What Is Heart Failure and How Does It Develop?
Heart failure is a progressive condition where your heart muscle becomes too weak or stiff to pump blood efficiently, causing blood and fluid to back up in your lungs and other organs. It usually develops gradually over years from conditions that damage or overwork the heart.
In heart failure, your heart can't pump enough oxygen-rich blood to meet your body's needs during activity or, in severe cases, even at rest. This occurs either because the heart muscle is too weak to pump forcefully (systolic dysfunction) or because it's become too stiff to fill properly with blood between beats (diastolic dysfunction). When the heart can't keep up with demands, several compensatory mechanisms activate: the heart chambers enlarge to hold more blood, the heart muscle thickens to pump more forcefully, and the heart beats faster. Initially, these adaptations help maintain adequate blood flow, but over time they actually make heart failure worse.
As heart failure progresses, blood flow slows and blood returning to the heart through the veins backs up, causing fluid congestion in tissues. When the left side of the heart fails, blood backs up into the lungs (pulmonary congestion), causing shortness of breath. When the right side fails, blood backs up in the systemic veins, causing swelling in the legs, ankles, abdomen, and liver. The kidneys sense reduced blood flow and respond by retaining salt and water, which increases blood volume and worsens congestion. This creates a vicious cycle that progressively worsens unless treated with medications that interrupt these harmful compensatory mechanisms.
What Causes Heart Failure?
The most common causes are coronary artery disease and heart attacks (which damage heart muscle), high blood pressure (which overworks the heart), and heart valve disease. Other causes include cardiomyopathy, congenital heart defects, infections, and certain medications or substances.
Coronary artery disease and heart attacks are the leading cause of heart failure, accounting for about two-thirds of cases. A heart attack kills a section of heart muscle, leaving scar tissue that can't contract. High blood pressure is the second leading cause—constantly pumping against high pressure overworks and weakens the heart muscle over time. Heart valve disease (especially aortic stenosis and mitral regurgitation) makes the heart work harder to pump blood through narrowed valves or compensate for leaky valves. Cardiomyopathy (disease of the heart muscle itself) has many causes including genetics, viral infections, alcohol abuse, chemotherapy drugs, and metabolic disorders.
Less common causes include: diabetes, which damages heart muscle through multiple mechanisms; obesity, which increases workload on the heart; congenital heart defects present from birth; arrhythmias like atrial fibrillation, which reduce pumping efficiency; thyroid disease (both overactive and underactive); kidney disease, which causes fluid retention and hypertension; sleep apnea, which strains the heart; certain chemotherapy drugs (doxorubicin, trastuzumab); chronic alcohol or drug abuse (cocaine, methamphetamine); viral infections that inflame the heart (myocarditis); and rare conditions like amyloidosis, sarcoidosis, or hemochromatosis. Identifying and treating the underlying cause, when possible, is an important part of heart failure management and may allow partial recovery of heart function.
What Are the Symptoms and Stages of Heart Failure?
Main symptoms are shortness of breath (especially with activity or lying flat), fatigue, leg swelling, and rapid weight gain from fluid retention. Heart failure is classified into four stages (A through D) based on risk and symptoms, guiding treatment intensity.
The most common symptom is dyspnea (shortness of breath), initially only with exertion but progressing to occur with less activity and eventually even at rest. Many people develop orthopnea (difficulty breathing when lying flat) and need to sleep propped up on multiple pillows. Paroxysmal nocturnal dyspnea (suddenly waking up gasping for breath) is particularly characteristic. Persistent fatigue and weakness limit physical activity—simple tasks like climbing stairs or carrying groceries become exhausting. Fluid retention causes weight gain (often 2-3 pounds overnight or 5+ pounds in a week), swelling in feet, ankles, and legs, abdominal swelling, and reduced urination during the day with increased urination at night. Other symptoms include rapid or irregular heartbeat, persistent cough or wheezing (especially with white or pink-tinged phlegm), lack of appetite, nausea, difficulty concentrating, and increased heart rate.
Heart failure is staged using the ACC/AHA classification: Stage A includes people at high risk but without structural heart disease or symptoms (those with hypertension, diabetes, obesity, or metabolic syndrome). Stage B includes people with structural heart disease (previous heart attack, left ventricular dysfunction, valve disease) but no symptoms. Stage C includes people with structural heart disease and current or previous symptoms—this is the most common presentation. Stage D includes people with advanced disease and severe symptoms despite maximum medical therapy (refractory heart failure requiring specialized interventions like heart transplant or mechanical support). This staging helps determine treatment aggressiveness and prognosis. Heart failure is also classified by ejection fraction: HFrEF (reduced EF, below 40%), HFmrEF (mildly reduced, 41-49%), and HFpEF (preserved EF, 50% or above).
How Is Heart Failure Diagnosed?
Diagnosis involves medical history, physical examination, blood tests (including BNP), chest X-ray, electrocardiogram, and echocardiogram. The echocardiogram is particularly important for measuring ejection fraction and identifying the cause and type of heart failure.
Your doctor will ask about symptoms, medical history, family history, and risk factors, then perform a physical exam checking for signs of fluid retention (leg swelling, fluid in lungs heard through stethoscope, enlarged liver, distended neck veins), heart murmurs, rapid or irregular heartbeat, and other abnormalities. Initial tests include: chest X-ray to see heart size and check for fluid in lungs; electrocardiogram (ECG) to detect heart rhythm abnormalities, previous heart attack, or left ventricular hypertrophy; and blood tests including complete blood count, kidney function, liver function, thyroid function, and BNP (B-type natriuretic peptide) or NT-proBNP—hormones released by stressed heart muscle that are highly sensitive markers of heart failure.
The most important diagnostic test is the echocardiogram (ultrasound of the heart), which shows heart structure and function in real-time. It measures ejection fraction (percentage of blood pumped out with each beat), assesses heart chamber sizes, evaluates valve function, detects areas of abnormal muscle movement, and estimates pressures within the heart. This information determines whether you have systolic or diastolic dysfunction and helps identify the underlying cause. Additional tests may include: stress testing to evaluate exercise capacity and detect coronary artery disease; cardiac catheterization to check for blocked arteries; cardiac MRI for detailed images of heart structure and scarring; or cardiac CT scan. In selected cases, myocardial biopsy may be performed to diagnose specific causes like amyloidosis or myocarditis.
What Medications Treat Heart Failure?
Guideline-directed medical therapy includes ACE inhibitors or ARNIs, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors. Diuretics relieve fluid congestion. These medications dramatically improve symptoms, slow progression, prevent hospitalizations, and extend life.
For HFrEF (reduced ejection fraction), the cornerstone medications are: (1) ACE inhibitors (lisinopril, enalapril) or ARBs (losartan, valsartan) block hormones that worsen heart failure and have been shown to reduce death by 20-30%. ARNIs (sacubitril/valsartan) are newer drugs that work even better than ACE inhibitors, reducing death and hospitalization by an additional 20%. (2) Beta-blockers (metoprolol succinate, carvedilol, bisoprolol) slow heart rate, reduce blood pressure, and reverse harmful heart remodeling—they reduce death by 30-35%. (3) Mineralocorticoid receptor antagonists (spironolactone, eplerenone) are potassium-sparing diuretics that also block harmful hormones and reduce death by 30%. (4) SGLT2 inhibitors (dapagliflozin, empagliflozin) were originally diabetes drugs but dramatically improve heart failure outcomes, reducing hospitalizations by 30% even in people without diabetes.
Diuretics (furosemide, bumetanide, torsemide) are used to relieve congestion by removing excess fluid—they dramatically improve symptoms but haven't been shown to prolong life. Dosing is adjusted based on daily weights and symptoms. Additional medications used in specific situations include: digoxin to improve symptoms and reduce hospitalizations in severe HFrEF; hydralazine plus isosorbide dinitrate (particularly effective in African Americans); ivabradine to slow heart rate when beta-blockers alone aren't enough; and anticoagulants if atrial fibrillation is present. Most people need 3-5 medications. It takes weeks to months to up-titrate to target doses. Side effects like low blood pressure, dizziness, worsening kidney function, or high potassium require dose adjustments but shouldn't lead to stopping these life-saving medications. For HFpEF (preserved ejection fraction), treatment focuses on blood pressure control, diuretics for congestion, and SGLT2 inhibitors, which have recently been shown to benefit HFpEF as well.
What Lifestyle Changes Help Manage Heart Failure?
Essential daily habits include monitoring weight daily, restricting sodium to under 2,000 mg, limiting fluids to 1.5-2 liters if congested, regular light exercise as tolerated, avoiding alcohol and smoking, managing stress, and taking medications consistently. These practices dramatically improve symptoms and outcomes.
Daily weight monitoring is crucial for detecting fluid retention early. Weigh yourself at the same time each morning after urinating but before eating, wearing similar clothing. Call your doctor if you gain 2-3 pounds overnight, 3-5 pounds in a week, or experience worsening symptoms. Sodium restriction (less than 2,000 mg daily, or 1,500 mg if severe) is critical—excess sodium causes fluid retention that worsens congestion. Avoid processed foods, canned soups, restaurant meals, deli meats, cheese, bread, and salty snacks. Read all nutrition labels. Flavor food with herbs, spices, lemon, or vinegar instead of salt. Fluid restriction (usually 1.5-2 liters or 6-8 cups daily if you have advanced heart failure) prevents fluid overload. Count all fluids including water, coffee, tea, juice, milk, soup, and foods with high water content like ice cream or gelatin.
Exercise is important despite fatigue—cardiac rehabilitation or a supervised exercise program helps improve endurance, strength, and quality of life without worsening heart failure. Start slowly with activities like walking and gradually increase as tolerated. Stop if you develop chest pain, severe shortness of breath, dizziness, or irregular heartbeat. Absolutely avoid alcohol (it directly weakens heart muscle) and quit smoking. Get vaccinated against flu, pneumonia, and COVID-19. Manage stress through relaxation techniques, meditation, or counseling. Get adequate sleep (7-9 hours). Maintain a healthy weight—obesity worsens heart failure, but unintentional weight loss can indicate worsening disease ('cardiac cachexia') requiring medical attention. Take all medications exactly as prescribed—never stop or change doses without consulting your doctor. Keep all medical appointments and report new or worsening symptoms immediately.
