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CLINICAL STUDIES

¹³N-ammonia myocardial blood flow and uptake

Relation to functional outcome of asynergic regions after revascularization

^a Cardiology Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland, USA
^b Department of Nuclear Medicine, National Institutes of Health, Bethesda, Maryland, USA

Manuscript received December 23, 1997; revised manuscript received October 19, 1998, accepted November 20, 1998.

Reprint requests and correspondence: Dr. Vasken Dilsizian, Cardiology Branch, Building 10, Room 7B-15, National Institutes of Health, Bethesda, Maryland 20892-1650
dilsizian{at}nmdhst.cc.nih.gov

OBJECTIVES

In this study we determined whether ¹³N-ammonia uptake measured late after injection provides additional insight into myocardial viability beyond its value as a myocardial blood flow tracer.

BACKGROUND

Myocardial accumulation of ¹³N-ammonia is dependent on both regional blood flow and metabolic trapping.

METHODS

Twenty-six patients with chronic coronary artery disease and left ventricular dysfunction underwent prerevascularization ¹³N-ammonia and ¹⁸F-deoxyglucose (FDG) positron emission tomography, and thallium single-photon emission computed tomography. Pre- and postrevascularization wall-motion abnormalities were assessed using gated cardiac magnetic resonance imaging or gated radionuclide angiography.

RESULTS

Wall motion improved in 61 of 107 (57%) initially asynergic regions and remained abnormal in 46 after revascularization. Mean absolute myocardial blood flow was significantly higher in regions that improved compared to regions that did not improve after revascularization (0.63 ± 0.27 vs. 0.52 ± 0.25 ml/min/g, p < 0.04). Similarly, the magnitude of late ¹³N-ammonia uptake and FDG uptake was significantly higher in regions that improved (90 ± 20% and 94 ± 25%, respectively) compared to regions that did not improve after revascularization (67 ± 24% and 71 ± 25%, p < 0.001 for both, respectively). However, late ¹³N-ammonia uptake was a significantly better predictor of functional improvement after revascularization (area under the receiver operating characteristic [ROC] curve = 0.79) when compared to absolute blood flow (area under the ROC curve = 0.63, p < 0.05). In addition, there was a linear relationship between late ¹³N-ammonia uptake and FDG uptake (r = 0.68, p < 0.001) as well as thallium uptake (r = 0.76, p < 0.001) in all asynergic regions.

CONCLUSIONS

These data suggest that beyond its value as a perfusion tracer, late ¹³N-ammonia uptake provides useful information regarding functional recovery after revascularization. The parallel relationship among ¹³N-ammonia, FDG, and thallium uptake supports the concept that uptake of ¹³N-ammonia as measured from the late images may provide important insight regarding cell membrane integrity and myocardial viability.

Abbreviations and Acronyms   ATP = adenosine triphosphate   FDG = 18F-deoxyglucose   METs = metabolic equivalents   MRI = magnetic resonance imaging   PET = positron emission tomography   ROC = receiver operating characteristic   SD = standard deviation   SPECT = single-photon emission computed tomography

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