Heart

With the patient fasting prior to injection, myocardial metabolism shifts from glucose utilization to fatty acids. As such, myocardial uptake of FDG should me minimal. 

Unfortunately, as the heart apparently has not read the rules on its metabolism, myocardial uptake is often extremely intense and its pattern of uptake quite variable.

While uptake in the heart almost always involves the myocardium of the left ventricle, uptake within the right ventricle is also frequently seen. Normal atrial and papillary muscle uptake is an occasional finding. 

Given the great variability of cardiac uptake, be very wary of considering any cardiac uptake “pathologic” unless accompanied by a corresponding CT abnormality.

For suspected para-cardiac lesions, some radiologists advocate increasing the pre-scan fasting period to 18-hours (instead of the normal 5-hour fast). This prolonged fasting period decreases the likelihood of cardiac activity obscuring an adjacent lesion.

Lipomatous hypertrophy of the inter-atrial septum is discussed in detail, here.