2.3 Heart Failure & Valvular Heart Disease

2.3 Heart Failure & Valvular Heart Disease

Heart failure (HF) and valvular heart disease represent major causes of cardiovascular morbidity worldwide. The MRCPI Part I examination heavily emphasizes the modern pharmacological architecture of heart failure, indication criteria for device therapy, hemodynamic assessment, and clear intervention thresholds for valvular lesions.

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Heart Failure Definitions & Categorization

Heart failure is a clinical syndrome characterized by cardinal symptoms (breathlessness, ankle swelling, fatigue) accompanied by signs (elevated JVP, pulmonary crackles, peripheral edema) caused by structural or functional cardiac abnormalities resulting in elevated intracardiac pressures or inadequate cardiac output.

ESC Classification by Left Ventricular Ejection Fraction (LVEF):

1. HFrEF (HF with reduced Ejection Fraction): LVEF <=40%. Characterized by progressive adverse LV remodeling and neurohormonal activation.
2. HFmrEF (HF with mildly reduced Ejection Fraction): LVEF 41–49%. Demonstrates pathophysiological overlap with HFrEF; benefits from similar disease-modifying therapies.
3. HFpEF (HF with preserved Ejection Fraction): LVEF >=50% with objective evidence of cardiac structural/functional impairment (LV hypertrophy, LA enlargement) and diastolic dysfunction.

Diagnostic Biomarkers

• B-type Natriuretic Peptide (BNP): Non-acute threshold >=35 pg/mL; Acute threshold >=100 pg/mL.
• N-terminal pro-BNP (NT-proBNP): Non-acute threshold >=125 pg/mL; Acute threshold >=300 pg/mL.
• High negative predictive value (>95%) makes natriuretic peptides essential for ruling out heart failure in acute dyspnea.

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HFrEF Disease-Modifying Pharmacotherapy ("The Four Pillars")

All patients with HFrEF should be rapidly initiated on the four foundational drug classes, titrated to target doses achieved in clinical trials:

1. Angiotensin Receptor-Neprilysin Inhibitor (ARNI) / ACEi / ARB:
   • Sacubitril/Valsartan (ARNI): Superior to enalapril in reducing mortality and hospitalizations (PARADIGM-HF trial). Dosed starting at 24/26 mg or 49/51 mg bd, target 97/103 mg bd.
   • CRITICAL SAFETY RULE: When switching from an ACE inhibitor to Sacubitril/valsartan, a 36-hour washout period is mandatory to prevent severe angioedema caused by dual inhibition of bradykinin breakdown!
   • ACE inhibitors (Ramipril target 10 mg daily, Enalapril target 10 mg bd) or ARBs (Candesartan target 32 mg daily) are indicated if ARNI is unavailable or poorly tolerated.
2. Evidence-Based Beta-Blockers:
   • Bisoprolol (target 10 mg daily), Carvedilol (target 25–50 mg bd), or Metoprolol Succinate (target 200 mg daily). Inhibits sympathetic hyperactivation; must be started in hemodynamically stable patients at low doses.
3. Mineralocorticoid Receptor Antagonists (MRAs):
   • Spironolactone (target 25–50 mg daily) or Eplerenone (target 50 mg daily). Reduces mortality (RALES and EMPHASIS-HF trials). Serum potassium (<5.0 mmol/L) and eGFR (>30 mL/min/1.73m2) must be monitored.
4. SGLT2 Inhibitors:
   • Dapagliflozin (10 mg daily) or Empagliflozin (10 mg daily). Reduces CV death and HF hospitalizations independent of diabetes status (DAPA-HF and EMPEROR-Reduced trials). Effective down to eGFR >=20 mL/min/1.73m2.

Second-Line & Additional Agents

• Ivabradine: Inhibits $I_f$ current in the SA node. Indicated in sinus rhythm with HR >=70 bpm despite maximum tolerated beta-blocker dose (SHIFT trial).
• Vericiguat: Soluble guanylate cyclase (sGC) stimulator indicated in worsening HFrEF despite GDMT (VICTORIA trial).
• Hydralazine + Isosorbide Dinitrate: Indicated in self-identified Black patients with persistent symptoms (A-HeFT trial) or patients unable to tolerate ARNI/ACEi/ARB due to renal failure or hyperkalemia.
• Loop Diuretics (Furosemide, Bumetanide): Essential for symptom relief of congestion, but do not reduce long-term mortality.

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Device Therapy in Heart Failure

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Valvular Heart Disease

1. Aortic Stenosis (AS)

• Etiology: Calcific degenerative (elderly), Congenital bicuspid aortic valve (younger patients, 30–50 years), or Rheumatic heart disease.
• Classic Symptom Triad: Angina, Syncope, Dyspnea on exertion ("SAD"). Mean survival after symptom onset drops to 2–3 years without intervention.
• Echocardiographic Criteria for Severe AS:
  • Aortic Valve Area (AVA) <1.0 cm2 (indexed <0.6 cm2/m2).
  • Mean transvalvular pressure gradient >=40 mmHg.
  • Peak aortic jet velocity >=4.0 m/s.
• Low-Flow Low-Gradient AS: Dobutamine Stress Echocardiography differentiates true severe AS (flow reserve increases AVA <1.0 cm2 with gradient >40 mmHg) from pseudo-severe AS.
• Management: Surgical Aortic Valve Replacement (SAVR) or Transcatheter Aortic Valve Implantation (TAVI). TAVI is preferred in patients aged >=75 years or those at high surgical risk (STS/EuroSCORE II >8%).

2. Aortic Regurgitation (AR)

• Etiology: Valve leaf disease (endocarditis, bicuspid valve) or Aortic root dilation (Marfan syndrome, aortic dissection, syphilis).
• Physical Signs: Early diastolic decrescendo murmur at left sternal border, Bounding "Corrigan's" water-hammer pulse, Wide pulse pressure, De Musset's sign (head nodding), Quincke's sign (capillary pulsations).
• Intervention Thresholds: Severe symptomatic AR, or asymptomatic severe AR with LVEF <=50% or LV end-systolic diameter (LVESD) >50 mm (or >25 mm/m2).

3. Mitral Stenosis (MS)

• Etiology: Almost exclusively Rheumatic Heart Disease.
• Physical Signs: Malar flush, Opening snap followed by a mid-diastolic rumbling murmur with presystolic accentuation (in sinus rhythm), loudest at apex in left lateral decubitus position.
• Diagnostic Threshold: Severe MS defined by Mitral Valve Area (MVA) <=1.5 cm2.
• Intervention: Percutaneous Mitral Commissurotomy (PMC) is first-line for severe symptomatic MS with favorable anatomy (Wilkins score <=8, no left atrial thrombus, and no >2+ mitral regurgitation). Otherwise, Mitral Valve Replacement.

4. Mitral Regurgitation (MR)

• Primary (Organic) MR: Structural abnormality of leaflets/chordae (Mitral Valve Prolapse / Myxomatous degeneration, Endocarditis). High-pitched holosystolic murmur radiating to the left axilla.
• Secondary (Functional) MR: LV remodeling displacing papillary muscles (ischemic or dilated cardiomyopathy).
• Intervention Thresholds: Primary severe MR warrants surgical repair (preferred over replacement) when symptomatic, or asymptomatic with LVEF <=60% or LVESD >=40 mm. Transcatheter Edge-to-Edge Repair (MitraClip) is indicated for secondary MR in high surgical risk patients meeting COAPT trial criteria.