It has been suggested that isolated systolic hypertension (ISH) may result from a smaller proximal aortic diameter. However, the available data are conflicting, no doubt because of different techniques and sites of measurement. We compared maximum (systolic) diameter, minimum (diastolic) diameter, and aortic distensibility at various levels along the thoracic aortic arch, between normotensive subjects (NT) and those with ISH, using MRI.

48 healthy subjects aged≥60 years, free of cardiovascular disease and medication were recruited from the ACCT Study. A Fiesta sequence (1.5T scanner,GE) was then performed in all subjects at 6 aortic levels: the aortic root (L1),1cm above the aortic valve (L2), proximal to the innominate artery (L3), distal to the left subclavian artery (L4), the descending aorta (L5) and the level of the diaphragm (L6). Diameters were determined using ARTFUN software.

Subject were divided into those with a normal blood pressure (<140/90 mmHg) and those with ISH (systolic≥140 mmHg, diastolic <90 mmHg), and were matched for age. Average systolic and diastolic aortic diameters were greater in subjects with ISH (Table 1). Distensibility was greater in normotensive subjects compared to those with ISH at L2-L6 (L1: 0.64±2.72 vs. 0.21±1.53; L2: 5.69±2.72 vs. 2.60±1.33; L3: 3.10±1.97 vs. 1.27±0.99; L4: 3.86±1.81 vs. 1.69±0.70; L5: 3.91±2.58 vs. 1.68±0.63; L6: 5.18±2.43 vs. 2.73±1.69, units=10⁻³ × mmHg⁻¹, P<0.01 for L2-L6, P=0.5 for L1). With the exception of the aortic root, both systolic and diastolic proximal aortic diameters are greater in subjects with ISH compared to NT subjects, whereas distensibility is reduced.