An echocardiogram (often called an “echo”) is an ultrasound scan of the heart. It uses sound waves to create real-time moving images of the heart’s structure and function, without using radiation. It is one of the most commonly used cardiac investigations and is almost always performed as part of the assessment following a cardiac arrest.
**What it measures**
An echocardiogram can assess:
– **Cardiac chambers:** the size and shape of the four chambers of the heart
– **Ejection fraction:** the percentage of blood pumped out of the left ventricle with each beat, which is the primary measure of cardiac function (a normal ejection fraction is typically above 55%)
– **Wall motion:** whether all areas of the heart muscle are contracting normally, or whether some areas are weak or not moving (which may indicate previous heart attack or cardiomyopathy)
– **Heart valves:** whether the valves are opening and closing properly, whether there is leakage (regurgitation) or narrowing (stenosis)
– **Pericardium:** whether there is fluid around the heart (pericardial effusion)
– **Aorta:** the diameter of the main artery leaving the heart
**Types of echocardiogram**
– **Transthoracic echocardiogram (TTE):** the most common type, where a probe is placed on the chest wall
– **Transoesophageal echocardiogram (TOE):** the probe is passed into the oesophagus for a clearer view, used when TTE is inconclusive
– **Stress echocardiogram:** images are taken at rest and during or after exercise or medication-induced stress, to look for changes in heart function
**After cardiac arrest**
Ejection fraction is particularly important after cardiac arrest because reduced cardiac function influences decisions about ICD implantation, medication, and follow-up. Serial echocardiograms may be needed to monitor whether function improves over time.
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