Microvolt T-wave alternans in patients undergoing elective coronary artery bypass grafting: a pilot study

Introduction: We designed a prospective observational study targeting a selective population of patients undergoing elective coronary artery bypass grafting with normal systolic function. In this study we looked at the prevalence of pre-operative microvolt T-wave alternans and if it predicts atrial fibrillation after surgery.

Methods: The inclusion criteria included all patients referred to the cardiothoracic outpatient clinic for elective bypass, who can perform aerobic exercise, with a recent exercise stress test exercising at least to 85% of the maximal predicted heart rate (220 - age) and with non-limiting chest pain at maximal exercise. Twenty patients met the inclusion/exclusion criteria between May 2008 and February 2010. The hospital course of those patients was followed, and in-hospital events were recorded.

Results: Nine out twenty (45%) of patients had a non-negative microvolt T-wave alternans tracing. Six patients (30%) developed new onset atrial fibrillation post surgery. Patients with non-negative microvolt level T-wave alternans are more likely to develop atrial fibrillation post coronary artery bypass grafting then patients with negative microvolt level T-wave alternans (p=0.05).

Conclusions: This pilot study provides the first clinical evidence that patients with ischemic heart disease and normal systolic function have a high prevalence of abnormal microvolt T-wave alternans and might be at higher risk of sudden cardiac death. In addition our results show that microvolt level T-wave alternans predicts post coronary artery bypass grafting new onset atrial fibrillation.