Introduction Myocardial perfusion scintigraphy (MPS) is one of the most commonly performed non-invasive imaging procedures for the diagnosis of Coronary Artery Disease (CAD). Two large trials evaluating over 21,000 patients with a normal SPECT study have demonstrated the safety of stress-only imaging as compared to traditional stress/rest imaging. Comparably low all-cause and cardiac mortality rates were observed with both imaging protocols. This was true irrespective of patient age, gender, cardiac risk factor profile, or stressor employed with SPECT. These results are consistent with earlier studies evaluating patient outcome following normal stress-only imaging. The best use of a stress-only imaging strategy is likely to be in the selected low or intermediate risk population, which forms the referral basis for myocardial perfusion imaging. In this study, we describe the introduction of stress only MPS in comparison to traditional stress/rest MPS.
Old Pathway The traditional stress/rest MPS pathway requires two imaging sessions either the same day or on two separate days according to the patient’s Body Mass Index (BMI). For a 1 day protocol typically the injected activity is split in a 1:3 ratio between the first and second injections. For BMI <30, a total of 1125 MBq is administered. For BMI 30–35, a total of 1475 MBq is administered. For BMI>35, a total of 2000 MBq is administered 1:1. If the BMI is not provided by the requesting clinician then a letter is sent to the patient asking their height and weight.
New Pathway From September 2014 through December 2014, we introduced selective stress only imaging. A single high dose MIBI stress dose of of 800 MBq, was authorised for all patients, regardless of BMI. After stress imaging, a decision was made regarding the necessity of rest imaging.
Results Patients were referred from 10 hospitals. 407 patients were scanned. 55% were male and 45% female. Their average age was 66 years (+/-12.9). Their average BMI was 29.4 kg/m2 (+/-6.4).
Of the total, 35% percent were normal at stress imaging and did not have rest imaging. Of the 65% who were abnormal, 60% of the combined rest/stress scans were interpreted as abnormal. As a result of this, the average time from request to appointment date for the stress scan reduced from 27 to 14 days.
The average time between stress scan and rest scan was 2.5 (range: 1–21 days). The average report turn around time from request to report for MPS was 5 days, but 97% of normal stress only scans were reported the same day. Furthermore, the administered radiation dose was lower for 67% of all patients.
In additional to scanning parameters being assessed, patients preferences were also assessed via a questionnaire. 49% expressed a preference for the test to be split across 2 days. 7% said either 1 day or 2 days. 20% of patients had to take a day off work to attend the hospital.
Conclusion Stress only MPS reduces radiation exposure, increases efficiency and thereby reduces cost.
- perfusion scintigraphy
- nuclear imaging
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