Attenuated myocardial vasodilator response in patients with hypertensive hypertrophy revealed by oxygenation-dependent magnetic resonance imaging

Background - Oxygen (O₂) homeostasis is central to myocardial tissue functioning, and increased O₂ demand is thought to be satisfied by a vasodilatory mechanism that results in increased blood and O₂ delivery. We applied blood oxygenation level-dependent (BOLD) MRI in conjunction with vasodilatory stress to index the ability to augment intramyocardial oxygenation in hypertensive hypertrophy, the primary cause of heart failure. Methods and Results - Nine healthy controls and 10 hypertensive subjects with moderate-to-severe hypertrophy underwent imaging on a 1.5 T clinical scanner. The dipyridamole-induced change in the apparent transverse relaxation rate, R2*, which correlates with hemoglobin oxygenation, was -5.4±2.2 s^-1 (95% CI, -4.0 to -6.8 s^-1) in controls compared with -1.7±1.4 s^-1 (95% CI, -0.8 to -2.6 s^-1) in hypertensive patients (P=0.0003). Conclusions - Patients with hypertensive hypertrophy demonstrate an impaired ability to increase intramyocardial oxygenation during vasodilatory stress, as indexed by BOLD MRI. The capacity to image vascular function with BOLD MRI may advance the understanding of the development of ventricular dysfunction in hypertension.