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Pharmacology / Nuclear Medicine

Nuclear imaging provides powerful tools for managing heart disease

04/10/2009

Treadmill-Nuclear imagingNuclear imaging techniques are being used to detect coronary artery disease in selected patients with significantly greater accuracy than traditional electrocardiogram (EKG) testing. The technique, known as myocardial perfusion imaging, is used to produce images of the patient’s heart when it is under stress and when at rest. Areas affected by coronary artery disease will show normal perfusion at rest but during stress, when demand for oxygen-rich blood increases, imaging will reveal inadequate perfusion.

Patients with an intermediate to high likelihood of coronary artery disease are good candidates for myocardial perfusion imaging. This includes those showing symptoms of coronary artery disease, such as angina, and those with a combination of risk factors such as hyperlipidemia, high blood pressure, family history, history of smoking, etc.

Cardiac imaging is also used in patients with multi-vessel disease — those who have more than one vessel contributing to the disease process — to help determine which vessel is causing the patient’s symptoms.

About the imaging study

Myocardial perfusion imaging is most often performed using SPECT (single proton emission computed tomography). First, a radioactive tracer is injected at rest and allowed to distribute through the patient’s heart. The patient then exercises on a treadmill to put stress on the heart. If the patient is not able to undergo the physical stress test, a pharmacological agent is used to induce stress on the heart. From the stress and the rest images it can be determined whether the blood flow to the heart is normal or abnormal.

If SPECT imaging does not produce definitive results, PET (positron emission tomography) can be used to produce higher resolution images.

Hibernating myocardium

Some heart failure patients suffer reduced heart function when myocardial segments cease functioning due to an inadequate supply of oxygenated blood. Though the tissue is still alive, it no longer contributes to the heart’s pumping action. Known as hibernating myocardium, the condition is reversible — unlike myocardial infarction — if the affected area can be revascularized. Nuclear imaging can help physicians distinguish between infarcted and hibernating myocardial tissue.

The diagnosis is highly significant because hibernating myocardium can be successfully treated with coronary bypass surgery, whereas heart failure due to infarction can require heart transplantation. Patients diagnosed with hibernating myocardium can be spared the additional trauma and need for lifelong immunosuppression associated with cardiac transplantation while avoiding additional pressure on the donor organ supply.

When a patient is found to have inadequate perfusion both during stress and while at rest, PET/CT is used with a radio-labeled glucose tracer. If the tissue in question is consuming glucose, then it is merely dormant and not dead and can be treated with bypass surgery.

Accurate diagnosis of coronary artery disease

“Myocardial perfusion imaging with SPECT is the best non-invasive technique to image cardiac patients,” asserts Johannes Czernin, M.D., professor of molecular and medical pharmacology and director of nuclear medicine at UCLA. “It is highly accurate and gives very reliable results.”

Coronary artery disease is the leading cause of death in the United States for both men and women. According to Dr. Czernin, treadmill stress testing with EKG has an accuracy of about 65 percent in diagnosing coronary artery disease; nuclear imaging can improve this rate to 85 to 90 percent.

UCLA’s nuclear cardiology program is a collaboration between cardiology and nuclear medicine with services available at Santa Monica-UCLA Medical Center and Orthopaedic Hospital and at Ronald Reagan UCLA Medical Center in Westwood.

Participating Physicians

Martin Allen-Auerbach, M.D.
Assistant Clinical Professor,
Molecular and Medical Pharmacology

Johannes Czernin, M.D.
Professor,
Molecular and Medical Pharmacology

Robb MacLellan, MD
Associate Professor, Cardiology

Heinrich Schelbert, M.D., Ph.D.
Professor, Molecular and Medical Pharmacology

Christiaan Schiepers, M.D., Ph.D.
Clinical Professor,
Molecular and Medical Pharmacology

Daniel Silverman, M.D., Ph.D.
Associate Clinical Professor,
Molecular and Medical Pharmacology

Ramin Tabibiazar, MD
Assistant Professor, Cardiology

Contact Information

(310) 794-1005 Appointment scheduling
(310) 267-0227 Fax
www.nuc.uclahealth.org





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