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Objective: Increased myocardial glucose metabolism occurs with the onset of myocardial ischemia and may persist even after the restoration of blood flow, termed as 'ischemic memory'. Previous studies have demonstrated that 18F-fluorodeoxyglucose (18F-FDG) is a sensitive marker of myocardial ischemia and may have potential utility in diagnosing unstable angina (UA). This study aimed to explore the value of F-FDG PET/CT in diagnosing UA., Patients and Methods: Thirty-four patients (17 male patients; mean age, 59 ± 6 years) with suspected UA were prospectively recruited. Resting myocardial F-FDG PET/CT imaging was performed 21 ± 9 h (2-46 h) after the latest onset of angina pectoris. Resting or exercise myocardial perfusion imaging (MPI) and coronary angiography were performed. 'Focal' or 'focal on diffuse' myocardial F-FDG uptake was defined as abnormal, whereas other patterns of myocardial uptake, including 'focal' uptake on the basal segments, were considered as normal. The final diagnosis of UA was based on a comprehensive analysis of ECG, MPI, and coronary angiography., Results: Of the 21 patients with a final diagnosis of UA, 18 had increased 18F-FDG uptake (sensitivity 85.7%), whereas, of the 13 patients without UA, only one had abnormal 18F-FDG uptake (specificity 92.3%). The sensitivity of resting 18F-FDG imaging was higher than that of resting MPI (85.7 vs. 52.4%, P=0.016). Moreover, six UA patients with only exercise-induced ischemia showed abnormal F-FDG uptake at rest., Conclusion: This pilot study demonstrated that resting 18F-FDG PET/CT imaging is an accurate and sensitive technique for the identification of UA.

The effects of left bundle branch block (LBBB) on left ventricular myocardial metabolism have not been well investigated. This study evaluated these effects in patients with coronary artery disease (CAD).Sixty-five CAD patients with complete LBBB (mean age, 61.8 ± 9.7 years) and 65 without LBBB (mean age, 59.9 ± 8.4 years) underwent single photon emission computed tomography, positron emission tomography, and contrast coronary angiography. The relationship between myocardial perfusion and metabolism and reverse mismatch score, and that between QRS length and reverse mismatch score and wall motion score were evaluated.The incidence of left ventricular septum and anterior wall reverse mismatching between the two groups was significantly different (P < 0.001 and P = 0.002, respectively). The incidences of normal myocardial perfusion and metabolism in the left ventricular lateral and inferior walls were also significantly different between the two groups (P < 0.001 and P < 0.001, respectively). The incidence of septal reverse mismatching in patients with mild to moderate perfusion was significantly higher among those with LBBB than among those without LBBB (P < 0.001). In CAD patients with LBBB, septal reverse mismatching was significantly more common among those with mild to moderate perfusion than among those with severe perfusion defects (P = 0.002). The correlation between the septal reverse mismatch score and QRS length was significant (P = 0.026).In patients with CAD and LBBB, septal and anterior reverse mismatching of myocardial perfusion and metabolism was frequently present; the septal reverse mismatch score negatively correlated with the QRS interval.

Objectives: This study was designed to evaluate the biodistribution and blood clearance characteristics of 99mTcN-15C5 and its potential as a myocardial perfusion radiotracer., Methods: Five normal mongrel dogs were injected with 99mTcN-15C5 intravenously. Blood samples were collected at 0.5, 1, 2, 3, 4, 5, 10, 15, and 30 min postinjection (p.i.). Anterior planar images were acquired at 5, 15, 30, 60, 90, and 120 min p.i. Regions of interest (ROIs) were drawn around heart, liver, and lungs. The raw activity in each ROI was expressed as counts/pixel/min. Heart/liver and heart/lung ratios were calculated by dividing the mean counts in heart ROI by the mean counts in liver and lung ROI, respectively. For comparison, 99mTc-sestamibi was also evaluated in the same five dogs. In dogs with coronary stenoses, single photon emission computed tomography images were acquired at 30, 60, and 120 min after administration of 99mTcN-15C5 with/without adenosine., Results: 99mTcN-15C5 and 99mTc-sestamibi had very similar blood clearance characteristics during the first 30 min p.i. The heart/liver ratio of 99mTcN-15C5 increased from 0.48+/-0.05 at 5 min p.i. to 1.85+/-0.11 at 120 min p.i., whereas the heart/liver ratio of 99mTc-sestamibi was improved only slightly from 0.45+/-0.04 at 5 min p.i. to 0.74+/-0.15 at 120 min p.i. SPECT imaging studies in canines with coronary stenoses indicated that good visualization of the perfusion defect could be achieved at 30 min after administration of 99mTcN-15C5 with the adenosine stress., Conclusion: The combination of high heart uptake and rapid liver clearance makes 99mTcN-15C5 a promising new radiotracer for myocardial perfusion imaging.

Background and Aim: Previous studies have documented the prognostic value of normal exercise Tl myocardial perfusion imaging in patients with angiographic coronary artery disease (CAD). However, data on exercise Tc-sestamibi myocardial single photon emission computed tomography (SPECT) are scant. Accordingly, the purpose of this study was to investigate the prognostic value of normal exercise Tc-sestamibi SPECT in patients with angiographic CAD., Methods: We retrospectively investigated 90 consecutive patients who had a normal exercise Tc-sestamibi myocardial SPECT but angiographic CAD. A group of 69 consecutive patients with both normal exercise Tc-sestamibi myocardial SPECT and coronary arteries were included as control., Results: During a mean follow-up of 50+/-19 months, a total of three hard cardiac events (non-fatal myocardial infarction) and seven soft cardiac events (late revascularization) were observed. The annual hard cardiac event rate between the two groups was not significantly different (0.6% vs. 0.3%, chi=0.47, P=NS), nevertheless the annual soft cardiac event rate was higher in patients with angiographic CAD (1.9% vs. 0, chi=5.74, P=0.02). Moreover, the annual hard cardiac events rate in patients with angiographic CAD who were treated medically was also not significantly different from that of the control group (0.8% vs. 0.3%, chi=0.77, P=NS). Among patients with angiographic CAD, the annual hard cardiac event rate was not statistically different between those treated medically and those who underwent revascularization (0.8% vs. 0, chi=0.53, P=NS)., Conclusions: Our data demonstrate that normal exercise Tc-sestamibi myocardial SPECT despite angiographic CAD suggests a low rate of cardiac death or non-fatal myocardial infarction but a relatively high rate of late revascularization during an intermediate term of follow-up.