Near-fatal neonatal coronary ischaemia associated with intermittent aortic regurgitation: successful surgical treatment

An infant presented with features suggestive of an anomalous left coronary artery was found to have normal origins of both coronary arteries. Echocardiography during episodes of ischaemia showed marked aortic regurgitation with retrograde coronary flow. The left coronary leaflet was mildly hypoplastic. Surgical re-suspension of this leaflet prevented aortic regurgitation and the patient had no further symptoms and recovered cardiac function.

Role of oxygen-derived free radicals in canine reperfusion arrhythmias

The role of oxygen-derived free radicals in reperfusion arrhythmias was investigated in open-chest anesthetized dogs. The left anterior descending coronary artery was cannulated and perfused by an arterial bypass shunt. Ischemia was produced for 15 min by shunt occlusion and retrograde diversion of collateral blood flow. Dogs (n = 12) were treated with saline, N-(2-mercaptopropionyl)glycine (50 mg/kg), deferoxamine (10 mg/kg), superoxide dismutase (15,000 U/kg) plus catalase (55,000 U/kg), or dimethylthiourea (500 mg/kg). All agents were infused intravenously for 1 h starting 30 min before occlusion and continuing for 5 min of reperfusion. There were no differences in mean arterial blood pressure, heart rate, antegrade coronary flow, retrograde coronary flow, or size of the risk region among the five treatment groups. None of the dogs developed ventricular fibrillation during occlusion, whereas 88% of the 60 dogs fibrillated upon reperfusion. The antioxidant interventions did not alter the incidence of reperfusion-induced ventricular fibrillation compared with the saline-treated controls. The results suggest that free radicals do not play a role in lethal canine reperfusion arrhythmias.

Retrograde coronary flow is limited by time-varying elastance

The study examined the influence of left ventricular pressure (PLV) on coronary arterial flow and pressure. In eight anesthetized open-thorax goats with cannulated and artificially perfused left main coronary artery, the PLV was disturbed by aortic occlusions. In the constant pressure perfusion (CPP) protocol the response of systolic arterial inflow on a change in PLV was studied with fixed perfusion pressure and at several perfusion pressure levels. Similarly, in the constant flow perfusion (CFP) protocol the response of systolic perfusion pressure was examined with fixed levels of perfusion flow and repeated for several flow levels. The results show an early systolic response determined by PLV for both protocols. Midsystolic responses were almost absent in the CPP protocol but present in the CFP protocol. At CPP, the effect of a change of PLV on arterial flow in mid systole was only 20% of that on early systolic flow with intact coronary tone and 33% with adenosine-induced vasodilation. At CFP the pulsations in perfusion pressure were 30% of PLV pulsations, both with intact tone and vasodilation; in contrast with the CPP results, no difference for this value was found in different stages of systole. We suggest that stiffness of cardiac muscle determines the influence of PLV on coronary flow. The difference in mid systolic relations between the CPP and CFP protocols is explained by the difference in time constants induced by the perfusion system. The results are best explained by a synthesis between the intramyocardial pump model and the elastance concept.

Effect of Aortic Stenosis on Coronary Flow Dynamics: Studies in an In-Vitro Pulse Duplicating System

The dynamics of retrograde coronary flow in aortic valvular stenosis was investigated in an in-vitro pulse duplicating system which had the capability of simulating coronary flow. The ventricular chamber of the pulse duplicator consisted of an opaque elastic sac molded from rubber in the shape of a left ventricle. The aortic test section consisted of an acrylic mold of the root of the aorta of a calf, which included the sinuses of Valsalva and the entrance region of both the left and right coronary arteries. Flow in the left coronary artery was modeled to deliver both a systolic and a diastolic component of flow. Studies were performed with normal porcine valves in the aortic and mitral positions and were repeated with a human stenotic valve in the aortic position. Pressures were measured in the aorta, left ventricle, and at the ostium of the left coronary artery with catheter-tip micromanometers. In the presence of a normal aortic valve, total coronary flow was adjusted to 120 ml/min of which 21 percent of the flow occurred during systole. The phasic pattern of coronary flow was similar to that shown in vivo. In the presence of a stenotic aortic valve, a small amount of retrograde coronary flow (<1 percent of total coronary flow) was observed; and this occurred during the initial phase of systole. Retrograde coronary flow during systole appears to have resulted from compression of the collapsible segment of the simulated coronary artery. This was caused by the elevated simulated intramural pressure.