Therapy and Prevention Angioplasty

To enhance detection of ischemia during percutaneous transluminal coronary angioplasty (PICA), unipolar intracoronary electrocardiograms (ECGs) were recorded during PTCA in 25 patients from the tips of guidewires positioned distal to stenoses being dilated. Surface electrocardiographic leads chosen to reflect likely areas of reversible ischemia during PTCA were recorded simultaneously. In 21 of 29 stenoses dilated (72%), ST segment elevation and/or T wave peaking in intracoronary ECG appeared during balloon inflation and disappeared after deflation, accompanied by transient angina on 19 occasions. Two patients had transient ST segment elevation in intracoronary ECGs during PTCA without associated angina. ST changes in the surface ECG during PTCA were seen on only nine occasions (31 %), always accompanied by ST segment elevation in the intracoronary ECG that appeared earlier and was of much greater magnitude. Five patients with prior myocardial infarction and aneurysm formation had fixed ST segment elevation in the intracoronary ECG unrelated to balloon inflation. Myocardial ischemia during PTCA can be detected easily with intracoronary ECGs and with greater sensitivity than that of the surface ECG. Furthermore, intracoronary ECGs may help to clarify the nature of chest pain during balloon inflation or during suspected complications. Circulation 74, No. 2, 330-339, 1986. MYOCARDIAL ISCHEMIA is frequently provoked during percutaneous transluminal coronary angioplasty (PTCA). In most cases ischemia is only transient, appearing after advancement of the angioplasty catheter across a critical stenosis or during balloon inflation and disappearing promptly upon balloon deflation. Occasionally, when angioplasty results in occlusion of a vessel or intimal dissection that compromises antegrade blood flow, ischemia may be long lasting. Traditionally, the presence or absence of angina and the surface electrocardiogram (ECG) have been relied upon to monitor myocardial ischemia during PTCA. Such an approach is not entirely satisfactory. Patients may not experience angina, even though profound myocardial ischemia is present.' Alternatively, chest pain during PTCA may not be caused by ischemia.' The surface ECG is also an unreliable index of ischemia. Ischemia in some regions of the heart may not be reflected by ST segment or T wave changes in From the Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston. Address for correspondence: Peter L. Friedman, M.D., Ph.D., Cardiovascular Division, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115. Received Jan. 9, 1986; revision accepted May 1, 1986. the particular leads being monitored during PTCA or may be present in an area of myocardium too small to be reflected in any of the standard surface leads.3 Conversely, previous myocardial infarction with aneurysm formation may cause fixed ST segment and T wave abnormalities that can mimic or obscure changes caused by transient ischemia. Acute ischemia in myocardial cells leads to a decline in resting membrane potential and abbreviation of action potential duration.4 One result of these abnormalities is the generation of current flow between ischemic and nonischemic regions. It is this current flow that leads to deviation of the ST segment in the ECG.4 Of note, the magnitude of such "currents of injury" is influenced greatly by the distance from the recording electrode to the region of ischemia. Thus an electrode on the body surface distant from a region of ischemia would be expected to record less ST segment deviation than an electrode placed on the surface of the heart, near the ischemic area. In the present study, local unipolar intracoronary ECGs were recorded during PITCA directly from guidewires positioned across coronary stenoses to be dilated. By virtue of the proximity of the guidewires to regions of potential ischeCIRCULATION 330 by gest on A ril 0, 2017 http://ciajournals.org/ D ow nladed from THERAPY AND PREVENTION-ANGIOPLASTY mia, it was thought that intracoronary ECGs recorded in this fashion might prove to be more sensitive and reliable indicators of transient myocardial ischemia than the standard ECG recorded from the body surface.