Microvolt t-wave alternans with exercise in pediatrics and congenital heart disease: limitations and predictive value.

BACKGROUND: Microvolt t-wave alternans (TWA) in early exercise is a noninvasive marker of life-threatening ventricular arrhythmia in some adult cardiac populations. The incidence and potential significance of sustained TWA in pediatric and congenital heart disease (CHD) populations has not been well defined.

METHODS: TWA treadmill exercise studies in pediatric patients with CHD, myopathy, potential myocardial ischemia, syncope, or history of cardiac arrest were analyzed. Tests were categorized as abnormal for sustained TWA with onset heart rate < 130 beats/min with specific analyses for lower onset heart rates. Patient characteristics were analyzed as possible correlates of TWA.

RESULTS: Over 2 years, 318 consecutive TWA exercise studies were performed in 304 patients (60% male, median 14 years, 6-41) for indications of syncope, cardiac arrest, possible ventricular arrhythmia, or evaluation of functional myocardial perfusion. Underlying conditions included apparently normal hearts (45%), CHD (16%), cardiomyopathy (11%), coronary anomalies (11%), electrical myopathy (9%), and transplant (8%). Abnormal TWA was seen in 24 (7%, onset HR 106 +/- 18) and included 19 at high clinical risk for serious events including 3 with cardiac arrest. By multivariate analysis sustained TWA was associated with cardiac arrest, ventricular arrhythmias, and a clinical classification of high risk.

CONCLUSIONS: TWA is associated with pediatric and CHD diagnoses at high risk of serious events and may contribute, with other diagnostic tools, to management choices. While the absence of TWA has relatively high negative predictive value, it does not completely exclude the potential for serious sustained ventricular arrhythmias. A more robust noninvasive marker for risk stratification in these populations is required.