The usefulness of SPECT-CT with radioisotope-labeled leukocytes in diagnosing lead-dependent infective endocarditis.

BACKGROUND

Lead-dependent infective endocarditis (LDIE) is a life-threatening complication of permanent transvenous cardiac pacing. According to the 2015 European Society of Cardiology (ECS) guidelines, the diagnosis of LDIE is based on the modified Duke criteria (MDC), while single-photon emission computed tomography with conventional computed tomography (SPECT-CT) with radioisotope-labeled leukocytes serves as an additional tool in difficult cases. The major challenge is to differentiate between true vegetation and a thrombus.

OBJECTIVES

The aim of the study was to evaluate the usefulness of SPECT-CT with radioisotope-labeled leukocytes in diagnosing LDIE in patients with intracardiac masses (ICMs).

MATERIAL AND METHODS

The prospective registry included 40 consecutive patients admitted with an ICM on the lead and suspicion of LDIE. The confirmation or rejection of the LDIE diagnosis was made according to an algorithm based on the MDC. The cohort was divided into 2 groups: patients with definite and possible LDIE diagnoses based on the MDC (the LDIE-positive group), and patients with negative LDIE diagnoses according to the MDC (the LDIE-negative group). All patients underwent SPECT-CT with radioisotope-labeled leukocytes. The diagnostic ability of SPECT-CT was compared to the gold standard MDC.

RESULTS

The LDIE-positive group with diagnosis based on the MDC consisted of 19 patients (LDIE definite - 11; LDIE possible - 8). The LDIE diagnosis was rejected on the basis of the MDC in 21 patients. The SPECT-CT results were compared with the MDC results and showed 73.7% sensitivity, 81.0% specificity, 77.5% accuracy, 77.8% positive predictive value (PPV), 77.3% negative predictive value (NPV), likelihood ratio positive (LR+) 3.868, likelihood ratio negative (LR-) 0.325, and moderate agreement (κ = 0.548, p < 0.001). After the exclusion of 5 patients treated with antibiotics at the time of the SPECT-CT, LR+ and LRimproved to 5.250 and 0, respectively, and inter-test agreement amounted to almost perfect concordance (κ = 0.773, p < 0.001).

CONCLUSIONS

Single-photon emission computed tomography with conventional CT with radioisotopelabeled leukocytes is a useful, efficient, single-step test for diagnosing LDIE.