Sympathetic Nerve Activity following Acute Type B Aortic Dissection: A Pilot Study

Control of blood pressure following acute type B aortic dissection usually requires sympatholytic antihypertensive medication. Although sympathetic nerve activity is central to blood pressure control, its role in the hypertensive response to acute aortic dissection has not been assessed.

A prospective pilot study was performed over an 18-month period. Patients presenting with acute type B aortic dissection confirmed on computed tomographic angiography were recruited. We measured blood pressure, heart rate, muscle sympathetic nerve activity (MSNA), and plasma catecholamine levels in patients following acute type B dissection and controls. Comparisons between groups were made 1 week (acute phase) and 3 months after dissection (recovery phase).

Five patients and four controls were recruited in the study. MSNA was higher in patients than controls during the acute phase of aortic dissection: 62 (60-62) versus 46 (29-60) bursts/min (effect size 0.88) and 88 (54-96) versus 71 (44-101) bursts/100 beats (effect size 0.60). Plasma normetanephrines were also increased acutely: 821.0 (489.0-884.0) versus 417.0 (348.5-561.5) pmol/L (effect size 0.85).

Sympathetic nerve activity is increased acutely during the first week after type B aortic dissection, resolving towards control values after 3 months. Immediate sympatholytic drug treatment is likely to be crucial in order to prevent the acute and chronic complications of this response. This may confer benefits over and above simply lowering the blood pressure to protect the aorta in the acute phase.