial hypertension, cardiopulmonary bypass and cardiac arrest durations, Simplified Acute Physiology Score II, preoperative serum brain natriuretic peptide level, total lung capacity, duration of mechanical ventilation, length of stay in the ICU and mortality in the ICU.

Haemodynamic parameters obtained by PAC were recorded after PEA (day 1), and on the next 2 days (day 2 and 3). We selected the values recorded simultaneously to the echocardiography assessment.

Statistical analysis

Data were analysed using StatView 5.0 software (SAS Institute Inc., Cary, NC, USA). The Kolmogorov–Smirnov test was used to assess normality of data distribution. Baseline categorical variables were presented as number (%) and quantitative variables as mean ± standard deviation if normally distributed or median (interquartile range) otherwise. χ2 tests or Fisher’s exact test were applied to compare proportions and rates, and t-test or Mann–Whitney U-test were used to compare continuous variables. P-values <0.05 were considered statistically significant. Changes in haemodynamic parameters after PEA within the 2 groups were analysed using repeated-measures analysis of variance followed by the Scheffe F test. The relationship between RV size, TAPSE or S’ velocity and ICI or TPR were studied using linear regression equation. Comparison of correlation coefficients before and after PEA was performed using the Z-score.

RESULTS

One hundred twenty-five patients were retrospectively screened, among whom 80 were included (Fig. 1); 13 patients were excluded as they required extracorporeal membrane oxygenation assistance in the immediate postoperative period, no reliable haemodynamic data and no echocardiographic data were available for 11 and 21 patients, respectively. Table 1 reports the patient characteristics according to the severity of CTEPH.

Flow chart of the study population. ECMO: extracorporeal membrane oxygenation.
Figure 1:

Flow chart of the study population. ECMO: extracorporeal membrane oxygenation.

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Table 1:
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Preoperative characteristics of the study population according to the pulmonary disease severity

Total cohort (n = 80)Patients with TPR ≤ 900 dynes·s/cm5 (n = 46)Patients with TPR > 900 dynes·s/cm5 (n = 34)P-value
Age (years), mean ± SD57 ± 1657 ± 1661 ± 140.23
Male gender, n (%)30 (37)22 (48)8 (23)0.03
BMI (kg/m2), mean ± SD27.9 ± 7.029.6 ± 7.625.7 ± 5.30.01
BMI >30 kg/m2, n (%)22 (27)15 (33)7 (20)0.23
Body surface area (m2), mean ± SD1.90 ± 0.291.99 ± 0.311.78 ± 1.19<0.001
Ideal body surface area (m2), mean ± SD1.68 ± 0.181.71 ± 0.191.64 ± 0.150.11
Preoperative PaO2 (mmHg), mean ± SD65 ± 1266 ± 1364 ± 90.53
Total lung capacity (%), mean ± SD91 ± 1594 ± 1587 ± 130.07
Forced vital capacity (%), mean ± SD91 ± 2092 ± 2188 ± 180.33
FEV1 (%), mean ± SD87 ± 1988 ± 2084 ± 170.42
BNP (ng/l), median (IQR)80 (26–252)38 (20–111)192 (89–501)<0.001
PH-specific treatments, n (%)
 Epoprostenol1 (1)01 (3)0.24
 Bosentan25 (31)18 (39)7 (20)0.08
 Sildenafil18 (22)8 (17)10 (29)0.20
Need of dobutamine, n (%)9 (11)1 (2)8 (23)0.003
Duration of cardiopulmonary bypass (min), mean ± SD227 ± 34230 ± 37222 ± 290.28
Duration of circulatory arrest (min), mean ± SD28 ± 1027 ± 1030 ± 100.24
Duration of mechanical ventilation (days), mean ± SD4.4 ± 6.22.5 ± 3.17.1 ± 8.2<0.001
ICU length of stay (days), mean ± SD10 ± 88 ± 412 ± 110.009
SAPS II (points), mean ± SD26 ± 1022 ± 930 ± 10<0.001
ICU mortality, n (%)2 (2.5)02 (5.9)0.99
Total cohort (n = 80)Patients with TPR ≤ 900 dynes·s/cm5 (n = 46)Patients with TPR > 900 dynes·s/cm5 (n = 34)P-value
Age (years), mean ± SD57 ± 1657 ± 1661 ± 140.23
Male gender, n (%)30 (37)22 (48)8 (23)0.03
BMI (kg/m2), mean ± SD27.9 ± 7.029.6 ± 7.625.7 ± 5.30.01
BMI >30 kg/m2, n (%)22 (27)15 (33)7 (20)0.23
Body surface area (m2), mean ± SD1.90 ± 0.291.99 ± 0.311.78 ± 1.19<0.001
Ideal body surface area (m2), mean ± SD1.68 ± 0.181.71 ± 0.191.64 ± 0.150.11
Preoperative PaO2 (mmHg), mean ± SD65 ± 1266 ± 1364 ± 90.53
Total lung capacity (%), mean ± SD91 ± 1594 ± 1587 ± 130.07
Forced vital capacity (%), mean ± SD91 ± 2092 ± 2188 ± 180.33
FEV1 (%), mean ± SD87 ± 1988 ± 2084 ± 170.42
BNP (ng/l), median (IQR)80 (26–252)38 (20–111)192 (89–501)<0.001
PH-specific treatments, n (%)
 Epoprostenol1 (1)01 (3)0.24
 Bosentan25 (31)18 (39)7 (20)0.08
 Sildenafil18 (22)8 (17)10 (29)0.20
Need of dobutamine, n (%)9 (11)1 (2)8 (23)0.003
Duration of cardiopulmonary bypass (min), mean ± SD227 ± 34230 ± 37222 ± 290.28
Duration of circulatory arrest (min), mean ± SD28 ± 1027 ± 1030 ± 100.24
Duration of mechanical ventilation (days), mean ± SD4.4 ± 6.22.5 ± 3.17.1 ± 8.2<0.001
ICU length of stay (days), mean ± SD10 ± 88 ± 412 ± 110.009
SAPS II (points), mean ± SD26 ± 1022 ± 930 ± 10<0.001
ICU mortality, n (%)2 (2.5)02 (5.9)0.99

BMI: body mass index; BNP: serum brain natriuretic peptide level; FEV1: forced expiratory volume in the first second; ICU: intensive care unit; IQR: interquartile range; PaO2: partial pressure of oxygen in arterial blood; SAPS II: Simplified Acute Physiologic Score version II; SD: standard deviation; TPR: total pulmonary vascular resistance.

Table 1:
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Preoperative characteristics of the study population according to the pulmonary disease severity

Total cohort (n = 80)Patients with TPR ≤ 900 dynes·s/cm5 (n = 46)Patients with TPR > 900 dynes·s/cm5 (n = 34)P-value
Age (years), mean ± SD57 ± 1657 ± 1661 ± 140.23
Male gender, n (%)30 (37)22 (48)8 (23)0.03
BMI (kg/m2), mean ± SD27.9 ± 7.029.6 ± 7.625.7 ± 5.30.01
BMI >30 kg/m2, n (%)22 (27)15 (33)7 (20)0.23
Body surface area (m2), mean ± SD1.90 ± 0.291.99 ± 0.311.78 ± 1.19<0.001
Ideal body surface area (m2), mean ± SD1.68 ± 0.181.71 ± 0.191.64 ± 0.150.11
Preoperative PaO2 (mmHg), mean ± SD65 ± 1266 ± 1364 ± 90.53
Total lung capacity (%), mean ± SD91 ± 1594 ± 1587 ± 130.07
Forced vital capacity (%), mean ± SD91 ± 2092 ± 2188 ± 180.33
FEV1 (%), mean ± SD87 ± 1988 ± 2084 ± 170.42
BNP (ng/l), median (IQR)80 (26–252)38 (20–111)192 (89–501)<0.001
PH-specific treatments, n (%)
 Epoprostenol1 (1)01 (3)0.24
 Bosentan25 (31)18 (39)7 (20)0.08
 Sildenafil18 (22)8 (17)10 (29)0.20
Need of dobutamine, n (%)9 (11)1 (2)8 (23)0.003
Duration of cardiopulmonary bypass (min), mean ± SD227 ± 34230 ± 37222 ± 290.28
Duration of circulatory arrest (min), mean ± SD28 ± 1027 ± 1030 ± 100.24
Duration of mechanical ventilation (days), mean ± SD4.4 ± 6.22.5 ± 3.17.1 ± 8.2<0.001
ICU length of stay (days), mean ± SD10 ± 88 ± 412 ± 110.009
SAPS II (points), mean ± SD26 ± 1022 ± 930 ± 10<0.001
ICU mortality, n (%)2 (2.5)02 (5.9)0.99
Total cohort (n = 80)Patients with TPR ≤ 900 dynes·s/cm5 (n = 46)Patients with TPR > 900 dynes·s/cm5 (n = 34)P-value
Age (years), mean ± SD57 ± 1657 ± 1661 ± 140.23
Male gender, n (%)30 (37)22 (48)8 (23)0.03
BMI (kg/m2), mean ± SD27.9 ± 7.029.6 ± 7.625.7 ± 5.30.01
BMI >30 kg/m2, n (%)22 (27)15 (33)7 (20)0.23
Body surface area (m2), mean ± SD1.90 ± 0.291.99 ± 0.311.78 ± 1.19<0.001
Ideal body surface area (m2), mean ± SD1.68 ± 0.181.71 ± 0.191.64 ± 0.150.11
Preoperative PaO2 (mmHg), mean ± SD65 ± 1266 ± 1364 ± 90.53
Total lung capacity (%), mean ± SD91 ± 1594 ± 1587 ± 130.07
Forced vital capacity (%), mean ± SD91 ± 2092 ± 2188 ± 180.33
FEV1 (%), mean ± SD87 ± 1988 ± 2084 ± 170.42
BNP (ng/l), median (IQR)80 (26–252)38 (20–111)192 (89–501)<0.001
PH-specific treatments, n (%)
 Epoprostenol1 (1)01 (3)0.24
 Bosentan25 (31)18 (39)7 (20)0.08
 Sildenafil18 (22)8 (17)10 (29)0.20
Need of dobutamine, n (%)9 (11)1 (2)8 (23)0.003
Duration of cardiopulmonary bypass (min), mean ± SD227 ± 34230 ± 37222 ± 290.28
Duration of circulatory arrest (min), mean ± SD28 ± 1027 ± 1030 ± 100.24
Duration of mechanical ventilation (days), mean ± SD4.4 ± 6.22.5 ± 3.17.1 ± 8.2<0.001
ICU length of stay (days), mean ± SD10 ± 88 ± 412 ± 110.009
SAPS II (points), mean ± SD26 ± 1022 ± 930 ± 10<0.001
ICU mortality, n (%)2 (2.5)02 (5.9)0.99

BMI: body mass index; BNP: serum brain natriuretic peptide level; FEV1: forced expiratory volume in the first second; ICU: intensive care unit; IQR: interquartile range; PaO2: partial pressure of oxygen in arterial blood; SAPS II: Simplified Acute Physiologic Score version II; SD: standard deviation; TPR: total pulmonary vascular resistance.

Haemodynamic results 48 h after pulmonary endarterectomy in patients with and without severe chronic thromboembolic pulmonary hypertension

Table 2 shows marked differences between patients with and without severe CTEPH before PEA, and the improvement in mean PAP, CO and TPR after PEA in both groups. LV ejection fraction decreased from 66 ± 10% to 60 ± 6% in both groups (P < 0.001).

Table 2:
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Preoperative and postoperative (48 h after surgery) haemodynamic data in 80 patients with repeated measurements (data are expressed as mean ± SD)

VariablesBefore surgery
Between group P-valueAfter surgery
Between group P-value
TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)
Mean pulmonary arterial pressure (mmHg)40 ± 1154 ± 9<0.000124 ± 6*28 ± 6†0.015
Cardiac output (l/min)5.5 ± 1.23.6 ± 0.7<0.00015.4 ± 1.84.5 ± 0.9‡0.013
Ideal cardiac index (l/min/m2)a3.2 ± 0.72.2 ± 0.4<0.00013.2 ± 0.72.7 ± 0.6#0.005
TPR (dynes·s/cm5)648 ± 1921224 ± 272<0.0001399 ± 180**548 ± 2012††0.001
Right atrial pressure (mmHg)7.7 ± 4.711.2 ± 6.70.0086.9 ± 3.66.8 ± 3.2‡‡0.98
Need of mechanical ventilation, n (%)17 (37)26 (76)<0.001
Tidal volume (ml/kg)6.6 ± 1.67.6 ± 1.60.05
Positive end-expiratory pressure (cmH2O)6.0 ± 2.96.7 ± 2.70.49
Respiratory rate (breaths/min)19 ± 418 ± 30.13
Mean arterial pressure (mmHg)93 ± 1389 ± 140.1887 ± 9##82 ± 10***0.03
Heart rate (beats/min)80 ± 1781 ± 100.7189 ± 1585 ± 12†††0.31
VariablesBefore surgery
Between group P-valueAfter surgery
Between group P-value
TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)
Mean pulmonary arterial pressure (mmHg)40 ± 1154 ± 9<0.000124 ± 6*28 ± 6†0.015
Cardiac output (l/min)5.5 ± 1.23.6 ± 0.7<0.00015.4 ± 1.84.5 ± 0.9‡0.013
Ideal cardiac index (l/min/m2)a3.2 ± 0.72.2 ± 0.4<0.00013.2 ± 0.72.7 ± 0.6#0.005
TPR (dynes·s/cm5)648 ± 1921224 ± 272<0.0001399 ± 180**548 ± 2012††0.001
Right atrial pressure (mmHg)7.7 ± 4.711.2 ± 6.70.0086.9 ± 3.66.8 ± 3.2‡‡0.98
Need of mechanical ventilation, n (%)17 (37)26 (76)<0.001
Tidal volume (ml/kg)6.6 ± 1.67.6 ± 1.60.05
Positive end-expiratory pressure (cmH2O)6.0 ± 2.96.7 ± 2.70.49
Respiratory rate (breaths/min)19 ± 418 ± 30.13
Mean arterial pressure (mmHg)93 ± 1389 ± 140.1887 ± 9##82 ± 10***0.03
Heart rate (beats/min)80 ± 1781 ± 100.7189 ± 1585 ± 12†††0.31
a

Ideal cardiac index was defined as followed: cardiac output divided by ideal body surface area.

Within-group comparisons: * and †P < 0.001 before and after surgery; ‡P < 0.001 before and after surgery 3; #P < 0.001 before and after surgery; ** and ††P < 0.001 before and after surgery; ‡‡P<0.001 before and after surgery; ##P <0.001 and ***P = 0.05 before and after surgery; ##P = 0.05 before and after surgery; †††P = 0.002 before and after surgery.

SD: standard deviation; TPR: total pulmonary vascular resistance.

Table 2:
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Preoperative and postoperative (48 h after surgery) haemodynamic data in 80 patients with repeated measurements (data are expressed as mean ± SD)

VariablesBefore surgery
Between group P-valueAfter surgery
Between group P-value
TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)
Mean pulmonary arterial pressure (mmHg)40 ± 1154 ± 9<0.000124 ± 6*28 ± 6†0.015
Cardiac output (l/min)5.5 ± 1.23.6 ± 0.7<0.00015.4 ± 1.84.5 ± 0.9‡0.013
Ideal cardiac index (l/min/m2)a3.2 ± 0.72.2 ± 0.4<0.00013.2 ± 0.72.7 ± 0.6#0.005
TPR (dynes·s/cm5)648 ± 1921224 ± 272<0.0001399 ± 180**548 ± 2012††0.001
Right atrial pressure (mmHg)7.7 ± 4.711.2 ± 6.70.0086.9 ± 3.66.8 ± 3.2‡‡0.98
Need of mechanical ventilation, n (%)17 (37)26 (76)<0.001
Tidal volume (ml/kg)6.6 ± 1.67.6 ± 1.60.05
Positive end-expiratory pressure (cmH2O)6.0 ± 2.96.7 ± 2.70.49
Respiratory rate (breaths/min)19 ± 418 ± 30.13
Mean arterial pressure (mmHg)93 ± 1389 ± 140.1887 ± 9##82 ± 10***0.03
Heart rate (beats/min)80 ± 1781 ± 100.7189 ± 1585 ± 12†††0.31
VariablesBefore surgery
Between group P-valueAfter surgery
Between group P-value
TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)TPR ≤ 900 dynes·s/cm5 (n = 46)TPR > 900 dynes·s/cm5 (n = 34)
Mean pulmonary arterial pressure (mmHg)40 ± 1154 ± 9<0.000124 ± 6*28 ± 6†0.015
Cardiac output (l/min)5.5 ± 1.23.6 ± 0.7<0.00015.4 ± 1.84.5 ± 0.9‡0.013
Ideal cardiac index (l/min/m2)a3.2 ± 0.72.2 ± 0.4<0.00013.2 ± 0.72.7 ± 0.6#0.005
TPR (dynes·s/cm5)648 ± 1921224 ± 272<0.0001399 ± 180**548 ± 2012††0.001
Right atrial pressure (mmHg)7.7 ± 4.711.2 ± 6.70.0086.9 ± 3.66.8 ± 3.2‡‡0.98
Need of mechanical ventilation, n (%)17 (37)26 (76)<0.001
Tidal volume (ml/kg)6.6 ± 1.67.6 ± 1.60.05
Positive end-expiratory pressure (cmH2O)6.0 ± 2.96.7 ± 2.70.49
Respiratory rate (breaths/min)19 ± 418 ± 30.13
Mean arterial pressure (mmHg)93 ± 1389 ± 140.1887 ± 9##82 ± 10***0.03
Heart rate (beats/min)80 ± 1781 ± 100.7189 ± 1585 ± 12†††0.31
a

Ideal cardiac index was defined as followed: cardiac output divided by ideal body surface area.

Within-group comparisons: * and †P < 0.001 before and after surgery; ‡P < 0.001 before and after surgery 3; #P < 0.001 before and after surgery; ** and ††P < 0.001 before and after surgery; ‡‡P<0.001 before and after surgery; ##P <0.001 and ***P = 0.05 before and after surgery; ##P = 0.05 before and after surgery; †††P = 0.002 before and after surgery.

SD: standard deviation; TPR: total pulmonary vascular resistance.

Changes in right ventricular echocardiographic parameters during the first 3 postoperative days

Right ventricle dimension

RVEDA/LVEDA ratio was available in 21 patients both in the preoperative and postoperative period (11 and 10 patients without and with severe CTEPH, respectively). RVEDA/LVEDA ratio significantly decreased after PEA during the day 1–day 3 period (1.19 ± 0.43 vs 0.97 ± 0.21, respectively; P = 0.002). Decrease in RVEDA/LVEDA ratio affected mainly patients with TPR >900 dynes·s/cm5 [1.54 ± 0.47 vs 1.04 ± 0.21 (P < 0.001)]. RVEDA/LVEDA ratio changes versus the preoperative value in the group with and without severe CTEPH were −33.3% (95% confidence interval −36.7 to −19.9) versus −3.5% (−21.7 to 17.9) (P = 0.001) (Table 3). There was a significant correlation between changes in RVEDA/LVEDA ratio and changes in TPR (Y = 5.85 + 0.55 × X; r = 0.57; P = 0.007) (Fig. 2).

Relationship between changes in right ventricular size and changes in pulmonary vascular resistances after pulmonary endarterectomy. LVEDA: left ventricular end-diastolic area; RVEDA: right ventricular end-diastolic area; TPR: total pulmonary vascular resistance.
Figure 2:

Relationship between changes in right ventricular size and changes in pulmonary vascular resistances after pulmonary endarterectomy. LVEDA: left ventricular end-diastolic area; RVEDA: right ventricular end-diastolic area; TPR: total pulmonary vascular resistance.

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Table 3:
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Evaluation of systolic right ventricular function and use of vasoactive drugs

VariablesBefore surgery
P-valueDay 1–day 3 after surgery
P-value
≤900 dynes·s/cm5>900 dynes·s/cm5≤900 dynes·s/cm5>900 dynes·s/cm5
Right over left ventricular end-diastolic area, mean ± SD0.97 ± 0.231.48 ± 0.460.0030.93 ± 0.231.01 ± 0.20*0.44
 Patients under dobutamine, n (%)03 (33)1 (8)4 (44)
 Patients under norepinephrine, n (%)0002 (22)
Tricuspid annular plane systolic excursion (cm), mean ± SD20.0 ± 4.215.3 ± 5.60.0110.6 ± 1.4†9.6 ± 1.7‡0.10
 Patients under dobutamine, n (%)05 (29)2 (12)6 (26)
 Patients under norepinephrine, n (%)002 (16)6 (42)
Tissue Doppler-derived tricuspid lateral annular systolic velocity (S’) (cm/s), mean ± SD12.5 ± 2.810.9 ± 2.60.028.6 ± 1.6#7.3 ± 1.7**0.65
 Patients under dobutamine, n (%)07 (29)5 (16)8 (33)
 Patients under norepinephrine, n (%)006 (19)13 (54)
VariablesBefore surgery
P-valueDay 1–day 3 after surgery
P-value
≤900 dynes·s/cm5>900 dynes·s/cm5≤900 dynes·s/cm5>900 dynes·s/cm5
Right over left ventricular end-diastolic area, mean ± SD0.97 ± 0.231.48 ± 0.460.0030.93 ± 0.231.01 ± 0.20*0.44
 Patients under dobutamine, n (%)03 (33)1 (8)4 (44)
 Patients under norepinephrine, n (%)0002 (22)
Tricuspid annular plane systolic excursion (cm), mean ± SD20.0 ± 4.215.3 ± 5.60.0110.6 ± 1.4†9.6 ± 1.7‡0.10
 Patients under dobutamine, n (%)05 (29)2 (12)6 (26)
 Patients under norepinephrine, n (%)002 (16)6 (42)
Tissue Doppler-derived tricuspid lateral annular systolic velocity (S’) (cm/s), mean ± SD12.5 ± 2.810.9 ± 2.60.028.6 ± 1.6#7.3 ± 1.7**0.65
 Patients under dobutamine, n (%)07 (29)5 (16)8 (33)
 Patients under norepinephrine, n (%)006 (19)13 (54)

Except in the preoperative setting, there was no significant difference between the 2 groups concerning administration of dobutamine. Patients under norepinephrine were always significantly more frequent in the severe group (>900 dynes·s/cm5).

Within-group comparisons: *P = 0.001 before surgery versus day 1–day 3; †P < 0.001 before surgery versus day 1–day 3; ‡P = 0.001 before surgery versus day 1–day 3. #P < 0.001 before surgery versus day 1–day 3; **P < 0.001 before surgery versus day 1–day 3.

SD: standard deviation.

Table 3:
Open in new tab

Evaluation of systolic right ventricular function and use of vasoactive drugs

VariablesBefore surgery
P-valueDay 1–day 3 after surgery
P-value
≤900 dynes·s/cm5>900 dynes·s/cm5≤900 dynes·s/cm5>900 dynes·s/cm5
Right over left ventricular end-diastolic area, mean ± SD0.97 ± 0.231.48 ± 0.460.0030.93 ± 0.231.01 ± 0.20*0.44
 Patients under dobutamine, n (%)03 (33)1 (8)4 (44)
 Patients under norepinephrine, n (%)0002 (22)
Tricuspid annular plane systolic excursion (cm), mean ± SD20.0 ± 4.215.3 ± 5.60.0110.6 ± 1.4†9.6 ± 1.7‡0.10
 Patients under dobutamine, n (%)05 (29)2 (12)6 (26)
 Patients under norepinephrine, n (%)002 (16)6 (42)
Tissue Doppler-derived tricuspid lateral annular systolic velocity (S’) (cm/s), mean ± SD12.5 ± 2.810.9 ± 2.60.028.6 ± 1.6#7.3 ± 1.7**0.65
 Patients under dobutamine, n (%)07 (29)5 (16)8 (33)
 Patients under norepinephrine, n (%)006 (19)13 (54)
VariablesBefore surgery
P-valueDay 1–day 3 after surgery
P-value
≤900 dynes·s/cm5>900 dynes·s/cm5≤900 dynes·s/cm5>900 dynes·s/cm5
Right over left ventricular end-diastolic area, mean ± SD0.97 ± 0.231.48 ± 0.460.0030.93 ± 0.231.01 ± 0.20*0.44
 Patients under dobutamine, n (%)03 (33)1 (8)4 (44)
 Patients under norepinephrine, n (%)0002 (22)
Tricuspid annular plane systolic excursion (cm), mean ± SD20.0 ± 4.215.3 ± 5.60.0110.6 ± 1.4†9.6 ± 1.7‡0.10
 Patients under dobutamine, n (%)05 (29)2 (12)6 (26)
 Patients under norepinephrine, n (%)002 (16)6 (42)
Tissue Doppler-derived tricuspid lateral annular systolic velocity (S’) (cm/s), mean ± SD12.5 ± 2.810.9 ± 2.60.028.6 ± 1.6#7.3 ± 1.7**0.65
 Patients under dobutamine, n (%)07 (29)5 (16)8 (33)
 Patients under norepinephrine, n (%)006 (19)13 (54)

Except in the preoperative setting, there was no significant difference between the 2 groups concerning administration of dobutamine. Patients under norepinephrine were always significantly more frequent in the severe group (>900 dynes·s/cm5).

Within-group comparisons: *P = 0.001 before surgery versus day 1–day 3; †P < 0.001 before surgery versus day 1–day 3; ‡P = 0.001 before surgery versus day 1–day 3. #P < 0.001 before surgery versus day 1–day 3; **P < 0.001 before surgery versus day 1–day 3.

SD: standard deviation.

The significant correlation between preoperative RVEDA/LVEDA ratio and preoperative ICI is shown in Fig. 3A. In the early postoperative period, a persistently significant correlation was found between postoperative RVEDA/LVEDA ratio and the postoperative ICI, as illustrated in Fig. 3B. The r-values before and after PEA were not significantly different (P-value one-sided test statistic Z = 0.49).

Linear regression analysis between ICI and right ventricular size (RVEDA:LVEDA ratio) (n = 21), S’ velocity (n = 55) or TAPSE (n = 32). Linear regression analysis formula is displayed on each panel with the corresponding r-value. (A) Preoperative relationship between ICI and RVEDA:LVEDA ratio. The analysis included 21 patients. (B) Postoperative relationship between ICI and RVEDA:LVEDA ratio. The analysis included 21 patients. (C) Preoperative relationship between ICI and S’ velocity. The analysis included 55 patients. (D) Postoperative relationship between ICI and S’ velocity. The analysis included 55 patients. (E) Preoperative relationship between ICI and TAPSE. The analysis included 34 patients. (F) Postoperative relationship between ICI and TAPSE. The analysis included 34 patients. ICI: ideal cardiac index; LVEDA: left ventricular end-diastolic area; RVEDA: right ventricular end-diastolic area; S’ velocity: systolic tricuspid annular velocity; TAPSE: tricuspid annular plane systolic excursion.
Figure 3:

Linear regression analysis between ICI and right ventricular size (RVEDA:LVEDA ratio) (n = 21), S’ velocity (n = 55) or TAPSE (n = 32). Linear regression analysis formula is displayed on each panel with the corresponding r-value. (A) Preoperative relationship between ICI and RVEDA:LVEDA ratio. The analysis included 21 patients. (B) Postoperative relationship between ICI and RVEDA:LVEDA ratio. The analysis included 21 patients. (C) Preoperative relationship between ICI and S’ velocity. The analysis included 55 patients. (D) Postoperative relationship between ICI and S’ velocity. The analysis included 55 patients. (E) Preoperative relationship between ICI and TAPSE. The analysis included 34 patients. (F) Postoperative relationship between ICI and TAPSE. The analysis included 34 patients. ICI: ideal cardiac index; LVEDA: left ventricular end-diastolic area; RVEDA: right ventricular end-diastolic area; S’ velocity: systolic tricuspid annular velocity; TAPSE: tricuspid annular plane systolic excursion.

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Tricuspid annular plane systolic excursion and systolic tricuspid annular velocity

TAPSE and S’ velocity were studied both in the preoperative and postoperative period in 32 and 55 patients, respectively. In both groups, RV systolic function evaluated by TAPSE and S’ velocity decreased in the early postoperative period.

The significant correlations between preoperative S’ velocity or preoperative TAPSE and preoperative cardiac index are shown in Fig. 3C and E, respectively. However, in the early postoperative period, there was no correlation between S’ velocity (Fig. 3D) or TAPSE (Fig. 3F) and ICI. The r-values before and after PEA were significantly different (P-value one-sided test statistic Z = 0.045 and 0.059, respectively).

DISCUSSION

Our study suggests that improvement in RV size occurs very early in the postoperative period of PEA and is correlated with better CO. In contrast, annular parameters (TAPSE or S’ velocity) did not reflect an improvement in RV function after PEA.

Early invasive haemodynamic data are in accordance with those from earlier studies with a decrease in TPR and an increase in CO [17–20]. We reported a very early decrease in RV dimensions, evaluated by the RVEDA/LVEDA ratio, starting as early as the first postoperative day after PEA, which positively correlated with the ICI. Of course, we acknowledge that ICI does not fully characterize RV function. Previous studies have shown a decrease in RV dimension either using 2- or 3-dimensional echocardiography or cardiac magnetic resonance [17–19, 22, 23] in a time period ranging from hours to 12 days after PEA. We also confirmed that the improvement in RVEDA/LVEDA ratio was more important in patients with a high preoperative TPR than previously described [22]. One study reported that RVEDA/LVEDA ratio was related to the severity of circulatory failure after thrombolysis of major pulmonary embolism [12]. PEA has been shown to restore RV remodelling by an acute reduction in RV afterload [22, 24]. Although PVR appeared to be the most critical measure after PEA [19, 24], PVR is an imperfect surrogate for total RV afterload [25]. Thus, the RV loading conditions are not normalized although PAP nearly normalized [26]. We found a relationship between changes in RV dimensions and PVR, which has not been confirmed in other studies [18], perhaps because intraoperative investigation was performed too early after PEA [18]. Finally, the immediate postoperative RV function is a consequence of intraoperative RV ischaemia, postoperative stunning, septal damage [14, 23], level of preload, and the degree of decrease in RV afterload. The RVEDA/LVEDA ratio appears to be a good and simple echocardiographic parameter for evaluating the success of PEA. Interestingly, a decrease in RV dimensions is a univariate predictor of good outcome [19].

TAPSE decreased after PEA by 40–50% [5, 19, 22, 23, 27] and S’ velocity by 20% [19], which would theoretically reflect a worsening of the RV systolic function. A reduction of up to 50% of these longitudinal parameters after cardiac surgery has also been reported [14, 28]. This occurred in association with the opening of the pericardium [13, 15] and after weaning from cardiopulmonary bypass [13, 15]. These changes are probably related to altered geometry or contraction pattern as overall RV systolic function is preserved when assessed by other parameters [15]. Although TAPSE and S’ velocity correlated well with PVR, mean pulmonary artery pressure (mPAP) and CO [7, 8] in the preoperative period, such a relationship was not found after PEA while it seemed that the systolic RV function improved [5, 23]. One study reported a good correlation between TAPSE and RV ejection fraction after PEA [16]. However, a large majority of patients in this study received dobutamine, which increased the annular parameters [29]. Surprisingly, RV ejection fraction was not related to CO [16] while it was previously reported that RV ejection fraction was directly correlated with CO in PAH [30].

Our findings suggest that RVEDA/LVEDA ratio may be more useful to describe the surgical success of PEA than TAPSE and S’ velocity. Therefore, fluid management and prescription of vasoactive drugs should not be guided by low longitudinal annular parameters.

Limitations

Our study has several limitations. First, it is a retrospective study but based on real-time echocardiographic measurements. Second, haemodynamic and Doppler echocardiographic data were not obtained simultaneously in the preoperative period. However, all the studied patients were haemodynamically stable and the possible impact of such a delay is probably minimal. Third, the number of the systolic RV functional parameters recorded varied among patients. Thus, the small numbers of patients must be taken into account when drawing any conclusions. Fourth, some patients required inotropic support and/or mechanical ventilation in the postoperative period. Vasoactive drugs could have affected the longitudinal dimensions of the RV postoperatively [29] but tidal volume set at 6 ml/kg of ideal body weight probably did not affect the pulmonary resistances [10]. Finally, tricuspid regurgitation was not evaluated.

CONCLUSION

In conclusion, improvement of the RVEDA/LVEDA ratio started as early as the first postoperative day and described the surgical success of PEA and lowering of TPR. Such changes are more pronounced in the severe form of CTEPH. Annular parameters of RV function (TAPSE and S’ velocity) should not be used in this immediate period after PEA as they correlate poorly with postoperative ICI. Recognizing this limitation is important in minimizing an overdiagnosis of RV dysfunction after PEA.

Funding

This work was supported solely by institutional and/or departmental sources.

Conflict of interest: François Stéphan has received fees from Fisher and Paykel Healthcare for scientific conferences. All other authors declared no conflict of interest.

Author contributions

Saida Rézaiguia-Delclaux: Conceptualization; Data curation; Formal analysis; Writing—original draft. François Haddad: Conceptualization; Formal analysis; Methodology; Writing—review & editing. Catherine Pilorge: Conceptualization; Formal analysis; Writing—review & editing. Myriam Amsallem: Conceptualization; Methodology; Writing—review & editing. Elie Fadel: Writing—review & editing. François Stéphan: Conceptualization; Formal analysis; Methodology; Supervision; Writing—original draft.

Reviewer information

Interactive CardioVascular and Thoracic Surgery thanks Petre Vlah-Horea Botianu and the other, anonymous reviewer(s) for their contribution to the peer review process of this article.

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ABBREVIATIONS

     
  • CO

    Cardiac output

    •  
  • CTEPH

    Chronic thromboembolic pulmonary hypertension

    •  
  • ICI

    Ideal cardiac index

    •  
  • ICU

    Intensive care unit

    •  
  • LV

    Left ventricular

    •  
  • LVEDA

    Left ventricular end-diastolic area

    •  
  • PAC

    Pulmonary artery catheter

    •  
  • PAP

    Pulmonary artery pressure

    •  
  • PEA

    Pulmonary endarterectomy

    •  
  • PVR

    Pulmonary vascular resistances

    •  
  • RV

    Right ventricular

    •  
  • RVEDA

    Right ventricular end-diastolic area

    •  
  • S’velocity

    Systolic tricuspid annular velocity

    •  
  • TAPSE

    Tricuspid annular plane systolic excursion

    •  
  • TPR

    Total pulmonary vascular resistance

© The Author(s) 2020. 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)
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