Combined prognostic value of peak O(2) 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 (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.

Predictive significance for sudden death of microvolt-level T wave alternans in New York Heart Association class II congestive heart failure patients: a prospective study.

BACKGROUND: Sudden cardiac death (SDC) is responsible for approximately 60-70% of deaths in New York Heart Association (NYHA) class II congestive heart failure (CHF) patients. Recently, microvolt-level T wave alternans has been proposed as a new noninvasive tool to identify CHF patients at risk for SCD and ventricular tachycardia/fibrillation (VT/VF). OBJECTIVES: To determine the prognostic value of MTWA in NYHA class II patients. METHODS: Among 181 consecutive CHF patients with ischemic and nonischemic cardiomyopathy, 73 patients in NYHA class II with left ventricular ejection fraction <45% were selected and prospectively investigated. MTWA was determined during bicycle exercise testing. The study end point was defined as SCD, documented sustained VT/VF and appropriate implantable cardioverter defibrillator (ICD) shock. RESULTS: MTWA was positive in 30 (41%) patients, negative in 26(36%) patients and indeterminate in 17 (23%) patients. During an average follow-up of 17.1+/-7.4 months, seven patients had an arrhythmic event in the MTWA positive group, whereas one and no events occurred in the indeterminate and negative group, respectively. From Kaplan-Meier univariate analysis and multivariate Cox analysis, MTWA was a significant arrhythmic risk stratifier (p=0.01 and p=0.03, respectively). Sensitivity, specificity, negative and positive predictive values of MTWA were 100%, 53%, 100% and 24%, respectively. CONCLUSION: Our data suggest that MTWA is a promising predictor of arrhythmic events in NYHA class II CHF patients.