14. Choosing Appropriate Imaging Techniques

There is no single algorithm for choosing among myriad cardiac imaging tests. Suspected or confirmed epicardial coronary artery stenoses are typically evaluated directly by X-ray angiography in settings where revascularization is under consideration or when the pretest likelihood of disease is sufficiently high to warrant bypassing less invasive indirect testing of coronary perfusion (i.e., treadmill stress electrocardiography, stress echocardiography, or myocardial perfusion imaging.) As the pathophysiologic model of acute coronary syndromes continues to evolve, more attention will focus on early detection of nonstenotic but high-risk “vulnerable” atheromatous plaques. CT, cardiac MRI, intravascular ultrasound, and nuclear imaging techniques will continue to evolve for the purpose of coronary plaque characterization and risk stratification.

Myocardial and valvular disorders, including myocardial tissue abnormalities and systolic and diastolic dysfunction, are best imaged by techniques that provide both structural and functional (i.e., hemodynamic) information. While 2-D echocardiography with Doppler imaging is currently the standard for assessing myocardial and valvular function, cardiac MR techniques may develop into a new “gold standard” for measuring systolic function. 3-D echocardiography has great potential. Invasive measurement of intracardiac pressures by right heart catheterization is reserved for cases in which noninvasive testing yields inconclusive results or results discrepant with clinical findings.