Lacosamide-Induced Recurrent Ventricular Tachycardia in the Acute Care Setting.

Lacosamide is a new-generation antiepileptic drug (AED) most commonly used adjunctively in the setting of partial-onset seizures refractory to traditional therapy. We describe the first case report, to our knowledge, of a patient who developed recurrent, sustained ventricular tachycardia with multiple administrations of lacosamide in an acute setting. A 70-year-old woman with a history significant for valvular heart disease was admitted to the inpatient cardiology service for worsening heart failure. On hospital day 7, she received a bioprosthetic aortic valve. Prior to surgery and immediately after, the patient's electrocardiogram (ECG) was normal. After developing multiple generalized tonic-clonic seizures refractory to levetiracetam, fosphenytoin, and valproic acid, the decision was made to initiate lacosamide. Two hours following the second lacosamide dose, the patient developed a wide complex QRS that transitioned into sustained ventricular tachycardia requiring electrical cardioversion. Sustained ventricular tachycardia occurred again, just hours after the third dose of lacosamide was given. Following cessation of lacosamide, the patient's QRS interval normalized and has since had no documented episodes of ventricular tachycardia. Clinicians should be aware of the potential for life-threatening rhythmic disturbances in patients initiated on lacosamide and the need for vigilant ECG, electrolyte, and drug-drug monitoring.

Outcomes of patients with definite and suspected isolated cardiac sarcoidosis treated with an implantable cardiac defibrillator.

PURPOSE: Cardiac sarcoidosis (CS) patients are at increased risk for sudden death. Isolated CS is rare and can be difficult to diagnose. METHODS: In this multicenter retrospective review, patients with CS and an implantable cardiac defibrillator (ICD) were identified. RESULTS: Of 235 patients with CS and ICD, 13 (5.5 %) had isolated CS, including 7 (3.0 %) with definite isolated CS (biopsy or necropsy-proven) and 6 (2.6 %) with suspected isolated CS based on a constellation of clinical, ECG, and imaging findings. Among 13 patients with isolated CS, 10 (76.9 %) were male, mean age was 53.8 ± 7.6 years, and mean left ventricular ejection fraction was 38.3 ± 16.5. Diagnosis was made by cardiac magnetic resonance (CMR) (n = 2), biopsy (n = 3), CMR and biopsy (n = 2), CMR and positron emission tomography (PET) (n = 2), PET (n = 1), late enhanced cardiac CT (n = 1), pathology at heart transplant (n = 1), and autopsy (n = 1). Eight of 13 (61.5 %) patients with isolated CS had a secondary prevention indication (VT in 6 and VF in 2) vs. 80 of 222 (36.0 %) with sarcoidosis in other organs (p = 0.04). Over a mean of 4.2 years, 9 of 13 (69.2 %) patients with isolated CS received appropriate ICD therapy, including anti-tachycardia pacing (ATP) and/or shock, compared with 75 of 222 (33.8 %) patients with cardiac and extracardiac sarcoidosis (p = 0.0150). Six of 7 (85.7 %) patients with definite isolated CS received appropriate ICD intervention, compared with 78 of 228 patients (34.2 %) without definite isolated CS (p = 0.0192.) CONCLUSIONS: In this retrospective study, patients with isolated CS had very high rates of appropriate ICD therapy. Prospective, long-term follow-up of consecutive patients with isolated CS is needed to determine the true natural history and rates of ventricular arrhythmias in this rare and difficult-to-diagnose disease.

Prevention of sudden cardiac death with implantable cardioverter-defibrillators in children and adolescents with hypertrophic cardiomyopathy.

OBJECTIVES: The aim of this study was to determine the efficacy of implantable cardioverter-defibrillators (ICDs) in children and adolescents with hypertrophic cardiomyopathy (HCM). BACKGROUND: HCM is the most common cause of sudden death in the young. The availability of ICDs over the past decade for HCM has demonstrated the potential for sudden death prevention, predominantly in adult patients. METHODS: A multicenter international registry of ICDs implanted (1987 to 2011) in 224 unrelated children and adolescents with HCM judged at high risk for sudden death was assembled. Patients received ICDs for primary (n = 188) or secondary (n = 36) prevention after undergoing evaluation at 22 referral and nonreferral institutions in the United States, Canada, Europe, and Australia. RESULTS: Defibrillators were activated appropriately to terminate ventricular tachycardia or ventricular fibrillation in 43 of 224 patients (19%) over a mean of 4.3 ± 3.3 years. ICD intervention rates were 4.5% per year overall, 14.0% per year for secondary prevention after cardiac arrest, and 3.1% per year for primary prevention on the basis of risk factors (5-year cumulative probability 17%). The mean time from implantation to first appropriate discharge was 2.9 ± 2.7 years (range to 8.6 years). The primary prevention discharge rate terminating ventricular tachycardia or ventricular fibrillation was the same in patients who underwent implantation for 1, 2, or ≥3 risk factors (12 of 88 [14%], 10 of 71 [14%], and 4 of 29 [14%], respectively, p = 1.00). Extreme left ventricular hypertrophy was the most common risk factor present (alone or in combination with other markers) in patients experiencing primary prevention interventions (17 of 26 [65%]). ICD-related complications, particularly inappropriate shocks and lead malfunction, occurred in 91 patients (41%) at 17 ± 5 years of age. CONCLUSIONS: In a high-risk pediatric HCM cohort, ICD interventions terminating life-threatening ventricular tachyarrhythmias were frequent. Extreme left ventricular hypertrophy was most frequently associated with appropriate interventions. The rate of device complications adds a measure of complexity to ICD decisions in this age group.

Efficacy and safety of implantable cardiac defibrillators for treatment of ventricular arrhythmias in patients with cardiac sarcoidosis.

AIMS: Implantable cardiac defibrillator (ICD) implantation is a class IIA recommendation for patients with cardiac sarcoidosis (CS). However, little is known about the efficacy and safety of ICDs in this population. The goal of this multicentre retrospective data review was to evaluate the efficacy and safety of ICDs in patients with CS. METHODS AND RESULTS: Electrophysiologists at academic medical centres were asked to identify consecutive patients with CS and an ICD. Clinical information, ICD therapy history, and device complications were collected for each patient. Data were collected on 235 patients from 13 institutions, 64.7% male with mean age 55.6 ± 11.1. Over a mean follow-up of 4.2 ± 4.0 years, 85 of 234 (36.2%) patients received an appropriate ICD therapy (shocks and/or anti-tachycardia pacing) and 67 of 226 (29.7%) received an appropriate shock. Fifty-seven of 235 patients (24.3%) received a total of 222 inappropriate shocks. Forty-six adverse events occurred in 41 of 235 patients (17.4%). Patients who received appropriate ICD therapies were more likely to be male (73.8 vs. 59.6%, P = 0.0330), have a history of syncope (40.5 vs. 22.5%, P = 0.0044), lower left ventricular ejection fraction (38.1 ± 15.2 vs. 48.8 ± 14.7%, P ≤ 0.0001), ventricular pacing on baseline electrocardiogram (16.1 vs. 2.1%, P = 0.0002), and a secondary prevention indication (60.7 vs. 24.5%, P < 0.0001) compared with those who did not receive appropriate ICD therapies. CONCLUSION: Patients with CS and ICDs are at high risk for ventricular arrhythmias. This population also has high rates of inappropriate shocks and device complications.

Lead integrity alert algorithm decreases inappropriate shocks in patients who have Sprint Fidelis pace-sense conductor fractures.

BACKGROUND: The Medtronic Sprint Fidelis high-voltage implantable cardioverter-defibrillator (ICD) lead is prone to fracture. The majority of fractures involve the pace-sense (P/S) conductors and may result in multiple inappropriate shocks. The Medtronic lead integrity alert (LIA) algorithm was designed to improve early detection of transient P/S conductor fractures and to decrease the incidence and number of inappropriate shocks. OBJECTIVE: The purpose of this prospective single-center study was to assess the effectiveness of the LIA algorithm for warning patients of an impending Sprint Fidelis P/S conductor fracture and for decreasing the incidence and number of inappropriate shocks. METHODS: The study population included all patients who had Sprint Fidelis leads and Medtronic ICD pulse generators that were implanted and followed at the Minneapolis Heart Institute. Patients were evaluated in the clinic every 3 to 4 months or by remote monitoring using the Medtronic CareLink system. When the LIA algorithm was released in August 2008, the RAMware was downloaded to the pulse generator of all patients with the Sprint Fidelis lead. Patients and family members received educational materials and were given a demonstration of the audible alerts. RESULTS: Between October 2004 and January 2010, 52 (11.3%) of 461 Sprint Fidelis leads failed in the study population. Inappropriate shocks were the first sign of lead failure in 18 (69%) of the 26 patients who did not have the LIA compared to 4 (17%) of 23 patients who had the LIA (P = .0004). Patients who experienced inappropriate shocks without the LIA received an average of 13.2 +/- 13.6 inappropriate shocks (range 2-54) versus 3.0 +/- 2.0 inappropriate shocks (range 2-6) in patients who had the LIA (P = .017). The audible alert was effective in 70% (16/23) and 35% (6/17) of patients with and without the LIA, respectively, whose alerts were programmed ON (P = .053). Overall, 8 (32%) of 25 patients whose audible alerts were triggered did not immediately hear or recognize the tone. CONCLUSION: The LIA appears to be an effective method for detecting most Sprint Fidelis lead fractures and for decreasing the incidence and number of inappropriate shocks. However, a better method for alerting patients and caregivers is needed.

Deaths and cardiovascular injuries due to device-assisted implantable cardioverter-defibrillator and pacemaker lead extraction.

AIMS: An estimated 10,000-15,000 pacemaker and implantable cardioverter-defibrillator (ICD) leads are extracted annually worldwide using specialized tools that disrupt encapsulating fibrous tissue. Additional information is needed regarding the safety of the devices that have been approved for lead extraction. The aim of this study was to determine whether complications due to device-assisted lead extraction might be more hazardous than published data suggest, and whether procedural safety precautions are effective. METHODS AND RESULTS: We searched the US Food and Drug Administration's (FDA) Manufacturers and User Defined Experience (MAUDE) database from 1995 to 2008 using the search terms 'lead extraction and death' and 'lead extraction and injury'. Additional product specific searches were performed for the terms 'death' and 'injury'. Between 1995 and 2008, 57 deaths and 48 serious cardiovascular injuries associated with device-assisted lead extraction were reported to the FDA. Owing to underreporting, the FDA database does not contain all adverse events that occurred during this period. Of the 105 events, 27 deaths and 13 injuries occurred in 2007-2008. During these 2 years, 23 deaths were linked with excimer laser or mechanical dilator sheath extractions. The majority of deaths and injuries involved ICD leads, and most were caused by lacerations of the right atrium, superior vena cava, or innominate vein. Overall, 62 patients underwent emergency surgical repair of myocardial perforations and venous lacerations and 35 (56%) survived. CONCLUSION: These findings suggest that device-assisted lead extraction is a high-risk procedure and that serious complications including death may not be mitigated by emergency surgery. However, skilled standby cardiothoracic surgery is essential when performing pacemaker and ICD lead extractions. Although the incidence of these complications is unknown, the results of our study imply that device-assisted lead extractions should be performed by highly qualified physicians and their teams in specialized centres.

Long-term survival after cardiac arrest in hypertrophic cardiomyopathy.

BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) and aborted cardiac arrest are generally regarded as a high-risk subgroup susceptible to future major cardiac events and an unfavorable prognosis. However, outcome over extended time periods after major arrhythmic events is unresolved in such HCM patients. OBJECTIVE: This study sought to more completely define the natural history of HCM. METHODS: Of 916 HCM patients in the Minneapolis Heart Institute registry, 39 experienced either cardiac arrest (n = 21) or an appropriate shock from a prophylactically implanted cardioverter-defibrillator (ICD) (n = 18), and were assessed prospectively. RESULTS: Age at initial arrhythmic event was 34 +/- 17 years (range 8 to 68; 67% <40 years). Of the 39 study patients, 32 (82%) survived after their initial cardiac event (for 9.4 +/- 7.6 years; up to 30 years), including 14 patients for >or=10 years (36%) and 4 patients >or=20 years (10%). Of the 32 survivors, 15 (47%) have not experienced subsequent events, and 17 (53%) had >or=1 additional cardiac arrest or appropriate ICD intervention. Annual HCM-related mortality was 1.4%, similar to general HCM populations, and 88% of patients were free of HCM-related death over the follow-up period. Survival from potentially lethal arrhythmias was associated with no or only mild heart failure symptoms in 29 of 32 patients (91%) at most recent evaluation. CONCLUSION: In HCM, long-term survival up to 30 years may follow cardiac arrest with or without ICD intervention. Disabling heart failure symptoms were uncommon after these arrhythmic events, at last follow-up. These novel observations regarding the natural history of HCM underscore the unpredictability of the arrhythmogenic substrate, which may remain dormant over extended periods of time.

Clinical outcome and phenotypic expression in LAMP2 cardiomyopathy.

CONTEXT: Mutations in X-linked lysosome-associated membrane protein gene (LAMP2; Danon disease) produce a cardiomyopathy in young patients that clinically mimics severe hypertrophic cardiomyopathy (HCM) due to sarcomere protein mutations. However, the natural history and phenotypic expression of this newly recognized disease is incompletely resolved and its identification may have important clinical implications. OBJECTIVES: To determine the clinical consequences, outcome, and phenotypic expression of LAMP2 cardiomyopathy associated with diagnostic and management strategies. DESIGN, SETTING, AND PATIENTS: Clinical course and outcome were assessed prospectively in 7 young patients (6 boys) with defined LAMP2 mutations from the time of diagnosis (age 7-17 years; median, 14 years) to October 2008. Phenotypic expression of this disease was assessed both clinically and at autopsy. MAIN OUTCOME MEASURES: Progressive heart failure, cardiac death, and transplant. RESULTS: Over a mean (SD) follow-up of 8.6 (2.6) years, and by age 14 to 24 years, the study patients developed left ventricular systolic dysfunction (mean [SD] ejection fraction, 25% [7%]) and cavity enlargement, as well as particularly adverse clinical consequences, including progressive refractory heart failure and death (n = 4), sudden death (n = 1), aborted cardiac arrest (n = 1), or heart transplantation (n = 1). Left ventricular hypertrophy was particularly marked (maximum thickness, 29-65 mm; mean [SD], 44 [15] mm), including 2 patients with massive ventricular septal thickness of 60 mm and 65 mm at ages 23 and 14 years, respectively. In 6 patients, a ventricular pre-excitation pattern at study entry was associated with markedly increased voltages of R-wave or S-wave (15-145 mm; mean [SD], 69 [39] mm), and deeply inverted T-waves. Autopsy findings included a combination of histopathologic features that were consistent with a lysosomal storage disease (ie, clusters of vacuolated myocytes) but also typical of HCM due to sarcomere protein mutations (ie, myocyte disarray, small vessel disease, myocardial scarring). CONCLUSIONS: LAMP2 cardiomyopathy is a profound disease process characterized by progressive clinical deterioration leading rapidly to cardiac death in young patients (<25 years). These observations underscore the importance of timely molecular diagnosis for predicting prognosis and early consideration of heart transplantation.

Failure of impedance monitoring to prevent adverse clinical events caused by fracture of a recalled high-voltage implantable cardioverter-defibrillator lead.

BACKGROUND: The Medtronic Sprint Fidelis implantable cardioverter-defibrillator high-voltage lead is prone to fracture. The October 2007 safety advisory recommended lead impedance monitoring to aid in identifying lead fractures. OBJECTIVE: The aim of this single-center study was to examine the effectiveness of impedance monitoring for detecting Sprint Fidelis lead failures before they caused adverse clinical events such as inappropriate shocks. METHODS: Impedance and sensing information were acquired during routine clinic and CareLink follow-up and at the time of lead failure using the Patient Alert, sensing integrity counter, nonsustained episode, and electrogram features in Medtronic pulse generators. RESULTS: Between September 2004 and February 2008, 17 of 514 Sprint Fidelis leads (3.3%) followed up at our center failed between 11 and 35 months after implantation (mean 23.0 +/- 8.0 months). Fifteen of these failures (88%) were caused by pace-sense conductor fractures, and 2 (12%) were caused by high-voltage conductor defects. Twelve of 15 patients (80%) with pace-sense conductor fractures received inappropriate shocks; of these, 4 had no significant increase in lead impedance before they were shocked, 2 were shocked <3 hours after their lead impedances exceeded the 1,000 Omega audible alert threshold, and 2 patients did not hear the alarm. All pace-sense conductor failures whose sensing function could be evaluated (13 of 15) had oversensing based on stored data, and oversensing usually (11 of 13) preceded impedances changes. CONCLUSION: Impedance monitoring did not prevent inappropriate shocks in two-thirds of our patients. Thus, pace-sense conductor impedance monitoring as currently implemented does not reliably forewarn patients of a lead malfunction. Consequently, patients who have Sprint Fidelis leads remain at risk for adverse clinical events associated with pace-sense conductor fracture.

Significance of appropriate defibrillator shock 3 hours and 20 minutes following implantation in a patient with hypertrophic cardiomyopathy.

INTRODUCTION: Implantable defibrillators have proved effective in terminating potentially life-threatening ventricular tachyarrhythmias in hypertrophic cardiomyopathy (HCM), although the timing of appropriate shocks may be exceedingly variable. METHODS AND RESULTS: We report an unusual occurrence in a 48-year-old woman with nonobstructive HCM who experienced an appropriate shock for ventricular fibrillation only 3 hours and 20 minutes after implantation. Careful review of the clinical circumstances failed to define a specific mechanism related to the implant procedure that could have triggered the potentially lethal arrhythmia. CONCLUSION: Early device interventions are not uncommon in HCM, but (as in this case) appear unrelated to mechanisms other than the unpredictable and underlying arrhythmogenic substrate in this disease.

Implantable cardioverter-defibrillators and prevention of sudden cardiac death in hypertrophic cardiomyopathy.

CONTEXT: Recently, the implantable cardioverter-defibrillator (ICD) has been promoted for prevention of sudden death in hypertrophic cardiomyopathy (HCM). However, the effectiveness and appropriate selection of patients for this therapy is incompletely resolved. OBJECTIVE: To study the relationship between clinical risk profile and incidence and efficacy of ICD intervention in HCM. DESIGN, SETTING, AND PATIENTS: Multicenter registry study of ICDs implanted between 1986 and 2003 in 506 unrelated patients with HCM. Patients were judged to be at high risk for sudden death; had received ICDs; underwent evaluation at 42 referral and nonreferral institutions in the United States, Europe, and Australia; and had a mean follow-up of 3.7 (SD, 2.8) years. Measured risk factors for sudden death included family history of sudden death, massive left ventricular hypertrophy, nonsustained ventricular tachycardia on Holter monitoring, and unexplained prior syncope. MAIN OUTCOME MEASURE: Appropriate ICD intervention terminating ventricular tachycardia or fibrillation. RESULTS: The 506 patients were predominately young (mean age, 42 [SD, 17] years) at implantation, and most (439 [87%]) had no or only mildly limiting symptoms. ICD interventions appropriately terminated ventricular tachycardia/fibrillation in 103 patients (20%). Intervention rates were 10.6% per year for secondary prevention after cardiac arrest (5-year cumulative probability, 39% [SD, 5%]), and 3.6% per year for primary prevention (5-year probability, 17% [SD, 2%]). Time to first appropriate discharge was up to 10 years, with a 27% (SD, 7%) probability 5 years or more after implantation. For primary prevention, 18 of the 51 patients with appropriate ICD interventions (35%) had undergone implantation for only a single risk factor; likelihood of appropriate discharge was similar in patients with 1, 2, or 3 or more risk markers (3.83, 2.65, and 4.82 per 100 person-years, respectively; P = .77). The single sudden death due to an arrhythmia (in the absence of advanced heart failure) resulted from ICD malfunction. ICD complications included inappropriate shocks in 136 patients (27%). CONCLUSIONS: In a high-risk HCM cohort, ICD interventions for life-threatening ventricular tachyarrhythmias were frequent and highly effective in restoring normal rhythm. An important proportion of ICD discharges occurred in primary prevention patients who had undergone implantation for a single risk factor. Therefore, a single marker of high risk for sudden death may be sufficient to justify consideration for prophylactic defibrillator implantation in selected patients with HCM.

Early failure of a small-diameter high-voltage implantable cardioverter-defibrillator lead.

BACKGROUND: We have observed a higher than expected rate of Sprint Fidelis model 6949 lead failures in our practice. OBJECTIVE: The aim of this study was to assess the performance of small-diameter Sprint Fidelis high-voltage ICD leads. METHODS: The actuarial survival of Sprint Fidelis model 6949 leads implanted at our center was compared with that of the Sprint Quattro Secure model 6947. The United States Food and Drug Administration Manufacturers and User Facility Device Experience (MAUDE) database was searched for Sprint Fidelis models. RESULTS: The survival of 583 Sprint Fidelis 6949 leads implanted at our center between September 2004 and February 2007 was significantly less than 285 Sprint Quattro Secure model 6947 leads implanted by us between November 2001 and February 2007 (P = .005). Six patients presented with Sprint Fidelis lead failure 4-23 months after implant. Five of the six patients experienced multiple inappropriate shocks associated with pace-sense conductor and coil fractures; the sixth patient had a fixation mechanism failure. The MAUDE search rendered reports for 679 Sprint Fidelis leads. The most frequent complaints or observations were inappropriate shocks (33%), high impedance (33%), and fracture (35%). Of 125 leads analyzed by the manufacturer, 62 involved fracture of the pace-sense conductor or coil and the high-voltage (defibrillation) conductor. CONCLUSIONS: The Sprint Fidelis high-voltage lead appears to be prone to early failure. Its use should be limited until the failure mechanism is identified and corrected. Patients should be evaluated quarterly, and automatic lead test features should be enabled. While more data are needed, routine prophylactic replacement of intact, normally functioning Sprint Fidelis leads does not appear justified.

Clinical experience with pacemaker pulse generators and transvenous leads: an 8-year prospective multicenter study.

BACKGROUND: Pacemakers have improved the lives of patients worldwide. Unfortunately, the medical community has had little independent information regarding the performance of these vital medical devices. OBJECTIVES: The purpose of this study was to examine the reasons pacemaker pulse generators and transvenous leads were removed from service. We evaluated the causes and major adverse clinical events associated with device end-of-service life behavior and how they were detected and managed. METHODS: Pulse generator and lead data were entered prospectively using a web-based format. Normal battery depletion was signified by the elective replacement indicator appearing >3 years after implant. Lead failure was a device defect causing pacing, sensing, or fixation malfunction, high threshold, or abnormal impedance. Major adverse clinical events were death, angina, heart failure, syncope, and perioperative surgical complications. RESULTS: From 1998 to 2006, 2,652 pulse generator and 615 leads were removed from service. The average pulse generator was implanted for 7.3 +/- 3.1 years (range <1 day to 26 years). The majority of pulse generators (n = 2,317 [87%]) were replaced for normal battery depletion. Severe and accelerated battery depletion, manufacturers' advisories, and electronic or connector defects accounted for 13% of pulse generator removals. The proportion of pulse generators removed from service as a result of manufacturers' advisories, electronic failure, and housing defects were 4%, 2%, and 1%, respectively. Models with rate response capability had shorter battery longevities than those without rate response capability. Major adverse clinical events due to pulse generator end-of-service life behavior were related to electronic and connector defects, and both normal and severe battery depletion. Median time to lead failure was 7.2 +/- 5.2 years. Insulation defects caused the majority of lead failures, and most of these leads used polyurethane materials. Lead failure was associated with a 16% incidence of major adverse clinical events. No major adverse clinical events occurred when impending lead failure was detected at routine follow-up. Lead extraction was associated with a 5.6% complication rate, including one death. CONCLUSION: Overall pulse generator performance was satisfactory. Differences in battery longevity were observed among models. In some patients, elective replacement indicators signifying normal battery depletion resulted in major adverse clinical events. Pacemaker follow-up effectively identified pulse generator end-of-service life and often detected impending lead failure, thus avoiding major adverse clinical events. Long-term studies are needed to assess chronic lead performance so that appropriate clinical management strategies, including recommendations for lead extraction, can be developed.

Cardioverter-defibrillator implantation in high-risk patients with hypertrophic cardiomyopathy.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are used with increasing frequency in hypertrophic cardiomyopathy (HCM) patients of all ages for primary and secondary sudden death prevention. Concerns may arise regarding the safety of device implantation because of unique clinical and phenotypic expressions of HCM. OBJECTIVES: The purpose of this study was to assess the efficacy and safety of ICD placement in high-risk patients with HCM. METHODS: We analyzed the experience with ICDs and transvenous lead systems in 75 consecutive HCM patients at the Minneapolis Heart Institute from 1993 to 2004. RESULTS: The age of the study group patients was 12 to 79 years (mean 36 +/- 16). Patients received ICDs for secondary (n = 4, after cardiac arrest) or primary prevention (n = 71, with > or = 1 risk factor). Thirty-one patients demonstrated disease features that potentially impacted methodology and safety of the implant procedure, most commonly massive left ventricular (LV) hypertrophy and outflow obstruction > or = 50 mmHg. There were no procedure-related deaths; defibrillator implants were successful and uneventful in 71 of 75 patients (95%). In 3 of the 75 patients (4%), defibrillation was unsuccessful because of high thresholds, associated with extreme hypertrophy (wall thickness > 45 mm) and/or ongoing amiodarone therapy. In two of these patients, thoracotomy with epicardial lead placement achieved successful defibrillation; ICD therapy was abandoned in the other patient. CONCLUSION: ICD placement in children and adults with HCM is generally safe and effective. However, in some patients with massive LV hypertrophy and/or prior administration of amiodarone, transvenous defibrillation proved difficult, and epicardial lead placement was required. High-energy ICD devices and defibrillation threshold testing are recommended for most high-risk HCM patients.