Combined prognostic value of peak O2 uptake and microvolt level T-wave alternans in patients with idiopathic dilated cardiomyopathy

Background Despite the great improvement in clinical management of patients with idiopathic dilated cardiomyopathy (DCM), sudden cardiac death (SCD) and death due to worsening heart failure (HF) remain a challenging problem. The assessment of oxygen consumption (peakVO2) has been recognized as an independent marker of mortality. Nevertheless peakVO2 is not helpful in the risk stratification of SCD. Given this limitation, the association with another non-invasive test able to predict SCD such as microvolt level T-wave alternans (MTWA) would be useful. Objectives To determine the combined predictive value of peakVO2 and MTWA in patients with DCM. Methods Seventy consecutive DCM patients were prospectively investigated. PeakVO2 and MTWA were determined during bicycle exercise testing. Primary composite study end-point was defined as major cardiac events (MCE): total cardiac death or documented sustained VT/VF (including appropriate ICD shock). Secondary end-point was defined as arrhythmic events (AE): SCD or documented sustained VT/VF. Results Thirty-nine patients (55%) had a peakVO2 < 10 ml/kg/min, while 40 patients (57%) showed an abnormal MTWA test. During an average follow-up of 19.2 ± 10.7 months, 11 MCE of which 6 AE have been documented. Among patients with abnormal MTWA and peakVO2 < 10 ml/kg/min 8 MCE of which 5 AE occurred while among patients with normal MTWA and peakVO2 ≥ 10 ml/kg/min no event occurred. From multivariate analysis, the combined prognostic value of MTWA and peakVO2 achieved statistical significance for MCE (p = 0.03, HR 0.28, 95% CI 0.12–0.95) and for AE (p = 0.05, HR 0.39, 95% CI 0.18–0.99) while MTWA alone was a significant predictor of AE (p = 0.04, HR 0.32, 95% CI 0.14–0.93). Conclusions Our results suggest that only the association of MTWA and peakVO2, but not the two single tests, is a significant prognostic marker of both MCE and AE in DCM patients. However, MTWA alone confirms its predictive power as arrhythmic risk stratifier in this population.