Device Use Patterns and Clinical Outcome of Implantable Cardioverter Defibrillator Patients with Moderate and Severe Impairment of Left Ventricular Function

The beneficial effects of implanted cardioverter defibrillator (ICD) therapy in patients with malignant ventricular tachyarrhythmias and variable degrees of left ventricular (LV) dysfunction are debated. ICD use and patient survival were examined in 128 patients with malignant ventricular arrhythmias and moderate or severe LV dys function. Group I included 64 patients with moderate LV dysfunction (LV ejection fraction of > 30%) and group H, 64 patients with severe LV dysfunction (LV ejection fracfion of ≤ 30%). Follow-up period ranged from 1 to 78 months. The two groups were similar in age, incidence of coronary artery disease and presenting arrhythmia. The mean LV ejection fraction in group I was 44%± 8% and group II was 22%± 5% (P < 0.0001). At 4 years of follow-up, 66% of patients from group I and 62% from group II (P = NS) had ICD activation for presumed ventricular tachyarrhythmia. Survival was calculated using actuarial analysis. Arrhythmic or sudden death mortality at 4 years of follow-up was 4% in group I and 7% in group II (P = NS). Cardiac mortality was for group I, 7% (P < 0.05), 12% (fP < 0,01), 15% (P < 0.01), and 15% (P < 0.01) for follow-up years 1, 2, 3, and 4, respectively. For group II, cardiac mortality was 27%, 36%, 41%, and 41% for follow-up years for 1, 2, 3, and 4, respectively. The majority of cardiac deaths in both groups was observed in the first 2 years of follow-up. However, in both groups, cardiac mortality was comparable in patients who did (users) and did not (nonusers) experience appropriate ICD shocks. Thus, the incidence of long-term ICD use is comparable in patients with moderate and severe LV dysfunction. Cardiac mortality is higher in patients with severe LV dysfunction in the first 4 years of follow-up irrespective of device use. The comparable long-term clinical outcome of ICD users and non users in patients with moderate or severe LV dysfunction can be related to elimination of arrhythmic mortality. Long-term patient survival in ICD recipients with severe LV dysfunction remains substantial even at 4 years of follow-up.     

Inability of the Signal-Averaged Electrocardiogram to Determine Risk of Arrhythmia Recurrence in Patients with Implantable Cardioverter Defibrillators

Signal-averaged electrocardiography has been used to identify patients at risk for arrhythmic death after myocardial infarction. Since patients with implantable cardioverter defibrillators (ICDs) are at high risk for arrhythmic events, they should also be expected to have a high incidence of abnormal signal-averaged electrocardiograms (SAECGs). However, whether the SAECG can discriminate patients who will have arrhythmia recurrence and receive appropriate ICD shocks from those who will have no recurrence and no shocks is unknown. This study examines the usefulness of the SAECG to separate appropriate users from non-users of the ICD. Fifty patients with ICDs participated in this study. Those who received a shock preceded by symptoms, a shock without preceding symptoms but with electrocardiographic documentation of ventricular fibrillation or ventricular tachycardia, or a shock while asleep were classified as ICD users. All other patients were classified as nonusers. The SAECG was classified as normal if the QRS duration on the standard electrocardiogram was less than or equal to 110 msec and if the total filtered QRS duration was less than 120 msec, the root-mean square voltage of the terminal 40 msec was greater than 25 muV, and the terminal low amplitude signal duration measured less than 38 msec. The SAECG was classified as abnormal if the QRS duration on the standard electrocardiogram was less than or equal to 110 msec and any one of these three criteria were outside the "normal range." The SAECG was classified as indeterminate if the QRS duration on the standard 12-lead electrocardiogram was greater than 110 msec. For the entire group of 50 patients, 8 (16%), 12 (24%), and 30 (60%) had normal, abnormal, and indeterminate SAECGs, respectively. Of the 22 ICD users, 1 (5%), 5 (23%), and 16 (73%) patients had normal, abnormal, and indeterminate SAECGs, respectively. Of the 28 ICD nonusers, 7 (25%), 7 (25%), and 14 (50%) patients had normal, abnormal, and indeterminate SAECGs, respectively. ICD users had lower left ventricular ejection fractions (P = 0.0002), a higher incidence of ventricular tachycardia (P = 0.04), prior exposure to a greater number of antiarrhythmic drugs (P = 0.04), and a lower likelihood for survival (P = 0.02) compared to the ICD nonusers. There was no statistically significant difference between the ICD users and nonusers as stratified by SAECG classification regardless of whether or not the interminate studies were included or excluded from the analysis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ventricular Pacing Induced Ventricular Tachycardia in Patients with Implantable Cardioverter Defibrillators

Appropriately timed noncompetitive ventricular pacing potentially may initiate ventricular tachycardia in patients prone to these arrhythmias. The combination of bradycardia pacing and stored electrograms in a currently available cardioverter defibrillator provides an opportunity to evaluate the occurrence of such pacing induced ventricular tachycardia. During a surveillance period of 18.7 ± 11.4 months, stored electrograms documented 302 episodes of ventricular tachycardia in 77 patients. Five patients (6.5%) demonstrated 25 episodes (1–16 per patient) of ventricular tachycardia that were immediately preceded by an appropriately paced ventricular beat (8.3% of all episodes of ventricular tachycardia). All five patients had prior myocardial infarctions and a history of monomorphic ventricular tachycardia occurring both spontaneously and in response to programmed electrical stimulation. Antitachycardia pacing terminated pacing induced ventricular tachycardia in 22 episodes; in one episode antitachycardia pacing accelerated ventricular tachycardia. In two cases shock therapy was aborted for nonsustained ventricular tachycardia. We conclude that, in selected postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter defibrillators, appropriately timed ventricular pacing may induce ventricular tachycardia.     

Predictors of Device Activation for Ventricular Arrhythmias and Survival in Patients with Implantable Pacemakers/Defibrillators

Predictors of survival and arrhythmia recurrence for patients with implanted defibrillators have been reported but patients with sustained, well-tolerated ventricular tachycardia were often excluded from these trials. Arrhythmia recurrence and survival in populations including these patients have been less well studied. The purpose of the present study was to examine predictors of spontaneous ventricular arrhythmias and mortality in patients who received a tiered therapy antitachycardia pacemaker/defibrillator for ventricular tachycardia, fibrillation, or both. Three hundred thirty-seven patients who received a Ventritex CADENCE® tiered therapy antitachycardia device at one of 19 participating centers between July 11, 1989 and March 4, 1991 are included in this retrospective analysis. Diagnostic summary data and stored electrograms telemetered from the implanted device were assessed to determine characteristics of recurrent arrhythmias. Mean follow-up was 360 ± 10 (SEM) days. Thirty-three patients died during follow-up. At least one recurrent ventricular arrhythmia was observed in 205 patients (61 %). A total of 7,539 episodes were observed with a mean of 37 ± 5 per patient. Patients with recurrent ventricular arrhythmias were slightly but significantly older (64 ± 0.7 vs 59 ± 1.2 years; P < 0.001) but were not distinguished by gender or underlying structural disease. Patients whose presenting arrhythmia was monomorphic ventricular tachycardia were more likely to experience recurrent ventricular arrhythmias (69% recurrence rate) than patients presenting with ventricular fibrillation or polymorphic ventricular tachycardia (46% recurrence rate; P < 0.001). Cycle length of spontaneous tachycardia was also a predictor of arrhythmia recurrence. Patients having slower ventricular arrhythmias were less likely to remain recurrence free. Mean left ventricular ejection fraction was similar for patients with and without recurrences. Younger age and absence of arrhythmia recurrence but not presenting arrhythmia were predictors of survival. We conclude that age and presentation with monomorphic ventricular tachycardia are important predictors of arrhythmia recurrence for this patient population. Exclusion of patients with monomorphic ventricular tachycardia underestimates the rate of recurrent ventricular arrhythmias and utilization of device therapy.     

Gross and Microscopic Changes Associated with a Nonthoracotomy Implantable Cardioverter Defibrillator

The pathology associated with an invesrigational transvenous defibriliating and sensing lead is described. The lead system had delivered a total of 865 J from the time of implantation to the time of patient death from a noncardiac cause 7 months after implantation and 1 month after his last defibrillator shock. There was mild, superficial fibrous thickening on the endothelial surface of the superior vena cava adjacent to the proximal spring electrode, which did not extend into the vessel wall. The distal portion of endocardial lead was embedded in the interventricular septum near the apex of the right ventricle, surrounded by fibrous thickening, and partially covered by endocardial tissue. Microscopically, there was a thick bed of fibrous connective tissue surrounding the lead with extensive interstitial fibrous connective tissue radiating into the adjacent myocardium. Since this pattern is different from the more generalized fibrotic scarring produced by myocardial infarction, we speculate that the mechanism for the observed interstitial fibrosis is replacement fibrosis following acute myocyte injury that resulted from prior defibrillator shocks and possibly from the trauma produced by the lead compressing adjacent myocardium during systole. Potential effects on device efficacy of these fibrotic changes at the bioelectric interface include their representing a new arrhythmia substrate, the possibility that fibrosis could increase both defibrillation and pacing thresholds, and that the inflammatory reaction may cause deterioration of intracardiac electrograms and interfere with sensing and tachycardia recognition.     

Results of Delivered Therapy for VT or VF in Patients with Third-Generation Implantable Cardioverter Defibrillators

Third-generation implantable cardioverter defibrillators (ICDs) offer tiered therapy and can provide significant advantage in the management of patients with life-threatening arrhythmias. Three different types of ICDs were implanted in 21 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia presentation was VT(76%), VF(10%), or both (14%). The mean left ventricular ejection fraction for the group was 32.4 ± 7%. No surgical mortality occurred. Prior to discharge individual EPS determined the final programmed settings of the ICDs. During a mean follow-up of 13 ± 1.4 months (range 2–20) the overall patient survival was 85.7%. No sudden arrhythmic or cardiac death occurred. Twenty of 21 patients (95%) received therapy by their device. In 14 patients (67%) antitachycardia pacing (A TP) was programmed "on," 13 of which was self-adaptative autodecremental mode. There were 247 VT episodes, 231 of which were subjected to ATP with 97% success and 3% acceleration or failure. Low energy shocks reverted all other VT episodes. VF episodes were successfully reverted by a single shock (93%), two shocks (6%), or three shocks (1 %). We conclude that ATP therapy of VT is successful in the large majority of episodes with rare failures, and that VF episodes are generally terminated by a single ICD shock.     

The Role of Implantable Cardioverter Defibrillators in Non VT/VF Sudden Deaths

Implantable cardioverter defibrillator (ICD) therapy has been an impressive success in preventing sudden cardiac death (SCD). Electrocardiographic documentation of SCD in ICD patients has been rare, but usually arrhythmias other than ventricular tachycardia/ventricular fibrillation (VT/VF; asystole and electromechanical dissociation [EMD]) have been implicated. This raises the question whether backup bradycardia pacing can prevent deaths due to asystole and EMD in such patients. We studied the outcome of 88 patients with permanent bradycardia pacemakers and compared them to 500 consecutive nonpacemaker patient controls, sustaining out-of-hospital cardiac arrest and undergoing resuscitation by paramedics. Mean age of the pacemaker patients was 73.5 ± 10.3 years and 64% males, compared to mean age of 68.2 ± 6.7 years and 67% males in the control group. Overall success of resuscitation and survival rates were similar. When the documented rhythm was VT/VF or asystole there were no differences in resuscitation or survival rates for the pacemaker or nonpacemaker patients. However, resuscitation rate was significantly higher in pacemaker patients than nonpacemaker patients with EMD: 47% versus 20% ( P < 0.03). For EMD, survival rate for the pacemaker patients was 13% compared to 5% in the nonpacemaker patients, but this difference was not statistically significant. Backup bradycardia pacing in future generation devices may improve the outcome of non VT/VF sudden cardiac death in at least some of the ICD recipients.     

Sudden Death Mortality in Implantable Cardioverter Defibrillator Patients

Implanfable Cardioverter defibrillator (ICD) prevention of sudden cardiac death (SCD) is not absolute and our experience was reviewed to determine the frequency and nature of SCO in this population. The incidence and cause of mortality in 56 consecutive patients, who underwent ICD implantation beginning May 1982 with follow-up through May 19, 1990 were analyzed. Twenty-one patients died, 33% of the mortality was due to SCD, and 52% of deaths may be considered arrhythmic. The cumulative 1, 3, and 5 year SCD survivals were 93%, 89%, and 75%. All seven patients dying of SCD presented initially with SCD, all received previous shocks prior to SCD, and two of the seven patients had devices that were probably inactive at the time of death. We conclude that ICDs reduce but by no means eliminate arrhythmic death, particularly in those at highest risk for SCD. Arrhythmic death remained the most common cause of death in this population.     

A Subcutaneous Lead Array for Implantable Cardioverter Defibrillators

Two patients received an implantable cardioverter defibrillator with the combination of a transvenous lead and a subcutaneous lead array with three branches. This approach allowed us to find low defibrillation threshoids in both patients (≤10 and ≤ 15 joules [J], respectively], which was impossible with a transvenous catheter. In a third patient, a crinkled subcutaneous patch was replaced by an array. The defibrillation threshoid with the array was ≤ 20 J, as opposed to ≤24 J with the patch. No surgical problems occurred. The subcutaneous array is a technical improvement for tiie therapy with impiantable defibrillators, when a single catheter system is not sufficient to ensure a safety margin for defibrillation, or when surgicai or postsurgical problems occur with a subcutaneous patch.     

Implantable Cardioverter Defibrillators in Patients with Chagas' Disease: Are They Different from Patients with Coronary Disease?

Chagas' disease is a parasitic affliction, endemic to certain regions of South America, which may lead to a chronic dilated nonischemic cardiomyopathy. Ten Chagasic patients were compared to 18 coronary patients undergoing transvenous ICD implantation for ventricular tachycardia (VT), ventricular fibrillation (VF), or aborted cardiac arrest. Indications for ICD implantation were either drug intolerance or refractoriness, or no inducible tachyarrhythmia at EPS. There were no statistically significant differences between the Chagas and coronary artery disease groups with respect to age (60.2 vs 62.6 yrs], NYHA Class II (50% vs 62%), ejection fraction (31.1% vs 29.7%), and incidence of cardiac arrest (20% vs 33%), respectively. The following ICD implant and long-term follow-up variables were compared between the two groups: pacing threshold (0.94 V vs 0.95V), defibrillation threshold (19.5 J vs 19.6 J), number of VT episodes (414 vs 435), number of spontaneous VT terminations (86 vs 187), percent efficacy of antitachycardia pacing (93.9% vs 92.1 %), and total number of shocks (112 vs 145). These differences were not statistically significant. We conclude that patients with Chagas' disease, compared with coronary artery disease patients, have similar clinical characteristics leading to ICD implantation. Furthermore, no differences were found with respect to ICD and long-term follow-up characteristics between the two groups.     

Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators: How Many Attempts Are Useful?

The purpose of this study was to determine the termination and acceleration rates for 1 to 6 attempts of antitachycardia pacing (ATP) delivered by ICD in order to terminate spontaneously occurring VTs. Twenty-four ICD recipients with active ATP programs, including a maximum of six ATP sequences and spontaneously occurring VTs during follow-up, were investigated. During a mean follow-up of 42 ± 15 months (range, 17–63 months) 413 spontaneous VT episodes (17 ± 14; range, 1–49 per patient) resulting in appropriate ATP delivery by the ICD occurred. ATP successfully terminated 328 episodes (80 %) with a mean number of 1.6 ± 1.1 pacing sequences. Eighty episodes (19%) were accelerated by ATP and 5 (1%) were unresponsive to ATP. The ATP success decreased until the third ATP sequence (59%→ 31%→ 24%), but increased again in the fourth to sixth attempt (46%→ 46%→ 29%). The acceleration rate increased from sequence one to sequence three (8%→ 13%→ 28%), but decreased significantly in further ATP attempts (19%→ 0%→ 0%). The mean time delays until redetection or termination after 4, 5, and 6 attempts of ATP were 22 ± 5 seconds, 37 ± 2 seconds, and 41 ± 9 seconds, respectively. Nine patients (37%) used ≥3 ATP attempts during follow-up and all of them had a therapeutic benefit from it. Five out of 13 VTs (38%) treated with ≥4 attempts could ultimately be terminated by ATP. The results of this study demonstrate that the first ATP sequence is the most effective and that > 4 ATP attempts may be useful in a minority of patients. There seems to be a low risk of VT acceleration by the fourth to sixth ATP sequence. Because of the associated time delay, a high number of ATP attempts should only be programmed in patients with hemodynamically well-tolerated stable VTs.     

Mechanism of Death in Patients with the Automatic Implantable Cardioverter Defibrillator

Fifty patients underwent primary implantation of an automatic implantable cardioverter defibrillator between August 1983 and April 1988 and were entered into a long-term surveillance program. There were a total of 14 deaths (28%) in the entire group occurring at a mean of 8.7 months postimplantation. Eleven deaths were cardiac and three were noncardiac (two pneumonia, one leukemia). The group of deceased patients were similar to the survivors in all respects except for a statistically lower ejection fraction (23% vs 32%) at the time of implantation. In addition, 13/14 (93%) of the deceased patients experienced at least one appropriate AICD discharge at a mean of 4.5 months post implantation. Recorded ECGs at the time of death revealed that most of the sudden deaths were due to electromechanical dissociation and not to AICD-treatable arrhythmias. These data suggest therefore that death in AICD patients is usually cardiac, due primarily to low ejection fraction and occurs in patients who have previously received AICD discharges.     

Outcomes of Elderly Recipients of Implantable Cardioverter Defibrillators

Aims of the Study: To examine the patterns of use, complication rates, and survival in elderly recipients of implantable cardioverter defibrillators (ICD).
Methods and Results: We followed 500 consecutive patients included in the Marburg Defibrillator database for 48 ± 39 months. There were 40 patients (8%) ≥75 and 460 (92%) <75 years of age at the time of implant. The 5-year Kaplan-Meier estimate for appropriate treatment of VT or VF by ICD was 49% among patients <75- versus 57% among patients ≥75-years-old (P = 0.17). The 5-year sudden death rate was similarly low in both groups of patients (2% versus 3%). The 5-year overall mortality rate was significantly higher in patients ≥75 than in patients <75 years of age (55% versus 21%, P = 0.001), due to a higher mortality from heart failure (HF). All procedure-related, lead-related, and pulse generator-related complications were similar in both patient groups (23% versus 25%).
Conclusions: ICD therapy was equally effective in patients ≥75 and patients <75 years of age in the prevention of sudden cardiac death. While the complication rates were similar in both age groups, the long-term mortality was considerably higher in elderly patients, due to a higher mortality from HF. The current ICD therapy guidelines appear applicable to elderly patients who are otherwise medically stable and without advanced HF.     

Clinical Significance of Sleep-Related Breathing Disorders in Patients with Implantable Cardioverter Defibrillators

The prevalence and clinical significance of sleep-related breathing disorders (SRBDs) in patients with cardiac disease and a history of life-threatening ventricular tachyarrhythmias is unclear. Forty consecutive recipients of implantable cardioverter defibrillators (ICDs) with cardiac disease and a documented history of spontaneous, life-threatening, ventricular tachyarrhythmias underwent full night polysomnography. SRBDs were diagnosed if the apnea/hypopnea index was > 10. SRBD were diagnosed in 16 of 40 patients (40%): central sleep apnea (CSA) was present in 9 of these 16 patients (56%), 8 of whom had associated Cheyne-Stoke respiration. Seven of the 16 patients with SRBD (44%) had obstructive sleep apnea (OSA). Patients with and without SRBDs were comparable with respect to left ventricular ejection fraction, NYHA classification, underlying heart disease, ICD indications, and concomitant antiarrhythmic drug and beta-blocker therapy. Patients were followed prospectively for 2 years. ICD-treated ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA (NS). The numbers and circadian distributions of episodes recorded during follow-up in patients without SRBD versus with CSA or OSA were not significantly different (14 ± 25, median = 4 vs 4 ± 5, median = 2.5 vs 15 ± 15, median = 7, respectively). The 2-year mortality, which was entirely attributable to nonsudden cardiac events, was highest in patients with CSA (4/9 [44%], vs 0/7 [0%] with OSA, vs 3/24 patients (12.5%) without SRBD; P < 0.05).     

Implantation of Submammary Implantable Cardioverter Defibrillators

Implantable cardioverter defibrillators (ICDs) are routinely placed in the left pectoral area using a transvenous approach. This approach may result in poor cosmetic outcome and cause psychological problems, especially in younger patients. To avoid this, several alternative implantation techniques have been developed. For cosmetic reasons, we used a submammary technique to implant ICDs into three young women. Apart from defibrillation threshold testing, the procedures were performed under local anesthesia. Threshold testing was done under general anesthesia. Appropriate defibrillation thresholds were obtained in all three cases, and all the patients tolerated the procedure well. There were no complications in a mean of 22 months of follow-up, and the cosmetic results were very good.(PACE 2004; 27[Pt. I]:779–782)     

Renal Extracorporeal Shock Wave Lithotripsy Performed in Patient with Implantable Cardioverter Defibrillator

The effect of extracorporeal shock wave lithotripsy on the automatic implantable cardioverter defibrillator is unknown. To evaluate what effect might occur, a non-implanted automatic implantable cardioverter defibrillator was subjected to a full course of extracorporeal shock wave lithotripsy while inactive. Bench testing by the manufacturer after lithotripsy demonstrated normal function of the device. A patient with an automatic implanted cardioverter defibrillator who required contralateral extracorporeal shock wave lithotripsy then underwent this procedure. The right renal calculus was destroyed successfully with no apparent damage to the automatic implantable cardioverter defibrillator. A test of the automatic implantable cardioverter defibrillator after lithotripsy demonstrated normal sensing and conversion of induced ventricular tachycardia.     

The Automatic Implantable Cardioverter-Defibrillator

The automatic implantable cardioverter-defibrillator is an electronic device designed to monitor the heart continuously, to identify malignant ventricular tachyarrhythmias, and then to deliver effective countershock to restore normal rhythm. There are two defibrillating electrodes which are also used for waveform analysis; one is located in the superior vena cava, the other is placed over the cardiac apex. A third bipolar right ventricular electrode serves for rate counting and R-wave synchronization. When ventricular fibrillation occurs, a 25 joule pulse is delivered; when ventricular tachycardia faster than a preset rate is detected, the discharge is R-wave synchronized. The device can recycle three times if required. Special batteries can deliver over 100 shocks or provide a 3-year monitoring life. Implantation of the device is made either through a thoracotomy or by a subxiphoid approach. Thus far, the device has been implanted in 160 patients with a follow-up of 42 months. Acceleration of ventricular tachycardia to a faster rhythm or to ventricular fibrillation occurred only rarely and is dealt with most successfully through recycling. Actuarial analysis of the initial 52 patients has indicated 22.9% one-year total mortality, a 52% decrease from the 48% mortality that would be expected in the same group of patients without the device: the mortality attributed to arrhythmias was only 8.5%. In conclusion, the automatic cardioverter-defibrillator can reliably identify and correct potentially lethal ventricular tachyarrhythmias, leading to a substantial increase in survival in properly selected high-risk patients.     

Transvenous Cardioverter Defibrillators: Cost Implications of a Less Invasive Approach

To assess the economic impact of a transvenous lead system for an implantable Cardioverter defibrillator (ICD), we evaluated the hospital charges for two groups of patients: group I patients (n = 23) underwent implantation of an ICD generator with an epicardial lead system via a thoracotomy and group II patients (n = 25) underwent implantation of the same generator using transvenous leads. There was no difference in demographics between the two groups. There was a 15% decrease in total charges for the transvenous group compared to the thoracotomy group ($54,142 vs $63,359, P < 0.05). Evaluation of the component charges revealed that the decline could be attributed to a reduction in implant ($27,328 vs $29,285, P < 0.02) and convalescent charges ($7,703 vs $15,179, P < 0.01) for the transvenous group. There was a corresponding decrease in length of stay for the transvenous group (22 vs 29 days, P < 0.05) largely secondary to a 38% reduction in convalescent length of stay (8 vs 13 days, P < 0.05). We conclude that the use of transvenous lead systems for the ICD results in a significant reduction in hospital charges as well as hospital length of stay.