Combined prognostic value of peak O(2) uptake and microvolt level T-wave alternans in patients with idiopathic dilated cardiomyopathy

Abstract

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 (peakVO(2)) has been recognized as an independent marker of mortality. Nevertheless peakVO(2) 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 peakVO(2) and MTWA in patients with DCM.

Methods: Seventy consecutive DCM patients were prospectively investigated. PeakVO(2) 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 peakVO(2)<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 peakVO(2)<10 ml/kg/min 8 MCE of which 5 AE occurred while among patients with normal MTWA and peakVO(2)> or =10 ml/kg/min no event occurred. From multivariate analysis, the combined prognostic value of MTWA and peakVO(2) 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 peakVO(2), 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.