Noninvasive Assessment of Myocardial Function

Myocardial function can be assessed noninvasively by echocardiography and radionuclide techniques. M-mode echocardiography provides important clues to ventricular volumes, wall thickness, wall motion, ejection fraction, and shortening velocities. The relative movements of posterior wall and septum can be ascertained and several specific cardiomyopathies recognized. M-mode echocardiography gives a limited "ice-pick" view of the left ventricle. Two-dimensional techniques give additional information. Echocardiography is done during rest, while radionuclide procedures are done during rest and exercise. First-pass radionuclide angiocardiography can estimate ventricular ejection fractions independently of geometric assumptions. Equilibrium gated blood pool imaging by multiple gated acquisition techniques allows repeated visual assessment of overall and regional ventricular function. Thallium-201 imaging provides insight into regional myocardial perfusion during rest and exercise but is limited by its resolution and isotope persistence. Newer techniques using 13NH3 promise better approaches to perfusion with tomographic identification of regional changes.