What Is an Echocardiogram? What It Shows and When You Need One.

An echocardiogram is an ultrasound study of the heart performed in real time, producing a moving image of cardiac structure and function that no other non-invasive test can match in a single examination. The study takes 30 to 60 minutes, requires no radiation, no injection, and no special preparation. It is performed by a cardiac sonographer and interpreted by a cardiologist or echocardiographer trained in cardiac imaging.

The Mechanism

The echocardiogram works on the same physical principle as any diagnostic ultrasound. A transducer placed on the chest wall emits high-frequency soundwaves, typically between 1 and 5 megahertz for cardiac imaging. Those soundwaves pass through tissue and reflect off boundaries between structures with different acoustic properties, such as the junction between blood and cardiac muscle, or between the heart wall and the pericardium. The reflected waves return to the transducer and are converted into an image. Because the heart is continuously moving, the echocardiogram captures that motion in real time, which is what makes it uniquely informative for cardiac assessment.

The standard transthoracic echocardiogram uses multiple acoustic windows: the parasternal view from the left sternal border captures long-axis and short-axis views of the heart; the apical views from the left lateral chest wall show all four chambers simultaneously; the subcostal view from below the ribcage is particularly useful in patients where standard windows are limited by lung or chest wall configuration. A technically complete study incorporates views from all of these positions to capture different structural planes and to quantify blood flow through each valve using Doppler techniques.

Doppler echocardiography measures the velocity and direction of blood flow within the heart. Pulsed-wave Doppler identifies flow at specific points in the circulation, while continuous-wave Doppler captures peak velocities across high-gradient structures like stenotic valves. Color Doppler superimposes a color map of flow direction and velocity onto the two-dimensional image, making valvular regurgitation visible as a jet of retrograde flow. Tissue Doppler imaging measures the velocity of myocardial motion itself, which is the basis for assessing diastolic function.

The transoesophageal echocardiogram (TEE) uses a miniaturized transducer on a flexible probe passed into the oesophagus to image the heart from directly behind it. Without the chest wall and lungs as acoustic barriers, TEE provides substantially higher resolution, particularly of posterior structures like the mitral valve, left atrial appendage, and aortic root. TEE is used when transthoracic image quality is insufficient or when specific structures require higher resolution, and it requires sedation or anaesthesia.

What the Evidence Shows

Ejection fraction measurement and clinical outcomes. The left ventricular ejection fraction (EF) is the fraction of blood ejected from the left ventricle with each contraction, expressed as a percentage. Normal EF is above 55 percent. An EF below 40 percent defines heart failure with reduced ejection fraction (HFrEF), the threshold at which guideline-directed medical therapy with beta-blockers, ACE inhibitors or ARBs, and mineralocorticoid receptor antagonists has demonstrated survival benefit in randomized trials. An EF in the range of 40 to 54 percent is classified as heart failure with mildly reduced ejection fraction (HFmrEF), a category where the evidence base is still developing. 4 / Promising

The prognostic significance of EF was established in the Studies of Left Ventricular Dysfunction (SOLVD) trials, which enrolled patients with EF at or below 35 percent and showed that enalapril reduced mortality and heart failure hospitalizations compared with placebo (SOLVD Investigators, NEJM 1991). The EF threshold of 35 percent or below also defines eligibility for implantable cardioverter-defibrillator (ICD) therapy based on the MADIT II trial, which showed that prophylactic ICD implantation in patients with ischemic cardiomyopathy and EF at or below 30 percent reduced all-cause mortality by 31 percent (Moss et al., NEJM 2002).

Diastolic function and heart failure with preserved EF. An echocardiogram in a hypertensive patient that reports only “normal EF” without diastolic function assessment is an incomplete study. Heart failure with preserved ejection fraction (HFpEF) is defined by symptoms of heart failure in the presence of an EF above 50 percent, elevated filling pressures, and evidence of diastolic dysfunction. The echocardiographic parameters used to grade diastolic function include the E/A ratio (the ratio of early to late transmitral filling velocity), the tissue Doppler E’ velocity at the mitral annulus, the E/e’ ratio (used to estimate left ventricular filling pressure), and left atrial volume index.

The 2016 ASE/EACVI guidelines for the evaluation of diastolic function established that an E/e’ ratio above 14 is associated with elevated filling pressures, with a sensitivity and specificity for invasive filling pressure elevation of approximately 72 and 79 percent respectively (Nagueh et al., JASE 2016). An enlarged left atrial volume index (above 34 mL/m2) provides additional evidence of chronically elevated left heart filling pressures. These parameters together form the basis for diagnosing diastolic dysfunction, which affects 20 to 30 percent of hypertensive adults, many of whom have no symptoms at the time the echocardiogram is performed.

Valvular heart disease quantification. The echocardiogram is the primary tool for diagnosing and grading the severity of valvular heart disease. Aortic stenosis severity is graded by peak jet velocity, mean gradient, and aortic valve area. Severe aortic stenosis is defined as a peak velocity above 4 m/s, mean gradient above 40 mmHg, and aortic valve area below 1.0 cm2. These thresholds, established through correlation with outcomes and hemodynamic studies, determine timing of valve replacement. The 2021 ACC/AHA valve guidelines recommend intervention for severe aortic stenosis in symptomatic patients and in asymptomatic patients with EF below 50 percent or very severe stenosis (peak velocity above 5 m/s) (Otto et al., Circulation 2021). 4 / Promising

Mitral regurgitation severity grading similarly uses echocardiographic measures: effective regurgitant orifice area, regurgitant volume, and regurgitant fraction. Severe primary mitral regurgitation with preserved EF and left ventricular enlargement prompts surgical referral before EF deteriorates, since functional recovery is less complete once EF falls below the normal range.

Echocardiography before noncardiac surgery. The utility of preoperative echocardiography in men without known cardiac disease scheduled for elective major noncardiac surgery depends heavily on the individual’s risk profile. A 2021 systematic review in the Canadian Journal of Cardiology found that routine preoperative echocardiography changed management in 11 to 14 percent of patients but identified clinically significant new findings (severe LV dysfunction, severe valvular disease) in a smaller subset. The American College of Cardiology guidelines do not recommend routine preoperative echocardiography in asymptomatic patients before elective surgery, but do support it when clinical examination suggests new or unstable cardiac disease.

What echocardiography cannot show. The echocardiogram does not visualize coronary anatomy. It shows the consequences of coronary disease, specifically wall motion abnormalities in territories supplied by obstructed vessels, but cannot determine whether a given vessel is stenosed or by how much. Coronary artery calcium scoring or coronary CT angiography is required for that assessment. Additionally, standard transthoracic echocardiography has image quality that varies significantly with body habitus, emphysema, and chest wall anatomy. In patients with poor acoustic windows, findings may be limited or inconclusive, and alternative imaging (cardiac MRI, TEE, or nuclear imaging) may be required.

What to Do This Week

1. If your physician has ordered an echocardiogram and you have not been told what parameters will be reported, ask specifically about these four: ejection fraction, left ventricular wall thickness, diastolic function (E/e’ ratio and E’ velocity), and valve function. These are the four categories that carry the most clinical weight in the outpatient cardiology setting.

2. If you have received a report stating “normal EF” and you have hypertension, ask your physician whether diastolic function was assessed and what the E/e’ ratio showed. An EF above 55 percent with an elevated E/e’ ratio and a dilated left atrium suggests early HFpEF, not a normal study.

3. If you have never had an echocardiogram and you have had hypertension for two or more years, ask your physician whether a baseline study is clinically indicated. The purpose of a baseline echocardiogram in a hypertensive patient is to detect left ventricular hypertrophy and diastolic dysfunction before symptoms develop and to establish a reference point for future comparisons.

4. If you have had a previous echocardiogram and your current physician does not have access to the prior report, request a copy. The comparison between studies at different time points often carries more clinical information than any single result in isolation. An EF that has declined from 65 percent to 52 percent is not a “normal” study, even though 52 percent falls within the normal range.

5. If you are told your echocardiogram was technically limited due to poor acoustic windows, ask whether alternative imaging is warranted. A technically inadequate study that reports “EF appears normal” is not the same as a technically adequate study demonstrating a measured EF of 60 percent.

Stress Echocardiography: Adding the Functional Dimension

A standard resting echocardiogram assesses cardiac structure and function at baseline. Stress echocardiography adds a physiological challenge — typically treadmill or bicycle exercise, or pharmacological stress with dobutamine in patients who cannot exercise — and repeats the echocardiographic acquisition immediately after or during peak stress. The purpose is to unmask ischemic wall motion abnormalities that are absent at rest but appear when myocardial oxygen demand exceeds the supply the stenosed vessel can deliver.

The diagnostic performance of stress echocardiography in patients with intermediate probability of obstructive coronary artery disease is well-established. A 2016 meta-analysis by Picano and colleagues in JACC: Cardiovascular Imaging, pooling 75 studies with over 29,000 patients, reported sensitivity of 80 to 85 percent and specificity of 84 to 86 percent for detecting obstructive coronary artery disease. 4 / Promising The sensitivity is lower than invasive coronary angiography but substantially higher than exercise ECG alone (sensitivity approximately 45 to 68 percent), making stress echocardiography a preferred modality when the resting ECG is abnormal, when the patient takes digoxin, or when localizing the territory of ischemia is clinically important for revascularization planning.

Two specific scenarios where stress echocardiography provides information the resting study cannot: first, a patient with dyspnea on exertion in whom the resting echocardiogram is normal — stress can reveal exercise-induced diastolic dysfunction or new wall motion abnormalities not present at rest, distinguishing cardiac from pulmonary or deconditioning causes; second, a patient with moderate aortic stenosis at rest where the resting gradient appears to underestimate hemodynamic severity — dobutamine stress echocardiography can differentiate true severe stenosis from pseudo-severe stenosis in low-flow low-gradient aortic stenosis, which changes the decision about valve replacement.

Interpretation of stress echocardiography requires pairing the echocardiographic images with the clinical response: heart rate and blood pressure trajectory during stress, symptoms reported during the protocol, and any arrhythmia. A normal ECG response with a new segmental wall motion abnormality on echocardiography represents ischemia in a patient whose ECG alone would have been misread as negative.

What a Complete Echo Report Should Include

A complete echocardiogram report should contain the following structured data. If key elements are absent and the clinical indication is relevant, the absence should be flagged to the interpreting cardiologist:

Left ventricle: internal dimensions at end-diastole and end-systole; wall thickness at septum and posterior wall; ejection fraction measured by biplane Simpson’s method with a stated numeric value, not estimated qualitatively.

Diastolic function: E/A ratio; tissue Doppler E prime velocity at the septal and lateral mitral annulus; E/e prime ratio; left atrial volume index; graded as normal, grade I, grade II, or grade III diastolic dysfunction per 2016 ASE/EACVI criteria.

Right ventricle: RV linear dimensions; systolic function assessed by TAPSE (tricuspid annular plane systolic excursion) or S prime velocity; right atrial size.

Valves: all four valves assessed and graded; severity of any stenosis by peak velocity, mean gradient, and valve area; severity of any regurgitation by current grading criteria (mild/moderate/severe).

Pericardium: presence or absence of effusion; if present, size and any evidence of hemodynamic significance.

Aorta: aortic root dimension at the sinuses of Valsalva; ascending aorta dimension if visualized — relevant in patients with hypertension, bicuspid aortic valve, or family history of aortic disease.

A report returning three sentences summarizing “normal LV function, EF 58 percent, no significant valvular disease” in a hypertensive patient evaluated for dyspnea is not diagnostically complete. Patients who receive such summaries without the diastolic parameters, right heart assessment, or aortic dimensions should ask their physician to request a complete structured report from the interpreting cardiologist or, if necessary, a repeat study at a facility with structured reporting protocols.

The echocardiogram is the most information-dense non-invasive cardiac test available, but its value depends entirely on the completeness of the study performed, the technical quality of the images obtained, and the clinical context in which the results are interpreted. A reported EF, without diastolic parameters and without comparison to prior studies, answers only part of the question.