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

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 Tc and 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 N-NH positron emission tomography (PET).

METHODS

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