Refinement of pig retroperfusion technique: Global retroperfusion with ligation of the azygos connection preserves hemodynamic function in an acute infarction model in pigs (Sus scrofa domestica)

Abstract

In ischemic hearts, venous retroperfusion is a potential myocardial revascularization strategy. This study aimed to refine the technical and functional aspects of a pig model of acute myocardial infarction and retroperfusion with respect to the azygos connection. Global retroperfusion after ligation of the ramus interventricularis paraconalis (equivalent to the left anterior descending artery in humans) was performed in 16 Landrace pigs (Sus scrofa domestica). Coronary sinus perfusion was performed in 8 pigs (P+) but not in the other 8 (P-), and the azygos vein was ligated (L+) 4 of the 8 pigs in each of these groups but left open (L-) in the remaining animals. Hemodynamic performance (for example, cardiac output, stroke volume) was significantly better in P+L+ pigs that underwent coronary sinus perfusion with ligation of the azygos vein compared with all other animals. In addition, troponin I release was significant lower in P+L+ pigs (1.7 +/- 1.3 ng/mL) than in P-L- (5.47 +/- 2.1 ng/mL), P-L+ (6.63 +/- 2.4 ng/mL), and P+L- (4.81 +/- 2.3 ng/mL) pigs. Effective retrograde flow and thus hemodynamic stability was achieved by ligation of the azygos vein. Therefore, experiments focusing on global retroperfusion will benefit from effective inhibition of the blood flow through the azygos vein.

Figure 1.

The operating field seen from the perspective of the surgeon; cranial is to the left. (A) A balloon-tipped catheter (1) is placed transatrially into the coronary sinus and connected to an aortic canula, creating an aorta-to-coronary–sinus shunt (3). The ramus interventricularis paraconalis (2) and its concomitant vein (vena cordis magna) also are shown. (B) The facies diaphragmatica of the heart is shown, with a view of the coronary sinus (1) and the vena cava caudalis (3). (C) Preparation of the vena azygos sinistra after creation of a pericardial window (3). The azygos vein (2) is shown before ligation, for which a suture is placed by means of a clamp (1). (D) The vena cava cranialis (1), azygos vein (ligated with a tourniquet; 2), and the pericardial window (3).

Figure 2.

Intraoperative retrograde venograms of the connection of the venus azygos sinistra; cranial is to the left. (A) Retrograde venogram of the vena azygos sinistra (*) before ligation; a balloon-tipped catheter (#) is placed transatrially into the coronary sinus (∧). The cardiac venous system (for example, vena cordis magna) lacks contrast because of backflow of blood to the vena azygos sinistra. (B) Venogram of the vena cava caudalis (*) is shown to distinguish the vena cava caudalis from the vena azygos sinistra (#, balloon-tipped catheter). (C) Venogram of the cardiac venous system. The vena azygos sinistra (∧) contains contrast material just to the point of ligation (X). The tourniquet (o), vena cordis magna (*), and sinus coronarius (#) are shown. (D) After backflow of the contrast medium has been blocked by ligation of the azygos vein, the vena cordis magna (∧) is now visible. Visualization of the vena cordis magna indicates effective retrograde flow through the aorta-to-coronary– sinus catheter. In addition, the vena cordis media (+), sinus coronarius (#), and tourniquet (o) are shown.

Figure 3.

Changes in cardiac output after LAD ligation: effect of azygos vein ligation. Data are presented as percentages of the preoperative (preop.) cardiac output. Each line represents an individual animal. The solid line represents the mean value (error bars, 1 SD). The 4 pigs in the P+L+ group comprise the upper cluster of data points, whereas those of the P+L–group comprise the lower cluster. 0 min, start of LAD ligation; 60 min, start of reperfusion. *, Significantly (P < 0.05) different from preoperative value.