Flowmeter and¹³³Xenon Clearance Studies of the Blood flow in the Internal Mammary Artery after Intramyocardial Implantation in the Dog

The left internal mammary artery was implanted into the myocardium in 16 dogs. In 8 dogs all major branches of the implant artery were ligated to create a “closed” implant. In the other 8 dogs 3 major branches were left open in the myocardial tunnel, i.e. “open” implants. Blood flow in the implant artery trunk was measured with an electromagnetic flowmeter. The flow value obtained during acute occlusion of the cognate coronary artery was used. Myocardial tissue blood flow in the implantation area was measured by recording the clearance rate of 133Xenon after local intramyocardial injections and during occlusion of the coronary artery. The flow value during occlusion of the implant artery was subtracted from the value with the unclamped artery. The “ischaemic” area was weighed, and the relative flow values were converted to absolute values by multiplying them with this weight. There was a close agreement between the flows obtained with the two methods, (r = 0.86). This indicates that most of the implant flow can be utilized by the myocardium. In the “closed” implant, with a mean implantation time of 86 days, the flow-meter values averaged 1.4 ml/min, and the converted clearance values averaged 2.0 ml/min. For the “open” implant group, with a mean implantation time of 94 days, corresponding values were 2.9 and 2.8 ml/min. The differences between the groups were not statistically significant, which may be due to the small number of dogs studied. Attempts were made to correlate the blood flow to the implantation time. The results indicate that the flow increased with time, at least in the “open” implant group.