During a 7-month period, 3,000 echocardiographic examinations were performed at the Ochsner Medical Institutions, New Orleans, and of these, 1,800 studies were performed with Doppler echocardiography (as ordered by the referring physicians), including continuous-wave, pulsed-wave, and color-flow Doppler techniques. From these Doppler echocardiographic studies, we identified patients with structurally normal M-mode and 2D echocardiograms. Exclusion criteria included the following: (1) atrial, ventricular, or aortic dilatation; (2) systolic ventricular dysfunction (either global dysfunction or regional wall motion abnormalities); (3) ventricular hypertrophy; (4) abnormal valve thickening or abnormal motion (eg, bicuspid aortic valve, valvular prolapse, valvular sclerosis); (5) annular calcification; (6) pericardial disease; or (7) congenital heart disease. Of these 1,800 Doppler echocardiograms, 206 (11 percent) met the criteria for our study.
Acquisition and Interpretation of Echocardiographic Data
The 2D and Doppler studies were performed by an experienced technician (on either a Hewlett-Packard Sonos 1000, an Acuson 128, or an Aloka 860). Transducer frequency was usually 2.5 MHz, although occasionally a 3.5-MHz transducer was used. Frame rates varied from 15 to 40 Hz depending on field depth and color display format. All of these studies were reviewed and interpreted by one of three experienced staff echocardiographers. In our laboratory, the majority of studies are reviewed before the patient leaves the laboratory, and on many occasions the physician performs part of the echocardiographic study in order to ensure highest accuracy of the data.