isruption of coronary artery plaque and subsequent thrombosis has been identified as a primary cause of acute coronary syndrome (ACS), which includes acute myocardial infarction and unstable angina, 1-4 and thus, reliable noninvasive detection of plaque is extremely important in patients who have coronary risk factors.Multislice spiral computed tomography (MSCT), which provides simultaneous acquisition of 4-16 sections and 0.4-0.5 s gantry rotation, has been recently developed and initial results indicate that this technique allows visualization of the coronary arteries in both normal subjects and patients with coronary artery disease. 5-9 Moreover, Schroeder et al reported that MSCT can detect coronary artery plaques by demonstrating good agreement of plaque texture between the computed tomography (CT) density of the plaque and that observed by intracoronary ultrasound (ICUS): plaques with a low CT density (0-40 Hounsfield units (HU)) corresponded to those containing a lipid core, and plaques with a medium CT density corresponded to fibrous plaques. 10 Previous pathological and ICUS studies have consistently documented that rupture-prone, vulnerable coronary artery plaques are characterized by the presence of a lipid-rich core and thin fibrous cap. 11-13 Thus, we hypothesized that plaque vulnerability could be evaluated in patients with coronary artery disease by measuring the CT density, so we compared the CT density of the plaque in culprit lesions between patients with ACS and those with stable angina (SA), as well as the CT density between the ACS-related, culprit coronary segment and non-culprit segment in a series of patients with ACS who had multiple plaques. Methods PatientsForty two patients (35 males, 7 females; mean age, 60.0±11.5 years (range: 32-78 years)) with angiographically documented coronary artery disease underwent MSCT. Patients who had undergone previous coronary artery bypass surgery or any kind of percutaneous coronary intervention, including stent implantation and percutaneous transluminal balloon angioplasty, were excluded, as were patients with atrial fibrillation, other supraventricular or ventricular arrhythmias, renal dysfunction (serum creatinine >1.5 mg/dl) or severe left ventricular dysfunction (left ventricular ejection fraction <30%). The final study group consisted of 20 patients (19 males, 1 female; age 54.7±12.3 years) with ACS (17 with acute myocardial infarction, 3 with unstable angina). There were 22 patients with SA (16 males, 6 females; mean age, 64.9±8.4 years). ACS was prospectively defined to satisfy guidelines established by the American College of Cardiology and the American Heart Association (ACC/AHA) 14 with the following modifications. Possible or probable ACS required resting chest pain compatible with myocardial ischemia ≥30 min duration, non ST-segment elevation myocardial infarction required abnormal serial troponin-T (>1.96 g/dl) with a

alfunctioning of a pacemaker because of electromagnetic interference (EMI) was reported after development of the demand pacemaker. 1 Clinically, a variety of medical appliances that produce electromagnetic or radiofrequency waves are now used for diagnostic or therapeutic purposes, and precautions or restrictions on their use have been enforced to protect patients with an implanted pacemaker from possible hazards. [2][3][4][5][6] Computed tomography (CT) is widely used in clinical practice, but a detailed report has not been published of the effects of CT scanning on the operation of pacemakers. Although it is commonly believed that CT scanning does not affect the functioning of pacemakers, we have previously reported a transient malfunction of the pacemaker probably caused by over-sensing. 7 The present study was undertaken to examine the influence of multislice spiral CT on pacemakers in patients and experimental models of the human body. Methods ECG Monitoring During Chest CT Scanning in Pacemaker-Implanted PatientsIn 11 patients with implanted demand-type pacemaker, chest CT scanning using a multislice spiral CT system (4-detector row, SOMATOM Volume Zoom, Siemens, Germany) was performed for further evaluation of abnormal shadows that had been observed on chest X-ray.During the CT scanning, the ECGs of the extremity leads were recorded at a paper feed rate of 25 mm/s. All patients gave informed consent. Measurement of Alternating Electric and Magnetic Fields in the CT Room and on CT Scan LinesThis experiment was conducted to examine whether the CT procedure produces electromagnetic fields in the CT room and induces EMI with pacemakers. Alternations of the electric and magnetic fields on the CT scanning line, and at points 1 m distant from the CT scanning line within the CT room, were measured during CT scanning using an electric-field measuring device (FD-1, Combinova, Sweden) and a magnetic-field measuring device (Model 5080, F.W. Bell, Orlando, FL, USA). The measurements were repeated 3 times, and the maximum values were adopted. Effects of CT Scanning on Pacemaker Function in Human Body ModelsThe pacemakers, Thera SR8960i and Kappa SR701 (Medtronic, Minneapolis, MN, USA), combined with a 5024M lead (Medtronic) were mounted in Irnich's human body model (Fig 1) 8-10 and subjected to CT scanning. The bench model (Fig 2) was constructed for this study to clarify the conditions induced by CT scanning that might influence pacemaker function.Measuring Systems The Irnich's body model was filled with 0.18 w-% saline, and the electroconductivity of the model was set at a value equivalent to that of the human body. Pick-up electrodes to receive pacing pulses from the pacemaker were attached to the pacemaker lead. Specific electrodes to input the sensing signals (known as cenelic patterns) produced by the pseudo-beat generator were also arranged on the model. The model was connected to the pseudo-beat generator and recorder via a 20-m cable that Circ J 2006; 70: 190 -197 (Received August 24, 2005; revised manuscrip...

rolonged regional myocardial dysfunction following exercise-induced ischemia has been identified as a sensitive marker of ischemia in both an experimental model 1 and patients with known coronary artery disease (CAD). [1][2][3][4] Nevertheless, the correlation between a wall motion abnormality detected by ECG-gated single-photon emission computed tomography (SPECT) and the angiographic data has not been fully evaluated. ECG-gated SPECT provides information on global as well as regional systolic function, 5,6 in addition to regional myocardial perfusion. Because a regional wall motion (RWM) abnormality may persist for 30-240 min following exercise, 5 ECG-gated SPECT, acquired within 60 min after exercise cessation, has the potential to detect post-stress RWM abnormality in patients with multivessel CAD and highgrade coronary artery stenosis in the proximal coronary artery segments. 7-9 However, the value of wall motion analysis using ECG-gated SPECT in patients with mild, single-vessel CAD has not yet been evaluated and because Circulation Journal Vol.69, March 2005a RWM abnormality is most apparent in the early phase of the post-exercise period, we speculated that wall motion analysis shortly after exercise might give incremental diagnostic value to myocardial perfusion SPECT in patients with mild, single-vessel CAD. Methods Patient PopulationThe study group consisted of 97 normal subjects (Group 1: 57 men, 42 women; age 60±11 years) and 46 patients with angiographically documented single-vessel CAD (Group 2: 40 men, 6 women; age 61±9 years) who underwent separate acquisition, dual isotope ECG-gated SPECT. Group 1 consisted of patients with atypical chest pain who were classified as having a low likelihood of CAD according to the American Heart Association/American Colledge of Cardiology classification for assessment of cardiovascular risk using multiple-risk-factor assessment equations. 10 In all the patients of Group 1, coronary CT angiography was performed using a Siemens SOMATOM Volume Zoon with the image reconstruction method developed in our laboratory 11 and it revealed no significant coronary artery stenosis in their major coronary arteries. The diagnostic accuracy of coronary CT angiography in comparison with invasive coronary angiography has been proved to be excellent, with a sensitivity of 94% and specificity of 97% Circ J 2005; 69: 301 -305

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