ing showed a 0*3 mV depression of the ST segment in lead CM5 but produced no chest pain. The patient was referred for right heart catheterisation and intracardiac electrography. These examinations showed no signs of left to right shunt, and no inducible ventricular tachycardia or ventricular fibrillation was recorded during electrophysiological studies. Myocardial perfusion scintigraphy with thallium-201 showed decreased activity in the anteroapical region. We therefore decided to perform coronary angiography. There was no evidence of aortic stenosis, and the pressures in the left ventricle were normal (100/8 mm Hg). Left ventriculography showed a normal contraction pattern, an ejection fraction of 0-71, no signs of mitral regurgitation, and no left coronary artery arising from the aorta. The right coronary orifice was found to be very wide and when injected with contrast was dilated and tortuous with many collateral channels through which the contrast passed to the left coronary artery and finally drained retrogradely into the pulmonary artery (Figure a).At operation the right coronary artery was dilated. The left anterior descending artery was small with an internal diameter of 2 mm. The left anterior descending and the circumflex arteries were in the normal 110