Congestive Heart Failure

Epidemiology

• Prevalence in the United States: 1%–2%
• More common in men
• Prevalence in African Americans is 25% higher than in Caucasians.
• Incidence and prevalence increase steeply with age.
• Most common cause of hospitalization in patients > 60 years of age

Etiology

Underlying conditions include:

• Hypertension
• Coronary artery disease 
• Diabetes mellitus
• Myocardial infarction (MI)
• Cardiomyopathy
• Left ventricular hypertrophy
• Pulmonary hypertension
• Cor pulmonale (e.g., chronic obstructive pulmonary disease)
• Valvular heart diseases (e.g., aortic stenosis)
• Renal failure
• Pericardial diseases (e.g., constrictive pericarditis)
• Myocarditis
• Hemochromatosis
• Amyloidosis
• Arrhythmias (e.g., bradyarrhythmias, tachyarrhythmias)

Risk factors include:

• Substance abuse (e.g., ethanol, cocaine)
• Smoking
• Obesity
• Sedentary lifestyle

Pathophysiology

• Congestive heart failure (CHF) can be due to systolic or diastolic dysfunction.
  • Systolic heart failure: impaired myocyte contractility and dilated heart → reduced stroke volume and ejection fraction 
    • Also known as reduced ejection fraction heart failure or HFrEF
  • Diastolic heart failure: inadequate relaxation and filling of the hypertrophied heart but normal myocyte contractility → preserved ejection fraction despite low stroke volume
    • Also known as preserved ejection fraction heart failure or HFpEF
• Compensatory mechanisms induced by decreased cardiac output:
  • Activation of the sympathetic nervous system
  • ↑ Oxygen demand
  • Activation of the renin-angiotensin-aldosterone system
  • ↑ Antidiuretic hormone release
  • ↑ Atrial natriuretic peptide/brain natriuretic peptide (BNP) release
  • Cardiac remodeling/hypertrophy
• Initially, these adaptations can increase cardiac output and prevent the development of symptoms (compensated CHF).
• Over time, hypertrophy decreases lumen size and fails to increase contractility → exacerbation of CHF due to increased oxygen demand and decreased contractility → decompensated CHF
• Acute decompensated CHF is usually due to myocardial ischemia (e.g., MI).

Clinical Manifestations

Symptoms of CHF

• Chest pain
• Dyspnea (exertional early)
• Orthopnea
• Paroxysmal nocturnal dyspnea
• Hypotension 
• Syncope
• Fatigue
• Confusion
• Palpitations
• Dizziness
• Cough
• Exercise intolerance
• Unintentional weight loss

Signs of CHF

• S3 heart sound (low-pitched sound in early diastole)
• Crackles or rales on lung examination
• Tachycardia
• Displaced apical beat
• Jugular venous distension
• Tender/painful hepatosplenomegaly
• Nutmeg liver
• Symmetric edema
• Cyanosis
• Refractory volume overload
• Pitting edema
• Hemosiderin-laden macrophages

New York Heart Association (NYHA) functional classification

• Class I: no limitations of physical activity
• Class II: comfortable at rest but slight limitation during moderate/prolonged physical activity
• Class III: comfortable only at rest. Daily activities such as dressing result in marked limitations of physical activity.
• Class IV: symptomatic even at rest

American Heart Association classification

• Stage A: high risk for heart failure but without structural heart disease, objective evidence of cardiovascular disease, or symptoms of heart failure
• Stage B: structural heart disease/objective evidence of minimal cardiovascular disease but without signs or symptoms of heart failure
• Stage C: structural heart disease/objective evidence of moderate to severe cardiovascular disease with prior or current symptoms of heart failure
• Stage D: refractory heart failure/objective evidence of severe cardiovascular disease requiring specialized interventions

Diagnosis

• Evaluate preexisting conditions and reversible causes of heart dysfunction.
  • Thyroid function tests: Hyperthyroidism and hypothyroidism can lead to severe heart failure or contribute to the severity of existing heart failure.
  • CBC: Anemia can cause high output cardiac failure.
  • Fasting glucose: Diabetes mellitus is a common comorbidity.
• Initial workup should include:
  • Blood urea nitrogen/creatinine: > 20 = prerenal failure → worse prognosis
  • Electrolytes: hyponatremia → worse prognosis
  • Albumin: hypoalbuminemia → worse prognosis
  • Bilirubin: elevated total bilirubin → worse prognosis
  • Serum aminotransferase levels: reflect liver function
  • BNP/pro-BNP levels: high sensitivity and predictive value
  • Electrocardiogram (ECG): can show increased QRS voltage in leads I and aVL, Q waves, ST and T wave abnormalities in patients with prior MI or with cardiomyopathy
  • Chest X-ray (CXR): can show cardiomegaly (cardiac size to thoracic size ratio > 0.5), pulmonary edema, pleural effusion, pulmonary vascular congestion, Kerley B lines
• If labs, CXR, and ECG support CHF diagnosis, continue workup:
  • Transthoracic echocardiogram: measure ejection fraction and assess cardiac anatomy over time
  • Cardiac stress test: can assess functional impairment due to CHF
  • Multigated acquisition scan (radionuclide ventriculography): most accurate way to assess ejection fraction but is rarely done
    • Example of when to perform: A patient is receiving doxorubicin for chemotherapy. You are planning to administer a maximum dose of the drug, but need to make sure it is not causing cardiomyopathy.
• Diagnosis is made based on 4 criteria:
  1. Clinical evaluation confirming severe symptoms
  2. Episodes of refractory fluid retention and/or hypoperfusion
  3. Evidence of severe cardiac dysfunction on echocardiogram (or right heart catheterization)
  4. Evidence of severe impairment of functional capacity

A good mnemonic to remember these findings on CXR is ABCDE:

• A: alveolar edema (batwing)
• B: Kerley B lines
• C: cardiomegaly
• D: dilated upper lobe vessels
• E: pleural effusion

Treatment

Management of acute decompensated heart failure

• Furosemide: treats pulmonary edema or acute volume overload 
• Morphine: decreases preload and pain
• Nitroglycerin: decreases preload/oxygen demand 
• Oxygen: treats dyspnea/hypoxia
• Position patient upright 
• If refractory: 
  • IV nitroprusside/hydralazine
  • Sympathomimetics (dobutamine, dopamine, milrinone)

Long-term management of HF

Lifestyle modifications decrease mortality in cases of preserved ejection fraction heart failure.

• Weight loss
• Exercise (contraindicated if decompensating)
• Restriction of sodium to 3 g/day
• Restriction of fluids to 1.5–2 L/day in volume overload/edema
• Cessation of smoking and alcohol consumption
• Pneumococcal polysaccharide (PPSV23) vaccine (patients with CHF are more susceptible to pneumococcal pneumonia)

Pharmacological management

• Diuretics: Loop/thiazide
  • Indication: class I–IV (symptomatic): first line
  • Symptomatic management 
  • No improvement in prognosis/does not decrease mortality
• Renin-angiotensin-aldosterone blockers:
  • Angiotensin-converting-enzyme (ACE) inhibitors:
    • Indications: post-MI, asymptomatic with ejection fraction (EF) < 40%, symptomatic class II–IV, diabetes, hypertension
    • Mechanism: decrease preload and afterload by lowering oxygen demand
    • Prevent cardiac remodeling →  decreases mortality
  • Angiotensin II receptor blocker (ARB):
    • For patients with contraindication or intolerance to ACEIs
    • Avoid combination with ACEIs
    • Can be combined with angiotensin receptor-neprilysin inhibitors: valsartan/sacubitril
      • For persistent symptoms despite ACE/ARB
      • Neprilysin is an endopeptidase that breaks down BNP 
• Beta blockers:
  • Indications: class I–III, EF < 40%, post-MI
  • Contraindicated in acute decompensated HF due to negative inotropic/chronotropic effects
  • Use after stabilizing by ACEIs/ARBs
  • Decreases mortality
• Aldosterone receptor antagonist (spironolactone, eplerenone)
  • Indication: class II–IV (symptomatic), EF < 35%
  • Add on with ACEI, beta blockers, and diuretics
  • Decreases mortality
• Second-line medications:
  • Relieve symptoms and decrease hospitalizations
  • Do not affect mortality

Invasive procedures

• Implantable cardiac defibrillator can decrease mortality.
  • Primary prevention of arrhythmia: patients with EF < 35% and prior MI/CHF
  • Secondary prevention of arrhythmia: patients with a history of ventricular arrhythmias or sudden cardiac arrest
• A biventricular pacemaker can be placed in patients with EF < 35%, QRS width > 120 milliseconds, dilated cardiomyopathy, or severe left bundle branch block.
• Coronary revascularization (percutaneous transluminal coronary angioplasty or coronary artery bypass surgery) in patients with coronary artery disease
• Cardiac transplantation in patients with NYHA IV, EF < 20%, if no other options are available.

Mnemonic

To recall the management of acute heart failure or exacerbation of CHF, remember LMNOP:

• Lasix/Loop diuretic
• Morphine
• Nitroglycerin
• Oxygen
• Position or Prop up the patient

Clinical Relevance

The following conditions are risk factors and/or causes of congestive heart failure:

• Hypertension: blood pressure that is higher than > 130 mm Hg in systole and > 80 mm Hg in diastole. It is a risk factor of secondary diseases such as stroke, CHF, and cardiac insufficiency
• Diabetes mellitus: a heterogeneous group of metabolic diseases whose basic feature is chronic hyperglycemia with subsequently elevated sugar contents in the urine
• Coronary heart disease: the leading cause of death worldwide. It is a condition that occurs as a result of atherosclerotic changes of the coronary arteries with subsequent narrowing of the vessels, preventing their dilation. 
• Myocardial infarction: ischemia of the myocardial tissue due to a complete obstruction or drastic constriction of the coronary artery. This is usually accompanied by an increase in cardiac enzymes, typical ECG changes (ST elevations), and chest pain.
• Ventricular fibrillation: a type of ventricular tachyarrhythmia often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The heartbeat is uncoordinated, resulting in a decrease in cardiac output and immediate hemodynamic collapse. 
• Cardiomyopathy: a group of myocardial diseases associated with impaired systolic and diastolic function. The World Health Organization classifies 5 types based on cardiac changes: dilated, hypertrophic nonobstructive or obstructive, restrictive, arrhythmogenic right ventricular, and unclassified cardiomyopathies. 
• Myocarditis: an inflammatory disease of the heart muscle that mostly arises due to infections with cardiotropic viruses, especially infections with the coxsackievirus
• Atrial fibrillation: the most common form of supraventricular arrhythmia. Chronic AF increases the risk of thromboembolic events, especially for individuals in advanced age. AF reduces quality of life and increases mortality in affected individuals.
• Amyloidosis: a disorder caused by extracellular deposition of insoluble abnormal amyloid fibrils that alter the function of tissues. Amyloid is a protein produced in the bone marrow and can be deposited in any organ.
• Hemochromatosis: a genetic autosomal recessive disorder that occurs as a result of genetic mutations of certain genes (e.g., HFE gene) involved in the metabolism of iron, resulting in increased intestinal iron absorption
• Cor pulmonale: the abnormal enlargement of the right ventricle as a result of primary disease of the lungs or the pulmonary blood vessels
• Obesity: a disorder involving excessive body fat deposition that increases the risk of health problems such as cardiovascular diseases, sleep apnea, and type II diabetes. It is measured using the body mass index.
• Aortic stenosis: a condition characterized by narrowing of the aortic valve, in which the left ventricle has to use more strength to maintain the cardiac output against the pathologically increased pressure gradient of the valve. This results in concentric hypertrophy of the left ventricle. Long term, this creates a diastolic dysfunction.
• Hyperthyroidism: Hyperthyroidism is caused by an excess of thyroid hormones T3 and T4. Clinical features are mostly due to the increased body’s metabolic rate. Hyperthyroidism can lead to severe HF or contribute to the severity of HF due to other common causes. Therefore, thyroid function should be assessed and corrected before classifying HF as advanced.
• Hypothyroidism: Hypothyroidism is caused by the deficiency of the T3 and T4 hormones. Clinical features are primarily due to the accumulation of matrix substances and a decreased metabolic rate. Hypothyroidism can lead to severe HF or contribute to the severity of HF due to other common causes. Therefore, thyroid function should be assessed and corrected before classifying HF as advanced.
• Obstructive sleep apnea: Obstructive sleep apnea is a disorder characterized by recurrent obstruction of the upper airway during sleep, which causes hypoxia and fragmented sleep. Sleep-disordered breathing is common in patients with HF and can impair systolic and diastolic cardiac function. The presence of obstructive sleep apnea in patients with HF is associated with a worse prognosis. 
• Anemia: Severe anemia is defined as hemoglobin < 8 mg/dL and can result in impaired oxygen delivery to tissues. This may contribute to symptoms such as dyspnea and fatigue in patients with suspected advanced HF. Treatment of the anemia may improve HF symptoms.