Intracoronary shunt insertion prevents myocardial stunning in a juvenile porcine MIDCAB model absent of coronary artery disease.
OBJECTIVE
The relevance of regional LV myocardial ischemia/reperfusion induced by temporary left anterior descending (LAD) coronary artery occlusion during minimally invasive direct coronary artery bypass (MIDCAB) grafting is controversial. The purpose of our study was (1) to determine the impact of conventional LAD occlusion during left internal thoracic artery (LITA)-LAD anastomosis on regional LV myocardial ischemia and function, and (2) to evaluate if intra-LAD shunt insertion during LITA-LAD anastomosis prevents potential regional LV ischemia and dysfunction in a pig model.


METHODS
In 20 anesthetized, mechanically ventilated pigs we performed LITA-LAD anastomosis on the beating heart without cardiopulmonary bypass during either 15 min LAD occlusion (occlusion-group; n = 10) or 15 min intra-LAD shunt insertion to maintain blood supply to the myocardium beyond the anastomosis (shunt-group; n = 10). Besides standard hemodynamics we determined the global and regional LV wall motion score index (WMSI) using epimyocardial echocardiography. To quantitate structural myocardial alteration we determined the inducible heat-shock protein-70 (HSP-70) in LV anterior wall myocardial biopsies. Data were recorded at baseline, at 15 min of LAD occlusion or shunt insertion, respectively, and at 30 min of reperfusion. At the end of the experiments we determined myocardial adenine nucleotide (ATP, ADP, AMP) and glycogen content.


RESULTS
In both groups WMSI was not significantly different at 15 min LAD occlusion or shunt insertion, respectively, as compared to baseline. However, at 30 min reperfusion both global and regional WMSI demonstrated significant LV dysfunction in the occlusion-group, whereas LV function in the shunt-group remained normal. This was associated with higher myocardial HSP-70 expression in the occlusion-group (P < 0.05). Myocardial adenine nucleotide and glycogen contents were significantly better preserved in the shunt-group.


CONCLUSIONS
Our data show that in a porcine MIDCAB model 15 min LAD occlusion and 30 min reperfusion result in significant myocardial stunning. In contrast, maintenance of LAD perfusion using intracoronary shunt insertion minimizes ischemia/reperfusion injury and prevents regional LV dysfunction. Although our experiments were conducted in healthy pig hearts absent from coronary artery disease, similar results may--at least partially--be expected in humans, and thus, intracoronary shunts could be a useful tool for myocardial protection during 'off-pump revascularization'.
Dapunt
O E
OE
Department of Cardiothoracic Surgery, University of Cologne, Germany. otto.dapunt@medizin.uni-koeln.de
Raji
M R
MR
Jeschkeit
S
S
Dhein
S
S
Kuhn-Régnier
F
F
Südkamp
M
M
Fischer
J H
JH
Mehlhorn
U
U
D000227:Adenine Nucleotides / Q000378:metabolism; D000714:Anastomosis, Surgical; D000818:Animals; D019917:Blood Vessel Prosthesis Implantation; D001026:Coronary Artery Bypass / Q000379:methods*; D003327:Coronary Disease / Q000150:complications; D004195:Disease Models, Animal; D004452:Echocardiography; D005260:Female; D006003:Glycogen / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006439:Hemodynamics; D008297:Male; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D017682:Myocardial Stunning / Q000000981:diagnostic imaging / Q000378:metabolism / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism; D013552:Swine
D000227:Adenine Nucleotides; D018840:HSP70 Heat-Shock Proteins; D006003:Glycogen