The management of functional mitral regurgitation

Percutaneous repair of mitral valve regurgitation in patients with severe heart failure: comparison with optimal medical treatment

BACKGROUND

Occurrence of severe mitral valve (MV) regurgitation (MR) is an independent negative predictor of mortality in patients with severe systolic heart failure (HF). This study examines clinical effects and cardiac reverse remodelling in patients with severe systolic HF receiving percutaneous mitral valve repair (PMVR) using MitraClip in comparison to patients receiving optimal medical therapy only.

METHODS

Between 2010 and 2014, 86 patients (Society of Thoracic Surgeons score: 10.5% ± 1.2%) with severe HF (left ventricular [LV] ejection fraction; LVEF: 25% ± 2%; LV endsystolic diameter [LVESD]: 55 ± 3 mm) and severe MR received PMVR using MitraClip. Cardiac reverse remodelling and clinical parameters were compared to HF patients with severe MR (from our HF outpatient clinic; n = 69; LVEF: 26% ± 1.4%; LVESD: 53 ± 2 mm) receiving optimal medical therapy (OMT) only. All patients received stable OMT and were characterised by echocardiography, 6-minwalk-distance test and cardiac biomarkers within a 24 months observation period.

RESULTS

PMVR in patients with end-stage HF and severe MR resulted in reduction of MR and significant additional cardiac reverse remodelling (LVEF: 26 ± 1.4 vs. 33% ± 2%, p < .05; LVESD: 53 ± 2 vs. 47 ± 2 mm, p < .05) over the 24 months observation period as compared to pharmacologically-only managed comparators.

CONCLUSIONS

Both OMT and PMVR cause cardiac reverse remodelling and relief of symptoms in patients with HF and severe MR. PMVR results in significant additional cardiac reverse remodelling compared to pharmacologically-only managed patients.

Cardiomyocyte mitochondrial oxidative stress and cytoskeletal breakdown in the heart with a primary volume overload

Left ventricular (LV) volume overload (VO) results in cardiomyocyte oxidative stress and mitochondrial dysfunction. Because mitochondria are both a source and target of ROS, we hypothesized that the mitochondrially targeted antioxidant mitoubiquinone (MitoQ) will improve cardiomyocyte damage and LV dysfunction in VO. Isolated cardiomyocytes from Sprague-Dawley rats were exposed to stretch in vitro and VO of aortocaval fistula (ACF) in vivo. ACF rats were treated with and without MitoQ. Isolated cardiomyocytes were analyzed after 3 h of cyclical stretch or 8 wk of ACF with MitoSox red or 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate to measure ROS and with tetramethylrhodamine to measure mitochondrial membrane potential. Transmission electron microscopy and immunohistochemistry were used for cardiomyocyte structural assessment. In vitro cyclical stretch and 8-wk ACF resulted in increased cardiomyocyte mitochondrial ROS production and decreased mitochondrial membrane potential, which were significantly improved by MitoQ. ACF had extensive loss of desmin and β₂-tubulin that was paralleled by mitochondrial disorganization, loss of cristae, swelling, and clustering identified by mitochondria complex IV staining and transmission electron microscopy. MitoQ improved mitochondrial structural damage and attenuated desmin loss/degradation evidenced by immunohistochemistry and protein expression. However, LV dilatation and fractional shortening were unaffected by MitoQ treatment in 8-wk ACF. In conclusion, although MitoQ did not affect LV dilatation or function in ACF, these experiments suggest a connection of cardiomyocyte mitochondria-derived ROS production with cytoskeletal disruption and mitochondrial damage in the VO of ACF.

[Mitral regurgitation in heart failure. Surgical therapy]

The optimal treatment of mitral regurgitation concomitant to heart failure remains controversial. A lack of consensus between cardiologists and cardiac surgeons, because of limited studies and heterogeneous data, has led to vaguely defined guidelines and different handling in the clinical routine in the past. However, progress in the operative management with excellent results of individual experienced centers suggests that a variety of patients might benefit from surgical therapy. Each patient should be evaluated individually regarding the benefits of surgical therapy which requires an interdisciplinary approach ("heart team") due to the complex pathophysiology and demanding diagnostics.

Quantitative evaluation of change in coexistent mitral regurgitation after aortic valve replacement

OBJECTIVES

Management of intermediate degrees of mitral regurgitation during aortic valve replacement for aortic stenosis remains controversial. We sought to evaluate the degree of reduction of mitral regurgitation in patients undergoing aortic valve replacement, as well as a mathematical relationship between aortic valve gradient reduction and the degree of mitral regurgitation decrement.

METHODS

We retrospectively analyzed demographic, intraoperative, and echocardiographic data on 802 patients who underwent aortic valve replacement or aortic root replacement between January 2010 and March 2011. A total of 578 patients underwent aortic valve replacement or aortic root replacement without intervention on the mitral valve. We excluded 88 patients with severe aortic insufficiency, 3 patients who underwent ventricular assist device placement, 4 patients who underwent prior mitral valve replacement, and 21 patients with incomplete data, yielding 462 patients for analysis. For each patient, the degree of pre- and postoperative mitral regurgitation was graded on a standard 0 to 4+ scale.

RESULTS

Of the 462 patients, 289 patients had at least mild mitral regurgitation. On average, mitral regurgitation decreased 0.24 degrees per patient for this cohort of 289 patients. Of the 56 patients with at least moderate mitral regurgitation, mitral regurgitation decreased 0.54 degrees per patient. Of 62 patients who underwent isolated aortic valve replacements, who had at least mild mitral regurgitation, and who had no evidence of structural mitral valve disease, mitral regurgitation decreased 0.24 degrees per patient. Linear regression analysis revealed no relationship between reduction in mitral regurgitation and gradient reduction across the aortic valve.

CONCLUSIONS

Reduction in mitral regurgitation after relief of aortic outflow tract obstruction is modest at best. Further, the magnitude of gradient change across the aortic valve has little influence on the degree of reduction in mitral regurgitation. These observations argue at minimum for performing a prospective evaluation of the clinical benefits of addressing moderate mitral regurgitation at the time of aortic valve intervention and may support a more aggressive approach to concomitant mitral surgery.

Mechanisms and predictors of mitral regurgitation after high-risk myocardial infarction

BACKGROUND

Mitral regurgitation (MR) has been associated with adverse outcomes after myocardial infarction (MI). Without structural valve disease, functional MR has been related to left ventricular (LV) remodeling and geometric deformation of the mitral apparatus. The aims of this study were to elucidate the mechanistic components of MR after high-risk MI and to identify predictors of MR progression during follow-up.

METHODS

The Valsartan in Acute Myocardial Infarction Echo substudy prospectively enrolled 610 patients with LV dysfunction, heart failure, or both after MI. MR at baseline, 1 month, and 20 months was quantified by mapping jet expansion in the left atrium in 341 patients with good-quality echocardiograms. Indices of LV remodeling, left atrial size, and diastolic function and parameters of mitral valve deformation, including tenting area, coaptation depth, anterior leaflet concavity, annular diameters, and contractility, were assessed and related to baseline MR. The progression of MR was further analyzed, and predictors of worsening among the baseline characteristics were identified.

RESULTS

Tenting area, coaptation depth, annular dilatation, and left atrial size were all associated with the degree of baseline MR. Tenting area was the only significant and independent predictor of worsening MR; a tenting area of 4 cm(2) was a useful cutoff to identify worsening of MR after MI and moderate to severe MR after 20 months.

CONCLUSIONS

Increased mitral tenting and larger mitral annular area are determinants of MR degree at baseline, and tenting area is an independent predictor of progression of MR after MI. Although LV remodeling itself contributes to ischemic MR, this influence is directly dependent on alterations in mitral geometry.

Reduced systolic torsion in chronic "pure" mitral regurgitation

BACKGROUND

Global left ventricular (LV) torsion declines with chronic ischemic mitral regurgitation (MR), which may accelerate the LV remodeling spiral toward global cardiomyopathy; however, it has not been definitively established whether this torsional decline is attributable to the infarct, the MR, or their combined effect. We tested the hypothesis that chronic "pure" MR alone reduces global LV torsion.

METHODS AND RESULTS

Chronic "pure" MR was created in 13 sheep by surgically punching a 3.5- to 4.8-mm hole (HOLE) in the mitral valve posterior leaflet. Nine control (CNTL) sheep were operated on concurrently. At 1 (WK-01) and 12 weeks (WK-12) postoperatively, the 4D motion of implanted radiopaque markers was used to calculate global LV torsion. MR-grade in HOLE was greater than CNTL at WK-01 and WK-12 (2.5+/-1.1 versus 0.6+/-0.5, P<0.001 at WK-12). HOLE LV mass index was larger at WK-12 compared with CNTL (195+/-14 versus 170+/-17 g/m(2), P<0.01), indicating LV remodeling. Global LV systolic torsion decreased in HOLE from WK-01 to WK-12 (4.1+/-2.8 degrees versus 1.7+/-1.7 degrees , P<0.01), but did not change in CNTL (5.5+/-1.8 degrees versus 4.2+/-2.7 degrees , P=NS). Global LV torsion was lower in HOLE relative to CNTL at WK-12 (P<0.05) but not at WK-01 (P=NS).

CONCLUSIONS

Twelve weeks of chronic "pure" MR resulting in mild global LV remodeling is associated with significantly increased LV mass index and reduced global LV systolic torsion, but no other significant changes in hemodynamics. MR alone is a major component of torsional deterioration in "pure" MR and may be an important factor in chronic ischemic mitral regurgitation.