European Journal of Cardio-Thoracic Surgery, Vol 12, 63-69, Copyright © 1997 by European Association for Cardio-thoracic Surgery
Left ventricular remodelling and improvement in Freestyle stentless valve haemodynamics
XY Jin, S Westaby, DG Gibson, R Pillai and DP Taggart
Department of Cardiac Surgery, Oxford Heart Centre, John Radcliffe Hospital, UK.
OBJECTIVE: To assess how left ventricular (LV) hypertrophy, geometry and
function change after stentless aortic valve replacement for aortic
stenosis, and to elucidate the physiological mechanism of the improvement
in stentless valve haemodynamics. METHODS: 81 patients with aortic stenosis
(age 75 +/- 6 years, 47 male) underwent aortic valve replacement (plus CABG
in 33 patients) with a Freestyle stentless porcine valve (mean size 23 +/-
2 mm). They were prospectively investigated by Doppler echocardiography at
2 weeks, 3-6, 12, and 24 months after operation. Two hundred and forty-six
echocardiograms were obtained and analysed. Aortic valve performance was
assessed from its effective orifice area (EOA), the transvalvular increase
in mean flow velocity (delta mV), the deceleration time of aortic flow
velocity, and mean pressure drop (mPG). LV hypertrophy was assessed from LV
mass index; LV geometry, from the ratio of wall thickness to the radius
(T/R ratio) and LV function, from stroke volume index (LVSVI) and
myocardial stroke work (SW). RESULTS: By 2 years after operation, LV mass
index had fallen from 162 +/- 64 to 109 +/- 36, g/m2, and T/R ratio from
0.61 +/- 0.25 to 0.43 +/- 0.10. LVSVI increased from 29.4 +/- 10 to 42 +/-
17, ml/m2, and myocardial SW from 3.1 +/- 1.6 to 5.2 +/- 2.2, mJ/cm3 (all P
< 0.001 by ANOVA), while LV outflow tract diameter remained unchanged.
At the same time, stentless valve EOA increased from 1.59 +/- 0.75 to 2.2
+/- 0.72, cm2, and delta mV (from 82 +/- 31 to 49 +/- 24, cm/s) and mPG
(from 9.7 +/- 5.0 to 5.2 +/- 3.7 mmHg) both fell significantly (all P <
0.001 by ANOVA): as the deceleration time of aortic flow velocity increased
from 153.6 +/- 64.1 to 202.7 +/- 37.6 ms (P < 0.001 by ANOVA).
CONCLUSION: After stentless aortic valve replacement, LV mass index and
wall thickness both fall towards normal, and myocardial stroke work
increases. These ventricular remodelling processes are accompanied by a
more physiological flow jet at valve cusp level, which permits a greater
stroke volume to be ejected with a smaller transvavular velocity increase,
so that effective orifice area increases.
