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Prosthetic Valves


Physical Examination

General examination:

  • Surgical scars: median sternotomy or small infraclavicular scar (evidence of prior valve replacement or endocarditis treatment)

  • Look at the legs (vein harvesting scars)

  • Signs of heart failure (fatigue, exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, fluid retention)

  • Stigmata of endocarditis (pyrexia, clubbing, splinter haemorrhages, Osler's nodes, Janeway lesions, Roth spots, splenomegaly, microscopic hematuria, neurological deficits)

  • Bruising from warfarin (suggesting anticoagulation for mechanical valve or atrial fibrillation)

  • Anaemia and jaundice (due to intravascular mechanical hemolysis or subacute bacterial endocarditis)

Precordial inspection:

  • Visible cardiac apex beat (may be normal or displaced, depending on ventricular function)

  • Chest deformities or surgical scars (from valve replacement surgery)

Palpation:

  • Apex beat (may be normal or displaced, depending on ventricular function)

  • Parasternal heave (if right ventricular hypertrophy is present)

  • Absence of palpable thrill (if the valve replacement was successful)

Auscultation:

  • Prosthetic valve clicks (audible in mechanical valves, timing dependent on valve position)

  • Soft systolic murmur across aortic or pulmonary prosthesis (normal in the absence of stenosis)

  • Regurgitant murmur (indicative of paravalvular or valvular leak, never normal)

  • Possible new murmur (if there is prosthetic valve dysfunction or complications)

Additional examination:

  • Peripheral pulses (to assess for any vascular complications, such as aortic coarctation or peripheral embolism)

  • Blood pressure (evaluating for post-operative hypertension or hypotension)

  • Lung auscultation (checking for clear lung fields, indicating the absence of pulmonary congestion)

  • Abdominal examination (assessing for the absence of hepatomegaly or ascites, indicating improvement in right-sided heart function)


Investigations


Laboratory tests:

  • Complete blood count (assessing for anaemia, infection, or thrombocytopenia)

  • Renal function tests (evaluating kidney function and electrolyte balance)

  • Liver function tests (assessing hepatic function and synthetic capacity)

  • Coagulation profile (checking for coagulopathy, especially if anticoagulated)

  • Cardiac biomarkers (troponin, BNP/NT-proBNP, to assess cardiac stress or injury)

  • Inflammatory markers (CRP, ESR, to identify inflammation or infection)

  • Blood cultures (if suspecting infective endocarditis or prosthetic valve infection)

Imaging:

  • Chest X-ray (evaluating heart size, pulmonary congestion, or lung pathology)

  • Echocardiography (assessing prosthetic valve function, ventricular function, and chamber dimensions)

    • Transthoracic echocardiography (TTE) as the initial noninvasive imaging modality

    • Transesophageal echocardiography (TEE) for a more detailed assessment, especially in cases of prosthetic valves or endocarditis

  • Cardiac CT (evaluating valve morphology, prosthetic valve complications, or other structural abnormalities)

  • Cardiac MRI (assessing myocardial function, tissue characterisation, and prosthetic valve assessment)


Invasive tests:

  • Cardiac catheterisation (if indicated, to evaluate coronary artery disease, hemodynamic parameters, or valve complications)

  • Electrophysiology study (if arrhythmias are suspected or need further evaluation)

Other tests:

  • Electrocardiogram (ECG) (assessing for arrhythmias, ischemia, or other electrical abnormalities)

  • Ambulatory ECG monitoring (Holter monitor, event monitor, for detecting intermittent arrhythmias)

  • Treadmill or bicycle exercise test (assessing exercise capacity, ischemia, or arrhythmias)

  • Stress echocardiography (evaluating valve function or other hemodynamic changes under stress, if indicated)

Management

General management:

  • Regular follow-up: monitor valve function and overall health

  • Dental hygiene: maintain oral health to prevent infective endocarditis

  • Education: inform the patient about the importance of anticoagulation and signs of complications

Medical management:

  • Anticoagulation:

    • Mechanical valves: lifelong warfarin (target INR 2.5-3.5)

    • Bioprosthetic valves: warfarin for 3 months, then aspirin

  • Antiplatelet therapy: low-dose aspirin for all patients

  • Heart failure management: ACE inhibitors, beta-blockers, diuretics, aldosterone antagonists, digoxin

  • Rate control: beta-blockers or calcium channel blockers for atrial fibrillation/flutter

  • Rhythm control: antiarrhythmic drugs or electrical cardioversion for atrial fibrillation/flutter

Surgical management:

  • Prosthetic valve dysfunction: consider reoperation for severe stenosis, regurgitation, or valve thrombosis

  • Infective endocarditis: valve replacement surgery if the infection is uncontrolled or complications arise

Other management:

  • Infective endocarditis prophylaxis: antibiotics before dental or other high-risk procedures

  • Pregnancy: high-risk, multidisciplinary care, closely monitor anticoagulation, consider delivery planning

  • Travel: carry identification (e.g., medical alert bracelet) indicating the type of prosthetic valve and anticoagulation therapy

  • Lifestyle modifications: exercise, diet, smoking cessation, and stress reduction for overall cardiovascular health

Indications for Mitral Valve Replacement

I. Indications for MVR in Mitral Regurgitation (MR)


A. Severe symptomatic MR

  1. New York Heart Association (NYHA) functional class III or IV symptoms despite optimal medical therapy.

  2. Acute MR with hemodynamic instability or pulmonary oedema refractory to medical therapy.

B. Asymptomatic MR with impaired LV function

  1. Left ventricular ejection fraction (LVEF) ≤60%.

  2. Progressive left ventricular dilation (end-systolic dimension ≥45 mm).

C. Asymptomatic MR with other surgical indications

  1. Concomitant coronary artery bypass graft (CABG) surgery or aortic valve replacement (AVR).

  2. Severe pulmonary hypertension (pulmonary artery systolic pressure >50 mmHg at rest or >60 mmHg with exercise).


II. Indications for MVR in Mitral Stenosis (MS)

A. Severe symptomatic MS

  1. NYHA functional class III or IV symptoms despite optimal medical therapy.

  2. Severe pulmonary hypertension (pulmonary artery systolic pressure >50 mmHg at rest or >60 mmHg with exercise).

  3. Recurrent embolic events despite anticoagulation.

B. Asymptomatic MS with other surgical indications

  1. Concomitant CABG surgery, AVR, or tricuspid valve surgery.

  2. Severe MS (mitral valve area <1.0 cm2) with atrial fibrillation or left atrial thrombus.

Key Points

  • MVR is indicated for both mitral regurgitation and mitral stenosis when conservative management is insufficient.

  • Indications for MVR include severe symptomatic disease, impaired LV function, and concomitant cardiac surgery.

Indications of Aortic Valve Replacement

I. Introduction

  • Aortic valve replacement (AVR) is a surgical procedure to treat aortic valve disease, particularly aortic stenosis (AS) and aortic regurgitation (AR).

II. Indications for AVR in Aortic Stenosis (AS)

A. Symptomatic severe AS

  1. New York Heart Association (NYHA) functional class II, III, or IV symptoms (e.g., angina, syncope, or heart failure) despite optimal medical therapy.

  2. Aortic valve area (AVA) <1.0 cm2 or indexed AVA <0.6 cm2/m2, with a mean gradient ≥40 mmHg or peak velocity ≥4.0 m/s.

B. Asymptomatic severe AS with impaired LV function

  1. Left ventricular ejection fraction (LVEF) <50%.

  2. Severe AS (AVA <1.0 cm2 or indexed AVA <0.6 cm2/m2, with a mean gradient ≥40 mmHg or peak velocity ≥4.0 m/s).

C. Asymptomatic severe AS with other surgical indications

  1. Concomitant coronary artery bypass graft (CABG) surgery or mitral valve surgery.

  2. Rapid hemodynamic progression (mean gradient increase ≥10 mmHg/year or peak velocity increase ≥0.3 m/s/year).

D. Asymptomatic severe AS with elevated risk of events

  1. Abnormal exercise test (e.g., symptoms, hypotensive response, or complex ventricular arrhythmias).

  2. Very severe AS (mean gradient ≥60 mmHg or peak velocity ≥5.0 m/s).

III. Indications for AVR in Aortic Regurgitation (AR)

A. Severe symptomatic AR

  1. NYHA functional class III or IV symptoms despite optimal medical therapy.

  2. Left ventricular end-systolic dimension (LVESD) ≥50 mm, left ventricular end-diastolic dimension (LVEDD) ≥65 mm, or LVEF <50%.

B. Asymptomatic severe AR with impaired LV function

  1. LVEF <50%.

  2. LVESD ≥50 mm or LVEDD ≥65 mm.

C. Asymptomatic severe AR with other surgical indications

  1. Concomitant CABG surgery or mitral valve surgery.

  2. Progressive left ventricular dilation (LVESD ≥50 mm or LVEDD ≥65 mm).

Key Points

  • AVR is indicated for both aortic stenosis and aortic regurgitation when conservative management is insufficient.

  • Indications for AVR include severe symptomatic disease, impaired LV function, and concomitant cardiac surgery.

Choice of Prosthetic Valves

I. Introduction

  • In prosthetic valve replacement, two main types of valves are used: mechanical valves and bioprosthetic valves (also known as tissue valves).

II. Mechanical Valves

A. Advantages

  1. Durable: longer lifespan, typically 20-30 years or more.

  2. Lower risk of structural valve deterioration.

B. Disadvantages

  1. Requires lifelong anticoagulation with warfarin to prevent valve thrombosis.

  2. Higher risk of thromboembolic events and anticoagulation-related bleeding.

  3. It may produce an audible clicking sound.

C. Indications

  1. Patients aged <60-65 years without contraindications to anticoagulation.

  2. Patients who require long-term anticoagulation for other reasons (e.g., atrial fibrillation, recurrent thromboembolic events).

III. Bioprosthetic Valves

A. Advantages

  1. No need for lifelong anticoagulation (except for a limited period postoperatively).

  2. Lower risk of thromboembolic events and anticoagulation-related bleeding.

  3. Quieter valve sound.

B. Disadvantages

  1. Limited durability: typically 10-15 years, may require reoperation due to structural valve deterioration.

  2. Higher risk of valve failure, particularly in younger patients.

C. Indications

  1. Patients aged >65-70 years, as the risk of reoperation is lower in older patients.

  2. Women considering pregnancy as anticoagulation can be teratogenic.

  3. Patients with contraindications to anticoagulation or a history of bleeding complications.

IV. Balancing Factors

  1. Age: younger patients may be more suitable for mechanical valves due to durability, while older patients may be more suitable for bioprosthetic valves due to lower reoperation risk.

  2. Anticoagulation: the need for lifelong anticoagulation is a major consideration, with mechanical valves requiring strict anticoagulation and bioprosthetic valves offering more flexibility.

  3. Comorbidities and lifestyle: consider patient preferences, occupation, and activities that may increase bleeding risk.

Key Points

  • The choice between mechanical and bioprosthetic valves depends on factors such as patient age, the need for anticoagulation, and comorbidities.

Complications of Prosthetic Valve Disease

  • Thromboembolic complications:

  • Bleeding complications (due to anticoagulation)

  • Infective endocarditis:

  • Structural valve degeneration (calcification, wear and tear)

  • Paravalvular leak (valve dehiscence)

  • Mechanical complications (valve dysfunction)

  • Haemolysis

  • Atrial fibrillation




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