Haemodynamics in juvenile hypertension at rest and during exercise.

In twenty-eight patients with juvenile hypertension haemodynamic examinations were made at rest and during exercise (600 kpm/min). The cardiac output was determined by the Fick method; venous blood was sampled from a floating catheter introduced into the pulmonary artery; the systemic pressure was measured directly in the brachial artery. In 57% of the juvenile hypertensives the resting cardiac index was higher than 4.5 l/min/m2. The increase was due to an increase in the stroke volume rather than in the heart rate. Of the patients 37.5% had increased cardiac output relatively to the oxygen uptake also during exercise; most of them were hyperkinetic already at rest. The resting systemic resistance was significantly elevated in patients whose resting systolic pressure was greater than 150 mmHg and/or diastolic pressure was greater than 90 mmHg, compared to controls; during exercise the values of systemic resistance lay within normal limits. The systemic pressure responded to the exercise by either a hypertonic or a normotonic reaction. In only 23% of subjects normotensive at rest a hypertonic response to exercise was found.