Exercise Limitation in Aortic Stenosis

McCann, Gerald Patrick (2001) Exercise Limitation in Aortic Stenosis. MD thesis, University of Glasgow.

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Symptomatic (Sy) aortic stenosis (AS) is a malignant condition with a five year survival of <50% but the prognosis in Asymptomatic (Asy) AS is relatively good. Aortic valve replacement (AVR) is virtually a curative procedure for those who survive the peri-operative period. AVR is recommended for symptomatic patients but the timing of surgery is critical to optimise outcome. Mechanisms underlying exercise intolerance and symptom generation in AS are poorly understood. This study investigated non-invasive predictors of exercise capacity in 37 patients with significant AS (peak PG >25mmHg) and 20 matched controls. Methods; Full echocardiography, cardiopulmonary exercise testing, skeletal muscle strength and endurance, arm and leg ergoreflex activation, brain natriuretic peptide (BNP) and endothelin-1 (ET-1) before and after maximal exercise, were measured. AS was classified by both disease (mild/severe) severity and symptomatic (Sy/Asy) status. Echocardiographic, anthropometric and exercise variables were examined as predictors of aerobic exercise capacity by univariate and multivariate regression analysis. Results: AS and control subjects were well matched for age, body size and sex. Sy patients (67.9+/-11, n=19) were older than Asy AS (47.6+/-19, n=18) and controls (50.4+/-17 years), p=0.001. Exercise capacity (% predicted) was reduced in Sy AS (52+/-27%) compared to Asy AS (86+/-28%) and controls (126+/-17%), p<0.0001. Exercise VEA/CO2 was increased in severe (34.5+/-8) and Sy AS (35.1+/-7) v mild (30.2+5), Asy AS (29.8+/-5) and controls (28.6+/-4) p<0.01. SBP response to exercise was reduced in severe and Sy AS v controls and Asy/mild AS (P<0.001). Isometric quadriceps strength (Sym 470+/-169N v Asy AS 564+/-251N V controls 567+/-199N) and isokinetic endurance (Sym 83.4+/-16% v Asy AS 71.9+/-14% V controls 76.1+/-7%) were not significantly different between AS and controls. Arm ergoreflex activation was not significantly increased in AS. Leg ergoreflex activation (ventilation, % peak) was enhanced in Sym AS (67+/-50) v Asy AS (20+/-46) and controls (17+/-48), p=0.01 but did not predict exercise capacity or VEA/CO2. BNP was increased in severe and Sym AS v mild/Asy AS and controls, p<0.0001. ET-1 was comparable at rest and after exercise in AS and controls. LV mass/mass index and BNP were independent predictors of exercise capacity in AS. Conclusions: Several variables have been identified which differ in symptomatic and asymptomatic AS. These (BNP, exercise capacity and SBP response ) should be assessed for prognostic value in a prospective study of AS.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: W Stewart Hills
Keywords: Medicine, Kinesiology
Date of Award: 2001
Depositing User: Enlighten Team
Unique ID: glathesis:2001-76035
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 17:05
Last Modified: 19 Nov 2019 17:05
URI: https://theses.gla.ac.uk/id/eprint/76035

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