Life expectancy gains and cost-effectiveness of implantable cardioverter/defibrillators for the primary prevention of sudden cardiac death in patients with hypertrophic cardiomyopathy.

BACKGROUND: Sudden cardiac death (SCD) is a devastating complication of hypertrophic cardiomyopathy (HCM). The optimal strategy for the primary prevention of SCD in HCM remains controversial. METHODS: Using a Markov model, we compared the health benefits and cost-effectiveness of 3 strategies for the primary prevention of SCD: implantable cardioverter/defibrillator (ICD) insertion, amiodarone therapy, or no therapy. We modeled hypothetical cohorts of 45-year-old patients with HCM with no history of cardiac arrest but at significant risk of SCD (3%/y). RESULTS: Over a lifetime, compared with no therapy, ICD therapy increased quality-adjusted survival by 4.7 quality-adjusted life years (QALYs) at an additional cost of $142,800 ($30,000 per QALY), whereas amiodarone increased quality-adjusted survival by 2.8 QALYs at an additional cost of $104,900 ($37,300 per QALY). Compared with no therapy, ICD therapy would cost < $50,000 per QALY for patients (i) aged 25, with > or = 1 risk factors for SCD, and (ii) aged 45 or 65, with > or = 2 risk factors for SCD. CONCLUSIONS: An ICD strategy is projected to yield the greatest increase in quality-adjusted life expectancy of the 3 treatment strategies evaluated. Combined consideration of age and the number of risk factors for SCD may allow more precise tailoring of ICD therapy to its expected benefits.

Determinants of implantable defibrillator discharges in high-risk patients with hypertrophic cardiomyopathy.

OBJECTIVES: To identify the determinants of appropriate and inappropriate implantable cardioverter-defibrillator (ICD) discharges in patients with hypertrophic cardiomyopathy (HCM). DESIGN: Retrospective cohort study. SETTING: ICD clinic at an academic hospital. PATIENTS: 61 patients with HCM who received ICDs for the primary or secondary prevention of sudden cardiac death (SCD). OUTCOME MEASURES: (a) Analysis of appropriate and inappropriate ICD discharges; (b) predictors of ICD discharges. RESULTS: Mean (SD) age at ICD insertion was 46 (18) years (range 10-79). Follow-up time was 40 (27) months (range 7-151). Eight patients experienced an appropriate discharge, occurring 24.5 (13.6) months after ICD insertion. Appropriate ICD intervention was more common in the secondary (36%) than the primary (8%) prevention group (p = 0.02). Inappropriate ICD discharges occurred in 20 (33%) patients. Multivariate Cox regression analysis identified two significant predictors of inappropriate ICD discharges: (a) age <30 years at the time of ICD insertion (hazard ratio (HR) = 3.0 (95% CI 1.1 to 8.0; p = 0.03) and (b) history of atrial fibrillation (HR = 3.1 (95% CI 1.2 to 8.1; p = 0.02). CONCLUSIONS: ICDs are effective in the prevention of SCD in HCM. However, there is a high incidence of inappropriate ICD discharges.

Atrial overdrive pacing and incidence of heart failure-related adverse events in permanently paced patients.

BACKGROUND: Atrial overdrive pacing algorithms may be effective in preventing or suppressing atrial fibrillation (AF). However, the maintenance of a heart rate incessantly faster than spontaneous could induce left ventricular (LV) dysfunction and promote heart failure (HF) on the long term. OBJECTIVE: This post hoc analysis examined the effects of a new overdrive algorithm on the incidence of HF-related adverse events in 411 patients enrolled in the ADOPT-A trial. MATERIALS AND METHODS: The AF Suppression algorithm was randomly programmed ON in 209 patients (treatment group) versus OFF in 202 patients (control group). The incidence of HF-related adverse events and HF-related deaths over a 6-month follow-up was compared between the two groups. Patients with versus without HF-related clinical events were also compared to each other within each group. RESULTS: There were eight HF-related adverse clinical events (3.8%) in the treatment group and 11 (5.4%) in the control group, including four HF-related deaths (1.9 vs. 2.0%) in each group during follow-up. Baseline NYHA functional class in patients with versus without HF-related adverse events was 1.4 +/- 0.5 versus 1.5 +/- 0.7 in the control, and 1.5 +/- 0.8 versus 1.5 +/- 0.6 in the treatment group. LV ejection fraction (EF) was 49 +/- 7% in patients with, versus 57 +/- 12% in patients without HF-related adverse events, in the control group, and 43 +/- 14% in patients with, versus 56 +/- 13% in patients without HF-related adverse events, in the treatment group. LVEF was lowest and similar in both groups among patients who died from HF (35 +/- 10% in the control and 38 +/- 27% in the treatment group). CONCLUSIONS: In ADOPT-A, HF-related clinical events and deaths were related to LV dysfunction and not to atrial pacing overdriven by the AF suppression algorithm.

Permanent pacing after cardiac transplantation in the era of extended donors.

BACKGROUND: Early results with bicaval anastomosis have shown a decreased requirement for permanent pacing (PPM) after transplantation (Tx). It is unclear whether this remains true in the current era of extended donor criteria. The objective of the present study was to characterize the need for post-Tx PPM requirements in the current bicaval era and to determine factors associated with need for pacing. METHODS: The local cardiac Tx database, hospital records and electrophysiology laboratory database were cross-referenced for information on patients in the pre-, peri- and post-Tx period. RESULTS: Between 2000 and 2004, 88 patients received a cardiac Tx using bicaval anastomosis. At post-Tx, 18 of 88 (20.5%) patients required a PPM. The incidence of single- and dual-chamber PPM was 31.3% and 68.7%, respectively. Mean donor age for patients requiring post-Tx PPM was 44.7 +/- 15.3 years compared with 35.7 +/- 14.4 years for those with no PPM requirement (p = 0.019). For every 5-year increase in donor age the risk for post-Tx PPM increased 1.234-fold (95% confidence interval [CI] 1.022 to 1.489, p = 0.0289). Recipient age, gender, amiodarone use, year of transplant, surgeon and surgical times were not associated with PPM requirements after cardiac Tx. CONCLUSIONS: Pacing requirements after heart transplantation, in the era of extended donor criteria, exceed the previously published rates of 0% to 5%. The advantage of bicaval anastomosis in decreasing pacing needs post-Tx does not exist in the era of extended donor criteria, specifically in the older donor age group.

Cardiac resynchronization therapy: retiming the failing right ventricle.

Cardiac resynchronization therapy (CRT) improves symptoms, reduces hospitalization, and may decrease mortality in patients with moderate/severe heart failure and left bundle branch block. Whether CRT may have a role in the management of patients with adult congenital heart disease and a failing right (systemic) ventricle is unknown. We report the case of an adult patient with transposition of the great arteries and previous Mustard's repair, who successfully underwent CRT using a hybrid transvenous/epicardial approach. Exercise tolerance improved, right ventricular (systemic) ejection fraction improved, diuretic requirements reduced, and renal function improved. CRT may offer a new therapeutic option for this patient population.

Long-term outcomes of cardiac pacing in adults with congenital heart disease.

OBJECTIVES: The purpose of this retrospective study was to define long-term outcomes after pacemaker therapy in adults with congenital heart disease (CHD). BACKGROUND: Adults with CHD represent a unique and expanding population. Many will require pacemaker or implantable defibrillator therapy, with a lifelong need for re-intervention and follow-up. They pose technical and management challenges not encountered in other groups receiving pacing, and the complication and re-intervention rates specific to this population are not well-defined. METHODS: We reviewed outcomes of 168 adults with CHD, 89 females, mean age 40 years, in whom a pacemaker or anti-tachycardia device was implanted. RESULTS: Mean age at implant was 28 years with mean pacing duration 11 years at follow-up (range, 0.5 to 38.0). Seventy-two (42%) received initial dual-chamber devices and remained in this mode, while 23 (14%) went from ventricular to dual-chamber pacing in follow-up. Initial mode of pacing did not have a significant effect on subsequent atrial arrhythmia. Patients receiving an initial epicardial system were younger than those paced endocardially (17 +/- 12 years vs. 35 +/- 16 years, p < 0.001) and more likely to undergo re-intervention (p = 0.019). Difficulty with vascular access was encountered in 25 patients (15%), while 45 (27%) experienced lead-related complications. No significant predictors of lead complications were identified. CONCLUSIONS: Lead complications were not significantly different for epicardial versus endocardial, nor physiologic versus ventricular pacing, but a trend toward improved lead survival in patients receiving endocardial leads at first implant was observed. Adults with CHD remain at risk for atrial arrhythmias regardless of pacing mode.

A new pacemaker algorithm for the treatment of atrial fibrillation: results of the Atrial Dynamic Overdrive Pacing Trial (ADOPT).

OBJECTIVES: The Atrial Dynamic Overdrive Pacing Trial (ADOPT) was a single blind, randomized, controlled study to evaluate the efficacy and safety of the atrial fibrillation (AF) Suppression Algorithm (St. Jude Medical Cardiac Rhythm Management Division, Sylmar, California) in patients with sick sinus syndrome and AF. BACKGROUND: This algorithm increases the pacing rate when the native rhythm emerges and periodically reduces the rate to search for intrinsic atrial activity. METHODS: Symptomatic AF burden (percentage of days during which symptomatic AF occurred) was the primary end point. Patients underwent pacemaker implantation, were randomized to DDDR with the algorithm on (treatment) or off (control), and were followed for six months. RESULTS: Baseline characteristics and antiarrhythmic drugs used were similar in both groups. The percentage of atrial pacing was higher in the treatment group (92.9% vs. 67.9%, p < 0.0001). The AF Suppression Algorithm reduced symptomatic AF burden by 25% (2.50% control vs. 1.87% treatment). Atrial fibrillation burden decreased progressively in both groups but was lower in the treatment group at each follow-up visit (one, three, and six months) (p = 0.005). Quality of life scores improved in both groups. The mean number of AF episodes (4.3 +/- 11.5 control vs. 3.2 +/- 8.6 treatment); total hospitalizations (17 control vs. 15 treatment); and incidence of complications, adverse events, and deaths were not statistically different between groups. CONCLUSIONS: The ADOPT demonstrated that overdrive atrial pacing with the AF Suppression Algorithm decreased symptomatic AF burden significantly in patients with sick sinus syndrome and AF. The decrease in relative AF burden was substantial (25%), although the absolute difference was small (2.50% control vs. 1.87% treatment).

Experience with a dual chamber implantable defibrillator.

An implantable defibrillator with dual chamber pacing may have advantages for pacing, sensing, and detection of brady- and tachyarrhythmias. This study evaluates the safety and performance of a dual chamber implantable cardioverter defibrillator that incorporates an algorithm to discriminate supraventricular from ventricular arrhythmias. The 300 patients in this study had the device implanted for the following indications: ventricular tachycardia (47%), sudden cardiac death survivorship (51%), and prophylactic implants (2%). Patients received dual chamber pacing for accepted bradyarrhythmic (51.7%) or investigational indications. During a mean follow-up period of 1.7 months a total of 1,092 arrhythmia episodes in 96 patients were fully documented in the device memory: 66 patients experienced a total of 796 ventricular tachyarrhythmia episodes and 42 experienced a total of 296 supraventricular episodes. The device appropriately detected 100% of sustained ventricular tachyarrhythmias while reducing the inappropriate detection of supraventricular tachyarrhythmias by 72% compared to single chamber rate only detection. The positive predictive value was 90.5% for ventricular tachyarrhythmia detection in episodes that exceeded the tachycardia detection rate. Adverse events observed in at least 2% of the patients were incisional pain (22%), inappropriate ventricular detection (7%), atrial lead dislodgement (4%), atrial oversensing/undersensing (3%), hematoma (3%), incessant ventricular tachyarrhythmia (2%), and pneumothorax (2%). There were 13 deaths, none of which were attributed to device failure. The Gem DR is safe and effective for the detection and treatment of ventricular tachyarrhythmias. The dual chamber detection algorithm appropriately recognized supraventricular tachycardia with rapid ventricular rates 72% of the time while maintaining 100% detection of sustained ventricular tachyarrhythmias.