1, Chronic mitral valve insufficiency pathophysiology
The main pathophysiological change in mitral insufficiency is mitral regurgitation, which increases the left atrial load and the diastolic load of the left ventricle. During left ventricular systole, blood flows from the left ventricle into the aorta and through the insufficiently closed mitral valve into the less resistant left atrium, and the regurgitant flow into the left atrium can reach more than 50% of the left ventricular blood volume. The increase in left atrial pressure can cause an increase in pulmonary vein and swollen capillary pressure, followed by dilation and stasis. At the same time, the diastolic volume load of the left ventricle increases and the left ventricle enlarges. Pulmonary hypertension and total heart failure may occur in the late stages of mitral valve insufficiency. However, the typical patient with chronic mitral valve insufficiency has mild symptoms and a slow progression, and once the disease worsens the prognosis is unpredictable.
All pathophysiologic changes will result in an enlarged heart with increasing leaflet regurgitation. In some patients with severe mitral insufficiency, although the regurgitant flow is high, the patient may have only mild clinical symptoms or even no clinical symptoms and left ventricular insufficiency, i.e., the EF is still within the normal range, because of compensatory mechanisms or because the patient has adapted to the regurgitation itself. In any case, however, mitral insufficiency is a progressive disease with regurgitant flow increasing by an average of 7.5 ml per year.
2. Early surgical treatment of mitral valve insufficiency
(1) The need for early surgery
The main pathological changes of mitral valve insufficiency are caused by left ventricular overload, left ventricular enlargement and functional impairment, and less accompanied by pulmonary circulation back into the left heart obstruction, only in the late stage of left heart function is obvious, the left atrium secondary dilatation after the performance of pulmonary stasis and produce activity palpitations, chest tightness and other clinical symptoms of decreased activity tolerance. Most patients with mitral valve insufficiency have severe left heart function impairment by the time clinical symptoms are evident, which adversely affects the efficacy of near- and long-term cardiac surgery, especially the implementation of repair surgery.
In asymptomatic patients, early surgical treatment is the preferred approach. Patients who are clearly asymptomatic and have normal left ventricular size and function should be followed up with prophylactic surgery when a preoperative assessment of repair success is expected to be >90%. Some senior mitral valve repair centers have demonstrated that surgical treatment of asymptomatic cases of severe mitral valve insufficiency provides the best near-term and long-term results with a surgical risk of <1% and a success rate of >80% for valve repair, and they highlight the importance of early determination and assessment of mitral regurgitation.
Current surgical treatments for mitral valve insufficiency are divided into three categories.
(1) mitral valvuloplasty.
(2) mitral valve replacement with preservation of the annulus.
(3) mitral valve replacement without preservation of the annulus.
Choice of surgical approach.
For early surgery, mitral valvuloplasty repair has more definite benefits than valve replacement because valve replacement often results in higher postoperative mortality, whereas valvuloplasty repair has lower postoperative risk, longer survival, and reduced likelihood of recurrent heart failure and stroke. Early valve repair is a priority in degenerative mitral valve insufficiency with mitral valve prolapse.
Mitral valvuloplasty has the following advantages.
(1) Avoidance of long-term anticoagulation.
(2) Reduces the risk of bacterial endocarditis;
(3) Preservation of left heart function by preserving the valvular apparatus;
(4) Avoidance of complications associated with valve replacement, such as hemolysis, thrombosis, and embolism;
(5) Avoidance of bioprosthetic valve failure.
(6) Economic cost savings.
Although mitral valvuloplasty is an effective treatment, the indications for mitral valvuloplasty involve various factors such as the degree of pathologic changes in the diseased valve, etiology, and functional status of the heart.
(1) Extensive fibrosis and calcification of all mitral valve structures, severe fusion of subvalvular structures, and severe smoldering lesions of the anterior mitral leaflet that have resulted in severely restricted mobility and reduced size.
(2) A history of previous mitral valve surgery.
(3) Severe pathologic changes in the mitral valve structures of more than 50% and other valves requiring prosthetic valve replacement in the heart.
(4) Preoperative severe left ventricular function impairment or complex cardiac malformation, mitral valvuloplasty cannot be completed within a short period of time, which may result in significantly prolonged extracorporeal circulation and cardiac arrest time.
(5) The operator is unable to determine the method of mitral valvuloplasty repair and the immediate intraoperative results based on his or her own experience, and has doubts about long-term hemodynamic stability.
In addition, the decision to perform surgery should be based on a combination of.
(1) Echocardiography. Good use of echocardiography to assess mitral valve function and lesions, appropriate timing of surgery, and proper application of surgical techniques are all interrelated. The predicted accuracy for highly probable mitral valvuloplasty is approximately 95.8%, the predicted value for probable valvuloplasty is approximately 83%, and the predicted value for difficult valvuloplasty due to poor valve texture is 93%. (2) Intraoperative mitral valve surgery
(2) Intraoperative exposure and exploration of the mitral valve. Good intraoperative exposure and exploration of the mitral valve is also an important prerequisite for determining the indication for valvuloplasty and for using the correct repair technique to complete the procedure, but is often overlooked by some operators; intraoperative exploration of mitral valve lesions should be organized, which is very useful for determining the indication for surgery and for selecting the repair method.
(3) The surgeon’s knowledge of mitral valve structure and function, the indications and timing of surgery, the choice of surgical approach, and surgical technique may all affect the outcome of valvuloplasty. Mitral valve surgery has been performed on a large number of patients worldwide, but the results achieved are not identical.
Timing of surgery: When treating patients with mitral valve insufficiency, cardiovascular surgeons are often faced with two questions.
(1) To what extent does mitral valve insufficiency cause clinical symptoms or left ventricular insufficiency that requires clinical treatment.
(2) The timing and approach of mitral insufficiency treatment [15]. The timing of surgical treatment for patients with severe mitral valve insufficiency is a complex and controversial issue. Physicians need to consider many issues when making surgical decisions and continually evaluate a number of indicators, including the patient’s symptoms, severity of regurgitation, the impact of hemodynamic changes on the left atrium, right and left ventricles, the feasibility of surgery, and the risks of surgery.
Cardiologists must pay attention to the issue of timing of surgical treatment of asymptomatic severe mitral valve insufficiency so that patients can choose surgery at the most appropriate fit and obtain a high-quality prognosis. There are clinical data [26] that suggest that surgical interventions for the disease process, one of the issues that clinicians must consider i.e. in contrast to the natural course of disease development, can improve overall survival and quality of life. Thus, since the last decade, many retrospective clinical trials have provided data on the timing criteria of surgery for asymptomatic severe mitral valve closure regurgitation and the outcome of benefit for patients under this criterion.
Patients with asymptomatic severe mitral valve closure insufficiency are considered for surgery when they present with.
(1) Mild to moderate left ventricular insufficiency (left ventricular EF 30-60%, and/or end-systolic internal diameter ≥40 mm).
(2) Fairly good left ventricular function (EF > 60% and left ventricular end-systolic volume < 40 mm) with > 90% chance of successful surgical repair without residual reflux can be treated surgically with MV in an experienced surgical center.
(3) Normal left ventricular function with new-onset atrial fibrillation.
(4) Normal left ventricular function and pulmonary hypertension.
This guideline also suggests that asymptomatic patients with severe mitral valve closure insufficiency with fair left ventricular function (EF ≥ 60% and left ventricular end-systolic volume < 40 mm) and significant doubts about the feasibility of valve repair are not candidates for surgery. At the same time, patients with mild or toxic mitral valve insufficiency are also not candidates for surgery. It is emphasized here that the issue of valve repairability is critical to the suitability of surgery, and it is only when the patient is suitable for surgical treatment and the valve is repairable that it becomes important to consider when to repair the valve. Moreover, specific measurements of left ventricular insufficiency are given to facilitate clinicians' reference in practice. Thus, when considering the timing of surgery in patients, our main references include clinical symptoms, ejection fraction, left ventricular size, arrhythmias, pulmonary hypertension, ERO regurgitation area, left atrial size, and age, among other indicators.