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The noninvasive assessment of resting left ventricular (LV) performance is an integral part of the evaluation of patients with known or suspected cardiac disease, having important diagnostic, therapeutic, and prognostic significance.1–11 Although scintigraphic measures of cardiac function historically included measurement of ejection fraction (EF), estimation of cardiac output, valvular regurgitant fraction, and detection of intracardiac shunts have also been successfully performed. Other than EF, these potential applications for nuclear cardiology techniques have been largely supplanted by echocardiography, cardiac computed tomography, and magnetic resonance imaging (MRI) techniques over the past two decades.
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Gated equilibrium radionuclide angiography (ERNA, often called multiple-gated acquisition [MUGA] and equilibrium radionuclide ventriculography [RNV]) were introduced nearly 30 years ago. These techniques were routinely utilized in the evaluation of patients with known or suspected LV dysfunction, postmyocardial infarction (MI), and valvular disease, and for monitoring the cardiotoxic effects of chemotherapeutic drugs. Exercise radionuclide angiography (RNA), particularly with the first-pass radionuclide angiographic (FPRNA) technique, was widely used to diagnose or evaluate known coronary artery disease (CAD),5–9 competing favorably with and often complementing planar myocardial perfusion imaging (MPI). However, since its introduction, RNA has evolved little, while other noninvasive methods, such as gated single-photon emission computed tomography (SPECT) MPI, echocardiography, and cardiac magnetic resonance, have been introduced and become increasingly sophisticated and cost effective.
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Red Blood Cell Labeling
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For FPRNA alone, Tc-99m DTPA is often used if no equilibrium images are required. For ERNA, red blood cell labeling can be performed via multiple methods. The in vitro method, usually using a commercial kit, is preferred, and offers the highest level of labeling efficiency (>97%). Blood is withdrawn from the patient, mixed into a "reaction vial" containing stannous pyrophosphate. After 5 minutes it is mixed with sodium hypochlorite to destroy extracellular stannous ion, and then with citrate buffer. After shaking lightly, 25mCi Tc-99m is added, incubated for 20 minutes and then reinjected back into the patient. The in vivo method, although simple, cheap and fast, is no longer recommended as it provides the lowest labeling efficiency (80–85%). It involves giving stannous pyrophosphate directly to the patient, followed by Tc-99m 15 to 20 minutes later (which can be given as a rapid bolus if for FPRNA). Finally, a modified in vivo/in vitro method can be used with labeling efficiency of 92% to 95%. Perfusion imaging can also be performed if desired.12–14
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First-Pass Radionuclide Angiography
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FPRNA images are usually obtained using a single- or multicrystal high-count rate gamma camera fitted with a high-sensitivity parallel hole collimator (e.g., SIM 400, Scinticor, Milwaukee, WI; or ElGems CardiaL [formerly Elscint], Haifa, Israel). Images are acquired in the anterior or the right anterior oblique (RAO) projection using 25 (±4) frames per cardiac cycle. Preliminary work suggests that FPRNA can also be performed with positron emission tomography (PET) using images acquired during a bolus ...