Abstract and Introduction
Abstract
Background: In the last recent years a new percutaneous procedure, the MitraClip, has been validated for the treatment of mitral regurgitation. MitraClip procedure is a promising alternative for patients unsuitable for surgery as it reduces the risk of death related to surgery ensuring a similar result. Few data are present in literature about the variation of hemodynamic parameters and ventricular coupling after Mitraclip implantation.
Methods: Hemodynamic data of 18 patients enrolled for MitraClip procedure were retrospectively reviewed and analyzed. Echocardiographic measurements were obtained the day before the procedure (T0) and 21 ± 3 days after the procedure (T1), including evaluation of Ejection Fraction, mitral valve regurgitation severity and mechanism, forward Stroke Volume, left atrial volume, estimated systolic pulmonary pressure, non invasive echocardiographic estimation of single beat ventricular elastance (Es(sb)), arterial elastance (Ea) measured as systolic pressure • 0.9/Stroke Volume, ventricular arterial coupling (Ea/Es(sb) ratio). Data were expressed as median and interquartile range. Measures obtained before and after the procedure were compared using Wilcoxon non parametric test for paired samples.
Results: Mitraclip procedure was effective in reducing regurgitation. We observed an amelioration of echocardiographic parameters with a reduction of estimated systolic pulmonary pressure (45 to 37,5 p = 0,0002) and left atrial volume (110 to 93 p = 0,0001). Despite a few cases decreasing in ejection fraction (37 to 35 p = 0,035), the maintained ventricular arterial coupling after the procedure (P = 0,67) was associated with an increasing in forward stroke volume (60,3 to 78 p = 0,05).
Conclusion: MitraClip is effective in reducing mitral valve regurgitation and determines an amelioration of hemodynamic parameters with preservation of ventricular arterial coupling.
Introduction
Mitral regurgitation (MR) is the second most frequent valve disease after aortic stenosis. Mitral valve surgery is the standard of care for patients presenting symptomatic or asymptomatic MR with evidence of left ventricle (LV) dysfunction or dilation; mitral valve repair should be the preferred technique when it is expected to be durable. However, many patients presenting a high surgical risk are treated with a strict titration of pharmacological therapy or resynchronization.
In recent years, a new percutaneous procedure using the MitraClip® has been validated for the treatment of mitral regurgitation. The positioning of a clip approximates leaflets at different locations mimicking Alfieri's surgical suture and creating a double orifice mitral valve. For large orifices more clips can be used to effectively reduce regurgitant volume. The Everest studies I and II demonstrated the safety and efficacy of the procedure. Furthermore, Ussia et al. demonstrated an improvement in quality of life in high surgical risk patients undergoing the MitraClip procedure. Therefore, the MitraClip procedure is considered to be a promising alternative for patients unsuitable for surgery ensuring a similar result.
One of the concerns when using this procedure in patients with advanced heart failure is that the acute correction of MR could further impair LV systolic performance, leading to a low or even lower cardiac output state.
Sunagawa demonstrated that the stroke volume produced by the heart is determined by the interaction between ventricular end-systolic elastance and arterial elastance. Ventricular end-systolic elastance (Ees) is defined by the slope of the end-systolic pressure-volume relationship (ESPVR) and is a measure of the contractility of the left ventricle, which is not influenced by pre-load changes. Arterial elastance (Ea) is considered a good index of vascular load and is determined using the compliance, impedance and resistances of the arterial system. End-systolic pressure follows maximal ejection pressure because end-systole occurs as LV relaxation starts. Therefore, it can be approximated using the ratio of 90% of the systolic arterial pressure to Stroke volume (SV). Sagawa et al. demonstrated that the cardiovascular system is efficient and produces the maximal stroke work when the Ea/Ees ratio is 0.5–1.
Because measuring Ees varying preload and ventricular end-systolic pressures invasively is difficult in clinical practice, single-beat methods were developed and validated for obtaining the Ees value (Ees(SB)). In particular, the Ees [SB] can be evaluated by measuring the LV ejection fraction (EF), Stroke volume (SV), pre-ejection time and systolic time interval when coupled with the systolic and diastolic arterial pressures (Figure 1).
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Figure 1.
Left ventricular end-systolic elastance was calculated by the single-beat method validated by Chen et al. [14]. The echo figures display the evaluation of ejection fraction (left panel) and pre-ejection and ejection time (right panel) using aortic Doppler waveform. Normalized ventricular elastance at arterial end-diastole (End) was measured according to the formula: Ees(sb) = [Pd - (ENd(est) • Ps • 0.9)]/[SV • ENd(est)], ENd(avg) = ∑ ai • tNdi = 0, ENd(est) = 0.0275 - 0.165 • EF + 0.3656 • (Pd/Pes) + 0.515 • ENd(avg) where ai are (0.35695, -7.2266, 74.249, -307.39, 684.54. -856.92, 571.95, -159.1) for i = 1 to 7, respectively. The value for tNd was determined by the ratio of pre-ejection period (R wave to flow onset) to total systolic period (R wave to end-flow), with the time of onset and termination of flow defined Doppler. Systolic (Ps) and diastolic (Pd) blood pressure were invasively obtained.
For this reason, we aimed to evaluate the hemodynamic effects of the MitraClip procedure, with particular emphasis on cardiomechanics, by non invasive evaluation of ventriculo-arterial coupling.