Stress MPI scan for heart | Super Sahyog Nuclear Imaging

Downloads

For most essential points to best prepare for the procedure, please download the patient information brochure (PDF).
For a more elaborate explanation of the procedure and related points, please continue to read ahead.

Brief introduction

Principle

This write up is best read after going through general introduction to MPI explaining functioning of the heart, its blood supply, and principles of this procedure.

Under physical stress, myocardial territories served by normal coronary arteries show markedly increased perfusion, whereas those served by stenosed arteries show no improvement or much lesser improvement. This disparity in perfusion makes it easier to identify ischaemic territories under stress.

Physical stress is created using a treadmill. ECG electrodes are connected on the chest and limbs. The patient walks / jogs on the treadmill. The speed and inclination of the treadmill are governed by 'modified Bruce protocol' with 3 minute-stages of increasing speed and inclination. Aim of the exercise is to cause maximum possible increase in blood flow to the heart muscles, indicators of which include heart rate (HR) and systolic blood pressure (SBP). Most patients reach these targets during third or fourth stages (within 6 to 12 minutes). MIBI or tetrofosmin are injected during maximal stress, and the treadmill is kept running for at least a minute.

Injecting MIBI or tetrofosmin is avoided if the test targets (of HR and SBP) are not met. The stress test may also have to be prematurely terminated in cases of excessive exhaustion, troubling symptoms, excessive excursions in blood pressure, and certain types of ECG changes.

Indications (conditions in which advised)

Assessing need for CAG in those with intermediate test results on treadmill test.
Assessing need for CAG in those with renal failure.
Baseline assessment before medical therapy and/or revascularization (PCI or CABG surgery).
Assessing improvement in myocardial perfusion following treatment for CAD and/or IHD.
Evaluating viability of at-risk myocardium (though cardiac FDG PET is more reliable in this regard).
Determining prognosis after MI.
Preoperative stratification of risk for adverse cardiovascular events during non-cardiac surgery

Considerations / steps before procedure

Prior appointment is a must.
Patient must not be pregnant.
If breast feeding, please inform the staff for further directions.
Some drugs that alter heart rate and blood pressure (beta blockers, calcium channel blockers and nitrates) may have to be stopped few days before the procedure.
Caffeine-containing beverages and food products (i.e., tea, coffee, chocolate and certain 'cold drinks') must be avoided for 12 hours before the procedure.
Class of drugs called methylxanthines (most commonly used in asthma) must be stopped 24 hours before the procedure.
Male patients must shave off chest hair before reporting.
Patients must bring along a pair of running shoes they are used to.
Clothing suitable for brisk walking and running should be brought along.
Please bring along suitable fatty meal (e.g., bread and butter) for the procedure.
4 hours’ fasting before scan.
Please let the staff know at the time of appointment if the patient is unable to lie still for ~30 min, has breathing difficulty, or might need special medical attention for the duration of visit.
Have at least 1/2 litre water within an hour before reporting for the scan. There is no need to hold urine.
There is no need to hold urine before reporting for the procedure.
Do not bring expensive jewellery or accessories along with you for the scan.
Proof of doctor's request is necessary for starting the procedure.
The patient must be accompanied by a responsible carer.

What to expect as part of procedure?

Important steps

Rest study
1. Patient registration and consent.
2. Handing over medical documents to the staff.
3. Intravenous (IV) access is established (in form of cannula).
4. Radiopharmaceutical (RP) - Sestamibi / tetrofosmin is injected through the IV cannula.
5. Waiting time of ~75 min (± 15 min) to allow sufficient time for RP to be taken up and eliminated by all organs. Pass urine just before the scan, and also before that (if needed).
6. Scanning process starts wherein, the patient lies on their back on the scanner table. A pair of detectors rotates around the patient's chest region, and the entire procedure lasts for ~30 minutes.
7. The acquired images are reviewed to ascertain satisfactory scan quality.
8. The scan may have to be repeated especially if there is unacceptable patient movement.
Stress study
1. RP is injected during the treadmill test (as described above).
2. Waiting time of ~45 min (± 15 min) to allow sufficient time for RP to be taken up and eliminated by all organs. Pass urine just before the scan, and also before that (if needed).
3. Scanning process is similar to the resting study.
4. The acquired images are reviewed to ascertain satisfactory scan quality.
5. The scan may have to be repeated especially if there is unacceptable patient movement.

Rest and stress studies can be performed on the same day or on separate days. Splitting study between 2 separate days could result in slightly better image quality and reduction in RP dose, but this could prove inconvenient to some patients.

Discomfort / risks during procedure

Pain during injections or IV cannula insertion.
There is risk of extravasation at the time of injections or IV cannula insertion. [Extravasation means that blood leaks through the walls of vein punctured by cannula’s needle].
There is very small risk (1 in 10,000) of MI, i.e., 'heart attack' while exercising on treadmill.

Time taken for the entire patient visit

Typical: 5 hours (either on same day or split between 2 days).
Be prepared for: 7 hours (either on same day or split between 2 days).

What to expect after procedure?

Precautions / special care

Maintain at least 1 metre-distance from pregnant ladies and children (below 10 years) for at least 5 hours after the scan.
Drink plenty of water throughout the day (3 to 4 litres).
Pass urine as frequently as possible throughout the day.

Discomfort / risks

Exhaustion and/or muscle pain because of treadmill exercise.
There are no other remarkable expected risks or side effects.

Time taken for report / summary generation

Typical (for self-paying patients): 12 hours.
Be prepared for: 24 hours.

Additional reading

For additional information, please visit the following links.

Stress MPI scan

Table of contents