Robert C. Bahler

Absent right pulmonary artery: Problems in diagnosis and management

Abstract Two cases of congenital absence of the right pulmonary artery and one case of probably acquired obstruction of the right pulmonary artery are discussed. Patients with congenital absence of the right pulmonary artery frequently present with pulmonary hypertension during infancy, particularly if there is an associated patent ductus arteriosus. Adults with absent right pulmonary artery may be asymptomatic. The diagnosis may be suspected from the chest roentgenogram and confirmed by pulmonary angiography. Aortography is essential for the recognition of the not infrequent anomalous origin of the right pulmonary artery. Previous surgical results and possible therapeutic approaches to the problem of absent right pulmonary artery are discussed.

Cardiovascular function in potassium-depleted dogs

Abstract Chronic potassium depletion in the dog is associated with multiple cardiovascular alterations. The rate of automaticity of the S-A node appears diminished and its response to a chronotropic stimulus is impaired. The reduced peripheral resistance causes a decline in the characteristic hypertensive response to pentobarbital anesthesia. Cardiac function is not impaired, in the absence of arrhythmias, and contractility seems enhanced since potassium depletion produces a significant increase in the mean systolic ejection rate, a rise in LV dpdt, and a higher LVSW and a trend to increased LVMW at similar levels of LVEDP. These hemodynamic alterations are not associated with light microscopic changes in cardiac muscle.

Left ventricular filling shortly after an uncomplicated myocardial infarction as a predictor of subsequent exercise capacity

Resting measurements of left ventricular systolic function do not reliably predict exercise capacity in patients with cardiac disease. Therefore left ventricular filling shortly after a myocardial infarction was prospectively studied to determine whether it could predict subsequent exercise time. Consecutive patients with an acute infarction underwent Doppler and two-dimensional echocardiography within 36 hours of infarction. The study group was composed of the 26 men who did not have reperfusion, who had an uncomplicated myocardial infarction, and who had undergone symptom-limited stress testing during recovery (modified Bruce protocol, 44 +/- 23 days after myocardial infarction). Systolic function was measured by ejection fraction and a wall motion score. Ventricular filling was assessed by the peak transmitral Doppler velocity in early diastole (E), with atrial systole (A), their ratio (A/E), and the percentage of filling from atrial systole. The only parameter of systolic or diastolic function that correlated with exercise time was E (r = 0.65, p less than 0.001). This relationship was particularly strong for the 16 subjects taking beta blockers at the time of stress testing (r = 0.88, p less than 0.001). Stepwise multivariate regression analysis showed that only E and beta blocker therapy at the time of stress testing contributed to the model predicting recovery exercise time (R2 = 0.55). In summary, E, measured soon after an uncomplicated myocardial infarction, is one factor that predicts exercise capacity during recovery.

A geometric method of measuring the left ventricular ejection fraction on gated Tc-99m sestamibi myocardial imaging

Geometric measurements of the left ventricular diameters as used in biplane angiocardiography and echocardiography were applied to gated SPECT Tc-99m sestamibi myocardial scintigrams in order to calculate the left ventricular ejection fraction. These measurements take no longer than 5 minutes and require no additional computer software. In a review of 79 examinations, the left ventricular ejection fraction calculated using these measurements correlated well with the echocardiographically estimated ejection fraction (r = 0.78, P < 0.0001). The technique is highly reproducible with an intraobserver correlation of r = 0.94 and interobserver correlation of r = 0.93.

Use of Tc-99m sestamibi infusion for detection of hibernating myocardium: A preliminary report

To evaluate whether a prolonged infusion of Tc-99m sestamibi allows for visualization of viable myocardium in areas of hypoperfused myocardium, 25 patients were prospectively studied. Each patient was imaged four times in two consecutive days in the following manner: day 1:1) immediately after injection of Tl-201 at rest, 2) 1 hour after a bolus injection of Tc-99m sestamibi at rest; and day 2: 1) imaging in the Tl-201 window for 24 hour redistribution, 2) imaging after a 1-hour infusion of Tc-99m sestamibi. The two Tc-99m sestamibi and two Tl-201 studies were evaluated for presence of redistribution. This was present both on the Tl-201 and Tc-99m sestamibi studies (concordant) in 13 cases, and absent on both the Tl-201 and Tc-99m sestamibi studies (concordant) in 9 cases. In two cases redistribution was seen on the Tl-201 images only, and in one case it was seen on the Tc-99m sestamibi images only (discordant). Tc-99m sestamibi infusion may provide information about the presence of viable myocardium which is similar to that provided by Tl-201 24-hour imaging.

Cardiac venous blood flow in atrial pacing versus exercise-induced angina pectoris

Thirteen patients with angina pectoris underwent measurements of great cardiac vein blood flow at rest, with the onset of angina pectoris induced by atrial pacing, and again during angina pectoris induced by exercise in order to compare the regional coronary blood flow response to differing myocardial stresses. All patients had significant obstructions of the left anterior descending artery. Exercise-induced angina, compared to pacing-induced angina, was associated with a higher systolic pressure, higher left ventricular end-diastolic pressure, and a lower heart rate. Indices of myocardial oxygen demand, that is, the systolic pressure-heart rate product and the tension-time index, increased to a similar degree during both types of myocardial stress and great cardiac vein blood flow paralleled these changes. We conclude that in a given patient the level of regional coronary blood flow is similar at the onset of either pacing- or exercise-induced angina, despite significant differences in the hemodynamic response to these myocardial stresses.