Precordial ST-segment mapping 1. Clinical studies in the coronary care unit.

Abstract

SUMMARYPrecordial ST-segment mapping was applied serially in the coronary care unit for the study of 46 patients with myocardial infarction (MI), using a 49-lead system. Data from the maps were compared with clinical status of patients, conventional ECGs obtained simultaneously, and serum enzyme levels. Stability of the maps over a one hour period was noted in the early phase of admission. However, a The present study reports on the results of serial precordial mapping applied in patients treated in the CCU and discusses the advantages of this modality over the conventional ECG. Material and MethodsForty-six patients (33 males and 13 females) age 55.3 ± 1.7 (SEM, range 31 to 79) years who were admitted to the CCU of Boston City Hospital with the presumptive clinical diagnosis of MI were studied. All patients had ST elevation in their 12-lead ECG and chest pain of over one hour's duration within the 24 hours before admission,1 except for one patient who was studied 48 hours after onset of pain. Excluded were patients with left and right bundle branch block (LBBB, RBBB), and patients who had a pacemaker implanted. All ECGs were recorded using a Hewlett-Packard 1511A electrocardiograph. A Welsh selfretaining ECG electrode (HP Part No. 9301-0122) with a contact diameter of 15 mm, attached to the "V" lead was used for precordial mapping. Studies were not done during an episode of chest pain, save for the initial ones on admission. Paper speed was 25 mm/sec and the standardization was 0.1 mV/mm. Patients were studied in the supine position following marking of a grid on the anterior chest wall, consisting of 49 recording sites, arranged in seven horizontal rows, each including seven marks ( fig. 1). The seven horizontal rows were designated by letters A to G and the vertical columns by numbers 1 to 7. The top right mark (Al) was made at the second intercostal space to the right of the sternum, A2 was made at the second intercostal space to the left of the sternum. A6 was placed at the same horizontal level on the anterior axillary line, A, and A4 marks were spaced evenly between A2 and A,, and A,, and A7 were made at the same horizontal level on the mid-and posterior ax-

Localization of regional myocardial ischemia by recording of monophasic action potentials.

“…In contrast, epicardial ST segment voltages were highest just inside the cyanotic border and decreased progressively toward the center of the ischemic region. As seen in figure 6, these increases in total ST segment voltage were due to a combination of true ST elevation and TQ segment depression. The relative contribution of TQ segment depression, however, was greater in recordings made inside the ischemic region der of the cyanotic region was determined in six dogs by the radioactive microsphere technique.…”

ST-segment variations after acute myocardial infarction. Relationship to clinical status.

“…Reese and co-authors found wide variability in 2ST after AMI, and noted that re-elevations were not always associated with infarct extension. '3 Madias et al,6 who studied 37 patients with AMI, found evidence for infarct extension in 18. One patient with subendocardial ischemia had a progressive increase in ST depression, evolved an anterior transmural MI and died in cardiogenic shock.…”

ST-segment mapping. Realistic and unrealistic expectations.

“…Precordial ST-segment mapping provides a useful noninvasive approach for the assessment of acute directional changes in ischemic injury that appears to be a reliable clinical indicator of particular therapeutic interventions.14 29,[32][33][34][35][36][37][38][39] More rapid reductions of ST-segment elevations were observed in patients with the inhalation of oxygen39 and the use of drugs such as hyaluronidase,33 nitroglycerin (with and without phenylephrine37, 38), as well as with intra-aortic balloon counterpulsation,29 than in untreated patients. The same interventions have been shown to reduce infarct size in experimental animals, and these changes in the ST segment appear to correlate well with the salvage of myocardium.…”