Echocardiography in mitral valve disease: A review

Summary Echocardiographic evaluation of the mitral valve has attracted much attention and generated much discussion since its beginnings, some thirty years ago. Echocardiography affords the physician a detailed assessment of mitral valve integrity unequalled by any other non-invasive test. Aside from the normal appearance of the valve, a variety of pathological conditions have been studied in detail; mitral stenosis was the first and over the years the state-of-the-art has evolved from simply looking at the EF slope as an indicator of severity to the accurate quantification utilizing planimetry and pressure half-time. Mitral regurgitation, although not as well quantified as mitral stenosis, can be detected and its etiology usually determined. Mitral valve prolapse may easily be overdiagnosed by echocardiography, however together with auscultation, ultrasound remains the best way to evaluate this common condition. Echocardiography is also invaluable in the evaluation of endocarditis and prosthetic mitral valves.     

Echocardiography of the mitral valve

Mitral valve disease is the second most common valvular heart disease after the aortic valve worldwide. Mitral valve has historically been a structure of interest by pioneers in echocardiography. One of the earliest applications of echocardiography was in the diagnosis of valvular heart disease, particularly mitral stenosis. In this review we wish to take the reader through the structural and hemodynamic evaluation of the normal mitral valve.     

Natural history of aortic and mitral valve disease

An appreciation of the natural history of acquired valvular heart disease is a prerequisite to an understanding of how surgical intervention has altered the natural outlook. The prognosis for a patient with valvular heart disease treated medically is dependent on the stage of the disease at which he is first seen. Therefore, assessment for surgery requires evaluation of the pathophysiologic consequences that have resulted from the hemodynamic alterations. Survival statistics for patients seen at the University of California Medical Center at San Francisco are presented and compared with the data of others. Stenotic lesions appear to have a poorer prognosis than chronic regurgitant lesions and generally warrant surgical intervention at an earlier functional stage of the disease. However, valvular insufficiency produced acutely is poorly tolerated and may constitute a surgical emergency.     

Echocardiography in the management of mitral valve prolapse

Echocardiography plays a major role in the management of patients with mitral valve prolapse (MVP). The technique has greatly enhanced our understanding of the pathophysiology, epidemiology and natural history. There are major and minor echocardiographic diagnostic criteria for prolapse. Major criteria involve the mitral leaflets and include late systolic posterior displacement on M-mode, bulging into the left atrium on 2D long-axis (LAX) view, and thickening and redundancy of the leaflets. Minor criteria include holosystolic posterior prolapse on M-mode, bowing of the mitral leaflets into the left atrium (LA) in the apical 2D views, and late systolic mitral regurgitation on the Doppler echogram. Any of the major criteria should be sufficient to make the diagnosis. One or two minor criteria without a major sign would be questionable. The degree of thickening and redundancy and the presence and quantitation of mitral regurgitation influence prognosis. Echocardiography is also helpful in identifying complications such as endocarditis and ruptured chordae. An echocardiogram may not be necessary for the diagnosis, but it is helpful for prognosis and as a baseline for possible future changes. The frequency of follow-up echocardiograms should be determined by clinical findings. When mitral regurgitation is present, then one should follow LA and left ventricular size and function. Transoesophageal echocardiography may be desirable for better definition of vegetations or flail leaflets and is frequently used to monitor surgical repair.     

Congenital aortic valve disease with rupture of mitral chordae tendineae.

A new clinical entity is described in which free aortic regurgitation from congenital aortic valve disease caused rupture of the chordae to the anterior leaflet of the mitral valve in 7 men aged 45 to 63 years (mean 52 years); 2 of the patients also had rupture of chordae to the posterior leaflet. Comparing these patients with those with ruptured mitral chordae in association with rheumatic heart disease and patients with spontaneous chordal rupture, differences were evident. No patient had a history of rheumatic fever and none had active infection. The typical clinical presentation was of acute mitral regurgitation into a small left atrium, with severe pulmonary oedema which was often resistant to medical treatment. The cause of chordal rupture in these patients was in part the result of progressive left ventricular dilatation, of direct trauma to the anterior cusp of the mitral valve, and possibly of a genetic factor. The anatomical features of both aortic and mitral valves are described, and in 3 histology of the mitral valve was available; 2 had myxomatous degeneration similar to that seen in patients with spontaneous chordal rupture, and in 1 there was degeneration of collagen tissue. All patients were treated surgically but the mortality was high (5 out of 7,70%). Early operation with replacement of the aortic and mitral valves is recommended if this high mortality is to be reduced.     

Echocardiography quantification of mitral valve defects

Echocardiography led during the last 10 years to a definite improvement of quality of cardiological diagnostics. In addition to an excellent recording of morphological and functional changes of the heart by 1- and two-dimensional images Doppler-echocardiography allows the semiquantitative judgement of the hemodynamic effect. Echocardiographic techniques try to measure the mitral valve area in cases of mitral stenosis resp. the leak area in cases of mitral insufficiency to assess the importance of valve disorder. These parameters are constant values, whereas the transmitral diastolic pressure gradient and the regurgitant volume are variable. The assessment of the mitral valve area and the graduation of the mitral valve stenosis is possible with a high diagnostic relevance using planimetrical and/or pressure-half-time methods. The applicability of the pressure-half-time method depends on the nature of the pressure decrease and an individual review is necessary. The measurement of the leak area is much more problematical. The assessment of the functional regurgitation area by colour coded Doppler-echocardiography seems to be favourite, but not validated up to now. A semiquantitative judgement of a mitral valve insufficiency is successful in evaluating of intensity, width and area of the regurgitant cloud. The evaluation of raw data of flow patterns will provide further information in future.     

Advances in the percutaneous treatment of aortic and mitral valve disease

The healthcare burden of valvular heart disease continues to increase as our population ages. Because of advances in operative techniques and cardiac anesthesiology, surgery has excellent safety and durability for many patients, and surgery remains the gold standard for treating valvular heart disease. Because many patients have comorbidities that increase operative risk, interest in catheter-based valve repair and replacement has grown. Early human experience with aortic stent-valve prostheses has been quite encouraging. For mitral regurgitation, percutaneous annuloplasty and leaflet repair are being developed by numerous companies, and early human studies have demonstrated feasibility of percutaneous repair. Continuing advances in technology and experience promise to expand the role of percutaneous repair and replacement in the treatment of valvular heart disease. Ongoing trials will help define long-term durability and safety, along with appropriate patient selection for percutaneous treatment.     

The natural history of aortic valve disease after mitral valve surgery

OBJECTIVES

The present study evaluates the long-term course of aortic valve disease and the need for aortic valve surgery in patients with rheumatic mitral valve disease who underwent mitral valve surgery.

BACKGROUND

Little is known about the natural history of aortic valve disease in patients undergoing mitral valve surgery for rheumatic mitral valve disease. In addition there is no firm policy regarding the appropriate treatment of mild aortic valve disease while replacing the mitral valve.

METHODS

One-hundred thirty-one patients (44 male, 87 female; mean age 61 ± 13 yr, range 35 to 89) were followed after mitral valve surgery for a mean period of 13 ± 7 years. All patients had rheumatic heart disease. Aortic valve function was assessed preoperatively by cardiac catheterization and during follow-up by transthoracic echocardiography.

RESULTS

At the time of mitral valve surgery, 59 patients (45%) had mild aortic valve disease: 7 (5%) aortic stenosis (AS), 58 (44%) aortic regurgitation (AR). At the end of follow-up, 96 patients (73%) had aortic valve disease: 33 AS (mild or moderate except in two cases) and 90 AR (mild or moderate except in one case). Among patients without aortic valve disease at the time of the mitral valve surgery, only three patients developed significant aortic valve disease after 25 years of follow-up procedures. Disease progression was noted in three of the seven patients with AS (2 to severe) and in six of the fifty eight with AR (1 to severe). Fifty two (90%) with mild AR remained stable after a mean follow-up period of 16 years. In only three patients (2%) the aortic valve disease progressed significantly after 9, 17 and 22 years. In only six patients of the entire cohort (5%), aortic valve replacement was needed after a mean period of 21 years (range 15 to 33). In four of them the primary indication for the second surgery was dysfunction of the prosthetic mitral valve.

CONCLUSIONS

Our findings indicate that, among patients with rheumatic heart disease, a considerable number of patients have mild aortic valve disease at the time of mitral valve surgery. Yet most do not progress to severe disease, and aortic valve replacement is rarely needed after a long follow-up period. Thus, prophylactic valve replacement is not indicated in these cases.     

Abnormal aortic valve echoes in mitral prolapse. Echocardiographic features of floppy aortic valve.

The following distinctive combination of M-mode and two dimensional echocardiographic abnormalities of the aortic valve was observed in a group of 12 patients, of whom 11 had mitral valve prolapse. On two dimensional scans, the aortic cusps were freely mobile but appeared thickened or folded. On M-mode records, cusp excursion was normal: there was well defined systolic oscillation, and cusp echoes were multiple and centrally positioned within the aortic root during diastole. The aortic valve was inspected at operation in two patients: a typically myxomatous valve was replaced in one and findings were in keeping with this diagnosis in the other. It is suggested that the echocardiographic features described are characteristic of the floppy aortic valve. Despite the echocardiographic abnormalities, only three patients had clinical evidence of an aortic valve lesion. It is, therefore, further suggested that the investigation of patients with mitral prolapse should include echocardiographic assessment of the aortic valve, even when associated myxomatous degeneration of that valve is not suspected clinically.     

Relation of angina to coronary artery disease in mitral and in aortic valve disease.

Of 129 patients with either mitral or aortic valve disease angina was present in 55 (42%). It was more frequent in aortic (60%) than in mitral valve disease (33%). The standard 12-lead electrocardiogram was not helpful in distinguishing underlying occlusive coronary artery disease. Coronary arteriography demonstrated coronary artery disease in 26 patients (20%), only 2 of whom had no angina. The incidence of coronary artery disease was almost identical in both the mitral and aortic groups (22% and 17%, respectively), but the percentage of those with demonstrable coronary artery disease accompanying angina was much higher in the mitral group (67% as against 29%). Angina in mitral valve disorders is thus much more likely to be the result of disease of the coronary arteries. Coronary arteriography is mandatory in all patients in both groups who have angina. Otherwise it seems unnecessary as coronary artery disease was found in only 2 patients who did not have angina.     

Evaluation of posterior aortic wall echogram in diagnosis of mitral valve disease.

The clinical usefulness of detecting abnormal movement of the posterior wall of the aortic root by M-mode echocardiography was studied in 93 patients with common cardiac diseases (mitral and aortic valve disease, atrial septal defect, hypertrophic and congestive cardiomyopathy) and in 17 normal subjects. Though abnormally slow (less than 3 cm/s) or prolonged (greater than 240 ms) diastolic movement was confirmed to be common in mitral stenosis, since it occurred in 35 of 36 patients it was non-specific. Similar abnormalities frequently occurred in other patients with, for example, mitral regurgitation, aortic valve disease, after aortic valve replacement, and in both hypertrophic and congestive cardiomyopathy. The severity of mitral stenosis, assessed at operation, could not be accurately predicted from abnormalities of aortic root movement. Information derived from aortic movement was not diagnostic and did not predict severity in isolated mitral regurgitation though both the peak rate of systolic aortic motion and total aortic excursion were significantly greater than normal. We conclude that abnormalities of posterior aortic wall movement are frequent and their specificity and clinical usefulness are limited.