We investigated the risk factors for appropriate and inappropriate implantable cardioverter-defibrillator (ICD) shocks and mortality in 549 patients (mean age 74 years) with heart failure and ICDs. During a mean follow-up of 1,243 ± 655 days, of the 549 patients, 163 (30%) had appropriate ICD shocks, 71 (13%) had inappropriate ICD shocks, and 63 (12%) died. Stepwise logistic regression analysis showed that significant independent prognostic factors for appropriate ICD shocks were smoking (odds ratio 3.7) and statins (odds ratio 0.54). The significant independent prognostic factors for inappropriate ICD shocks were atrial fibrillation (odds ratio 6.2) and statins (odds ratio 0.52). Finally, those for the interval to mortality were age (hazard ratio 1.08/1-year increase), angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (hazard ratio 0.25), atrial fibrillation (hazard ratio 4.1), right ventricular pacing (hazard ratio 3.6), digoxin (hazard ratio 2.9), hypertension (hazard ratio 5.3), and statins (hazard ratio 0.32). In conclusion, in patients with heart failure and ICDs, smoking increased and statins reduced appropriate ICD shocks, atrial fibrillation increased and statins reduced inappropriate ICD shocks, and the interval to mortality was increased by age, atrial fibrillation, right ventricular pacing, hypertension, and digoxin and reduced by angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and statins.
Smoking is associated with a greater incidence of appropriate implantable cardioverter-defibrillator (ICD) shocks in patients with ICDs, and statin use reduces the incidence of appropriate ICD shocks in these patients. In the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II, one or more inappropriate ICD shocks occurred in 83 (12%) of 719 patients. Atrial fibrillation triggered 44% of inappropriate ICD shocks and supraventricular tachycardia (36%) of inappropriate ICD shocks in that study. We report on the risk factors for appropriate ICD shocks, inappropriate ICD shocks, and the interval to all-cause mortality during 1,243 days of follow-up for 549 patients (mean age 74 years) with heart failure and ICDs.
Methods
We investigated, in an observational, single-center study, the risk factors for appropriate ICD shocks, inappropriate ICD shocks, and interval to all-cause mortality in 434 men and 115 women (mean age 74 years) with heart failure and ICDs. Of the 549 patients, 322 (59%) had ischemic cardiomyopathy and 227 (41%) had nonischemic cardiomyopathy.
The left ventricular ejection fraction was measured from 2-dimensional echocardiograms, as previously described. At follow-up every 3 months, the ICD was interrogated to determine whether any shocks had occurred. The shocks were further evaluated by 2 electrophysiologists viewing the intracardiac electrocardiograms for appropriate shocks (ventricular tachycardia/ventricular fibrillation) or inappropriate shocks (shocks not resulting from ventricular tachycardia/ventricular fibrillation) and their causes.
The mean follow-up was 1,243 ± 655 days.
Student’s t tests were used to analyze continuous variables. A p value <0.05 by 2-sided t tests was considered significant. Chi-square tests and Fisher’s exact tests were used to analyze dichotomous variables. Stepwise logistic regression analysis was performed for appropriate ICD shocks, and inappropriate ICD shocks, and stepwise Cox regression analysis for the interval to mortality using the variables age, gender, ischemic cardiomyopathy, nonischemic cardiomyopathy, atrial fibrillation, left ventricular ejection fraction, biventricular pacing, right ventricular pacing, dual chamber pacing, QRS duration, New York Heart Association class, smoking, systemic hypertension, diabetes mellitus, dyslipidemia, and the use of statins, β blockers, angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers, amiodarone, sotalol, and digoxin.
Results
Of 549 patients, 163 (30%) had appropriate ICD shocks, 71 (13%) had inappropriate ICD shocks, and 63 (12%) died. Table 1 lists the baseline characteristics of patients with and without inappropriate shocks and the levels of statistical significance. The mean follow-up was 1,243 ± 655 days.
| Variable | Inappropriate Shocks | p Value | |
|---|---|---|---|
| Yes (n = 71) | No (n = 478) | ||
| Gender | NS | ||
| Women | 16 (23%) | 99 (21%) | |
| Men | 55 (77%) | 379 (79%) | |
| Age (years) | 75 ± 6 | 73 ± 10 | 0.038 |
| Ischemic cardiomyopathy | 45 (63%) | 277 (58%) | NS |
| Nonischemic cardiomyopathy | 26 (37%) | 201 (42%) | NS |
| Atrial fibrillation | 29 (41%) | 41 (9%) | <0.0001 |
| Left ventricular ejection fraction | 28 ± 8 | 29 ± 7 | NS |
| Biventricular pacing | 23 (32%) | 186 (39%) | NS |
| Right ventricular pacing | 48 (62%) | 292 (61%) | NS |
| Dual chamber pacing | 45 (63%) | 322 (67%) | NS |
| QRS duration (ms) | 117 ± 21 | 118 ± 19 | NS |
| New York Heart Association class | NS | ||
| II or III | 49 (69%) | 328 (69%) | |
| IV | 22 (31%) | 150 (31%) | |
| Smoker | 17 (24%) | 92 (19%) | NS |
| Systemic hypertension | 37 (52%) | 214 (45%) | NS |
| Diabetes mellitus | 13 (18%) | 99 (21%) | NS |
| Dyslipidemia ⁎ | 39 (55%) | 285 (60%) | NS |
| Statins | 22 (31%) | 257 (54%) | <0.0001 |
| β Blockers | 49 (69%) | 324 (68%) | NS |
| Angiotensin-converting enzyme inhibitors/angiotensin receptor blockers | 50 (70%) | 304 (64%) | NS |
| Amiodarone | 18 (25%) | 94 (20%) | NS |
| Sotalol | 5 (7%) | 19 (4%) | NS |
| Digoxin | 25 (35%) | 137 (29%) | NS |
| Follow-up (days) | 1,241 ± 555 | 1,243 ± 670 | NS |
⁎ Dyslipidemia indicated by serum total cholesterol ≥200 mg/dl, serum low-density lipoprotein cholesterol ≥100 mg/dl, serum high-density lipoprotein cholesterol <40 mg/dl, serum triglycerides ≥150 mg/dl, or use of lipid-lowering drug therapy.
Appropriate ICD shocks occurred in 33 (46%) of 71 patients who had inappropriate ICD shocks and in 130 (27%) of 478 patients who had no inappropriate ICD shocks (p <0.0001). Of the 71 patients with inappropriate ICD shocks, 16 (23%) died and of the 478 patients who had no inappropriate ICD shocks, 47 (10%) died (p = 0.002).
A total of 187 inappropriate shocks occurred in the 71 patients with inappropriate shocks. Of the 187 inappropriate shocks, 109 (58%) were triggered by atrial fibrillation with a rapid ventricular rate, 64 (34%) were triggered by supraventricular tachycardia and 14 (7%) by sinus tachycardia with a ventricular rate >150 beats/min. The data listed in Table 2 showed that atrial fibrillation (odds ratio 6.2) and statins (odds ratio 0.54) were significant independent risk factors for inappropriate ICD shocks.
| Prognostic Factor | Parameter Estimate | SE | p Value | Odds Ratio | 95% Confidence Interval |
|---|---|---|---|---|---|
| Atrial fibrillation | 0.915 | 0.150 | <0.0001 | 6.238 | 3.470–11.22 |
| Statins | −0.323 | 0.144 | 0.025 | 0.524 | 0.298–0.922 |
The data listed in Table 3 showed that smoking (odds ratio 3.7) and statins (odds ratio 0.54) were significant independent risk factors for appropriate ICD shocks. The data listed in Table 4 showed that significant independent risk factors for the interval to all-cause mortality were age (hazard ratio 1.08/1-year increase), ACE inhibitors/angiotensin receptor blockers (hazard ratio 0.25), atrial fibrillation (hazard ratio 4.1), right ventricular pacing (hazard ratio 3.6), digoxin (hazard ratio 2.9), systemic hypertension (hazard ratio 5.3), and statins (hazard ratio 0.32).
| Prognostic Factor | Parameter Estimate | SE | p Value | Odds Ratio | 95% Confidence Interval |
|---|---|---|---|---|---|
| Smoking | 0.648 | 0.113 | <0.0001 | 3.656 | 2.352–5.682 |
| Statins | −0.307 | 0.098 | 0.002 | 0.542 | 0.368–0.797 |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
