José Cláudio Meneguetti

SPECT dipyridamole scintigraphy for detecting coronary artery disease in patients with isolated severe aortic stenosis.

BACKGROUND The sensitivity and specificity of non-invasive methods--specifically single-photon emission computed tomography (SPECT) dipyridamole-thallium myocardial perfusion--for detecting coronary artery disease (CAD) in patients with severe aortic stenosis remains unclear. Occasionally, these patients present with atypical angina. Therefore, a CAD diagnosis must be excluded to prevent unnecessary cardiac catheterization. METHODS To determine the diagnostic value of SPECT dipyridamole-thallium imaging in this population, we compared the effectiveness of the imaging procedure with that of coronary angiography by prospectively analyzing patients who underwent both procedures. Group 1 included 59 patients who were asymptomatic or had atypical angina; group 2; 51 preoperative aged-matched patients with typical angina. SPECT acquisition was performed 15 min after 0.142 mg/kg/min of dipyridamole infusion completion, and redistribution images were performed 4 h after thallium injection. Two cut-off values of luminal diameter narrowing, >50 and >70%, defined significant CAD. RESULTS Coronary angiography with significant CAD (>50%) was present in 15 (25%) group 1 patients and in 16 (32%) group 2 patients (P=NS). The sensitivity was greater in group 2 than in group 1 (56 versus 26%; P=0.001). The specificity, positive and negative predictive value, and accuracy in the groups were similar. CAD of >70% luminal stenosis was present in 11 (19%) group 1 patients and in 12 (23%) group 2 patients (P=NS). The positive predictive value was greater in group 2 than in group 1 (75 versus 43%; P=0.001) but similar sensitivity, specificity, negative predictive value, and accuracy. The likelihood ratio for abnormal test increased in patients with CAD of >70%. CONCLUSIONS symptoms of typical angina had significant impact on test sensitivity, positive predictive value and likelihood ratio for abnormal test. Furthermore, SPECT dipyridamole-thallium imaging was a useful non-invasive method to exclude the diagnosis of significant CAD (high specificity) in asymptomatic and symptomatic patients with isolated severe aortic stenosis.

Quantification of ocular inflammation with technetium-99m glucoheptonate

Histological and morphometric evaluation of ocular inflammation is difficult, particularly when there is extensive ocular involvement with abscess formation and necrosis. A quantitative imaging procedure applicable to humans would be important clinically. To establish such a procedure, turpentine-induced ocular inflammation was obtained by subconjunctival injection in the right eye of 55 rabbits. The left eye was used as control and injected with a volume of saline equal to the volume of turpentine in the right eye. Volumes of turpentine or saline were 0.02, 0.04, 0.06, 0.2 and 0.6 ml, and the rabbits were divided into groups 1–5, according to these volumes. Imaging was performed 48 h after turpentine injection and 6 h after intravenous injection of 10 mCi of technetium-99m glucoheptonate (99mTc-GH). An inflammatory reaction index (IRI), defined as the ratio of counts of the right eye divided by counts of the left eye, was used. IRIs were proportional to the degree of inflammation and allowed the distinction of 3 subgroups: one represented by group 4, one by group 5 and one by groups 1, 2 and 3. This method of quantification of ocular inflammatory processes using 99mTc-GH is original, rapid, non-invasive, reproducible and safe, although unable to differentiate inflammatory processes caused by doses of turpentine which are very small and close to each other. It is conceivable that its application to humans will bring new insight into the ocular inflammatory process and response to therapy.

Decreased glycolytic metabolism in non-compaction cardiomyopathy by 18F-fluoro-2-deoxyglucose positron emission tomography: new insights into pathophysiological mechanisms and clinical implications

Aims The pathophysiological mechanisms of left ventricular non-compaction cardiomyopathy (LVNC) remain controversial. This study performed combined 18F-fluoro-2-deoxyglucose dynamic positron emission tomography (FDG-PET) and 99mTc-sestamibi single-photon emission computed tomography (SPECT) studies to evaluate myocardial glucose metabolism and perfusion in patients with LVNC and their clinical implications. Methods and results Thirty patients (41 ± 12 years, 53% male) with LVNC, diagnosed by cardiovascular magnetic resonance (CMR) criteria, and eight age-matched healthy controls (42 ± 12 years, 50% male) were prospectively recruited to undergo FDG-PET with measurement of the myocardial glucose uptake rate (MGU) and SPECT to investigate perfusion-metabolism patterns. Patients with LVNC had lower global MGU compared with that in controls (36.9 ± 8.8 vs. 44.6 ± 5.4 μmol/min/100 g, respectively, P = 0.02). Of 17 LV segments, MGU levels were significantly reduced in 8, and also a reduction was observed when compacted segments from LVNC were compared with the segments from control subjects (P < 0.001). Perfusion defects were also found in 15 (50%) patients (45 LV segments: 64.4% match, and 35.6% mismatch perfusion-metabolism pattern). Univariate and multivariate analyses showed that beta-blocker therapy was associated with increased MGU (beta coefficient = 10.1, P = 0.008). Moreover, a gradual increase occurred in MGU across the beta-blocker dose groups (P for trend = 0.01). Conclusion The reduction of MGU documented by FDG-PET in LVNC supports the hypothesis that a cellular metabolic pathway may play a role in the pathophysiology of LVNC. The beneficial effect of beta-blocker mediating myocardial metabolism in the clinical course of LVNC requires further investigation.