Treatment of chronic mitral regurgitation

State of the art: degenerative mitral valve disease

Mitral valve repair offers superior long-term survival, freedom from cardiac morbidity, and quality of life in patients with severe mitral regurgitation compared to medical management and mitral valve replacement; it is the treatment of choice in these patients. Mitral valve repair is the only treatment that restores normal life expectancy to otherwise healthy patients with advanced degenerative mitral valve disease. This review focuses on indications, timing and techniques for mitral valve repair in degenerative disease, emphasising the importance of anatomy in surgical outcomes.

Echocardiographic quantitation of mitral regurgitation

Mitral valve regurgitation is a common valvular problem, particularly in developing nations. It causes significant morbidity and mortality, especially if the severity of valve regurgitation is underestimated. Echocardiography plays a significant role in the diagnoses, serial follow-up and management of patients with valvular heart disease. However, precise quantitation of the severity of mitral regurgitation is a crucial element in the therapeutic decisions for managing mitral regurgitation. An accurate assessment of the severity of mitral regurgitation allows for optimal timing of surgical intervention, culminating in improved patient outcomes. This review provides a systematic approach to the quantitation of mitral regurgitation using the echocardiography and Doppler methodologies that are available in the modern noninvasive imaging and hemodynamic laboratory. Additional, novel and evolving noninvasive imaging modalities are reviewed briefly.

Mitral regurgitation: determinants of referral for cardiac surgery by Canadian cardiologists

PURPOSE

Advances in surgery permit for earlier intervention with improved outcomes for patients with mitral regurgitation (MR). Many patients still appear to be referred to surgery late in their course. Consensus guidelines were compared with the surgical referral practices for MR among Canadian cardiologists.

METHODS

A self-administered questionnaire was mailed to all adult cardiologists in Canada. This included seven case scenarios, as well as direct questions designed to establish the influence of factors including atrial fibrillation, pulmonary hypertension, left ventricular (LV) dilation, experience of the cardiac surgeon, symptoms and ejection fraction (EF) on referral.

RESULTS

There were 319 respondents; LVEF was rated as extremely important in 71.5% of patients and moderately important in 26% of patients. In asymptomatic patients, EF of 50% to 60% was correctly identified as a trigger for surgery by 57.2 % of cardiologists, while only 15.6% of cardiologists correctly referred New York Heart Association class II patients with normal LV function. The group complied in only 4.77 of the seven case scenarios. Compliance was inversely related to years in practice for asymptomatic patients with mild LV dysfunction, as well as in overall compliance. Referral practices were similar among clinicians, echocardiographers, interventional cardiologists and researchers, with no differences in geographic region or academic affiliation.

CONCLUSION

Compliance with published guidelines for patients with MR and either New York Heart Association class II or mild LV dysfunction among Canadian cardiologists was poor. Compliance was somewhat better in more recent graduates, suggesting the need to institute programs geared at enhancing knowledge of published standards and introduce practical tools to aid in their implementation.

Role of vasodilators in regurgitant valve disease

Vasodilator therapy is designed to reduce regurgitant volume and improve left ventricular function. Acute administration reduces vascular resistance and decreases regurgitant volume and left ventricular filling pressure. These effects may be clinically useful in acute regurgitations, but less consistent results have been reported in long-term therapy. In chronic mitral functional regurgitation, vasodilator therapy has proved to have clinical or prognostic benefit only when heart failure or poor ventricular function is present. The indication of vasodilator treatment in aortic regurgitation has raised significant controversy. Several studies with small series have shown beneficial effects on regurgitant volume, ejection fraction, and mass of the left ventricle. Nevertheless, in the only two randomized long-term follow-up studies, results differed completely. In our experience, both nifedipine and enalapril failed to reduce the need for valvular surgery or show benefits in echocardiographic parameters. Vasodilator therapy would be indicated only in patients with severe aortic regurgitation and systemic hypertension, or when surgery is contraindicated.

Ventricular assistance with microaxial flow pump following mitral repair for dilated cardiomyopathy

BACKGROUND

Postcardiotomy heart failure is still the main cause of death in patients undergoing palliative surgery for end-stage dilative cardiomyopathy. New micro-axial flow ventricular assisting devices (LVAD) have been suggested in such cases.

OBJECTIVE

Evaluate the effect of the new LVAD on short-term outcome of a patient admitted for end-stage heart failure.

STUDY DESIGN

Case report.

DATA SOURCES

One patient admitted for severe mitral regurgitation secondary to end-stage dilative cardiomyopathy and chronic atrial fibrillation (AF).

INTERVENTION

Preoperative intraaortic balloon pump (IABP) insertion, mitral plasty with radiofrequency ablation of AF, microaxial flow LVAD support.

RESULTS

The patient was unweanable from cardiopulmonary bypass until microaxial flow LVAD unloaded the left ventricle and restored adequate cardiac function. The patient was discharged home and is still well at 5 months folllow-up.

CONCLUSIONS

The miniinvasive insertion and withdrawal, low anticoagulation protocols, and the possibility of coupling with IABP make the microaxial flow LVAD promising for patients with end-stage heart failure undergoing surgery.

Medical and surgical treatment of chronic mitral regurgitation

Chronic severe mitral regurgitation is a progressive disease that can lead to left ventricular dysfunction. New information on the natural history of the disease, along with advances in surgical techniques, has changed the roles of medical and surgical therapies. There is no well-defined role for medical therapy in chronic mitral regurgitation. The goal of the treating physician is therefore to identify the optimal timing for surgical intervention. The timing of surgical intervention depends primarily on two factors: (i) clinical symptoms and (ii) the left ventricular response to volume overload. However, the aetiology of mitral regurgitation, the likelihood of surgical repair, the occurrence of atrial fibrillation and the presence of pulmonary hypertension, together with the haemodynamic response to exercise, are important factors in the optimal surgical timing. New concepts in the understanding of the natural history of the disease coupled with success of mitral repair have recently resulted in a widespread evolution towards earlier surgery.

Triple valve repair for rheumatic heart disease

The onset of the clinical expression of rheumatic heart disease (RHD) is variable. Exercise or other states that necessitate increased cardiac output often precipitate symptoms. Mitral stenosis (MS) is present in 25% of patients with RHD, and 40% of patients have concomitant MS and mitral regurgitation. About two third of patients with MS have concurrent aortic insufficiency. Pulmonary and tricuspid insufficiency may occur from rheumatic involvement of these valves, or secondary to dilatation of valve annuli from pulmonary hypertension secondary to mitral and/or aortic valve disease. Pregnancy is associated with many hemodynamic changes including expanded intravascular volume, tachycardia, increased intracardiac dimensions, and valvular regurgitation. We report a case of a young female who developed flash pulmonary edema during parturition and was found to have abnormal rheumatic involvement of her aortic, mitral, and tricuspid valves. Successful triple valve repair was performed in a single operation. A review of rheumatic valvular abnormalities, and literature supporting multivalvular repair for rheumatic heart disease is provided.

Selecting patients with mitral regurgitation and left ventricular dysfunction for isolated mitral valve surgery

BACKGROUND

American College of Cardiology/American Heart Association (ACC/AHA) Guidelines state that patients with an ejection fraction (EF) of 30% or less should not undergo mitral valve replacement for mitral regurgitation (MR). We sought to establish, using a national cardiac surgery database, whether patients with left ventricular dysfunction may safely undergo mitral valve surgery for MR, and if so, which ones.

METHODS

We queried the Society of Thoracic Surgeons (STS) National Database to identify patients who had isolated mitral valve replacement or repair for MR between 1998 and 2001. Mortality and morbidity outcomes were compared by EF category (< or = 30% vs > 30%), and observed mortality compared by EF group, stratified by predicted risk for mortality. A classification and regression tree (CART) model was then used to determine which patient characteristics contributed most to designate the high-risk patient.

RESULTS

Of the 14,582 patients who had mitral valve surgery, 727 had an EF of 30% or less and 13,855 had an EF of more than 30%. Observed mortality rates were higher for patients with an EF of 30% or less (5.4% vs 3.1%). However, for low-risk to medium-risk patients, mortality rates remained fairly constant across levels of EF. Mortality is notably increased in the high-risk patients (predicted risk > 10%). A classification tree identifies three key characteristics for high risk: age more than 75 years, renal failure, and emergent or salvage procedure.

CONCLUSIONS

When the predicted mortality risk is less than 10%, EF has minimal impact on operative mortality for mitral regurgitation. In contrast to the ACC/AHA Guidelines, our data show that operative risk for mitral valve surgery is not prohibitive for most patients with ventricular dysfunction.

Percutaneous mitral valve repair: A feasibility study in an ovine model of acute ischemic mitral regurgitation

Annuloplasty is the cornerstone of surgical mitral valve repair. A percutaneous transvenous catheter-based approach for mitral valve repair was tested by placing a novel annuloplasty device in the coronary sinus of sheep with acute ischemic mitral regurgitation. Mitral regurgitation was reduced from 3-4+ to 0-1+ in all animals (P < 0.03). The annuloplasty functioned by reducing septal-lateral mitral annular diameter (30 +/- 2.1 mm preinsertion vs. 24 +/- 1.7 mm postinsertion; P < 0.03). These preliminary experiments demonstrate that percutaneous mitral annuloplasty is feasible. Further study is necessary to demonstrate long-term safety and efficacy of this novel approach.

Improvement in right ventricular systolic function after surgical correction of isolated tricuspid regurgitation

Chronic tricuspid regurgitation (TR) may lead to impairment in right ventricular (RV) function. Whether surgical correction results in restoration of normal RV geometry and function is unknown. The purpose of this study was to determine whether surgical correction of TR results in improved RV geometry and function. Measurements of RV areas were made from digitized 4-chamber echocardiographic views. Right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV), and ejection fraction (EF) were calculated with the single-plane subtraction method. There was a significant decrease in RVEDV (109.06 +/- 12.45 versus 71.63 +/- 6. 83; P =.005) and RVESV (76.2 +/- 9.83 versus 44.5 +/- 5.58; P =.002) and a significant increase in RVEF (0.30 +/- 0.05 versus 0.38 +/- 0. 05; P =.01) at a mean follow-up of 130 +/- 63 days after surgery. These results demonstrate significant remodeling of the right ventricle with reduction in size and improved EF after tricuspid valve surgery.

Mitral Regurgitation

Chronic severe mitral regurgitation is a surgically correctable disorder. Advances in cardiac surgery (including mitral valve repair and less invasive operations), a low postoperative complication rate, and improved long-term prognosis have reduced the threshold for surgical referral. Choosing the optimal timing for surgery remains the cardinal problem. Clinical and diagnostic imaging information is essential to the detection of occult myocardial decompensation, for which surgical correction should be sought. Surgery is not generally recommended in asymptomatic patients without signs of progressive disease. The final decision regarding timing of surgery should be made based on all the clinical data, the patient's choice, and the available surgical expertise. The use of medical therapy to delay the time to surgery is not supported by large trials; however, small short-term studies of chronic vasodilator therapy show favorable hemodynamic effects.

[Functional mitral regurgitation. Physiopathology and impact of medical therapy and surgical techniques for left ventricle reduction]

Functional mitral regurgitation is frequently observed in the setting of left ventricular dyfunction. This finding is a marker of poor outcome in patients with either ischemic or dilated cardiomyopathy. The mechanism accounting for this phenomenon is an altered balance of tethering versus coapting forces acting on the mitral valves in the failing heart. Tethering forces represent an anomalous tension on the mitral valves due to displacement of mitral valve attachments secondary to increased left ventricular chamber sphericity associated with systolic ventricular dysfunction. On the other hand, coapting forces are weak and unable to counteract the abnormal tension acting on the mitral valve, which restricts closure and leads to regurgitation. Vasodilators and inotropic drugs are effective in the management of functional mitral regurgitation. Although partial left ventriculectomy or Batista's procedure is still investigational, this new technique seems to provide an optimal control of functional mitral regurgitation and improve functional capacity and survival of some patients with heart failure.