Laboratory Investigation Congenital Heart Disease

Left-to-right (L-R) shunting across a ventricular septal defect (VSD) often involves a direct VSD-pulmonary arterial component (jet) that surges from the VSD immediately into the pulmonary artery. We used the thermodilution technique in dogs with acute experimental VSD to quantify this component. In dogs with supracristal VSD (n = 7), the direct component represented 76 + 4% (mean ± SE) of the total L-R shunt on average, vs 39 ± 7% (p < .001) of the total in dogs with infracristal VSD and the same level of L-R shunting (n = 6). The direct component can be expected to impose additional hyperkinetic forces on the pulmonary artery since it is driven by the left ventricular pressure. Although not yet clinically proven, we speculate therefore that patients with supracristal VSD may be at greater risk of becoming jeopardized by late-onset pulmonary vascular obstructive disease. Since a part of the total shunt other than the direct component dropped into the right ventricle, the right ventricle bore only 24% of the total shunt in supracristal VSD, but 61% in infracristal VSD. We also found that the amount of direct component was decreased, and therefore another part must have increased, as the pulmonary vascular resistance was artificially raised. As a second speculation, therefore, we suggest that patients with supracristal VSD may have less enlargement of the right ventricle than those with infracristal VSD before pulmonary hypertension develops. Circulation 73, No. 4, 775-783, 1986. IT IS a common finding in routine cineangiographic examinations of patients with ventricular septal defect (VSD; figure 1) that part of the left-to-right (L-R) shunted blood surges from the defect immediately into the pulmonary artery without being trapped in the right ventricle. The remainder of the shunted blood drops into the body of the right ventricle, and is then delivered to the pulmonary artery. In this report, the former portion is referred to as the direct VSD-PA component, with a flow fdp, and the latter as the VSD-RV-PA component, with a flow fdr, Clinically, the direct VSDPA component is often termed a jet. The present study was undertaken to investigate the pathophysiologic From the Departments of Cardiology and Cardiovascular Dynamics, National Cardiovascular Center, Suita, Osaka, and Department of Cardiovascular Surgery, Ehime Prefectural Central Hospital, Matsuyama, Ehime, Japan. Address for correspondence: M. Nakai, M.D., Department of Cardiovascular Dynamics, National Cardiovascular Center, Suita, Osaka 565, Japan. Received July 12, 1985; revision accepted Nov. 21, 1985. Vol. 73, No. 4, April 1986 significance and characterize the hemodynamic nature of such an intracardiac pattern of shunt flow. Pulmonary vascular obstructive disease is known to represent one of the most serious clinical problems in treating patients suffering from congenital heart disease with shunt. ' It has been theorized that hyperkinetic hemodynamic forces imposed on the pulmonary arterial wall are major factors in the genesis of vascular disease.>Elevation of the pulmonary arterial pressure, wide pulse pressure, and/or an increase in flow may certainly contribute to the extra hemodynamic forces.3' 6 Our group has suggested in a preceding report7 that in patients with VSD, one possible additional putative hemodynamic factor, which if not a major causative factor is at least an accelerating one, is the presence of the direct VSD-PA component. In that study, we quantified the component in dogs with experimental VSD produced for a short period at the entrance of the outflow tract of the right ventricle and found that it occu775 by gest on A ril 0, 2017 http://ciajournals.org/ D ow nladed from