Prediction of Inappropriate Implantable Cardioverter-Defibrillator Therapies Through Parameters Obtained in a Simple Exercise Stress Test

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Although the clinical benefits of implantable cardioverter-defibrillators (ICDs) have been demonstrated, inappropriate therapies (IATs) cannot be completely avoided even with the most advanced devices. Recently, IATs are considered to decrease the ventricular function and prognosis of a patient. The aim of this study was to investigate the predictors of IAT with parameters during cardiopulmonary exercise stress test (CPX). Sixty consecutive ICD patients underwent symptom-limited CPX, and were divided into IAT (+) and IAT (−) groups. During and after CPX, ECG and hemodynamic parameters of systemic blood pressure, heart rate, and maximal O2 consumption (max VO2) were evaluated every minute. In selected patients, sympathetic and parasympathetic activities were evaluated with analyses of heart rate variability (HRV). No significant differences were observed in clinical background parameters. In the CPX parameters, only the maximal heart rate exhibited a significant difference between the IAT (+) group and the IAT (−) group (154.8 ± 5.9 versus 137.9 ± 4.2 beats per minute, P = 0.032), and LF/HF was higher during the recovery phase 4 minutes after peak exercise in the former group (4.5 ± 1.0 versus 2.4 ± 0.9, P = 0.021). In ICD patients, IAT can be predicted using simple parameters of increased sympathetic activity such as increased maximal heart rate and increased LF/HF ratio during and after the exercise stress test.