An EKG and an echocardiogram are both heart tests, but they measure completely different things. An EKG records your heart’s electrical activity through sensors on your skin, producing a line graph of your heartbeat’s rhythm and timing. An echocardiogram uses ultrasound to create a live video of your heart, showing its chambers, valves, and blood flow in real time. Doctors often order one or both depending on what they suspect is going on.
How Each Test Works
An EKG (also written as ECG) detects the tiny electrical signals your heart generates every time it beats. Those signals travel through your body and reach your skin, where small sticky patches called electrodes pick them up. A standard 12-lead EKG places 10 electrodes on your chest, arms, and legs, each “looking” at the heart from a different angle. The machine translates those signals into a line tracing with distinctive peaks and valleys. Each peak corresponds to a specific phase of your heartbeat: the upper chambers contracting, the lower chambers contracting, and the heart resetting for the next beat.
An echocardiogram works like a sonar system. A handheld probe pressed against your chest sends out high-frequency sound waves (between 1.5 and 7.5 MHz) that bounce off your heart’s structures and return to the probe. The machine measures how long each echo takes to return and how strong it is, then assembles a two-dimensional image in real time. A feature called Doppler mode tracks how blood cells move by measuring changes in the frequency of reflected sound waves, letting the technician see blood flowing through valves and chambers, and calculate its speed.
What Each Test Can Diagnose
Because they capture different information, these tests answer different clinical questions.
EKG Strengths
An EKG excels at detecting problems with your heart’s electrical system and blood supply. It’s the go-to test for identifying irregular heart rhythms like atrial fibrillation, which shows up as a characteristic “irregularly irregular” pattern with no organized activity from the upper chambers. It can also detect heart blocks, where electrical signals between the upper and lower chambers are delayed or completely disconnected.
The EKG is especially critical for diagnosing heart attacks. During a heart attack, the electrical pattern changes in predictable ways depending on which part of the heart is losing blood flow. Specific changes in the tracing can tell doctors not only that a heart attack is happening, but which artery is blocked. Old heart attacks leave permanent scars that also show up as distinctive changes on the tracing, even years later. Beyond heart-specific problems, an EKG can reveal electrolyte imbalances, effects of certain medications, and conditions like hypothermia that affect heart function.
Echocardiogram Strengths
An echocardiogram shows the physical structure and pumping function of your heart. It’s the primary tool for measuring ejection fraction, the percentage of blood your heart pushes out with each beat. According to the American Heart Association, a normal ejection fraction falls between 55% and 70%. A reading below 40% typically indicates heart failure or cardiomyopathy, while a mildly reduced range sits between 41% and 49%. Readings above 75% can signal a condition where the heart muscle is abnormally thick.
This test is also the standard for evaluating heart valves. It can show whether a valve is too narrow (stenosis), leaking backward (regurgitation), or structurally abnormal. It detects thickened heart walls, enlarged chambers, fluid around the heart, and abnormal wall motion that might suggest damage from a previous heart attack or an infiltrative disease like cardiac amyloidosis, where abnormal proteins build up in heart tissue. Wall thickness greater than 1.2 cm without another explanation raises suspicion for amyloidosis, while a wall thickness of 15 mm or more at any segment is a key marker for hypertrophic cardiomyopathy.
What to Expect During Each Test
An EKG is one of the quickest tests in medicine. You lie on an exam table, a technician places the electrode patches on your skin (they may shave small areas of chest hair for better contact), and the machine records for about 10 seconds. The whole visit typically takes under 10 minutes. No fasting or special preparation is needed, though you should skip oily skin lotions beforehand since they interfere with electrode contact. Wear a shirt that’s easy to remove, and avoid full-length tights or pantyhose that would block electrode placement on your legs.
An echocardiogram takes longer, around 20 minutes for a standard transthoracic exam. You lie on your left side while a sonographer presses the ultrasound probe against different spots on your chest, using gel to improve the sound wave connection. It’s painless, though the probe pressure can feel mildly uncomfortable. No fasting is required for a standard echo, though some specialized versions (like a transesophageal echo, where the probe goes down your throat) do require fasting and sedation.
Stress Versions of Both Tests
Both tests have stress versions used to evaluate chest pain and suspected coronary artery disease. A stress EKG records your heart’s electrical activity while you exercise on a treadmill, looking for changes that suggest reduced blood flow during exertion. A stress echocardiogram does the same but adds ultrasound images of the heart before and immediately after exercise, letting doctors see whether any part of the heart muscle stops contracting normally under stress.
The stress echo is significantly more accurate. In a study of 302 patients presenting with acute chest pain, the stress echo correctly identified 80% of patients as low-risk compared to just 31% for the exercise EKG alone. When the stress echo flagged a positive result, 84% of those patients turned out to have significant coronary artery disease on follow-up angiography, compared to 56% for a positive exercise EKG. Patients who underwent stress echo were also far less likely to need additional testing afterward (16% vs. 52%).
Which Test Comes First
In an emergency, the EKG almost always comes first. American Heart Association guidelines recommend that anyone arriving at a medical facility with chest pain should have an EKG performed and interpreted within 10 minutes. The reason is speed: the EKG can identify a type of heart attack called a STEMI that requires immediate intervention to reopen a blocked artery. Minutes matter in that scenario, and no other test delivers that information as fast.
An echocardiogram often follows when the initial EKG doesn’t explain the symptoms or when doctors need to rule out other causes of chest pain, such as aortic dissection, fluid around the heart, or stress cardiomyopathy. In non-emergency settings, your doctor might order an EKG as a first-line screening tool because it’s fast and inexpensive, then add an echocardiogram if the results suggest something that needs a closer structural look.
Cost Differences
An EKG is one of the least expensive cardiac tests available, often costing between $50 and $250 without insurance. An echocardiogram is considerably more expensive because it involves specialized equipment, a trained sonographer, and a longer interpretation process. Out-of-pocket costs for a standard echo typically range from several hundred to over a thousand dollars. Most insurance plans cover both tests when ordered for a documented medical reason, though echocardiograms may face more scrutiny for medical necessity than a routine EKG.
Why Doctors Often Order Both
These tests complement each other because they reveal different layers of heart function. An EKG might show an abnormal rhythm, but it can’t tell your doctor why the rhythm is abnormal. Is the heart enlarged? Is a valve malfunctioning? Is the muscle too thick? Those answers come from the echo. Conversely, an echocardiogram can show that a heart valve is leaking, but it won’t reveal whether that leak is causing a dangerous rhythm disturbance. The EKG fills that gap. Think of the EKG as reading the heart’s electrical wiring and the echocardiogram as watching the plumbing and mechanics in action.