The safety of dipyridamole-thallium imaging in patients with critical aortic valve stenosis and angina.

Angina pectoris occurs in many patients with critical aortic valve stenosis, but in less than 50% of cases is it due to atherosclerotic coronary disease. Pre-operative coronary angiography is used to determine whether coronary revascularization is required in addition to aortic valve replacement. The aim of this study was to determine the safety and image quality of dipyridamole-thallium imaging (DPT) in excluding coronary artery disease requiring a coronary artery bypass graft in patients with aortic valve stenosis requiring aortic valve replacement. Dipyridamole-thallium imaging and coronary angiography were performed less than one month apart in patients with clinical and echo-Doppler evidence of aortic valve stenosis requiring aortic valve replacement. Coronary angiography and DPT were each interpreted by experienced observers blind to the other result. The safety of DPT was judged by symptoms, ECG changes, haemodynamic effects and the need for stress reversal. Image quality was determined from the myocardial-to-background thallium uptake ratio in a normal segment. Twelve patients with aortic valve stenosis (gradient 95 +/- 24 mmHg) were studied, all of whom had left ventricular hypertrophy. The dominant symptom was angina pectoris in eight patients, syncope in three and dyspnoea in one. None had previous myocardial infarction, but two were smokers, six were hyperlipidaemic and one was hypertensive. The patients tolerated DPT well and only one required stress reversal. The quality of the DPT images was good. The DPT image was entirely normal in eight (66%) patients, none of whom had coronary artery disease. Reversible defects were seen in four patients, all of whom had significant coronary artery disease. We conclude that DPT is safe in patients with aortic valve stenosis and angina pectoris. The image quality is good despite left ventricular hypertrophy. In patients with angina pectoris and aortic valve stenosis, coronary angiography can safely be restricted to those with abnormal myocardial perfusion results.