Quantitative echocardiography
TDI as a quantitative tool is based on principles of lower velocity
Doppler frequency shifts and has been extensively used to characterize
both systolic and diastolic function. More specifically, mitral annular
early diastolic recoil velocity (e’) has been shown to be associated
with invasively measured time constant of LV relaxation (τ), and has
been validated in both animal models51 52 and human
studies.53-55 Further, e’ has been shown to be less
load-dependent than conventional doppler-derived parameters. With this
background, Ozdemir and colleagues first demonstrated reduced systolic
and diastolic myocardial velocities in MS subjects with normal ejection
fraction (EF). While systolic myocardial velocities demonstrated a
positive correlation with mitral orifice area, no association was
observed with e’, suggesting that reduced LV performance in MS could be
attributed to both myocardial and functional
factors.56 Sengupta and colleagues also demonstrated
decreased myocardial velocities in MS and subsequent elevation after
balloon commissurotomy. In that study, increase in e’ was associated
with MVA. Serial measurements during follow-up showed progressive
improvement in the annular velocities, prompting the authors to suggest
that tissue velocity imaging can be used to monitor changes in LV
function after PTMC.57
2D Speckle tracking echocardiography is another powerful parametric
imaging tool now being increasingly employed in clinical practice. There
is limited data studying diastolic function in MS employing speckle
tracking echocardiography. Sengupta and colleagues showed decreased
strain in patients with severe MS, with rapid improvement in LV
deformation after PTMC, which correlated well with improved diastolic
loading. The findings suggested that impaired LV mechanical function in
MS can be attributed to decreased LV filling, instead of structural
myocardial abnormalities.58
Balloon Mitral Commissurotomy
Percutaneous transvenous mitral commissurotomy (PTMC) is the treatment
of choice for patients with symptomatic MS. Soon after PTMC, an improved
LV filling and increased LV end diastolic volume is observed, with
slight increase in LVEDP and subsequent normalization.6
38 In the absence of LV diastolic dysfunction, no significant changes
are seen in LV diastolic pressure, although a fall in LA pressure is
observed. Limited data exists on the impact of PTMC on LV compliance and
the effect of elevated baseline LVEDP on outcomes. Eleid et al reported
LV diastolic dysfunction and elevated invasive LVEDP in one in three
subjects undergoing PTMC and suggested that diastolic aberrations
contribute to existing LA pressure and are associated with greater risk
of failure to improve symptoms. In their study, both body mass index and
DM were associated with diastolic dysfunction. While no significant
differences in severity of pulmonary hypertension or post-interventional
improvement in hemodynamic status was observed when comparing the group
with elevated LV stiffness (LVEDP>15mmHg) with normal
compliance (LVEDP≤15mmHg), the group with elevated LVEDP had a higher
risk of combined end-point, which included recurrent severe symptoms,
repeat procedure or death (1-year estimate, 42% vs 81%; hazard ratio,
2.83; 95% CI, 1.62-4.96; P<.001). 35Additionally, lower LVEDP has been proposed as an independent predictor
for intermediate and long-term risk-free survival in multiple
studies.59 60