Determinants of patient survival rate after implantation of a cardioverter-defibrillator without resynchronisation capability

Abstract

Background: Proper selection of patients at high risk for sudden cardiac death (SCD) and increasing use of implantable cardioverter-defibrillators (ICD) may contribute to improved survival among patients at the highest SCD risk.

Aim: To assess patient survival rate after implantation of an ICD without resynchronisation capability in our own patient population. Using uni- and multivariate analysis, we attempted to identify factors associated with significant worsening of patient survival rate.

Methods: From the population of patients who underwent ICD implantation for primary or secondary prevention of SCD in 2008-2010, we selected 376 patients with coronary artery disease or dilated cardiomyopathy (56 females, 320 males). Mean age was 66.1 ± 11.2 (range 22-89) years. ICD implantation protocols and in-hospital and outpatient records were reviewed retrospectively. We analysed the following clinical and procedural variables: age, gender, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) functional class, mean heart rate (HR), QRS width, number of antiarrhythmic ICD interventions, type of SCD prevention, ICD type, performing defibrillation threshold testing (DFT) to establish defibrillation safety margin at ICD implantation, ventricular lead location, history of cardiovascular disease and arrhythmia, medications used (amiodarone, sotalol, beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, statins, loop diuretics, aldosterone antagonists). Date and cause of death were established by contacting patient family and/or the hospital to which the patient was admitted shortly before death or the general practitioner caring for the patient (verification of death certificates).

Results: During the mean follow-up period of 447 ± 313 days, 46 patients died of known causes. Causes of death included sudden death in 16 patients, heart failure in 20 patients, and other causes in 10 patients (respiratory failure - 1, bleeding diathesis - 2, lung cancer - 3, colorectal cancer - 1, traffic accident - 1, and stroke - 2 patients). A comparison between primary and secondary prevention patients was performed. Mean QRS width <118 ms, resting HR < 78 bpm and LVEF >30% were significant cutoff values for improved survival as determined using the ROC curves. HR >78 bpm was observed in all SCD patients. In Kaplan-Meier univariate analysis including 27 parameters potentially influencing survival, 10 significant parameters were identified (type of prevention, presence of cardiomyopathy, ventricular tachycardia, HR, QRS width, LVEF, NYHA class, performing DFT, and statin and diuretic treatment). In Cox multivariate analysis, risk of death was increased with mean LVEV <30% (3-fold increase in risk), no DFT (2-fold increase in risk), NYHA class III or IV (3-fold increase in risk), and no statin use (2-fold increase in risk). Mean HR <78 bpm and QRS width <118 ms were independently related to an increased survival.

Conclusions: Death rate was higher in patients with LVEF <30%, NYHA class III or IV, no DFT performed and no statin treatment. In these patients, indications for cardiac resynchronisation therapy should be considered. HR <78 bpm and QRS width <118 ms are independent protective factors. HR >78 bpm was observed in all SCD patients. Sicker ICD patients live for a shorter time. The presence of atrial fibrillation, number of antiarrhythmic ICD interventions, ICD type and revascularisation approach did not affect survival/mortality.