Cardiology - Heart Failure

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Heart Failure

I. Overview of Heart Failure

Heart failure (HF) is a complex clinical syndrome resulting from structural or functional impairment in blood ejection or ventricular filling. It manifests with signs of fluid overload and/or decreased cardiac output.

Key Characteristics:

• Fluid overload symptoms: Dyspnea (shortness of breath), paroxysmal nocturnal dyspnea (PND), orthopnea (difficulty breathing when lying flat), peripheral edema, crackles in lungs, elevated central venous pressure, and an S3 heart sound.
• Decreased cardiac output symptoms: Hypotension, low pulse pressure, cool extremities, reduced cognition, and worsening kidney or liver function.

Types of Heart Failure based on Left Ventricular Ejection Fraction (LVEF):

• Heart failure with reduced ejection fraction (HFrEF): LVEF of 40% or less.
• Common Causes: Coronary artery disease (CAD), hypertension, obesity, diabetes mellitus, and valvular heart disease.
• Pathophysiology: Reduced LVEF triggers neurohormonal system activation (Renin-Angiotensin-Aldosterone System (RAAS) and sympathetic nervous system). Initially adaptive, this becomes "chronic and maladaptive in the long term," leading to vasoconstriction, fluid overload, and "ventricular remodeling" (structural and functional changes in myocytes that worsen LV function).
• Heart failure with preserved ejection fraction (HFpEF): LVEF of 50% or greater.
• Common Causes: Hypertension (most common), aging, obesity, diabetes mellitus, atrial fibrillation, and CAD. Amyloid deposits are found in over 10% of HFpEF patients.
• Heart failure with mildly reduced ejection fraction (HFmEF): LVEF between 40% and 50%. This category includes "up to 25% of all patients with heart failure" and often receives similar treatment to HFrEF.

II. Screening and Diagnosis

A. Screening for Asymptomatic Patients at Risk:

• Pooled Cohort Equation to Prevent Heart Failure risk score: Can identify asymptomatic patients at increased risk, though the inclusion of race as a variable "is likely a flawed approach and limits the utility."
• Natriuretic Peptide Biomarker-based Screening: Useful in patients at risk (e.g., hypertension, diabetes, vascular disease). Elevated B-type natriuretic peptide (BNP) or N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels may prompt team-based care to prevent LV dysfunction. However, "there is no agreed-on standard for such screening and no certainty as to its cost-effectiveness."

B. Clinical Evaluation and Diagnosis:

• Comprehensive History and Physical Examination: Focus on risk factors and assessment of fluid and perfusion status.
• Initial Diagnostic Testing:ECG: Evaluates for myocardial infarction, tachyarrhythmia, or LV hypertrophy.
• Chest Radiography: May show cardiomegaly, vascular congestion, Kerley B lines, or pleural effusion; can also rule out pulmonary causes of dyspnea.
• Natriuretic Peptides (BNP/NT-proBNP): Crucial for differentiating cardiac from pulmonary causes of dyspnea. "BNP levels are elevated in patients with increased filling pressures and heart failure (typically >400 pg/mL)," while low in pulmonary disease (typically <100 pg/mL). High sensitivity and negative predictive value for HF. Note: BNP levels can be influenced by kidney failure, age, sepsis, ARNI therapy, female sex, and are typically reduced in elevated BMI.
• Laboratory Assessment: Complete blood count, serum electrolytes, kidney and liver function tests, glucose, lipid levels, and thyroid-stimulating hormone (TSH).
• Echocardiography: "The primary diagnostic modality for evaluation of heart failure." Provides information on chamber size, thickness, systolic/diastolic function, valvular pathology, and clues to underlying causes (e.g., regional wall motion abnormalities for CAD, myocardial changes for amyloidosis).
• Cardiac Magnetic Resonance (CMR) Imaging: Used for myocarditis and infiltrative processes (e.g., hemochromatosis, sarcoidosis, amyloidosis). Not routinely recommended; used only "in the search for a specific diagnosis."
• H2FPEF Risk Score: Assesses the likelihood of HFpEF to discriminate cardiac versus noncardiac dyspnea. Variables include obesity, atrial fibrillation, age >60, multiple antihypertensive drugs, and specific echocardiographic findings (E/e′ ratio >9, estimated pulmonary artery systolic pressure >35 mm Hg).
• Evaluation for Ischemia: CAD is the "leading cause of heart failure in the United States (>50% of patients)." Stress testing or coronary angiography may be considered based on symptoms, risk factors, and ECG/echocardiogram findings.
• Diagnosis Confirmation: HFrEF and HFpEF are diagnosed by appropriate LVEF combined with increased left ventricular filling pressures, documented by elevated natriuretic peptides, echocardiographic criteria, or invasive hemodynamic assessment.

C. Classification of Heart Failure Severity:

• New York Heart Association (NYHA) Functional Classification: Categorizes symptom severity (Class I: no limitations to Class IV: unable to perform any physical activity without symptoms). Patients can move between classes.
• American College of Cardiology (ACC)/American Heart Association (AHA) Stages of Heart Failure:Stage A: At Risk for HF: Risk factors present, but no symptoms, structural heart disease, or cardiac biomarkers.
• Stage B: Pre-HF: No symptoms, but evidence of structural heart disease, reduced ventricular function, increased filling pressures, or elevated biomarkers.
• Stage C: Symptomatic HF: Structural heart disease with current or previous HF symptoms.
• Stage D: Advanced HF: Marked HF symptoms that interfere with daily life and recurrent hospitalizations despite optimized guideline-directed medical therapy (GDMT). Patients can only progress in these stages.

III. Management of Heart Failure

A. General Principles:

• Multidisciplinary Team Management: Essential for optimal treatment due to the complexity and high comorbidity burden (e.g., hypertension, diabetes, CKD, COPD, dementia, malignancy, depression). Involves primary care, cardiology, and other specialists.
• Patient Education and Adherence: Repeated patient education, nonjudgmental assessment of adherence, and addressing obstacles are crucial for medication, diet, activity, and weight monitoring. Avoiding over-the-counter NSAIDs is advised.
• Primary Care Prevention: Focus on modifying risk factors like hypertension (goal <130/80 mm Hg) and diabetes (metformin, SGLT2 inhibitors). Weight loss and smoking cessation also prevent CAD, a major HF cause. Routine vaccinations (pneumonia, influenza) are important.
• Lifestyle Modification: Sodium restriction (1.5-2 g/day) and fluid restriction (1.5-2 L/day) are commonly advised. "Exercise training is recommended for all patients," improving functional capacity and quality of life.
• Sleep-Disordered Breathing: Common and underdiagnosed. Guideline-directed medical therapy for HF is the initial treatment. Persistent sleep-disordered breathing despite HF therapy should be treated with CPAP for obstructive sleep apnea. Adaptive...