Resonance Raman Spectroscopy Detects Ischemia in Experimental Coarctation of the Aorta in a Rodent Model

Coarctation of the aorta (CoA) can cause aortic obstruction, ischemia, and death. Resonance Raman Spectroscopy (RRS) measures tissue oxyhemoglobin (ShbO₂) and mitochondrial redox state (3RMR) non-invasively. Metal wire was placed around the aorta of Sprague Dawley rats to generate a systolic blood pressure (SBP) gradient. RRS-ShbO₂ and 3RMR were measured pre- (hand) and post-obstruction (foot). In model 1 (n = 8), the gradient rapidly reached 120 mmHg. In model 2 (n = 30), gradients of 20 mmHg (n = 9) and 40 mmHg (n = 12) were maintained for 2 h. In model 1, foot-ShbO₂ and 3RMR changed significantly (P = 0.004 and P = 0.007) at SBP gradients of 80-mmHg or above. In model 2, the 40-mmHg gradient group showed significant declines in foot-ShbO2 (P = 0.014) and increases in 3RMR (P = 0.008) by 1 h. Foot-ShbO₂ and 3RMR correlated strongly with serum mixed venous saturation (ShbO₂: r = 0.73, P < 0.0001; 3RMR: r = -0.55, P < 0.0001). RRS effectively detects ischemia caused by aortic obstruction in a CoA model.