Pressure characteristics in arterial grafts for coronary bypass surgery

The haemodynamic properties of arterial grafts were studied by measuring the pressure waveform at the tip of the grafts in 28 patients who underwent coronary artery bypass surgery (CABG). The internal thoracic and gastroepiploic arteries were harvested as pedicles for CABG. Pressure wave of the ascending aorta and arterial grafts were simultaneously recorded with an electrocardiogram under stable haemodynamic conditions before cardiopulmonary bypass. Systolic, diastotic and mean pressures were measured, and mean systolic and diastolic pressures calculated for systolic and diastolic areas divided by time. The ascending aorta showed high sustained diastolic pressure that decreased gradually. Pressures in the internal thoracic and gastroepiploic artery grafts had narrow contours and decreased rapidly. Pressure waveforms in the internal thoracic and gastroepiploic artery grafts had a notch between the systolic and diastolic contours. There was no difference in systolic pressure between the ascending aorta and internal thoracic and gastroepiploic artery grafts. Diastolic pressures were 64(9), 55(7), and 51(6) mmHg in the ascending aorta and internal thoracic and gastroepiploic artery, respectively. Mean(s.d.) pressures were 75(9), 65(9) and 59(7) mmHg in the ascending aorta and internal thoracic and gastroepiploic artery grafts, respectively. Diastolic and mean pressures in the internal thoracic artery grafts were significantly lower than in the ascending aorta but significantly higher than in the gastroepiploic artery grafts. The mean(s.d.) calculated diastolic pressure in the internal thoracic artery grafts was significantly lower than in the ascending aorta but significantly higher than in the gastroepiploic artery grafts. The inferior capacity of flow through the arterial grafts may be mainly attributable to reduced diastolic pressure, which is caused by anatomical characteristics. Arterial grafts originating from a systolic-dominant circulation far away from the heart have a limited ability to supply blood to the diastolic-dominant coronary circulation.