Cardiac tests — what each one tells your cardiologist

An ECG is a 10-second recording of the heart's electrical activity and excels at diagnosing rhythm problems, ongoing or previous heart attacks, thickened heart muscle, and certain inherited electrical conditions.

What it cannot do is show how the heart is moving or pumping, or whether the coronary arteries are narrowed at rest. A normal ECG between symptomatic episodes does not rule out arrhythmia or coronary disease — for those, you usually need a recording during symptoms (Holter or patch monitor) or an imaging test such as an echo, CT or MRI.

An echocardiogram is an ultrasound scan of the heart, showing the size and pumping function of each chamber, how well the heart valves are working, the thickness of the muscle, and the pressure in the pulmonary arteries.

Echocardiography uses no radiation, no needles and no contrast in its standard form, making it completely safe and repeatable. A standard scan takes 20 to 40 minutes. A more detailed variant — the transoesophageal echo — passes a probe down the throat for a closer look and is reserved for specific situations where the standard scan is limited.

A standard exercise ECG records electrical activity while you walk on a treadmill, looking for electrical signs of inadequate blood supply during exertion. It is inexpensive and widely available but only modestly accurate — particularly in women.

A stress echocardiogram combines exercise (or a chemical that mimics it) with ultrasound imaging before, during and after the stress. The cardiologist looks for areas of heart muscle that move less well under load, which signals a meaningful blockage in the artery supplying that region. Stress echo is significantly more accurate and has become the preferred functional test in most UK practice.

In most patients with new chest pain, NICE recommends starting with a CT coronary angiogram — a non-invasive scan that gives a detailed look at the coronary arteries in about ten minutes. It is excellent at ruling out significant coronary disease and identifying who needs further investigation.

An invasive coronary angiogram is reserved for patients with definitive evidence of significant disease on CT or stress testing, those with high-risk symptoms such as unstable angina or a recent heart attack, or those in whom CT cannot be performed reliably. The big advantage of the invasive angiogram is that it can move directly to treatment — placing a stent in the same procedure if a significant blockage is confirmed.

A coronary calcium score is a quick, low-dose CT scan that measures calcified plaque in the coronary arteries and translates the result into a 10-year risk of heart events. It takes about ten minutes, requires no contrast and no needles.

It is most useful in middle-aged adults at intermediate cardiovascular risk where the decision about starting a statin is genuinely uncertain — a score of zero argues strongly against starting, while a high score (over 100) argues firmly for it. It is not generally recommended in low-risk under-40s or in patients with established heart disease, where treatment is already indicated regardless.

Cardiac MRI is the most detailed imaging test for the heart muscle and uses no radiation. Its unique strengths are detecting scar tissue from previous heart attacks, identifying inflammation such as myocarditis, characterising cardiomyopathies, and measuring ejection fraction with the highest accuracy.

It is particularly valuable when an echocardiogram is inconclusive, when scar or inflammation is suspected, or when an inherited heart condition is being assessed. The scan takes 45 to 60 minutes, requires you to lie still and follow breath-hold instructions, and usually involves an injection of contrast.

Modern CT coronary angiograms use very low radiation doses — typically equivalent to 6 to 18 months of natural background radiation — and protocols continue to improve year on year. For most patients, the diagnostic benefit comfortably outweighs the small theoretical risk.

In younger patients, women of childbearing age and patients needing multiple scans, the radiation question is weighed more carefully. Cardiac MRI is often used instead when radiation avoidance is a priority, although the choice ultimately depends on the clinical question being asked.

Avoid caffeine for at least 12 hours before the test and a heavy meal for 3 hours. Wear comfortable clothes and shoes suitable for walking. Some medications, particularly beta-blockers, may need to be paused on the morning of the test — your cardiologist will advise specifically.

Bring a list of your medications. The test itself takes 30 to 60 minutes including preparation and recovery; the exercise portion is usually 6 to 15 minutes. Most people are back to normal activity immediately afterwards.

An invasive coronary angiogram is performed under local anaesthetic with mild sedation, almost always via the wrist (radial approach). A thin tube is guided up to the heart and X-ray dye is injected into the coronary arteries so the cardiologist can see narrowings or blockages in real time.

The procedure takes 20 to 40 minutes and is done as a day case. If a significant narrowing is found, a stent can often be placed in the same sitting. You can usually go home within a few hours, and most patients are back to normal activity within a couple of days — slightly longer if a stent has been placed.

In private practice, most cardiac test results — ECG, echocardiogram, stress echocardiogram — are reported on the day of the test, with a formal letter sent within 24 to 48 hours. CT coronary angiograms and cardiac MRIs typically take 2 to 5 working days for the full report.

If an urgent result is identified during the scan — a critical narrowing, for example — you will be told immediately rather than waiting for the formal report. Time-critical findings always trigger same-day contact and onward planning.

The right test depends on your age, risk factors and the character of the pain. For most adults with new exertional chest pain, CT coronary angiogram is first-line under NICE guidance because it can both rule in and rule out coronary disease quickly and non-invasively.

If your pain is unlikely to be cardiac but further reassurance is wanted, an echocardiogram and exercise ECG may be sufficient. For patients with known coronary disease and a question of new ischaemia, a stress echocardiogram or cardiac MRI is usually preferred. The choice should always be discussed in a consultation — there is no one-size-fits-all answer.

No — a normal ECG between symptomatic episodes is reassuring but does not rule out coronary disease, intermittent arrhythmia, valve disease or cardiomyopathy. The ECG is a snapshot, not a film.

Many patients with significant coronary narrowings have completely normal resting ECGs. Many patients with palpitations have normal ECGs between episodes. If symptoms persist despite a normal ECG, more targeted testing — imaging, ambulatory rhythm monitoring or stress testing — is the appropriate next step.