What Is an Echocardiogram? A Cardiologist's Guide to the Heart Ultrasound

The echocardiogram is the workhorse of modern cardiology. If you have ever been sent for a heart test that involved warm gel, a probe moved across your chest, and a monitor showing grainy black-and-white pictures of a beating heart, you have had one. I order echos almost every day. Patients often leave the appointment unsure what was actually measured, what the report means, or why I ordered it in the first place. This is a plain-language walkthrough of what an echocardiogram is, what it can and cannot show, and how I use the results to make clinical decisions.

What an Echocardiogram Is

An echocardiogram is an ultrasound of the heart. A small probe called a transducer emits high-frequency sound waves, the waves bounce off cardiac structures and blood, and a computer assembles the returning signals into real-time images. No radiation, no contrast dye (in most cases), no needles. A typical study takes 30 to 45 minutes and is performed by a sonographer while the patient lies on their side on an exam table. The images are later interpreted by a cardiologist who writes the formal report.

Four types of information come out of a standard transthoracic echocardiogram. First, structure — the size and thickness of the four chambers, the appearance of the valves, the pericardium, and the great vessels. Second, function — how well the left and right ventricles contract and relax, quantified most commonly as ejection fraction. Third, flow — the velocity and direction of blood through the valves, which identifies stenosis (narrowing) and regurgitation (leaking) and allows estimation of pressures inside the heart. Fourth, pressures — derived non-invasively using Doppler measurements, including pulmonary artery pressure and right atrial pressure.

Why I Order Echocardiograms

Almost every new patient in my office gets an echo, because it answers so many questions at once. The specific reasons I order them fall into a few categories.

Symptom Evaluation

Shortness of breath, chest pain, palpitations, fatigue, syncope, and leg swelling all deserve evaluation for an underlying cardiac cause. An echo rapidly identifies or excludes the big structural and functional culprits — heart failure, valvular disease, pericardial effusion, pulmonary hypertension, cardiomyopathy, and intracardiac shunts.

Risk Stratification

Patients with hypertension, diabetes, atrial fibrillation, prior heart attack, or a strong family history often need baseline imaging to understand their current cardiac structure and function. An echo quantifies left ventricular mass, which is a powerful predictor of future cardiovascular events independent of blood pressure itself. It also picks up silent dysfunction in patients who feel well but have early disease.

Monitoring Known Disease

Aortic stenosis, mitral regurgitation, cardiomyopathy, and heart failure all progress, and the echo is how we track that progression. Serial studies at 6-month, 1-year, or 2-year intervals let me know when it is time to escalate therapy or consider intervention. For a patient with moderate aortic stenosis, the echo is what tells me when the valve has tipped into the severe range that warrants a conversation about TAVR or surgical valve replacement.

Pre-Operative and Pre-Chemotherapy Assessment

Patients going for major non-cardiac surgery sometimes need an echo to document LV function, and patients starting cardiotoxic chemotherapy — anthracyclines, trastuzumab, some tyrosine kinase inhibitors — need baseline and serial echos to detect early cardiotoxicity before it becomes symptomatic heart failure.

The Key Measurements in Your Report

Echo reports can be dense, and most patients see numbers they do not understand. The measurements that matter most in everyday cardiology are the ones I explain below.

Left Ventricular Ejection Fraction (LVEF)

This is the percentage of blood in the left ventricle that gets pumped out with each beat. Normal is 55 to 70 percent. Mildly reduced is 40 to 54 percent. Moderately reduced is 30 to 39 percent. Severely reduced is below 30 percent. Heart failure is classified by LVEF into four categories per the 2022 AHA/ACC/HFSA guideline: HFrEF (reduced, ≤40 percent), HFmrEF (mildly reduced, 41 to 49 percent), HFpEF (preserved, ≥50 percent), and HFimpEF (improved, a previously reduced LVEF ≤40 percent that has recovered to above 40 percent). The classification matters because the treatment pathways differ, and HFimpEF patients in particular should continue guideline-directed therapy even after their ejection fraction recovers.

Left Ventricular Wall Thickness

Normal wall thickness is less than 1.1 cm in men and slightly less in women. Thickening beyond that suggests left ventricular hypertrophy, most commonly from uncontrolled high blood pressure but also seen in hypertrophic cardiomyopathy, infiltrative diseases like amyloidosis, and aortic stenosis. Hypertrophy is not benign — it increases the risk of heart failure, arrhythmia, and sudden death.

Valve Findings

Each valve (aortic, mitral, pulmonic, tricuspid) is graded for stenosis and regurgitation on a trace-to-severe scale. Mild regurgitation of any valve is extremely common and often clinically irrelevant. Moderate or severe findings warrant attention. Aortic stenosis is graded by peak velocity, mean gradient, and valve area — severe AS means peak velocity ≥4 m/s, mean gradient ≥40 mmHg, or valve area ≤1.0 cm². Mitral regurgitation severity depends on vena contracta width, regurgitant volume, and effective regurgitant orifice area.

Diastolic Function

Diastole is the filling phase of the heartbeat. When the left ventricle becomes stiff — from hypertension, age, diabetes, or infiltration — it fills poorly even though its squeezing function is preserved. Echo assesses diastolic function with Doppler measurements of mitral inflow and tissue Doppler imaging of the mitral annulus. Grade I is mild diastolic dysfunction. Grade II and III represent progressively elevated filling pressures and are the echocardiographic hallmark of HFpEF.

Right Ventricular Function and Pulmonary Pressure

Right ventricular size and function matter in pulmonary hypertension, right-sided heart failure, congenital heart disease, and after pulmonary embolism. Pulmonary artery systolic pressure is estimated from the tricuspid regurgitation jet velocity. Normal is less than 35 mmHg; elevated values prompt further evaluation for the cause.

Left Atrial Size

Left atrial volume index above 34 mL/m² indicates left atrial enlargement, which is both a marker of chronic elevated filling pressures and an independent risk factor for atrial fibrillation and stroke.

When a Standard Echo Is Not Enough

The transthoracic echocardiogram I have been describing works well for most patients, but in some situations it is not the right tool.

Transesophageal echocardiogram (TEE) involves passing an ultrasound probe down the esophagus. Because the probe sits right behind the heart, image quality is exceptional. I order a TEE when I need high-resolution views of the mitral valve, the left atrial appendage (for example to rule out clot before cardioversion for atrial fibrillation), prosthetic valves, or suspected endocarditis that the transthoracic study did not resolve. TEE requires sedation and carries small procedural risks.

Stress echocardiogram combines echo imaging with either exercise on a treadmill or pharmacologic stress (usually dobutamine). It is used to evaluate for inducible ischemia in patients with chest pain and intermediate pre-test probability of coronary disease, to assess functional severity of valvular disease, and to test contractile reserve in low-gradient aortic stenosis.

Contrast-enhanced echocardiogram uses agitated saline or a dedicated ultrasound contrast agent. Agitated saline is excellent for detecting patent foramen ovale and other right-to-left shunts. Ultrasound contrast agents improve endocardial border definition in patients with technically difficult studies, which makes ejection fraction measurement far more accurate.

Cardiac MRI is sometimes preferred over echo for tissue characterization — distinguishing myocardial inflammation (myocarditis) from infiltration (amyloid, sarcoid), assessing scar burden after a heart attack, and evaluating complex congenital heart disease. Echo is faster, cheaper, and portable, but MRI gives information echo cannot.

Limitations of Echocardiography

Echo has some meaningful limitations. Image quality depends on body habitus — obesity, large breast tissue, lung disease with hyperinflation, and chest wall deformities all make image acquisition harder. Ejection fraction is operator-dependent and has inter-reader variability of several percentage points. Coronary arteries themselves are generally not visualized on echo, so coronary disease must be inferred from wall motion abnormalities or confirmed by a different test. Small intracardiac masses and vegetations can be missed on transthoracic echo and require TEE for confident evaluation.

These limitations are why I sometimes order additional imaging even when the echo reads as "normal." A normal echo does not rule out coronary disease, early cardiomyopathy with normal ejection fraction, or small intracardiac thrombi. Clinical judgment always layers on top of any single test.

What to Expect During the Study

You do not need to fast for a transthoracic echo. You will be asked to remove your shirt and change into a gown. The sonographer will place three ECG electrodes on your chest and have you lie on your left side. Warm ultrasound gel is applied, and the probe is moved across your chest from several positions — below the sternum, between the ribs, and at the base of the neck for some views. You may be asked to hold your breath briefly or turn slightly. Occasionally the sonographer will apply firm pressure to get between ribs. It is not painful but can be mildly uncomfortable. Expect to be in the exam room for 30 to 45 minutes, sometimes longer for technically difficult studies or when the sonographer spots something that needs extra imaging.

If your cardiologist ordered a stress echo, the procedure is longer and includes exercise or medication administration. If it is a TEE, plan for sedation, an adult to drive you home, and nothing by mouth for six to eight hours beforehand.

What This Means for You

An echocardiogram is one of the most informative, safest, and most cost-effective tests in medicine. If your cardiologist orders one, it is usually because they want a detailed look at structure and function that no other test can provide as quickly or as safely. Ask for a copy of the report and ask your clinician to walk you through the key measurements — ejection fraction, valve findings, wall thickness, diastolic function, and atrial size are the ones that almost always tell the clinical story.

If your echo comes back completely normal, that is reassuring but not absolute. If it shows an abnormality, do not panic. Most abnormalities are either mild and not clinically important, or manageable with medication and lifestyle change. The rare findings that require urgent intervention — severe valve disease, severely reduced ejection fraction, large pericardial effusion — will be communicated to you promptly. An echo is usually the start of a conversation, not the end of one.

References

1. Mitchell C, Rahko PS, Blauwet LA, et al. Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults: recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2019;32:1-64.

2. Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015;28:1-39.

3. Nagueh SF, Smiseth OA, Appleton CP, et al. Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2016;29:277-314.

4. Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease. J Am Coll Cardiol. 2021;77:e25-e197.

5. Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure. Circulation. 2022;145:e895-e1032.

6. Pellikka PA, Arruda-Olson A, Chaudhry FA, et al. Guidelines for performance, interpretation, and application of stress echocardiography in ischemic heart disease. J Am Soc Echocardiogr. 2020;33:1-41.

7. Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination. J Am Soc Echocardiogr. 2013;26:921-964.

8. Porter TR, Mulvagh SL, Abdelmoneim SS, et al. Clinical applications of ultrasonic enhancing agents in echocardiography. J Am Soc Echocardiogr. 2018;31:241-274.