What is a radioisotope cardiac scan?

There are different nuclear cardiac scans, each of which uses different radiotracers.

Cardiac imaging includes:

• Myocardial perfusion imaging (MIBI scan): exercise or Persantin studies
• Multigated-acquisition scan (MUGA scan)

Why is it performed?

Nuclear cardiac scans are performed for a number of reasons.

A myocardial perfusion scan is conducted to evaluate blood flow (perfusion) to the heart muscle during exercise and rest.

The scan is performed:

• To see if there are areas of the heart with a low blood supply
• To see the location and damage of a recent heart attack
• To see the effect of blocked arteries
• To evaluate chest pain
• To back up or supplement certain findings of an ECG

How does it work?

During a cardiac perfusion or MIBI scan a small amount of radioactive tracer is injected into the bloodstream after a period of exercise or rest.

During exercise testing, echocardiogram (ECG) leads are attached to the chest, arms, and legs to monitor the heart rate. You will be asked to walk on a treadmill, or pedal on a stationary bike, slowly at first, and then the speed will increase until your heart rate reaches a certain target. Once your heart rate is at the correct rate, or if you develop chest pain during exercise, your doctor will inject the radioactive tracer intravenously. There is normally a period of about 45 minutes to an hour before imaging will commence. A camera then records images of the radioactive tracer in the heart. These cardiovascular images allow your doctor to properly assess perfusion or blood flow in the distribution of the coronary arteries.

3h after the initial stress test, a resting scan is performed. A second injection of Tc-99m MIBI is administered intravenously with the patient at rest. The second scan is performed 1h after the 2nd injection. The scan time is about 20 min.

In certain cases, if patients cannot exercise, a physiological stress test is performed where a substance called Persantin is injected slowly prior to administration of MIBI.

Preparation for a Persantin MIBI scan:

• Coffee, tea (English or breakfast tea) or any food/drinks containing caffeine (chocolates, Milo etc.) should be stopped 24h prior to the test
• If the patient is an asthmatic patient and regularly taking medication containing Theophylline, the doctor should be notified. Asthma is a relative contraindication for Persantin.