The only effective management for MR is its mechanical correction. There is no evidence from large trials to support the use of afterload reducing agents to treat chronic MR, and most of the data that do exist are disappointing.
Conversely, patients with hypertension should receive standard therapy for that condition. Mild to moderate MR is usually tolerated indefinitely as long as it does not worsen. However, because MR causes ventricular enlargement, in turn placing additional stress on the valve, MR tends to cause worsening of MR. These triggers are demarcations in the disease which, if left unattended, lead to worsened prognosis and include: the onset of symptoms, evidence of LV dysfunction, and evidence of pulmonary hypertension.
This suggests that these benchmarks are a sign that LV dysfunction has ensued. If the patient is seen for the first time when symptoms or LV dysfunction have occurred, a short course months of standard heart failure therapy that includes the administration of ACE inhibitors and beta blockers is probably advisable before proceeding to mitral valve surgery.
However, even if the patient improves clinically after this therapy, the indications for surgery have been met and there is no evidence that surgery should be delayed any further. The mitral valve is an integral part of the LV; the mitral apparatus aids in LV contraction and helps maintain the efficient prolate ellipsoid shape of the LV.
Destruction of the mitral valve apparatus and concomitant mitral valve replacement cause increased operative mortality, poorer postoperative LV function, and decreased postoperative survival when compared with mitral valve repair. Thus, in the treatment of MR, when possible, the mitral valve should be conserved and repaired instead of replaced.
Reparability depends upon valve pathology and surgical skill. In general, rheumatic valves are difficult to repair and the durability of the repair is undependable.
Simple posterior leaflet prolapse is the easiest to repair and most durable; bileaflet myxomatous disease is in the middle between the two. It must be noted that surgical expertise varies widely, with some surgeons able to repair most non-rheumatic MR, while others have never performed a mitral valve repair. However some valves ultimately will require replacement.
Preservation of the natural connections between the native valve and the papillary muscles can be maintained even when the valve is replaced, and this procedure helps preserve LV function. In cases of severe MR where the anatomy is consistent with almost certain valve repair, many would argue for early surgery before symptoms or evidence of LV dysfunction develop. This strategy only works if a successful repair is carried out. If an unwanted mitral valve replacement ensues, with its higher risk of both operative mortality and long-term prosthetic valve complications, the strategy fails.
Many providers remain unaware of the nuances of therapy. Common mistakes in management include:. Treating symptoms medically. Despite evidence that the presence of even mild symptoms worsens prognosis, many providers add diuretics or other therapies to improve symptoms. However, there is no evidence that medical therapy improves prognosis even if symptoms improve. In some cases, it is entirely obvious that the patient has severe MR from all aspects of the clinical presentation.
However, in other cases visualizing, only the MR jet at color-flow Doppler examination may overestimate or underestimate MR severity because all the clues available are not considered. Under-appreciation of the importance of mitral repair. Many practitioners are willing to accept mitral replacement when repair could be performed by surgeons more skilled in the technique. As noted above, the only effective management of MR is mechanical correction.
However, very elderly patients or those with advanced liver, lung or renal disease may be at unacceptable risk for mitral surgery. Recently, experimental approaches using transcatheter, percutaneous, or transapical methods for mitral repair or replacement have been attempted. One, the MitraClip, is now approved in the United States for mitral repair in inoperable patients with severe primary symptomatic MR.
The technique employs trans-septal deployment of a device that clips the midportions of the two mitral leaflets together, reducing MR from severe to moderate or mild in most cases.
The technique is less effective than surgery in eliminating MR but safer in this group of patients and has provided excellent relief of symptoms for up to 5 years. While currently the indications for use are limited as described above, in Europe it is most often used to treat secondary MR and trials for that use are currently underway in the United States. Carabello, BA. Part Mod Concepts Cardiovasc Dis. Summarizes the pathophysiology of MR.
J Am Coll Cardiol. Demonstrates that diastolic function in MR is super-normal. Dispels the misconception that MR unloads the LV. Demonstrates the importance of the mitral apparatus in aiding LV function. J Thorac Cardiovasc Surg. Demonstrates the risks of pulmonary hypertension in MR. Cements LV systolic dimension as a predictor of outcome in MR.
Ann Thorac Surg. Shows that even mild preoperative symptoms in MR effect post-operative outcome negatively. Demonstrates the survival benefit of mitral repair compared to replacement. Reveals the importance of repair volume in predicting the likelihood of a successful repair.
All rights reserved. Gaasch WH. Pathophysiology of chronic mitral regurgitation. In: Post TW, ed. Last updated: December 30, Accessed: February 27, Karen K. Stout, Edward D. Acute Valvular Regurgitation. Acute mitral regurgitation. Left Ventricular Response to Mitral Regurgitation. Curr Probl Cardiol. Atrial Fibrillation and Mitral Valve Prolapse. Cardiovascular Physiology Concepts.
Cardiovascular Imaging by Ultrasound. Primary Care, Second Edition. Pulmonary Hypertension in Mitral Regurgitation. J Am Heart Assoc. A Practical Approach to Cardiac Anesthesia. The right ventricle in pulmonary arterial hypertension. European Respiratory Review. Diagnosis and Treatment in Internal Medicine. Thoracic Imaging: Pulmonary and Cardiovascular Radiology. Circ Cardiovasc Imaging. Mitral valve repair versus replacement..
Ann Cardiothorac Surg. Recent Progress in Mitral Valve Disease. Elsevier ; Islam MS. Clinical presentation, diagnosis and management of acute mitral regurgitation following acute myocardial infarction.
J Acute Dis. The net effect of these changes is that the width of the pressure-volume loop is increased i. The increased ventricular "stroke volume" measured as the end-diastolic minus the end-systolic volume in this case includes the volume of blood ejected into the aorta as well as the volume ejected back into the left atrium. The changes just described do not include cardiac and systemic compensatory mechanisms e. Therefore, the red loop depicted in the figure only represents what may occur under a given set of conditions.
Cardiovascular Physiology Concepts Richard E. Klabunde, PhD.
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