Nuclear techniques in ischemic heart disease.

Until recently, it was necessary to measure parameters such as ventricular pressure to assess the effects of drugs on the force of myocardial contraction--the inotropic effect. Even simpler measurements such as cardiac output are not completely satisfactory, because they are determined not only by the contractile state but also by the diastolic volume of the ventricles, outflow impedance, and heart rate. Within the past few years, the use of radioactive tracer techniques has made it possible to measure the changes in ventricular volume that occur throughout the cardiac cycle. With these techniques, it is now possible to measure end-diastolic and end-systolic volumes, the rates of ventricular emptying and filling, stroke volume, and systolic and diastolic time intervals. In complicated diseases such as combined valvular and coronary artery disease the ventricular response to antiarrhythmic, vasodilator, and inotropic drugs can be assessed in individual patients.