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Acute Heart Failure (AHF)

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Acute Heart Failure (AHF)

Acute heart failure (AHF) is the rapid onset or sudden worsening of heart failure symptoms. It is a common medical emergency and often requires hospitalization.

Also called

Congestive heart failure (CHF)

ICD-10

I50.21 + I50.31

Specialty

Cardiology

Onset

Acute

Reviewed

June 2026

On This Page

Overview

Acute Heart Failure (AHF) is the sudden onset or rapid worsening of heart failure symptoms due to the heart’s inability to pump enough blood to meet the body’s needs. It is a medical emergency that often requires hospitalization.

Etiology & Risk Factors

Etiology (Common Causes) for Acute Heart Failure (AHF)

  • Acute myocardial infarction (heart attack)
  • Acute decompensation of chronic heart failure
  • Uncontrolled hypertension
  • Cardiac arrhythmias (e.g., atrial fibrillation)
  • Valvular heart disease
  • Infection (e.g., pneumonia, sepsis)
  • Pulmonary embolism
  • Myocarditis
  • Renal failure or fluid overload
  • Medication or dietary nonadherence (e.g., excess sodium/fluid intake)

-Risk Factors ;

    • Pre-existing heart failure
    • Coronary artery disease
    • Hypertension
    • Diabetes mellitus
    • Chronic kidney disease
    • Advanced age
    • Obesity
    • Smoking
    • Excessive alcohol or illicit drug use (e.g., cocaine)
    • History of myocardial infarction or cardiomyopathy
    • Valvular heart disease

Pathophysiology

  • Trigger (MI, hypertension, arrhythmia, infection) → Sudden ↓ cardiac pump function → ↓ Cardiac output → Activation of SNS & RAAS → Vasoconstriction + Na⁺/water retention → ↑ Preload & ↑ Afterload → Pulmonary/systemic congestion → Pulmonary edema + dyspnea + peripheral edema → Hypoxia ± end-organ hypoperfusion/cardiogenic shock

     
     

Clinical Presentation

    • Sudden severe shortness of breath (dyspnea)
    • Orthopnea and paroxysmal nocturnal dyspnea (PND)
    • Pulmonary edema with crackles/rales; may produce pink frothy sputum
    • Peripheral edema (legs/ankles) and jugular venous distention (JVD)
    • Tachycardia, tachypnea, and hypoxia
    • Fatigue, weakness, and reduced exercise tolerance
    • Cool, clammy skin and cyanosis (if poor perfusion)
    • Confusion, dizziness, or hypotension in severe cases (may indicate cardiogenic shock)
     

  2. –Clinical Classification : New York Heart Association Classification (NYHA) ;

Heart Failure · NYHA Functional Classification

Class Functional Limitation Symptoms 5-Year Mortality ACC/AHA Stage
I No limitation
Ordinary physical activity causes no symptoms. No restriction on daily activities. Asymptomatic despite cardiac disease <10% Stage C
II Slight limitation
Comfortable at rest. Ordinary activity (climbing stairs, walking briskly) causes fatigue, dyspnea, or palpitations. Dyspnea on moderate exertion; orthopnea may be absent ~20% Stage C
III Marked limitation
Comfortable at rest. Less-than-ordinary activity (dressing, walking on flat) causes symptoms. Dyspnea on minimal exertion, fatigue, orthopnea, possible PND ~50% Stage C
IV Symptoms at rest
Unable to carry on any activity without discomfort. Symptoms present at rest. Bed-to-chair existence. Dyspnea at rest, severe orthopnea, PND, peripheral edema, ascites >50% Stage D

EF-based Classification

HFrEF
EF <40%
Heart Failure with reduced EF — systolic dysfunction. Responds to ACEi/ARB, BB, MRA, SGLT2i, ARNI.
HFmrEF
EF 40–49%
Heart Failure with mildly reduced EF — grey zone. Consider same therapies as HFrEF.
HFpEF
EF ≥50%
Heart Failure with preserved EF — diastolic dysfunction. SGLT2i (dapagliflozin) shown to reduce hospitalizations.

History Taking

Key Questions

-Fluid Congestion (Backward Failure)

  • Exertional Dyspnoea: Onset and severity during physical activity.

  • Orthopnoea: Presence of shortness of breath when lying flat, and the number of pillows required.

  • Paroxysmal Nocturnal Dyspnoea (PND): Sudden awakening at night gasping for air.

  • Peripheral Edema: New or worsening swelling in the ankles, legs, or abdomen.

  • Weight Changes: Rapid, unexpected weight gain over a few days (fluid accumulation).

-Low Cardiac Output (Forward Failure)

    • Fatigue: Severe, unusual exhaustion during basic daily tasks.

    • Cerebral Hypoperfusion: Dizziness, lightheadedness, or confusion, especially when standing.

-Red Flags

  • • Hemodynamic instability
  • • Acute pulmonary edema
  • • Tachyarrhythmias
  • • Bradyarrhythmia
  • • Cardiogenic shock

Physical Examination

-Signs of Volume Overload (Fluid Retention)

  • Elevated Jugular Venous Pressure (JVP): Reflects high pressure in the right atrium. A positive hepatojugular reflux (pressing the liver raises JVP) is a highly reliable sign.

  • Pulmonary Crackles (Crepitations): Fine, inspiratory Velcro-like crackles heard at the lung bases, signaling fluid in the alveoli.

  • Pitting Peripheral Edema: Symmetrical swelling in the lower extremities that leaves an indentation when pressed.

-Signs of Cardiac Dysfunction (The Failing Pump)

  • Displaced Apex Beat: The apex beat is shifted downwards and outwards (lateral to the midclavicular line), indicating left ventricular dilation.

  • Third Heart Sound (S3 Gallop): A low-pitched extra heart sound heard early in diastole, caused by rapid blood flow rushing into a stiff, dilated, and volume-overloaded ventricle.

  • Tachycardia: A rapid heart rate at rest as the sympathetic nervous system tries to compensate for the low stroke volume.

Investigations

  • BNP or NT-proBNP – Elevated, supports the diagnosis of heart failure.
  • Cardiac troponin – Detects myocardial injury or acute myocardial infarction.
  • ECG (Electrocardiogram) – Identifies arrhythmias, ischemia, or infarction.
  • Chest X-ray – Shows pulmonary edema, cardiomegaly, or pleural effusion.
  • Echocardiogram – Assesses cardiac structure, ejection fraction, and valvular function.
  • Blood tests: CBC, electrolytes, renal function (BUN/creatinine), liver function, glucose, and thyroid function (when indicated).
  • Arterial blood gas (ABG) – Evaluates oxygenation and acid–base status in severe respiratory distress.
  • Pulse oximetry – Monitors oxygen saturation continuously.

Diagnosis

Acute Heart Failure · Diagnostic Criteria — ESC 2021

Acute HF is a life-threatening medical emergency requiring rapid diagnosis and treatment. Diagnosis is clinical — based on symptoms + signs + investigations. No single test is diagnostic alone. Treat while investigating.
Symptoms
Dyspnea at rest or minimal exertion
Orthopnea (cannot lie flat)
Paroxysmal nocturnal dyspnea (PND)
Rapid deterioration over hours to days
Fatigue, reduced exercise tolerance
Ankle / leg swelling
Signs (examination)
Tachypnea (RR >20/min)
SpO₂ <90% on room air
Bilateral basal crackles (pulmonary oedema)
Elevated JVP — congestion marker
S3 gallop / displaced apex beat
Peripheral pitting oedema
Hepatomegaly / ascites (right HF)
Cool peripheries, prolonged CRT (low output)
Key investigations
BNP >100 pg/mL or NT-proBNP >300 pg/mL (rules in)
CXR: cardiomegaly, pulmonary vascular congestion, Kerley B lines, pleural effusion
Echo: reduced EF, wall motion abnormality, valve pathology, pericardial effusion
ECG: tachycardia, AF, LVH, Q waves, LBBB
Troponin: elevated if ischaemia or myocarditis is trigger
Clinical Profile Congestion Perfusion Haemodynamics Management focus
Warm & Dry No congestion Adequate perfusion Normal CO, normal PCWP Optimise oral therapy; not acute HF presentation
Warm & Wet Congested Adequate perfusion Normal CO, high PCWP Most common AHF. IV diuretics (furosemide), vasodilators, O₂
Cold & Wet Congested Hypoperfused Low CO, high PCWP Inotropes + diuretics; consider haemodynamic monitoring; ICU
Cold & Dry No congestion Hypoperfused Low CO, low/normal PCWP Cardiogenic shock / RV failure. Cautious fluids + inotropes; urgent echo
Investigations — mandatory workup on admission
Bloods
BNP / NT-proBNP — confirm HF, guide therapy
Troponin I or T — rule out ACS as precipitant
FBC — anaemia (common trigger)
U&E / Creatinine — baseline before diuretics
LFTs, TFTs, glucose — precipitant screen
ABG — if SpO₂ <90% or respiratory distress
Lactate — if low output / shock suspected
Imaging
CXR — cardiomegaly, Kerley B lines, bat-wing oedema, pleural effusions
Bedside echo (POCUS) — rapid EF, IVC, pericardial effusion
Formal TTE — within 48h if not already done
Lung POCUS — B-lines confirm pulmonary oedema (≥3 B-lines per zone)
Monitoring
12-lead ECG — rate, rhythm, LBBB, ischaemia, LVH
Continuous SpO₂ monitoring
Urine output — catheterise if severe; target >0.5 mL/kg/h
Daily weight — fluid balance tracking
Invasive haemodynamic monitoring (Swan-Ganz) if cardiogenic shock
Common precipitants — always search for and treat
Acute MI / ACS Atrial Fibrillation Infection / Sepsis Medication non-adherence Anaemia Hypertensive crisis Arrhythmia (VT/VF) Valve dysfunction (acute MR/AR) Pulmonary embolism Renal failure / fluid overload Thyroid storm Alcohol / cardiotoxins

Heart Failure With Reduced Ejection Fraction (HFrEF) Vs Heart Failure With Preserved Ejection Fraction (HFpEF)

Diagnosis · HFrEF vs HFpEF

HFrEF
EF < 40%
HFpEF
EF ≥ 50%
Ejection fraction
EF < 40% — systolic dysfunction confirmed
EF ≥ 50% — systolic function preserved
EF 40–49% = HFmrEF (grey zone)
Key echocardiographic findings
• Dilated LV (LVEDV ↑)
• Reduced wall motion (global hypokinesia)
• Thin LV walls (eccentric remodelling)
• MR ± TR (secondary)
• Normal or small LV cavity
• LVH — concentric remodelling
• Impaired relaxation: E/e′ >14, e′ <7 cm/s
• LA dilation (LAVi >34 mL/m²)
BNP / NT-proBNP
Markedly elevated
BNP >100 pg/mL
NT-proBNP >300 pg/mL
Elevated but often lower than HFrEF
BNP >35 pg/mL
NT-proBNP >125 pg/mL
Typical patient
Younger males; post-MI; dilated cardiomyopathy; alcoholic CM; chemotherapy-induced
Older females; hypertension, obesity, diabetes, atrial fibrillation; metabolic syndrome
ECG clues
LBBB Q waves Poor R progression
LV dilation pattern; AF common
LVH criteria AF
May be normal; ST changes of LVH strain
Auscultation
S3 gallop (volume overload); displaced apex beat; pansystolic murmur (MR)
S4 gallop (stiff LV); non-displaced apex; signs of pulmonary hypertension
Haemodynamics
• Low CO / CI (<2.2 L/min/m²)
• High LVEDP
• High PCWP (>18 mmHg)
• Normal CO at rest
• High LVEDP (diastolic)
• PCWP rises steeply on exertion
Mortality-reducing therapy
ACEi/ARB/ARNI β-blocker MRA SGLT2i
ICD/CRT if indicated
SGLT2i (dapagliflozin / empagliflozin)
Diuretics for congestion
No proven mortality benefit for RAAS/BB
Prognosis
Worse; 5-yr mortality ~50% without optimal therapy. EF may recover with treatment (HFrecEF).
Similar overall mortality to HFrEF; harder to treat; driven by comorbidities.
ESC 2021 — Minimum diagnostic criteria for HFrEF
Required (all 3 must be present)
Symptoms of HF (dyspnea, orthopnea, fatigue, ankle swelling)
Signs of HF (elevated JVP, pulmonary crackles, peripheral edema)
LVEF < 40% on echocardiography
Supportive findings
Elevated BNP / NT-proBNP
Structural abnormality on echo (LV dilation, wall motion abnormality)
Response to diuretic therapy
Causative etiology identified (ischemic, valvular, idiopathic)
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Management of Acute Heart Failure (AHF)

Immediate Management of Acute Heart Failure (AHF)

  • Airway, Breathing, Circulation (ABCs)
  • Supplemental oxygen if hypoxemic
  • Non-invasive ventilation (CPAP/BiPAP) for severe respiratory distress or pulmonary edema
  • Continuous cardiac and pulse oximetry monitoring
  • IV access and close monitoring of vital signs

Pharmacologic Treatment

  • IV loop diuretics (e.g., furosemide) for fluid overload
  • IV vasodilators (e.g., nitroglycerin) if blood pressure is adequate and congestion is present
  • Inotropes/vasopressors (e.g., dobutamine, norepinephrine) for cardiogenic shock or severe hypoperfusion
  • Treat the underlying cause (e.g., acute myocardial infarction, arrhythmia, infection, hypertensive emergency)

Ongoing Management for Acute Heart Failure (AHF)

  • Monitor urine output, daily weight, renal function, and electrolytes
  • Restrict sodium and fluids if indicated
  • Optimize guideline-directed heart failure medications once the patient is hemodynamically stable
  • Provide patient education and arrange appropriate follow-up to reduce the risk of readmission.

Complications of Acute Heart Failure (AHF)

      • Pulmonary edema leading to severe hypoxemia and respiratory failure
      • Cardiogenic shock
      • Cardiac arrhythmias (e.g., atrial fibrillation, ventricular arrhythmias)
      • Acute kidney injury (cardiorenal syndrome)
      • Myocardial ischemia or infarction
      • Thromboembolism (e.g., stroke or pulmonary embolism)
      • Multiorgan dysfunction/failure due to poor tissue perfusion
      • Death if not recognized and treated promptly
       
       

Prognosis of Acute Heart Failure (AHF)

    • Prognosis depends on the underlying cause, severity, age, comorbidities, and response to treatment.
    • Early diagnosis and prompt treatment improve outcomes and reduce complications.
    • Patients remain at high risk for recurrent hospitalizations and worsening heart failure.
    • Poor prognostic factors include cardiogenic shock, persistent hypotension, renal dysfunction, and reduced ejection fraction.
    • Long-term management, medication adherence, and lifestyle modifications are essential to improve survival and quality of life.

Key Points / Clinical Pearls of Acute Heart Failure (AHF)

  • Acute Heart Failure (AHF) is the sudden onset or rapid worsening of heart failure symptoms and is a medical emergency.
  • The hallmark symptom is acute dyspnea, often due to pulmonary edema.
  • Prompt assessment of airway, breathing, and circulation (ABCs) is essential.
  • IV loop diuretics are the mainstay of treatment for patients with fluid overload.
  • Identify and treat the underlying cause (e.g., myocardial infarction, arrhythmia, infection, hypertensive emergency).
  • Monitor oxygenation, vital signs, urine output, renal function, and electrolytes closely.
  • Early recognition and timely intervention reduce complications, rehospitalization, and mortality.