2.2 Heart Failure & Cardiac Arrhythmias

Heart Failure & Cardiac Arrhythmias

1. Heart Failure Definitions & Classification

Heart Failure (HF) is a complex clinical syndrome resulting from structural or functional impairment of ventricular filling or ejection. It is characterized by elevated intracardiac pressures and inadequate cardiac output at rest or during exercise.

Ejection Fraction Categories (ESC / ACC / AHA Guidelines)

• Heart Failure with Reduced Ejection Fraction (HFrEF): $LVEF \le 40%$. Characterized by impaired myocardial contractility (systolic dysfunction), most commonly secondary to CAD, MI, or dilated cardiomyopathy.
• Heart Failure with Mildly Reduced Ejection Fraction (HFmrEF): $LVEF \text{ 41–49%}$. Represents a middle spectrum requiring mild systolic dysfunction management.
• Heart Failure with Preserved Ejection Fraction (HFpEF): $LVEF \ge 50%$. Driven by impaired ventricular relaxation and compliance (diastolic dysfunction), strongly linked to long-standing hypertension, aging, obesity, and diabetes mellitus.

Functional & Staging Systems

2. Diagnostic Workup & Biomarkers

• Natriuretic Peptides (BNP & NT-proBNP): Ventricular myocytes release B-type natriuretic peptide in response to wall stress and volume overload.
  • BNP: $<100 \text{ pg/mL}$ rule-out value in acute dyspnea; $>400 \text{ pg/mL}$ strongly indicates acute HF.
  • NT-proBNP: $<300 \text{ pg/mL}$ rule-out value; age-adjusted cutoffs for rule-in: $>450 \text{ (<50 yrs)}$, $>900 \text{ (50-75 yrs)}$, $>1800 \text{ (>75 yrs)}$.
  • Note: Patients taking Sacubitril/Valsartan (ARNI) will have artificially elevated BNP levels (because Sacubitril inhibits neprilysin which degrades BNP), but NT-proBNP is not degraded by neprilysin and remains accurate.
• Transthoracic Echocardiogram (TTE): Essential initial test to measure LVEF, assess valvular structure, wall motion abnormalities, and estimate pulmonary artery systolic pressure (PASP).
• Chest X-Ray (ABCDE Criteria):
  • Alveolar edema (bat-wing appearance)
  • Berley (Kerley) B lines (interlobular septal fluid)
  • Cardiomegaly (Cardiothoracic ratio >0.50)
  • Dilated upper lobe vessels (cephalization)
  • Effusions (pleural, blunting of costophrenic angles)

3. Guideline-Directed Medical Therapy (GDMT) for HFrEF

All patients with HFrEF ($LVEF \le 40%$) must be established on the Four Foundational Pillars of GDMT unless contraindications exist, as each class independently reduces all-cause mortality:

Additional Therapies & Device Indications

• Loop Diuretics (Furosemide, Torsemide): Symptom relief of congestion; does NOT confer mortality benefit, adjust to maintain euvolemia.
• Ivabradine: Inhibits funny ($I_f$) channels in SA node. Indicated if patient is in sinus rhythm with resting heart rate $\ge 70 \text{ bpm}$ despite maximal tolerated beta-blocker dose.
• Hydralazine + Isosorbide Dinitrate: Indicated in self-identified Black patients with persistent NYHA Class III-IV HFrEF despite GDMT, or in patients intolerant to ACEi/ARB/ARNI due to severe renal impairment or hyperkalemia.
• Implantable Cardioverter-Defibrillator (ICD): Primary prevention of sudden cardiac death if $LVEF \le 35%$ despite $\ge 3$ months of optimal GDMT and NYHA Class II-III.
• Cardiac Resynchronization Therapy (CRT-D): Indicated if $LVEF \le 35%$, Sinus Rhythm, and Left Bundle Branch Block (LBBB) with $QRS \ge 150 \text{ ms}$.

4. Acute Decompensated Heart Failure (ADHF)

Clinical presentation is categorized based on Hemodynamic Profiles (Forrester Classification):

• Warm & Wet (Most Common ~80%): Adequate perfusion, severe congestion. Treated with IV Loop Diuretics (Furosemide IV dose $\ge 1-2.5\times$ oral home dose) + IV Vasodilators (Nitroglycerin / Nitroprusside if $SBP > 110 \text{ mmHg}$).
• Cold & Wet (Cardiogenic Shock with Congestion): Poor perfusion ($SBP <90 \text{ mmHg}$, cold extremities, oliguria, altered sensorium) + congestion. Treated with IV Inotropes (Dobutamine, Milrinone) $\pm$ Vasopressors (Norepinephrine) to restore organ perfusion before cautious diuresis.

5. Cardiac Arrhythmias

Atrial Fibrillation (AF)

• ECG Characteristics: Irregularly irregular ventricular response, absence of distinct P waves, fibrillatory waves (rate 350-600 bpm).
• Stroke Risk Stratification (CHA2DS2-VASc Score):
  • Congestive heart failure (+1)
  • Hypertension (+1)
  • A2ge $\ge 75$ years (+2)
  • Diabetes mellitus (+1)
  • S2troke / TIA / Thromboembolism (+2)
  • Vascular disease (prior MI, PAD, aortic plaque) (+1)
  • Age 65–74 years (+1)
  • Scex category (Female) (+1)
  • Recommendation: Score $\ge 2$ in men or $\ge 3$ in women mandates oral anticoagulation with Direct Oral Anticoagulants (DOACs: Apixaban, Rivaroxaban, Dabigatran) preferred over Warfarin.
• Rate Control vs Rhythm Control:
  • Rate Control: Target resting HR <110 bpm using Beta-blockers (Metoprolol), Non-dihydropyridine CCBs (Diltiazem, Verapamil - avoid CCBs in HFrEF!), or Digoxin.
  • Rhythm Control: Electrical cardioversion or antiarrhythmic drugs (Amiodarone, Flecainide, Propafenone). If AF duration $>48 \text{ hours}$, anticoagulation for at least 3 weeks prior and 4 weeks after cardioversion is required (or TTE/TEE to exclude LA appendage thrombus).

Supraventricular Tachycardia (SVT / AVNRT)

• ECG: Regular, narrow QRS complex (<120 ms), rate 150-250 bpm, P waves hidden or retrogradely buried in QRS.
• Management Algorithm:
  1. Hemodynamically Unstable $\rightarrow$ Immediate Synchronized Cardioversion (50-100 J).
  2. Hemodynamically Stable $\rightarrow$ Vagal Maneuvers (modified Valsalva or carotid sinus massage).
  3. Pharmacotherapy $\rightarrow$ Adenosine $6 \text{ mg}$ rapid IV push followed by $20 \text{ mL}$ saline flush. If no conversion within 1-2 min, give $12 \text{ mg}$ rapid IV push. (Side effects: flushing, bronchospasm, transient cardiac arrest/asystole).
  4. Second-line: IV Beta-blockers or IV Diltiazem/Verapamil.

Ventricular Tachycardia (VT) vs Wide-Complex Tachycardia

• ECG: Broad QRS complex ($\ge 120 \text{ ms}$), rate >100 bpm. Assume ANY wide-complex tachycardia is VT until proven otherwise.
• Brugada Criteria for VT: Absence of RS complex in all precordial leads, RS interval >100 ms, AV dissociation, fusion or capture beats.
• Management:
  • Pulseless VT or VF: Immediate unsynchronized high-energy shock (Defibrillation 200J biphasic) + CPR.
  • Unstable VT with Pulse: Immediate Synchronized Cardioversion (100J).
  • Stable Monomorphic VT: IV Amiodarone ($150 \text{ mg}$ over 10 min followed by infusion) or IV Procainamide.

Atrioventricular (AV) Heart Blocks