028 Aortic wall stress in patients with hypertension and ascending aortic aneurysms

Abstract

The relationship of blood pressure to ascending aortic aneurysm has not been well characterized in patients with hypertension. Patients attending an aortic diseases clinic who met the following criteria: ascending aortic aneurysm of unknown etiology - no evidence of Marfan's syndrome or genetic disease known to be associated with aortic aneurysm who had hypertension, had no previous surgery on the ascending aorta and who did not have significant aortic valve disease (no significant aortic stenosis or regurgitation. More detailed aortic dimensions were obtained from the M Mode of the aorta and included aortic systolic diameter, aortic diastolic diameter and aortic wall thickness in systole and diastole. Wall stress (WS) was measured at peak systole. WS at a blood pressure P is expressed from the equation: WS(P) = 2LCSA × Psyst/MCSA, where LCSA is the lumen cross-sectional area and assumed that the ascending aorta was circular; MCSA is the surface area of the aortic wall cross sectional area and considered aortic wall thickness. Within a 6 month period, nine men age 69.9+10.2 years (SD) fulfilled these criteria and had an echocardiographic assessment of their heart and ascending aorta. Aortic diameter was 44.1+2.9 mm at level of sinus of Valsalva and 46.3+5.5 mm at the level of the ascending aorta from echocardiogram were evaluated. Using the model, wall stress was calculated for systolic blood pressures from 110 to 170 mmHg for each patient and averaged. For each 5mmHg increment in systolic blood pressure there was an approximately 4% increase in wall stress. The relationship was more strongly evident at lower levels of systolic blood pressure. Wall stress continued to increase with increasing systolic blood pressure but incrementally less. These data in patients with hypertension and aneurysms of the ascending thoracic aorta, give credence to the suggestion that there is a benefits of reduction of systolic blood pressure to levels less than 140 mmHg.