Israel Medical Association Journal

Background: Microvolt T-wave alternans (MTWA) measures subtle beat-to-beat fluctuations in the T-wave amplitude. It was found to be associated with cardiac electrical instability in patients with ischemic and dilated cardiomyopathy.

Objectives: To investigate the reproducibility of the MTWA test results in patients with ischemic heart disease.

Methods: The study group comprised patients with ischemic heart disease who participated in a rehabilitation program at the Assaf Harofeh Medical Center. MTWA was measured during a bicycle exercise test at the first encounter and repeated after one week.

Results: Of the 40 study patients with coronary artery disease, 4 had an indeterminate result and were excluded from the data analysis; 5 had a positive MTWA in the first and second study (14%), 27 had a negative MTWA in the first and second study (75%), and 4 had a negative MTWA in the first study and a positive MTWA in the second study (11%). Overall, there was a correlation between the results of the first and the second study in 89% of the patients (kappa = 0.652, P = 0.0001).

Conclusions: MTWA measurements are reproducible in the short term in patients with coronary artery disease.

Background: Patients with hypertrophic cardiomyopathy are prone to ventricular arrhythmias and sudden death. Identifying patients at risk of sudden death is difficult.

Objectives: To determine whether microvolt T-wave alternans detected during exercise or rapid atrial pacing can identify patients with HCM[1] who are at risk of ventricular arrhythmias and sudden death.

Methods: This prospective observational study included 21 patients with HCM: 11 with hypertrophic obstructive cardiomyopathy, 9 with non-obstructive hypertrophic cardiomyopathy, and 1 with apical hypertrophic cardiomyopathy. TWA[2] was measured while the patients were on anti-arrhythmic medication.

Results: TWA was positive in 9 patients (43%) and negative in 12 (57%). Three patients were resuscitated after sudden death before their enrolment in the study and two patients developed ventricular tachycardia and fibrillation respectively during the study period. After combining the endpoint of sudden death from a ventricular arrhythmia and the presence of ventricular arrhythmias on a Holter monitor, there was no significant correlation between the presence of a positive TWA and the presence of ventricular arrhythmias on the Holter monitor or a history of sudden death.  

Conclusion: TWA cannot be used as a non-invasive test for detecting patients with HCM and electrical instability. TWA is not useful for predicting sudden death in patients with HCM.