Medicine Short Cases

My most likely diagnosis is Mitral Regurgitation (MR), complicated by Atrial Fibrillation (AF).

Key features supporting the diagnosis:

• Pan-systolic murmur at the apex, radiating to the axilla: This is the classical presentation of a mitral regurgitation murmur.
• Thrusting and displaced apex beat: A thrusting and displaced apex beat is characteristic of left ventricular volume overload, which occurs in MR.
• Irregularly irregular pulse: This suggests atrial fibrillation, a common complication of chronic MR due to left atrial dilatation.
• Soft S1: A soft S1 can be heard in MR due to incomplete closure of the mitral valve.

Differentiating MR from other pan-systolic murmurs like VSD, and other conditions that can cause a systolic murmur, is crucial for accurate diagnosis.

Differentiating Mitral Regurgitation from Ventricular Septal Defect (VSD):

Both MR and VSD can cause a pan-systolic murmur, but key differentiating features on examination include:

• Location and Radiation of Murmur:
  • MR: Best heard at the apex and classically radiates to the axilla. If the posterior leaflet is predominantly involved (e.g., Mitral Valve Prolapse or papillary muscle dysfunction), the murmur may radiate to the left sternal edge.
  • VSD: Best heard at the lower left sternal edge and usually does not radiate to the axilla.
• Apex Beat:
  • MR: Typically a displaced and thrusting apex due to left ventricular volume overload.
  • VSD: A non-displaced apex is common, though a displaced apex can be seen in large defects.
• Thrills:
  • MR: A systolic thrill at the apex may be palpable.
  • VSD: A systolic thrill is typically palpable at the lower left sternal edge.
• Severity of Murmur: For VSD, a louder murmur generally indicates a smaller defect, while a softer murmur suggests a larger, more significant defect often accompanied by signs of pulmonary hypertension. This correlation is less direct in MR.

Differentiating from other systolic murmurs:

Other systolic murmurs include Ejection Systolic Murmurs (e.g., Aortic Stenosis, Pulmonary Stenosis) and other flow murmurs.

• Timing: MR is pan-systolic (heard throughout systole), while AS and PS are ejection systolic (heard after S1 and ending before S2).
• Heart Sounds: In MR, S1 is typically soft. In AS, S1 is normal and S2 may be soft. In PS, S2 is soft and single.
• Radiation: AS radiates to the carotids, PS typically does not, while MR radiates to the axilla.

The severity of mitral regurgitation is assessed clinically by evaluating the intensity of the associated signs and symptoms. While echocardiography provides definitive quantitative assessment, clinical signs are important for initial assessment.

Clinical indicators of severe MR include:

• Prominent and Displaced Thrusting Apex: Indicates significant left ventricular volume overload.
• Soft S1: Suggests significant regurgitation leading to incomplete valve closure.
• Presence of S3: Indicates increased left ventricular filling pressure and volume, a sign of severe MR.
• Palpable Precordial Thrill: A more intense murmur often correlates with a palpable thrill at the apex.
• Signs of Pulmonary Edema: Such as bibasal crepitations, dyspnoea, orthopnoea, and paroxysmal nocturnal dyspnoea.
• Signs of Pulmonary Hypertension (PHT): Such as a loud P2 (palpable second heart sound at the pulmonary area), elevated JVP, and right ventricular failure signs (e.g., peripheral oedema, hepatomegaly).
• Associated Atrial Fibrillation: Chronic AF often complicates severe or long-standing MR due to significant left atrial dilatation.

Mitral regurgitation can be acute or chronic, and its causes vary with age and underlying conditions. In an elderly patient, both chronic and some acute causes are relevant.

Possible Causes of Mitral Regurgitation:

• Chronic Causes:
  • Rheumatic Heart Disease: This is a common cause in many parts of the world, leading to leaflet thickening and distortion, chordal shortening, or annular dilatation.
  • Mitral Valve Prolapse (MVP): Degenerative changes leading to prolapse of one or both mitral leaflets into the left atrium during systole. The murmur often radiates to the left sternal edge if the posterior leaflet is primarily involved.
  • Left Ventricular Dilatation: Any condition causing severe left ventricular dilatation (e.g., dilated cardiomyopathy, chronic ischaemic heart disease) can lead to functional MR due to annular dilatation and papillary muscle displacement, even with structurally normal leaflets.
  • Infective Endocarditis (IE): Can cause chronic MR through leaflet destruction or chordal rupture.
  • Connective Tissue Disorders: Such as Marfan syndrome or Ehlers-Danlos syndrome.
• Acute Causes:
  • Acute Myocardial Infarction (MI): Can cause acute MR (discussed below).
  • Rupture of Chordae Tendinae: Can occur spontaneously or due to infective endocarditis.
  • Infective Endocarditis (IE): Rapid destruction of leaflets or rupture of chordae.

How Myocardial Infarction (MI) can cause MR:

A myocardial infarction can lead to acute MR primarily through involvement of the papillary muscles or the ventricular wall itself.

• Papillary Muscle Necrosis or Dysfunction: This is the most common mechanism. The papillary muscles connect the chordae tendinae to the ventricular wall, preventing the mitral valve leaflets from prolapsing into the atrium during systole. Ischaemia or infarction of a papillary muscle can cause:
  • Papillary Muscle Rupture: A catastrophic complication, leading to severe acute MR due to complete loss of support for a portion of the mitral leaflet. This often presents with acute pulmonary oedema and cardiogenic shock.
  • Papillary Muscle Dysfunction: Sublethal ischaemia or infarction can cause the papillary muscle to become hypokinetic or akinetic, leading to incomplete coaptation of the valve leaflets and varying degrees of MR. This is often transient or less severe than rupture.
• Left Ventricular Remodeling/Dilatation: In the subacute or chronic phase after a large MI, significant left ventricular remodelling and dilatation can occur. This changes the geometry of the ventricle, pulling the papillary muscles away from the mitral annulus and causing the leaflets to tent, leading to functional (secondary) MR.

The investigations for a patient with suspected mitral regurgitation aim to confirm the diagnosis, assess its severity, identify the aetiology, evaluate for complications, and guide management decisions.

1. Essential Investigations:

• Echocardiogram (2D and Doppler): This is the gold standard investigation.
  • Confirmation of Diagnosis: Directly visualises the mitral valve and detects regurgitant flow.
  • Assessment of Severity: Quantifies the regurgitant volume and fraction, assesses jet size and density, and helps classify MR as mild, moderate, or severe.
  • Valvular Anatomy: Identifies structural abnormalities (e.g., leaflet prolapse, rupture of chordae, calcification).
  • LV Dimensions and Function: Assesses left ventricular size (dilatation) and systolic function (ejection fraction), which are crucial for prognosis and timing of intervention.
  • Pulmonary Pressure Estimation: Estimates pulmonary artery systolic pressure, indicating the presence and severity of pulmonary hypertension.
• Electrocardiogram (ECG):
  • Atrial Fibrillation (AF): Confirm the presence of AF, if suspected clinically.
  • Left Atrial Hypertrophy/Dilatation: Signs like P-mitrale (broad, bifid P waves).
  • Left Ventricular Hypertrophy (LVH): Due to chronic volume overload.
  • Conduction Abnormalities: May be associated.
  • Signs of Ischaemia/Infarction: If MI is suspected as a cause.
• Chest X-ray (CXR):
  • Cardiomegaly: Often seen due to left ventricular and left atrial enlargement.
  • Left Atrial Dilatation: May manifest as a splayed carina (widening of the tracheal bifurcation) or a double right heart border.
  • Pulmonary Congestion/Pulmonary Edema: Signs like prominent pulmonary vascular markings, interstitial oedema (Kerley B lines) or alveolar oedema.
  • Pulmonary Hypertension (PHT) signs: Enlarged pulmonary arteries.

2. Other Investigations (if indicated by aetiology or complications):

• Full Blood Count (FBC): To assess for anaemia (which can exacerbate symptoms) or signs of infection (e.g., in infective endocarditis).
• Inflammatory Markers (ESR, CRP): If infective endocarditis or an inflammatory/rheumatic cause is suspected.
• Blood Cultures: If infective endocarditis is a possibility.
• Renal and Liver Function Tests: To assess end-organ function, especially if heart failure is present.
• Thyroid Function Tests: To rule out thyroid disease as a cause or exacerbating factor for AF.
• Coronary Angiogram: Especially in older patients or if there is a suspicion of concomitant coronary artery disease (e.g., if MI is a suspected cause of MR). This is crucial before surgical intervention.

The management plan for a patient with mitral regurgitation aims to relieve symptoms, prevent progression of the disease, and manage complications. The approach depends on the severity of MR, the presence of symptoms, and LV function, as well as the aetiology (primary vs. secondary MR).

1. General Principles:

• Patient Education: Explain the condition, the importance of regular follow-up, and warning signs of worsening heart failure.
• Risk Factor Modification: Manage co-morbidities like hypertension, diabetes, and hyperlipidaemia. Lifestyle advice (diet, exercise, smoking cessation).

2. Medical Management:

• Management of Atrial Fibrillation (AF): As the patient has an irregularly irregular pulse suggestive of AF:
  • Rate Control: Beta-blockers (e.g., carvedilol, metoprolol) or non-dihydropyridine calcium channel blockers (e.g., diltiazem, verapamil).
  • Anticoagulation: Assess stroke risk using CHA2DS2-VASc score and initiate oral anticoagulation (Warfarin or NOACs) to prevent thromboembolic complications like stroke.
  • Rhythm Control: May be considered in selected symptomatic patients (e.g., cardioversion, antiarrhythmic drugs), though rate control is often preferred in chronic MR.
• Management of Heart Failure Symptoms (if present):
  • Diuretics: For pulmonary congestion and oedema relief.
  • ACE Inhibitors/ARBs: May be considered, especially if there is associated hypertension or LV dysfunction, to reduce afterload and slow remodelling.
  • Beta-blockers: (As for AF rate control) also important for heart failure management.
• Prophylaxis for Infective Endocarditis: Although routine prophylaxis is not indicated for uncomplicated MR, it is important to ensure good dental hygiene and educate the patient on symptoms of endocarditis.

3. Interventional Management (Mitral Valve Surgery/Repair):

Intervention is considered in patients with severe MR, depending on symptoms and LV function.

• Indications for Intervention:
  • Symptomatic Severe MR: Patients with symptoms (e.g., dyspnoea) despite optimal medical therapy.
  • Asymptomatic Severe MR with Adverse Features:
    • LV systolic dysfunction (ejection fraction < 60%) or progressive LV dilatation (LV end-systolic diameter > 40-45mm).
    • New onset atrial fibrillation.
    • Development of pulmonary hypertension (pulmonary artery systolic pressure > 50 mmHg at rest).
  • Secondary (Functional) MR: The primary emphasis is on optimizing therapy for underlying ischaemic heart disease and heart failure. Surgical repair or replacement is considered if symptoms are refractory to medical management.
• Surgical Options:
  • Mitral Valve Repair (Valvuloplasty): Preferred whenever feasible, as it preserves LV function better than replacement.
  • Mitral Valve Replacement: When repair is not possible.

Chronic mitral regurgitation, especially if severe, can lead to several complications affecting the heart and lungs, impacting the patient’s quality of life and prognosis.

Potential Complications:

• Atrial Fibrillation (AF):
  • Common due to progressive left atrial dilatation caused by chronic volume overload. The irregularly irregular pulse in this patient already suggests AF.
  • AF itself can lead to complications such as:
    • Stroke: Due to thrombus formation in the left atrium and subsequent embolization.
    • Worsening Heart Failure: Loss of atrial kick and rapid ventricular rates can further compromise cardiac output.
• Pulmonary Hypertension (PHT):
  • Chronic increase in left atrial pressure is transmitted to the pulmonary veins and capillaries, leading to pulmonary arterial hypertension.
  • PHT can cause progressive right ventricular strain and eventual failure (cor pulmonale).
• Pulmonary Edema:
  • Episodes of acute or chronic pulmonary congestion can occur due to elevated left atrial and pulmonary venous pressures, leading to dyspnoea, orthopnoea, and paroxysmal nocturnal dyspnoea.
  • Fine crepitations on lung examination would be a key sign of pulmonary oedema.
• Left Ventricular Dysfunction and Heart Failure:
  • Initially, the left ventricle compensates for the volume overload by dilating and hypertrophying. Over time, chronic severe MR can lead to irreversible left ventricular systolic dysfunction, culminating in congestive heart failure.
  • Signs include dyspnoea, fatigue, and peripheral oedema.
• Infective Endocarditis (IE):
  • The abnormal blood flow across the regurgitant valve predisposes to bacterial colonization and infective endocarditis.
  • Symptoms may include fever, new murmurs, and peripheral stigmata (e.g., splinter haemorrhages, Janeway lesions, Osler’s nodes). Poor dental hygiene (as noted in one case) is a risk factor.
• Ventricular Arrhythmias: Chronic MR and its complications can increase the risk of ventricular arrhythmias.