STUDIES ON THE CORONARY ARTERIES OF THE HUMAN HEART

¹ Department of Physiology, University of Cairo, Egypt

Coronary arteries in man are usually relaxed at death, and when heated to 37°, contract. In certain conditions such as arteriosclerosis and luetic heart disease the arteries relaxed when heated to 37°, and are therefore presumably contracted at death.

Adrenalin is found to decrease the coronary flow of the perfused beating human heart, and to increase the flow in a standstill heart. It contracts some coronary artery rings and relaxes others with similar dilutions of the drug.

Ergotoxin has little or no effect on the coronary rings of the human heart alone, but when added in dilutions 1:50,000 to rings contracted by adrenalin, it causes relaxation. This observation supports the theory that there are sympathetic vasoconstrictor and vasodilator nerves in the coronary system.

Pituitrin causes slowing of the heart rate and a decrease in the coronary flow, with increase in amplitude of contraction during the first hour of perfusion. Later and particularly when the heart is dilated, the drug may increase the coronary flow and increase the rate and amplitude of the heart beat. The latter effect is due to an increased tone of the heart muscle. Pituitrin constricts human coronary artery rings. Caffein, sodium nitrite, papaverin and histamine increase the coronary artery flow. Caffein increases the rate and amplitude of the heart-beat; sodium nitrite has little or no effect. Morphine and papaverine diminish the rate and amplitude of the heart beat.

Camphor in large doses increases the coronary flow, but has no effect on the heart rate, amplitude of contraction, or on the conducting system of the heart.

Nicotine diminishes the coronary flow and increases the heart rate and amplitude of the heart-beat. Atropin increases the heart rate and diminishes the coronary flow. Pilocarpin decreases the heart rate and increases the coronary flow.