Conditions for "coronary steal" caused by coronary vasodilator in man

This study was undertaken to assess the conditions necessary to cause the "coronary steal" phenomenon in human subjects. We studied 42 patients (36 males, 6 females, ages 27--70 years) with known or suspected coronary artery diseases using continuous monitoring of the changes in blood pressure and electrocardiogram, thallium-201 myocardial imaging and selective coronary arteriography. Dipyridamole in a dose of 0.4 mg/Kg was given as an intravenous infusion for 4 min and thallium-201 was injected at the 4th minute after completion of the dipyridamole infusion. None of the 20 patients without significant coronary artery disease complained of anginal chest pain or showed ischemic S-T segment depression. Dipyridamole images showed no perfusion abnormalities in 17 of the 20 patients. On the other hand, in 4 of the 22 patients with significant coronary artery disease, anginal chest pain accompanied with S-T segment depression occurred after the dipyridamole infusion. Dipyridamole images showed perfusion abnormalities in 18 of the 22 patients. The 4 patients who experienced an anginal attack had 3 vessel disease on the coronary arteriogram and showed regional perfusion defects on scintigrams corresponding to the regions receiving collaterals. Before the onset of pain, the double product (heart rate X systolic arterial pressure) was unchanged significantly but there was a reduction in the systemic blood pressure. The overall data exhibit the following conditions under which attacks of angina pectoris are induced by dipyridamole: 1) the presence of multiple vessel disease, 2) a fall in systemic blood pressure, and 3) regional malperfusion caused by dipyridamole.

A study of brain development in low-birth-weight infants by computerized tomography

Follow up study was conducted by brain CT scans on fullterm and premature infants for a period of 3 years following birth. The results were: 1. Low density areas were observed symmetrically in the frontal region in premature infants for 3 to 4 months after birth. However, they disappeared after 44 weeks of postconceptional age irrespective of either gestational age or birth weight. 2. At 40 to 56 weeks postconceptional age extracerebral space was most frequently found. The extracerebral space was found to exist longer in proportion to the shortness of gestational age and to a lower birth weight. 3. Some infants in the group who showed definite extracerebral space required persistent artificial ventilation for a long period. This may indicate that could exist a relationship between the occurrence of this particular space and hypoxia. 4. We consider that the extracerebral space in CT scan can be a useful parameter to assess the process of brain growth in premature infants.

[Long-term use of vasodilators in patients with congestive cardiomyopathy (author's transl)]

Three patients with congestive cardiomyopathy were studied for the acute and chronic hemodynamic effects of vasodilators using right heart catheterization, echocardiography and exercise tolerance test. All of the three were in congestive heart failure and were on digoxin and furosemide. Various vasodilators were used, which included isosorbide dinitrate, hydralazine, phentolamine and prazosin. Favorable acute hemodynamic effects were seen in all three. However, on continued use, all three showed evidence of tolerance to vasodilators by hemodynamic measurements. The first patient died in heart failure, complicated by pulmonary infarction. The second died suddenly after discharge from the hospital, while maintained in good control of the congestive heart failure. The third patient had recurrence of congestive heart failure after discharge, which was controled by the hospitalization and change to different vasodilator agents. Favorable hemodynamic effects were readily seen following vasodilators in patients with confestive cardiomyopathy. However, on chronic use some tolerance to the agents was observed. This needs to be investigated as to the mechanism so these agents can be more effectively utilized in these patients who are usually resistant to the conventional mode of therapy.