heart failure 

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  • Copyright © 2017, 2014, 2010, 2007, 2004, 2000, Mosby, Inc., an affiliate of Elsevier Inc. All Rights Reserved.

Objective

  • Describe the etiology, pathophysiology, clinical manifestations, drug therapy, and collaborative care of heart failure.

Definition of Heart Failure

  • Heart failure (HF) is an abnormal condition involving impaired cardiac pumping.
  • Results in the inability of the heart to provide sufficient blood to meet the oxygen needs of tissues and organs.
  • Decreased cardiac output (CO) leads to:
      - Decreased tissue perfusion
      - Impaired gas exchange
      - Fluid volume imbalance
      - Decreased functional ability
  • This chronic slow process ultimately leads to further complications.

Cardiac Output

  • Heart failure is characterized by the heart's inability to produce adequate cardiac output.
  • Cardiac output formula:
      - CO=extStrokeVolumeimesextHeartRateCO = ext{Stroke Volume} imes ext{Heart Rate}
  • Components of stroke volume estimation:
      - Ejection Fraction (EF): Percentage of blood ejected by the left ventricle with each heartbeat.
        - Normal range is 60% to 70%.
      - Preload: The force that stretches the cardiac muscle prior to contraction.
      - Afterload: Pressure that the heart has to pump against; influences the volume ejected each beat.
        - If ventricular filling is compromised, the ventricle may begin to fail.

Anatomy of the Heart

  • Blood Flow Through the Heart:
      - Superior Vena Cava ➔ Right Atrium ➔ Tricuspid Valve ➔ Right Ventricle ➔ Pulmonary Artery ➔ Lungs ➔ Pulmonary Veins ➔ Left Atrium ➔ Mitral Valve ➔ Left Ventricle ➔ Aortic Valve ➔ Aortic Arch.
  • Reference Figure: Blood flow anatomy as illustrated in clinical textbooks.

Etiology of Heart Failure

  • Primary Causes:
      - Coronary artery disease (CAD)
      - Hypertension
      - Rheumatic heart disease
      - Congenital heart defects
      - Pulmonary Hypertension
      - Hyperthyroidism
      - Cardiomyopathy
  • Primary Risk Factors:
      - Anemia
      - Tobacco use
      - Infection
      - Dysrhythmias
      - Diabetes
      - Obesity
  • These factors can exacerbate cardiac workload and contribute to heart failure.

Pathophysiology of Heart Failure

  • Discussion of various forms of heart failure includes right-sided, left-sided, systolic, and diastolic heart failure.

Forms of Heart Failure

  • Left-Sided Heart Failure:
      - Most common form of heart failure.
      - Results from the inability of the left ventricle (LV) to:
        - Empty adequately during systole
        - Fill adequately during diastole
      - Causes blood backup into the left atrium and pulmonary veins, leading to pulmonary congestion and edema.
      - Further classified into:
        - Systolic Heart Failure (HFrEF): Characterized by decreased ejection fraction (EF < 40%), commonly caused by impaired contractility (e.g., myocardial infarction), increased afterload (e.g., hypertension), or mechanical abnormalities (e.g., valve disease).
        - Diastolic Heart Failure (HFpEF): Characterized by impaired ventricular relaxation and decreased filling due to stiffness, commonly caused by hypertension. Patients generally maintain a normal ejection fraction.

Right-Sided Heart Failure

  • Occurs when the right ventricle does not pump effectively, leading to fluid backup into the venous system and peripheral tissues.
  • Most common cause of right heart failure is left heart failure, where fluid accumulates in pulmonary circulation, complicating right ventricular function. Other causes include right ventricular (RV) infarction, pulmonary embolism (PE), and cor pulmonale.

Ventricular Adaptations

  • Dilation: Enlargement of heart chambers in response to sustained pressure over time.
      - Initially adaptive but can lead to overstretching and cardiac exhaustion.
  • Hypertrophy: Increase in muscle mass due to overwork, also adaptive initially but reduces contractility and increases oxygen demands over time, leading to further complications.
  • Remodeling: Changes in cardiac structure in response to volume overload or injury, affecting heart function.

Counter-Regulatory Processes

  • In heart failure, natriuretic peptides (e.g., Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP)) are released in response to ventricular pressure and volume overload.
  • Functions include:
      - Promoting vasodilation
      - Enhancing diuresis
      - Inhibiting cardiac hypertrophy
      - Chronic heart failure can deplete these regulatory factors.

Clinical Manifestations

  • Common Symptoms:
      - Fatigue
      - Limited activity
      - Chest congestion and cough
      - Edema
      - Shortness of breath
  • These symptoms are often summarized in the FACES acronym (Fatigue, Activity limitations, Chest congestion, Edema, Shortness of breath).

Complications of Heart Failure

  • Common Complications:
      - Fluid volume overload
      - Pleural effusion
      - Pulmonary edema
      - Atrial fibrillation (most common dysrhythmia), which can reduce cardiac output by 10%-20% and increases stroke risk
      - High risk of fatal dysrhythmias (sudden cardiac death, ventricular tachycardia) with ejection fraction < 35%
      - Hepatomegaly, with potential for fibrosis or cirrhosis
      - Renal insufficiency or failure due to decreased perfusion.

Diagnostic Studies

  • Diagnostic Approaches:
      - History and physical examination
      - Chest X-ray
      - Electrocardiogram (ECG)
      - Laboratory studies (cardiac enzymes, BNP levels)
      - Hemodynamic assessment
      - Echocardiogram to evaluate ejection fraction
      - Cardiac catheterization
  • The primary goal is to determine the underlying cause of heart failure.

Classification of Heart Failure

  • New York Heart Association Functional Classification:
      - Classes I to IV, based on symptom severity.
  • ACC/AHA Staging System:
      - Stages A to D, indicating progression of disease.

Collaborative Management of Heart Failure

  • Pharmacotherapy:
      - ACE Inhibitors: First-line for HFrEF; reduce afterload.
      - ARBs: For those who cannot tolerate ACE inhibitors.
      - Spironolactone: A potassium-sparing diuretic that prolongs survival in HF; requires monitoring of potassium levels and renal function.
      - Beta-blockers: Directly block negative SNS effects on the failing heart.
      - Digitalis (Digoxin): Mildly increases contractility; hold for heart rate below 60 bpm, side effects include hypotension and gastrointestinal disturbance.

Non-Pharmacological and Advanced Management

  • Advanced Therapies:
      - Cardiac Resynchronization Therapy (CRT)
      - Intra-aortic balloon pump (IABP)
      - Ventricular assist devices (VADs) for temporary or long-term assistance.
  • Home Care Recommendations:
      - Daily weight monitoring.
      - Contact healthcare provider for significant weight gain (3 lbs in 2 days or 3-5 lbs in a week) or increased symptoms (dyspnea, angina).

Nutritional Therapy

  • Dietary Recommendations:
      - Individualized and culturally sensitive.
      - Dietary Approaches to Stop Hypertension (DASH) diet recommended.
      - Sodium intake typically restricted to 2.3 g/day.

Acute Decompensated Heart Failure

  • Physical Findings:
      - Orthopnea, tachypnea, cyanosis, cool and clammy skin, cough with frothy blood-tinged sputum, crackles, wheezes, and rhonchi.
      - Can lead to pulmonary edema, which may be life-threatening.
  • Treatment includes ICU monitoring, diuretics, and vasodilators.

References

  • Various cited works relevant to heart failure, notably texts by Huether, McCance, and Lewis et al., focusing on pathophysiology and nursing management.