Nuclear magnetic resonance spectroscopy of rat ventricles following chronic hypoxia: A model of right ventricular hypertrophy

Nuclear magnetic resonance spectroscopy was used to study the effect of chronic hypoxia on both right (RV) and left ventricular and septal (LV + S) muscle. Rats in the hypoxic group, kept in a hypobaric chamber at $\text{1}\text{2}$ atm pressure for 2 weeks, developed right, but not left, ventricular hypertrophy (p < 0.001). Tissues were studied within 2.5 h of return to air. T₁ and T₂ relaxation times of RV, LV + S and thigh muscle (Th) from hypoxic and control rats were compared. The T₂ value distinguished hypoxic from control RV (p < 0.002), but not hypoxic from control LV + S or Th, indicating that the change in relaxation time reflects cellular hypertrophy, and not hypoxemia. For hypoxic rats only the T₂ value distinguished each muscle type: RV from LV + S (p < 0.009), RV from Th (p < 0.001) and LV + S from Th (p < 0001). The T₁ value did not identify either the hypoxic or control group or the type of muscle. Percent water content was similar for all tissues. For hypoxic RV, T₂ correlated with the percent water content (r = 0.89; p < 0.01). The sensitivity of T₂ to the cellular changes associated with hypoxic RV hypertrophy could provide a means of detecting right ventricular hypertrophy.