Cardiac Structures, Valvular Heart Disease, and Cardiomyopathies

Heart Valve Anatomy & Physiology

  • Atrioventricular (AV) Valves:

    • Mitral Valve (Bicuspid Valve): Located between the Left Atrium (LA) and Left Ventricle (LV); regulates oxygenated blood flow into the left ventricle.

    • Tricuspid Valve: Located between the Right Atrium (RA) and Right Ventricle (RV); regulates deoxygenated blood flow into the right ventricle.

  • Semilunar Valves:

    • Aortic Valve: Located between the Left Ventricle (LV) and the Aorta; directs oxygenated blood into systemic circulation.

    • Pulmonary Valve: Located between the Right Ventricle (RV) and the Pulmonary Artery (PA); directs blood into pulmonary circulation.


Anatomy of the heart chambers and valves

  • General Etiology of Valvular Heart Disease:

    • The majority of acquired valvular lesions stem from Rheumatic Heart Disease (RHD) secondary to rheumatic fever.

  • Pathophysiologic Valve Abnormalities:

    • Regurgitation (Incompetence / Insufficiency): Incomplete valve closure resulting in abnormal backward leakage (retrograde flow) of blood into the preceding cardiac chamber.

    • Stenosis: Constriction, calcification, or structural narrowing of the valve orifice that impedes forward blood flow (anterograde flow).

Cardiac Murmurs & Diagnostic Classification

  • Heart Sounds:

    • S1S_1 (First Heart Sound): Marks the onset of ventricular systole; produced by the closure of the AV valves (Mitral and Tricuspid).

    • S2S_2 (Second Heart Sound): Marks the onset of ventricular diastole; produced by the closure of the semilunar valves (Aortic and Pulmonary).

  • Timing of Murmurs:

    • Systolic Murmur: Occurs during ventricular contraction between S1S_1 and S2S_2

    • Pattern: S1— murmur —S2S_1 \text{--- murmur ---} S_2

    • Diastolic Murmur: Occurs during ventricular filling between S2S_2 and S1S_1

    • Pattern: S2— murmur —S1S_2 \text{--- murmur ---} S_1

  • Diagnostic Memory Mnemonics:

    • MTR PASS MVP:

    • Mitral and Tricuspid Regurgitation (physiologic or pathological), Physiologic murmurs, Aortic Stenosis, and Mitral Valve Prolapse present as Systolic murmurs/sounds.

    • MS ARD:

    • Mitral Stenosis and Aortic Regurgitation present as Diastolic murmurs.

Mitral Valve Disorders

  • Mitral Stenosis (MS):

    • Pathophysiology: Fusion of mitral valve leaflets leads to a narrowed orifice, creating significant impedance to flow from the LA to the LV.

    • Etiology:

    • Rheumatic fever (most common cause).

    • Calcium deposits / calcification.

    • Atrial myxoma.

    • Thrombus formation.

    • Marfan's Syndrome.

    • Hemodynamic Sequence:

    • Obstruction to blood flow from LA to LV →\rightarrow Increased LA pressure →\rightarrow Increased LA size (atrial enlargement) →\rightarrow Increased Pulmonary Artery (PA) pressure (pulmonary hypertension) →\rightarrow Increased RV size (right ventricular hypertrophy/dilation).

    • Clinical Manifestations & Assessment Findings:

    • Shortness of breath (SOB) / Dyspnea on exertion.

    • Hemoptysis (blood-tinged sputum).

    • Jugular Venous Distension (JVD).

    • Irregularly irregular pulse secondary to Atrial Fibrillation (AF).

    • Right parasternal pulsations or heave.

    • Auscultation: Loud first heart sound (S1S_1), Opening Snap (OS), and Mid-Diastolic Murmur (MDM).

    • Hoarseness of voice (Ortner's syndrome due to LA enlargement compressing the recurrent laryngeal nerve).


Normal heart vs Mitral Valve Stenosis

  • Mitral Valve Regurgitation (MR):

    • Pathophysiology: Incomplete valve closure during ventricular systole allows blood to flow back from the LV into the LA.

    • Etiology: Rheumatic Fever, Infective Endocarditis, Papillary Muscle Dysfunction.

    • Clinical Manifestations & Assessment Findings:

    • Dyspnea on exertion (DOE).

    • Paroxysmal Nocturnal Dyspnea (PND), Orthopnea, and nocturnal dry cough.

    • Hemoptysis.

    • Pulmonary edema secondary to acute or chronic left atrial elevation/failure.

    • Right-sided heart failure (peripheral edema, JVD, hepatomegaly).

    • Atrial Fibrillation.

    • Embolic phenomena (systemic arterial embolization from mural thrombi).


Mitral regurgitation blood flow

  • Mitral Valve Prolapse (MVP):

    • Pathophysiology: Abnormal displacement or ballooning of one or both mitral valve leaflets into the left atrium during systole, which can lead to progressive mitral regurgitation.


Mitral valve prolapse with regurgitation

Aortic Valve Disorders

  • Aortic Stenosis (AS):

    • Pathophysiology: Impaired opening of the aortic valve leaflets during ventricular systole, impeding outflow from the LV into the systemic aorta.

    • Etiology: Calcific disease, congenital bicuspid valve, rheumatic heart disease.

    • Classic Triad & Presentation:

    • Angina.

    • Syncope.

    • Exertional Dyspnea.

    • Management Overview:

    • Medical management for symptom relief and hemodynamic stability.

    • Surgical interventions: Transcatheter Aortic Valve Replacement (TAVR) or Open Surgical Valve Replacement.


Normal aortic valve vs stenotic aortic valve

  • Aortic Regurgitation (AR):

    • Pathophysiology: Incompetent aortic valve closure during ventricular diastole resulting in regurgitation of blood from the aorta back into the left ventricle.

    • Etiology:

    • Rheumatic fever.

    • Infective endocarditis.

    • Aortic dissection.

    • Secondary syphilis.

    • Post-TAVR procedural complication.

    • Marfan's Syndrome.

    • Characteristic Physical Exam Signs:

    • Water-hammer pulse (Corrigan's pulse): Rapidly rising and sudden collapsing arterial pulse.

    • Traube's sign: Pistol-shot arterial sound heard over the femoral arteries.

    • Hill's sign: Popliteal cuff systolic pressure exceeding brachial pressure by >20–40 mmHg> 20\text{--}40\,mmHg

    • De Musset's sign: Rhythmic head bobbing synchronized with the arterial pulse.

    • Quincke's sign: Visible capillary pulsations in the nail beds upon gentle compression.


Aortic valve regurgitation backflow

Diagnostic Evaluations for Valvular Diseases

  • History and Physical Examination: Initial identification of clinical symptoms, risk factors, and characteristic peripheral vascular signs or cardiac murmurs.

  • Electrocardiogram (EKG / ECG): Identifies underlying cardiac dysrhythmias (e.g., Atrial Fibrillation) and chamber hypertrophy/enlargement (e.g., Left Ventricular Hypertrophy, Left Atrial Enlargement).

  • Echocardiography:

    • Transthoracic Echocardiogram (TTE): Non-invasive standard for visual assessment of valve morphology, motion, regurgitant jets, and ejection fraction.

    • Transesophageal Echocardiogram (TEE): Provides high-resolution imaging of posterior heart structures, valve leaflets, and atrial thrombi.

  • Chest X-Ray (CXR): Evaluates cardiomegaly, cardiac silhouette enlargement, pulmonary congestion, and calcification of valves.

  • Cardiac Catheterization: Measures direct intracardiac pressure gradients, calculates precise valve orifice area, and assesses coronary artery anatomy.

Collaborative Care & Surgical Interventions for Valvular Diseases

  • Prophylactic Antibiotic Therapy:

    • Rationale: Crucial clinical intervention for patients with Rheumatic Heart Disease, Valvular Heart Disease, or prior Infective Endocarditis to prevent recurrent bacterial endocarditis following invasive surgical or dental procedures.

  • Surgical & Interventional Procedures:

    • Valvuloplasty: Surgical reconstruction or repair of diseased valve components.

    • Annuloplasty: Surgical narrowing and reinforcement of a dilated valve annulus using a prosthetic ring or purse-string suturing techniques.

    • Commissurotomy: Incision or separation of fused valve commissures (leaflet boundaries).

    • Transcatheter Valve Therapies:

    • TMVr: Transcatheter Mitral Valve Repair (e.g., MitraClip).

    • TAVR: Transcatheter Aortic Valve Replacement.

  • Valve Replacement Types:

    • Mechanical Valves:

    • Constructed from synthetic, durable materials (e.g., pyrolytic carbon).

    • Advantage: Long-term durability.

    • Requirement: Requires lifelong systemic anticoagulation therapy to prevent valve thrombosis and thromboembolism.

    • Tissue (Bioprosthetic) Valves:

    • Lower risk of thromboembolism compared to mechanical valves; does not require long-term anticoagulation.

    • Disadvantage: Limited lifespan (susceptible to structural valve deterioration over 10–15 years).

    • Allograft (Homograft): Harvested from human cadavers.

    • Xenograft: Harvested from animal tissues (Bovine [cow] or Porcine [pig]).

Overview of Cardiomyopathies

  • Definition: Heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction.

  • Major Categories:

    • Dilated Cardiomyopathy (DCM).

    • Hypertrophic Cardiomyopathy (HCM).

    • Restrictive Cardiomyopathy (RCM).

    • Takotsubo Cardiomyopathy (Stress-induced).

    • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC).


Types of cardiomyopathy overview

Dilated Cardiomyopathy & Takotsubo Cardiomyopathy

  • Dilated Cardiomyopathy (DCM):

    • Incidence: Most common type of cardiomyopathy, accounting for approximately 90%90\% of all cardiomyopathy cases.

    • Pathophysiology: Enlargement/dilation of all cardiac chambers, ventricular wall thinning, severely impaired myocardial contractility, leading to profound systolic dysfunction.

    • Clinical Assessment Findings:

    • Auscultation of an S3S_3 gallop rhythm and functional regurgitant murmurs.

    • Pulmonary rales present on lung auscultation secondary to left heart failure.

    • Marked cardiomegaly visible on chest radiograph.

    • Decreased myocardial contractility leading to diminished cardiac output (COPCOP).

    • High clinical risk for mural thrombi formation, deep vein thrombosis (DVT), and systemic embolic events.

  • Takotsubo Cardiomyopathy:

    • Common Name: Stress-induced cardiomyopathy or "Broken Heart Syndrome".

    • Pathophysiology: Transient apical ballooning and dilation of the left ventricle triggered by extreme physical or emotional stress.

    • Etimology: Named after the Japanese octopus trap ("Tako-Tsubo") due to the characteristic round bottom and narrow neck shape assumed by the hypercontractile base and akinitic apex of the left ventricle during systole.


Takotsubo cardiomyopathy vs normal heart

Hypertrophic Cardiomyopathy

  • Pathophysiology & Characteristics:

    • Massive myocardial hyperkalemic growth / ventricular hypertrophy.

    • Disproportionate asymmetrical septal hypertrophy with or without Left Ventricular Outflow Tract (LVOT) obstruction.

    • Severe diastolic dysfunction caused by rigid, non-compliant ventricular walls that impair ventricular filling.

    • Hemodynamic changes: Reduced ventricular filling →\rightarrow Decreased Left Ventricular End-Diastolic Volume (LVEDVLVEDV) →\rightarrow Reduced Cardiac Output (COPCOP) exacerbated by outflow obstruction.

    • Clinical Significance: Major underlying cause of sudden cardiac death in young athletes secondary to ventricular arrhythmias.


Normal heart vs hypertrophic cardiomyopathy

  • Clinical Manifestations & Assessment Findings:

    • Patients may remain completely asymptomatic until lethal event/presentation.

    • Syncope: Triggered by sudden dysrhythmias or severe drop in cardiac output.

    • Angina: Resulting from massive ventricular hypertrophy exceeding coronary microvascular blood supply and forceful ventricular contractions.

    • Dyspnea: Secondary to elevated left ventricular diastolic filling pressures.

    • Arrhythmias: Atrial fibrillation and dangerous ventricular tachycardia/fibrillation.

    • Physical signs: Bisferiens arterial pulse, double/forceful Point of Maximal Impulse (PMI), and audible S3S_3 / S4S_4 gallop sounds.

Restrictive & Arrhythmogenic Right Ventricular Cardiomyopathies

  • Restrictive Cardiomyopathy (RCM):

    • Incidence: Least common form of cardiomyopathy.

    • Pathophysiology: Excessive rigidity of the ventricular walls leading to poor ventricular compliance.

    • Primary Defect: Diastolic dysfunction — inadequate relaxation and impaired filling of the ventricular cavities during diastole, despite normal or near-normal wall thickness and systolic contraction.


Restrictive cardiomyopathy rigid ventricular wall

  • Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC):

    • Definition: Inherited familial heart muscle disorder characterized by progressive replacement of right ventricular myocardium by fibrous and fatty tissue.

    • Pathophysiology: Progressive fatty replacement of heart muscle weakens the right ventricular wall, predisposing the patient to right ventricular dilation, localized aneurysms, and life-threatening ventricular arrhythmias.


Arrhythmogenic right ventricular cardiomyopathy fatty replacement

Collaborative Management of Cardiomyopathies

  • General Principles: Focuses on treating underlying causes, relieving symptoms, improving cardiac output, and preventing complications.

  • Pharmacological Interventions:

    • Dilated Cardiomyopathy (DCM): Diuretics, Digoxin, Nitrates, and ACE Inhibitors (ACEI) to reduce preload/afterload and manage heart failure symptoms.

    • Anticoagulation Therapy: Mandatory in DCM patients with low ejection fraction or Atrial Fibrillation to prevent mural thrombi and DVT.

    • Hypertrophic Cardiomyopathy (HCM): Beta-blockers are first-line pharmacological agents to reduce heart rate, prolong diastolic filling time, and alleviate outflow tract obstruction. Avoid nitrates and inotropes that worsen outflow tract gradients.

  • Surgical & Advanced Interventions:

    • Surgical Ventriculomyotomy / Septal Myectomy: Surgical resection of hypertrophied septal muscle tissue in HCM to relieve LVOT obstruction.

    • Heart Transplantation: Definitive treatment option for end-stage, refractory Dilated Cardiomyopathy (DCM) and Restrictive Cardiomyopathy (RCM).