Comparison of M-mode and two-dimensional echocardiography.

IN THE PRECEDING ARTICLE in this issue of Circulation, Wann et al. compare features of M-mode and two-dimensional echocardiography as used in patients with infective endocarditis. Their discussion should arouse curiosity about the implied conflict between M-mode and the newer, two-dimensional approach for general ultrasonic imaging of the heart. M-mode echocardiography has well-known capabilities. Clinician-echocardiographers can master this method in most diagnostic situations. This favorable milieu prevails because of the 15 or 20 years of intensive study into the capabilities of the technique that preceded its widespread, rapid acceptance in clinical practice. No other diagnostic modality based on modern electronic methods provides the "hands-on" characteristics that allow a physician to examine cardiac anatomy, confirm diagnostic impressions and immediately direct and accomplish further clinical examination. Now, there is similar clinical enthusiasm for twodimensional echocardiography, but there has been no luxury of time to develop a mature understanding of the technique. Practical systems for clinical use were developed only 4 years ago, and the demand for twodimensional echocardiographic services has accelerated rapidly. The ultimate clinical capabilities of this method are still uncertain, and some confusion exists regarding its indications for use, particularly in comparison with M-mode procedures. This is an appropriate time to reflect upon several features of Mmode and two-dimensional echocardiography that serve to characterize and direct the use of both imaging methods.