Assessment of Longitudinal Myocardial Mechanics in Patients with Degenerative Mitral Valve Regurgitation Predicts Postoperative Worsening of Left Ventricular Systolic Function Dimosthenis Pandis, MD, MSc, Partho P. Sengupta, MD, DM, Javier G. Castillo, MD, Giuseppe Caracciolo, MD, PhD, Gregory W. Fischer, MD, Jagat Narula, MD, PhD, Anelechi Anyanwu, MD, FRCS, and David H. Adams, MD, New York, New York
Background: The optimal timing of mitral valve repair (MVr) in patients with chronic severe degenerative mitral regurgitation (MR) remains controversial and is broadly based on either measurable loss of systolic function, as determined by left ventricular (LV) ejection fraction (LVEF) and/or LV chamber remodeling. The aim of this study was to test the hypothesis that the assessment of LV deformation by speckle-tracking echocardiography might uncover subclinical changes for predicting reduction of LVEF after MVr. Methods: One hundred thirty patients (mean age, 57 6 14 years; 85 men) who underwent MVr for chronic severe degenerative MR were retrospectively identified. Baseline and immediate postoperative transthoracic echocardiography was used to assess global longitudinal strain (GLS), global radial strain, and global circumferential strain before and after MVr. Results: In comparison with baseline, MVr resulted in significant reductions in LVEF (P < .0001) and in GLS (P < .0001). Postoperative change in LVEF was related to the changes in GLS (r = 0.71, P < .0001) and global circumferential strain (r = 0.22, P = .01) but not global radial strain. For the entire group, the presence of a high preoperative GLS magnitude predicted a postoperative reduction in LVEF of >10% (odds ratio, 0.80; P < .001). Furthermore, GLS showed diagnostic value in predicting a reduction in LVEF of >10% with a resulting postoperative LVEF of 10%) after MVr surgery. The concerted contribution of radial and circumferential fibers together with the longitudinal component is crucial in maintaining forward stroke during disease states. In patients with heart failure,
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for example, there is marked attenuation of LV mechanics along the longitudinal axis, and radial and circumferential deformation are primarily correlated with LVEF.31 On the contrary, in primary degenerative MV disease, it seems that to maintain global systolic function (and LVEF), an increase in LV longitudinal mechanics (and thus greater longitudinal strain amplitude) takes place, which compensates for the small contributions of the circumferential and radial components. Moreover, only LV longitudinal mechanics predicted LV dysfunction after MVr. Impact of Chronic Degenerative MR on LV Alteration and Symptoms Patients with severe MR may have diverse baseline LV function, and markers such LVEF and LV dimensions32,33 may not be sensitive to the presence of subclinical LV dysfunction, which is important to recognize before MV reconstructive surgery. Moreover, not all patients actually exhibit clinical symptoms, and LVEF may appear spuriously normal because of compensatory changes in multidirectional LV mechanics. Recognizing these subclinical changes is particularly relevant for patients with LVEFs of 50% to 60%, because these patients have inferior prognosis34 and worse survival.2 Our results indicate that patients with severe primary degenerative MR may appear to have near normal LVEFs because of disproportionately higher compensation in GLS. It has been postulated that the subendocardium is the most vulnerable to preload alterations, and therefore patients with primary degenerative MR may have larger shortening strains along the LV longitudinal axis.35 However, this change may be only related to the regurgitation and not contribute to forward stroke volume in the systemic circulation. Patients with higher disproportionate strain in the longitudinal direction would also subsequently have the highest risk for substantial reduction in LVEF (>10%) following MVr. To yield a better correlation of strain with the changes imposed on the left ventricle after MVr, we elected to use the postoperative change in LVEF rather than the absolute postoperative value.13,14,33 The latter isolates the events from their starting point, which carries the risk for grouping patients with low postoperative LVEF as worse than those with higher absolute LVEF after surgery but with greater reductions from their baseline LVEF. Although all three baseline strains were lower in patients with preoperative LVEF < 50%, only GLS correlated well with postoperative reduction in LVEF of >10%. These findings may extend important clinical significance in choosing surgical candidates for mitral reconstructive surgery. A priori knowledge of probable poor postoperative performance may guide a modification of surgical technique during mitral reconstruction, shorter myocardial ischemic time, and/or modifications to myocardial protection method.
Figure 5 (A) Scatter diagram and regression line of the relationship between postoperative LVEF change and change in longaxis mechanics (longitudinal strain [LS]) and radial axis mechanics (circumferential strain [CS] and radial strain [RS]). LV long-axis mechanics show the strongest relationship with the
change in LVEF after MVr, whereas CS confers a weaker contribution, and the RS component makes no contribution. (B) Comparison of correlation coefficients between postoperative change in LVEF and changes in LS, CS, and RS. LV long-axis mechanics appear most strongly associated with the postoperative changes in LVEF after MVr. The radial axis seems to only partially contribute, with an otherwise smaller association via CS, while the radial component does not infer an association with LVEF change, in patients with degenerative MR undergoing MVr. The table insert shows the Z statistic and respective P value for each pair comparison. FED, Fibroelastic deficiency; GCS, global circumferential strain; GRS, global radial strain.
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Table 3 Comparative correlations between change in LVEF and changes in GLS, GCS, and GRS after MVr, across different baseline LVEF subgroups GLS Correlation
LVEF (%) 70 (n = 35)
0.58 0.65 0.57 0.44
.036 .0002 10%. This result is different from the findings of Florescu et al.16 In their study, a subgroup that showed postoperative LVEF reductions > 10% (n = 13) had lower baseline strains compared with patients with LVEF reductions < 10% (n = 15) (P = .001). These were all
Figure 6 (A) Clustered comparison of baseline and postoperative LVEF in different baseline LVEF groups. Patients with higher baseline LVEFs demonstrated greater LVEF reductions after MVr. (B) Comparison of LVEF change after MVr, at different levels of baseline LVEF. The reduction was greater at higher baseline LVEF values. EF, Ejection fraction. asymptomatic patients (New York Heart Association class I) with baseline LVEFs > 60%, tested at 6 months after surgery, when LV reverse remodeling has settled, whereas our population had a more diverse clinical presentation and was tested during the immediate postoperative period. Clinical Implications The concept of surgical intervention when LVEF decreases to 40 mm, and/or symptoms enter the realm of New York Heart Association classes III and IV has matured for over 30 years,36-39 and recent guidelines reflect a change in thought.40 When assessing the contractile functional status of the left ventricle under various loading conditions, speckle-tracking-derived strain analysis is faster, cost efficient (compared with cardiac magnetic resonance imaging), and less invasive (compared with catheterization). According to our results, longitudinal strain may offer a practical and more reliable platform to identify subclinical changes in LV function that impose risk for substantial reduction in LVEF after MVr. When baseline GLS is < 20%, indicating disproportionately higher compensation in the longitudinal direction, this may indicate a risk for substantial loss of LVEF after MVr, which may be particularly relevant for patients with LVEFs of 50% to 60%, in whom a 10% postoperative reduction may lead to adverse outcomes.
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Table 5 Conventional LV echocardiographic and strain parameters influencing LVEF change after MVr in patients with chronic severe degenerative MR Variable
LVEDD LVESD LVEDV LVESV SV RA pressure PA pressure* High EuroSCORE GLS GCS GRS
1.0 1.1 1.0 0.9 1.0 0.8 0.9 0.2 0.8 0.9 1.0
0.66–1.73 0.63–1.92 0.99–1.01 0.96–0.99 1.01–1.02 0.77–0.94 0.95–1.02 0.03–0.93 0.73–0.88 0.92–1.02 0.98–1.02
.78 .72 .42 .009 .001 .002 .45 .04 10% with concomitant postoperative LVEF < 50% (blue solid line). See text for details.
RA pressure 10.9 0.86 0.7–0.9 .002 0.84 0.75–0.95 .004 LVESV 7.45 0.9 0.96–0.99 .009 GLS 25.7 0.8 0.7–0.9