SUMMARY1. Recent experimental data support the view that prostaglandins might be involved in autoregulation of coronary blood flow. Since indomethacin blocks prostaglandin synthesis, the present study was performed to determine whether indomethacin also inhibits coronary vasodilatation induced by hypoxia.2. Coronary and systemic haemodynamic and metabolic effects of hypoxia (5 % and 8 % oxygen in nitrogen) were studied in intact, anaesthetized and vagotomized dogs before and after indomethacin. 3. 30 and 60 min after administration of indomethacin coronary blood flow increases produced by hypoxia were considerably lower than those before indomethacin.4. These results are held to lend support to the hypothesis that prostaglandins are involved in the autoregulation of coronary blood flow.

An asymptomatic congenital cardiac diverticulum was seen on a routine chest film in a 45-year-old man. Right atrial and left ventricular cineangiography showed that the diverticulum communicated independently with both ventricles. There was no evidence of heart failure, arrhythmia, or mural thrombus, and surgery was not deemed necessary.

A technique for measurement of retrograde coronary blood flow in intact anesthetized dogs is described. Occlusion of the coronary artery is produced by the inflation of a small rubber balloon at the tip of a no. 9 cardiac catheter placed under fluorescopy in a branch of the left coronary artery. Blood which bleeds back from the occluded coronary artery through the no. 9 catheter is diverted into a small reservoir of 1-ml capacity. The time to fill this reservoir is recorded electrically. Retrograde coronary blood flow is calculated from the time required to fill this reservoir. Results indicate good repeatability of meadurements. The technique seems to be a simple, adequate, and convenient means for assessing agents for possible vasodilator action on the collateral circulation in intact animals.

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