Electrocardiographic ST segment depression and clinical function in children with Fontan circulation

Previous studies noted that Fontan patients have electrocardiographic ST depressions during exercise tests and on 24-hour ambulatory electrocardiographic (ECG) monitoring. This study investigated whether the ST depressions were correlated to clinical function (NYHA Functional Classification). Forty-five children in two groups were examined--15 patients with Fontan circulation and 30 with a structurally normal heart, matched for sex, height, and weight. Clinical and echocardiographic examinations were performed. The clinical state was defined as NYHA functional classes I-IV. All 45 children underwent 24-hour ECG and an analysis of ST changes was performed, with ST segment depression > 0.20 mV at ST 60 regarded as significant. Twelve of 15 patients had significant 24-hour ECG ST depressions; in 9 of 12 patients these occurred on more than one occasion. Comparing 24-hour ECG recordings from patients in NYHA I with patients in NYHA II or III showed a significant difference in depth (p = 0.0023), duration (p = 0.0016), and number of ST depressions (p = 0.0001). None of the matched healthy children showed ST depressions. Repeated ST analysis on 24-hour ECG shows that the ST depressions seem to be correlated to functional status and this may be a useful tool in clinical praxis.