Objectives: The impairment of right
ventricular (RV) myocardial mechanics is evident in hypertrophic cardiomyopathy
(HCM). It is independently influenced by LV mechanics and correlated to the
severity of LV phenotype. We investigated the changes in RV global and regional
deformation following surgical septal myectomy
using vector velocity imaging (VVI). Methods: 25 HCM patients, 68% males with mean
age (34.5 ± 12 years) were examined before and within two months after surgical
myectomy using VVI. In addition to conventional
echocardiographic parameters, peak systolic strain (εsys), strain rate (SR) and time to peak εsys (TTP) of regional RV
free wall (RVFW) & septal walls were analyzed in longitudinal (long)
directions from apical four-chamber view and their (Δ) changes were calculated.
Similar parameters were quantified in LV from apical 2 & 4 CH views.
Intra-V-delay was defined as SD of TTP and inter-V dyssynchrony was estimated
from TTP difference between the most delayed LV segment & RVFW. Results: All study patients showed improvement of their functional class from NYHA class
III to class I and reduction of LVOT gradient to below 20 mmHg except one
patient who had 30 mmHg gradients at rest. There was significant reduction of septal thickness, left atrial diameter & volume, LVOT
gradient, LVMI, severity of mitral
regurgitation, tricuspid annular velocities (P < 0.0001), RV diameter (P
< 0.02) and increase in LV internal dimensions(P < 0.001) post myectomy. However, there was significant
reduction of RV and LV systolic mechanics; RV global εsys % (from -16.1% ± 4.4%
to -12.9% ± 2.9%, P < 0.0001)
and LV global εsys %: from
-11.6% ± 2.8% to -9.4% ± 2.2%, P < 0.0001) respectively. The
magnitude of reduction of RV strain (ΔRV εsys %, ΔSRsys) was directly correlated LV maximal wall thickness (r = 0.46, P < 0.01)
and ΔRV dyssynchrony (TTP-SD) (r = 0.4, P < 0.05) and negatively correlated to
age (r = -0.46, P < 0.02), pre-op RV SRsys (r = -0.52, P < 0.01) and
pre-op LV EF % (r = -0.43, P
< 0.03). Meanwhile, the reduction in RV diastolic mechanics: ΔRV SRe & SRa were directly correlated to PAP and LVOT gradient
before surgery (r = 0.62, P < 0.002). Conclusion: Despite the improvement of patient functional
status and reduction LVOT gradient, RV mechanics shows further deterioration
after surgical myectomy. The magnitude of
reduction is modestly related to cardiac phenotype and pre-op mechanical
function.