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Effects of heterogeneous myocardial perfusion on coronary venous H2 desaturation curves and calculations of coronary flow

Francis J. Klocke, Robert C. Koberstein, David E. Pittman, Ivan L. Bunnell, David G. Greene, and Douglas R. Rosing

1Department of Medicine, State University of New York at Buffalo School of Medicine, Buffalo, New York 14214

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Abstract

The present investigation was intended to evaluate myocardial inert gas desaturation curves for manifestations of heterogeneous coronary perfusion. The test gas was hydrogen (H2) and blood H2 analyses were performed with a gas chromatograph capable of detecting small but prolonged venous-arterial H2 differences produced by areas of reduced flow. Curves were initially obtained after 4-min left ventricular infusions of H2-saturated saline in six patients with arteriographically proven coronary artery disease, three patients with normal coronary arteries, and nine closed-chest dogs. The dogs were studied before and after embolic occlusion of a portion of the left coronary artery. Although the slopes of their semilogarithmically plotted venous desaturation curves varied with time before embolization, they showed more distinct deviations from single exponentials after embolization (after H2 concentrations had fallen below 15% of their initial values). The human curves divided similarly, those from coronary artery patients deviating appreciably from single exponentials. A similar separation was also evident in studies of coronary venous-arterial H2 differences after 20 min of breathing 2% H2: data were obtained in four dogs before and after coronary embolization, and in three normal patients, and five patients with coronary artery disease. Additional data indicated that the findings were not the result of right atrial admixture in sampled coronary venous blood, although admixture occurred frequently when blood was sampled in the first 2 cm of the coronary sinus (as seen in the frontal projection). Finally, average coronary flows calculated from a given set of data varied significantly with different methods of calculation. Areas of below-average flow seemed likely to be overlooked when single rate constants of desaturation, relatively insensitive analytical techniques, or relatively short periods of saturation and (or) desaturation are employed.

Circulation Research. 1968;22:841.)

© 1968 American Heart Association, Inc.

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Indicator-Dilution Measurement of Cardiac Output with Dissolved Hydrogen

FRANCIS J. KLOCKE M.D.1, DAVID G. GREENE M.D.1, ROBERT C. KOBERSTEIN M.D.1

1 Department of Medicine, State University of New York at Buffalo School of Medicine, Buffalo, New York 14214

Dissolved H2 has been used as an indicator for measuring cardiac output by the techniques of constant-rate injection and sudden, single injection indicator dilution. Because of its low solubility, H2 is eliminated essentially quantitatively in the lungs and recirculates negligibly. The constant-rate injection technique involves the gas chromatographic measurement of pulmonary (or systemic) arterial H2 concentration during an infusion of dissolved H2 into a vena cava (or the left atrium). Measurements in anesthetized dogs agreed well with simultaneous measurements by dye dilution, direct Fick, and direct volumetric techniques. Measurements could be repeated several times a minute, and using a linearly responding platinum electrode, intravascular H2 concentrations could be recorded continuously. In the sudden, single injection technique, dissolved H2 was injected into a vena cava (or the left atrium) while monitoring pulmonary (or systemic) arterial H2 concentration with a chromatographically calibrated platinum electrode. Measurements again agreed with simultaneous measurements by dye dilution, constant-rate injection of H2, and the direct volumetric technique. Hydrogen curves could be repeated rapidly and integrated instantaneously. Hydrogen appears to be a useful indicator for rapidly repeated determinations of cardiac output and for measurements of output in situations in which recirculation of conventional indicators limits their usefulness.

Key Words: indicator recirculation • gas chromatography • intrapulmonary H2 elimination • rapidly repeated cardiac outputs • H2 electrode • dogs

Accepted on April 15, 1968

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