Mitral regurgitation: comprehensive assessment by echocardiography

Coronary Sinus-Based Approach to Mitral Regurgitation

Functional, or secondary, mitral regurgitation (FMR) is clinically important because patient with congestive heart failure with FMR have worse clinical outcomes and associated higher risks than patients without FMR. There is interest in finding repair techniques which may modify the mitral valve dysfunction and reduce the clinical impact. Although several devices have taken advantage of the close anatomical relationship between the coronary sinus and the posterior annulus of the mitral valve, in order to provide a cinching force on the mitral annulus, only the Carillon device is currently in use in humans. A double blind randomized trial is currently being done to evaluate the value of this therapy, building upon the favorable result of three prior safety and efficacy trials, which have led to European approval of the device.

Hemodynamic aspects of mitral regurgitation assessed by generalized phase-contrast MRI

PURPOSE

To investigate the utility of MRI measurement of left atrial (LA) flow patterns and turbulent kinetic energy (TKE) in patients with clinically significant mitral regurgitation.

MATERIALS AND METHODS

Three-dimensional cine phase-contrast MRI (PC-MRI) data were acquired in five patients with posterior mitral leaflet prolapse and two normal volunteers. LA flow patterns were assessed using particle trace visualization. Specifically, vortices were recognized by closed streamlines. LA flow distortion was assessed by estimation of TKE. In addition, the regurgitant volume was measured.

RESULTS

Four of the mitral regurgitation patients had eccentric regurgitant jets directed toward the septum; one patient had a central jet. The dominant systolic vortex was located in proximity to the regurgitant jet. The LA flow was highly disturbed with elevated values of TKE; peak LA TKE ranged from 13 to 37 mJ and occurred consistently at late systole. The average LA TKE per cardiac cycle was significantly related to the regurgitant volume (TKE = 0.573 + 0.179·RegVol, R(2) = 0.983).

CONCLUSION

MRI permits investigations of atrial flow patterns and TKE in significant mitral regurgitation. The degree of LA flow distortion, as measured by the average LA TKE over one cardiac cycle, appears to reflect the severity of regurgitation.

Lessons learned from a pediatric clinical trial: the Pediatric Heart Network angiotensin-converting enzyme inhibition in mitral regurgitation study

BACKGROUND

Mitral regurgitation is the most common indication for reoperation in children following repair of atrioventricular septal defect (AVSD). We hypothesized that angiotensin-converting enzyme inhibitor therapy would decrease the severity of mitral regurgitation and limit left ventricular volume overload in children following AVSD repair.

METHODS

The Pediatric Heart Network designed a placebo-controlled randomized trial of enalapril in this population. The primary aim was to test the effect of enalapril on the change in left ventricular end-diastolic dimension body surface area-adjusted z score. Before the launch of the trial, a feasibility study was performed to estimate the number of patients with at least moderate mitral regurgitation following AVSD repair.

TRIAL EXPERIENCE

Seventeen months after the start of the study, 349 patients were screened, 8 were trial eligible, and only 5 were enrolled. The study was subsequently terminated because of low patient accrual. Several factors led to the problems with patient accrual, including (1) the use of criteria to assess disease severity in the feasibility study that were not identical to those used in the trial, (2) failure to achieve equipoise for the study among clinicians and referring physicians, (3) reliance on methodology developed in adult populations with different disease mechanisms, and (4) absence of adequate data to define the natural history of the disease process under study. Progress in the treatment of children with cardiovascular disease will depend on the future of multicenter collaborative clinical trials. The lessons learned from this study may contribute to improvements in this research.

Prognostic implication of valvular lesion and left ventricular size in asymptomatic patients with chronic organic mitral regurgitation and normal left ventricular performance

OBJECTIVE

To date, few studies have evaluated asymptomatic patients with organic mitral regurgitation (MR). The goal of the present study was to assess the presence of independent predictive factors for progression of symptoms and/or left ventricular dysfunction (SLVSD) in this population.

METHODS

We prospectively evaluated 128 consecutive patients (mean age 60 +/- 8 years, 68% men; ejection fraction 66 +/- 3%) who were asymptomatic, with severe organic MR. Mean follow-up was 29 +/- 12 months. The combined end point was SLVSD. Clinical and echocardiographic variables were evaluated. Follow-up data were also estimated considering the annualized rate (?) of the echocardiographic indices.

RESULTS

Thirty-seven patients (29%) had SLVSD during follow-up. Cox regression model identified the effective regurgitant orifice area (EROA) >55 mm2 (risk ratio 6.3, 95% CI 2.3-8.1, P < .001) and end-systolic diameter >22 mm/m2 (risk ratio 4.5, 95% CI, 1.8-9.4, P < .02) as the only independent predictors of SLVSD. When the follow-up data were added, the ?EROA (>15 mm2/y) was independently associated with the end point.

CONCLUSION

In asymptomatic patients with organic MR, the EROA and the end-systolic diameter are independent predictors of SLVSD and allow a better risk stratification in this group of patients. ANALYTICAL SUMMARY: The goal of this study was to determine the presence of independent predictors of symptomatic progression, and/or left ventricular dysfunction in asymptomatic patients with severe mitral regurgitation. We prospectively evaluated 128 consecutive patients (mean age 60 +/- 8 years, 68% male; ejection fraction 66 +/- 3%). During follow-up (mean 29 +/- 12 months). The end point occurred in 37 patients (29%). Multivariate analysis using Cox model identified the effective regurgitant orifice area (EROA) >55 mm2 (RR: 6.3; 95% CI: 2.3-8.1; P < .001) and an end-systolic diameter (ESD) >22 mm/m2 (RR: 4.5; 95%CI: 1.8-9.4; P < .02) as the only independent predictors of the end point. When the follow-up data were added, the annualized change rate of the EROA (>15 mm2/year) was independently associated with the end point. In asymptomatic patients with organic mitral regurgitation, the EROA and ESD at study entry were independent predictors of the combined end point and allowed a better risk stratification in this group of patients.

Semiquantitative and Quantitative Color Flow Mapping Methods

Conventional pulsed and continuous-wave Doppler applications have been in use since the mid-1970s. The first color flow mapping system was a color m-mode instrument developed by a Swiss engineer named Brandistini. Stevenson and coworkers utilized this system for cardiac sonographic examinations in the late 1970s, but in general, there was very little interest in the method until the early 1980s, when a 2D color flow mapping system became available. With this new technology and the interest it generated, the development in color flow mapping Doppler technology moved at a rapid pace.

Technique and outcome of mitral valve replacement in dogs

Eight dogs with naturally occurring severe mitral regurgitation underwent mitral valve replacement with a mechanical valve prosthesis during cardiopulmonary bypass. Dogs received warfarin orally after surgery to maintain a prothrombin time-based international normalized ratio from 2.5 to 3.5. Seven dogs survived surgery. Left ventricular diastolic volume index decreased significantly from 206 +/- 91 mL/m2 before surgery to 121 +/- 47 mL/m2 after surgery. Left atrium-to-aorta ratio decreased significantly from 2.66 +/- 0.4 before surgery to 1.73 +/- 0.65 after surgery. Left ventricular systolic volume index was not significantly different after surgery (56 +/- 36 mL/m2), compared with before surgery (40 +/- 32 mL/m2). Median survival after surgery was 4.5 months (range, 0.75 months to 5.25 years). Six dogs died of confirmed or suspected thrombosis of the valve prosthesis. Dogs with severe mitral regurgitation tolerated mitral valve replacement well, but a high incidence of prosthetic valve thrombosis limited long-term outcome.

Pointwise assessment of three-dimensional computer reconstruction of mitral leaflet surfaces from rotationally scanned echocardiograms in vitro

Three-dimensional transesophageal echocardiography offers promise for improved understanding of mitral leaflet pathology, but it has not been validated quantitatively, nor has the minimum number of imaging planes for satisfactory reconstruction been determined with a rotational scanning geometry. This study assessed its accuracy in vitro by comparing, on a 1 x 1-mm grid, the surfaces of mitral leaflets derived from 5-degree rotational ultrasonic scans with those derived from laser scans of casts of the atrial side of the leaflets. Overall, the ultrasonically derived surface had a mean absolute deviation of 0.65 +/- 0.12 mm from the laser-derived surface. Using only alternate imaging planes (10-degree increments) made no significant difference in the overall distribution of deviations (P =.56), although the distributions on some individual specimens differed markedly. We conclude that 5-degree rotational scanning in vitro can reconstruct the mitral valve leaflets with sufficient accuracy and detail to render clinically important features.

Detection of mechanisms of immediate failure by transesophageal echocardiography in quadrangular resection mitral valve repair technique for severe mitral regurgitation

Residual mitral regurgitation (MR) after repair is a risk factor for late reoperation. The use of intraoperative transesophageal echocardiography (IOTEE) decreases the incidence of immediate repair failure. This study identifies the mechanisms of immediate failure by IOTEE in the quadrangular resection technique, a well-standardized mitral valve repair procedure to guide further repair procedures. Two hundred five consecutive patients underwent quadrangular resection due to prolapse or flail posterior leaflet. Twenty-four patients (11%) had immediate failure. Immediate reinstitution of cardiopulmonary bypass ("second pump run") was needed in 21 patients (10%) for further repair. The identified mechanisms of failure were residual cleft provoking interscallop malcoaptation into the posterior leaflet in 8 patients, residual prolapse of the anterior or posterior leaflets in 1 and 4 patients, respectively, residual annular dilation in 3, left ventricular outflow obstruction in 2, suture dehiscence in 2, and other mechanisms in another 2 patients. In 20 patients (95%), IOTEE guided further repair with resolution of the residual MR, whereas 1 patient underwent valve replacement due to pharmacologically untreatable left ventricular outflow obstruction. In conclusion, even if this type of valve repair technique is well standardized, the incidence of immediate failure is not negligible. IOTEE identified the mechanisms of the immediate failure and guided further repair procedures, thus reducing the incidence of valve replacement (0.5%) without increasing perioperative mortality and morbility.

Native mitral valve regurgitation. Proactive management can improve outlook

Mitral regurgitation is a common valvular abnormality that can result in substantial morbidity. Primary care physicians should maintain a high index of suspicion for this disorder, especially in patients with symptoms of heart failure. The paramount concern is early identification of patients with mitral regurgitation and prompt referral to a cardiologist when symptoms occur or if evidence of ventricular enlargement or reduction in ejection fraction is found. Echocardiography is an invaluable tool in determining the severity of regurgitation, the integrity of the mitral valve apparatus, the extent of left ventricular enlargement, and the ejection fraction. Although no standard medical treatment has been established for mitral regurgitation, use of ACE inhibitors is appropriate. Patients presenting with severe, acute mitral regurgitation from papillary muscle rupture should be evaluated for ischemia and treated expediently. The preferred operative procedure in patients with severe mitral regurgitation and left ventricular dysfunction is mitral valve repair, if possible, or mitral valve replacement with posterior chordal preservation, if feasible.