Effects of ischemia on intracellular rubidium in pig and rat hearts:87Rb NMR imaging and spectroscopic study

Rubidium-87 magnetic resonance spectroscopy and imaging for analysis of mammalian K+ transport

“…39 A similar observation was made in pig hearts preloaded with Rb þ , in which the left anterior descending artery (LAD) was occluded for 120 min. 39 The peak heights of 87 Rb spectra from the ischemic anterior wall increased by 40 AE 16% (vs 21 AE 11% in non-ischemic area) due to a 12% decrease in the apparent 87 Rb linewidth and a 24 AE 14% increase in peak area. The 87 Rb peak could be fitted to two Lorentzians, with narrow (297 AE 21 Hz) and broad (1098 AE 40 Hz, 59 AE 3% of the total area) components.…”

“…In these studies, ischemia caused a 33 AE 4% increase in the 87 Rb resonance peak height as a result of peak narrowing (13 AE 1%), and an increase in peak area (17 AE 5%). 39 A similar observation was made in pig hearts preloaded with Rb þ , in which the left anterior descending artery (LAD) was occluded for 120 min. 39 The peak heights of 87 Rb spectra from the ischemic anterior wall increased by 40 AE 16% (vs 21 AE 11% in non-ischemic area) due to a 12% decrease in the apparent 87 Rb linewidth and a 24 AE 14% increase in peak area.…”

“…37 For this reason the 87 Rb resonance consists of two wide components centered at the same frequency: narrow (150 Hz in water) and broad lines comprise 40 and 60% of the total area, respectively. [37][38][39] In biological tissues Rb þ binding and the higher viscosity of the milieu result in shorter relaxation times and broader lines. The broader component may not be observed due to low SNR and truncation of free induction decay by receivers with a relatively long dead times.…”

“…39,50,53,56,[66][67][68][69][70] In our first 87 Rb imaging study 66 projection-reconstruction was used, which provided rather fuzzy images. In all our subsequent work a three-dimensional chemical shift imaging (CSI 3-D) sequence was used, 39,50,53,56,[66][67][68][69][70] which provided minimal delay between the excitation pulse and acquisition (0.5 ms on Bruker Avance console interfaced with a 7.05 T magnet). Even this short delay, necessary for gradient ramping, resulted in loss of two-thirds of the signal.…”

“…Complete (nominal zero flow) or partial ($10% of residual flow) LAD occlusion and subsequent reperfusion were used to induce ischemia and infarction in the anterior (Ant) left ventricular (LV) wall. 39,50,53,56,[66][67][68][69][70] The posterior (Pos) wall (normal, non-ischemic) served as an internal control/reference. Hearts were loaded with Rb þ either before or after LAD occlusion, or during reperfusion, and serial 87 Rb images were acquired.…”