Assessment of myocardial viability for coronary artery bypass grafting by intraoperative epicardial mapping
Aoyama, T.
Nihon Kyobu Geka Gakkai 35(4): 463-473
1987
ISSN/ISBN: 0369-4739 PMID: 3497996 Document Number: 298005
Coronary artery bypass grafting (CABG) has been demonstrated to enhance the functional capacity of ischemic heart disease patients. However, transmural myocardial infarction will not have a viable myocardium. The purpose of this study is to assess myocardial viability in myocardial infarction (MI) for CABG. Intraoperative epicardial mapping was performed on 28 patients who underwent CABG (26 males and 2 females). There were 15 cases of old MI (OMI) and 13 cases of non-OMI. Epicardial mapping was carried out before cardiopulmonary bypass during regular sinus rhythm. A tripolar hand-held electrode probe was used to record unipolar and bipolar epicardial electrograms simultaneously. The unipolar electrogram was assessed both in shape and amplitude. The term positive and negative was used to describe amplitude from the baseline. A quantitative analysis of abnormally contracting segments from left ventricular angiography was done by superimposing the tracing of end-diastolic and end-systolic frames using the apex and mid-aortic valve as fixed points. Radial lines were drawn from the mid-point of the long axis to the end-diastolic frame every 5 degrees. Anterior and inferior walls were divided into 5 segments every 30 degrees. Each segmental radial shortening (%RS) was calculated. There were QS, QS with Notching, Small q and Normal QRS waves which showed a sequential spike change from QS to Normal QRS in MI. The amplitude of these 4 kinds of electrograms were significantly different from each other. It was -5.1 .+-. 3.8 mv in QS, -0.1 .+-. 5.2 mv in QS with Notching, 6.8 .+-. 3.1 mv in Small q and 11.4 .+-. 3.3 mv in Normal QRS wave. There was a positive correlation between epicardial electrogram amplitude (X) and the corresponding segmental %RS (Y), Y=1.5X + 12.8, r=0.772, p < 0.001. This meant that the higher the epicardial electrogram amplitude was, the better the regional wall contractility was likely to remain in the infarcted area. The result of CABG in MI was studied. Preoperative and postoperative %RS in each area were as follows respectively, 0.5 .+-. 4.7 and 3.1 .+-. 3.0 in the QS area (N.S.), 12.9 .+-. 8.1 and 17.2 .+-. 11.3 in the QS with Notching area (N.S.), 30.5 .+-. 10.2 and 37.2 .+-. 16.8 in the Small q area (p < 0.05), 30.9 .+-. 9.3 and 51.4 .+-. 12.9 in the Normal QRS area (p < 0.001). This suggests non-reversible asynergy in the QS and QS with Notching wave areas and reversible asynergy in the Small q and Normal QRS wave areas. Assessment of myocardial reversibility by the epicardial unipolar electrogram proved to be most useful in providing information about viability in the ischemic myocardium.