What is strain imaging?
Strain imaging is an advanced form of heart ultrasound that measures how much the heart muscle actually stretches and shortens with each beat. A standard echocardiogram reports the ejection fraction, which is how much blood is pushed out per beat, but that figure can look normal even when the muscle has already begun to weaken. Strain imaging follows tiny patterns in the muscle from frame to frame and produces a detailed map, often shown as a colour diagram, that reveals early or localised weakness before it becomes obvious in any other way.
Why is it done?
Because it detects damage early. It is used to pick up the first effects of certain cancer treatments on the heart, so that treatment can be adjusted before the muscle is significantly harmed; to distinguish between causes of a thickened heart muscle, including infiltrative diseases such as amyloidosis; to detect early damage from high blood pressure, diabetes or valve disease; to assess the effect of a previous heart attack; and to follow patients on heart failure treatment. It is also used to decide when the timing is right for valve surgery.
What happens on the day?
Strain imaging is done as part of an ordinary echocardiogram, so nothing extra is required from you and no injections, radiation or dye are involved. You undress to the waist, a gown is provided, and you lie on your left side on a couch. Sticky ECG dots are placed on the chest, warm gel is applied and the sonographer or cardiologist moves the probe over your chest, asking you at times to hold your breath briefly or lie still. Good-quality images are important for the analysis, so the study may take a little longer than a routine scan, usually thirty to forty-five minutes in total.
What to expect afterwards
The gel is wiped off, you dress, and you can eat, drive and continue your day immediately with no restrictions. The recordings are then analysed on a workstation, which takes some time, and your cardiologist discusses the report with you at your consultation. Because the technique is sensitive, results are always interpreted together with your symptoms, your other tests and, where relevant, with previous strain measurements to see whether anything has changed.
Possible complications
There are none of consequence. Ultrasound uses sound waves rather than radiation, nothing is injected and there are no known harmful effects at diagnostic levels. Minor discomfort can come from the cool gel, from pressure of the probe between the ribs, from lying on your side, or from mild skin irritation where the ECG dots were. In some patients, particularly with lung disease or a larger build, the image quality is not good enough for reliable strain analysis, and another test such as a cardiac MRI may be recommended instead.
This information does not replace a consultation. Please discuss your own risks and options with your cardiologist.