[Study of coronary perfusion by radioisotopes]

The study of coronary blood flow by radio isotpopes may determine the casual relationship between coronary artery narrowing and myocardial ischemia. Total coronary flow is measured without cardiac catheterisation by double counter technique using 84 Rb and by radionuclide angiography using 42 K and 113m in fixed on siderophilin. This is an easier method, which is very reproductible and which may be sensitised by atrial pacing. The measurement of regional coronary flow gives a better estimation of the physiological effects of coronary artery disease. Two indicators are used; radioactive gases (113 Xe and more recently 81 m Kr) and microspheres tracers. Selective coronary injection of biodegradable microspheres labelled with 99m Tc and 113m In may be used to assess the hyperemic reaction in the coronary arteriolar territory to the triiodide contrast media used in coronary angiography, and to estimate the reserve coronary blood flow. The transmural perfusion may be studied in animal experiments with non-biodegradable microspheres. Tomographic techniques should allow quantification of myocardial perfusion in man.