Assessment of myocardial viability by intracellular 23Na magnetic resonance imaging.
BACKGROUND
Because of rapid changes in myocardial intracellular Na+ (Na+(i)) during ischemia and reperfusion (R), 23Na magnetic resonance imaging (MRI) appears to be an ideal diagnostic modality for early detection of myocardial ischemia and viability. So far, cardiac 23Na MRI data are limited and mostly concerned with imaging of total Na+. For proper interpretation, imaging of both Na+(i) and extracellular Na+ is essential. In this study, we tested whether Na+(i) imaging can be used to assess viability after low-flow (LF) ischemia.


RESULTS
Isolated rat hearts were subjected to LF (1%, 2%, or 3% of control coronary flow) and R. A shift reagent was used to separate Na+(i) and extracellular Na+ resonances. Acquisition-weighted 23Na chemical shift imaging (CSI) was alternated with 23Na MR spectroscopy. Already during control perfusion, Na+(i) could be clearly seen on the images. Na+(i) image intensity increased with increasing severity of ischemia. During R, Na+(i) image intensity remained highest in 1% LF hearts. Not only did we find very good correlations between Na+(i) image intensity at end-R and end-diastolic pressure (R=0.85, P<0.001) and recovery of the rate-pressure product (R=-0.88, P<0.001) at end-R, but most interestingly, also Na+(i) image intensity at end-LF was well correlated with end-diastolic pressure (R=0.78, P<0.01) and with recovery of the rate-pressure product (R=-0.81, P<0.01) at end-R. Furthermore, Na+(i) image intensity at end-LF was well correlated with creatine kinase release during R (R=0.79, P<0.05) as well as with infarct size (R=0.77, P<0.05).


CONCLUSIONS
These data indicate that 23Na CSI is a promising tool for the assessment of myocardial viability.
Jansen
Maurits A
MA
University Medical Center, Heart Lung Center Utrecht, NMR Laboratory, Utrecht, The Netherlands.
Van Emous
Jan G
JG
Nederhoff
Marcel G J
MG
Van Echteld
Cees J A
CJ
D000818:Animals; D002470:Cell Survival; D008297:Male; D017202:Myocardial Ischemia / Q000473:pathology*; D009206:Myocardium / Q000737:chemistry / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000473:pathology; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000201:enzymology; D012964:Sodium / Q000032:analysis*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase