HEART FAILURE

Overview of Heart Failure (HF)

• Definition: Heart failure is defined not as a specific disease, but as a clinical syndrome characterized by impaired cardiac pumping or filling. In this state, the heart is incapable of producing an adequate cardiac output ($CO$) to meet the body's metabolic requirements.

• Key Physiological Formulas:

  • Cardiac Output: $CO = SV \times HR$

  • Normal Systemic Cardiac Output: $4-8\,dm^3/min$

  • Blood Pressure: $BP = CO \times SVR$

• Epidemiology and Statistics:

  • Approximately $5 \times 10^6$ (5 million) Americans are currently affected by HF.

  • It represents the most common reason for hospitalization in adults over the age of $65$ years.

• Primary Associations: HF is most commonly associated with long-standing hypertension ($HTN$), Coronary Artery Disease ($CAD$), and Myocardial Infarction ($MI$).

• Core Characteristics:

  • Ventricular dysfunction.

  • Reduced exercise tolerance.

  • Diminished quality of life.

  • Shortened life expectancy.

Etiology and Risk Factors

• Primary Risk Factors:

  • Coronary Artery Disease (CAD): The leading cause of heart failure.

  • Advancing Age.

• Hypertension (HTN): Acting as a major contributing factor, it increases the risk of HF approximately $3 \times$. The risk increases in direct proportion to the severity of the hypertension.

• Diabetes Mellitus: This condition predisposes individuals to HF regardless of whether CAD or HTN is present.

• Secondary Contributing Factors:

  • Tobacco use.

  • Obesity.

  • High serum cholesterol levels.

Types of Heart Failure: Systolic vs. Diastolic vs. Mixed

• Systolic Failure (HFrEF - Heart Failure with Reduced Ejection Fraction):

  • Hallmark: A decreased ejection fraction where EF < 50\%.

  • Mechanisms: Result of impaired contractility (e.g., following an MI), increased afterload (e.g., chronic HTN), cardiomyopathy, or valvular disease.

• Diastolic Failure (HFpEF - Heart Failure with Preserved Ejection Fraction):

  • Mechanism: Characterized by the impaired ability of the ventricles to relax and fill during diastole.

  • Hemodynamics: Results in decreased stroke volume and CO; however, the ejection fraction ($EF$) remains within normal ranges.

  • Causes: Left ventricular ($LV$) hypertrophy resulting from chronic HTN, aortic stenosis, or hypertrophic cardiomyopathy.

  • Diagnosis Criteria: Based on the presence of pulmonary congestion, pulmonary hypertension, and ventricular hypertrophy in the context of a normal $EF$.

• Mixed Failure (Dilated Cardiomyopathy):

  • Characteristics: Extremely poor ejection fraction (EF < 35\%).

  • Clinical Presentation: High pulmonary pressures and biventricular failure (where both ventricles are dilated, resulting in poor filling and emptying).

Compensatory Mechanisms in Heart Failure

• Sympathetic Nervous System (SNS) Activation: An immediate response that increases heart rate and contractility to maintain $CO$.

• Neurohormonal Response (RAAS):

  • The kidneys sense decreased perfusion and release renin.

  • Renin converts angiotensinogen to angiotensin I.

  • Angiotensin-converting enzyme ($ACE$) in the lungs converts angiotensin I to angiotensin II.

  • Angiotensin II triggers aldosterone release (leading to $Na^+$ and $H_2O$ retention) and causes peripheral vasoconstriction to increase $BP$.

• Ventricular Dilation: The chambers of the heart enlarge to accommodate larger volumes of blood.

• Ventricular Hypertrophy: The walls of the ventricles thicken in response to overwork. While this initially helps, it significantly increases the risk for ventricular dysrhythmias.

Left-Sided Heart Failure (Most Common)

• Etiology: Caused by left ventricular dysfunction arising from MI, hypertension, CAD, or cardiomyopathy.

• Mechanism: Blood backs up into the left atrium and pulmonary veins, leading to pulmonary symptoms.

• Signs/Symptoms and Mechanisms:

  • Paroxysmal Nocturnal Dyspnea (PND): Caused by fluid redistribution from the lower extremities to the lungs when lying flat at night.

  • Orthopnea: Difficulty breathing when lying flat; relieved only by sitting upright.

  • Exertional Dyspnea: Inability to meet oxygen demands during physical activity.

  • Pulmonary Congestion: Presenting as cough, crackles, wheezes, and blood-tinged sputum due to fluid in the alveoli.

  • Tachycardia: A compensatory response to maintain $CO$ as stroke volume drops.

  • Tachypnea: Increased respiratory rate to compensate for poor oxygenation.

  • Elevated Pulmonary Capillary Wedge Pressure: A clinical indicator of elevated left-sided heart pressures.

  • Cerebral Effects: Restlessness, confusion, and decreased memory due to cerebral hypoperfusion.

  • Peripheral Effects: Cyanosis and fatigue due to decreased $O_2$ delivery to the tissues.

Right-Sided Heart Failure

• Etiology: Most commonly caused by pre-existing left-sided HF, Cor Pulmonale, or a right ventricular MI.

• Mechanism: Blood backs up into the right atrium and the systemic venous circulation.

• Signs/Symptoms and Mechanisms:

  • Jugular Venous Distention (JVD): Result of increased venous pressure.

  • Hepatomegaly and Splenomegaly: Venous congestion occurring within the abdominal organs.

  • GI Distress: Vascular congestion of the GI tract leading to anorexia and nausea.

  • Peripheral Edema: Fluid accumulation in dependent areas (legs, ankles, sacrum).

  • Ascites: Fluid accumulation within the peritoneal cavity (abdomen).

  • Weight Gain: Significant fluid retention; a gain of > 3\,lbs ($1.36\,kg$) in $2$ days must be reported.

  • Fatigue: Caused by reduced $CO$ and subsequent tissue hypoperfusion.

• Cor Pulmonale: Right-sided HF specifically caused by a primary respiratory disorder, most commonly Chronic Obstructive Pulmonary Disease ($COPD$). Pulmonary hypertension is typically a pre-existing condition in these cases.

Clinical Manifestations: Chronic Heart Failure

• Fatigue: The most common symptom; directly related to decreased cardiac output.

• Respiratory: Dyspnea, orthopnea, and PND due to pulmonary congestion.

• Cough: A persistent dry cough that remains unrelieved by position changes or over-the-counter suppressants.

• Tachycardia: Compensation for low stroke volume.

• Edema: Dependent, pitting edema in the lower extremities.

• Nocturia: Increased renal perfusion at rest allows for the redistribution and excretion of fluid accumulated during the day.

• Skin Changes: Skin may appear dusky, cool, and damp to the touch.

• Neurological: Restlessness and confusion due to hypoperfusion of the brain.

• Chest Pain (Angina): Resulting from decreased myocardial perfusion.

• Weight Gain: Defined as $3+\,lbs$ ($1.36+\,kg$) in $2$ days or $3-5\,lbs$ ($1.36-2.27\,kg$) in $1$ week.

Acute Decompensated Heart Failure (ADHF)

• Pulmonary Edema: The hallmark of ADHF; considered a life-threatening emergency.

• Progression of Pulmonary Edema:

  • Early Stage: Increased respiratory rate; decreased $PaO_2$.

  • Late Stage: Tachypnea; frothy, blood-tinged sputum; respiratory acidemia (decreased ventilation leading to increased blood $CO_2$).

• Physical Findings:

  • Use of accessory muscles for breathing (indicating severe respiratory effort).

  • Cyanosis (indicating severe hypoxia).

  • Cool, clammy skin due to peripheral vasoconstriction.

  • Crackles, wheezes, and rhonchi in the airways.

  • Hypotension or Hypertension depending on the severity and compensatory state.

Complications of Heart Failure

• Pleural Effusion: Excess fluid between the pleural layers of the lungs.

• Atrial Fibrillation: The single most common dysrhythmia associated with HF.

• Fatal Dysrhythmias: High risk of sudden cardiac death or Ventricular Tachycardia ($V\text{-tach}$) when EF < 35\%.

• Hepatomegaly: Severe right ventricular failure can lead to liver fibrosis and eventually cirrhosis.

• Renal Insufficiency: Progression toward renal failure due to chronic hypoperfusion.

Diagnostic Studies and BNP Interpretation

• Primary Goal: Determine and treat the underlying cause of the failure.

• Diagnostic Tools:

  • History and physical examination.

  • Chest X-ray and Electrocardiogram ($ECG$).

  • Lab studies: Cardiac enzymes, serum/urine electrolytes, Arterial Blood Gases ($ABGs$), and $SpO_2$.

  • Hemodynamic assessments: Vital signs, pulse, and respiratory rate.

  • Echocardiogram and Stress testing.

  • Cardiac Catheterization to measure Ejection Fraction.

• B-Type Natriuretic Peptide (BNP) Levels:

  • < 100\,pg/dm^3: HF is highly improbable; seek other causes for symptoms.

  • $100-500\,pg/dm^3$: HF is probable; further evaluation is required.

  • > 500\,pg/dm^3: HF is highly probable; treat aggressively.

Classification Systems

NYHA Functional Classification

• Class I: No limitation of physical activity. Ordinary activity does not cause symptoms.

• Class II: Slight limitation of physical activity. Comfortable at rest, but ordinary activity results in symptoms.

• Class III: Marked limitation of physical activity. Comfortable at rest, but less-than-ordinary activity causes symptoms.

• Class IV: Inability to carry on any physical activity without discomfort. Symptoms are present even at rest.

ACC/AHA Stages of Heart Failure

• Stage A: High risk for HF, but no structural heart disease or symptoms. Focused on prevention.

• Stage B: Structural heart disease present, but the patient has no symptoms of HF.

• Stage C: Structural heart disease present with prior or current symptoms of HF.

• Stage D: Refractory HF/unmanageable HF requiring specialized interventions (e.g., transplant).

Collaborative Management: Chronic HF

Overall Treatment Goals

• Decrease patient symptoms and improve quality of life.

• Improve $LV$ function and reverse ventricular remodeling.

• Decrease mortality and morbidity.

• Maximize $CO$ and preserve target organ function.

Non-Pharmacologic Therapies

• Oxygen Administration: To maintain adequate oxygenation levels.

• Rest: Physical and emotional rest to decrease cardiac workload.

• Cardiac Resynchronization Therapy (CRT): Biventricular pacing to improve the synchrony of ventricular contractions.

• Mechanical Support: Intraaortic Balloon Pump ($IABP$) or Ventricular Assist Devices ($VADs$). $VADs$ may be used as a bridge to transplant or as destination therapy.

• Cardiac Transplantation: Reserved for end-stage HF (Stage D).

Drug Therapy for Heart Failure

• Diuretics: Used to reduce preload and mobilize edema.

  • Thiazide (HCTZ): First choice for chronic HF; convenient and effective.

  • Loop (Furosemide/Lasix): Most potent; used in ER settings for acute fluid overload.

  • Spironolactone (Aldactone): Potassium-sparing diuretic. Requires monitoring for hyperkalemia.

  • Note: Monitor for hypokalemia (fatigue, anorexia, vomiting, palpitations) with loop and thiazide diuretics.

• ACE Inhibitors: First-line for systolic dysfunction. Decreases afterload. Side effects include dry cough and hyperkalemia. Contraindicated in pregnancy. Examples: Lisinopril, Enalapril, Captopril.

• ARBs (Angiotensin II Receptor Blockers): Used when ACE inhibitors are not tolerated. Takes $2-4$ weeks for full effect. Examples: Losartan, Valsartan.

• Aldosterone Antagonists: e.g., Spironolactone. Requires potassium monitoring.

• Nitrates + Hydralazine (Apresoline): Provides vasodilation for long-term management. Example: BiDil (isosorbide dinitrate + hydralazine).

• Beta-adrenergic Blockers: Decrease heart rate and improve $EF$ long-term. Examples: Carvedilol (Coreg), Metoprolol.

• Digoxin (Lanoxin): Positive inotrope that strengthens contractions while decreasing HR via the AV node.

• Calcium Sensitizers: e.g., Levosimendan; used specifically in acute HF.

Digoxin Nursing Priorities

• Assessment: Take the APICAL pulse for one full minute before administration.

• Withholding: Hold the medication if the heart rate is < 60\,bpm.

• Monitoring: Check Digoxin levels and serum potassium. Hypokalemia significantly increases the risk of digoxin toxicity.

• Therapeutic Level: $0.5 - 2.0\,ng/cm^3$.

• Toxicity Signs: GI symptoms (anorexia, nausea) and visual disturbances.

Nutritional Therapy and Nursing Management

• Sodium Restriction: Usually restricted to $2.5\,g$ per day.

• Fluid Restriction: Not generally required for standard HF patients.

• DASH Diet: Recommended (Dietary Approaches to Stop Hypertension).

• Daily Weight Protocol: Weigh at the same time and with the same clothing each day. Report gains of $3\,lbs$ in $2$ days or $3-5\,lbs$ in $1$ week.

• Nursing Diagnoses: Activity intolerance, Fluid volume excess, Impaired gas exchange, Anxiety, Deficient knowledge.

• Interventions: Restrict salt, conserve patient energy, and utilize support systems.

• Patient Education:

  • Medications are lifelong; emphasize compliance.

  • Teach the patient how to monitor their own pulse rate and when to withhold medications (e.g., Digoxin, Beta-blockers).

  • Home Blood Pressure monitoring.

  • Recognizing signs of hypokalemia and hyperkalemia.

  • Adopting energy-efficient behaviors.

• Evaluation Parameters: Improved respiratory status ($O_2$ sat), stabilized fluid balance (weight, edema, I&O), increased activity tolerance, and demonstrated knowledge of the disease.