Equilibrium radionuclide angiocardiography: Its usefulness in current practice and potential future applications

Abstract

The routine and potential future applications of equilibrium radionuclide angiocardiography/multigated acquisition (MUGA) in clinical decision making are explored in this review. The non-invasive nature of the test, less operator dependence, lower radiation dose and ease of performing, even in ill patients, are important considerations in clinical cardiology practice. Two important routine uses of this modality in day-to-day clinical practice include the following: serial assessment of left ventricular ejection fraction (LVEF) in patients receiving cardiotoxic chemotherapy, and determination of accurate LVEF in patients with intractable heart failure. Other potential utilities of MUGA that could be translated into clinical practice include determination of regional LVEF, obtaining information about both right and left ventricle in suitable patients as a part of first pass angiocardiography, identification of diastolic dysfunction in patients with heart failure with preserved LVEF, and demonstration of dyssynchrony prior to cardiac resynchronisation, specifically by MUGA single photon emission tomography.The last two indications are particularly important and evolving at this point.

Keywords: Angiocardiography; Diastolic parameters; Dyssynchrony; Equilibrium radionuclide; Left ventricular ejection fraction; Multigated acquisition.

Figure 1

Normal multigated acquisition study with left ventricular ejection fraction of 66%. The phase image shows synchronous contraction across the left ventricular (LV) myocardium with narrow phase histogram width. The left and right ventricular phases are in sync with each other and out of sync with the atrial phase. The amplitude image shows maximal count variation in the lateral wall of LV myocardium suggesting maximal contraction by lateral wall and paradox image does not show any wall of LV myocardium to be in paradox. LV time activity curve is normal. EF: Ejection fraction; ROI: Region of interest; LAO: Left anterior oblique; SV: Stroke volume; Syst: Systolic; Dias: Diastolic; Avg Bkgnd: Average backgroud.

Figure 2

Multigated acquisition scan shows significantly reduced left ventricular ejection fraction of 17%. The phase image shows dyssynchronous contraction in left ventricular (LV) myocardium and there is overlap of phases both in left and right ventricular myocardium. The width of the phase histogram is more than normal suggesting intra- and inter-ventricular dyssynchrony. The image also demonstrates regional ejection fraction (EF). The paradox image does not show any region of myocardium in paradox. The left ventricular time activity curve is abnormal. ROI: Region of interest; LAO: Left anterior oblique; SV: Stroke volume; Syst: Systolic; Dias: Diastolic; Avg Bkgnd: Average backgroud..

Figure 3

Left ventricular time activity curve from the first derivative showing different phases of cardiac cycle and parameters obtained. SV: Stroke volume; PER: Peak emptying rate; TPER: TIme at peak emptying rate; PFR: Peak filling rate; t-PFR: Time to peak filling rate; TES: Time to end of systole; F: Part of SV achieved during rapid filling rate.

Figure 4

Multigated acquisition time activity curves with their first derivative. A: Pattern of normal diastolic function; B: One with abnormal diastolic function.