Hemodynamic effects of calcium channel and beta-receptor antagonists: evaluation by Doppler echocardiography

Pulsed wave Doppler echocardiography in normal horses

Reference values were established for selected Doppler derived variables from a group of 40 normal Thoroughbred and Thoroughbred cross horses. Standard two-dimensional (2-D) images used for guiding the Doppler sampling site allowed accurate alignment with flow. Tricuspid inflow velocities during rapid filling (E) and atrial contraction (A) were significantly higher when recorded from a right parasternal angled view than from a right parasternal long-axis view. In 8 horses the tricuspid inflow peak A velocity was higher than the peak E velocity. The peak acceleration of blood flow was higher (P = 0.000) in the aorta (mean 8.01 m/s/s) than in the pulmonary artery (4.45 m/s/s). Significant differences were also noted in the pre-ejection period, ejection time and acceleration time between the 2 vessels. Horses with functional ejection murmurs had lower peak aortic acceleration and a longer acceleration time than horses without flow murmurs. Horses with filling murmurs over the left hemithorax had a significantly higher peak mitral E velocity than horses without such murmurs. Measurements from Doppler waveforms were repeatable and may prove useful in assessing ventricular function in this species.

A placebo controlled comparison of the effects of metoprolol and celiprolol on echo-Doppler measurements of cardiovascular function in normal volunteers

1. This study used a continuous-wave echo-Doppler method (Exerdrop) to investigate the effects of beta-adrenoceptor antagonism and partial agonism on cardiovascular responses at rest and during dynamic exercise. 2. A double-blind, randomised, placebo controlled comparison of metoprolol (50 mg) and celiprolol (200 mg) was undertaken in nine normal volunteers; single oral doses of medication were administered at weekly intervals. Rest and exercise (supine bicycle) haemodynamics were assessed at 0, 2, 4, 6 and 8 h following dosing. 3. Before dosing and after placebo, the aortic flow velocity, acceleration and velocity integral increased progressively during exercise, as did heart rate, blood pressure and cardiac output. 4. Following metoprolol 50 mg, heart rate was significantly reduced without change in systolic or diastolic blood pressure. Echo-Doppler peak acceleration and velocity decreased at rest. On exercise, heart rate and systolic blood pressure fell significantly; the increase in acceleration was significantly blunted compared with placebo (a decrease of 15.2% at rest and 22.9% at 75 watts; P < 0.01 vs placebo). Peak velocity fell significantly by 75 watts exercise. 5. Celiprolol 200 mg at rest significantly increased systolic blood pressure, peak acceleration and velocity. On exercise celiprolol, in contrast to metoprolol, did not reduce peak acceleration or peak velocity; however exercise heart rate and systolic blood pressure were significantly reduced. The difference between celiprolol and metoprolol in respect of peak acceleration persisted over the 8 h of the study. 6. These differences between metoprolol and celiprolol are compatible with the partial agonism of celiprolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Reliability of blood pressure, heart rate, and Doppler-derived hemodynamic measurements during exercise

Doppler echocardiography of aortic blood flow, heart rate, and blood pressure represent noninvasive methods for evaluation of the hemodynamic effects of pharmacologic agents or other stimuli during rest and exercise. In this study the reliability of continuous-wave Doppler echocardiography for detecting the effects of various interventions on left ventricular systolic function during exercise was assessed. The reliability of Doppler measurements was compared with that found for measurements of simultaneously obtained heart rate and blood pressure. Exercise treadmill testing was performed at 0, 2, 4, 6, and 8 hours in 18 healthy male subjects. All measurements were performed at rest and during the last half of each exercise stage. Reliability of peak modal velocity, peak aortic blood flow acceleration, heart rate, and blood pressure was measured by the intraclass correlation coefficient (ICC) at each stage. ICC reliability of greater than 0.75 is considered excellent, 0.4 to 0.75 fair to good, and less than 0.4 poor. The reliability of all Doppler-derived parameters, heart rate, and blood pressure improved with increasing stage of exercise. Peak modal velocity, peak acceleration, heart rate, and manually obtained systolic blood pressure had ICCs of 0.75 or greater by stage 3. The reliability of Doppler-derived aortic blood flow parameters was good or excellent at rest and advanced stages of exercise. Continuous-wave Doppler echocardiography is a reliable method for performing studies to assess the effects of interventions on cardiovascular function during exercise.