Heart Failure Overview and Mechanisms

Heart Failure: Generally

• Heart failure is a complex syndrome where the heart struggles to effectively pump blood.
• Stroke volume (SV) is the volume of blood pumped per heart contraction.
• Cardiac output (CO) is the volume pumped per minute (CO = SV x heart rate).
• Preload is the blood volume in the left ventricle before contraction.
• Afterload is the stress on the ventricular wall during systole.
• Inotropy refers to cardiac contractility.
• Ejection fraction (EF) is the percentage of blood leaving the heart per contraction (EF = (stroke volume/end diastolic volume) x 100).
• Frank-Starling mechanism describes how increased blood volume in the ventricle leads to stronger contractions.
• Heart failure with reduced ejection fraction (HFrEF) involves systolic dysfunction (pump problem). Causes include decreased contractility, low blood supply, increased afterload and impaired mechanical function.
• Heart failure with preserved ejection fraction (HFpEF) involves diastolic dysfunction (filling problem). It is characterized by non-compliant ventricles, elevated filling pressures and preserved ejection fraction (EF ≥ 50).
• Types of heart failure include biventricular (left and right side), cor pulmonale (secondary to pulmonary hypertension), left-sided, and right-sided heart failure.
• Left-sided heart failure involves impaired ability of left ventricle to pump blood, with backup into the lungs.
• Right-sided heart failure involves impaired ability of the right ventricle to pump blood, with backup into the body.
• The classification of heart failure based on ACC/AHA stages and NYHA classes is used to assess severity.

Heart Failure: Risk Factors

• Cardiac disorders (ischemic heart disease, valvular heart disease, hypertension)
• Other chronic conditions (hypertension, diabetes, obesity)
• Toxins (smoking, alcohol, certain medications)
• High-output states (thyrotoxicosis, anemia)
• Age is a contributing risk factor

Heart Failure: Complications

• Cardiogenic shock
• Biventricular heart failure
• Arrhythmias
• End organ damage
• Liver damage (congestive hepatopathy)
• Exacerbation (Certain drugs, nonsteroidal anti-inflammatory drugs, excessive beta blockers or calcium channel blockers, cyclophosphamide)

Heart Failure: Signs and Symptoms

• High filling pressures (pulmonary edema, dyspnea, orthopnea, exercise intolerance, paroxysmal nocturnal dyspnea, basilar crackles, tachypnea, jugular venous distention, hypoxemia, fatigue, peripheral edema, hepatomegaly, S3)
• Low cardiac output (tachycardia, hypotension, cool extremities, decreased pulse pressure, decreased urine output, decreased appetite)

Heart Failure: Diagnostic Imaging

• Chest X-ray: Detects cardiomegaly (enlarged heart), chamber and vessel enlargement, pulmonary congestion, pericardial and pleural effusions.
• Doppler echocardiography: Evaluates hemodynamics, valvular function, and ventricular function.
• Pulmonary artery catheterization: Measures cardiac output, filling pressures, and pulmonary capillary wedge pressure (PCWP).
• MRI: Visualizes ventricular volumes, myocardial mass, presence of myocardial remodeling.

Heart Failure: Lab Results

• BNP and NT-proBNP: Elevated levels indicate heart failure.
• Serum creatinine and blood urea nitrogen (BUN): Increased levels suggest decreased glomerular filtration rate, which is a sign of impaired kidney function.
• Serum total bilirubin and aminotransferase: Increased levels suggest impaired liver function.

Heart Failure: Treatment

• Medications: Individualized according to NYHA class, EF, comorbidities. Diuretics, ACE inhibitors, ARBs, beta blockers, aldosterone antagonists. Considerations of other medication classes for acute exacerbations.

Heart Failure: Other Interventions

• Lifestyle modifications (low dietary salt, exercise, smoking cessation, decreased alcohol intake)
• Cardiac rehabilitation
• Implantable cardioverter-defibrillator (ICD)
• Ventricular assist device (VAD)
• Biventricular pacemaker
• Heart transplant

Cor Pulmonale

• Cor pulmonale is right-sided heart failure secondary to pulmonary hypertension.
• Right ventricular hypertrophy, dilation, and dysfunction are hallmarks of cor pulmonale
• Elevated pulmonary vascular resistance frequently due to causes such as COPD and pulmonary fibrosis.
• Conditions like obstructive sleep apnea, obesity-hypoventilation syndrome, and chest wall irregularities.
• Often presents with symptoms of right-sided heart failure, including peripheral edema, jugular venous distension, and hepatomegaly.
• Chest X-ray and echocardiography for diagnosis and to evaluate right ventricular function.
• Management focuses on treating the underlying pulmonary condition.

Left Heart Failure

• Left heart failure is a clinical syndrome where the left ventricle fails to pump enough blood, leading to backup into the lungs. Categorized by left ventricular ejection fraction (LVEF) into systolic (HFrEF) and diastolic (HFpEF).

• Risk factors include coronary artery disease, infiltration diseases, hypertension, valve disease, exposure to toxins, arrhythmias

• Complications of left sided heart failure include pulmonary edema, pulmonary hemorrhage, pleural effusion, renal insufficiency. Signs and symptoms include exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, pulmonary edema (wet cough, froth), bibasilar crackles, nocturia, restlessness, and confusion, s3/s4 heart sounds

Right Heart Failure

• Right heart failure is a clinical syndrome where the right ventricle fails to pump enough blood, leading to backup into the venous system

• A clinical syndrome due to alterations of structure and function of the right ventricle.

• Common causes include left-sided heart failure, right ventricle infarction, and bacterial endocarditis

• Compilcations include eventual failure of the left side of the heart.

• Signs and symptoms include distended jugular vein, hepatojugular reflux, fatigue, peripheral edema, hepatomegaly, ascites, s3/s4 heart sounds and poor gas exchange.

• Symptoms commonly related to fluid buildup in the body, such as edema, and related to the lungs, such as shortness of breath

• Diagnosis typically involves chest x ray and echocardiography to assess cardiac structure and function

Diastolic Heart Failure

• Diastolic heart failure is a clinical syndrome characterized by the heart's inability to relax and fill adequately which leads to reduced cardiac output.

• Diagnosed by clinical presentation, symptoms, imaging, and diagnostics.

• Causes include stiff, non-compliant ventricle, reduced ventricular relaxation, increased end-diastolic pressure, increased resistance to filling, and reduced preload.

• Risk factors include advancing age, restrictive cardiomyopathy, hypertrophic cardiomyopathy, long-standing hypertension, valvular disease, coronary artery disease, diabetes and obesity

• Complications of diastolic heart failure can include arrhythmias, pulmonary embolism, pulmonary hypertension, right ventricular failure.