076 Failure of aortic valve replacement to improve objective functional capacity in patients with isolated severe aortic stenosis

Abstract

Introduction Aortic stenosis (AS) is the commonest valve disease requiring surgery in the developed world. Development of symptoms is a Class 1 indication for aortic valve replacement (AVR) which reduces mortality. However, regression of left ventricular hypertrophy may be incomplete, myocardial fibrosis and diastolic dysfunction may be irreversible which may limit the functional improvement seen following AVR. We sought to examine the impact of AVR on cardiac remodelling and objective improvements in functional capacity. Methods 46 patients with isolated severe AS (peak velocity >4 m/s or mean pressure gradient (MPG) >Hg or aortic valve 40 mm area (AVA) <1 cm2) without obstructive coronary artery disease (on angiography) were recruited. Investigations were performed on the same day once listed for AVR and 6 months following surgery; transthoracic echocardiography (TTE) for stenosis severity, diastolic function; cardiac magnetic resonance (CMR) for ventricular geometry, left atrial volumes, myocardial fibrosis on late gadolinium enhancement (LGE), adenosine stress/rest perfusion for absolute quantification of myocardial blood flow and calculation of myocardial perfusion reserve (MPR); cardiopulmonary exercise testing (CPEX) for objective exercise capacity (peak VO2); venepuncture for NT-proBNP. Results 46 patients were studied pre-AVR. Baseline characteristics; mean age 66±9 years, 74% male, peak velocity 4.4±0.57 m/s, MPG Hg and AVA 0.86±0.22 cm 49±14 mm2. 43 patients returned for follow-up, of these 2 did not have CMR due to permanent pacemaker implantation and three had CMR without gadolinium (renal impairment/refused/extravasation). Non-normal data were log-transformed before analysis, paired t-tests were used for continuous variables, λ2/McNemar tests for categorical. 42/43 had a biological prosthesis. Comparison between pre- and post-operative values; Abstract 076 tables 1 and 2. There were significant improvements in symptomatic status and reductions in LVMI, LVEDVI and left atrial volume index (LAVI) but this was not associated with improvement in objective exercise capacity (or NT-proBNP), significant reduction in E/e' or increase in MPR. Discussion The majority of patients had minimal or no symptoms at the time of AVR. As expected there is a significant fall in LV mass and volumes by 6 months. The fall in left atrial volumes likely reflects the fall in left atrial pressure (and LVEDP consistent with a reduced, albeit not significantly, E/e'). Despite an improvement in NYHA Class there is no significant improvement in objective exercise capacity (peak VO2) at 6 months. Over half the patients have evidence of myocardial fibrosis (LGE) by the time of AVR, which does not regress post-operatively. Equally there is a failure of myocardial perfusion reserve to improve. This suggests that although significant LV remodelling occurs it is likely that irreversible fibrosis limits improvement in functional capacity.