Cardiac PET Imaging

Heart Disease

Coronary Artery Disease

Coronary artery disease is caused by the accumulation of plaques within the walls of the arteries that supply blood to the myocardium, or the muscle of the heart. This narrowing of the blood vessels restricts the flow of essential nutrients that the heart muscle needs to function and continuously pump blood throughout the body. 

The heart has a unique way of providing the increased blood flow that is needed during periods of exercise or stress. A network of collapsed arteries and veins, called flow reserve, is ready to be used if needed. The heart also has the ability to develop collateral vessels to bring blood to heart tissues that may require more. When narrowing of the arteries occurs with coronary artery disease, some of these collapsed vessels open so that the heart can maintain optimal flow. A portion of the flow that should be reserved for stress or exercise is needed for resting function. In fact, blood flow to the heart tissue at rest is not decreased, so that symptoms may not be detected until the blockage is extensive, which may be when all the collapsed vessels in the area are fully utilized to address the needs of the heart at rest. Further narrowing or blockage prevents the heart muscle from getting the blood it needs, even at rest. 

Decreased or absent blood flow to the heart muscle from coronary artery disease may imply that the heart is permanently damaged and the patient may require a heart transplant. However, very often, revascularization or restoring blood flow, with bypass surgery may be all that is required to restore blood flow and function to the heart muscle. 

Proper treatment depends on understanding the level of severity of the disease and impact on the heart's function.

PET/CT Scans and Heart Disease 

PET/CT imaging provides a way to assess the severity of heart disease and measure its impact on heart function. Clinical studies show an important role for PET/CT in screening for coronary heart disease, assessing flow rates and flow reserves, and distinguishing viable from nonviable heart tissue. Two areas of clinical application have emerged:

Medicare Overview

The information below is taken from the Medicare National Coverage Determinations Manual1:

The identification of patients with partial loss of heart muscle movement or hibernating myocardium is important in selecting candidates with compromised ventricular function to determine appropriateness for revascularization. Diagnostic tests such as 18F FDG PET distinguish between dysfunctional but viable myocardial tissue and scar tissue in order to affect management decisions in patients with ischemic cardiomyopathy and left ventricular dysfunction.

Medicare covers 18F FDG PET for the determination of myocardial viability as a primary or initial diagnostic study prior to revascularization or following an inconclusive SPECT.

Limitations: In the event a patient receives a SPECT test with inconclusive results, a PET scan may be covered. However, if a patient receives an 18F FDG PET study with inconclusive results, a follow up SPECT test is not covered.

Private Payer Overview

Private insurance typically follows Medicare coverage guidelines. However, private payers can have wide variation in coverage policies, coverage criteria or procedures. Additionally, most insurance companies require pre-authorization for a PET/CT scan. It is advisable to verify local specific coverage guidelines with the payer prior to performing the scan.

Resources

• American Heart Association
• Centers for Disease Control and Prevention
• SecondsCount.org