CONTINUOUS WAVE DOPPLER ECHOCARDIOGRAPHIC EVALUATION OF CARDIAC-OUTPUT AND ITS APPLICATION TO TREADMILL EXERCISE

To evaluate the clinical usefulness of Doppler-derived cardiac output and the effect of altered left ventricular function during maximal treadmill exercise, this study was performed using continuous wave (CW) Doppler technique through the suprasternal notch acoustic window. Subjects consisted of 22 patients with coronary artery disease (study 1) and 21 healthy male volunteers (study 2). In study 1, cardiac output obtained by Doppler method was well correlated with simultaneous thermodilution measurements when the cross-sectional area was employed at the level of the aortic root just above the sinus of Valsalva (r = 0.86). In study 2, exercise duration was 15-18 min and CW Doppler recordings could be performed until the end of the treadmill exercise in all subjects (peak heart rate 140-190 beats/min). Mean stroke volume index increased from 34 ± 6 ml/m2 at rest to 57 ± 10 ml/m2 (peak stroke volume) at 126 beats/min and then decreased to 46 ± 8 ml/m2 at peak exercise. Mean cardiac index increased progressively until peak exercise by further increment in heart rate (2.5 ± 0.4-7.5 ± 1.4 l/min/m2). Peak velocity of ascending aortic flow also increased from 0.71 ± 0.13 m/s at rest (upright position) to 1.40 ± 0.18 m/s at peak exercise. In recovery, the 1-min stroke volume index and ascending aortic peak velocity were significantly larger in the supine than in the upright position although cardiac index was not significantly different in both postures. The changes in Doppler-derived systolic parameters during and after exercise can provide a reference for the evaluation of patients with known or suspected heart disease.