Long-term follow-up of sudden cardiac arrest survivors and electrophysiologically guided antiarrhythmic therapy.

Sudden cardiac arrest survivors have a high risk of suffering from recurrent arrhythmic events. Recent studies have shown that these patients have a significantly decreased mortality rate, if they are supplied with an implantable cardioverter/defibrillator (ICD). The aim of this study was to evaluate the long-term prognosis of patients with electrophysiologically guided antiarrhythmic drug therapy in comparison to patients with ICD. 204 consecutive survivors of sudden cardiac arrest were enrolled in this study. All patients were examined with an initial electrophysiologic study (EPS) with programmed ventricular stimulation. Patients were treated with antiarrhythmic drugs (if the inducible tachycardia was suppressed) or with the implantation of an ICD. The maximal follow-up period was 120 months, the mean period was 53.3 +/- 31.4 months (ICD) versus 60.3 +/- 35.5 months (EPS, nonsignificant). Patients with ICD showed an overall mortality rate of 14.6%, whereas EPS-guided patients had a mortality rate of 43.2% (p < 0.001). The cardiac and arrhythmogenic mortality rates were significantly lower in the ICD group (12 vs. 43%, p < 0.01, and 1 vs. 16%, p < 0.001, respectively). A reduction of the mortality risk was observed in the ICD group by up to 61% (all-cause mortality), 52% (cardiac mortality) and 97.2% (arrhythmogenic mortality). In arrhythmic event survivors with ICD, arrhythmic and overall mortality rates are significantly lower compared to patients with an EPS-guided drug therapy. In the secondary prevention of sudden cardiac death, ICD should be the first choice of antiarrhythmic therapy.

Chemoreflex sensitivity as a predictor of arrhythmia relapse in ICD recipients.

BACKGROUND: The chemoreflex sensitivity as a marker of a disturbed vagal reflex activity has proved to be a parameter of increased risk for ventricular tachyarrhythmias or sudden cardiac death. The sensitivity of patients with prior myocardial infarction concerning ventricular tachyarrhythmias amounted to about 70%. This prospective study should evaluate the positive predictive accuracy of this new method in patients at risk for ventricular arrhythmias. METHODS: 42 patients were enrolled into this study. All had a prior myocardial infarction at least 6 months previously; 35 patients were resuscitated from sudden cardiac death, and seven patients had documented monomorphic ventricular tachycardias. All patients were recipients of an ICD. The chemoreflex sensitivity was measured by determination of the venous partial pressure of oxygen and the heart rate before and after inhalation of pure oxygen. The difference in the RR-intervals before and after inhalation divided by the difference in the oxygen pressures were calculated as the chemoreflex sensitivity [ms/mmHg]. Furthermore, in all patients additional risk stratifiers used in this study were the presence of ventricular late potentials (LP), the short-term heart rate variability (HRV), the baroreflex sensitivity (BRS) and a decreased left ventricular function (ejection fraction<40%, EF). RESULTS: The chemoreflex sensitivity in the patient group as a whole amounted to 2.59+/-2.06 ms/mmHg. During follow-up, out of the 42 patients enrolled, 20 had a documented arrhythmic event (AE: sustained ventricular tachycardia or ventricular fibrillation). Patients with and without AE showed significantly different values of chemoreflex sensitivity (1.58+/-1.09 vs. 3.51+/-2.31 ms/mmHg, P<0.01) and EF (33.3+/-15.6 vs. 47.9+/-17.9%, P<0.05), but not of LP, HRV or BRS. The relative risk of reduced chemoreflex sensitivity concerning an AE amounted to 2.83 (95% CI 0.99-8.01). CONCLUSIONS: The chemoreflex sensitivity as a marker of increased risk for ventricular tachyarrhythmias shows a high positive predictive power in patients with prior myocardial infarction and who previously survived ventricular tachyarrhythmias. These results should be confirmed by studies in broad populations and without survived arrhythmic event.