Hemodynamic determinants of exercise-induced ST-segment depression in children with valvar aortic stenosis

To evaluate the hemodynamic factors associated with treadmill-induced ST-segment depression in children with valvar aortic stenosis, 12 patients (mean age 13 years) with ST-segment depression during treadmill exercise and 5 patients (mean age 13 years) without ST-segment depression during treadmill exercise underwent exercise testing during cardiac catheterization. The left ventricular (LV) systolic pressure and LV outflow tract gradient at rest (177 +/- 25 vs 138 +/- 8 mm Hg and 59 +/- 18 vs 23 +/- 7 mm Hg, respectively) and corresponding pressures during maximal supine exercise (248 +/- 37 vs 189 +/- 17 mm Hg and 112 +/- 34 vs 52 +/- 14 mm Hg) were significantly greater (p less than 0.01) in the patients with exercise-induced ST-segment depression, although overlap existed. The LV-O2 supply-demand ratio during maximal supine exercise was significantly less (6.4 +/- 2.7 vs 11.8 +/- 0.7; p less than 0.005) in patients with than in those without exercise-induced ST-segment depression. In fact, an LV-O2 supply-demand ratio less than 11.0 was 100% sensitive and specific in predicting treadmill-induced ST-segment depression. These results suggest that although the development of ST-segment depression during treadmill exercise is related to LV systolic pressure and LV outflow gradient, its major hemodynamic determinant is the LV-O2 supply-demand ratio.