Body surface isopotential T map for assessment of right ventricular volume and pressure overloads in secundum atrial septal defect.

The body surface isopotential T map was analyzed to detect right ventricular volume and pressure overloads in 25 patients with secundum atrial septal defect. Three patterns were distinguished: a T map resembling normal (type A, n = 9); that with an isolated negative area in a positive area (type B, n = 11); and that with rightward movement of maximum (type C, n = 5). Right ventricular end-diastolic volumes in types B (161 +/- 19% of normal; %N) and C (175 +/- 40% N) were significantly (p < 0.01) greater than those in controls (100 +/- 9% N) and type A (113 +/- 18% N). Right ventricular systolic pressure in type C (48 +/- 11 mmHg) was significantly (p < 0.01) higher than those in the controls (30 +/- 5 mmHg), type A (31 +/- 4 mmHg), or type B (34 +/- 5 mmHg). These results suggest that the patients with type B have right ventricular volume overload and those with type C have both volume and pressure overloads.