Myocardial contractile performance, preload recruitable stroke work relationships, and histomorphometric changes following off-pump and on-pump coronary bypass grafting of the left internal thoracic artery to the left anterior descending artery.

Abstract

BACKGROUND:

It has been shown that coronary artery bypass grafting without cardiopulmonary bypass (off-pump or OPCABG) preserves better cerebrocognitive, pulmonary, hepatorenal, and blood cell functions compared with onpump surgery because of an attenuated inflammatory response. The degrees of ischemia/reperfusion injury, myocardial protection, and quantitative changes in myocardial contractile performance following OPCABG have not been well documented.

METHODS:

A canine myocardial ischemic injury model (60-minute occlusion of the left anterior descending artery [LAD];; n = 30, 27-35 kg body weight) was used to quantitatively assess postoperative regional left ventricular function (sonomicrometry, micromanometry, preload recruitable stroke work [PRSW]). The left internal thoracic artery (LITA) was anastomosed to the distal LAD in off-pump and on-pump CABG with antegrade/retrograde cold blood cardioplegic arrest (cardiopulmonary bypass time, 58 +/- 2 minutes; cross-clamp time, 28 +/- 3 minutes). Anastomosis patency and endothelial changes at the anastomoses were analyzed with light microscopy and histopathologic techniques.

RESULTS:

LAD occlusion resulted in ischemia/infarction (creatine kinase-MB levels on-pump and off-pump versus the baselines were, respectively, 17.5 +/- 1.4 mg/L versus 1.5 +/- 0.3 mg/L [P <.05 by analysis of variance and t test]; and 19.5 +/- 1.8 mg/L versus 2.1 +/- 0.4 mg/L [P < .05]) and a significant decrease in regional myocardial function in both groups (50% decrease of PRSW). Revascularization led to reestablishment of myocardial function to baseline (on-pump and off-pump PRSW were, respectively, 57-196 10(3) erg.cm-2; [mean, 127 x10(3) +/- 25 x 10(3) erg . cm-2] and 81-98 10(3) erg.cm-2; [mean, 90 x 10(3) +/- 15 x 10(3) erg .cm-2]). All anastomoses were widely patent in all animals 14 days after surgery. There was a significantly increased intimal thickening at the 8-0 monofilament suture line in the off-pump LITA-to-LAD anastomoses.

CONCLUSIONS:

Compared with most commonly applied myocardial preservation techniques (cardiopulmonary bypass, hypothermic blood cardioplegic arrest), OPCABG provides at least equal myocardial protection, because there were no significant quantitative differences between off-pump and onpump CABG in myocardial contractile performance following LITA-to-LAD revascularization. The more prominent intimal thickening observed in OPCABG procedures is worrisome and deserves further investigation.

• Authors: Hartmuth B Bittner, Peter V Ching
• Journal: The heart surgery forum (Heart Surg Forum) Vol. 6 Issue 3 Pg. E52-8 ( 2003) ISSN: 1522-6662 [Electronic] United States
• PMID: 12821440 (Publication Type: Journal Article)

Topics

• Animals
• Cardiac Output, Low (etiology)
• Coronary Artery Bypass (adverse effects, methods)
• Coronary Disease (surgery)
• Dogs
• Inflammation (prevention & control)
• Internal Mammary-Coronary Artery Anastomosis (adverse effects, methods)
• Models, Animal
• Myocardial Contraction (physiology)
• Myocardial Ischemia (surgery)
• Myocardial Reperfusion (methods)
• Ventricular Function, Left (physiology)