Hans Henrik Dedichen has investigated the circulatory responses to early physical activity after on-pump coronary artery surgery.

(1) Although patients are stable and have good blood flow, skeletal muscle anaerobic metabolism and blood lactate concentrations increase immediately after coronary artery bypass grafting. The increases are linked to anemia and reduced oxygen supply to the tissues, while there is no reduction in the muscles’ ability to absorb oxygen from the blood.

14 patients with stable angina and no exercise restrictions were included in the study. Both immediately before and the morning after cardiac surgery, the patients underwent a light exercise test. Blood lactate concentration was significantly increased after surgery both at rest and during exercise.

(2) The left ventricle is less completely filled with blood during exercise the day after cardiac surgery. Systolic function is intact, but the stroke volume decreases because of the reduced diastolic heart function. This decrease makes the patients feel a higher rate of exertion during light exercise than immediately before surgery.

The 14 patients cycled for a total of ten minutes at a rate of 50-60 rounds per minute and two intensity levels. Dedichen and co-workers examined cardiac function with cardiac ultrasound, and compared the results with a corresponding bicycle test the patients did just before surgery. Patients experienced the test at both intensity levels more tiring the morning after surgery than the day before.

(3) On-pump cardiac surgery might reduce flow-mediated dilation the next day. However, this can be at least partly due to reduced postoperative blood flow rather than reduced endothelial function.

19 patients had their brachial artery flow-mediated dilation examined prior to and the morning after coronary artery bypass grafting. Brachial artery baseline diameter was unaffected by coronary artery bypass surgery, whereas resting blood flow decreased.