HAEMODYNAMIC STUDIES

Abstract

SummaryHaemodynamic studies have been made, with heart catheterization and measurement of the cardiac output by the direct Fick method, both at rest and during work. This series comprises 17 cases of Friedreich's ataxia with a varying duration of the disease and grade of physical handicap. In every case, the ECG shows signs of cardiomyopathy. The following results are obtained.1. There is no pressure gradient across the pulmonary valve, and no cardiac malformations are disclosed.2. Selective angiography in two cases shows a distinct systolic contraction of the infundibulum of the right ventricle, but no real obstruction. Persistence of contrast medium in the right ventricle indicates its incomplete emptying.3. Left ventricular hypertrophy is well depicted at angiocardiography, and the walls seem to be rigid during the cardiac cycle.4. The pressure in the right atrium, both the initial and end‐diastolic pressure in the right ventricle, and the mean pulmonary wedge pressure are elevated, and significantly correlated to the duration of the neurological syndrome. Significant differences are present between the groups with and without walking ability with respect to all these pressures.5. The rise in pressure in cases without enlargement is attributed to a raised filling resistance, presumably secondary to increased resistance or decreased compliance of the walls of both ventricles.6. The mean pressure in the pulmonary artery is moderately elevated, corresponding to the rise in pulmonary wedge pressure. Increased pulmonary vascular resistance is present in two cases.7. The oxygen uptake is low in relation to heart rate, i.e., there is a low oxygen pulse. The low oxygen pulse is combined with a somewhat elevated arterio‐venous oxygen difference.8. With few exceptions, the stroke volume is distinctly small, demanding a high heart rate to provide an adequate cardiac output. During work, the stroke volume decreases in several cases, indicating myocardial dysfunction.9. The cardiac output differs individually, but is most often hypokinetic. The cardiac index at rest is, however, more than 5 lit/min/m2 in four cases, despite a decreased blood flow in the extremities. This is suggested to be due to a redistribution of the cardiac outflow.10. Mechanical systole of the left ventricle shows a shorter duration in relation to heart rate than normally, the duration being significantly shorter in group III + IV than in group I + II. Ventricular hypertrophy, the demand for a prolonged filling time and a small stroke volume are considered to be factors contributing to shortening of the duration of systole.