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Updated: Aug 9, 2026
Surgical Swine Model of Chronic Cardiac Ischemia Treated by Off-Pump Coronary Artery Bypass Graft Surgery
Published on: March 27, 2018
Off-pump coronary bypass surgery causes less immediate postoperative coronary endothelial dysfunction compared to
U Lockowandt1, A Franco-Cereceda
1Department of Thoracic Surgery, Karolinska Hospital, 171 76 Stockholm, Sweden. ulf.lockowandt@ks.se
Insights
Coronary bypass surgery using a heart-lung machine (on-pump) harms coronary artery function more than surgery without it (off-pump). Both methods show similar direct smooth muscle responses, suggesting other factors influence patient outcomes.
Area of Science:
- Cardiovascular Surgery
- Vascular Physiology
- Surgical Outcomes
Background:
- Coronary artery bypass grafting (CABG) is a common procedure for coronary artery disease.
- The use of a heart-lung machine (on-pump) versus off-pump techniques may influence post-operative vascular function.
- Endothelial and smooth muscle reactivity are critical determinants of coronary blood flow.
Purpose of the Study:
- To compare vascular reactivity in coronary bypass patients undergoing on-pump versus off-pump surgery.
- To investigate the effects of acetylcholine (ACh) and adenosine (ADO) on coronary blood flow in these patient groups.
- To assess differences in endothelial and smooth muscle function based on surgical approach and angina stability.
Main Methods:
- Vascular reactivity was assessed by injecting ACh and ADO into vein grafts in three groups: off-pump stable angina, on-pump stable angina, and on-pump unstable angina.
- Coronary blood flow and hemodynamics were monitored.
- Surgical parameters including occlusion and cross-clamp times were recorded.
Main Results:
- Acetylcholine (ACh) caused significant vasoconstriction in on-pump patients (stable: -60%, unstable: -38%) but vasodilation in off-pump patients (+14%).
- Adenosine (ADO) significantly increased coronary blood flow in all groups (off-pump: +81%, on-pump stable: +95%, on-pump unstable: +74%).
- No significant hemodynamic changes were observed with either agent; no difference in endothelial dysfunction was noted between stable and unstable on-pump groups.
Conclusions:
- On-pump CABG surgery appears more detrimental to coronary endothelial function than off-pump surgery, evidenced by ACh-induced vasoconstriction.
- Direct smooth muscle vascular reactivity is not significantly different between on-pump and off-pump procedures.
- Endothelial dysfunction differences between stable and unstable on-pump groups were not apparent, suggesting other factors contribute to post-operative outcomes.
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.
