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DOI: 10.1148/radiol.2481071027
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(Radiology 2008;248:88-96.)
© RSNA, 2008

Cardiac Imaging

Tissue Sodium Concentration in Myocardial Infarction in Humans: A Quantitative 23Na MR Imaging Study1

Ronald Ouwerkerk, PhD, Paul A. Bottomley, PhD, Meiyappan Solaiyappan, PhD, Amy E. Spooner, MD, Gordon F. Tomaselli, MD, Katherine C. Wu, MD, and Robert G. Weiss, MD

1 From the Division of Magnetic Resonance Research, Department of Radiology (R.O., P.A.B., M.S.); and Cardiology Division, Department of Medicine (A.E.S., G.F.T., K.C.W., R.G.W.), Johns Hopkins University, School of Medicine, 601 N Caroline St, JHOC 4241, Baltimore, MD 21287-0845. Received June 25, 2007; revision requested August 23; revision received October 29; accepted January 15, 2008; final version accepted February 19. Supported by a grant from the Donald W. Reynolds Foundation and by National Institutes of Health grant 1R01-HL61695. Address correspondence to R.O. (e-mail: rouwerke@mri.jhu.edu).

Purpose: To prospectively determine whether the absolute tissue sodium concentration (TSC) increases in myocardial infarctions (MIs) in humans and whether TSC is related to infarct size, infarct age, ventricular dysfunction, and/or electrophysiologic inducibility of ventricular arrhythmias.

Materials and Methods: Delayed contrast material–enhanced 1.5-T hydrogen 1 (1H) magnetic resonance (MR) imaging was used to measure the size and location of nonacute MIs in 20 patients (18 men, two women; mean age, 63 years ± 9 [standard deviation]; age range, 48–82 years) examined at least 90 days after MI. End-systolic and end-diastolic volumes, ejection fraction, and left ventricle (LV) mass were measured with cine MR imaging. The TSC in normal, infarcted, and adjacent myocardial tissue was measured on sodium 23 (23Na) MR images coregistered with delayed contrast-enhanced 1H MR images. Programmed electric stimulation to induce monomorphic ventricular tachycardia (MVT) was used to assess arrhythmic potential, and myocardial TSC was compared between the inducible MVT and noninducible MVT patient groups.

Results: The mean TSC for MIs (59 µmol/g wet weight ± 10) was 30% higher than that for noninfarcted (remote) LV regions (45 µmol/g wet weight ± 5, P < .001) and that for healthy control subjects, and TSC did not correlate with infarct age or functional and morphologic indices. The mean TSC for tissue adjacent to the MI (50 µmol/g wet weight ± 6) was intermediate between that for the MI and that for remote regions. The elevated TSC measured in the MI at 23Na MR imaging lacked sufficient contrast and spatial resolution for routine visualization of MI. Cardiac TSC did not enable differentiation between patients in whom MVT was inducible and those in whom it was not.

Conclusion: Absolute TSC is measurable with 23Na MR imaging and is significantly elevated in human MI; however, TSC increase is not related to infarct age, infarct size, or global ventricular function. In regions adjacent to the MI, TSC is slightly increased but not to levels in the MI.

© RSNA, 2008