Optimization of a simultaneous dual-isotope 201Tl/123I-MIBG myocardial SPECT imaging protocol with a CZT camera for trigger zone assessment after myocardial infarction for routine clinical settings: Are delayed acquisition and scatter correction necessary?

BACKGROUND: Dual-isotope 201Tl/123I-MIBG SPECT can assess trigger zones (dysfunctions in the autonomic nervous system located in areas of viable myocardium) that are substrate for ventricular arrhythmias after STEMI. This study evaluated the necessity of delayed acquisition and scatter correction for dual-isotope 201Tl/123I-MIBG SPECT studies with a CZT camera to identify trigger zones after revascularization in patients with STEMI in routine clinical settings. METHODS: Sixty-nine patients were prospectively enrolled after revascularization to undergo 201Tl/123I-MIBG SPECT using a CZT camera (Discovery NM 530c, GE). The first acquisition was a single thallium study (before MIBG administration); the second and the third were early and late dual-isotope studies. We compared the scatter-uncorrected and scatter-corrected (TEW method) thallium studies with the results of magnetic resonance imaging or transthoracic echography (reference standard) to diagnose myocardial necrosis. RESULTS: Summed rest scores (SRS) were significantly higher in the delayed MIBG studies than the early MIBG studies. SRS and necrosis surface were significantly higher in the delayed thallium studies with scatter correction than without scatter correction, leading to less trigger zone diagnosis for the scatter-corrected studies. Compared with the scatter-uncorrected studies, the late thallium scatter-corrected studies provided the best diagnostic values for myocardial necrosis assessment. CONCLUSIONS: Delayed acquisitions and scatter-corrected dual-isotope 201Tl/123I-MIBG SPECT acquisitions provide an improved evaluation of trigger zones in routine clinical settings after revascularization for STEMI.

Should HIV-infected patients be screened for silent myocardial ischaemia using gated myocardial perfusion SPECT?

PURPOSE: A higher prevalence of cardiovascular risk factors (CRFs) in HIV-infected patients, together with chronic infection and treatments, has resulted in an increased risk of silent myocardial ischaemia (SMI). The objective of this study was to evaluate whether myocardial SPECT should be used for screening HIV-infected patients with no clinical symptoms of coronary artery disease. METHODS: The prevalence of SMI detected by myocardial SPECT was determined in 94 HIV-infected patients with a normal clinical cardiovascular examination in relation to anthropomorphic parameters, CRFs, inflammatory and HIV infection status, and treatment. RESULTS: Coronary artery disease was detected in nine patients (eight with ischaemia, one with myocardial infarction), corresponding to 9.6 % positivity. All but two of the scintigraphic diagnoses of ischaemia were confirmed by coronarography. Univariate analysis revealed that the overall number of CRFs and the combination of gender and age were associated with a diagnosis of SMI (p < 0.05). According to multivariate analysis, the only independent parameter significantly associated with the scintigraphic diagnosis of SMI was the combination of gender and age (p = 0.01). All the positive myocardial SPECT scans were in men older than 52 years with at least two other CRFs. In this subpopulation of 47 patients, the prevalence of SMI detected by myocardial SPECT reached 19.2 %. CONCLUSION: In male HIV-infected patients older than 52 years and with at least two other CRFs, screening for SMI using myocardial SPECT was about four times more likely to be positive than in the general population. This may motivate physicians to advise these patients to undergo more systematic screening for SMI using this technique.

Exploration of cardiac sympathetic adrenergic nerve activity in narcolepsy.

OBJECTIVE: To compare cardiac sympathetic adrenergic nerve activity in patients with narcolepsy type 1 (NT1) and controls using 123I-MIBG myocardial scintigraphy, and to determine the clinical and neurophysiological variables associated with 123I-MIBG scintigraphy results in NT1. METHODS: Fifty-six NT1 patients and 91 controls without neurological diseases underwent a cardiac scintigraphy. MIBG uptake was quantified by delayed heart/mediastinum (H/M) ratio. Clinical, neurophysiological and biological determinants of a low H/M were assessed in NT1. RESULTS: MIBG uptake did not differ between NT1 and controls in crude and adjusted associations. Five patients had low MIBG uptake (<1.42, first decile of controls), often with advanced age, cardiovascular (CV) diseases, stimulants intake, and REM sleep behavior disorder. Patients with H/M <1.62 (lowest tertile) were older, with higher BMI, microarousal index and CV comorbidities. A three-fold increase of phasic/tonic REM sleep motor activities was found in those patients, confirmed in a subanalysis of 40 drug-free patients. No association was found with CSF hypocretin levels. CONCLUSION: A direct measure of the heart adrenergic nerve activity revealed no sympathetic denervation in NT1. SIGNIFICANCE: Our results indicate normal cardiac sympathetic innervation in NT1. However, few patients with low MIBG uptake also presented CV comorbidities and REM sleep motor deregulation, potentially at high CV risk, requiring a careful follow-up.

Diagnostic performance of 18F-FDG PET-CT for large vessel involvement assessment in patients with suspected giant cell arteritis and negative temporal artery biopsy.

OBJECTIVE: The purpose of our study was to assess the diagnostic performance of 18F-FDG PET-CT for large vessel involvement in patients with suspected giant cells arteritis (GCA) and a negative temporal artery biopsy (TAB). METHODS: We conducted a retrospective study in a cohort of patients with suspected GCA and negative TAB who underwent an 18F-FDG PET-CT. Ten vascular segments were studied using a visual score and a semi-quantitative method based on SUVmax ratio with respect to liver uptake. The diagnosis of GCA was established during a mean follow-up of 42 months, based on the presence of clinical symptoms, laboratory results, and imaging data compatible with GCA, good response to corticosteroid therapy, and no differential diagnosis after a follow-up of at least 18 months. RESULTS: We included 63 patients (30 men and 33 women, aged 67 ± 12 years). 18F-FDG PET-CT showed large vessel involvement in 22 patients, 14 of whom were finally diagnosed with GCA. Forty-one patients were 18F-FDG PET-CT negative, 9 of whom were finally diagnosed with GCA. Overall, 18F-FDG uptake by large vessel yielded 61% sensitivity, 80% specificity, 64% positive predictive value, 78% negative predictive value, and 73% diagnostic accuracy. A significant number of patients were treated by corticosteroids before 18F-FDG PET-CT. However, corticosteroid therapy did not impact significantly the diagnostic performance, although there was a trend to a lower sensitivity in patients receiving corticosteroid therapy for more than 3 days. CONCLUSIONS: 18F-FDG PET-CT is a useful imaging technique to assess large vessel involvement in patients with suspected GCA and negative TAB.

Cardiac Sympathetic Activity differentiates Idiopathic and Symptomatic Rapid Eye Movement Sleep Behaviour Disorder.

The pathophysiology of rapid eye movement sleep behavior disorder (RBD) associated with narcolepsy type 1 (NT1) is still poorly understood, potentially distinct from idiopathic RBD (iRBD), but may share affected common pathways. We investigated whether MIBG cardiac uptake differs between iRBD and NT1 comorbid with RBD. Thirty-four patients with NT1-RBD and 15 patients with iRBD underwent MIBG cardiac scintigraphy. MIBG uptake was measured by calculating the early and delayed heart to mediastinum (H/M) ratios. A delayed H/M ratio lower than 1.46 was considered abnormal based on a population of 78 subjects without neurological or cardiac diseases. Patients with iRBD were older, had an older RBD onset age and higher REM sleep phasic and tonic muscular activities than NT1-RBD. Lower delayed and early H/M ratios were associated with iRBD, but not with NT1-RBD, in crude and adjusted associations. The delayed H/M ratio differed between iRBD and controls, after adjustment, but not between patients with NT1-RBD and controls. In conclusion, the MIBG cardiac uptake difference between NT1-RBD and iRBD supports the hypothesis of different processes involved in RBD pathogenesis, providing for the first time a cardiac biomarker to differentiate those disorders.

Area at risk can be assessed by iodine-123-meta-iodobenzylguanidine single-photon emission computed tomography after myocardial infarction: a prospective study.

BACKGROUND: Myocardial salvage is an important surrogate endpoint to estimate the impact of treatments in patients with ST-segment elevation myocardial infarction (STEMI). AIM: The aim of this study was to evaluate the correlation between cardiac sympathetic denervation area assessed by single-photon emission computed tomography (SPECT) using iodine-123-meta-iodobenzylguanidine (I-MIBG) and myocardial area at risk (AAR) assessed by cardiac magnetic resonance (CMR) (gold standard). PATIENTS AND METHODS: A total of 35 postprimary reperfusion STEMI patients were enrolled prospectively to undergo SPECT using I-MIBG (evaluates cardiac sympathetic denervation) and thallium-201 (evaluates myocardial necrosis), and to undergo CMR imaging using T2-weighted spin-echo turbo inversion recovery for AAR and postgadolinium T1-weighted phase sensitive inversion recovery for scar assessment. RESULTS: I-MIBG imaging showed a wider denervated area (51.1±16.0% of left ventricular area) in comparison with the necrosis area on thallium-201 imaging (16.1±14.4% of left ventricular area, P<0.0001). CMR and SPECT provided similar evaluation of the transmural necrosis (P=0.10) with a good correlation (R=0.86, P<0.0001). AAR on CMR was not different compared with the denervated area (P=0.23) and was adequately correlated (R=0.56, P=0.0002). Myocardial salvage evaluated by SPECT imaging (mismatch denervated but viable myocardium) was significantly higher than by CMR (P=0.02). CONCLUSION: In patients with STEMI, I-MIBG SPECT, assessing cardiac sympathetic denervation may precisely evaluate the AAR, providing an alternative to CMR for AAR assessment.

Is computed tomography attenuation correction more efficient than gated single photon emission computed tomography analysis in improving the diagnostic performance of myocardial perfusion imaging in patients with low prevalence of ischemic heart disease?

OBJECTIVE: The purpose of this study was to compare computed tomography (CT)-based attenuation correction (AC) using a hybrid single photon emission computed tomography (SPECT)-CT system and quantitative analysis of wall thickening using gated SPECT with regard to the diagnostic accuracy of myocardial perfusion imaging. MATERIALS AND METHODS: We prospectively included 70 patients with low prevalence of acute coronary artery disease who underwent a myocardial stress-rest SPECT study. Interpretation was based on supine nongated SPECT data with (AC) or without (NC) CT-based attenuation correction, and on gated SPECT data without attenuation correction (GNC). The scintigraphic diagnosis was obtained using standard automated quantitative analysis software and compared with a 23±14 months' clinical follow-up for 57 patients or with the results of a coronary angiography for 13 patients. RESULTS: The sensitivity, specificity, and overall accuracy were, respectively, 77, 60, and 63% for NC SPECT, 67, 81, and 79% for AC SPECT, and 69, 98, and 93% for GNC SPECT. The initial diagnosis was modified in about one-third of the cases for both AC and GNC, this rate being independent of any clinical parameter (including BMI) except sex (two to four times more artifact correction in men). CONCLUSION: Its widespread availability, cost effectiveness, safety in terms of radiation exposure, and ability to significantly improve myocardial perfusion imaging specificity and accuracy make gated SPECT a self-sufficient modality for coronary artery disease screening and follow-up, whereas CT-AC should be discussed on a case-by-case basis.