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.     

Inappropriate Implantable Cardioverter-Defibrillator Therapy Due to the Detection of Premature Ventricular Complexes

Inappropriate shocks delivered by implantable cardioverter-defibrillators may occur in 15%-40% of patients treated with these devices. This article describes a rare cause for inappropriate shocks. Two patients received inappropriate shocks due to the presence of premature ventricular complexes during attempted reconfirmation of ventricular fibrillation. Knowledge of device algorithms for detection and reconfirmation of ventricular fibrillation, designed to have a high degree of sensitivity and therefore lower specificity, allows for reprogramming to avoid further inappropriate shocks.     

Comparison of ICD shock rates in Japanese and non‐Japanese patients in the PainFree SST study

Background

The PainFree Smart Shock Technology (SST) study showed a low implantable cardioverter‐defibrillator (ICD) inappropriate shock rate. However, the majority of patients were from Western countries with patient characteristics different from those in Japan. ICD shock rates using the novel SST algorithms in Japanese patients are still unknown.

Methods

All 2,770 patients in the PainFree SST study (Japan [JPN]: N = 181, other geographies [OJPN]: N = 2,589) were included in this analysis.

Results

Japanese patients had higher average left ventricular ejection fraction (P < 0.0001), higher prevalence of secondary prevention indications (P < 0.0001), nonischemic cardiomyopathy (P < 0.0001), and permanent atrial fibrillation (P < 0.0001). The appropriate shock rate at 12 months was not different between JPN and OJPN: 6.4% and 6.3%, respectively (P = 0.95). The inappropriate shock rate at 12 months was significantly higher in Japanese patients (2.9% vs 1.7%, P = 0.017). However, after propensity score matching to adjust for the difference in baseline characteristics, the difference in inappropriate shock rate was not statistically significant (P = 0.51).

Conclusions

There was no difference in the appropriate shock rate between Japan and other geographies. The inappropriate shock rate in Japan was low, although it was slightly higher compared to other geographies due to baseline characteristics, including a higher prevalence of permanent AF. There was not a statistically significant difference after adjusting for baseline characteristics.

     

Recurrent Implantable Cardioverter‐Defibrillator Replacement Is Associated with an Increasing Risk of Pocket‐Related Complications

Background: Despite beneficial effects of implantable cardioverter‐defibrillator (ICD) therapy, limited service life results in replacement within the majority of patients. Data concerning the effect of replacement procedures on the occurrence of pocket‐related adverse events are scarce. In this study, the requirement for pocket‐related surgical re‐interventions following ICD treatment and the effect of device replacement were evaluated. Methods: From 1992 to 2008, 2,415 patients receiving an ICD at the Leiden University Medical Center were analyzed. Pocket‐related complications requiring surgical re‐intervention following ICD implantation or replacement were noted. Elective device replacement, lead failure, and device malfunction were not considered pocket‐related complications. Results: A total of 3,161 ICDs were included in the analysis. In total, 145 surgical re‐interventions were required in 122 (3.9%) ICDs implanted in 114 (4.7%) unique patients. Three‐year cumulative incidence for first surgical re‐intervention in all ICDs was 4.7% (95% confidence interval [CI] 3.9–5.5%). Replacement ICDs exhibited a doubled requirement for surgical re‐intervention (rate ratio 2.2, 95% CI 1.5–3.0). Compared to first implanted ICDs, the occurrence of surgical re‐intervention in replacements was 2.5 (95% CI 1.6–3.7) times higher for infectious and 1.7 (95% CI 0.9–3.0) for noninfectious causes. Subdivision by the number of ICD replacements showed an increase in the annual risk for surgical re‐intervention, ranging from 1.5% (95% CI 1.2–1.9%) for the first, to 8.1% (95% CI 1.7–18.3%) for the fourth implanted ICD. Conclusions: ICD replacement is associated with a doubled risk for pocket‐related surgical re‐interventions. Furthermore, the need for re‐intervention increases with every consecutive replacement. (PACE 2010; 1013–1019)     

Multiple Inappropriate Shocks Precipitated by Interrogation of an Implantable Cardioverter Defibrillator

A 57-year-old man suffered multiple inappropriate shocks from an implantable cardioverter defibrillator that could not be inactivated because the magnet switch feature was deactivated. Attempts to interrogate the defibrillator caused shocks to be delivered. Emergent explantation was performed and a loose sensing lead was discovered. Sensing and defibrillation leads functioned normally, and testing of the explanted generator demonstrated no abnormalities. A new generator was put in place and the patient has been without shocks for 6 months. This case illustrates the need for robust methods of attenuating electromagnetic interference and the importance of multiple methods of device inactivation.     

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.     

Response to Cardiac Resynchronization Therapy in Patients with Heart Failure and Renal Insufficiency

Background: Renal insufficiency (RI) adversely impacts prognosis in heart failure (HF) patients, partly because renal and cardiac dysfunction are intertwined, yet few cardiac resynchronization therapy (CRT) studies have examined patients with moderate‐to‐severe RI. Methods: We analyzed 787 CRT‐defibrillator (CRT‐D) recipients with a glomerular filtration rate (GFR) measured prior to implant. Patients were grouped by GFR (in mL/min/1.73 m²): ≥60 (n = 376), 30–59 (n = 347), and <30 (n = 64). Overall survival, changes in left ventricular (LV) ejection fraction and LV end‐systolic diameter, and GFR change at 3–6 months were compared among CRT‐D groups and with a control cohort (n = 88), also stratified by GFR, in whom LV lead implant was unsuccessful and a standard defibrillator (SD) was placed. All patients met clinical criteria for CRT‐D. Results: Among CRT‐D recipients, overall survival improved incrementally with higher baseline GFR (for each 10 mL/min/1.73 m² increase, corrected hazard ratio [HR] 1.21, 95% confidence interval [CI] 1.13–1.30, P < 0.0001). Survival among SD and CRT‐D patients within GFR < 30 and GFR ≥ 60 groups was similar, whereas CRT‐D recipients with GFR 30–59 had significantly better survival compared to SD counterparts (HR 2.23, 95% CI 1.34–3.70; P = 0.002). This survival benefit was associated with improved renal and cardiac function. CRT recipients with GFR ≥ 60 derived significant echocardiographic benefit but experienced a GFR decline, whereas those with GFR < 30 had no echocardiographic benefit but did improve GFR. Conclusions: CRT may provide the largest survival benefit in HF patients with moderate RI, perhaps by improving GFR and LV function. Severe baseline RI predicts poor survival and limited echocardiographic improvement despite a modest GFR increase, such that CRT may not benefit those with GFR < 30 mL/min/1.73 m². CRT recipients with normal renal function derive echocardiographic benefit but no overall survival advantage. (PACE 2010; 850–859)     

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)     

Rates of upgrade of ICD recipients to CRT in clinical practice and the potential impact of the more liberal use of CRT at initial implant

Background: Many implantable cardioverter defibrillator (ICD) recipients may develop indications for cardiac resynchronization therapy (CRT) during follow‐up. However, the actual upgrade rate during follow‐up in clinical practice is not known. Methods: We performed a single center retrospective observational study of all new ICD implants over 5 years (2003–2007). The rate of CRT upgrade of patients initially implanted with a single‐/dual‐chamber ICD during follow‐up was assessed. The impact of using alternative criteria on the need for CRT in ICD recipients at initial implant was also evaluated. Results: During the study period, there were 549 new ICD implants. The initial implant was a single/dual‐chamber ICD in 73% (n = 399) and a CRT‐D in 27% (n = 150). During follow‐up (48±20 months) of the 399 ICD recipients, 70 (17.5%) died and 15 (3.8%) were upgraded to CRT, including eight cases where left ventricular lead implant had been initially unsuccessful. Upgrade rates at 1, 3, and 5 years were 0.03%, 2.4%, and 5.1%, respectively. Using alternative CRT criteria (left ventricular ejection fraction [LVEF]≤30%, QRS ≥130 ms, New York Heart Association I‐IV) 42.6% (n = 234) of ICD recipients met criteria for CRT at initial implant. Conclusion: In this retrospective single center study, rates of CRT upgrade in ICD recipients over the medium term were low, which may reflect underuse in otherwise appropriate candidates. The more liberal use of CRT at initial implant in patients with a reduced LVEF, a broad QRS, but only mild heart failure symptoms would require approximately 50% increase in CRT use in ICD recipients at initial implant, and may help address some of the suggested underutilization. (PACE 2012; 35:73–80)     

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.