Right Ventricular Dysfunction and the Incidence of Implantable Cardioverter‐Defibrillator Therapies

Introduction: Implantable cardioverter‐defibrillator (ICD) therapy is well established in preventing sudden cardiac death in patients with left ventricular dysfunction. The influence of right ventricular (RV) function on ICD therapy for sudden cardiac death (SCD) is not known. Methods: We retrospectively studied 222 patients receiving an ICD for primary prevention of SCD. Baseline clinical and echocardiographic data were gathered. RV systolic function was qualitatively assessed as normal or abnormal (described as mildly, moderately, or severely reduced). Primary endpoint was combined ICD therapy or death and secondary endpoint was ICD therapy alone. Results: The mean follow‐up was 940 ± 522 days. The mean left ventricular ejection fraction was 0.23 ± 0.07. By Kaplan‐Meier analysis, RV dysfunction was predictive of combined ICD therapy or death when comparing between normal and abnormal RV function (P = 0.008) and among qualitative ranges of RV function (P = 0.012). RV dysfunction was not predictive of ICD therapy alone with either type of classification. After adjusting for clinical covariates, severe RV dysfunction was predictive of the combined endpoint of ICD therapy or death (HR 2.02, 95% CI 1.04–3.92, P = 0.037). Conclusion: Severe RV dysfunction appears to be an independent predictor of the combined endpoint of ICD therapy or death. RV dysfunction does not reliably predict the incidence of ICD therapy alone.     

Low Incidence of Lead Related Complications Associated with Nonthoracotomy Implantable Cardioverter Defibrillator Systems

Implantable cardioverter defibrillators (ICDs) are increasingly being implanted without the need for thoracotomy. Long-term lead performance and stability were evaluated in 150 consecutive patients in whom 1 of 3 nonthoracotomy ICD lead systems was implanted over a 3-year period from September 1990. Results: Twelve (8%) patients (7 males, 5 females) experienced 13 lead complications during a follow-up period of 12 ± 10 months. Complications were related to intracardiac leads in 7 (4 dislodgments, 2 fractures, 1 right ventricular perforation) and patch leads in 6 (2 folding, 1 fracture, 1 erosion, and 2 hematomas) cases. Freedom from lead related complications at 1 year was 92% (95% confidence interval, 86%–95%). A significant difference in freedom from lead complications between the two most frequently implanted lead systems was observed (P = 0.02). Complication rates were similar in the initial 75 and the more recent 75 implants (P= 0.5). The median time between lead implant and detection of complications was 37 days (range 3–1,147). Complications were diagnosed before hospital discharge in only two cases. In five patients, complications were asymptomatic and in three of these, reoperation was required due to inadequate defibrillation thresholds. Reoperation was necessary in 9 of 12 patients. Conclusions: Nonthoracotomy ICD lead systems are associated with a low complication rate. Complications may or may not cause symptoms, usually occur after hospital discharge, and require reoperation. Complications are not related to a "learning curve." There is a significant difference in performance between different lead systems.     

Holter Documented Sudden Death in a Patient with an Implanted Defibrillator

A 68-year-old man with recurrent attacks of monomorphic ventricular tachycardia (VT) received a pacer cardioverter defibrillator featuring antitachycardia pacing and cardioversion/defibrillation. Over 300 episodes of VT were successfully terminated by antitachycardia pacing. During Holter monitoring the patient experienced supraventricular tachycardia with delivery of multiple antitachycardia pacing, cardioversion, and defibrillation therapies ending with the death of the patient. The following factors played a role in the unfortunate outcome of this patient: 1. triggering of VT therapy by an unexpected high sinus rate; 2. atrial fibrillation induced by cardioversion therapy; 3. a gradual and continuous increase in rate during atrial fibrillation possibly caused by repeated VT and ventricular fibrillation therapies and/or by a thrombus, found at autopsy, in a bypass graft; and 4. the limited ability of presently available defibrillators to distinguish between ventricular and supraventricular arrhythmias.     

Does Reception of Appropriate Shocks from the Implantable Cardioverter Defibrillator Affect Survival?

The impluntable Cardioverter defibrillafor has become an important therapeutic modality for treatment of life-threatening ventricular tachyarrhythmias. Recent reports have suggested that patients who receive appropriate shocks from this device have an inordinately high overall mortality, and questioned the extent of benefit these patients derive from the implant. This report analyzed the survival among 184 patients who received the implantable Cardioverter defibrillator to assess survival differences between patients who received appropriate shocks versus those who did not. At a mean follow-up of 24 ± 18.7 months, 68 patients received an appropriate shock from their device while 116 did not receive an appropriate shock. Overall survival of the entire population was quite similar (o those published by others. There was no significant difference between overall survival of patients who received an appropriate shock versus those who did not. However, there was a statistically significant difference in sudden death mortality. The group of patients that received appropriate shocks included all five sudden deaths. This observation suggested that sudden death in this population was likely due to ventricular tachyarrhythmias rather than strictly bradycardia or asystole. The "benefit" of the device to the entire population was also assessed by estimating survival after receipt of the first appropriate shock. Using this approach, an estimated 10% of patients died without receiving an appropriate shock. In other words, ultimately, 90% of patients were expected to benefit from the device. This survival curve, which initiated only after receipt of the first appropriate shock was fairly similar to those estimated from conventional methods. Therefore, survival after receipt of an appropriate shock was comparable to overall survival and there was no significant difference between survival of patients who received appropriate shocks and those who did not.     

Basal Exit Site of Clinical Ventricular Tachycardia is an Independent Predictor of Antitachycardia Pacing Failure in Implantable Cardioverter‐Defibrillators Recipients

Background: Little is known about predictors of antitachycardia pacing (ATP) failure in implantable cardioverter defibrillator (ICD) recipients. Distance between the stimulation site and the ventricular tachycardia (VT) site of origin may critically affect ATP effectiveness. We hypothesized that ATP may be less effective in ICD patients who had basal VT than in those who had apical VT. Methods: We reviewed data from 52 patients with sustained monomorphic VT and left ventricular disease referred for ICD implantation. ATP was delivered exclusively at the right ventricular apex. The clinical VTs site of origin (basal, midventricular, or apical) was determined in each patient, using 12‐lead electrocardiogram. VTs episodes treated with ATP during the 1‐year follow‐up were studied. ATP success rate (%), defined as the ratio between the number of successful ATP sequences and the number of delivered ATP sequences, was determined in each patient. Results: VT exit site was apical in 19 patients (36%), basal in 18 patients (35%), and midventricular in 15 patients (29%). In those 52 patients, 1,393 ATP sequences, delivered to treat 761 VT episodes, were analyzed. ATP success rate was found to be associated with the VT site of origin (median [interquartile range]): basal (33%[11–67]), midventricular (50%[37–100]), apical (100%[41–100]) (P = 0.027). Multivariate analysis identified basal VT site of origin as an independent predictor of ATP failure (P = 0.023). Conclusion: ATP is less effective in ICD patients who had basal VT than in those who had apical VT before ICD implantation. (PACE 2012; 35:1209–1216)     

Implantable Cardioverter Defibrillator Therapy for Prevention of Sudden Cardiac Death in Children in The Netherlands

Introduction: Implantable cardioverter defibrillator (ICD) therapy is increasingly used in children. The purpose of this multicenter study is to evaluate mid‐term clinical outcome and to identify predictors for device discharge in pediatric ICD recipients. Methods and Results: From 1995 to 2006, 45 patients in The Netherlands under the age of 18 years received an ICD. Mean age at implantation was 10.8 ± 5.2 years. Primary prevention (N = 22) and secondary prevention (N = 23) were equally distributed. Underlying cardiac disorders were primary electrical disease (55%), cardiomyopathy (20%), and congenital heart disease (17%). The follow‐up was 44 ± 32.9 months. Three patients (7%) died and one patient (2%) underwent heart transplantation. ICD‐related complications occurred in eight patients (17%), seven of whom had lead‐related complications. Fourteen patients (31%) received appropriate ICD shocks; 12 patients (27%) received inappropriate ICD shocks. Fifty‐five percent of 22 ICD recipients under the age of 12 years received appropriate shocks, which was higher as compared with 9% of 23 older ICD recipients (P = 0.003). Although the incidence of appropriate shocks in the present study was larger in secondary prevention (9/23; 39%) as compared with primary prevention (5/22; 23%), this difference did not reach significance. Conclusions: In our population of patients, children <12 years of age had more appropriate shocks than patients 13–18 years. The complication rate is low, and is mainly lead related. (PACE 2010; 33:179–185)     

Complications of Third-Generation Implantable Cardioverter Defibrillator Therapy

To determine the incidence of complications of third-generation implantable cardioverter defibrillator (ICD) therapy, 144 patients were prospectively studied who underwent first implant of third-generation devices (i.e., ICD systems with biphasic shocks, ECC storage capability, and nonthoracotomy lead systems). During 21 ± 15 months of follow-up, 41 (28%) patients had one or more complications. No patient died perioperatively (30 days) and no ICD infection was observed during follow-up. Complications included bleeding or pocket hematoma (hemoglobin drop > 2 g/dL) in 5 (3%) patients, prolonged reversible ischemic neurological deficit in 1 (1%) patient, postoperative deep venous thrombosis of leg in 1 (1%) patient, pneumothorax in 2 (1%) patients, difficulty to defibrillate ventricular fibrillation intraoperatively in 2 (1%) patients, generator malfunction in 1 (1%) patient, arthritis of the shoulder in 3 (2%) patients, and allergic reaction to prophylactic antibiotics in 2 (1%) patients. A total of seven lead related complications were observed in six (4%) patients including endocardial lead migration in four (3%) patients. Twenty-three (16%) patients received inappropriate shocks for supraventricular tachyarrhythmias (n = 13), non-sustained ventricular tachycardia (VT) (n = 7), or myopotential oversensing (n = 3). We conclude that serious complications such as perioperative death or ICD infection are rare in patients with third-generation ICDs. Lead-related problems and inappropriate shocks during follow-up are the most frequent complications of third-generation ICD therapy. Recognition of these complications should promote advances in ICD technology and management strategies to avoid their recurrence.     

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.     

Complications of Implantable Cardioverter Defibrillator Therapy: Follow-Up of 241 Patients

In order to determine the incidence of complications of impJantable cardioverter defibrillator (ICD) therapy, 241 patients with a total of 353 ICD implantations were followed for 24 ± 20 months. Complications were defined as any untoward effects experienced by the patient related to the ICD implantation and function or death within 4 weeks of implant or before hospital discharge. During follow-up, 129 of 241 patients (53%) had a total of 166 complications. An operative procedure was required to correct the complication in 50 of the 241 patients (21%). No patient died intraoperativeiy, but eight patients died within 4 weeks postoperatively or before hospital discharge. ICD infection required removal of the device in 13 patients (5%). Twenty-six patients (11%) had postoperative respiratory complications. Postoperative bleeding and/or thrombosis occurred in 11 patients (4%). Endocardial lead migration was observed in nine patients (4%) and lead adapter or insulation break occurred in nine patients (4%). Fifty-four patients (22%) experienced ECC-documented discharges for non-VT rhythm. In conclusion, although perioperative mortality in ICD patients is low, the maiority of patients have complications during followup. Recognition of these complications may allow for advances in ICD technology and management strategies to avoid their occurrence.     

Initial Clinical Experience with a New Small Sized Third-Generation Implantable Cardioverter Defibrillator: Results of a Multicenter Study

This study reports the acute clinical experience with the new CPI VENTAK MINI: a small sized (68 cc), implantable cardioverter defibrillator (ICD) with 33 J stored energy. Implantation of the device was attempted in 113 patients (90 men, mean age 57 ± 16 years, 64 with coronary artery disease, mean left ventricular ejection fraction 41%) with ventricular tachycardia or ventricular fibrillation (VF). All 113 patients (100%) were ultimately implanted, 12% of them for ICD replacement. Transvenous lead implantation was accomplished in all 104 patients (100%) receiving new leads, 95% of them with a single lead configuration. The safety criteria for implantation (2 consecutive VF conversions at 15 J or 3 at 20 J. in both cases without failures to convert) were demonstrated in all but 7 patients (6%). In 6 of these, safety criteria were not fully assessed while in the last patient defibriliation efficacy was not determined. Of the 104 patients with new leads, 90% underwent pectoral implantation. Of the 9 patients (9%) abdominally implanted, only 4 (4%) (3 children) were judged small sized for pectoral implant. At predischarge testing, reliable VF detection and conversion were noted in 96 of 97 patients tested. There was no perioperative mortality. At a 3.6 ± 1.3 months follow-up, 34% of the patients had a spontaneous arrhythmic event, and 24% of the patients received shocks. Clinically inappropriate therapies occurred in 8% of the episodes in which any kind of therapy was delivered. This study demonstrates the short-term clinical efficacy and safety of the new device, and that pectoral implantation can be performed in the large majority of patients.     

Implantation of the Automatic Implantable Cardioverter Defibrillator (AICD): Practical Aspects

Most patients who are resuscitated from an episode of sudden cardiac death or one of sustained ventricular tachycardia (VT) can now be treated using serial electrophysiologic testing as a guide to drug therapy. Recurrence rates are low if an antiarrhythmic regimen can be found which prevents induction of VT. Patients failing serial drug testing have a high recurrence rate (approximately 50%/year). Most clinicians now refer such patients for either experimental antiarrhythmic therapy or electrical intervention. The most promising of the electrical interventions (including tachycardia converting pacemakers and intraoperative mapping)has been the automatic implantable cardioverter defibrillator (AICD). Only recently has the AICD been released from investigative status by the Food and Drug Administration. It can be implanted safely and with favorable clinical outcome if the techniques of implantation are well understood and used often. The text incorporates the authors' experience in implanting nearly 200 devices and is intended as a practical guide to the use of the AICD.     

The Value of DDD Pacing in Patients with an Implantable Cardioverter Defibrillator

Although the beneficial effects of DDD pacing are well known, currently available ICDs provide only fixed rate ventricular antibradycardia pacing. In a consecutive series of 139 patients with ICDs, we have analyzed the need for antibradycardia pacing and the indications for DDD pacing. We also report our initial experience with the Defender 9001 (ELA Medical, France) DDD-ICD. Out of 139 patients, 25 (18%) were in need of antibradycardia pacing. Ten patients already had a pacemaker at the time of ICD implantation and ten other patients had a conventional pacemaker indication at that time. Five patients became pacemaker dependent during a follow-up of 20 ± 8 months. The disorders necessitating pacemaker therapy were high degree AV conduction disturbances in 72%, sick sinus syndrome in 12%, and AF with a slow ventricular response in 16% of patients. Based upon current indications, DDD pacing was indicated in 20 (80%) of 25 patients. The Defender 9001 DDD-ICD (ELA Medical) was used in two patients with ischemic cardiomyopathy and pacemaker syndrome with VVI pacing. Cardiac output during DDD pacing increased by 36% in one patient with an increase in VO₂ max during exercise of 29%. The other patient showed an increase in cardiac output of 50% with DDD pacing, and, while unable to exercise with VVI pacing, had a VO_2max of 24 mL/kg per minute during DDD pacing. Up to 18% of our ICD patients are in need of antibradycardia pacing. Of these pacemaker dependent patients, 80% have an indication for DDD pacing. Our first clinical experience with a DDD-ICD confirms the hemodynamic benefit of AV synchronous pacing in ICD patients with pacemaker syndrome.     

AutoCapture with Dual-Coil Leads of Implantable Cardioverter Defibrillator

AutoCapture™ (AC) can confirm ventricular capture with true bipolar single coil leads of implantable cardioverter defibrillators (ICD). The compatibility of AC with a new, true bipolar, dual-coil ICD lead needed to be evaluated. This multicenter study enrolled 46 patients (69 ± 10 years, 37 men) undergoing ICD implantation. All patients received a true bipolar, dual-coil lead. Evoked response (ER) sensitivity and AC threshold tests were performed using a pulse generator with the AC algorithm. Mean capture threshold was 0.85 ± 0.67 V, pacing impedance 612 ± 225 Ω, R wave amplitude 13.85 ± 6.17 mV, and defibrillation threshold 14.4 ± 5.1 J. AC was recommended in 45 patients (97.8%) with ER and polarization values of 14.86 ± 7.32 mV and 0.87 ± 0.69 mV, respectively. The AC algorithm was highly compatible with true bipolar, dual-coil ICD leads. An AC algorithm specifically designed for an ICD may improve the generator longevity. Further examination of AC compatibility with other leads is warranted.     

Practical Aspects of Implantable Defibrillator Therapy in Patients with Congenital Heart Disease

Improved awareness of the risk for malignant ventricular arrhythmias in patients with congenital heart disease (CHD), together with dramatic advances in implantable cardioverter-defibrillator (ICD) technology, have led to a rapid increase in device therapy for this population. Clinical challenges remain surrounding patient selection and difficulties with lead positioning that arise in response to the anatomic and physiologic complexities of CHD. This article will attempt to review contemporary data on ICD use in the CHD population with particular attention to the novel implant methodology required for many of these patients.