Radionuclide assessment of left ventricular performance on exercise after external conduit operation

Only limited information is available concerning left ventricular (LV) response to exercise after an external conduit operation for cyanotic congenital heart disease. Sixteen patients who had undergone external conduit repair (EC group) were studied with multi-gated cardiac pool imaging using a supine bicycle ergometer on 20 occasions. Six patients with a history of Kawasaki disease without coronary artery stenosis served as controls (control group). Myocardial imaging and cardiac catheterization were also performed in the EC group. There was no significant difference in left ventricular ejection fraction (LVEF) at rest between the groups. However, on exercise, LVEF of the EC group was significantly lower than that of the control group. Nine patients in the EC group showed a perfusion defect (PD) on 12 occasions. LVEF on exercise of the patients with PD was significantly lower than that of the patients without PD. Furthermore, only the patients with PD showed a LVEF decrease of 5% or more in response to exercise. In the EC group, a significant inverse relationship was demonstrated between right ventricular systolic pressure (RVP) and LVEF response to exercise. However, two out of four patients who underwent external conduit replacement improved their LVEF response to exercise with successful reduction of RVP. These findings indicate that an impaired left ventricular response to exercise was common in patients after external conduit operations. Myocardial damage and right ventricular outflow tract obstruction could be the causes of this left ventricular dysfunction.