Abstract
For cardiac implantable electronic device (CIED) implantations, visualization of lead placement is necessary and fluoroscopy remains by far the most commonly used technique. With simple changes in the X-ray system settings, total radiation dose can be reduced significantly. The purpose of this study was to assess the safety and efficacy of various CIED implantations performed after implementation of a new dose reduction protocol (DRP).
We conducted a retrospective chart review of 584 patients undergoing CIED implantation or revision in our hospital. Of these patients, 280 (48%) underwent the implantation prior to and 304 (52%) after the DRP introduction. The DRP included various changes for optimized image processing and exposure system settings to enable dose reduction, as well as a reduced frame rates (4 FPS for fluoroscopy and 7.5 FPS for cinematographic images). Of the 584 patients, 53 (9.1%) had a one-chamber pacemaker, 232 (39.7%) a two-chamber pacemaker, 133 (22.8%) a one-chamber ICD, 35 (6.0%) a two-chamber ICD, 82 (14.0%) a CRT (de novo) implantation, and 49 (8.3%) had an upgrade to a CRT device. DRP was associated with a 64% reduction of the dose-area product (1372 ± 2659 vs. 3792 ± 5025 cGcm2, P < 0.001), while fluoroscopy duration (13 ± 15 vs. 13 ± 15 min) and procedural duration (93 ± 52 vs. 92 ± 52 min.) did not significantly increase. Complication rates did not differ significantly between the two groups.
The DRP proved to effectively reduce radiation dose for all types of CIED implantations. Fluoroscopy time, total procedure time, and the number of complications did not increase after introducing the DRP.
Evaluation of a dose reduction protocol in 584 CIED implantations leading to a dose reduction of more than 64%.
Proven safety of the changes made including the use of a reduced frame rate of 4 FPS.
Introduction
For most cardiac implantable electronic device (CIED), implantations visual guidance of lead placement is necessary. Despite new developments of non-fluoroscopic options,1 fluoroscopy remains by far the most commonly used technique.
Cumulative radiation exposure can be detrimental to the patient and the staff with radiation hazards ranging from cataracts to malignancy.2,3 The estimated additional lifetime cancer risk due to radiation exposure during a single cardiovascular procedure ranges from 1/1000 to 1/2000.4 Awareness of these consequences is growing and various efforts are being made to reduce radiation exposure for all types of interventional cardiac procedures.2
With simple changes in the X-ray system settings (lower frame rate, lower dose per frame), total radiation dose could be reduced significantly. On the other hand, decreasing radiation dose leads to lower quality images that potentially could prolong procedures and cause complications.
The purpose of this study was to assess the safety and efficacy of using a new dose reduction protocol (DRP) for various types of CIED implantations.
Methods
This study is based on a single-centre retrospective chart review of 584 patients undergoing CIED implantation. It is approved by the institutional ethical committee. To maintain consistency regarding potential machine-related differences, reviewed procedures were all performed with the same X-ray system. Operators did not change after DRP implementation. The procedures were performed between 2011 and 2015.
Patient demographics, including weight and height, and relevant comorbidities as well as procedural and fluoroscopy time were obtained. Cumulative radiation dose was measured using dose-area product (DAP). Rates of success and complications for the different procedure types were recorded before and after the DRP.
Dose reducing protocol
Procedures were performed using a Siemens Axiom Artis dBC (Siemens, Erlangen, Germany) interventional X-ray system.
Pre-DRP fluoroscopic and cineangiographic images were acquired at 15 and 7.5 frames per second (FPS), respectively. After the DRP was established, default settings were changed to a new protocol, which was used for all CIED implantations from then on. For this protocol, fluoroscopic images were acquired at 4 FPS, and default fluoroscopy dose rate mode that was changed from normal to low.
The ‘low dose’ programme that was established in cooperation with the manufacturer included optimized image processing and exposure system settings to enable dose reduction. Most importantly, the introduction of copper filtration (0.1–0.2 mm thickness), the reduction in the peak kilovoltage from 125 to 102, lower detector dose (reduced from 170 to 120 nGy), shorter pulse width (6.4–5 ms), and the selection of a smaller focus.
For all procedures before and after introducing the DRP, standard ALARA principles were applied. This included minimizing cine loop acquisition and using anterior–posterior view whenever possible as well as the use of collimation and minimal magnification.
Dose-area product was used as parameter comparing both protocols as it strongly correlates with skin dose,5 and it is commonly used for objective comparisons between X-ray systems,6 even though it should be considered an upper limit for accumulated patient radiation dose as the patient does not cover the entire field of view in certain tube angulations.
Statistical analysis
For comparison of categorical variables among groups, χ2 test was used. Independent sample t-test (normally distributed data) or Mann–Whitney U test (skewed data) was used to compare continuous variables. All analyses were performed using SPSS software version 20.0 (SPSS Inc., Chicago, IL, USA). Data are presented as absolute numbers and percentages for categorical variables or mean ± standard deviation (SD) for continuous variables. A P-value of <0.05 was considered statistically significant.
Results
Patient characteristics
Of the 584 patients included in the study, a total of 280 consecutive patients (48%) were treated before and 304 consecutive patients (52%) after implementation of the DRP. With regard to baseline characteristics, pre-DRP and post-DRP patients were not different in terms of age, gender, and BMI. Table 1 shows the baseline characteristics of the included patients.
Patient characteristics
| Parameter | Total (n = 584) | Before DRP implementation (n = 280) | After DRP implementation (n = 304) | Significance |
|---|---|---|---|---|
| Age, mean ± SD (years) | 70 ± 13 (17–94) | 69 ± 13 (23–94) | 71 ± 13 (17–91) | n.s. |
| Male gender, n (%) | 381 (65.2) | 181 (64.6) | 200 (65.8) | n.s. |
| Body mass index, mean ± SD (kg/m2) | 27.6 ± 5.5 (14.8–69.2) | 27.6 ± 5.2 (17.0–57.1) | 27.4 ± 5.8 (14.8–69.2) | n.s. |
| One-chamber pacemaker, n (%) | 53 (9.1) | 31 (11.1) | 22 (7.2) | n.s. |
| Two-chamber pacemaker, n (%) | 232 (39.7) | 104 (37.1) | 128 (42.1) | n.s. |
| One-chamber ICD, n (%) | 133 (22.8) | 71 (25.4) | 62 (20.4) | n.s. |
| Two-chamber ICD, n (%) | 35 (6.0) | 19 (6.8) | 16 (5.3) | n.s. |
| CRT (de novo), n (%) | 82 (14.0) | 39 (13.9) | 43 (14.1) | n.s. |
| CRT (upgrade), n (%) | 49 (8.3) | 16 (5.7) | 33 (10.9) | P = 0.025 |
| Oral anticoagulation, n (%) | 297 (50.9) | 132 (47.1) | 165 (54.3) | n.s. |
| Antiplatelet therapy, n (%) | 330 (56.5) | 166 (59.3) | 164 (53.9) | n.s. |
| Left ventricular ejection fraction, mean ± SD (%) | 43 ± 14.9 (5–70) | 44 ± 14.7 (15–66) | 43 ± 15.1 (5–70) | n.s. |
| NYHA class, mean ± SD (%) | 2.5 ± 2.4 (0–4) | 2.7 ± 3.6 (1–4) | 2.3 ± 0.7 (0–4) | n.s. |
| ASA class, mean ± SD (%) | 2.7 ± 0.6 (1–5) | 2.7 ± 0.5 (1–5) | 2.6 ± 0.6 (1–4) | n.s. |
| Procedure duration, mean ± SD (min) | 92 ± 52 (23–320) | 92 ± 52 (28–320) | 93 ± 52 (23–285) | n.s. |
| Fluroscopy duration, mean ± SD (min) | 13 ± 15 (0–86) | 13 ± 15 (0–84) | 13 ± 15 (0–86) | n.s. |
| Dose area product, mean ± SD (cGcm2) | 2517 ± 4136 (3–31 326) | 3792 ± 5025 (108–31 326) | 1372 ± 2659 (3–25 343) | P < 0.001 |
| Procedure success, n (%) | 568 (97.3) | 275 (98.2) | 293 (96.4) | n.s. |
| Parameter | Total (n = 584) | Before DRP implementation (n = 280) | After DRP implementation (n = 304) | Significance |
|---|---|---|---|---|
| Age, mean ± SD (years) | 70 ± 13 (17–94) | 69 ± 13 (23–94) | 71 ± 13 (17–91) | n.s. |
| Male gender, n (%) | 381 (65.2) | 181 (64.6) | 200 (65.8) | n.s. |
| Body mass index, mean ± SD (kg/m2) | 27.6 ± 5.5 (14.8–69.2) | 27.6 ± 5.2 (17.0–57.1) | 27.4 ± 5.8 (14.8–69.2) | n.s. |
| One-chamber pacemaker, n (%) | 53 (9.1) | 31 (11.1) | 22 (7.2) | n.s. |
| Two-chamber pacemaker, n (%) | 232 (39.7) | 104 (37.1) | 128 (42.1) | n.s. |
| One-chamber ICD, n (%) | 133 (22.8) | 71 (25.4) | 62 (20.4) | n.s. |
| Two-chamber ICD, n (%) | 35 (6.0) | 19 (6.8) | 16 (5.3) | n.s. |
| CRT (de novo), n (%) | 82 (14.0) | 39 (13.9) | 43 (14.1) | n.s. |
| CRT (upgrade), n (%) | 49 (8.3) | 16 (5.7) | 33 (10.9) | P = 0.025 |
| Oral anticoagulation, n (%) | 297 (50.9) | 132 (47.1) | 165 (54.3) | n.s. |
| Antiplatelet therapy, n (%) | 330 (56.5) | 166 (59.3) | 164 (53.9) | n.s. |
| Left ventricular ejection fraction, mean ± SD (%) | 43 ± 14.9 (5–70) | 44 ± 14.7 (15–66) | 43 ± 15.1 (5–70) | n.s. |
| NYHA class, mean ± SD (%) | 2.5 ± 2.4 (0–4) | 2.7 ± 3.6 (1–4) | 2.3 ± 0.7 (0–4) | n.s. |
| ASA class, mean ± SD (%) | 2.7 ± 0.6 (1–5) | 2.7 ± 0.5 (1–5) | 2.6 ± 0.6 (1–4) | n.s. |
| Procedure duration, mean ± SD (min) | 92 ± 52 (23–320) | 92 ± 52 (28–320) | 93 ± 52 (23–285) | n.s. |
| Fluroscopy duration, mean ± SD (min) | 13 ± 15 (0–86) | 13 ± 15 (0–84) | 13 ± 15 (0–86) | n.s. |
| Dose area product, mean ± SD (cGcm2) | 2517 ± 4136 (3–31 326) | 3792 ± 5025 (108–31 326) | 1372 ± 2659 (3–25 343) | P < 0.001 |
| Procedure success, n (%) | 568 (97.3) | 275 (98.2) | 293 (96.4) | n.s. |
AF, atrial fibrillation; ASA, American Society of Anesthesiologists; CRT, cardiac resynchronization therapy; COPD, chronic obstructive pulmonary disease; ICD, implantable cardioverter defibrillator; n.s., not significant; NYHA, New york heart association; SD, standard deviation.
Patient characteristics
| Parameter | Total (n = 584) | Before DRP implementation (n = 280) | After DRP implementation (n = 304) | Significance |
|---|---|---|---|---|
| Age, mean ± SD (years) | 70 ± 13 (17–94) | 69 ± 13 (23–94) | 71 ± 13 (17–91) | n.s. |
| Male gender, n (%) | 381 (65.2) | 181 (64.6) | 200 (65.8) | n.s. |
| Body mass index, mean ± SD (kg/m2) | 27.6 ± 5.5 (14.8–69.2) | 27.6 ± 5.2 (17.0–57.1) | 27.4 ± 5.8 (14.8–69.2) | n.s. |
| One-chamber pacemaker, n (%) | 53 (9.1) | 31 (11.1) | 22 (7.2) | n.s. |
| Two-chamber pacemaker, n (%) | 232 (39.7) | 104 (37.1) | 128 (42.1) | n.s. |
| One-chamber ICD, n (%) | 133 (22.8) | 71 (25.4) | 62 (20.4) | n.s. |
| Two-chamber ICD, n (%) | 35 (6.0) | 19 (6.8) | 16 (5.3) | n.s. |
| CRT (de novo), n (%) | 82 (14.0) | 39 (13.9) | 43 (14.1) | n.s. |
| CRT (upgrade), n (%) | 49 (8.3) | 16 (5.7) | 33 (10.9) | P = 0.025 |
| Oral anticoagulation, n (%) | 297 (50.9) | 132 (47.1) | 165 (54.3) | n.s. |
| Antiplatelet therapy, n (%) | 330 (56.5) | 166 (59.3) | 164 (53.9) | n.s. |
| Left ventricular ejection fraction, mean ± SD (%) | 43 ± 14.9 (5–70) | 44 ± 14.7 (15–66) | 43 ± 15.1 (5–70) | n.s. |
| NYHA class, mean ± SD (%) | 2.5 ± 2.4 (0–4) | 2.7 ± 3.6 (1–4) | 2.3 ± 0.7 (0–4) | n.s. |
| ASA class, mean ± SD (%) | 2.7 ± 0.6 (1–5) | 2.7 ± 0.5 (1–5) | 2.6 ± 0.6 (1–4) | n.s. |
| Procedure duration, mean ± SD (min) | 92 ± 52 (23–320) | 92 ± 52 (28–320) | 93 ± 52 (23–285) | n.s. |
| Fluroscopy duration, mean ± SD (min) | 13 ± 15 (0–86) | 13 ± 15 (0–84) | 13 ± 15 (0–86) | n.s. |
| Dose area product, mean ± SD (cGcm2) | 2517 ± 4136 (3–31 326) | 3792 ± 5025 (108–31 326) | 1372 ± 2659 (3–25 343) | P < 0.001 |
| Procedure success, n (%) | 568 (97.3) | 275 (98.2) | 293 (96.4) | n.s. |
| Parameter | Total (n = 584) | Before DRP implementation (n = 280) | After DRP implementation (n = 304) | Significance |
|---|---|---|---|---|
| Age, mean ± SD (years) | 70 ± 13 (17–94) | 69 ± 13 (23–94) | 71 ± 13 (17–91) | n.s. |
| Male gender, n (%) | 381 (65.2) | 181 (64.6) | 200 (65.8) | n.s. |
| Body mass index, mean ± SD (kg/m2) | 27.6 ± 5.5 (14.8–69.2) | 27.6 ± 5.2 (17.0–57.1) | 27.4 ± 5.8 (14.8–69.2) | n.s. |
| One-chamber pacemaker, n (%) | 53 (9.1) | 31 (11.1) | 22 (7.2) | n.s. |
| Two-chamber pacemaker, n (%) | 232 (39.7) | 104 (37.1) | 128 (42.1) | n.s. |
| One-chamber ICD, n (%) | 133 (22.8) | 71 (25.4) | 62 (20.4) | n.s. |
| Two-chamber ICD, n (%) | 35 (6.0) | 19 (6.8) | 16 (5.3) | n.s. |
| CRT (de novo), n (%) | 82 (14.0) | 39 (13.9) | 43 (14.1) | n.s. |
| CRT (upgrade), n (%) | 49 (8.3) | 16 (5.7) | 33 (10.9) | P = 0.025 |
| Oral anticoagulation, n (%) | 297 (50.9) | 132 (47.1) | 165 (54.3) | n.s. |
| Antiplatelet therapy, n (%) | 330 (56.5) | 166 (59.3) | 164 (53.9) | n.s. |
| Left ventricular ejection fraction, mean ± SD (%) | 43 ± 14.9 (5–70) | 44 ± 14.7 (15–66) | 43 ± 15.1 (5–70) | n.s. |
| NYHA class, mean ± SD (%) | 2.5 ± 2.4 (0–4) | 2.7 ± 3.6 (1–4) | 2.3 ± 0.7 (0–4) | n.s. |
| ASA class, mean ± SD (%) | 2.7 ± 0.6 (1–5) | 2.7 ± 0.5 (1–5) | 2.6 ± 0.6 (1–4) | n.s. |
| Procedure duration, mean ± SD (min) | 92 ± 52 (23–320) | 92 ± 52 (28–320) | 93 ± 52 (23–285) | n.s. |
| Fluroscopy duration, mean ± SD (min) | 13 ± 15 (0–86) | 13 ± 15 (0–84) | 13 ± 15 (0–86) | n.s. |
| Dose area product, mean ± SD (cGcm2) | 2517 ± 4136 (3–31 326) | 3792 ± 5025 (108–31 326) | 1372 ± 2659 (3–25 343) | P < 0.001 |
| Procedure success, n (%) | 568 (97.3) | 275 (98.2) | 293 (96.4) | n.s. |
AF, atrial fibrillation; ASA, American Society of Anesthesiologists; CRT, cardiac resynchronization therapy; COPD, chronic obstructive pulmonary disease; ICD, implantable cardioverter defibrillator; n.s., not significant; NYHA, New york heart association; SD, standard deviation.
The analysed procedures included 53 (9.1%) one-chamber pacemaker implantations, 232 (39.7%) two-chamber pacemaker implantations, 133 (22.8%) one-chamber ICD implantations, 35 (6.0%) two-chamber ICD implantations, 82 (14.0%) CRT de novo implantations and 49 (8.3%) CRT upgrades.
Procedures performed after implementation of the DRP showed an average reduction in the DAP of 64% (1372 ± 2659 vs. 3792 ± 5025 cGcm2, P < 0.001), while total fluoroscopy duration (13 ± 15 vs. 13 ± 15 min) and total procedural duration (93 ± 52 vs. 92 ± 52 min) were not prolonged (see Figures 1 and 2). Procedural success rates were not significantly different (97.3 vs. 98.2% P = 0.175). In no single case X-ray settings had to be adjusted due to insufficient visualization.
Dose area product before and after the dose reduction protocol according to the procedure type.
Fluoroscopy duration pre and after the dose reduction protocol according to the procedure type.
Procedures performed after implementation of the DRP were not associated with a higher complication rate. Complications were classified as major or minor, according to severity. Major complications include re-interventions within 6 weeks after implantation, local infections requiring re-intervention, Pocket hematomas with a haemoglobin drop of >3 g/dL or requiring re-intervention, transfusion or intensive care surveillance, implantation-related systemic infection or endocarditis, pericardial effusion requiring drainage, pneumothorax requiring drainage, pocket revisions due pain, dislocation, or generator-lead connection problems, and procedure-related death.
Minor complications included hematomas not categorized as major but requiring additional outpatient visits, wound infections managed conservatively, and pneumothoraces treated conservatively.
Table 2 summarizes major and minor complications for the different procedures before and after implementation of the protocol.
Complications
| Parameter | Before DRP implementation | After DRP implementation | Significance |
|---|---|---|---|
| Pacemaker (one-/two-chamber) | |||
| Complication, minor, n (%) | 7 (5.3) | 7 (4.7) | n.s. |
| Complication, major, n (%) | 11 (8.3) | 9 (6) | n.s. |
| ICD (one-/two-chamber) | |||
| Complication, minor, n (%) | 6 (6.7) | 4 (5.2) | n.s. |
| Complication, major, n (%) | 5 (5.6) | 3 (3.8) | n.s. |
| CRT (de novo/upgrade) | |||
| Complication, minor, n (%) | 13 (23.6) | 14 (18.4) | n.s. |
| Complication, major, n (%) | 4 (7.3) | 6 (7.9) | n.s. |
| Parameter | Before DRP implementation | After DRP implementation | Significance |
|---|---|---|---|
| Pacemaker (one-/two-chamber) | |||
| Complication, minor, n (%) | 7 (5.3) | 7 (4.7) | n.s. |
| Complication, major, n (%) | 11 (8.3) | 9 (6) | n.s. |
| ICD (one-/two-chamber) | |||
| Complication, minor, n (%) | 6 (6.7) | 4 (5.2) | n.s. |
| Complication, major, n (%) | 5 (5.6) | 3 (3.8) | n.s. |
| CRT (de novo/upgrade) | |||
| Complication, minor, n (%) | 13 (23.6) | 14 (18.4) | n.s. |
| Complication, major, n (%) | 4 (7.3) | 6 (7.9) | n.s. |
CRT, cardiac resynchronization therapy; ICD, implantable cardioverter defibrillator; SD, standard deviation.
Complications
| Parameter | Before DRP implementation | After DRP implementation | Significance |
|---|---|---|---|
| Pacemaker (one-/two-chamber) | |||
| Complication, minor, n (%) | 7 (5.3) | 7 (4.7) | n.s. |
| Complication, major, n (%) | 11 (8.3) | 9 (6) | n.s. |
| ICD (one-/two-chamber) | |||
| Complication, minor, n (%) | 6 (6.7) | 4 (5.2) | n.s. |
| Complication, major, n (%) | 5 (5.6) | 3 (3.8) | n.s. |
| CRT (de novo/upgrade) | |||
| Complication, minor, n (%) | 13 (23.6) | 14 (18.4) | n.s. |
| Complication, major, n (%) | 4 (7.3) | 6 (7.9) | n.s. |
| Parameter | Before DRP implementation | After DRP implementation | Significance |
|---|---|---|---|
| Pacemaker (one-/two-chamber) | |||
| Complication, minor, n (%) | 7 (5.3) | 7 (4.7) | n.s. |
| Complication, major, n (%) | 11 (8.3) | 9 (6) | n.s. |
| ICD (one-/two-chamber) | |||
| Complication, minor, n (%) | 6 (6.7) | 4 (5.2) | n.s. |
| Complication, major, n (%) | 5 (5.6) | 3 (3.8) | n.s. |
| CRT (de novo/upgrade) | |||
| Complication, minor, n (%) | 13 (23.6) | 14 (18.4) | n.s. |
| Complication, major, n (%) | 4 (7.3) | 6 (7.9) | n.s. |
CRT, cardiac resynchronization therapy; ICD, implantable cardioverter defibrillator; SD, standard deviation.
Discussion
Fluoroscopy is still an essential tool for most CIED implantations. To avoid potentially fatal complications caused by radiation, patient dose must be as low as possible. As shielding is difficult to achieve during these procedures, reducing the patient dose is at the same time the most effective way to reduce direct and scattered exposure of the operator.
Three major factors influence the dose delivered to the patient: tube settings of the X-ray equipment, patient weight,7 and fluoroscopy time.8 Of those three factors, optimizing the X-ray settings represents the most modifiable parameter to achieve significant reductions of the patient and operator dose.
Fluoroscopy system settings allow a reduction in radiation while preserving acceptable image quality. An important instantly modifiable parameter is the frame rate, as all commercially available systems allow different frame rate settings. There is a linear relationship between the frame rate and the radiation dose,2 so the lowest possible settings should be used. Although, according to the results of the European Heart Rhythm Association Survey about the use of fluoroscopy in clinical electrophysiology and CIED implantations in Europe, only 16% of the participating centres used a frame rate of less than 6 frames per second (FPS). After the DRP implementation 4 FPS were used as a standard for all CIED implantations. No single case was recorded where FPS had to be upregulated due to insufficient visualization.
Apart from the frame-rate reduction, a ‘low dose’ protocol was established together with the manufacturer of the X-ray system, which included optimized image processing and exposure system settings to enable dose reduction.
After the DRP was established a total dose reduction (measured as DAP) of 64% was achieved. The results were similar for all device implantations ranging from single pacemakers to CRT-D devices. These results are in line with previous studies, showing similar effects with DRPs for coronary angiograms9 or during EP ablation procedures.10
The additional focus of our study was to prove that safety and efficacy of the procedures are not altered after the new protocol was introduced. The rate of successful implantations was not different between the pre- and post-DRP groups and X-ray settings had never to be adjusted due to insufficient image quality. Complication rates did not increase after implementation of the DRP and were in line with the rate of complications observed in large registries.11,12
Limitations
This study has several limitations. It is designed as a retrospective, single-centre study, and the interventions were performed by a small number of (experienced) operators. Secondly establishing a DRP will lead to more radiation awareness. This is certainly an additional positive effect of such an effort. In our study, although fluoroscopy time did not decrease after implementation of the protocol, improvements in collimation or angulation may be in part responsible for the observed effects.
Conclusion
The DRP was effective in reducing the mean DAP by 64% over the various types of CIED implantations. Radiation settings did not have to be modified during the procedure due to insufficient image quality and the rate of successful implantations and complications was not different after the DRP was established. These data should encourage the use of similar protocols when CIED implantations are performed.
Conflict of interest: none declared.
