Myocardial Flow Assessment After Heart Transplantation Using Dynamic Cadmium-Zinc-Telluride Single-Photon Emission Computed Tomography With 201Tl and 99mTc Tracers and Validated by 13N-NH3 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 ^99mTc and ²⁰¹Tl 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-NH₃ positron emission tomography (PET).

Methods: Thirty-eight patients with prior heart transplantation who underwent CZT SPECT and ¹³ N-NH₃ PET dynamic scans were included in this study. CZT SPECT with ^99mTc-sestamibi was used in the first 19 patients and ²⁰¹Tl-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 ²⁰¹Tl and ^99mTc tracer groups. Both ²⁰¹Tl and ^99mTc CZT SPECT-derived stress MBF and MFR values globally and in 3 coronary territories showed good correlations with ¹³ N-NH₃ PET. The ²⁰¹Tl and ^99mTc cohorts did not differ significantly in the correlation coefficients of CZT SPECT versus PET for MBF and MFR, except for stress MBF (²⁰¹Tl:0.95 versus ^99mTc:0.80, P=0.03). ²⁰¹Tl and ^99mTc CZT SPECT were satisfactory for detecting PET MFR <2.0 (²⁰¹Tl area under the curve, 0.92 [0.71-0.99], ^99mTc 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-NH₃ 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 ²⁰¹Tl and ^99mTc tracers showed comparable MBF and MFR, and the results correlated well with those of ¹³ N-NH₃ PET. Hence, CZT SPECT with ²⁰¹Tl or ^99mTc tracers can be used to detect moderate-to-severe CAV in patients with prior heart transplantation. However, validation using larger studies is warranted.

Keywords: heart transplantation; positron emission tomography; technetium Tc 99m Sestamibi; thallium-201; tomography, emission-computed, single-photon.