Myocardial Flow Assessment After Heart Transplantation Using Dynamic Cadmium-Zinc-Telluride Single-Photon Emission Computed Tomography With 201 Tl and 99m Tc Tracers and Validated by 13 N-NH 3 Positron Emission Tomography

Abstract

Background: Cardiac allograft vasculopathy (CAV) is an obliterative and diffuse form of vasculopathy and is the most common cause of long-term cardiovascular mortality in heart transplant patients. This study aimed to investigate the diagnostic performance of 99m Tc and 201 Tl tracers in the assessment of CAV using cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) for myocardial blood flow (MBF) and myocardial flow reserve (MFR) quantification, which was further validated using 13 N-NH 3 positron emission tomography (PET). Methods: Thirty-eight patients with prior heart transplantation who underwent CZT SPECT and 13 N-NH 3 PET dynamic scans were included in this study. CZT SPECT with 99m Tc-sestamibi was used in the first 19 patients and 201 Tl-chloride for the remaining patients. To determine the diagnostic accuracy of angiographically defined moderate-to-severe CAV, the analysis included patients who underwent angiographic examinations within 1 year of their second scan. Results: There were no significant differences in the patient characteristics between the 201 Tl and 99m Tc tracer groups. Both 201 Tl and 99m Tc CZT SPECT-derived stress MBF and MFR values globally and in 3 coronary territories showed good correlations with 13 N-NH 3 PET. The 201 Tl and 99m Tc cohorts did not differ significantly in the correlation coefficients of CZT SPECT versus PET for MBF and MFR, except for stress MBF ( 201 Tl:0.95 versus 99m Tc:0.80, P =0.03). 201 Tl and 99m Tc CZT SPECT were satisfactory for detecting PET MFR <2.0 ( 201 Tl area under the curve, 0.92 [0.71–0.99], 99m Tc area under the curve, 0.87 [0.64–0.97]) and angiographically defined moderate-to-severe CAV, and CZT SPECT results were comparable to that of 13 N-NH 3 PET (CZT area under the curve, 0.90 [0.70–0.99], PET area under the curve, 0.86 [0.64–0.97]). Conclusions: This small study suggests that CZT SPECT using 201 Tl and 99m Tc tracers showed comparable MBF and MFR, and the results correlated well with those of 13 N-NH 3 PET. Hence, CZT SPECT with 201 Tl or 99m Tc tracers can be used to detect moderate-to-severe CAV in patients with prior heart transplantation. However, validation using larger studies is warranted.