How does the ejection fraction (EF) calculated during the sestamibi imaging of a cardiac stress test correlate with an EF measured with a two-dimensional cardiogram? — Patricia Gable, FNP-BC, Cadillac, Mich.

The EF is calculated by the computer assessment of gated images obtained during a sestamibi imaging test. The short axis gated images obtain data from the apex to the base; the horizontal gated images obtain data from the posterior to anterior; and the vertical gated images obtain data septal to lateral. The equipment determines how many slices (more slices mean better data). The ECG is then correlated to the gated images before the volume at end diastole and systole is finally calculated.

This all sounds impressive, but the EF from nuclear stress testing is often erroneous if the heart size is small (as in many women) or large with cardiomyopathies, or there are arrhythmias during the scanning process. The EF obtained by echocardiography is directly dependent on the images obtained by the sonographer and the experience of the reader. It is quite reliable with good images and a talented reader. The best EF is by either multigated acquisition (MUGA) scan or ventriculography during left-heart catheterization. — Maria Kidner, DNP, FNP-C (155-8)