COST-EFFECTIVE SELECTION OF PATIENTS FOR CORONARY ANGIOGRAPHY

In patients suspected of having coronary artery disease (CAD), noninva sive testing has been playing an increasing role in selecting patients who would require coronary angiography for either the ''definitive'' diagnosis of CAD or as a prelude to planning myocardial revascularizat ion. A mathematic model is presented that defines cost-effective utili ty of nuclear cardiology testing for diagnosis of CAD and selection of appropriate candidates for coronary angiography, according to quantit ative methods of decision analysis. Clinical utility or effectiveness was defined in terms of percent correct diagnosis of CAD. Cost was def ined as dollars of medical expenditure. Sis competing strategies were compared in subsets of patients with different pretest likelihoods of CAD, based on age, sex, and symptoms. Nuclear cardiology testing was t he most cost-effective initial modality of choice in patients with an intermediate pretest likelihood of CAD. In patients with a low pretest likelihood of CAD, nuclear cardiology testing was cost-effective in t he subgroup of patients who had abnormal exercise treadmill electrocar diograms. In patients with a high pretest likelihood of CAD, direct re ferral to coronary angiography was the most cost-effective strategy fo r diagnosis of CAD. Coronary angiography, however, is performed most o ften as a prelude to myocardial revascularization. Because these invas ive procedures are indicated only in patients who are at high risk wit h medical therapy, nuclear cardiology procedures, by virtue of increme ntal prognostic information, identify appropriate candidates for more invasive procedures, aimed at improving survival. Strategies for cost- effective prognostication of CAD depend on not only the patient's pret est likelihood of CAD but also the status of the rest electrocardiogra m. In patients with a normal rest electrocardiogram a low pretest like lihood of CAD indicates a low risk for cardiac events with medical the rapy. Therefore coronary angiography is not indicated in these patient s. Patients with an intermediate likelihood of CAD should first underg o exercise electrocardiographic testing; a negative response mould ind icate a low risk for cardiac events and a positive response would indi cate the need for nuclear cardiology testing for further cost-effectiv e risk stratification. In patients with a high pretest likelihood of C AD, the combined exercise electrocardiographic and nuclear cardiac tes ting is the most cost-effective strategy; a negative or a positive nuc lear test result would imply low or high risk, respectively. The latte r patients mould then be candidates for coronary angiography. In all p atients with an abnormal rest electrocardiogram, the most cost-effecti ve strategy is uniform referral to nuclear cardiac testing (which is p erformed in conjunction with exercise electrocardiography), regardless of the pretest likelihood of CAD; a negative or a positive nuclear te st result would indicate low or high risk for coronary events, respect ively. The latter group would be proper candidates for referral to cor onary angiography.