Aorta Wall Stress during Exercise in Patients with an Ascending Thoracic Aortic Aneurysm: Insights from a Case Series.

Abstract

Individuals with ascending thoracic aortic aneurysm (ATAA) are recommended to avoid intense exercise for fear of marked increases in aortic wall stress (AWS). However, no study has measured AWS during exercise. The aim of this case series was to examine AWS during "light-to-moderate" aerobic exercise in individuals with ATAA and healthy control (CON) participants.Three clinically stable patients with ATAA (2 male, mean age: 74 ± 1 years) and 3 CON (2 male, mean age: 69 ± 7 years) were studied on 2 separate days. Day 1: a maximal cardiopulmonary exercise test was performed to measure peak aerobic power (VO₂peak), maximal heart rate, and blood pressure (BP). Day 2: cardiac and aortic magnetic resonance imaging were performed at rest and during submaximal (3-5 metabolic equivalents) "stepper" exercise during which cardiac output (Qc), aorta diameters, wall thickness, and BP were measured. Circumferential ascending and descending AWS were calculated in accord with LaPlace Law, whereas aorta mechanical efficiency was derived as the AWS/Qc slope.Patients with ATAA demonstrated lower median VO₂peak (18.2 vs. 24.1 mL/kg/min). During exercise, the absolute ascending (ATAA: 257 vs. CON: 269 kPa) and descending AWS increased (ATAA: 224 vs. CON: 207 kPa), and ∆AWS during exercise was similar between ATAA and CON (Ascending, ATAA: 79 vs. CON: 62 kPa; Descending, ATAA: 64 vs. CON: 55 kPa). During exercise, ascending and descending AWS were 76 to 83% below ATAA rupture thresholds (i.e., 800-1,200 kPa) in all patients. Finally, exercise Qc was 17% lower and the ascending AWS/Qc slope was 30% higher in ATAA (16 kPa/L/min) versus CON (12 kPa/L/min).Our findings demonstrate "light-to-moderate" aerobic exercise produces similar AWS responses between ATAA and CON and is well below aneurysmal rupture thresholds. The higher AWS/Qc slope in ATAA suggests decreased aortic mechanical efficiency and may be a useful measure for exercise prescription for these patients.