Changes in aortic distensibility and pulse wave velocity assessed with magnetic resonance imaging following beta-blocker therapy in the marfan syndrome

Abstract

It has been shown that β-adrenergic blocking agents may reduce the rate of aortic root dilation and the development of aortic complications in patients with the Marfan syndrome. This may be due to β–blocker-induced changes in aortic stiffness, of which distensibility and pulse wave velocity are in vivo measurable derivatives. We studied changes in distensibility at 4 levels of the aorta and pulse wave velocity along the entire aorta after 2 weeks of β-blocker therapy in 6 Marfan syndrome patients and in 6 healthy volunteers, using magnetic resonance imaging (MRI) combined with brachial artery blood pressure measurements. In both groups, mean blood pressure decreased significantly (Marfan: 86 ± 6 vs 78 ± 5 mm Hg, p <0.05; control: 80 ± 8 vs 73 ± 3 mm Hg, p <0.05) (all data expressed as mean ± 1 SD). At baseline, the Marfan syndrome patients exhibited decreased distensibility at the level of the ascending aorta (2 ± 1 vs 6 ± 2 10 −3mm Hg −1, p <0.01) and increased pulse wave velocity (6.2 ± 0.4 vs 3.9 ± 0.4 ms −1, p <0.01) compared with control subjects. Only the Marfan syndrome patients had a significant increase in aortic distensibility at multiple levels and a significant decrease in pulse wave velocity after β-blocker therapy (ascending aorta distensibility: 2 ± 1 vs 4 ± 1 10 −3mm Hg −1, p <0.05; abdominal aorta distensibility: 5 ± 2 vs 8 ± 3 10 −3mm Hg −1, p <0.05; pulse wave velocity: 6.2 ± 0.4 vs 5.0 ± 1.0 ms −1, p <0.05). Thus, aortic stiffness in Marfan syndrome, together with mean blood pressure, is reduced by β-blocker therapy, and MRI is well suited to detect these changes by measuring distensibility and pulse wave velocity.