Analysis of arrhythmic episodes in patients with implanted cardioverter defibrillators and a high risk of sudden cardiac death

Abstract

Aim. To analyze arrhythmic events, according to the programming data of implanted cardioverter defibrillators (ICD), with the view of minimizing shock effects.Material and methods. The study included examination materials of 207 patients with implanted ICD/cardiac resynchronization therapy (CRT) devices. Patients were divided according to the types of implanted devices: 65 patients (31%) — CRT, 75 patients (36%) — single-chamber ICD, 67 patients (33%) — dual-chamber ICD. In the patient structure there were 168 patients (81%) with primary and 39 patients (19%) with secondary prevention of sudden cardiac death (SCD). In order to minimize the amount of shock effects applied, the following defibrillator programming techniques were used: prolongation of the duration of tachycardia detection in the ventricular fibrillation (VF) zone from the nominal parameters and changing the plan of applying antitachycardia stimulation (ATS) in VF zone (the number of stimuli in the exposure pack was increased and the stimulation interval was shortened by 10-20% in comparison with the initial parameters). To stop hemodynamically insignificant monomorphic ventricular tachycardia, shocks in the stopping pattern were disabled and only ATS was activated. Statistical processing of the obtained data was carried out using the “IBM SPSS Statistics 20” software.Results. The probability of shock and ATS effects in patients from the primary SCD prophylaxis group significantly increases in the presence of: ischemic cardiomyopathy (p=0,006) and severe ventricular extrasystoles (p=0,029).The absence of amiodarone therapy significantly increases the risk of shock effects in patients with implanted ICD for primary (p=0,002) and secondary prevention of SCD (p=0,02). In the vast majority of cases, appropriate shock effects were inflicted on patients with coronary artery disease and a history of myocardial infarction. On the contrary, in patients with dilated cardiomyopathy, clinically inappropriate shocks prevailed, most often performed on atrial fibrillation (р<0,001). In all cases of life-threatening ventricular arrhythmias, the effects of ICD and CRT were effective for their relief. There were no suddenly dead patients in the study. There were no negative effects of the proposed programming techniques. Against the background of increased tachycardia detection time, 48% of all arrhythmias stopped on their own without worsening. In patients with CRT devices, founded and unfounded responses were significantly less common than among patients with ICD. The main causes of inappropriate responses were: atrial arrhythmias in the VF detection zone (р<0,001), standard detection time in the VF zone (р<0,001) restrictions on the use of atrial ventricular arrhythmias discriminator (р<0,018).Conclusion. The prolongation of the tachycardia detection duration in the VF zone and the optimization of ATS lead to a decrease in shock ICD effects.

Keywords

• sudden cardiac death
• implantable cardioverter-defibrillator
• cardiac resynchronization therapy devices with defibrillation function
• antitachycardia stimulation
• founded shock
• unfounded shock
• detection of tachycardia