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