Cardiac Pathophysiology: Heart Failure Quiz

Cardiac Pathophysiology: Heart Failure and Arrhythmias

• Heart failure is a complex syndrome resulting from structural or functional cardiac disorders that impair the ventricle's ability to fill with or eject blood.
• Ejection Fraction (EF) is the amount of blood pumped out of the ventricle divided by the total amount of blood in the ventricle (EF=SV/EDV).
• EF is crucial in heart failure, impacting prognosis and patient selection in clinical trials. Patients with HFrEF (systolic HF) often have EF ≤35% or ≤40%.
• Heart failure can involve systolic dysfunction (impaired contraction) or diastolic dysfunction (impaired relaxation). These often coexist.

Heart Failure Classification

• Heart failure is classified by ejection fraction (EF):
  • HFrEF (Heart failure with reduced EF): LVEF ≤ 40%
  • HFimpEF (HF with improved EF): Previous LVEF ≤ 40% and follow-up LVEF > 40%
  • HFmrEF (HF with mildly reduced EF): LVEF 41-49%
  • HFpEF (HF with preserved EF): LVEF ≥ 50%

Etiologies of Heart Failure

• HFrEF (Systolic HF):
  • Reduction in muscle mass
  • Myocardial infarction
  • Dilated cardiomyopathy
  • Infection; Ethanol; Cardiotoxins
  • Progression from Ventricular Hypertrophy
  • Pressure Overload (Hypertension, Aortic Stenosis, Volume Overload)
  • Valvular Regurgitation
• HFpEF (Diastolic HF):
  • Increased Ventricular Stiffness
  • Ventricular Hypertrophy from pressure overload (Hypertension, Aortic Stenosis)
  • Infiltrative Myocardial Disease
  • Myocardial Infarction
  • Pericardial Disease

Heart Failure Symptoms

• Respiratory Symptoms:
  • DOE (Dyspnea on exertion)
  • Orthopnea (dyspnea in the supine position)
  • PND (Paroxysmal nocturnal dyspnea)
• Other Symptoms:
  • Cerebral symptoms (confusion, difficulty concentrating, headache, insomnia, anxiety)
  • Nocturia (urination at night)
  • Fatigue and weakness
  • Abdominal symptoms (anorexia, nausea, abdominal discomfort/fullness)

Heart Failure Classification (NYHA)

• NYHA Class I: No limitation of physical activity.
• NYHA Class II: Slight limitation of activity.
• NYHA Class III: Marked limitation of activity.
• NYHA Class IV: Severe limitation of activity.

Physical Signs of Heart Failure

• Signs of poor cardiac output:
  • Cyanosis (pale/blue skin)
  • Diaphoresis (sweating)
  • Cool extremities
  • Tachypnea (fast breathing rate)
  • Tachycardia (fast heart rate)
• Auscultation:
  • Pulmonary rales
  • Pleural effusions
  • Loud P2 component of the second heart sound (S2)
  • Third heart sound (S3)
  • Fourth heart sound (S4)
• Signs of excess volume:
  • Jugular venous distention
  • Hepatomegaly (enlarged liver)
  • Hepato-jugular reflux
  • Peripheral edema

Diagnostic Tests

• Chest X-ray: Cardiomegaly (cardiothoracic ratio > 0.5) or pulmonary edema (cloudlike appearance)
• Echocardiography: Assess left ventricular (LV) systolic function and ejection fraction, as well as right ventricle (RV), left atrium (LA), and right atrium (RA) function.

Learning Objectives

• Demonstrate understanding of normal cardiac electrical function at the cellular level.
• Demonstrate knowledge of the normal ECG, including normal values for intervals and complexes.
• Demonstrate understanding of electrophysiologic mechanisms for the development of supraventricular and ventricular arrhythmias.
• For ventricular and supraventricular arrhythmias, list major causes, identify the likely etiology, and describe likely signs and symptoms in a given patient.
• Demonstrate understanding of atrial fibrillation classification with regards to the terms paroxysmal, persistent, long-standing persistent, permanent and nonvalvular.

Heart Electrical Function

• The heart has a specialized conduction system that initiates and distributes electrical impulses, including the SA node, AV node, Bundle of His, bundle branches, and Purkinje fibers.

Impulse Formation: Automaticity

• Automaticity is a cell's ability to depolarize itself to threshold and generate an action potential.
• Some cardiac cells, like the SA node, AV node, and Purkinje fibers, have natural automaticity, setting the pace for the heart's rhythm.
• Other cardiac cells do not possess automaticity.
• Physiologic mechanisms (like the adrenergic nervous system) can increase or decrease automaticity.

Arrhythmias

• Arrhythmias are disorders of the heart's rhythm caused by alterations in impulse formation or conduction.
• Major causes of arrhythmias include:
  • Alterations in impulse formation (automaticity): enhanced automaticity, triggered activity
  • Alterations in impulse conduction (heart block): re-entry, AV block.

Supraventricular Arrhythmias

• Types include:
  • Atrial fibrillation (AF)
  • Atrial flutter
  • Premature atrial complexes (PACs)
  • Atrial tachycardia.

Ventricular Arrhythmias

• Types include:
  • Premature ventricular complexes (PVCs)
  • Ventricular tachycardia (VT)
  • Ventricular fibrillation (VF)
  • Torsades de Pointes

QT Prolongation

• Normal QT interval ranges from 0.25-0.45 seconds.
• Prolonged QT interval (>440 milliseconds) can increase the risk of ventricular arrhythmias.

This quiz covers the fundamental concepts of heart failure, focusing on ejection fraction and heart failure classifications. Understand the differences between HFrEF, HFmrEF, HFpEF, and more. Test your knowledge of the complexities surrounding cardiac pathophysiology.