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 ± 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 <50% (area under the curve, 0.93; P < .001).
Conclusions
In chronic severe degenerative MR, disproportionately higher LV global longitudinal strain signifies a maladaptive preload-related change that is associated with substantial loss of LVEF immediately after MVr. Preoperative assessment of longitudinal strain may be potentially useful for optimizing the timing of MVr for degenerative MR.
Surgical correction of chronic severe degenerative mitral regurgitation (MR) has seen a preference toward repair rather than replacement, driven by an attempt to reverse left ventricular (LV) remodeling and improve LV function. However, an optimal operative outcome is dependent not only on a successful repair but also on the preoperative contractile reserve of a chronically volume loaded left ventricle. Current American College of Cardiology and American Heart Association practice guidelines suggest a role for mitral valve (MV) surgery in chronic severe degenerative MR once there is evidence of LV dysfunction (defined as LV ejection fraction [LVEF] < 60% and/or LV end-systolic diameter [LVESD] ≥ 40 mm). The preload and Doppler angle dependency of these markers limits their ability to detect latent LV dysfunction. Myocardial strain analysis has been proposed as a novel, Doppler angle–independent method that can detect early subclinical contractile impairment.
Although relevant literature underscores the benefit of this method, there is a dichotomy of opinion regarding the incremental value of strain over conventional parameters. In the present study, we examined the role of two-dimensional (2D) echocardiography–derived speckle-tracking strain analysis in patients with chronic severe degenerative MR. In particular, we sought to assess the incremental value of strain in predicting poor postoperative LV function immediately after MV repair (MVr) in patients with degenerative MV lesions according to Carpentier’s classification (fibroelastic deficiency and Barlow’s disease, including forme fruste Barlow’s deformity).
Methods
Patient Selection
From January 2002 to December 2010, 744 patients underwent MVr for chronic severe degenerative MR; the data from these patients were analyzed retrospectively. Patients with occlusive coronary artery disease ( n = 80 [10.8%]), connective tissue disorders ( n = 3 [0.4%]), previous sternotomy ( n = 44 [5.9%]), and additional valvulopathies ( n = 37 [5%]), except for tricuspid regurgitation, were excluded. An additional 227 cases were excluded because they were not saved in Digital Imaging and Communications in Medicine format from the referring institution, while cases with baseline transesophageal echocardiograms were also not included for strain analysis ( n = 223). Complete baseline and postoperative transthoracic echocardiographic studies were archived in 130 patients with optimal views (all six LV wall segments were visible with very low noise/image ratios, in four acquisition windows: parasternal two-chamber, three-chamber, four-chamber, and short-axis views at the mid-papillary muscle level). The protocol was approved by our local institutional review board and was compliant with Health Insurance Portability and Accountability Act regulations and the ethical guidelines of the 1975 Declaration of Helsinki. The approval included a waiver of the requirement for informed consent.
Population Characteristics
The mean age was 57 ± 14 years, and 85 (65%) were men. The grade of MR severity was assessed using semiquantitative Doppler measurement of regurgitant volumes, using the proximal isovelocity surface area method (when single jets were observed) or regurgitant Doppler jet area and systolic flow reversal within the pulmonary veins and/or inferior vena cava (in case of complex or multiple regurgitant jets), per current guidelines. From the total population, all patients were graded as having severe MR (regurgitant volume ≥ 60 mL/beat and/or jet area > 10 cm 2 ). Concomitant tricuspid regurgitation was present in 76 patients (59%) on the basis of prebypass transesophageal echocardiographic evidence of tricuspid annular dilatation (>35 mm in the apical four-chamber view), as well as a regurgitant jet area > 5 cm 2 or a high-density continuous-wave Doppler tricuspid regurgitation signal, spanning from mild to severe. Sixteen patients (12%) were identified with either past or present compensated congestive heart failure. Atrial fibrillation was present in 36 patients (28%), and an equal number had controlled systemic arterial hypertension. The logistic European System for Cardiac Operative Risk Evaluation score was calculated according to guidelines, and the mean value for the study group was 3.5 ± 2.9 ( Table 1 ). After dividing the population on the basis of whether the baseline LVEF was reduced by >10% postoperatively (group A, reduction of LVEF > 10%; group B, reduction of LVEF ≤ 10%), we compared baseline and postoperative characteristics of LV dimensions, function, and strain trends between groups A and B.
| Parameter | Value | Baseline | Postoperative | P |
|---|---|---|---|---|
| Age (y) | 54 ± 14 | |||
| Men | 85 (65%) | |||
| BSA (m 2 ) | 1.9 ± 0.3 | |||
| Logistic EuroSCORE | 3.5 ± 3 | |||
| AF | 36 (29%) | |||
| TR | 76 (59%) | |||
| CHF | 16 (12%) | |||
| MR volume (mL) | 118.2 ± 95.6 | |||
| MR etiology | ||||
| FED | 54 (42%) | |||
| BD | 76 (58%) | |||
| Ruptured chordae tendineae | 67 (52%) | |||
| Cross-clamp time (min) | 137 ± 48 | |||
| Bypass time (min) | 170 ± 57 | |||
| HTN | 38 (29%) | |||
| Creatinine (mg/dL) | 1.02 ± 0.6 | |||
| 2D echocardiography | ||||
| LVEDD (cm) | 5.6 ± 0.8 | 4.9 ± 0.8 | <.001 | |
| LVESD (cm) | 3.6 ± 0.7 | 3.6 ± 0.9 | .80 | |
| LVPWd (cm) | 0.98 ± 0.17 | 1.05 ± 0.16 | .0006 | |
| IVSd (cm) | 1.02 ± 0.22 | 1.07 ± 0.14 | .01 | |
| LVEDV (mL) | 150.4 ± 55.7 | 111 ± 45.7 | <.001 | |
| LVESV (mL) | 56.6 ± 28.2 | 57 ± 28.6 | .87 | |
| LVEF (%) | 62.5 ± 11 | 49.5 ± 12 | <.001 | |
| Speckle-tracking | ||||
| GLS (%) | −20.6 ± 5 | −13.3 ± 4.1 | <.001 | |
| GCS (%) | −26.4 ± 7.1 | −19.7 ± 6.1 | <.001 | |
| GRS (%) | 36.5 ± 18.8 | 23.9 ± 13.6 | <.001 |
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