Abstract P423: Six Minutes Walk Test in Patients with Severe Aortic Stenosis: A Maximal Exercise Testing Procedure?
Rationale: Maximal exercise testing is an absolute contraindication in patients with severe symptomatic aortic stenosis (SSAS). Instead of maximal testing, the 6 minutes-walk test (6MWT) may be recommended to evaluate functional capacity and to establish prognostic. The aim of this study was to compare the 6MWT with a maximal exercise test in patients with SSAS.
Method: A ramp cardiopulmonary exercise test (CPET) on a cycle ergometer taken as control, and a 6MWT, both with a breath-by-breath gas analysis, were performed in a population with SSAS waiting for transcatheter aortic valve implantation (TAVI). During both tests, patients were monitored with continuous electrocardiogram. Blood pressure was taken every 2 minutes during CPET and at the beginning and the end of the 6MWT test. Patients underwent both tests.
Results: A total of 12 patients aged 79.5 ± 5.9 years participated to these evaluations. During the 6MWT, patients walked a mean distance of 335±74 m, producing a mean maximal workload of 48.5±13.2 watts during CPET. Through CPET, patients achieved a maximal oxygen consumption (VO2peak) of 11.9±4.2 mL/kg/min, which was similar to the VO2peak reached during 6MWT (12.8±2.5 mL/kg/min, p=0.062). For both tests, the respiratory exchanged ratio exceeded 1.1 (CPET=1.16±0.06 and 6MWT=1.12±0.09, p=0.241), which is one criterion of a maximal exercise capacity test. In comparison to CPET, a higher proportion of the 6MWT was performed at high intensity level (>85% VO2peak); 74.2±29.0% of the 6MWT vs. 31.5±24.0% of CPET, p=0.004*. During CPET, 8 patients experimented abnormal blood pressure (BP) response (4 dropped their BP and 4 achieved maximal BP value during recovery). No complication occurred during both tests except for 3 patients who experienced angina pectoris. In this high-risk elderly cohort, lean body mass was the better anthropometric feature associated with better exercise capacity during CPET (r=-0.73, p=0.03*).
Conclusion: Both exercise tests were very demanding for patients with SSAS waiting for TAVI. The 6MWT was a maximal effort and high intensity exertion was maintained for almost 75% of the test. The 6MWT was as intense as CPET suggesting the importance of an adequate monitoring while testing those patients. Considering that CPET allow blood pressure measure throughout the test and included a lower test portion in high intensity level, CPET may be more appropriate to evaluate functional capacity in patients with SSAS.
- © 2013 by American Heart Association, Inc.