We used Doppler echocardiography to quantitate the changes in intracardiac blood flow velocities and right and left ventricular stroke volumes in 80 normal human fetuses from 19 to 40 weeks gestation. Blood flow velocity spectra across the aortic, pulmonary, tricuspid, and mitral valves were digitized to obtain peak velocities (m/sec) and flow velocity integrals. Aortic and pulmonary diameters were measured at valve level from two-dimensional echocardiographic images and cross-sectional area was calculated assuming a circular orifice. Ventricular stroke volume was calculated as the product of the cross-sectional area of a great vessel and the flow velocity integral through that vessel. The pulmonary arterial and aortic diameters increased linearly with gestational age (r = .82, r = .84), and pulmonary arterial diameter consistently exceeded aortic diameter. There was a positive relationship between stroke volume and gestational age: stroke volume increased exponentially from 0.7 ml at 20 weeks to 7.6 ml at 40 weeks for the right ventricle (r = .87) and from 0.7 ml at 20 weeks to 5.2 ml at 40 weeks for the left ventricle (r = .91). Similar results were obtained for right and left ventricular and combined cardiac outputs. In 44% of the fetuses it was possible to quantitate both right and left ventricular stroke volumes. There was a close correlation between right and left ventricular stroke volumes in these fetuses (r = .96) and right ventricular stroke volume exceeded left ventricular stroke volume by 28%. Flow velocity across the tricuspid and mitral valves was consistently greater during atrial systole (A wave) than during rapid ventricular filling (E wave) (0.52 0.07 vs 0.37 + 0.08 m/sec and 0.45 ± 0.07 vs 0.33 ± 0.06 mlsec). The E/A ratios for the mitral and tricuspid valves were similar throughout the period of gestation studied, indicating equivalent diastolic ventricular function. This study demonstrates that right and left ventricular stroke volumes increase by approximately 10-fold from 20 to 40 weeks gestation in the normal human fetus. It also demonstrates, within the limitations of the equipment, that right ventricular stroke volume exceeds that of the left ventricle, thus confirming right ventricular dominance in utero. Circulation 74, No. 6, 1208-1216 TWO-DIMENSIONAL echocardiographic imaging of the fetal heart has permitted accurate definition of intracardiac anatomy and characterization of the growth patterns of the four cardiac chambers throughout the second and third trimesters.'-Echocardiography has also enabled recognition of cardiac rhythm distur-

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suMMARY Treatment with vasodilators in heart failure has not always produced a useful improvement in the haemodynamic responses to exercise, and in many cases early drug tolerance has further limited the potential of this type of treatment. In a study to evaluate the efficacy of felodipine, a new calcium antagonist with selective vasodilator properties, in the management of congestive heart failure 10 patients with congestive heart failure underwent treadmill exercise testing before and during oral treatment with felodipine 30 mg daily. At every level of exercise felodipine lowered the pulmonary capillary wedge pressure, whereas cardiac index and stroke index increased considerably. The haemodynamic improvement was associated with an increase in the duration of exercise to exhaustion. Importantly, these beneficial effects were sustained throughout four weeks of treatment without evidence of drug tolerance. These observations suggest a useful role for felodipine in the long term management of congestive heart failure.In patients with chronic congestive heart failure exercise related fatigue and dyspnoea are the commonest and most troublesome symptoms. The reduced capacity of the failing heart to increase output to meet the metabolic demands of working muscle and the exagerated rise in left atrial pressure largely account for these symptoms. A critical evaluation of specific antifailure treatment must, therefore, examine the influence it has on the haemodynamic responses to exercise. An additional consideration is the long term efficacy of treatment. This is more difficult to assess since the natural history of congestive heart failure involves a variably progressive deterioration in left ventricular function which is not easily distinguished from the development of drug tolerance.Despite

The antianginal effects of diltiazem 180 mg/day and propranolol 240 mg/day, alone and in combination, were investigated in 15 patients with effort related angina in a double blind placebo controlled crossover trial, with each period of treatment lasting four weeks. Patients performed a symptom limited treadmill exercise test at the end of each period of treatment. Mean (SEM) time to onset of angina was increased from 293(32) s when receiving placebo to 347(38) s when receiving diltiazem alone, to 350(30) s when receiving propranolol alone, and further to 421(34) s when receiving diltiazem and propranolol combined. Similar changes occurred in the duration of exercise testing and time to 1 mm ST segment depression. The sum of ST segment depression at peak exercise was reduced by both diltiazem and propranolol alone compared with placebo, and combination treatment produced a further significant improvement. Rate pressure product was significantly reduced at rest and at peak exercise after propranolol alone and combination treatment. The study clearly showed the superior value of diltiazem and propranolol combined in effort related angina when compared with either drug used alone.

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