Elevated γ-glutamyltransferase in implantable cardioverter defibrillator patients.

BACKGROUND: Elevated γ-glutamyltransferase (GGT) is a new risk factor for cardiovascular diseases, but its impact on ventricular tachyarrhythmia occurrence and survival in patients with an implantable cardioverter defibrillator (ICD) is unknown. METHODS AND RESULTS: Considering that GGT levels are gender-dependent, female ICD recipients were excluded from our database because of the low incidence of events. In a retrospective analysis, appropriate ICD therapy (both shocks and antitachycardia pacing due to ventricular tachyarrhythmias) occurred in 31.9% of 320 male patients who had received an ICD for primary prevention (median follow-up of 2.3 years), and in 55.1% of 423 male patients who had received an ICD for secondary prevention (median follow-up of 3.9 years). Compared to normal low GGT plasma levels (below 28 U/L), total mortality but not risk for appropriate ICD therapy was elevated for higher GGT categories (p for trend = 0.004 in primary prevention and p for trend = 0.002 in secondary prevention, respectively). In Cox regression analysis, elevated GGT (>56 U/L) remained an independent predictor of death both in primary (p = 0.011) and in secondary prevention (p = 0.006). Patients with elevated GGT and renal insufficiency defined by an estimated glomerular filtration rate <60 ml/min/1.73 m(2) suffered from excess total mortality jeopardizing the benefit of ICD therapy. CONCLUSION: Elevation of GGT is an important adverse prognostic parameter in ICD patients. A possible role of GGT for improved patient selection for ICD therapy deserves further investigation.

Comparison of benefit and mortality of implantable cardioverter-defibrillator therapy in patients aged ≥75 years versus those <75 years.

Implantable cardioverter-defibrillator (ICD) therapy decreases arrhythmic and all-cause mortality in patients at high risk of sudden death. However, its clinical benefit in elderly patients is uncertain. The aim of this study was to assess the long-term efficacy of ICD treatment in elderly patients and to identify markers of successful ICD therapy and risk factors of mortality. We performed multivariate analysis of a prospective long-term database from 2 tertiary care centers including 936 consecutive patients with an ICD. Predictors of ICD therapy and risk factors for mortality were assessed in patients ≥75 years old at ICD implantation compared to younger patients. Mean follow-up time was 43 ± 40 months. Rates of ICD therapy were similar in the 2 age groups. No significant predictors of ICD therapy could be identified in older patients. Median estimated survival was 132 months in patients <75 years and 81 months in those ≥75 years old (p = 0.006). Decreased ejection fraction (hazard ratio 1.62 per 10% decrease, p = 0.03) and impaired renal function (hazard ratio 1.57 per 10 ml/kg/m(2) decrease in estimated glomerular filtration rate, p = 0.02) were independent risk factors of mortality in patients ≥75 years old. However, mortality of older patients was similar to that of the age-matched general population irrespective of delivery of ICD therapy. In conclusion, ICD therapy is effective for treatment of life-threatening arrhythmias in all age groups. However, prevention of sudden cardiac death may have limited impact on overall mortality in older patients. Despite a similar rate of appropriate ICD therapies, risk of death is increased 1.6-fold in ICD recipients ≥75 years old compared to younger patients. Patients with decreased ejection fraction and impaired renal function are at highest risk.

Appropriate therapy but not inappropriate shocks predict survival in implantable cardioverter defibrillator patients.

BACKGROUND: Inappropriate implantable cardioverter defibrillator (ICD) shocks have been linked to a worse clinical outcome due to direct myocardial injury. HYPOTHESIS: The occurrence of ventricular tachyarrhythmia indicating progression of the underlying heart disease, but not the ICD shock itself, has prognostic impact in clinical routine. METHODS: In a retrospective study, 1117 recipients of an ICD were analyzed with respect to appropriate and inappropriate therapies and survival. RESULTS: During a mean follow-up of 2.92 years, appropriate therapy occurred in 27.7% and 54.0% of patients who had received an ICD for primary and secondary prevention of sudden cardiac death (SCD), respectively (P<0.0001). Inappropriate shock therapy occurred in 15.0% and 25.4% of patients who had received an ICD for primary and secondary prevention of SCD, respectively (P = 0.122). Appropriate ICD therapy had a strong impact on overall survival (P<0.0001), and this association was found both in primary (P<0.0001) and secondary (P = 0.002) prevention of SCD. Inappropriate ICD shocks had no impact on total mortality, neither in primary nor secondary prevention of SCD. CONCLUSIONS: Inappropriate shocks do not affect survival, in strong contrast to appropriate ICD therapy. Our study does not support the hypothesis that shock therapy in itself worsens clinical outcome. However, it confirms that appropriate ICD therapy is a warning sign and should prompt physicians to consider additional treatment strategies.