There are many nuclear diagnostic procedures available. One of the most common indications for any type of medical work up is cardiac evaluation. Many patients present with some form of chest pain or discomfort or related symptoms. Since this is a set of indicators for potential fatal cardiac problem, the evaluation is speedy and extensive. Once heart problem is ruled out, physicians continue to evaluate less critical causes of the symptoms until a correct diagnosis is reached.

There are several cardiac imaging test studies (nuclear and non-nuclear):

Exercise Stress Test

• Simple treadmill walking test
• Indication: low risk patients with good to excellent exercise capacity correlated with their age with no prior cardiac history and no EKG changes
• Relatively low sensitivity test and specificity

Cardiolite Rest Test

• Patients are injected with Cardiolite nuclear imaging agent at rest and scanned with an hour
• Indications: active chest pain within 4 hours of onset of symptoms, patients with low cardiac event probability
• Contraindications: no active chest pain, ongoing chest pain longer than 4 hours, known abnormal previous nuclear imaging, cardiac history
• Sensitivity and specificity is good for patients with recent ischemic event with no prior cardiac history

Exercise Stress/Rest with Nuclear Imaging

• Patients receive resting dose of Cardiolite nuclear imaging agent, resting scan, than treadmill exercise test with a second, higher dose of Cardiolite during exercise, and second set of images
• Indications: higher risk patients, baseline EKG abnormalities
• Contraindications: inability to exercise up to 85% of target heart rate (220-age), left bundle branch block, active chest pain, rising troponin levels, severe anemia (non-ESRD patients), abnormal potassium levels, TIA or suspected stroke
• Sensitivity and specificity is very high
• Limitations: insufficient exercise capacity

Pharmacological Stress/Rest Test with Nuclear Imaging

Lexiscan is the most commonly used pharmacological stress agent; Adenoscan, Persantine and Dobutamine are rarely used

• Indications: inability to exercise, left bundle branch block
• Contraindications: caffeine within 12 hours, active wheezing, active chest pain, rising troponin levels, severe anemia (non-ESRD patients), abnormal potassium levels, TIA or suspected stroke
• Sensitivity and specificity is quite high

MUGA  (Multiple Gated Acquisition) Scan

• Specialized type of nuclear imaging
• Very accurate and reproducible in determining strength and size of heart beats as ejection fraction
• Used mostly for evaluation of chemotherapy effect on heart function and to evaluate congestive heart failure
• Sensitive and specific for certain indications

Cardiac Echo

• Specialized type of ultrasound imaging
• Excellent for evaluation of heart anatomy, valves
• Not sensitive or specific for coronary artery disease detection

Stress Cardiac Echo

• Baseline cardiac echo is followed by stress echo following an exercise stress test, typical on a stationary bicycle
• Rarely used

Transesophageal Cardiac Echo

• More involved form that requires sedation and extensive preparation
• The ultrasound transducer is passed into esophagus to image very close to the heart
• Not commonly used, indicated for patients with very thick chest or emphysema

Dobutamine Stress Echo

• Cardiac echo performed during stress test with dobutamine
• Heart rate and blood pressure increase in response to the medication
• Sensitive and specific for evaluating anatomy under induced stress conditions

Based on the cardiac imaging and other relevant tests, the attending physician or cardiologist can determine most appropriate course of treatment or intervention.

* PET and PET/CT (a part of Nuclear Medicine) are also beginning to contribute to diagnostic cardiac imaging. We will discuss the various tests and developments in this modality in a following post.