Microvolt T-wave alternans (MTWA) is a promising non-invasive method of evaluating repolarization abnormalities. Its presence is strongly related to the occurrence of malignant ventricular tachyarrhythmias and is therefore regarded as a risk marker for sudden cardiac death. Most recent studies have described the usefulness of MTWA in selecting patients who may benefit from a cardioverter-defibrillator. This study presents two cases of patients suffering from ischemic cardiomyopathy, who underwent an MTWA test. Episodes of ventricular tachycardia occurred immediately after the end of the tests, with abnormal results.