Correlation of Intramyocardial Electrocardiograms with Polarographic Oxygen and Contractility in the Nonischemic and Regionally Ischemic Left Ventricle

Abstract

E HAVE previously shown that the enicardial-surface electrocardiogram is an inadequate index of localized myocardial ischemia. While striking chanares of polarographic oxygen and contractility regularly occur a few seconds after coronary arterial branch occlusion, epieardial electrocardiographic changes are delayed and sometimes absent.1 Intramyocardial electrocardiographic studies, on the other hand, reveal that localized ischemia disturbs myocardial electrical activity at least as early as either oxygenation or contractility, and over a more extensive area.We have developed a technique for amplification and recording of oxygen-reduction currents and electrocardiograms simultaneously from the same lead-point 2 "4 in the myocardium. This technique was combined with motion-picture records of muscle contraction 5 and epicardial-surface color. Thus, simultaneous information about electrical activity, oxygenation, and contractility in locally altered myocardium and adjacent, undisturbed muscle became available. This makes possible, as we will show in the present paper, an assessment of the limitations of Supported by Eesearch Grant H-398 from the National Heart Institute, National Institutes of Health, V. S. Public Health Service.Dr. Katcher is a Postdoctoral Eesearch Fellow, National Heart Institute (HF-7812 C3).Eeeeived for publication July 11, 1961. epieardial heart-body leads, which are still indispensable links between open-chest situations and the body-surface electrical phenomena of concern to the clinician. We consider such an assessment to be elementary for understanding the behavior of the heart muscle and the electrocardiogram in coronary heart disease.6 Methods In 28 dogs, weighing 15 to 23 Kg., the heart was exposed under morphine-Dial-urethane-pentobarbital anesthesia.7 A branch of the left anterior descending coronary artery was isolated. Eight to 10 glass-insulated platinum electrodes were inserted in the left ventricle as previously described. 1The construction of electrodes had been modified from those used in our earliest work. 7 The relatively heavy shank was eliminated and the entire shaft was made of light glass fused to a 0.2-mm. platinum wire which was connected at a plasticinsulated junction to a very light lead wire (no. 42 copper enameled) insulated by polyethylene tubing ( fig. 1). A white glass bead, cemented to the shaft at the level desired, acted as a depth stop and as a marker for cinematographic studies of muscle contraction. These electrodes were made the cathodes of an electrolytic circuit measuring changes in oxygen polarographically according to the method of Davies and Brink 8 and Montgomery and Horwitz. 9 The electrodes were also used as exploring lead-points for direct heart-body electrocardiograms. The platinum tips in the myocardium have an electrolytic capacitance of approximately 0.5 microfarad, which makes it possible to use them for simultaneous measurement of extracellular electrical activity. The reference electrode for both systems consisted of approximately two f...

Spatial and Nonspatial Influences on the TQ-ST Segment Deflection of Ischemia

“…This finding indicated that the spherical heart model with an ischemic region of uniform wall thickness from which the theoretical curves were derived (see Appendix) rather incompletely characterized the geom-206 R. P. Holland Boundary vs. local influences on the TQ-ST segment deflection. Recognizing that it is the relationship of the electrode to the ischemic boundary which determines the relative magnitude and polarity of the TQ-ST segment deflection, only then can it be appreciated that although sites of TQ-ST segment elevation are usually found to overlie tissue exhibiting lactate production (38), ATP and CPK depletion (29,38,39), histologic abnormalities (31,40), QRS complex alterations (5,30,41) and lowered PO2 (42)(43)(44), contractile activity (45), and coronary blood flow (46)(47)(48), the frequent lack of quantitative relationships existing between the magnitude of the TQ-ST segment deflection at a particular site and these alternated markers should not be surprising. Although the magnitude of the TQ-ST deflection varies depending upon the electrode's orientation to the boundary, there is no reason to expect CPK levels, histology, etc., to vary in the same manner.…”

Regional myocardial functional and electrophysiological alterations after brief coronary artery occlusion in conscious dogs.

“…This concept of rapid recovery is based primarily on studies in anesthetized animals with an open chest (3,4) or on pathological studies demonstrating no histologic evidence of cellular injury after occlusions of less than 18 min (2). Furthermore, it is clear that electrocardiographic evidence of ischemia is abolished rapidly after brief periods of coronary occlusion in anesthetized (1,5,6) and conscious animals (7), but that these indices of ischemia do not provide information on the time-course of recovery for mechanical function of the myocardium.…”

ST-segment mapping. Realistic and unrealistic expectations.

“…In some sites where mild ST-segment elevation of 1 to 2 mV had been present, CPK was normal in the subepicardial regions while subendocardial CPK depletion occurred 24 hours later. Thus, it is apparent from this observation, as well as the aforementioned correlations of the epicardial and intramyocardial ST segment with myocardial gas tensions, [22][23][24] that a limitation of the epicardial ST-segment measurement is its relative insensitivity to the more extensive subendocardial ischemic damage. A linear relation was found between local myocardial blood flow and log CPK activity 24 hours after coronary occlusion for both the subendocardial and subepicardial samples.…”