radionuclide ventriculography; cardiac blood pool imaging (RVG, MUGA)

Introduction

A test of ventricular structure & function in which images are produced through external detection of an intravascular radioactive tracer.

Indications

• assessement of LV systolic dysfunction
  • useful for serial evaluation of LVEF with cardiotoxic drugs

Contraindications

• patients with irregular R-R intervals, such as those with atrial fibrillation are not well suited for this procedure

Advantages

• quantitiative measurements of LV ejection fraction
• there is good signal to noise ratio in large, poorly contractile ventricles, thus MUGA has advantages over echocardiogram in patients with low ejection fractions as well as in patients with poor echocardiographic windows

Disadvantages

• less accurate with atrial fibrillation
• radiation exposure
• no data on other cardiac structures

Procedure

• erythrocytes are labeled with technetium
• a gamma counter is placed in the anteroposterior, left anterior oblique & lateral positions
• images are acquired over multiple cardiac cycles
• the procedure uses electrocardiographic gating in which the aperature of the gamma counter is open for fractions of the cardiac cycle.
• left ventricular ejection fraction is calculated from the number of photons present in the left ventricle at end-diastole at end-systole

More general terms

• scintigraphy (radionuclide test)