DEVELOPMENT OF PULMONARY HYPERTENSION IN MITRAL STENOSIS

Radiographic inversion of pulmonary blood flow in acute asthma

Chest radiographs are obtained routinely in children hospitalized with asthma but are considered to be of low utility. We describe a previously unreported radiographic inversion of pulmonary artery flow patterns in the chest films of a majority of children and young adults hospitalized for asthma. Seventy-five hospital records of 65 patients aged 2 to 25 years (mean 9.2) admitted for asthma during the calendar year 1991 were reviewed. As compared with the normal pattern, patients with inverted vascularity were younger (mean age 6.75 years), tended to be admitted through the emergency department, and had significantly more signs of labored breathing, such as tachypnea, retractions, nasal flaring, and tachycardia. We propose that the exaggerated respiratory effort in these children raises the transmural pulmonary artery pressure, impeding pulmonary blood flow. This results in distension of the right ventricle, which then compresses the left ventricle in the confines of the pericardium by posterior displacement of the interventricular septum. The resultant loss of left-sided compliance raises the left atrial and pulmonary venous pressures, leading to inversion of vascular markings through the same mechanism as seen in left-heart failure. We conclude that attention to this easily recognized sign will detect presence of the hemodynamically significant respiratory obstruction in asthmatic patients.

Cardiac evaluation

Over the past decade there has been a dramatic, rapid development of new imaging modalities used in the evaluation of the cardiac patient. These newer techniques are frequently complex and specialized in their application and interpretation. Nonetheless, the prevalence of cardiac disease in the United States, and the wide application of these diagnostic tests, mandate that the well-rounded clinician has a basic understanding of the utility of these diagnostic modalities. Unfortunately, the burgeoning field of cardiac imaging seems at times to overshadow our most important basic diagnostic tools, namely, the history, physical exam, chest radiograph, and electrocardiogram (ECG). This review will attempt to impart a basic understanding of the newer cardiac diagnostic tests and their utility in various disease states. Emphasis on the importance of the basic clinical exam and the precise integration of specific diagnostic tests into the cardiac evaluation will be emphasized. The article will deliver a basic review of exercise treadmill testing, echocardiography, radionuclide imaging techniques, magnetic resonance imaging, and cardiac catheterization. It is hoped that this review will impart to the noncardiologist clinician a basic understanding of the cardiovascular diagnostic techniques so that an accurate, precise, cost-effective, efficient diagnostic plan for the patient with cardiovascular disease can be developed and applied.

Assessment of the intrapulmonary ventilation-perfusion distribution after the Fontan procedure for complex cardiac anomalies: relation to pulmonary hemodynamics

In 12 patients who underwent the Fontan procedure for complex cardiac anomalies, lung scanning with xenon-133 was performed to assess the intrapulmonary ventilation-perfusion distribution, and comparison was made with a control group. All data were then analyzed in relation to either pre- or postoperative pulmonary hemodynamic data. In ventilation scans, the intrapulmonary distribution in the right lung was almost normal. In perfusion scans, an abnormal increased upper to lower lobe perfusion ratio greater than the normal value found in the control group was noted in seven patients (58.3%). There was a significant correlation (p less than 0.02) between the upper to lower lobe perfusion ratio and postoperative pulmonary vascular resistance. Furthermore, this perfusion ratio correlated inversely with the preoperative (p less than 0.005) and postoperative (p less than 0.02) right pulmonary artery area index, defined as the ratio of cross-sectional area to the normal value. Of five patients with less than 90% arterial oxygen saturation, four showed an abnormal distribution of pulmonary blood flow greater than the normal perfusion ratio. No patient had evidence of a pulmonary arteriovenous fistula by the echocardiographic contrast study. These results suggest that abnormal distribution of pulmonary blood flow to the upper lung segment may develop in patients after the Fontan procedure, and that insufficient size of the pulmonary artery before operation and the consequent postoperative elevation of pulmonary vascular resistance may be responsible for this perfusion abnormality.

Acute hemodynamic alterations after mitral valve replacement with the glutaraldehyde-treated porcine heterograft prosthesis

Perioperative hemodynamic changes following mitral valve replacement using the porcine heterograft prosthesis were measured in 21 patients with acquired mitral valve disease. Preoperatively, a state of compensatory cardiac failure was suggested by the following: an increased heart rate (HR) (96 beats per minute); low cardiac and stroke volume (SVI) indices (2.3 +/- 0.10 L/min/m2 and 25 +/- 2 ml/beat/m2); and increased systemic vascular resistance (SVR) (1,626 +/- 116 DYNE SEC CM-5). Bothe the mean pulmonary artery PAP) and pulmonary capillary wedge pressures (PCWP) were elevated as well (32 +/- 3 and 22 +/- 2 torr). Immediate hemodynamic improvement followed valve replacement. HR, SVR, PAP, and PCWP all decreased significantly. Twenty-four hours after valve replacement, PAP (23 +/- 1 torr) and PCWP (13 +/- 1 torr) demonstrated marked declines, SVR was reduced by one-third (1,173 +/- 87 dyne sec cm-5), HR had decreased by 10 beats per minute, and SVI had increased to 30 +/- 2 ml/beat/m2. The prompt circulatory improvement of patients soon after mitral valve replacement using the porcine heterograft compares favorably with studies in which other valve types were employed and in which postoperative cardiovascular depression was encountered frequently.

The pulmonary pressures in pulmonary venous obstruction

The contour of the pulmonary artery wedge pressure tracing in a case of pulmonary venous obstruction was unique and may be diagnostic. Wedged pressures were obtained in both a pulmonary artery and a pulmonary vein on recatheterization of a 5-year-old boy with total anomalous pulmonary venous drainage to the superior vena cava on whom an anastomosis of the confluence of the pulmonary veins to the left atrium with loose ligation of the vertical vein had been done at 2 months of age. The pulmonary artery wedge pressure (oxygen saturation, 97%) was 31/18 (mean, 22) mm Hg and its contour was almost identical to that of the pulmonary artery pressure. A similar contour was obtained in the pulmonary vein, for both wedged and free pressures. The similarity of the pulmonary artery wedge pressure to that in the free pulmonary artery may lead to the conclusion that the catheter is not wedged when actually it is. Doubt can be resolved by withdrawing fully saturated blood. Extreme stenosis between the confluence of the pulmonary veins and the left atrium may cause the pulmonary artery wedge to reflect pulmonary arterial rather than left atrial pressure and pulse form.

Correlation of hemodynamic data and pulmonary angiography in mitral stenosis

The abnormalities of pulmonary arterial blood supply in mitral stenosis, consisting primarily of constriction of lower lobe vessels with resultant upper lobe preferential flow, was assessed by means of pulmonary angiography in 30 patients with mitral stenosis uncomplicated by other cardiac diseases. The abnormalities in blood flow correlated best with both the pulmonay artery pressure and the pulmonary arteriolar resistance, and only reasonably well with the area of the mitral valve and the pulmonary capillary wedge pressure. It is suggested that the reversal of the normal lower lung field preferential blood flow in mitral stenosis is primarily a function of pulmonary artery hypertension due to increased pulmonary arteriolar resistance.

Similarly, the width of the right main pulmonary artery as measured on pulmonary angiograms correlated well with both the pulmonary artery pressure and pulmonary arteriolar resistance and less well with the area of the mitral valve. Pulmonary artery size in mitral stenosis is most likely a function of the severity of the pulmonary arteriolar resistance as reflected in the pulmonary artery pressure.