Aim: To determine predictors of sustained ventricular arrhythmias (SVA) in pts with good response to CRT.
Methods: Prospective cohort study of HF pts with reduced ejection fraction submitted to CRT-ICD. NYHA class, blood analysis, cardiopulmonary exercise testing and echocardiography were performed before and 3-6 months after CRT. In pts with no SVA prior to CRT (primary prevention) and with left ventricular ejection fraction (LVEF) > 35% 3-6 months after CRT, predictors of SVA were determined using regression analysis. Calibration of a score was assessed by Hosmer-Lemeshow test and discrimination, sensitivity, specificity and likelihood ratio by the area under the receiver operating curves (AUC).
Results: Of the 114 pts analyzed (70±14 years, 69.2% men, 29.1% ischemic etiology, 73.1% baseline NYHA III-IV, baseline LVEF 27%±11%), 69 (60.5%) had LVEF > 35% 3-6 months after CRT. In this population, 14 pts (20.3%) experienced a SVA during a mean follow-up of 38.3 months. 8 pts (12.0%) suffered inappropriate device therapies, adding up to a total of 35 episodes. Furthermore, 11 pts (15,9%) were submitted to generator replacement during follow-up. SVA were associated with troponin I (OR 1.427x10^22 95% CI 27.636-7.372x10^42 p 0.036), high-density lipoprotein (OR 0.957 95% CI 0.912-1.004 p 0.071), VEVCO2 slope (OR 1.097 95% CI 1.021-1.178 p 0.011), systolic blood pressure (OR 0.974 95% CI 0.974-1.001 p 0.062) and end-diastolic left ventricular volume (OR 1.006 95% CI 1.000-1.011 p 0.046). In the multivariate analysis, VEVCO2 slope was the only independent predictor of SVA (OR 1.156 95% CI 1.042-1.283 p 0.006). As a score to predict SVA, VEVCO2 slope showed good calibration and good discrimination with an AUC of 0.70. The ideal cut-off value of VEVCO2 slope to exclude SVA during follow-up is 24.35 (negative likelihood ratio 0.5).
Conclusion: The incidence of SVA in pts with adequate response to CRT is relatively high. On the other hand, inappropriate therapies are not an uncommon event. Cardiopulmonary exercise testing with assessment of VEVCO2 slope can be used as a widely accessible method with low cost to recognize pts who will no longer benefit from CRT-ICD (and to whom it may cause harm due to inappropriate therapies) and where downgrading CRT-P is suitable.