Use of contrast echocardiography for evaluation of right ventricular hemodynamics in the presence of ventricular septal defects.

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Abstract
Intracardiac blood flow is altered in the presence of a ventricular septal defect (VSD), with different sizes of defects producing different flow patterns that can be visualized by peripheral injection contrast echocardiography. The utility of these patterns in allowing estimation of right ventricular pressure and resistance to ejection of blood from the right ventricle (RV) was investigated. Forty-four patients underwent 46 contrast echocardiographic procedures, all within 24 h before cardiac catheterization. All patients were placed in 1 of 4 groups based on catheterization findings. Group I, which consisted of patients with no VSD, or a small VSD with a pulmonary-to-systemic flow ratio (Qp/Qs) < 1.5:1 and right ventricular pressure < 1/3 systemic, had echo-dense material appear in the RV only. Group II consisted of those with moderate-sized VSD with Qp/Qs .gtoreq. 2.5:1 and right ventricular pressure 60-80% systemic; in these patients echo-dense material appeared in the RV and in the left ventricle (LV) anterior to the mitral valve. The contrast appeared in the LV in early diastole and cleared from the LV in systole, with none appearing in the aorta or left atrium. Time from the preceding QRS to appearance of echo-dense material in the LV divided by the R-R interval (appearance time to R-R interval ratio) was 0.62-0.69. Group III consisted of those with large VSD, Qp/Qs > 3:1 and systemic right ventricular pressure with low pulmonary vascular resistance and no pulmonary stenosis. These patients had appearance of echo-dense material in the LV during early diastole anterior to the mitral valve as in group II, but the material remained in the LV to be ejected into the aorta. Appearance time to R-R interval ratio was the same as in group II. Group IV consisted of patients with tetrology of Fallot and 1 patient with a large VSD and increased pulmonary vascular resistance. Echo-dense material again appeared in the LV early in diastole and was ejected into the aorta during systole. The appearance time/R-R ratio was significantly less than in groups II or III, allowing a clear separation between those patients in group III from group IV. Contrast echocardiography allows estimation of the right ventricular pressure and evaluation of increased resistance to pulmonary flow due to either pulmonary stenosis (PS) or increased pulmonary vascular resistance in the presence of VSD. This technique also provides a minimally invasive method which may be useful for serial evaluation of such patients, and will permit early detection of developing PS, and possibly increasing pulmonary vascular resistance. Decreasing right ventricular pressure due to spontaneous closure of the VSD may also be detected by this technique.