Cardiac nuclear imaging
The above tests differ in terms of their diagnostic accuracy, cost, availability, and impact on downstream testing, potential to harm, and other relative advantages and disadvantages. There is therefore significant benefit in conducting a comprehensive evaluation of the evidence on the comparative clinical effectiveness and comparative value of nuclear myocardial perfusion tests.
Primary criteria ranking
- Safety = Medium
- Efficacy = Medium
- Cost = High
Coronary artery disease (CAD) is among the most common chronic conditions in the U.S., affecting over 16 million adults. CAD is estimated to cause over 1 million acute coronary events and over 400,000 deaths in this country each year.
Due to its prevalence, and because several options (e.g., surgery, medication) exist to reduce CAD-related morbidity and mortality, accurate diagnosis of CAD is critical. Currently the definitive standard for diagnosis is invasive coronary angiography (ICA). There are risks associated with ICA, however, such as infection, artery trauma, and heart arrhythmias. For this reason non-invasive diagnostic methods have been explored to document the presence of CAD; a growing number of such tests have been developed to identify CAD lesions significant enough to affect the flow of blood to the heart (i.e., myocardial perfusion). These functional tests are typically performed under exercise- or drug-induced stress to determine whether blood flow deteriorates when the stressor is introduced.
The most common tests of cardiac function include the stress-electrocardiogram (EKG or ECG), or treadmill test, which measures cardiac activity via electrical signals, and the stress-echocardiogram (ECHO), which uses ultrasound to measure myocardial perfusion using 2-dimensional imagery. Stress-EKG has fallen out of favor for use in patients at higher risk of CAD, however, as it has relatively low sensitivity and specificity for CAD, while stress-ECHO has been found to be less sensitive for detecting single-vessel vs. multi-vessel disease and may produce suboptimal imagery in obese patients, those with chronic respiratory conditions, and patients with chest deformities or pre-existing myocardial damage.
To address such concerns, "nuclear stress tests" have been developed to provide perfusion data in a broader spectrum of patients. The most longstanding of these is single photon emission computed tomography (SPECT), which uses a radioactive tracer and gamma camera to obtain images. Positron emission tomography (PET) scanners are also used with a radiotracer, and are felt by some to provide better image resolution in heavier patients and those with dense breast tissue. Additionally, combination modalities, originally developed for cancer detection and imaging, have also been applied to cardiac imaging to provide both perfusion and anatomic data (e.g., PET/CT, SPECT/CT) and/or to compare perfusion measurement methods (e.g., PET/MRI).
- Draft key questions Published: March 21, 2013
- Public comment period: March 21 – April 8, 2012
- Draft report published: June 24, 2013
- Public comment period: June 24 - July 22, 2013
- Final report published: August 19, 2013
- HTCC public meeting: September 20, 2013