Off-pump coronary bypass surgery causes less immediate postoperative coronary endothelial dysfunction compared to on-pump coronary bypass surgery.
OBJECTIVE
In this study a comparison of the vascular reactivity in the coronary circulation was investigated by injection of acetylcholine (ACh) and adenosine (ADO) in coronary bypass patients, operated on with or without the assistance of heart-lung machine. The patients operated on with heart-lung machine were further divided into subjects with stable or unstable angina pectoris.


METHODS
Nine patients with stable angina pectoris subjected to off-pump surgery (target arterial occlusion time of 11+/-0.5 min) and 18 patients subjected to on-pump surgery (nine patients with stable angina and nine patients with unstable angina; cross-clamp time of 43+/-3 and 32+/-2 min, respectively), received ACh (10 microg) and ADO (18 microg) given as bolus injections into a vein-graft anastomosed to a coronary vessel. The blood flow in the vein-graft (i.e. indirectly the flow in the targeted coronary circulation) and hemodynamics were observed.


RESULTS
In the off-pump group, ACh evoked an increase with +14+/-12% of control in coronary blood flow, while in the stable on-pump group ACh decreased the blood flow with -60+/-7% of baseline and in the unstable on-pump group the flow was decreased with -38+/-8% of baseline (P<0.001 between the stable on- and off-pump groups, no significant difference between the stable and unstable on-pump groups). ADO significantly increased the coronary blood flow in all three groups; with +81+/-14% in the off-pump patients; with +95+/-14% in the stable on-pump group and with +74+/-13% in the unstable on-pump group (P<0.01 compared to baseline for all three groups). Neither ACh nor ADO injection caused any changes in hemodynamics.


CONCLUSIONS
The present study demonstrates that on-pump coronary bypass surgery appears to be more harmful to the coronary endothelium, in terms of ACh-induced vasoconstriction, compared to off-bypass pump surgery. Furthermore, there is no significant difference in direct smooth muscle vascular reactivity between off-pump and on-pump coronary bypass surgery. No apparent dissimilarities in endothelial dysfunction were observed in the stable and unstable on-pump groups suggesting other causes for differences in post-operative outcome for these patients.
Lockowandt
U
U
Department of Thoracic Surgery, Karolinska Hospital, 171 76 Stockholm, Sweden. ulf.lockowandt@ks.se
Franco-Cereceda
A
A
D000109:Acetylcholine; D000241:Adenosine; D000328:Adult; D000368:Aged; D000789:Angina, Unstable; D001026:Coronary Artery Bypass / Q000379:methods*; D003326:Coronary Circulation / Q000502:physiology; D005260:Female; D006355:Heart-Lung Machine; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014661:Vasoconstriction / Q000502:physiology
D000241:Adenosine; D000109:Acetylcholine