The major risk factors of inappropriate diet, physical inactivity, high cholestreol (> 250 mg%), high BMI (>26) and hypertension (>155 mmHg) and smoking, explain at least 75% of new cases of Coronary Artery Disease (CAD). In the absence of these risk factors, CAD is a rare cause of death.
Two studies have addressed the issue of predicting the risk of developing CAD: the Framingham 10 year prediction rule and the Duke clinical prediction of CAD study.
A new study published in the Annals of Internal Medicine earlier this month compared stress testing and Computed Tomography Coronary Angiography (CTCA) to identify patients with chest symptoms who should receive cardiac catherization. The study differentiated three groups of patients, ranging from low to high probability of CAD based on the Duke clinical prediction rule:
- Stress testing is sufficient as a first diagnostic test for patients with a low pretest probability of CAD on the basis of their Duke clinical score.
- Computed tomography coronary angiography plays a more important role in patients with an intermediate pretest probability, in whom the test can distinguish which patients require invasive testing.
- In patients with a high pretest probability, neither stress testing nor CTCA offers much additional diagnostic value, and physicians can proceed directly to ICA.
CT Angiography already plays in important role in identifying the presence of vascular disease. Thus far however, smaller arteries such as coronaries were more difficult to analyze. Newer technology has now reached a stage where it can be applied to the evaluation of coronary artery disease, thus opening the door to eliminating the large number of unnecessary cardiac catherizations performed in this country. CTCA is easy to perform and has none of the risks associated with cardiac catherization. At an estimated cost saving of $500 vs. $3000 for cardiac catherization, there is an important economic incentive to start using CTCA for screening of intermediate risk patients.
Cardiac catherization is an important test that should be limited to when a patient has already been identified with obstructive CAD, and where a road map is needed to outline what procedure should be next.
- The Framingham Heart Study, D’Agostino et al., Circulation 2008;117;743-753
- Value of the History and Physical in Identifying Patients at Increased Risk for Coronary Artery Disease, Pryor et al, Ann Int Med 1993;118:81-90
- Diagnostic Accuracy and Clinical Utility of Noninvasive Testing for Coronary Artery Disease, Weustink et al., Ann Intern Med. 2010;152:630-639″