Aortic Wall Stress in Hypertension and Ascending Thoracic Aortic Aneurysms: Implications for Antihypertensive Therapy
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ORIGINAL ARTICLE
Aortic Wall Stress in Hypertension and Ascending Thoracic Aortic Aneurysms: Implications for Antihypertensive Therapy Simon W. Rabkin • Michael T. Janusz
Received: 12 July 2013 / Accepted: 24 September 2013 / Published online: 5 October 2013 Ó Springer International Publishing Switzerland 2013
Abstract The objective of this study was the evaluation of aortic wall stress in patients with ascending thoracic aortic aneurysms (TAA) because of the paucity of data to guide medical therapy for blood pressure (BP) management in TAA. Twelve men, age 67.4 ± 3.3 years (SEM) with hypertension and ascending TAA without other etiology, previous aortic surgery or associated significant aortic valve disease, had maximum dimensions of the ascending aorta measured from CT angiogram (CTa) and transthoracic echocardiogram (TTE) with aortic wall thickness measured on TTE. Wall stress (WS(r)(P)) at peak systolic BP (SBP) was expressed by the equation: WS(r)(P) = 2LCSA 9 SBP/MCSA, where LCSA is ascending aorta luminal cross-sectional area; MCSA is the surface area of the aortic wall cross sectional area considering aortic wall thickness. There was no significant difference in wall stress from TTE or CTa although mean wall stress was slightly larger when calculated from CTa. For each 5 mmHg increment in Systolic BP (SBP), there was a 3.9 kPa increase in wall stress that was 3.5 kPa for small aneurysms (40 to \45 mm) and 4.4 kPa for larger aneurysms (45–52 mm). There was a 33.0 ± 1.2 % reduction in wall stress when SBP went from 165 to 110 mmHg with a 21.0 ± 0.7 % reduction in wall stress found when SBP was reduced from 140 to 110 mmHg. These data, in patients with hypertension and ascending S. W. Rabkin (&) Department of Medicine, Division of Cardiology, University of British Columbia, Level 9 2775 Laurel St, Vancouver, BC V5Z 1M9, Canada e-mail: [email protected] M. T. Janusz Department of Surgery, Division of Cardiovascular Surgery, University of British Columbia, Vancouver, BC, Canada
TAA suggest that meaningful reductions in aortic wall stress occur with reductions of SBP and this benefit extends to SBP levels \140 mmHg. Keywords Aortic wall stress Hypertension Thoracic ascending aortic aneurysms
1 Introduction The increasing incidence of thoracic aortic aneurysm (TAA), a condition with a potentially high mortality rate from sudden rupture of the aorta [1, 2], has focused attention on the medical management of TAA prior to surgical intervention [3]. TAA is due to a spectrum of genetic, degenerative and traumatic conditions [3, 4]. Hypertension is not only a major risk factor for the development of cardiovascular disease [5] but also is a likely factor leading to the development of TAA, that is not of genetic or traumatic origin [4, 6]. Patients with TAA have a high prevalence of hypertension [4, 6] and hypertension is a predictor of development of aortic dissection in TAA [7]. In addition, hypertension is a significant factor influencing survival in patients with TAA as the survival rate in TAA with hypertensi
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