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‘PCr overshoot’: a study of the duration in canine myocardium
Author(s) -
StraeterKnowlen Ingrid M.,
Butterworth Edward J.,
Buchthal Steven D.,
Hollander Jan A. den,
Caulfield James B.,
Jennings Robert B.,
Evanochko William T.
Publication year - 2002
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.757
Subject(s) - phosphocreatine , ischemia , medicine , chemistry , endocrinology , cardiology , nuclear magnetic resonance , energy metabolism , physics
The phosphocreatine (PCr) overshoot is a well‐documented phenomenon and is readily observable by 31 P MRS. In addition, a second 31 P MRS observation during ischemia with reperfusion is a diminution in ATP levels. Combining these two as the ‘PCr Overshoot’ the PCr/ATP ratio may provide an index of viability. However little information is available regarding the duration of this ‘overshoot’. For this approach to be useful clinically, the duration of this phenomenon must be ascertained. An open chest canine model of 12 min of ischemia followed by reperfusion (6 h) was used. A 2 cm surface coil was sutured to the myocardium and spectra were acquired at 4.7 T. Gated spectra were acquired in <2.5 min with an interpulse delay of 5 s. Integrals of the PCr and ATP (beta) resonances were analyzed using a line‐fitting routine. Overall, the PCr signal increased from 22.0 ± 0.8 to 25.5 ± 0.9 and ATP decreased from 11.7 ± 0.4 to 10.0 ± 0.4 (arbitrary units). The PCr remained elevated for the entire 6 h period and the percentage increase was 15.9%. The ATP remained depleted for the entire 6 h period and the percentage decrease was 17.0%. Thus, the clinically relevant and readily observable PCr/ATP is a product of both an increase in PCr and a decrease in ATP for a calculated net increase in PCr/ATP of 39.6%. The PCr/ATP ratio of the ischemia group for baseline, ischemia, 6 h reflow, were: 2.33 ± 0.18, 1.04 ± 0.29 and 3.22 ± 0.21. We demonstrate that the ‘PCr overshoot’ is readily observable and can be monitored noninvasively and nondestructively for 6 h. Therefore, the ‘PCr overshoot’ may be a viable marker of reversible injury in this model and may prove to be applicable for detecting myocardial viability in patients. Copyright © 2002 John Wiley & Sons, Ltd.