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Nuclear Imaging

For evaluation of myocardial ischemia in patients with known or suspected coronary artery disease (CAD), nuclear myocardial perfusion imaging (MPI) is useful in patients with an intermediate likelihood of significant CAD based on age, gender, symptoms, risk factors, and results of stress electrocardiogram (ECG) testing (if available).¹

Stress MPI can provide important physiologic information about the extent, severity, and location of perfusion defects.¹ For intermediate-risk patients, testing with MPI using single-photon emission computed tomography (SPECT) can help identify patients at lower risk versus higher risk for cardiac events.^2-4 For patients at high risk, who may have a higher prevalence of CAD, SPECT results can help identify those who may benefit from invasive cardiac procedures.^2,5

Imaging at Stress and Rest

MPI depicts the distribution of blood flow in the myocardium by assessing the uptake of an intravenously administered radionuclide.⁶ Abnormal uptake of the radionuclide results in a “cold spot” on the image,⁷ indentifying areas of relatively reduced myocardial blood flow associated with ischemia or scar.⁶

The relative regional perfusion distribution can be assessed at rest, during cardiovascular stress, or both. The differentiation of ischemic myocardium is made by comparing images obtained at rest with those obtained at the peak of maximal exercise or during pharmacologic stress.⁶

STRESS		REST

Images courtesy of Kim Allan Williams, MD.

References
1. Klocke FJ, et al. ACC/AHA/ASNC Guidelines. 2003. http://www.acc.org/qualityandscience/clinical/guidelines/radio/index.pdf.
2. Berman DS, et al. Risk stratification and patient management. In: Dilsizian V, et al. Atlas of Nuclear Cardiology. 2nd ed. 2006:143-159.
3. Hachamovich R, et al. Circulation. 1998;97:535-543.
4. Metz LD, et al. J Am Coll Cardiol. 2007;49:227-237.
5. Shaw LJ, et al. J Nucl Cardiol. 2004;11:171-185.
6. Strauss, et al. Procedure guideline for myocardial perfusion imaging. 2008. http://interactive.snm.org/docs/155.pdf.
7. McKillop JH. West J Med. 1980;133:26-43.

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Lexiscan (regadenoson) injection is a pharmacologic stress agent indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress.

IMPORTANT SAFETY INFORMATION

Do not administer Lexiscan to patients with second- or third-degree AV block or sinus node dysfunction unless these patients have a functioning artificial pacemaker.

Fatal cardiac arrest, life-threatening ventricular arrhythmias, and myocardial infarction may result from the ischemia induced by pharmacologic stress agents. Hypersensitivity including anaphylaxis, angioedema, cardiac or respiratory arrest, respiratory distress, decreased oxygen saturation, hypotension, throat tightness, urticaria and rashes have occurred. Resuscitation equipment and trained staff should be immediately available before administering Lexiscan.

Adenosine receptor agonists, including Lexiscan, can depress the SA and AV nodes and may cause first-, second-, or third-degree AV block, or sinus bradycardia requiring intervention. In postmarketing experience, heart block (including third degree), and asystole within minutes of Lexiscan administration have occurred.

Adenosine receptor agonists, including Lexiscan, induce arterial vasodilation and hypotension. The risk of serious hypotension may be higher in patients with autonomic dysfunction, hypovolemia, left main coronary artery stenosis, stenotic valvular heart disease, pericarditis or pericardial effusions, or stenotic carotid artery disease with cerebrovascular insufficiency. In postmarketing experience, transient ischemic attack, seizures and syncope have been observed.

Adenosine receptor agonists, including Lexiscan, may result in clinically significant increases in blood pressure in some patients. In postmarketing experience, cases of potentially clinically significant hypertension have been reported, particularly in patients with underlying hypertension and when low-level exercise was included in the MPI.

Adenosine receptor agonists, including Lexiscan, may cause dyspnea, bronchoconstriction and respiratory compromise. Appropriate bronchodilator therapy and resuscitative measures should be available prior to Lexiscan administration.

The most common adverse reactions (≥5%) to Lexiscan are dyspnea, headache, flushing, chest discomfort, angina pectoris or ST-segment depression, dizziness, chest pain, nausea, abdominal discomfort, dysgeusia, and feeling hot. Most adverse reactions began soon after dosing, and generally resolved within approximately 15 minutes, except for headache, which resolved in most patients within 30 minutes. Aminophylline was used as a reversal agent in 3% of patients.

In postmarketing experience, QTc prolongation, tremor, abdominal pain in association with nausea, vomiting, or myalgias, and diarrhea, fecal incontinence, wheezing and musculoskeletal pain have occurred.

Intravenous Adenoscan is indicated as an adjunct to thallium-201 myocardial perfusion scintigraphy in patients unable to exercise adequately.

IMPORTANT SAFETY INFORMATION

Adenoscan is contraindicated in patients with second- or third-degree AV block, unless these patients have a functioning artificial pacemaker, sinus node disease, and known or suspected bronchoconstrictive or bronchospastic lung disease.

Fatal cardiac arrest, sustained ventricular tachycardia (requiring resuscitation), and nonfatal myocardial infarction have been reported coincident with Adenoscan infusion. Patients with unstable angina may be at greater risk. Appropriate resuscitative measures should be available.

Adenoscan is a potent peripheral vasodilator and can cause significant hypotension. The risk of hypotension may be higher in patients with cardiac or cerebrovascular insufficiency.

Adenoscan exerts a direct depressant effect on the SA and AV nodes and has the potential to cause first-, second- or third-degree AV block, or sinus bradycardia.

Increases in systolic and diastolic pressure have been observed.

Adenosine receptor agonists, including Adenoscan, may cause bronchoconstriction and respiratory compromise.

Atrial fibrillation has been reported in patients with Adenoscan infusion and may last from a few seconds to hours, however, patients spontaneously converted to normal sinus rhythm.

Most common adverse reactions (≥5%) to Adenoscan are flushing, chest discomfort, dyspnea, headache, discomfort of the throat, neck, or jaw, gastrointestinal discomfort, and lightheadedness/dizziness. Side effects with Adenoscan usually resolve quickly when the infusion is discontinued, although delayed or persistent effects have been observed.

Lexiscan is a registered trademark of Astellas US LLC. Other trademarks listed belong to their respective owners.
Lexiscan was developed in collaboration with Gilead Palo Alto, Inc. (formerly CV Therapeutics, Inc.).