Electrical monitoring of myocardium during induced ischemia

Abstract

Resistance and spontaneous electrical activity have been recorded during experimentally induced ischemia of swine heart performed on 9 pigs. Ischemia has been obtained by occlusion the left anterior descending coronary artery (LAD). Four waveforms of electrogram (EG), one electrocardiographic (ECG) -time reference signal- and two waveforms of resistance changes (WR) have been recorded simultaneously during normal perfusion of a myocardium and during its ischemia. One resistance waveform has been recorded in the area of restricted blood flow while another one in the area of normal blood flow. Similar, two EGs have been recorded in each of the regions. In the myocardium area of a restricted blood flow the mean resistance increase and depolarization wave velocity decrease have been observed during the progress of ischemia. The results of experiments support the argument that both types of measurements are sensitive to the level of the myocardium ischemia. Such simultaneous measurements enable precise monitoring of the state of myocardium during CABG (Coronary Artery By-Pass Grafting). We conclude from our experiments that EG is a very sensitive to ischemic process. Moreover such recordings are less sensitive to artifacts than changes of tissue impedance WR. Simultaneous recording of EG and WR waveforms enables to calculate some additional parameters, e.g. relation of the value of resistance at a certain moment of the depolarization wave. Discussed measurements are possible without introducing any obstacles for a surgeon, as only modifications to existed construction of the stabilizer should be introduced. © Springer-Verlag 2007.