Microvolt T-wave alternans in adult patients with repaired tetralogy of Fallot

Indications for sudden cardiac death (SCD) primary prevention are unknown in patients with repaired tetralogy of Fallot (ToF). The role of microvolt T-wave alternans (MTWA) in SCD risk stratification was documented. However, the prevalence of spectral MTWA and its association with ventricular arrhythmia (VA) in adults after ToF repair were not elucidated.

Microvolt T-wave alternans, electrocardiogram (ECG), ambulatory ECG monitoring, echocardiography, and spiroergometry were evaluated in 102 adults after ToF repair. Microvolt T-wave alternans results were classified as normal: negative(-), abnormal: positive(+), and indeterminate(ind). Owing to similar prognostic significance, MTWA(+) and MTWA(ind) due to patient factors were combined into nonnegative group: MTWA(abnormal).

Microvolt T-wave alternans(abnormal) was more frequent in the studied group as compared with controls (P = .0005). The MTWA(abnormal) group had greater right ventricular end-diastolic diameter (P = .005), higher incidence of pulmonary regurgitation (P = .015), lower peak oxygen consumption (P = .01), and higher VE/VCO2 slope (P = .04) in comparison with MTWA(normal). Univariate logistic regression proved pulmonary regurgitation (OR = 3.57, 95% CI 1.27-10.04), VA (OR = 3.26, 95% CI 1.06-10.05), right ventricular end-diastolic enlargement (OR = 1.11, 95% CI 1.03-1.2), increase in VE/VCO2 slope (OR = 1.08, 95% CI 1.01-1.17), and decrease in peak oxygen uptake (OR = .91, 95% CI 0.83-0.99) to increase MTWA(abnormal) prevalence.

In adults after ToF repair, abnormal MTWA occurred more often than in controls. Probability of abnormal MTWA did not rise with prevalence of malignant VA; however, presence of abnormal MTWA was associated with VA risk factors: pulmonary regurgitation, right ventricular enlargement, and consequent heart failure. The role of MTWA in selecting patients late after ToF repair at risk of SCD needs further observation.