Coronary artery disease can cause blood flow problems and heart attacks. Several imaging techniques can be used to visualise the area of dead myocardium – the infarct – but cardiac MR is one of the most suitable because it can visualise the dead area at high resolution. There are a number of myocardial diseases associated with dilatation of the ventricle, disproportionate thickening of the myocardium and structural abnormalities of the right ventricle that predispose to arrhythmias. These pathologies, or others not listed here, can cause heart failure and arrhythmias. Ultrasound of the heart is usually the first step in the investigation of these symptoms, but there may be unanswered questions and cardiac MRI is therefore an important part of the follow-up imaging. Cardiac MRI is the most accurate of all clinical imaging modalities to measure cardiac dilatation, function and myocardial mass. And in the case of myocardial injury, it can detect abnormalities caused by both recent (acute) and previous (chronic) damage.
Cardiac MR scans may be needed to investigate a number of diseases affecting the heart muscle. In addition to the detection and imaging of myocardial infarction due to coronary artery disease and other causes, heart failure and abnormal myocardial congestion may also require cardiac MR scanning in addition to cardiac ultrasound. Follow-up of congenital heart disease may also require cardiac MR every few years.
The scan can accurately determine the heart function, the ventricles and, if necessary, the atrial dilatation. The amount and location of oedema and scarring from previous damage to the myocardium can be detected. The pattern of stacking may differ between different pathologies, which aids diagnosis.
In congenital heart disease patients, the focus is often on the right ventricle, the valve leading to the pulmonary artery, and possible shunt circulation – the latter is the unwanted flow of blood from one side of the heart to the other side, the extent of which can also be detected.
The European Society of Cardiology has a number of recommendations on when to perform cardiac MR. In cases that are not entirely clear, our cardiac MR specialists will be happy to advise you or your doctor on the need for cardiac MR scanning.
The test usually takes 60 minutes. The measurement time will depend on the questions that the cardiac MR scan is designed to answer. The length of the measurement is also affected by the heart rate. If there are a lot of extra beats or irregular heartbeats, this can make data collection and assessment more difficult and may rarely require a repeat scan.
Preliminary medication can increase the chances of a successful test in patients with arrhythmias. During the scan, special ECG electrodes used in MR are attached and the breathing movements are monitored with a belt passed through the abdomen. Data acquisition is synchronous with the ECG, and breath-holding is used to eliminate “movement abnormalities” caused by respiratory movements. Each breath-hold takes about 8-15 seconds.
The test involves a strong sound impact, so our patients are provided with noise-cancelling earphones. During the cardiac MR scan, we communicate with our patients continuously.
The scan takes approximately 1.5 hours.
The contrast agent to be given, depending on the test questions, is not the usual iodine, but a rare earth metal, gadolinium. The substance does not react with the body, and most of it is eliminated by the kidneys within a few hours. Rarely, there is an allergic reaction, for which the MR facility is fully equipped. Allergies may mostly take the form of a minor rash, with the occasional transient nausea. If a contrast-enhanced cardiac MR scan is planned, the patient’s renal function will be determined beforehand.
You are allowed to drink fluids before the test, but we recommend that you eat plenty of fluids 4 hours before the test. The examiner should be informed of the type of metal implants being placed before the MR scan.
Thoracic wire sutures, artificial valves and coronary stents inserted during heart surgery are not usually a problem, but more complex medical devices such as pacemakers, ICDs, hearing implants, neurostimulators may cause problems. These may require limited or sometimes no MRI scans. Careful consideration is also needed for brain aneurysm angioplasty clips – older types cannot be MRIed.
If you have an implanted metal in your body, please enquire in advance at our Call Centre or bring the documentation with you to the scan. For a cardiac MRI scan, most of your clothing will need to be removed for the chest ECG, so it is advisable to wear less metal on your person e.g. push-up bra instead of sports bra for ladies. Some make-up also contains metal. Hair buckles should not be taken into the examination room, and hair elastics may also contain metal. In the case of drug delivery pumps, the part that has to be left out is often removable. The details always depend on the exact type. Ask the staff for help or enquire in advance.
The more accurate documentation you have, the easier it will be to determine whether a metal implant could cause a problem.
MR images are taken in a strong magnetic field using URH radio waves. There is no ionising radiation. The radio waves can heat the body, but to such a small extent that it is hardly measurable, but there may be a sensation of warmth during the measurement.
The power of the radio waves is limited by international standards (similar to mobile phones) and the software of the device ensures that no measurement can be run above the upper limit.
At the Wáberer Medical Center, a General Electric Signa Voyager MR machine with a 1.5 T field range is available to perform cardiac MR examinations to 21st century standards.
