Twenty-three patients who underwent operation for anomalous origin of the left coronary artery from the pulmonary artery were reexamined with two-dimensional echocardiography and thallium 201 perfusion imaging. Follow-up studies were performed 0.6 to 16.2 years (median 2.9 years) after operation. In 22 of 23 patients, a two coronary artery system had been established by implantation of the left coronary artery into the aorta (n = 8) or by anastomosis of the left subclavian artery with the left coronary artery (n = 14). The left coronary artery had been ligated in only one patient. For stress testing, 0.8 mg dipyridamole per kilogram body weight was infused in a 10-minute period in 20 of the 23 patients. High-dose dipyridamole infusion increased mean heart rate (98.1 +/- 27.1 to 122.3 +/- 19.2 beats/min, p < 0.001) and mean left ventricular ejection fraction (54.8% +/- 11.8% to 61.3% +/- 12.5%, p < 0.05) and decreased left ventricular end-diastolic volume index (38.8 +/- 26.7 to 29.9 +/- 8.3 ml/m2, p < 0.005). At rest, left ventricular dimensions were abnormal in only one patient, in whom the anastomosis with the left coronary artery proved to be occluded, as seen with subsequent angiography. Left ventricular function seen with two-dimensional echocardiography was normal in 19 patients and was compromised in 3 (all of whom had major structural anomalies of the left ventricle, such as left ventricular aneurysm, occlusion of the anastomosis, or mitral valve prosthesis). Patients with R-wave loss as seen with preoperative electrocardiography tended to have larger left ventricular volumes at follow-up (69.2 +/- 56.5 ml/m2 versus 32.4 +/- 9.6 ml/m2, p < 0.07). Ten of 20 patients had normal thallium 201-perfusion scans. In 9 of 20 patients defects revealed by permanent thallium 201-perfusion were observed and determined to be myocardial scars. Transient perfusion defects under dipyridamole stress with redistribution at rest occurred in three children, two of whom also had permanent thallium 201 defects. None of the three patients had angina-like symptoms or S-T segment changes during dipyridamole stress. Left ventricular ejection fraction, however, decreased severely during dipyridamole infusion in the single patient with ligature of the left coronary artery. The two remaining patients had normal echocardiographic left ventricular function under stress, and the diagnosis of myocardial ischemia as seen with scintigraphy must be questioned.(ABSTRACT TRUNCATED AT 400 WORDS)