Objective: Apical suction devices allow displacement of the heart in off-pump coronary artery surgery. However, high vacuum pressure may injure the suctioned myocardium. It has been demonstrated that partial pressure of oxygen in the myocardium (ptiO(2)) is a sensitive and rapid indicator of myocardial ischemia. The purpose of this study is to evaluate the effect of apical suction on the ptiO(2) as an indirect measure of myocardial perfusion of the ventricular apex.
Methods: Twenty-six patients undergoing elective off-pump coronary surgery were studied. Intramyocardial ptiO(2) was continuously measured using a flexible catheter microprobe (Licox GMS mbH, Kiel, Germany). Patients were divided into two groups. In one group (Group A; n=14), the microprobe was intraoperatively inserted into the myocardium of the left ventricular apex. In the second group (Group B; n=12), the probe was inserted in the anterior wall of the left ventricle. Intramyocardial ptiO(2) monitoring was made with the heart in the resting position and after placing the apical suction device.
Results: In Group A, basal ptiO(2) was 15.3+/-7.4 mmHg. One minute after placing the apical suction device, the ptiO(2) significantly decreased to 2.3+/-1 mmHg (p<0.001). A progressive increase of ptiO(2) was observed immediately after the Xpose suction device was removed. ptiO(2) was 13.6+/-9.1 mmHg 5 min after releasing the suction cup and increased to 27.2+/-12.6 mmHg 20 min later. In Group B, basal ptiO(2) was 17+/-10.3 mmHg. No significant changes were observed in Group B after placing and removing the suction cup.
Conclusions: Apical suction devices lead to severe ischemia of the suctioned myocardium. Collapse of coronary vessels due to vacuum pressure is a possible mechanism. Reperfusion occurs immediately after removing the suction cup and a significant reactive hyperemia is observed.