Valvular Heart Disease - Mitral Regurgitation

When the mitral valve is not closed properly, blood can seep back into the heart, a condition known as mitral valve regurgitation. It may be secondary or primary. A structural abnormality in the leaflet or papillary muscles is the major cause of mitral regurgitation. 

Mitral regurgitation resulting from an underlying issue other than a damaged mitral valve is referred to as a secondary cause. Both acute and chronic regurgitation can be symptoms of MR.

Causes Of Mitral Regurgitation

Degenerative Causes

• Primary causes since valves are the source of the issue. 
• Mitral valve prolapse is caused by Barlow's disease (myxomatous degeneration). 
• The annulus or leaflets' calculation.
• Regurgitation results from the valves in Marfan's syndrome becoming redundant due to improper closure.
  o Danlos syndrome of Ehrler.

Ventricular Causes

• Ischemic papillary necrosis and rupture, which result in myocardial infarction, can produce MR. 
• Dilated Cardiomyopathy: MR results from dilated ventricles, which dilate the annulus.

Autoimmune and Infected Diseases

The leaflets rip and perforate as a result of infectious endocarditis. The chordae tendineae rupturing. Valve calcification and fibrosis brought on by rheumatic fever causes the valves to retract and shut improperly, which results in MR.

Other Causes

• Trauma 
• Congenital defect - Isolated mitral cleft
• Medications like ergotamine 
• Radiotherapy

Carpentier’s Classification

• It is based on the degree of the movement of leaflets.

Causes Of Acute Mitral Regurgitation 

• Infective endocarditis, ischemic papillary muscle rupture, acute rheumatic fever

Pathophysiology

During systole, the left ventricle expels blood into the left atrium, resulting in an abrupt volume of load into the left atrium (LA). This quick increase in LA pressure can cause pulmonary congestion and backward pressure.

Causes Of Chronic Mitral Regurgitation

It proceeds slowly, so slow ejection of blood from LV to LA causes slow dilatation of the LA. It causes myxomatous degeneration, calcification, fibroelastic alterations in leaflets, and dilated cardiomyopathy.
As such, the pulmonary circulation is shielded and there won't be a rise in pressure in the LA. 

In long-term illnesses, the left ventricle (LV) expels more blood, which raises the pressure inside the LV and results in compensatory LV dilatation and hypertrophy. As the illness progresses, the pulmonary veins experience back pressure due to an increase in LA pressure, which leads to pulmonary congestion, edema, and CCF.

Also Read: Development of Heart Tube

Clinical Features Of Mitral Regurgitation

Acute MR: The patient will have dyspnea and abrupt lung congestion. A loud pansystolic murmur at the apex. 

Minimal Chronic MR: Without symptoms, progressive pulmonary congestion due to left ventricular failure will induce cough, orthopnea, and dyspnea when the patient exerts themselves. Atrial fibrillation is brought on by LA dilatation.
Experiencing an impulse due to left ventricular hypertrophy. Systolic murmur of pan.

Investigations

• Mitrale ECG-P: Bifid P waves, Signs of atrial fibrillation and left ventricular hypertrophy (LVH).
• Cardiomegaly with significant pulmonary vasculature on the chest X-ray. The degree and severity of regurgitation, the anatomy and morphology of the valves, and the reasons are all indicated by the echo with color flow doppler.
• For individuals over 40, coronary angiography ought to be the preferred procedure.
• A cardiac MRI displays the volume of regurgitation as well as the composition and operation of the valves.
• When valvular disorders such as regurgitant kinds occur, cardiac MRI is recommended.

Management Of MR

Medical Treatment

Vasodilators decrease systemic vascular resistance, which promotes forward flow and decreases regurgitant volume.

Indications of Surgery

• Present symptoms or none at all 
• Primary or secondary MR?  LV end systolic dimension 
• LV ejection fraction 
• The use of supporting frameworks 
• Primary MR: Symptomatic - NYHA II, III, IV with severe MR and LVEF greater than thirty percent
• Asymptomatic - Severe MR with preserved LV function (LVEF - >60%) + LVESD <40 mm with progressive decline in LV function and rise in LV size II a; • Severe MR with LV dysfunction (LVEF -30–60%) and/or LVESD >40 mm-II 
• Secondary MR • Despite a prescription, secondary severe MR exhibiting NYHA class III/IV symptoms
• Severe MR with concurrent CABG: Repairing the mitral valve is one option. 
•  MV substitution

Mitral Valve Repair

For myxomatous degenerative MR, the mitral valve is repaired when the pathology is restricted to the posterior leaflet.

Benefits

Prolonged anticoagulation reduces the risk of bleeding problems; avoid it. Prevents issues linked to valves. Ventricular function is preserved more effectively. After five years, the regurgitation recurrence rate is 30%.

Methodology

 Mini mitral surgery, or median sternotomy and right thoracotomy, is the preferred procedure. The approach can go straight through the interatrial groove and the LA. From the septum to the LA through RA. Appendages from LA. Prosthetic ring annuloplasty, which reduces the ring's size to stop regurgitation, can be used to repair it.

Mitral Valve Replacement

Patients who are not candidates for repair may benefit from replacement of the mitral valve (calcified valve). Papillary muscle rupture (ischemic MR).MS+MR * Approach - Medial sternotomy . CPB will be administered to the patient. Access is via LA.  Remove any diseased valves and install mechanical or bioprosthetic valves in their stead. The subvalvular apparatus (chordae tendineae) is preserved. Death toll: less than 5%.

Prosthetic Valves

Prosthetic valves can be mechanical or bioprosthetic valves. 

Mechanical Valves

It may replace any valve and be used at any age. Sturdy
drawback: Patients are more vulnerable to thrombosis and thromboembolism due to thrombogenic reactions in the body. As a result, individuals will need systemic anticoagulant medication for the rest of their lives. Use with caution in older patients, pregnant or lactating women, patients requiring additional major surgery, and those with bleeding diathesis.

Bioprosthetic (Biological Valves)

Allograft or homograft cadaveric valves, Autograft, Heterograft/xenograft valves: Frequently employed, these are derived from porcine or cow tissue. Valves that are stented or not. Rapid deployment valves require only three sutures, not numerous sutures, making them preferred in individuals over 60 who do not require long-term anticoagulation. 

Suture-free valves secured in place by an inflatable balloon stent.
Extremely helpful for minimally invasive operations, high-risk patients, and elderly patients.

Also Read: Aortic Stenosis- Causes, Clinical Features And Treatment

Complications Of Prosthetic Valves

1. Structural valve failure
   • Uncommon with mechanical valves
2. Paravalvular leaks
   • Early: Difficult insertion
   • Late: Degeneration/ Endocarditis
   • Haemolytic anemia + Hemodynamic compromise
   • Rx: Valve Replacement
3. Thrombosis + Thromboembolism
   • Mechanical valve MC complication: Risk: 0.5–3%/year Technical difficulties during insertion can result in an early paravalvular leak.  Endocarditis or valve degeneration are the main causes of late paravalvular leakage.

Also Read: Rapid Acquisition Of Key Concepts- Cardiothoracic And Vascular Surgery

Post-operative Management

Anticoagulation should be initiated the first or second postoperative day. Aspirin and warfarin are included in the DOC. Patients having bioprosthetic valves and level IIa evidence should get anticoagulant therapy for a duration of three to six months. Depending on the valve (aortic valve: 2.5, mitral valve: 3), INR varies. Rivaroxaban and Apixaban are not recommended.

Mitraclip

The process involves little invasiveness. Object/suture the pamphlets is the principle. The sutures' sides continue to open the valves. The right atrium can be accessed by the femoral vein, while the left atrium can be accessed through the septum. The technique is less intrusive and results in an early recovery. The long-term outcomes are still unknown.
In patients at high risk, such as CCF, prefer it.

Also Read: Knowing Venous Diseases and How to Treat Them

Hope you found this blog helpful for your Cardiothoracic and Vascular Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.