Cardiovascular disease has been the number one killer since the turn of the 19th century.  In 2002, the prevalence of coronary artery disease (CAD) was over 13 million, with more than 1 million of myocardial infarction occurred that year.  Accurate assessment of heart function and damage to heart tissue is therefore of paramount importance for physician to make accurate clinical decision.

Magnetic Resonance Imaging uses strong magnetic field to tip small particles in our bodies called “protons” to generate pictures.  This technique is non-invasive and does not expose patients to any radiation.  The quality and details of images are unmatched by any other non-invasive imaging modalities.  
 
Cardiovascular Imaging

Cardiovascular Magnetic Resonance Imaging (CMRI) has recently emerged as the “gold standard” in the assessment of heart function - how well the heart is pumping. Cardiovascular Magnetic Resonance Imaging is able to look at the heart in any views without being constraint by the patient’s physique.  The images are very reproducible, enabling physicians to follow patients over time with serial studies.

Another recent advance is the “viability / scar” sequence that allows CMRI to precisely detect any heart damage as a result of heart attack.  The sequence is performed in conjunction with the administration of “gadolinium”, a contrast agent in general is very well-tolerated by patients.  The results are very important to both the Cardiologist and the Cardiac Surgeons, especially in the planning of angioplasty versus coronary bypass surgery.

Due to the unique nature of CMRI, high contrast exists between the blood itself and the supplying vessels.  Blood vessels can be images without the use of contrast agent, however, gadolinium is commonly given to produce superb quality picture with very high resolution and to shorten the examination time.   In fact, in many institutions including ours, MR angiography has replaced traditional invasive angiography in the image of blood supply to the head, limbs as well as the aorta.

Cardiovascular Magnetic Resonance Imaging can also use to assess the significance of “narrowing” of the coronary arteries by performing Stress CMRI.  The resolution is better than the widely used modality (Nuclear SPECT).  The information allows the Cardiologist / Cardiac Surgeon to decide how the narrowing is best managed.

As CMRI does not involve any radiation, it is especially suited in the long-term follow-up of patients and disease processes.

1. Coronary Artery Disease
2. • Cardiac function
   • Myocardial viability – the amount of damaged heart tissue
   • Adenosine stress perfusion study
3. Cardiomyopathy
4. • To evaluate various forms of non-ischaemic cardiomyopathy, e.g. hypertrophic cardiomyopathy, isolated left ventricular non-compaction, arrhythmogenic right ventricular dysplasia / cardiomyopathy and dilated cardiomyopathy
5. Congenital Heart Disease
6. Valvular Heart Disease
7. Aortic
8. • Thoraco-abdominal aortic disease – for detection of aneurysm, dissection
   • As part of the workup for Endovascular Aneurysm Repair (link)
9. Peripheral vascular disease
10. • Evaluation of peripheral vessels (lower limbs) in patients with claudication
    • Assessment of renal artery stenosis as a cause of high blood pressure
    • Assessment of mesenteric vessels as a cause of abdominal pain
11. Pulmonary vein mapping before atrial fibrillation ablation
12. Cardiac Mass
13. Assessment of iron content of heart by a special T2* sequence
14. Pericardial disease
15. • Pericardial effusion
    • Pericardial thickness and constrictive pericarditis
    • Assessment of mesenteric vessels as a cause of abdominal pain
16. Anomalous Coronary Artery detection 
    

Patient preparation

Patient preparation is limited.  Certain type of examination will require the placement of an intravenous line in the back of the hand so that gadolinium can be given.  Patient will fill in a safety questionnaire before the examination.  ECG leads will be attached to the chest in most of the CMRI examinations.  The patient will lie on the examination bed inside the “magnet tube” The patient is in continuous communication with the physician / technologist all the time and may require to follow breath-holding instructions during certain parts of the examinations.

Some patients may feel claustrophobic inside the “magnet tube”.  Light sedation can be given by the physician to assist the patient to go through the examination.

The duration of the examination depends on the type of examination, e.g. 35 minutes for a “viability” study, and 50 minutes for a stress perfusion study.

Some patients may feel a warm / tingling sensation under the area of examination.   Furthermore, a warm sensation can be felt at the site of IV line when the gadolinium is injected.  The above findings are very common; however, the examiner should be informed if they persist.

Risk and Limitation of Study

There are certain limitations to CMRI.  The quality of the heart images will be affected if there are significant irregular heart beats or patients cannot maintain consistent breath-holds.  Patients with certain metallic implants will be allowed in the MR scanner and they will be screened by the safety questionnaire as well as the technologist.  CVMRI will usually not be performed in patients who are pregnant.

The Food and Drug Administration has recently issued a warning regarding the use of Gadolinium and the development of Nephrogenic Systemic Fibrosis (NSF) (link) in patients with significant renal disease.  Your physician should obtain a blood test for kidney function before your test if you are over 50 years old or have diabetes or known history of renal disease to confirm that you have satisfactory kidney function.