“Real life” longevity of implantable cardioverter‐defibrillator devices

Abstract

Background

Manufacturers of implantable cardioverter‐defibrillators (ICDs) promise a 5‐ to 9‐year projected longevity; however, real‐life data indicate otherwise. The aim of the present study was to assess ICD longevity among 685 consecutive patients over the last 20 years.

Hypothesis

Real‐life longevity of ICDs may differ from that stated by the manufacturers.

Methods

The study included 601 men and 84 women (mean age, 63.1 ± 13.3 years). The underlying disease was coronary (n = 396) or valvular (n = 15) disease, cardiomyopathy (n = 220), or electrical disease (n = 54). The mean ejection fraction was 35%. Devices were implanted for secondary (n = 562) or primary (n = 123) prevention. Single‐ (n = 292) or dual‐chamber (n = 269) or cardiac resynchronization therapy (CRT) devices (n = 124) were implanted in the abdomen (n = 17) or chest (n = 668).

Results

Over 20 years, ICD pulse generator replacements were performed in 238 patients (209 men; age 63.7 ± 13.9 years; ejection fraction, 37.7% ± 14.0%) who had an ICD for secondary (n = 210) or primary (n = 28) prevention. The mean ICD longevity was 58.3 ± 18.7 months. In 20 (8.4%) patients, devices exhibited premature battery depletion within 36 months. Most (94%) patients had none, minor, or modest use of ICD therapy. Longevity was longest for single‐chamber devices and shortest for CRT devices. Latest‐generation devices replaced over the second decade lasted longer compared with devices replaced during the first decade. When analyzed by manufacturer, Medtronic devices appeared to have longer longevity by 13 to 18 months.

Conclusions

ICDs continue to have limited longevity of 4.9 ± 1.6 years, and 8% demonstrate premature battery depletion by 3 years. CRT devices have the shortest longevity (mean, 3.8 years) by 13 to 17 months, compared with other ICD devices. These findings have important implications, particularly in view of the high expense involved with this type of electrical therapy.

1. INTRODUCTION

Significant progress and great technological strides have been accomplished in the electrical therapy of malignant ventricular arrhythmias and prevention of sudden cardiac death with the advent of the implantable cardioverter‐defibrillator (ICD).1, 2, 3, 4, 5, 6 However, this effective electrical approach to sudden cardiac death still entails a very high cost.7 Longevity of the ICD devices is an extremely important parameter that has to be factored into the equation of cost‐effectiveness of this therapy.7 All the technical advances, including downsized active‐shell devices with better integrated leads, have led to a significant decrease in cost but not to a similar prolongation of the life span of ICD devices.8, 9 In most studies the technical advantages of the new devices are emphasized, but the equally important aspect of device longevity has not been adequately addressed.9

Manufacturers of the newer‐generation ICD models promise a 5‐ to 9‐year projected longevity.10 There have been a few previous studies reporting on the longevity of newer ICD systems that practically refute this industry claim.11, 12, 13 We have been prospectively collecting data from our own experience with device replacements over the past 20 years, and the aim of the present study was to assess the pulse generator longevity among 685 consecutive patients who received an ICD over the last 20 years.

2. METHODS

2.1. Patients

The study included all ICD device replacements that were performed among 685 patients followed up in our outpatient ICD clinics over the last 20 years who had initially received a transvenous ICD in our institutions (Table 1). These were 601 men and 84 women, mean age 63.1 ± 13.3 years (range, 12 to 88 years), who presented with sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or syncope with inducible ventricular tachycardia (n = 562), or with low left ventricular ejection fraction (LVEF; n = 123). The underlying heart disease was coronary artery disease in 396 patients, cardiomyopathy in 220, valvular disease in 15, and 54 patients had primary electrical disease. The LVEF averaged 35.3% ± 13.2%. All patients underwent cardiac catheterization to define coronary anatomy, and in the early years, many of them were subsequently submitted to electrophysiological studies. Many of those with inducible monomorphic sustained VT were also submitted to electropharmacological testing using amiodarone loading with 1200 to 1800 mg daily for 10 days. In the later days, published respective guidelines were followed and an ICD was implanted for clinical VT/VF or for primary prevention for low (<35%) LVEF without necessarily performing an electrophysiology study. For the implantation of the ICD system, informed written consent was obtained from all patients.

Table 1.

Clinical and procedural data in all ICD patients and in the replacement group

	Whole ICD Group	ICD Replacement Group	P Value
Patients, n	685	238
M/F, %	601/84	209/29
Mean age, y	63.1 ± 13.3	63.7 ± 13.9	0.55
Secondary prevention	562 (82)	210 (88.2)	0.025
Primary prevention	123 (18)	28 (11.8)	0.025
CAD	396 (57.8)	135 (56.7)	0.71
Cardiomyopathy	220 (32.1)	75 (31.5)	0.86
Valvular heart disease	15 (2.2)	3 (1.3)	0.051
Primary electrical disease	54 (7.9)	25 (10.5)	0.22
LVEF, %	35.3 ± 13.2	37.7 ± 14.0	0.013
Successful procedures, %	100	100	NS

Abbreviations: CAD, coronary artery disease; F, female; ICD, implantable cardioverter‐defibrillator; LVEF, left ventricular ejection fraction; M, male; NS, not significant; SD, standard deviation.

Data are presented as n (%) or mean ± SD unless otherwise noted.

2.2. Initial implant procedure

The transvenous ICD lead system was introduced via the left cephalic or occasionally the left subclavian vein, and under fluoroscopy it was positioned usually at the right ventricular apex or at the septum or outflow tract. After obtaining satisfactory intraoperative electrical measurements (pacing and sensing thresholds), the lead was secured in place to the muscle. Then, defibrillation threshold testing was performed with induction of VF initially with use of the external cardioverter‐defibrillator support device and later with use of the ICD device by means of T‐wave shocking or use of alternating current. Defibrillation was initially attempted after 10 to 12 seconds of VF with use of a 15‐joule shock. Subsequently, a step‐down technique was followed down to 5 joules. This was later modified to include only 1 test at 15 joules.

All implant procedures were performed in the electrophysiology laboratory by electrophysiologists without surgical assistance, using techniques that have been previously described.4, 5, 6 Prophylactic antibiotic treatment was routinely employed. Initially, early on in the series general anesthesia was used for very few patients, but subsequently, in the majority of patients, the procedures were performed under local anesthesia combined with deep sedation (using midazolam and propofol) during defibrillation threshold testing. Again, early in the series with bigger ICD devices, the pulse generator was implanted in the left paraumbilical space (12 patients), but the majority of implants were pectoral, either in the subfascial area or in a smaller percentage in the subpectoral area. When an adequate threshold was obtained, the ICD device was appropriately programmed and implanted in the pocket.

2.3. Clinical follow‐up

At 24 to 48 hours postoperatively, in the early days, patients were submitted to predischarge testing of the ICD system, which subsequently was forgone. Follow‐up for all patients was arranged at the ICD clinic initially at 3 months and subsequently every 6 months. During follow‐up and throughout the lifetime of each device, minor ICD device use was defined as delivery of electrical therapy by the device in the form of anti‐tachycardia pacing (ATP) and/or 1 shock; modest ICD use was defined as delivery of 2 to 5 shocks, and ample ICD use was defined as delivery of >6 shocks; electrical storm was defined as delivery of >3 shocks in 1 day.

2.4. Pulse generator replacement

When the specific device elective replacement indicator (ERI) was reached, the patient was scheduled to have the pulse generator replaced in the electrophysiology laboratory. The patient was admitted either on the previous day or in the morning on the same day that the procedure was scheduled. Prior to the procedure, prophylactic antibiotics were used, including intravenous cefazolin or vancomycin administered 30 minutes or 1 hour before the procedure and continued for 48 hours, followed after discharge by oral oxacillin or combined amoxicillin plus clavulanic acid for 3 days.

All replacement procedures were performed under local anesthesia combined with deep sedation, with brief use of midazolam plus propofol during VF induction and device testing. After the lead(s) were disconnected from the old device, pacing and sensing thresholds were measured. This was followed by induction of VF and subsequent defibrillation when the new ICD device was in place, performed in the majority of patients.

2.5. Statistical analysis

Data are presented as mean ± SD. Comparisons were made using the Student unpaired t test for quantitative data and χ² analysis and the z‐statistic for qualitative and proportional data. Analysis of variance with Bonferroni correction was used to compare data for >2 groups. Multiple regression analysis was used to analyze the relation of longevity to multiple variables (age, sex, LVEF, underlying structural heart disease, device use, type and generation of ICD device, and manufacturer). A Kaplan‐Meier survival curve analysis was used to compare longevity outcomes in different groups, and differences between groups were analyzed with the log‐rank test. SPSS statistics software version 23 (IBM Corp., Armonk, NY) and MedCalc version 16.8.4 statistical package (MedCalc, Ostend, Belgium) were employed. A P value <0.05 was considered significant.

3. RESULTS

3.1. Initial implant procedures

Implantation was performed under general anesthesia in 42 patients; local anesthesia combined with deep sedation was used in all the other patients. There were 19 abdominal implants, whereas in the remainder of cases, ICDs were placed in the pectoral region. In 18 patients with inadequate subcutaneous tissue, subpectoral implants were performed using a single‐incision technique,5 whereas in all other patients the device was implanted in the prepectoral (subfascial) area.

A single‐coil lead ICD system was used in 33 patients; one of them received a VDD single‐coil ICD lead. A double‐coil ICD system was employed in all other patients. A single‐chamber ICD was implanted in 290 patients and a dual‐chamber ICD in 271 patients; a biventricular ICD system (CRT‐D) was implanted in 124 patients.

All systems were initially successfully implanted in all patients. Purely transvenous ICD implants were feasible in all patients. Active shell devices were employed in the majority of patients. Intraoperative measurements yielded very satisfactory results, with relatively low (<15 joules) defibrillation thresholds.

During the postoperative course, 1 patient developed pneumothorax that resolved spontaneously. In another patient, lead insulation break was noted during predischarge testing that required re‐operation on the third postoperative day for lead replacement. There were no operative deaths in this series. A total of 307 patients were implanted in the first 10 years and 378 in the last 10 years (a ~23% increase in the implantation rate).

3.2. Pulse generator replacement

Over 20 years, ICD pulse generator replacement was performed in 238 patients (34.7%; Table 1). Of these 238 patients, 19 had the device initially implanted in an abdominal pocket, 217 had their device implanted in a subcutaneous pectoral pocket, and 2 patients had a submuscular implant in the pectoral region. The study group included 209 men and 29 women, mean age 63.7 ± 13.9 years, who had the ICD device initially implanted for secondary (n = 210) or primary (n = 28) prevention. The underlying disease was coronary artery disease in 135 patients, cardiomyopathy in 75 patients, valvular heart disease in 3 patients, and primary electrical disease in 25 patients. The mean LVEF was 37.7% ± 14.0%.

3.3. Device longevity

The mean device longevity for all 238 pulse generator replacements was 58.3 ± 18.7 months (range, 7–121 months; Table 2). Early (<3 years) battery depletion occurred in 20 (8.4%) patients. The newer‐generation devices replaced during the second decade (n = 167) of the study period lasted longer compared with the older devices (n = 71) of the first decade (60.4 ± 18.8 months vs 53.5 ± 17.5 months; P = 0.009; Figure 1). Among the 3 different types of ICD devices (ICD VR, ICD DR, CRT‐D), the CRT pulse generators had the shortest longevity (46.3 ± 10.0 months; log‐rank P < 0.0001; Table 2, Figure 2). With regard to devices from different manufacturers, the Medtronic devices outlasted all the others (70.5 ± 21.6 months; log‐rank P < 0.0001; Table 2, Figure 3). According to multiple regression analysis, independent predictors of shorter longevity were device type (CRT‐D; P = 0.009), older‐generation devices (replaced in the first decade; P = 0.002), and devices implanted in patients with lower LVEF (P = 0.013). During follow‐up, 14 (5.9%) patients finally succumbed to pump failure.

Table 2.

Longevity of 238 replaced ICD devices

Devices	No.	Longevity, mo
All devices	238	58.3 ± 18.7
Prematurely depleted (<3 years)	20	30.5 ± 7.5
First‐decade replacements	71	53.5 ± 17.5
Second‐decade replacements	167	60.4 ± 18.8
Single‐chamber devices (ICD VR)	91	63.6 ± 21.6
Dual‐chamber devices (ICD DR)	101	59.0 ± 16.3
CRT‐D	45	46.3 ± 10.0
Device manufacturers
Medtronic	61	70.5 ± 21.6
Boston Scientific	58	58.3 ± 16.3
St. Jude	85	51.7 ± 15.4
Biotronik	28	51.9 ± 13.5
ELA Medical	5	57.4 ± 12.5

Abbreviations: CRT‐D, cardiac resynchronization therapy‐defibrillator device; ICD, implantable cardioverter‐defibrillator; ICD DR, dual‐chamber device; ICD VR, single‐chamber device; mo, months.

Figure 1.

Longevity was significantly shorter (mean, ~4.5 years) for devices replaced during the first decade (n = 71) compared with those replaced in the second decade (n = 167; mean ~5 years) of the time period in this series. Abbreviations: mos, months.

Figure 2.

Kaplan‐Meier device survival curves to pulse generator replacement for single‐chamber (ICD VR), dual‐chamber (ICD DR), and CRT‐D devices. Abbreviations: CRT‐D, cardiac resynchronization therapy device; ICD, implantable cardioverter‐defibrillator; ICD DR, dual‐chamber ICD device; ICD VR, single‐chamber ICD device.

Figure 3.

Kaplan‐Meier curves of device longevity for devices of different manufacturers. Abbreviations: Bio, Biotronik; Bo, Boston Scientific; E, ELA Medical; M, Medtronic; SJ, St. Jude Medical.

3.4. ICD‐delivered electrical therapy

All but 14 patients had none or minor (ATP and/or 1 shock) or modest use (ATP and/or 2–5 shocks) of the ICD device electrical therapy. A total of 14 patients had ample ICD use with delivery of 10 to 50 ICD shocks throughout the life span of the device. Electrical storm (>3 shocks clustered within 24 hours) occurred in 6 of these 14 patients, with 5 of them finally managed successfully with performance of radiofrequency ablation of the triggering VT. Interestingly, device longevity was apparently affected only in 1 patient, with an electrical storm considered responsible for premature battery depletion at 31 months. In the other 13 patients with ample ICD use, device longevity ranged from 45 to 121 months.

3.5. Follow‐up of patients with nonreplaced devices

Follow‐up of the 447 patients who had not had their pulse generator replaced as it had not reached the ERI yet, ranged from 6 to 108 months (mean, 25.7 ± 16.1 months). At the latest follow‐up, there were 12 patients whose devices had not reached ERI at 5 years, 3 patients at 6 years, 1 patient at 7 years, and 1 patient at 9 years. Among these 17 patients with a device life span >5 years, 11 had been implanted in the first decade and 6 during the second decade. During the follow‐up period of the whole group, 24 patients succumbed to pump failure (n = 22) or sudden death (n = 2).

4. DISCUSSION

In the present series of 685 patients receiving an ICD device over the last 20 years, pulse generator replacement was needed in 238 patients (~35%). Premature (<3 years) battery depletion occurred in 20 (8.4%) of 238 patients among those having device exchange or 2.9% among all ICD patients, which is a higher percentage compared with the 2% explantation rate for device malfunction reported to the US Food and Drug Administration according to a 2006 publication of a very large series of ICD devices.14 Fortunately, no deaths occurred as a result of this type of malfunction in our series, compared with a 0.37% death rate reported in the FDA series.14 Apparently, grave problems may arise with unpredictable and abrupt battery depletion, as has been reported by other investigators, who recommend more frequent (monthly) follow‐up or even battery replacement for devices reaching a near‐ERI voltage if patients are pacemaker‐dependent, have received device therapies, or have high pacing thresholds.15

Device longevity averaged 58.3 ± 18.7 months, and there was only minor to modest use of the devices throughout their life span in the majority of patients (94%). Even among those 14 patients with ample use of ICD electrical therapy or an electrical storm, only 1 was apparently affected and presented premature battery depletion. Although reports of longevity have indicated a progressive increase of the life span of ICD devices over the years, from a mean of 19 months in 1980 to 48 months in 200916 to 65 months in 2015,17 there is still room for improvement, as this is quite an expensive therapy and patient and physician expectations run high for a more satisfactory performance of these devices, a crucial determinant of cost‐efficacy of ICD therapy.18 Reducing the frequency of generator replacements would also reduce the frequency of important complications, such as device infection, and their consequent costs.19, 20, 21 Real‐life longevity is definitely sharply shorter compared with the industry‐projected longevity, which has always overestimated ICD device performance.10, 16, 22

In the present study, contemporary devices performed modestly better in comparison with earlier devices by about 7 months, a finding that is similar to previous reports.12, 23 Our analysis of the group of patients who had not yet had their devices replaced as they had not yet reached ERI at the latest follow‐up did not allow for any further firm conclusion about the life span of the newer‐generation devices; only 17 patients had devices not reaching ERI at 6 to 9 years. However, this may only relate to the limited duration of the follow‐up period. Great variability has also been documented in this and other series for devices of different manufacturers.17, 23, 24 Battery structure and design differ among the various types of ICD devices, and this may well explain the reason that ICD generator longevity has been variable among different manufacturers.25 In prior series, Medtronic devices were shown to have a longer life span when compared with those of Boston Scientific (Guidant) or St. Jude Medical,16, 17, 26 but other studies showed that Boston Scientific devices outperformed the devices of other manufacturers.13, 23, 24 In agreement with these previous studies, the present study also found that ICD device longevity varies among devices of different manufacturers. We found significantly better longevity for the Medtronic devices compared with almost all other devices. Kaplan‐Meier analysis of the time to battery depletion also revealed a much shorter longevity for the CRT‐D devices by 13 to 17 months compared with dual‐chamber (ICD DR) and single‐chamber (ICD VR) devices. Shorter CRT‐D device longevity has been reported in other series as well, attributed in part to the need for constant pacing.13, 27 Indeed, for CRT to be effective, constant left ventricular or biventricular pacing is a prerequisite to ensure left ventricular resynchronization.28 According to a recent study in a large cohort of 1399 patients treated with CRT‐D, device replacement for battery depletion proved to be a significant cost driver, whereby improved longevity observed with newer‐generation devices reduced the therapy cost.18 Furthermore, differences were also observed among CRT‐D systems from different manufacturers.

In essence, our results showed that in current clinical practice the real‐life longevity of ICD systems averaged only about 5 years and CRT‐D devices a little less than 4 years. Thus, device longevity still remains the weak link of ICD technology and lifesaving therapy. Whether this is a result of striking a balance between device miniaturization and longevity remains to be seen.29 In this regard, it has become obvious that prolonged device longevity is much more important than smaller generator size, and a call has been voiced by both patients and physicians for device batteries with larger capacities.30, 31, 32

4.1. Study limitations

A limitation of the present study is the lack of information regarding the longevity of the very latest devices that were recently implanted and have not reached the ERI; hopefully they may last longer than the devices replaced in this series. Thus, our results may not apply to these newer devices. In addition, data on parameters that might have affected device longevity, such as programmed pacing output and percentage of pacing, were not collected in this report. Although we have data on minor or modest device usage in the majority of patients, this parameter did not appear to have had an impact on battery life. Also, some devices were poorly represented in this series (eg, ELA Medical), thus not permitting an estimate of their life span. Finally, it should be pointed out that in our series, these were primarily secondary prevention devices, which tend to lead to more therapies that may adversely affect battery longevity. Nevertheless, only minor to modest use of electrical therapies of the devices occurred throughout their life span in the majority of patients (94%), thus not really accounting for or adequately explaining the observed suboptimal longevity in this series.

5. CONCLUSION

The present data on ICD longevity from our prospective analysis of 238 patients having pulse generator replacement among 685 consecutive patients who received an ICD over the last 20 years indicate that ICDs continue to have limited longevity of 4.9 ± 1.6 years, and a worrisome percentage (~8%) of these devices still demonstrate premature battery depletion by 3 years, thus falling short of the 3‐year manufacturer's warranty. CRT devices have the shortest longevity (mean, 3.8 years) by 13 to 17 months, compared with other ICD devices. These shortcomings may not be applicable to current device generators, which have not reached ERI yet, as latest‐generation devices do appear to have longer longevity. Significant differences exist among systems from different manufacturers.

All the technical advances accomplished over the years in the ICD devices, including device downsizing and better integrated leads, have led to significant improvement of device function and patient convenience but not to a similar prolongation of the life span of ICD devices. In most studies, the technical advantages of the new devices are emphasized, but the equally important aspect of device longevity has not been adequately addressed. Furthermore, manufacturers of the newer‐generation ICD models promise a 5‐ to 9‐year projected longevity. However, there have been a few previous studies reporting on the longevity of newer ICD systems that practically refute this industry claim.

These findings of limited “real‐life” ICD longevity and worrisome (8%) percentage of premature battery depletion, together with the finding of a weakest link of CRT technology, have important implications, particularly in view of the high importance and increased expense involved with this type of electrical therapy. Such compelling findings may urge manufacturers to act on implementing improvements in ICD battery life span.

Conflicts of interest

The authors declare no potential conflicts of interest.

Manolis AS, Maounis T, Koulouris S and Vassilikos V. “Real life” longevity of implantable cardioverter‐defibrillator devices. Clin Cardiol. 2017;40:759–764. 10.1002/clc.22729