Trying to predict the unpredictable:device-based daily monitored parameters can predict malignant arrhythmic events in patients undergoing cardiac resynchronization

Abstract

Purpose: The aim of this substudy was to evaluate the prognostic values of device-based diagnostic parameters as predictors of malignant ventricular arrhythmias in patients undergoing Cardiac Resynchronization Therapy (CRT). Methods: Study population consisted of 96 CRT-D recipients participating in the TRUST CRT Trial. Inclusion criteria included Heart Failure (HF) in NYHA≥3 class, QRS ≥120msec, left ventricular Ejection Fraction (EF) ≤35% and significant mechanical dyssynchrony. Patients were divided into those with (n=31, 92 arrhythmias) and without (n=65) appropriate ICD interventions within the median follow-up of 12.03±6.7 months. Daily monitored device-based diagnostic parameters - day and night Heart Rate (HR), Thoracic Impedance (TI), heart rate variability and physical activity were screened for significant changes within 4 time windows: within 10, 7, 3 days and 1 day prior to the first and to all appropriate ICD interventions. Results: Only 6 arrhythmias (6.5%) in 4 patients (13%) showed temporal relationship to HF exacerbation. There was a consistent pattern of changes in three out of five monitored factors prior to arrhythmia: a gradual increase of daily HR (103.43% of reference within 10-day window, 103.6% in 7-days, 104.6% in 3 days and 105.55% one day before, all P<0.05 vs. reference). Similarly varied night HR (104.75% in 3 days, 107.65% one day, all P<0.05). On the contrary, intrathoracic impedance was decreasing significantly (97.8% in 10 days, 97.7% in 7-days, 97.34% in 3 days and 96.81% in 1 day, all P<0.05). Changes in device-monitored parameters showed only moderate sensitivity, but high specificity, the combination of three parameters had better predictive performance (sensitivity 42%, specificity 86%), which improved further after excluding patients with atrial fibrillation. The predictive model combining changes in HR and TI together with EF and NTproBNP (AUC 0.7, 95% CI 0.63-0.77; P<0.05) was more prognostic in forecasting day-by-day risk than model involving EF and NTproBNP alone (difference in AUC 0.05, 95% CI 0.0005-0.09; P=0.04). Conclusions: Daily device-measured parameters show reproducibly significant variations prior to ventricular arrhythmia. Combination of multiple parameters improves their predictive performance, whereas presence of atrial fibrillation diminishes it. Predictive value of these variables is additive to baseline risk factors.