50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

Classification, Phenotypes & Staging of Heart Failure

Heart failure (HF) is a complex clinical syndrome resulting from any structural or functional impairment of ventricular filling or ejection of blood. Cardinal manifestations include dyspnea, fatigue, exercise intolerance, and signs of fluid retention (pulmonary crackles, elevated jugular venous pressure, peripheral edema).

Heart Failure Phenotypes by Ejection Fraction

The 2022 ACC/AHA/HFSA guidelines classify heart failure into distinct phenotypes based on left ventricular ejection fraction (LVEF), which fundamentally guides clinical prognosis and evidence-based pharmacotherapy:

                  HEART FAILURE PHENOTYPIC CLASSIFICATION

   Phenotype             LVEF Cutoff      Cardinal Pathophysiology & Structural Features
   ═════════════════════════════════════════════════════════════════════════════════════════
   Heart Failure with    LVEF <= 40%      Primary systolic contractile failure; progressive
   Reduced EF (HFrEF)                     ventricular dilation; eccentric hypertrophy; massive
                                          neurohormonal activation (RAAS, sympathetic nervous system).

   Heart Failure with    LVEF 41% to 49%  Intermediate demographic and clinical profile;
   Mildly Reduced EF                      substantial biological overlap with HFrEF; post-hoc trial
   (HFmrEF)                               analyses prove significant benefit from HFrEF GDMT.

   Heart Failure with    LVEF >= 50%      Primary diastolic relaxation impairment; increased chamber
   Preserved EF (HFpEF)                   stiffness; concentric LV hypertrophy; elevated LV filling
                                          pressures (LVEDP and PCWP); microvascular inflammation.

   Heart Failure with    Previous LVEF    Subgroup of HFrEF patients who demonstrate significant
   Improved EF (HFimpEF) <=40% with       structural recovery and LVEF increase >40% on GDMT;
                         follow-up >40%   MANDATORY RULE: Continue full GDMT indefinitely (do NOT stop!).
   ═════════════════════════════════════════════════════════════════════════════════════════

• The Diagnostic Framework for HFpEF: The H2FPEF Score:
  • Diagnosing HFpEF is notoriously challenging because resting echocardiography may reveal a normal LVEF and non-dilated ventricles.
  • The validated H2FPEF Score calculates clinical probability based on 6 weighted clinical variables:
    • H: Heavy (Body Mass Index >30 kg/m²) = 2 points;
    • H: Hypertensive (requiring >=2 antihypertensive medications) = 1 point;
    • F: Atrial Fibrillation (paroxysmal or persistent) = 3 points;
    • P: Pulmonary Hypertension (pulmonary artery systolic pressure >35 mmHg on echo) = 1 point;
    • E: Elder (age >60 years) = 1 point;
    • F: Filling Pressures Elevated (echocardiographic early mitral inflow-to-annular tissue velocity ratio, $E/e' > 9$) = 1 point.
  • An H2FPEF score >=6 points confirms the diagnosis of HFpEF with >90% probability.

Longitudinal Staging (ACC/AHA) vs. Functional Severity (NYHA)

Heart failure is categorized using two complementary classification systems: the progressive ACC/AHA Stages (A through D) and the dynamic, symptom-driven New York Heart Association (NYHA) Functional Classes (I through IV).

                  ACC/AHA STAGES VS. NYHA FUNCTIONAL CLASSIFICATION

   ACC/AHA Stage (Longitudinal Progression)     NYHA Functional Class (Subjective Symptoms)
   ═════════════════════════════════════════════════════════════════════════════════════════
   Stage A: At Risk for Heart Failure           (No NYHA equivalent: asymptomatic)
   Patients with risk factors (HTN, diabetes,
   ASCVD, obesity, cardiotoxins) WITHOUT
   structural disease or symptoms.

   Stage B: Pre-Heart Failure                   NYHA Class I: No Limitation
   Patients with structural heart disease (LVH,  Ordinary physical activity does not cause undue
   LVEF <=40%, chamber enlargement, prior MI)   fatigue, palpitation, or dyspnea.
   OR elevated cardiac biomarkers (BNP/troponin)
   WITHOUT past or present HF symptoms.

   Stage C: Symptomatic Heart Failure           NYHA Class II: Slight Limitation
   Structural heart disease WITH past or        Comfortable at rest; ordinary activity causes
   current signs/symptoms of heart failure.     fatigue, palpitation, or dyspnea.

                                                NYHA Class III: Marked Limitation
                                                Comfortable at rest; LESS THAN ordinary
                                                activity causes fatigue or dyspnea.

   Stage D: Advanced / Refractory HF            NYHA Class IV: Severe Symptoms at Rest
   End-stage structural heart disease with      Inability to perform any physical activity without
   severe refractory symptoms at rest despite   discomfort; symptoms present even at complete rest;
   maximal GDMT; requires specialized advanced  frequent hospitalizations; bedbound.
   therapies (inotropes, LVAD, transplant, hospice).
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The "Four Pillars" of Quadruple GDMT in HFrEF

In patients with symptomatic Heart Failure with Reduced Ejection Fraction (HFrEF: Stage C, LVEF <=40%), contemporary guideline consensus establishes Quadruple Guideline-Directed Medical Therapy (GDMT). Initiating and titrating all four foundational drug classes simultaneously reduces all-cause mortality, cardiovascular death, and heart failure hospitalizations by over 60% compared to historical standards.

                  THE FOUR PILLARS OF QUADRUPLE GDMT FOR HFREF

   Pillar & Class        Target Agents & Dosing                        Mechanisms & Trial Evidence
   ═════════════════════════════════════════════════════════════════════════════════════════════════════════════
   1. ARNI               Sacubitril / Valsartan                        Inhibits neprilysin (enhances natriuretic
      (Preferred over    (Initial: 24/26 mg or 49/51 mg BID;           peptides) + blocks AT1 receptor;
      ACEi / ARB)        Target: 97/103 mg twice daily)                PARADIGM-HF: 20% reduction in CV death/HF hosp.
                                                                       MANDATORY 36-HOUR WASHOUT from ACEi!

   2. Evidence-Based     ONLY THREE APPROVED AGENTS:                   Competitively blocks adrenergic cardiotoxicity,
      Beta-Blockers      • Metoprolol succinate ER (target 200 mg qd)  reduces arrhythmias, reverses LV remodeling;
                         • Carvedilol (target 25-50 mg BID)            MERIT-HF, COPERNICUS, CIBIS-II trials:
                         • Bisoprolol (target 10 mg daily)             ~35% reduction in all-cause mortality.

   3. Mineralocorticoid  Spironolactone (12.5-25 mg; target 50 mg qd)  Blocks aldosterone binding in myocardium/kidney;
      Receptor           OR Eplerenone (25 mg; target 50 mg qd)        anti-fibrotic; reduces sudden cardiac death;
      Antagonist (MRA)                                                 RALES, EMPHASIS-HF: 30% mortality reduction.

   4. SGLT2 Inhibitor    Dapagliflozin 10 mg daily                     Promotes osmotic natriuresis, reduces preload/
                         OR Empagliflozin 10 mg daily                  afterload, improves myocardial energetics;
                                                                       DAPA-HF, EMPEROR-Reduced: 25% CV death/hosp drop;
                                                                       PROVEN EFFECTIVE IN DIABETICS & NON-DIABETICS!
   ═════════════════════════════════════════════════════════════════════════════════════════════════════════════

Critical Pharmacologic & Safety Rules for the Four Pillars

1. ARNI (Sacubitril/Valsartan) & The 36-Hour Washout Rule:
   • Mechanism: Sacubitril is a prodrug that inhibits neprilysin (neutral endopeptidase), the primary enzymatic pathway degrading endogenous vasoactive natriuretic peptides (ANP, BNP, CNP), bradykinin, and adrenomedullin. Accumulation of natriuretic peptides promotes diuresis, natriuresis, vasodilation, and reverse remodeling. Valsartan selectively blocks angiotensin II AT1 receptors.
   • PARADIGM-HF Trial: Proved Sacubitril/Valsartan is significantly superior to enalapril 10 mg BID, producing a 20% reduction in cardiovascular death and a 21% reduction in heart failure hospitalizations. ARNI is the preferred first-line agent over ACEi or ARB for all symptomatic HFrEF patients.

   • [!CAUTION] THE CRITICAL SAFETY MANDATE: 36-HOUR WASHOUT PERIOD When switching a patient from an ACE inhibitor (e.g., lisinopril, enalapril) to Sacubitril/Valsartan, the clinician must enforce a MANDATORY 36-HOUR WASHOUT PERIOD between the last dose of the ACE inhibitor and the first dose of Sacubitril/Valsartan. Both ACE and neprilysin degrade bradykinin. Concurrent inhibition of both enzymes leads to massive, unchecked bradykinin accumulation, precipitating catastrophic, life-threatening angioedema with acute airway obstruction. When switching from an ARB to Sacubitril/Valsartan, NO WASHOUT PERIOD IS REQUIRED (because ARBs do not inhibit bradykinin degradation).

   • Biomarker Monitoring Pearl: Because neprilysin degrades BNP, administration of Sacubitril/Valsartan causes a pharmacologic rise in circulating BNP. Therefore, serum BNP levels are falsely elevated and cannot be used to assess decompensation. Clinicians must measure N-terminal pro-B-type natriuretic peptide (NT-proBNP), which is not a substrate for neprilysin and accurately reflects myocardial wall stress.
2. Evidence-Based Beta-Blockers: Only Three Approved Agents:
   • Only three specific beta-blockers are supported by robust clinical trial evidence demonstrating significant reductions in all-cause mortality in HFrEF:
     1. Metoprolol succinate extended-release (MERIT-HF trial; target 200 mg once daily);
     2. Carvedilol (non-selective beta and alpha-1 blocker; COPERNICUS and CAPRICORN trials; target 25 to 50 mg twice daily);
     3. Bisoprolol (selective beta-1 blocker; CIBIS-II trial; target 10 mg once daily).
   • Agents Strictly Ineffective / Avoided in HFrEF: Metoprolol tartrate (short-acting; the COMET trial proved metoprolol tartrate is markedly inferior to carvedilol and failed to improve survival), atenolol, and propranolol are NOT approved for HFrEF and must never be prescribed for this indication.
   • Initiation Protocol: Beta-blockers must be initiated only in clinically stable, euvolemic patients (no active fluid overload or worsening decompensation). "Start low and go slow," titrating upward every 2 to 4 weeks toward target trial doses.
3. Mineralocorticoid Receptor Antagonists (MRAs):
   • Spironolactone (12.5 to 25 mg daily) or Eplerenone (25 to 50 mg daily; selective MRA avoiding gynecomastia).
   • Indicated in all symptomatic HFrEF patients with LVEF <=35% (NYHA Class II-IV).
   • Prerequisites & Safety Thresholds: Baseline serum potassium must be <=5.0 mEq/L and eGFR must be >=30 mL/min/1.73m² (or serum creatinine <=2.5 mg/dL in men, <=2.0 mg/dL in women). Monitor electrolytes and renal function at 1 week, 4 weeks, and every 3 to 6 months. Hold or discontinue if serum potassium exceeds 5.5 mEq/L.
4. SGLT2 Inhibitors (Dapagliflozin & Empagliflozin):
   • Dapagliflozin (10 mg daily) and Empagliflozin (10 mg daily) represent the fourth pillar of GDMT.
   • The landmark DAPA-HF and EMPEROR-Reduced trials demonstrated a profound 25% to 30% reduction in cardiovascular death and heart failure hospitalization.

   • [!IMPORTANT] THE UNIVERSAL SGLT2i PEARL: INDEPENDENT OF DIABETES The survival and hospitalization benefits of SGLT2 inhibitors in HFrEF are IDENTICAL IN PATIENTS WITH AND WITHOUT TYPE 2 DIABETES MELLITUS. In non-diabetic heart failure patients, SGLT2 inhibitors do not cause hypoglycemia. They function as neurohormonal modifiers that reduce intracardiac filling pressures, enhance myocardial energetics, promote osmotic natriuresis, and prevent chronic renal decline.

Decongestion, Second-Line Therapies & Device Interventions

Decongestion: Loop Diuretic Titration

Loop diuretics (furosemide, bumetanide, torsemide) act on the Na+/K+/2Cl- cotransporter in the thick ascending limb of the loop of Henle.

• Role in GDMT: Loop diuretics do NOT reduce mortality in HFrEF; their sole clinical purpose is to restore and maintain euvolemia by eliminating peripheral edema, ascites, and pulmonary venous congestion.
• Bioavailability & Conversions:
  • Oral furosemide has poor and highly erratic oral bioavailability (~50%, varying from 10% to 90%), which is severely impaired by gut wall edema in decompensated heart failure. In acute decompensation, IV furosemide is approximately twice as potent as oral furosemide (40 mg oral = 20 mg IV).
  • Torsemide (80-100% bioavailability) and Bumetanide (80-100% bioavailability) exhibit highly predictable oral absorption unaffected by bowel edema.
  • Dose Equivalence: Oral Furosemide 40 mg = IV Furosemide 20 mg = Oral Torsemide 20 mg = Oral Bumetanide 1 mg.
• Diuretic Resistance: Managed by escalating loop diuretic doses, switching from oral furosemide to torsemide/bumetanide, or administering sequential nephron blockade by adding a thiazide diuretic (metolazone 2.5 to 5 mg PO or IV chlorothiazide) 30 minutes prior to the loop diuretic dose.

Phenotype-Specific Second-Line Therapies

• Hydralazine plus Isosorbide Dinitrate (BiDil):
  • The A-HeFT trial demonstrated that the fixed-dose combination of hydralazine (direct arteriolar vasodilator) plus isosorbide dinitrate (venodilator) produced a 43% reduction in mortality and a 33% reduction in HF hospitalizations when added to standard therapy in self-identified Black patients with persistent NYHA Class III-IV symptoms.
  • Indicated in self-identified Black patients with persistent symptoms despite optimal quadruple GDMT, OR in any patient intolerant to ARNI/ACEi/ARB due to severe renal insufficiency or intractable hyperkalemia.
• Ivabradine:
  • Selectively inhibits the hyperpolarization-activated cyclic nucleotide-gated ($I_f$) funny current in the sinoatrial node, slowing sinus rate without affecting inotropy, ventricular repolarization, or blood pressure.
  • Indicated in patients with symptomatic HFrEF (LVEF <=35%), in normal sinus rhythm with a resting heart rate >=70 bpm, who are already receiving maximally tolerated doses of an evidence-based beta-blocker (or have a documented contraindication to beta-blockers).
• Vericiguat:
  • An oral stimulator of soluble guanylate cyclase (sGC), directly enhancing the cyclic GMP pathway in smooth muscle and myocardium.
  • Indicated in high-risk HFrEF patients with a recent worsening heart failure hospitalization or outpatient IV diuretic requirement despite optimal GDMT (VICTORIA trial).

Device Therapy: Primary Prevention ICD & CRT

Sudden cardiac death from ventricular tachycardia or ventricular fibrillation accounts for up to 50% of deaths in HFrEF. Device therapy indications are strictly guided by LVEF, etiology, and QRS morphology:

                  DEVICE THERAPY INDICATIONS IN HFREF

   Device Modality       Guideline Indications & Selection Criteria
   ═════════════════════════════════════════════════════════════════════════════════════════
   Implantable           PRIMARY PREVENTION OF SUDDEN CARDIAC DEATH:
   Cardioverter-         1. Ischemic Cardiomyopathy: LVEF <= 35%, NYHA Class II or III,
   Defibrillator (ICD)      at least >= 40 DAYS post-myocardial infarction, AND on >= 3 months
                            of optimal guideline-directed medical therapy.
                         2. Non-Ischemic Dilated Cardiomyopathy: LVEF <= 35%, NYHA Class II or III,
                            on >= 3 months of optimal guideline-directed medical therapy.
                         *Exclusions: NYHA Class IV refractory symptoms (unless awaiting LVAD/transplant);
                         life expectancy < 1 year.

   Cardiac               BIVENTRICULAR PACING FOR MECHANICAL DYSSYNCHRONY:
   Resynchronization     1. LVEF <= 35% on optimal GDMT;
   Therapy (CRT / CRT-D) 2. Normal Sinus Rhythm;
                         3. Left Bundle Branch Block (LBBB) with QRS duration >= 150 ms (Class 1)
                            (or LBBB with QRS 120-149 ms, or non-LBBB with QRS >=150 ms [Class 2a]);
                         4. Symptomatic NYHA Class II, III, or ambulatory Class IV.
   ═════════════════════════════════════════════════════════════════════════════════════════

Contemporary Management of HFpEF (LVEF >=50%)

Historically, clinical trials of ACE inhibitors, ARBs, and beta-blockers in HFpEF failed to demonstrate mortality benefits. However, groundbreaking recent trials have revolutionized the therapeutic paradigm:

1. SGLT2 Inhibitors: The Landmark Class 1 GDMT:
   • Empagliflozin (EMPEROR-Preserved trial) and Dapagliflozin (DELIVER trial) are the first and only medications proven to significantly reduce the composite risk of cardiovascular death and heart failure hospitalizations across the entire spectrum of HFpEF.
   • SGLT2 inhibitors now carry a Class 1 guideline recommendation for all patients with HFpEF regardless of diabetes status.
2. Mineralocorticoid Receptor Antagonists (MRAs):
   • In the TOPCAT trial, spironolactone significantly reduced heart failure hospitalizations in patients with elevated natriuretic peptides, carrying a Class 2b recommendation in HFpEF.
3. ARNI (Sacubitril/Valsartan):
   • In the PARAGON-HF trial, sacubitril/valsartan demonstrated a reduction in heart failure hospitalizations, with greatest efficacy observed in patients with LVEF on the lower end of the preserved spectrum (LVEF 50% to 57%) and in women (Class 2b recommendation).
4. Loop Diuretics & Aggressive Comorbidity Control:
   • Titrate loop diuretics to relieve systemic and pulmonary venous congestion (edema, elevated jugular venous distention, dyspnea).
   • Rigorously manage contributing comorbidities: strict blood pressure control (<130/80 mmHg), rate or rhythm control in atrial fibrillation, continuous positive airway pressure (CPAP) for obstructive sleep apnea, and structured weight loss.