Heart Failure: Pathophysiology and Diagnosis¶
Chapter 264 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- Heart failure (HF) is a complex clinical syndrome characterized by impaired ventricular filling or ejection, with global prevalence of 6.7 million in the U.S. and 56.2 million worldwide.
- HF is classified into three main types: HF with reduced ejection fraction (HFrEF, EF ≤ 40%), HF with preserved ejection fraction (HFpEF, EF ≥ 50%), and HF with mildly reduced ejection fraction (HFmrEF, EF 41–49%).
- Neurohormonal activation (RAAS, SNS) and ventricular remodeling are central pathophysiological mechanisms, with SGLT-2 inhibitors showing significant benefits in reducing mortality and hospitalization.
- Diagnosis relies on clinical evaluation, natriuretic peptide levels (BNP/NT-proBNP), and imaging (echocardiography, CMR). The universal definition of HF includes symptoms/signs of fluid retention or congestion with objective evidence of cardiac dysfunction.
- Management involves guideline-directed therapies (ACEIs, beta-blockers, MRA), device therapy (CRT, ICD), and addressing comorbidities like diabetes and sleep apnea.
1. DEFINITION & OVERVIEW¶
Heart failure (HF) is a complex clinical syndrome characterized by impaired ventricular filling or ejection, leading to inadequate cardiac output. The American Heart Association/American College of Cardiology/HFSA defines HF as a syndrome with symptoms/signs due to structural/functional ventricular impairment. The European Society of Cardiology emphasizes cardinal symptoms (dyspnea, edema, fatigue) and signs (elevated JVP, pulmonary crackles) due to cardiac dysfunction. The universal definition of HF includes symptoms/signs of fluid retention or congestion with objective evidence of cardiac dysfunction (e.g., elevated natriuretic peptides or imaging evidence of congestion).
Table 264-1: Independent Predictors of Adverse Outcomes in Heart Failure¶
| Clinical | Predictor |
|---|---|
| Male sex | |
| Older age | |
| Diabetes mellitus | |
| Chronic kidney disease | |
| Coronary artery disease | |
| Advanced NYHA class | |
| Presence of third heart sound or elevated JVP |
| Clinical | Predictor |
|---|---|
| Decreased exercise capacity | |
| Cardiac cachexia | |
| Depression |
Table 264-2: Selected Causes of Heart Failure¶
| Heart Failure with Reduced Ejection Fraction | Heart Failure with Preserved Ejection Fraction |
|---|---|
| Coronary artery disease | Pulmonary hypertension |
| Myocardial infarction | Diastolic dysfunction |
| Myocardial ischemia | Hypertension |
| Nonischemic cardiomyopathy | Restrictive cardiomyopathy |
| Infiltrative disorders | Valvular heart disease |
| Familial disorders | Chronic lung disease |
| Tachycardia induced | Myocarditis |
| Valvular heart disease | Endomyocardial fibroelastosis |
| Aortic stenosis or regurgitation | Constrictive pericarditis |
| Mitral or tricuspid regurgitation | Amyloidosis |
1.1 Clinical Classification¶
HF is classified into three types: HFrEF (EF ≤ 40%), HFpEF (EF ≥ 50%), and HFmrEF (EF 41–49%). HFrEF is associated with systolic dysfunction, while HFpEF involves diastolic dysfunction. HFrecEF refers to patients with HFrEF who show recovery of EF to normal range with therapy.
1.2 Epidemiology¶
Global prevalence of HF is 56.2 million, with age-specific rates increasing significantly (1–2% in 40–49 years, 10%+ in >80 years). Racial disparities exist, with Black individuals having the highest risk. Obesity, hypertension, and diabetes are major risk factors. Mortality rates are ~50% at 5 years, with severe HF having 40% 1-year mortality.
2. EPIDEMIOLOGY¶
Global incidence of HF is 6.7 million in the U.S. with >600,000 new cases/year. Prevalence increases with age (1–2% in 40–49 years, 10%+ in >80 years). Racial disparities exist, with Black individuals having highest risk. Obesity, hypertension, and diabetes are major risk factors. Mortality rates are ~50% at 5 years, with severe HF having 40% 1-year mortality. HF readmissions are common (83% hospitalized at least once within 1 year).
Table 264-3: Mechanisms of Ventricular Remodeling¶
| Changes in Myocyte Biology | Changes in Myocardial Composition | Changes in Ventricular Geometry |
|---|---|---|
| Abnormal excitation-contraction coupling | Myocyte necrosis, apoptosis, and autophagy | Ventricular dilation and wall thinning |
| Fetal gene expression (b-myosin heavy chain) | Interstitial and perivascular fibrosis | Increased sphericity and displacement of papillary muscles |
| Changes in Myocyte Biology | Changes in Myocardial Composition | Changes in Ventricular Geometry |
|---|---|---|
| b-Adrenergic receptor desensitization | Matrix degradation | Atrioventricular valve regurgitation |
2.1 Demographics¶
Prevalence varies by age and race/ethnicity. Black individuals have highest risk, followed by Hispanic, White, and Chinese Americans. Age-adjusted mortality rates are higher in men than women. Mortality rates vary by region (highest in Midwest) and population density (highest in rural areas).
2.2 Comorbidities¶
HF is associated with comorbidities like diabetes, obesity, sleep apnea, and renal dysfunction. Diabetes increases risk of HF and worsens outcomes. Obesity is a risk factor for HFpEF and complicates volume status assessment.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
HF results from structural/functional cardiac abnormalities, with coronary artery disease (2/3 of cases) and hypertension (75% of cases) as leading causes. Pathophysiology includes neurohormonal activation (RAAS, SNS), ventricular remodeling, and myocardial dysfunction. SGLT-2 inhibitors improve outcomes by reducing neurohormonal activation and improving cardiac remodeling.
Table 264-4: New York Heart Association Functional Classification¶
| Functional Class | Limitation | Clinical Assessment |
|---|---|---|
| Class 1 | None | Ordinary physical activity does not cause undue fatigue, dyspnea, palpitations, or angina. |
| Class II | Mild | Comfortable at rest. Ordinary physical activity (e.g., carrying heavy packages) may result in fatigue, dyspnea, palpitations, or angina. |
| Class III | Moderate | Comfortable at rest. Less than ordinary physical activity (e.g., getting dressed) leads to symptoms. |
| Class IV | Severe | Symptoms of heart failure or angina are present at rest and worsen with any activity. |
3.1 Neurohormonal Activation¶
Sympathetic overactivation and RAAS activation lead to vasoconstriction, sodium retention, and myocardial hypertrophy. This worsens HF and contributes to cardiac remodeling. Inhibition of RAAS and SNS with ACEIs, ARBs, and MRA improves outcomes.
3.2 Ventricular Remodeling¶
Chronic hemodynamic stress (pressure/volume overload) leads to ventricular remodeling with increased wall stress, fibrosis, and altered myocardial structure. This worsens cardiac function and contributes to progressive HF.
4. CLINICAL FEATURES¶
Symptoms include dyspnea (orthopnea, paroxysmal nocturnal dyspnea), fatigue, and edema. Signs include elevated JVP, pulmonary crackles, and peripheral edema. Complications include renal dysfunction, arrhythmias, and sudden cardiac death. Secondary mitral regurgitation and pulmonary hypertension are common in advanced HF.
Table 264-5: Precipitating Factors in Heart Failure¶
| Patient-Related | Provider-Related | Heart Failure–Related | Other Disease States |
|---|---|---|---|
| Excess exertion or emotional stress | Use of medications that cause salt and water retention (e.g., NSAIDs) | Uncontrolled hypertension | Systemic infection |
| Excess fluid and/or sodium intake | Prescribed use of medications with negative inotropic properties (e.g., CCBs) | Myocardial ischemia or infarction | Worsening renal or hepatic failure |
| Nonadherence with medications | Unrecognized congestion and inadequate use of diuretics | Atrial or ventricular arrhythmias | Hyperthyroidism |
| Heavy alcohol use | Pulmonary embolism | Untreated sleep apnea |
4.1 Symptoms¶
Dyspnea (exertional, orthopnea, PND), fatigue, and peripheral edema are common. Paroxysmal nocturnal dyspnea (PND) is sudden awakening with dyspnea requiring upright position. Orthopnea occurs with recumbency due to fluid redistribution.
4.2 Signs¶
Elevated JVP, pulmonary crackles, peripheral edema, and hepatomegaly are common. Pulsus alternans (alternating strong/weak pulses) indicates severe left ventricular dysfunction.
5. DIFFERENTIAL DIAGNOSIS¶
HF must be differentiated from pulmonary causes (COPD, pulmonary edema), renal causes (congestive heart failure vs. renal failure), and noncardiac causes of edema (venous insufficiency, lymphedema). Other conditions include anemia, thyroid disease, and pulmonary hypertension.
Table 264-6: Diagnostic Criteria for Cachexia in Adults¶
| Criteria | Description |
|---|---|
| Underlying disease and body weight loss ‡5% in £12 months (or BMI <20 kg/m²) | |
| Decrease in muscle strength | |
| Fatigue | |
| Anorexia | |
| Low fat-free mass index | |
| Abnormal biochemistry: inflammation, anemia, low serum albumin levels |
5.1 Pulmonary Causes¶
Chronic lung disease, pulmonary hypertension, and COPD can mimic HF with dyspnea. Orthopnea and PND are more specific for cardiac causes, while pulmonary edema is associated with acute decompensation.
5.2 Noncardiac Causes¶
Venous insufficiency, lymphedema, and renal failure can cause peripheral edema. Anemia and hypothyroidism may present with fatigue and dyspnea. Sleep apnea is a common comorbidity in HF.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis involves clinical evaluation, natriuretic peptides (BNP/NT-proBNP), and imaging (echocardiography, CMR). The universal definition of HF includes symptoms/signs of fluid retention or congestion with objective evidence of cardiac dysfunction. Echocardiography assesses ventricular function and valvular disease.
Table 264-7: Mechanisms That Contribute to Development of Heart Failure in Patients with Type 2 Diabetes Mellitus¶
| Mechanism | Description |
|---|---|
| Altered myocardial substrate | |
| Abnormal mitochondrial bioenergetics | |
| Oxidative stress and inflammation | |
| Lipotoxicity | |
| Endoplasmic reticulum stress | |
| Impaired insulin signaling | |
| b-Adrenergic receptor signaling | |
| G protein–coupled receptor kinase 2 signaling | |
| RAAS activation | |
| Advanced glycation end products | |
| Autophagy |
6.1 Laboratory Tests¶
Elevated BNP/NT-proBNP levels support HF diagnosis. Electrolyte abnormalities (hyponatremia, hypokalemia) are common. Renal function tests (BUN, creatinine) assess for renal impairment. Anemia and iron deficiency are common comorbidities.
6.2 Imaging¶
Chest X-ray shows cardiomegaly and pulmonary congestion. Echocardiography assesses EF, ventricular size, and valvular function. CMR provides detailed assessment of myocardial structure and function. Cardiac catheterization may be used for hemodynamic assessment.
7. MANAGEMENT & TREATMENT¶
Guideline-directed therapies include ACEIs, ARBs, beta-blockers, and MRA. Device therapy (CRT, ICD) is indicated for specific patients. SGLT-2 inhibitors improve outcomes in HF. Non-pharmacologic management includes lifestyle modifications, diuretics, and addressing comorbidities like diabetes and sleep apnea.
Table 264-8: Differential Diagnosis of Heart Failure¶
| Symptom/Sign | Differential Diagnosis |
|---|---|
| Dyspnea | Chronic lung disease, pulmonary hypertension, neuromuscular disease, anemia, iron-deficiency anemia |
| Edema | Venous insufficiency, nephrotic syndrome, lymphedema, hepatic cirrhosis |
| Orthopnea | Pulmonary disease, cardiac disease |
| PND | Pulmonary disease, cardiac disease |
7.1 Pharmacologic Therapy¶
ACEIs/ARBs, beta-blockers, and MRA are first-line for HFrEF. SGLT-2 inhibitors reduce mortality and hospitalization. Diuretics (loop, thiazide) manage fluid overload. Digoxin is used for rate control in atrial fibrillation.
7.2 Device Therapy¶
CRT improves outcomes in patients with LV dyssynchrony. ICDs reduce sudden cardiac death in patients with EF ≤ 35%. Implantable devices are indicated for specific patients with advanced HF.
8. PROGNOSIS & COMPLICATIONS¶
Mortality rates are ~50% at 5 years, with severe HF having 40% 1-year mortality. Complications include renal dysfunction, arrhythmias, sudden cardiac death, and worsening heart failure. Prognosis is worse in patients with diabetes, obesity, and comorbidities.
8.1 Mortality¶
Overall 5-year survival is ~50%. Severe HF has 40% 1-year mortality. HF readmissions are common, with 83% hospitalized at least once within 1 year. Mortality rates vary by race and region.
8.2 Complications¶
Complications include renal dysfunction, arrhythmias, sudden cardiac death, and progressive heart failure. Secondary mitral regurgitation and pulmonary hypertension are common in advanced HF.
9. SPECIAL CONSIDERATIONS¶
HF in pregnancy requires careful management due to increased cardiac workload. Pediatric HF is often due to congenital heart disease. Elderly patients have higher risk of complications and require tailored management. Comorbidities like diabetes and sleep apnea worsen outcomes.
9.1 Pregnancy¶
Pregnancy increases cardiac workload and risk of decompensation. Management includes close monitoring, diuretics, and avoiding NSAIDs. Delivery timing is critical to minimize maternal and fetal risks. Pediatric HF is often due to congenital heart disease. Management includes surgical correction, device therapy, and long-term follow-up. Growth and development are critical considerations.
10. KEY POINTS & CLINICAL PEARLS¶
- HF is a complex syndrome with global prevalence of 56.2 million. 2. Diagnosis relies on clinical evaluation, natriuretic peptides, and imaging. 3. Management includes guideline-directed therapies (ACEIs, beta-blockers, SGLT-2 inhibitors). 4. Prognosis is worse in patients with comorbidities like diabetes and obesity. 5. Device therapy (CRT, ICD) improves outcomes in specific patients.