Heart failure happens when the heart muscle becomes too weak or too stiff to pump blood effectively. It’s not a single disease but the end result of many different conditions that damage or overwork the heart over time. About 7.4 million U.S. adults currently live with heart failure, more than double the 3.3 million affected in 1988. The causes range from blocked arteries and high blood pressure to infections, genetics, and toxic exposures.
Coronary Artery Disease
The most common cause of heart failure is coronary artery disease, where fatty plaques build up inside the arteries that supply blood to the heart muscle. These plaques narrow the arteries and reduce the flow of blood and oxygen. Over time, the heart muscle in the affected area weakens from chronic oxygen deprivation.
The more dangerous scenario is when a plaque ruptures. This triggers a blood clot that can partially or completely block the artery, causing a heart attack. During a heart attack, a section of heart muscle dies. The heart then tries to compensate by remodeling itself, stretching and reshaping the remaining muscle to keep pumping. This remodeling process, while initially helpful, gradually makes the heart larger and less efficient. People who survive a heart attack have a significantly elevated risk of developing chronic heart failure as a direct result of this structural change.
High Blood Pressure
Persistently elevated blood pressure forces the heart to work harder with every beat. Over years, this extra workload causes the heart muscle to thicken, stiffen, and eventually weaken. A large meta-analysis covering more than 20 million participants found that people with hypertension have a 71% higher risk of developing heart failure compared to those with normal blood pressure.
The relationship follows a clear dose-response pattern. Every 20-point increase in systolic blood pressure (the top number) raises heart failure risk by 28%. Every 10-point increase in diastolic pressure (the bottom number) raises it by 12%. At extreme levels around 180/120, the risk of heart failure is three to five times higher than at a healthy reading of 100/60. This makes blood pressure control one of the single most effective ways to prevent heart failure.
Diabetes and Metabolic Damage
Diabetes can damage the heart muscle directly, even in people who don’t have blocked arteries or high blood pressure. Chronically elevated blood sugar produces compounds that alter structural proteins in the heart, essentially creating abnormal crosslinks in the collagen that makes up the heart’s scaffolding. These crosslinks make collagen harder for the body to break down, leading to a buildup of scar-like tissue called fibrosis. The result is a stiffer heart that can’t relax and fill properly between beats.
Diabetes also disrupts how heart cells use fuel. Normally, heart muscle cells are flexible and can burn both sugar and fat for energy. In a diabetic heart, the cells lose much of their ability to take in and use glucose, becoming overly dependent on fat. This shift leads to a toxic accumulation of fat-related byproducts inside the heart cells, further impairing their ability to contract. The combination of increased stiffness and weakened contraction creates a form of heart failure specific to diabetes, sometimes called diabetic cardiomyopathy.
Heart Valve Problems
Your heart has four valves that open and close with each beat to keep blood flowing in the right direction. When a valve doesn’t open fully (stenosis) or doesn’t close tightly (regurgitation), the heart has to work much harder to move blood. Over months and years, this extra strain reshapes the heart chambers in ways that eventually lead to failure.
A narrowed aortic valve, for example, forces the left ventricle to generate more pressure with each beat, causing the muscle wall to thicken. A leaky mitral valve allows blood to flow backward into the upper chamber, forcing the heart to pump a larger volume with each cycle. Mitral valve prolapse, where the valve leaflets bulge backward, affects 2 to 3% of the population and is a common source of valve leakage that can progress to heart failure if severe enough. Whether the underlying problem is genetic or develops from wear and tear, the end result is the same: a heart chamber that remodels itself into a shape that pumps less effectively.
Infections and Inflammation
Viral infections can directly inflame the heart muscle, a condition called myocarditis. Many common viruses have been linked to this kind of damage, including adenovirus (a cause of the common cold), COVID-19, Epstein-Barr virus (which causes mono), hepatitis B and C, herpes simplex virus, and parvovirus. Even gastrointestinal viruses and rubella can trigger it.
When a virus infects the heart, the immune system’s inflammatory response can injure heart muscle cells alongside the virus. In mild cases, the inflammation resolves and the heart recovers. But when the damage is extensive or the immune response persists, the heart muscle weakens to the point where it can no longer pump blood effectively. Some people develop heart failure weeks after what seemed like a routine viral illness, making myocarditis an underrecognized cause.
Genetic and Inherited Causes
Heart failure sometimes runs in families because of inherited mutations in genes that build the heart’s contractile machinery. These mutations affect proteins responsible for generating force or maintaining the structure of heart muscle cells. Two genes, MYH7 and MYBPC3, account for roughly 80% of mutations that cause hypertrophic cardiomyopathy, a condition where the heart muscle grows abnormally thick.
Dilated cardiomyopathy, where the heart chambers stretch and weaken, involves a broader set of genes. Mutations in the gene TTN, which encodes a giant structural protein called titin, are particularly important. Titin acts like a molecular spring that maintains the organization of the heart’s contractile units and provides elasticity. When it’s defective, the heart muscle loses its ability to contract and rebound normally. Restrictive cardiomyopathy, a rarer form where the heart becomes extremely stiff, also traces back to mutations in many of these same structural genes. Because these conditions are inherited, heart failure from genetic cardiomyopathy often appears in younger adults and can affect multiple family members across generations.
Alcohol and Toxic Exposures
Heavy, sustained alcohol use is a well-established cause of heart failure. The threshold typically cited is more than 80 grams of alcohol per day (roughly 6 or more standard drinks) for at least five years. At that level, alcohol directly poisons heart muscle cells, causing the heart to enlarge and weaken in a pattern identical to dilated cardiomyopathy. Women appear to develop alcohol-related heart damage at lower doses and after shorter periods of heavy drinking than men.
The good news is that alcohol-related heart failure is partially reversible. People who stop drinking, or at least reduce their intake substantially, often see measurable improvement in how well their heart pumps. Complete abstinence offers the best outcomes, but even cutting back below the 80-gram daily threshold has been associated with better prognosis in published studies.
Cancer Treatment
Certain chemotherapy drugs, particularly a class called anthracyclines, can cause irreversible heart damage. The risk is directly tied to the total cumulative dose a patient receives. At a relatively low lifetime dose of 150 mg/m², only about 0.2% of patients develop heart failure. At 300 mg/m², that rises to 1.6%. At 450 mg/m², it reaches 3.3%, and at 600 mg/m², 8.7% of patients develop clinical heart failure. Microscopic damage to heart cells has been detected at doses as low as 240 mg/m². Additional risk factors include older or very young age, female sex, prior chest radiation, existing high blood pressure, and combination treatment with other cardiotoxic drugs.
Other Contributing Factors
Obstructive sleep apnea places chronic stress on the heart. Repeated episodes of interrupted breathing during sleep cause oxygen levels to drop and blood pressure to spike dozens of times per night. Over years, this intermittent strain thickens the heart walls and raises the pressure in the blood vessels leading to the lungs, which can lead to right-sided heart failure.
Thyroid disorders also play a role. An overactive thyroid forces the heart to beat faster and harder than necessary, sometimes for months before diagnosis, while an underactive thyroid can weaken the heart muscle and cause fluid retention. Obesity places extra demand on the heart simply because there is more tissue requiring blood flow, and the associated metabolic changes, including insulin resistance and chronic low-grade inflammation, compound the damage. Severe kidney disease, which disrupts fluid balance and blood pressure regulation, frequently contributes to heart failure as well.
In many cases, heart failure results not from a single cause but from several of these factors acting together. Someone with moderately high blood pressure, early diabetes, and a history of heavy drinking faces a compounding risk that far exceeds any one factor alone. This overlap is one reason heart failure has become increasingly common even as treatments for individual conditions have improved.