Futoshi Tadehara

Characterization of Noncalcified Coronary Plaques and Identification of Culprit Lesions in Patients With Acute Coronary Syndrome by 64-Slice Computed Tomography

OBJECTIVES We sought to characterize noncalcified coronary atherosclerotic plaques in culprit and remote coronary atherosclerotic lesions in patients with acute coronary syndrome (ACS) with 64-slice computed tomography (CT). BACKGROUND Lower CT density, positive remodeling, and adjacent spotty coronary calcium are characteristic vessel changes in unstable coronary plaques. METHODS Of 147 consecutive patients who underwent contrast-enhanced 64-slice CT examination for coronary artery visualization, 101 (ACS; n = 21, non-ACS; n = 80) having 228 noncalcified coronary atherosclerotic plaques (NCPs) were studied. Each NCP detected within the vessel wall was evaluated by determining minimum CT density, vascular remodeling index (RI), and morphology of adjacent calcium deposits. RESULTS The CT visualized more NCPs in ACS patients (65 lesions, 3.1 +/- 1.2/patient) than in non-ACS patients (163 lesions, 2.0 +/- 1.1/patient). Minimum CT density (24 +/- 22 vs. 42 +/- 29 Hounsfield units [HU], p < 0.01), RI (1.14 +/- 0.18 vs. 1.08 +/- 0.19, p = 0.02), and frequency of adjacent spotty calcium of NCPs (60% vs. 38%, p < 0.01) were significantly different between ACS and non-ACS patients. Frequency of NCPs with minimum CT density <40 HU, RI >1.05, and adjacent spotty calcium was approximately 2-fold higher in the ACS group than in the non-ACS group (43% vs. 22%, p < 0.01). In the ACS group, only RI was significantly different between 21 culprit and 44 nonculprit lesions (1.26 +/- 0.16 vs. 1.09 +/- 0.17, p < 0.01), and a larger RI (> or = 1.23) was independently related to the culprit lesions (odds ratio: 12.3; 95% confidential interval: 2.9 to 68.7, p < 0.01), but there was a substantial overlap of the distribution of RI values in these 2 groups of lesions. CONCLUSIONS Sixty-four-slice CT angiography demonstrates a higher prevalence of NCPs with vulnerable characteristics in patients with ACS as compared with stable clinical presentation.

Influence of type 2 diabetes mellitus on cardiovascular disease mortality: findings from the Hawaii-Los Angeles-Hiroshima study.

The present study addressed whether diabetes mellitus was a strong risk factor for cardiovascular disease (CVD) death. Between 1976 and 1984, 927 (404 men) Japanese-Americans in Hawaii aged 40-79 years participated at baseline examination including a 75 g oral glucose tolerance test. Diabetes was defined as fasting serum glucose >or=140 mg/dl, 2 h postload glucose >or=180 mg/dl, or the use of drugs for diabetes. Causes of death were classified by ICD-9 codes on the reports from the Hawaii State Public Health Bureau. Until 1994, 178 individuals suffered death; 81 were attributed to CVD and 43 to coronary heart disease (CHD). The age-adjusted and coronary risk factors-adjusted relative risks for CHD and CVD mortality were significant for diabetes both in men and women. The impact of diabetes on CHD mortality was greater for women. However, no gender difference in the contribution of diabetes to fatal CVD was observed. Serum fasting glucose levels tended to be associated with CHD death and were associated with CVD death in diabetic subjects. In conclusion, diabetes is a strong independent risk factor for CVD mortality in Japanese-American men and women. Hyperglycemia is associated with CVD mortality in diabetic subjects.

Predicting Angiographic Narrowing ≥50% in Diameter in Each of the Three Major Arteries by Amounts of Calcium Detected by Electron Beam Computed Tomographic Scanning in Patients With Chest Pain

The evaluation of calcium of the coronary arteries on a vessel-by-vessel basis by use of electron beam computed tomography was useful in obstructed coronary arteries. The absence of coronary calcification in any vessel was highly specific for the absence of an obstructive lesion.

Quinapril with High Affinity to Tissue Angiotensin-Converting Enzyme Reduces Restenosis after Percutaneous Transcatheter Coronary Intervention

Experimental studies have demonstrated that vascular injury resulted in an induction of vascular angiotensin-converting enzyme (ACE), and have suggested that inhibition of vascular ACE might be important in the prevention of restenosis. The present study aimed to determine the effect of quinapril, an ACE inhibitor with high affinity to tissue ACE, on restenosis following coronary intervention. The design of this study was a prospective, randomized, open, and non-placebo controlled trial. Patients with ischemic heart disease were enrolled after successful percutaneous transluminal coronary angioplasty or stent implantation at 7 participating institutions. Two hundred and fifty-three patients with 294 lesions were randomly assigned to the quinapril (10–20 mg per day) group or control group. Administration of quinapril was continued for 3–6 months of the follow-up. Quantitative coronary angiography was performed before and after angioplasty and at follow-up. Core laboratory measurements were performed independently and blinded. Follow-up angiography was performed in 108 patients with 124 lesions in the quinapril group and in 107 patients with 130 lesions in the control group. The baseline characteristics and findings of angioplasty showed no significant differences between the two groups. However, in the quinapril group, restenosis per patient and per lesion was significantly lower (34.3% vs. 47.7%, p < 0.05 and 30.6% vs. 43.8%, p < 0.05). Multivariable analysis revealed that administration of quinapril independently contributed to reducing the restenosis per patient and per lesion (odds ratio, 0.73; 95% confidence interval, 0.54–0.99 and odds ratio, 0.75; 95% confidence interval, 0.57–0.99). In conclusion, quinapril significantly reduces restenosis following coronary intervention.

Association Between Aortic Valve Calcification and Myocardial Ischemia, Especially in Asymptomatic Patients

Aortic valve calcification (AVC) is recognized as a manifestation of systemic arteriosclerosis. However, it is unclear whether AVC is associated with myocardial ischemia. Stress myocardial perfusion SPECT (MPS) is widely used for the diagnosis of myocardial ischemia. However, routine MPS is not recommended, particularly in asymptomatic patients. Accordingly, we investigated the hypothesis that the presence of AVC is strongly associated with inducible myocardial ischemia, even among asymptomatic patients. Methods: We investigated 669 consecutive patients who underwent both adenosine stress 201Tl MPS and echocardiography. We evaluated the extent and severity of myocardial ischemia by the summed difference score (SDS). We defined the presence of myocardial ischemia as SDS ≥ 3 and moderate to severe ischemia as SDS ≥ 8. We classified the severity of AVC according to the number of affected aortic leaflets. We also compared the mean SDS and the prevalence of SDS ≥ 3 and SDS ≥ 8 among patients stratified by the severity of AVC. Results: The presence of AVC was significantly associated with myocardial ischemia (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.10–2.23; P = 0.013) and moderate to severe ischemia (OR, 2.16; 95% CI, 1.26–3.80; P = 0.0061). In 311 asymptomatic patients, AVC was strongly associated with moderate to severe ischemia (OR, 4.31; 95% CI, 1.67–12.8; P = 0.0043). However, the SDS value and the prevalence of SDS ≥ 3 and SDS ≥ 8 did not increase with increasing number of affected aortic leaflets. Conclusion: The presence of AVC may be associated with the presence of myocardial ischemia, particularly in asymptomatic patients. However, we found no association between the extent of AVC and inducible myocardial ischemia. The presence of AVC may be a useful anatomic marker to help identify patients at high risk of myocardial ischemia, particularly asymptomatic patients.

Feasibility of a rapid protocol of 1-day single-isotope rest/adenosine stress Tc-99m sestamibi ECG-gated myocardial perfusion imaging

BackgroundWe previously developed a new rapid protocol for single-isotope rest/adenosine stress technetium 99m sestamibi (MIBI) electrocardiography-gated myocardial perfusion imaging examination. The feasibility and limitations of this rapid protocol are unclear.Methods and ResultsWe examined 422 patients who underwent rest acquisition, which eliminates the waiting time, after injection of low-dose MIBI and drinking 400 mL of water. The patients immediately underwent adenosine stress. Stress acquisition was performed 1 hour after injection of high-dose MIBI. The sensitivity and specificity for detecting significant coronary stenoses were 93% and 70%, respectively. The frequency of significant (moderate or severe) inferior wall artifacts on the rest single photon emission computed tomography images among all patients was 16.3%. The frequency of significant artifacts in patients aged 70 years or older was significantly lower than that in patients aged less than 70 years (11.9% vs 26.9%, P=.0001). Multivariate analysis revealed that age less than 70 years and prior myocardial infarction were predictors of significant artifacts on resting images (P<.0001 and P<.05, respectively).ConclusionsOur rapid protocol for MIBI myocardial perfusion imaging (MPI) provides high-quality images and good patient throughput, and it is effective at reducing the total examination time.

Calibration with currently available low-radiopacity catheters for scaling in digital quantitative coronary angiography.

Tadehara F, Imazu M, Kono S, et al. Calibration with currently available low-radiopacity catheters for scaling in digital quantitative coronary angiography. Invest Radiol 2001;36:705–712. rationale and objectives. In quantitative coronary angiography, the absolute diameters of coronary artery lumina are obtained by using a catheter as a scaling device. methods. We examined the effect of x-ray opacity on the accuracy of calibration methods that use such catheters by varying the concentration of contrast medium in the catheters in phantom experiments with a digital cine imaging system. results. With contrast-filled, currently available catheters, the average increase in the measured calibration factor from the gold standard (as determined by using a measuring scale) was 1.0% and 0.4% in the 13-cm and 17-cm image-intensifier modes, respectively, compared with −9.9% and −12.4% for catheters without contrast medium. The corresponding figures for catheters of the previous generation that lacked contrast medium were 1.0% and 0.4%, respectively. The image contrast of previous-generation catheters filled with saline was closer to that of current-generation catheters filled with contrast medium than that of current-generation catheters filled with saline. conclusions. When used for quantitative coronary angiography by digital angiography, currently available low-radiopacity catheters give more accurate data when filled with contrast medium.

Mathematical simulation of the Wenckebach phenomenon in Purkinje fibers

SummaryWe were able to simulate the Wenckebach phenomenon using a model of a one-dimensional cable, consisting of 20 serially connected Purkinje fiber cells represented by the model of McAllister, Noble, and Tsien. The internal resistance between the 10th and 11th cells was modified to five times the normal. To reconstruct the action potential, the derivative equation was solved using a fourth-order Runge-Kutta algorithm. When the first cell of the cable was stimulated, periodically, at an interval of 610ms, a 9:8 Wenckebach pattern was elicited in the conduction between the tenth and 11th cells. Lower order 5:4, 4:3, 3:2 Wenckebach patterns were observed at pacing cycle length of 605, 600—595, and 590—575 ms, respectively. At a pacing cycle length of 570ms or less, 2:1 block was elicited. In another simulation, only whenINa was 0 could the Wenckebach phenomenon be elicited in a cable model, in which internal cell resistance and membrane capacitance were uniformly set, but in which theINa of the center two cells of the cable were alternated between 1 and 0. A localized increase in internal resistance, a relatively long time constant of deactivation of the delayed rectifier outward current, and a relatively rapid rate of pacing cycle length was necessary to evoke the Wenckebach phenomenon. The conductance of the delayed rectifier current at the end of an action potential increased progressively, except after a dropped beat when it was allowed to decrease. It was concluded that the change of conductance affected the cable property of the fiber and consequently evoked the Wenckebach phenomenon.