A CMR scan is a sophisticated type of scan that does not use any radiation. The scanner uses a large magnetic tube to align the body’s protons – small particles contained within each hydrogen atom, found in every water molecule – and then uses short bursts of radio waves directed at specific areas of the body. These knock the protons out of alignment, which realign when the radio waves are turned off. This sends out radio signals that are picked up by receivers.
These signals provide the exact location of each proton and help distinguish between the different types of tissue inside the body, because the protons of each type of tissue realign at different speeds and produce a different signal. Computers then produce a detailed image of the body. These CMR images allow doctors to assess cardiac function, scarring of the heart muscle and a lack of blood supply (myocardial ischaemia).
CMR is considered the gold standard imaging modality for patients with cardiomyopathy as it allows for better visualisation of the heart and is the only way of detect the scarring of heart muscle that is often seen in these conditions.
A CMR is performed to obtain a comprehensive analysis of heart structure, function and diseases. In addition to diagnostic reasons above, there are other times you may need a CMR, including when your cardiologist needs to:
• Check for damage to your heart after a heart attack or areas that lack blood flow because of heart artery blockages.
• Pinpoint a location they need to treat during an ablation.
• See how much your treatment is helping your heart.
• Plan a procedure or treatment on your heart.
• Evaluate the success of a recent surgery.
• Check to see how a disorder has affected your heart since the last scan
Your scan should take between 45 - 60 minutes.
The machine may do several scans, with each one lasting a few minutes. You may be asked to hold your breath for part of the scan.
You’ll need to lie on your back without moving during scans. The machine is loud and may sound like an electronic video game or something pounding around you, but you’ll be able to communicate (through a microphone and headphones or intercom) with the person operating the machine.
They may put a call button in your hand that you can squeeze if you need to contact the person doing the scan. You may be able to listen to music through the headphones they put on you.
Risks of a CMR?
CMR is a safe procedure. If you took a sedative to relax, you may feel tired until the effects of the pill wear off. If not, you can return to your normal activities.
If you received contrast through an intravenous line (IV) you might have a metal-type taste for a little while or some bruising or irritation where the IV was put in.
Rarely, people may have nausea or a headache from the contrast they got in their IV.