When I was first diagnosed, doctors and nurses used words I’d never heard before — and they used them like I already knew what they meant. Ejection fraction. BNP. GDMT. I nodded along in the hospital bed and looked everything up later, alone, scared, and confused by what I found.
This glossary is the plain-English reference I wish someone had handed me. It’s organized by category so you can jump straight to what you need, and every definition leads with the plain answer first, then a little more context if you want it. It’s not a substitute for your care team — it’s a way to walk into your next appointment already understanding the language.
Understanding Your Diagnosis: Tests & Measurements
Ejection Fraction (EF)
Ejection fraction is the percentage of blood your left ventricle pumps out with each heartbeat. A normal EF falls between 55% and 70%; 41–49% is considered mildly reduced; and an EF under 40% usually points to heart failure or cardiomyopathy. It’s one number, not your whole story — plenty of survivors live full lives with a reduced EF.
BNP / NT-proBNP
BNP (B-type natriuretic peptide) and NT-proBNP are proteins your heart releases when it’s working harder than it should. A blood test measuring them helps confirm a heart failure diagnosis — BNP under 100 pg/mL, and NT-proBNP under roughly 125–450 pg/mL depending on your age, are considered normal. Higher numbers suggest your heart is under strain.
Echocardiogram (“Echo”)
An echocardiogram is an ultrasound of your heart. It’s painless, non-invasive, and it’s usually how you first learn your ejection fraction — it shows your heart’s chambers, valves, and pumping motion in real time.
Electrocardiogram (EKG or ECG)
An EKG records your heart’s electrical activity through small sensors placed on your skin. It takes seconds and can reveal irregular rhythms, past heart attacks, or strain on the heart muscle.
Cardiac Catheterization
A thin tube (catheter) is threaded through a blood vessel, usually in your wrist or groin, up to your heart to check for blockages, measure pressures, or guide a procedure like placing a stent.
Cardiac Stress Test
A stress test watches how your heart performs under exertion — usually on a treadmill or with medication that mimics exercise — to see whether blood flow to the heart muscle drops when it’s working hard.
Cardiac MRI
A cardiac MRI uses magnetic fields, not radiation, to produce detailed images of your heart’s structure and any scar tissue — often used when an echo doesn’t give a clear enough picture.
Chest X-Ray
A chest X-ray can show whether your heart is enlarged or whether fluid is building up in your lungs — both common signs of heart failure.
Troponin
Troponin is a protein released into your blood when heart muscle is damaged. It’s the primary blood test used to confirm or rule out a heart attack.
Cardiac Biomarkers
Cardiac biomarkers are substances in your blood — troponin and BNP among them — that rise when your heart is damaged or under stress. Tracking them over time helps your care team see whether treatment is working.
Holter Monitor
A Holter monitor is a small, wearable EKG you keep on for 24–48 hours or longer, to catch irregular heartbeats that a single in-office EKG might miss.
Types, Stages & Classes of Heart Failure
Heart Failure
Despite the name, heart failure doesn’t mean your heart has stopped — it means your heart can’t pump blood as well as it should, so your body doesn’t get all the oxygen and blood flow it needs. It’s a chronic condition you manage, not a single event.
Congestive Heart Failure (CHF)
CHF is heart failure advanced enough that fluid starts backing up — into your lungs, legs, or abdomen — because your heart can’t keep pace with your body’s demands. “Congestive” describes that fluid buildup, not a separate disease.
HFrEF (Heart Failure with Reduced Ejection Fraction)
HFrEF means your ejection fraction is 40% or below — your heart’s main pumping chamber isn’t squeezing as forcefully as it should. This is the type most heart failure medications are specifically proven to treat.
HFpEF (Heart Failure with Preserved Ejection Fraction)
HFpEF means your ejection fraction is normal, 50% or above, but your heart muscle has become stiff and doesn’t relax and fill with blood properly between beats. It’s just as real as HFrEF, even though the pumping number looks fine.
HFmrEF (Heart Failure with Mildly Reduced Ejection Fraction)
HFmrEF sits in between — an ejection fraction of 41% to 49%. It’s a newer category, and many of the same medications used for HFrEF are now recommended here too.
Cardiomyopathy
Cardiomyopathy is a disease of the heart muscle itself that makes it harder to pump blood. It can be caused by a heart attack (ischemic), or by other conditions — genetics, a viral infection, chronic high blood pressure — with no blockage involved (nonischemic).
Left-Sided Heart Failure
The left side of your heart isn’t pumping oxygen-rich blood out to your body effectively, which often causes fluid to back up into the lungs. It’s the most common type of heart failure.
Right-Sided Heart Failure
The right side of your heart struggles to pump blood to your lungs to pick up oxygen, which often causes fluid to pool in your legs, ankles, and abdomen. It frequently develops as a result of long-standing left-sided heart failure.
NYHA Functional Classification
Doctors use this four-class scale to describe how much heart failure limits your daily activity. Class I: no symptoms with ordinary activity. Class II: mild symptoms with ordinary activity. Class III: symptoms with less-than-ordinary activity. Class IV: symptoms even at rest. Your class can improve with treatment — mine did.
ACC/AHA Stages of Heart Failure (A–D)
This scale tracks heart failure’s progression rather than your symptoms in the moment. Stage A: at risk, no disease yet. Stage B: structural heart changes, no symptoms yet. Stage C: structural changes with current or past symptoms. Stage D: advanced, symptoms that persist despite treatment. Most survivors living full lives are managing Stage C.
Acute vs. Chronic Heart Failure
Acute heart failure comes on suddenly — often during or right after a major cardiac event — and needs emergency treatment. Chronic heart failure is the long-term, ongoing condition you manage day to day afterward. Most survivors live in the chronic phase; the acute crisis is usually what put you in the hospital in the first place.
What Causes Heart Failure — and Related Conditions
Coronary Artery Disease (CAD)
CAD happens when the arteries feeding your heart muscle become narrowed or blocked by plaque buildup. It’s the single most common underlying cause of heart failure.
Myocardial Infarction (Heart Attack)
A heart attack happens when blood flow to part of your heart muscle is suddenly blocked, and that tissue starts to die without oxygen. The more muscle damaged, the more likely heart failure follows.
“Widow-Maker” Heart Attack
This is the nickname for a heart attack caused by a complete blockage of the left anterior descending (LAD) artery — the vessel supplying a large share of the heart’s pumping muscle. It’s one of the most dangerous heart attacks to survive, and if you did, you already know why it earned that name.
Hypertension (High Blood Pressure)
Hypertension forces your heart to pump against constant extra resistance. Over years, that extra strain thickens and weakens the heart muscle, making it one of the leading contributors to heart failure.
Arrhythmia
An arrhythmia is any abnormal heart rhythm — beating too fast, too slow, or irregularly. Some are harmless; others, left untreated, can worsen heart failure or trigger a cardiac emergency.
Atrial Fibrillation (AFib)
AFib is the most common serious arrhythmia — the heart’s upper chambers quiver instead of beating in a coordinated rhythm. It raises stroke risk and can both cause and worsen heart failure.
Valvular Heart Disease
Your heart has four valves that keep blood flowing in one direction. When a valve doesn’t open fully or doesn’t close tightly, your heart has to work harder to compensate — and over time, that extra work can lead to heart failure.
Cardiogenic Shock
This is a medical emergency in which the heart suddenly can’t pump enough blood to meet the body’s needs, causing blood pressure to drop dangerously low. It requires immediate hospital treatment.
Pulmonary Hypertension
This is high blood pressure specifically in the arteries of the lungs. It forces the right side of the heart to work harder, which can lead to right-sided heart failure over time.
Cardiac Arrest (vs. Heart Attack)
A heart attack is a circulation problem — blocked blood flow. Cardiac arrest is an electrical problem — the heart suddenly stops beating altogether. They’re related but different, and a heart attack can trigger a cardiac arrest.
Symptoms & Complications
Edema
Edema is swelling caused by fluid trapped in your body’s tissues, most often in the ankles, feet, and legs. It’s one of the earliest and most common signs that heart failure is worsening.
Pulmonary Edema
This is fluid buildup in the lungs rather than the legs. It causes shortness of breath, coughing, and a feeling of not being able to catch your breath, and it can become a medical emergency.
Dyspnea (Shortness of Breath)
Dyspnea is the medical term for feeling breathless or like you can’t get enough air, even with ordinary activity — often one of the first symptoms that sends people to the doctor.
Orthopnea
Orthopnea is shortness of breath that happens specifically when lying flat, because fluid redistributes and puts extra pressure on the lungs. It’s why many heart failure patients sleep propped up on extra pillows.
Paroxysmal Nocturnal Dyspnea (PND)
PND is waking up suddenly in the middle of the night gasping for air, usually an hour or two after lying down. It’s a more specific and more serious symptom than ordinary orthopnea, and worth reporting to your doctor.
Ascites
Ascites is fluid buildup in the abdomen, causing visible swelling and bloating. In heart failure, it usually signals that the right side of the heart is struggling.
Cardiac Cachexia
This is unintentional muscle and weight loss that can occur in advanced heart failure, even when someone is eating normally. It’s a sign the body is working extremely hard just to keep the heart going.
Palpitations
Palpitations are the sensation of your heart pounding, fluttering, or skipping a beat. They’re not always dangerous, but new or worsening palpitations should always be mentioned to your care team.
Syncope
Syncope is the medical word for fainting — a temporary loss of consciousness caused by a sudden drop in blood flow to the brain. In heart failure, it can signal a dangerous arrhythmia and needs prompt evaluation.
Cardiac Fatigue
This is the deep, whole-body exhaustion common in heart failure — different from ordinary tiredness because your heart isn’t delivering oxygen-rich blood to your muscles efficiently. It’s real, it’s physical, and it’s not a character flaw.
Medications: What They Do and Why
Doctors call the core combination of heart failure drugs “guideline-directed medical therapy,” or GDMT. The medications below are usually used together, not as substitutes for one another.
Guideline-Directed Medical Therapy (GDMT)
GDMT is the term for the combination of medications proven by research to help people with reduced ejection fraction live longer and stay out of the hospital — typically a beta-blocker, an ACE inhibitor/ARB/ARNI, a mineralocorticoid receptor antagonist, and an SGLT2 inhibitor, usually all four together.
ACE Inhibitors
These widen and relax your blood vessels, easing the pressure your heart has to pump against. Common examples include lisinopril and enalapril.
ARBs (Angiotensin Receptor Blockers)
ARBs work similarly to ACE inhibitors — relaxing blood vessels to ease the heart’s workload — and are often used when someone can’t tolerate an ACE inhibitor’s side effects. Losartan is a common example.
ARNI (Angiotensin Receptor-Neprilysin Inhibitor)
ARNI — brand name Entresto, generic sacubitril/valsartan — combines two mechanisms in one pill and has been shown to outperform ACE inhibitors or ARBs alone for many people with HFrEF.
Beta-Blockers
Beta-blockers slow your heart rate and reduce the force it has to work with, letting it pump more efficiently over time. Common examples include metoprolol, carvedilol, and bisoprolol.
Diuretics (“Water Pills”)
Diuretics help your kidneys remove excess salt and fluid from your body, easing swelling and shortness of breath. They treat your symptoms, not the underlying heart muscle, which is why they’re usually combined with other medications.
MRA (Mineralocorticoid Receptor Antagonist)
Also called aldosterone antagonists, these medications — spironolactone, eplerenone — block a hormone that would otherwise cause your body to retain salt and fluid and further strain your heart.
SGLT2 Inhibitors
Originally developed for diabetes, drugs like empagliflozin and dapagliflozin were found to meaningfully reduce heart failure hospitalizations and are now a core part of standard treatment, even for people without diabetes.
Anticoagulants (Blood Thinners)
These medications reduce your blood’s ability to clot, lowering stroke risk — especially important if you also have atrial fibrillation. Examples include warfarin and newer options like apixaban and rivaroxaban.
Statins
Statins lower cholesterol and help stabilize plaque in your arteries, reducing the risk of another heart attack. They don’t directly treat heart failure but are often part of the picture when coronary artery disease is the underlying cause.
Digoxin
One of the oldest heart medications still in use, digoxin helps the heart beat more forcefully and can help control heart rate in certain arrhythmias like AFib. It’s used less often now that newer medications exist, but still has a role for some patients.
Nitrates
Nitrates relax and widen blood vessels, easing chest pain (angina) and reducing the heart’s workload. They’re sometimes combined with another drug, hydralazine, as an alternative for patients who can’t take ACE inhibitors or ARBs.
Devices & Procedures
Pacemaker
A small device implanted under the skin that sends electrical signals to keep your heart beating at a steady, appropriate rate when your heart’s natural signaling isn’t reliable.
Implantable Cardioverter-Defibrillator (ICD)
Similar to a pacemaker, but an ICD’s main job is to detect a dangerous, chaotic heart rhythm and deliver a shock to reset it — a safety net against sudden cardiac arrest for people at high risk.
Cardiac Resynchronization Therapy (CRT)
A specialized pacemaker that coordinates the timing between the heart’s left and right ventricles so they squeeze together more efficiently — used for certain patients with more advanced heart failure.
LVAD (Left Ventricular Assist Device)
A mechanical pump surgically implanted to help a severely weakened heart circulate blood. It can serve as a bridge to transplant or, for some patients, as a long-term treatment on its own.
Angioplasty & Stent (PCI)
In this procedure, a tiny balloon is used to open a blocked artery, and a small mesh tube (stent) is usually left in place to hold it open — restoring blood flow without open-heart surgery.
Coronary Artery Bypass Graft (CABG)
Open-heart surgery that reroutes blood flow around a blocked artery using a healthy blood vessel taken from elsewhere in the body — commonly called “bypass surgery.”
Heart Transplant
For the most advanced heart failure that no longer responds to other treatments, a transplant replaces the damaged heart with a healthy donor heart.
Intubation & Mechanical Ventilation
A breathing tube connected to a machine that breathes for you when your body can’t do it on its own — often used during a cardiac crisis or major surgery. If you spent time on a ventilator, you know it firsthand; I spent nearly three weeks on one.
Cardiac Rehabilitation
A medically supervised program of exercise, education, and support designed to help you safely rebuild strength and confidence after a cardiac event. It’s one of the most evidence-backed ways to improve both survival and quality of life.
Cardiac Ablation
A procedure that uses heat or cold energy, delivered through a catheter, to destroy small areas of heart tissue causing an abnormal rhythm — often used to treat AFib or other arrhythmias.
Recovery, Daily Life & Emotional Terms
These aren’t terms you’ll find in most clinical glossaries — but if you’re living this, they’re just as real.
Cardiac (Brain) Fog
The mental haziness, forgetfulness, and difficulty concentrating that many survivors experience after a major cardiac event — caused by a mix of shock, medication, poor sleep, and grief. It’s real, it’s common, and it typically improves with time.
Cardiac Anxiety
Persistent worry, hypervigilance about your heartbeat, or fear of another event — affecting an estimated 30–40% of heart failure survivors. It’s your mind trying to protect you, and it responds well to the right tools.
Post-Traumatic Stress After a Cardiac Event
Some survivors experience genuine post-traumatic stress after a cardiac crisis — intrusive memories, hypervigilance, or avoidance — similar to trauma responses seen after other life-threatening events. It’s treatable, and it deserves the same seriousness as physical recovery.
Fluid Restriction
A doctor-prescribed daily limit on how much liquid you drink, used to prevent fluid from building up and overworking a weakened heart.
Sodium Restriction
Limiting dietary salt, because sodium causes your body to retain fluid — one of the most consistently recommended lifestyle changes for managing heart failure.
Daily Weight Monitoring
Weighing yourself at the same time each morning to catch fluid buildup early. A sudden gain of 2–3 pounds in a day, or 5 pounds in a week, is often a signal to call your care team before it becomes a crisis.
Activity Tolerance
How much physical exertion your heart can currently handle without triggering symptoms. It’s not fixed — with cardiac rehab and time, most survivors’ activity tolerance meaningfully improves.
Caregiver Burnout
The physical and emotional exhaustion that can build up in spouses, adult children, and other loved ones caring for someone with heart failure. It’s common, it’s real, and caregivers need — and deserve — support too.
A Note on These Definitions
These definitions are written for clarity, not as clinical or legal guidance. They draw on my own experience as a two-time heart failure survivor along with publicly available patient education materials from the American Heart Association, the Heart Failure Society of America, and the Cleveland Clinic. Your own numbers, medications, and situation may differ — always ask your care team to explain anything specific to you.
Greg R. Traver is a heart failure survivor, author, and advocate. After surviving three “widow maker” heart attacks and two cardiac crises, he wrote Hope After Heart Failure — the book he wished he’d had when his own recovery began. He shares ongoing encouragement and resources at hopeafterheartfailure.com.