Shinji Ono

Regional myocardial perfusion and glucose metabolism in experimental left bundle branch block.

BackgroundSeveral authors have reported cases in which 201TI scintigraphy demonstrated perfusion abnormality in the septum of patients with left bundle branch block (LBBB) and normal coronary arteriogram. The mechanism of this abnormality, however, remains to be clarified. Methods and ResultsTo determine whether LBBB itself induces abnormal myocardial perfusion and ischemia and to elucidate its mechanism, we used an in vivo animal model. LBBB was induced by right ventricular pacing in 17 open-chest dogs. We examined myocardial perfusion and glucose uptake using 201T1 and 18F-labeled 2-fluoro-2-deoxy-D-glucose. 201T1 activity in the septum was reduced to 74.7±14.5% of its maximal activity, and mean activity was 86.5±5.3% in the free wall (p<0.05). 18F activity in the septum was also reduced compared with that in the free wall (67.4±12.1% versus 88.0plusmn;5.2%, p<0.05). Regional myocardial blood flow was significantly reduced in the septum compared with the free wall, averaging 0.53±0.18 ml/min/g versus 0.84±0.14 ml/min/g, respectively (p<0.01). Systolic thickening in the septum was reduced from 1.36±0.20 to 0.98±0.04 (p<0.01) after the induction of LBBB, and the intramyocardial pressure in the septum in diastolic phase, in which the major flow of left anterior descending coronary artery (LAD) exists, increased from 26.6±10.5 to 57.8±22.2 mm Hg (p<0.02). Mean aortic pressure, IAD flow, and lactate extraction rate showed no significant change. ConclusionsLBBB itself may reduce myocardial perfusion and glucose uptake in the septum because of impaired systolic thickening and augmented intramyocardial pressure in the septum; however, this is not necessarily related to septal ischemia.

Effectiveness of tranilast on restenosis after directional coronary atherectomy

Tranilast is an antiallergic drug used widely in Japan that also inhibits the migration and proliferation of vascular smooth muscle cells. This pilot study was undertaken to determine the effectiveness of tranilast on restenosis after successful directional coronary atherectomy. After the procedure, 40 patients (56 lesions, tranilast group) were treated with oral tranilast for 3 months, and 152 patients (188 lesions, control group) did not receive tranilast. Angiographic and clinical variables were compared between the two groups. The minimal lumen diameter was significantly larger in the tranilast group than in the control group at both 3-month (2.08 vs 1.75 mm, p = 0.004) and 6-month follow-up (2.04 vs 1.70 mm, p = 0.003). The diameter stenosis in the tranilast group was smaller than that in the control group both 3 months (28% vs 40%, p = 0.0007) and 6 months (30% vs 43%, p = 0.0001) after the procedure, with a lower restenosis rate (percent diameter stenosis > or =50) in the tranilast group at 3 months (11 % vs 26%, p = 0.03). The number of clinical events over the 12-month period after the procedure was significantly reduced by tranilast administration (p = 0.013). These findings suggest that the oral administration of tranilast strongly prevents restenosis after directional coronary atherectomy.

Oxidative metabolism in the myocardium in normal subjects during dobutamine infusion.

To assess the biventricular response of the clearance rate of carbon-11 acetate as an index of myocardial oxidative metabolism to increase in work-load, dynamic positron emission tomography was performed at rest and during dobutamine infusion in 14 normal subjects. The clearance rate constant (Kmono) of the left ventricular (LV) myocardium increased during dobutamine infusion (0.112±0.020 min−1 vs 0.065±0.015 min−1 at rest) (P<0.001) in proportion to the increase in the pressure-rate product. Kmono in the right ventricular (RV) myocardium also increased (0.080±0.018 min−1 vs 0.034±0.013 min−1 at rest) (P<0.001), with an excellent correlation with the LV Kmono (r=0.920). The fact that the increase in RV Kmono during dobutamine infusion was greater (158%±81%) than that in LV Kmono (79%±39%) (P < 0.005) indicates a greater increase in oxidative metabolism in the RV in response to inotropic stimulation in normal subjects.

Myocardial oxidative metabolism in normal subjects in fasting, glucose loading and dobutamine infusion states

Experimental studies indicated the clearance rate constant of11C-acetate as an index of regional myocardial oxygen consumption. To assess the response of the clearance rate from the left ventricular (LV) myocardium to the change in plasma substrate levels and to the increase in the cardiac work load in normal subjects, a total of 18 dynamic positron emission tomographic studies were performed at rest in the fasting state (control) (n=7), after oral glucose administration (n=4), and during dobutamine infusion (n=7) in 7 normal volunteers. The clearance rate constant (Kmono) was similar in the control (0.065±0.017 min< 1) and glucose loading states (0.059±0.OO8 min−1), whereas a significant increase in Kmono was observed during dobutamine infusion (0.106±0.018 min−1) (p< 0.01) in relation to the increase in the pressure-rate product with a correlation coefficient of 0.873 (p< 0.01). When the LV myocardium was divided into 6 segments, there were no significant differences among the segments in Kmono values in any condition. These normal responses should be valuable for assessing oxidative metabolic reserve and regional changes in oxidative metabolism in patients with coronary artery disease.

Systematic evaluation of vascular access by color-Doppler ultrasound decreased the incidence of emergent vascular access intervention therapy and X-ray exposure time: a single-center observational study.

Arteriovenous fistula has superior patency over other accesses, but vascular access intervention therapy (VAIVT) for stenosis or thrombosis still remain major reasons for hospital admission of dialysis patients. The aim of this study was to examine the usefulness of systematic evaluation of vascular access by color‐Doppler ultrasound (CDUS). This study was a single‐center observational design study. We planned screening CDUS to evaluate all vascular accesses once per year, and additionally, follow‐up CDUS of post‐interventional patients 1 month, 3 months and 6 months after their recent VAIVT. This systematic evaluation was started from September 2009. The observational period between September 2008 and August 2009 was defined as period A. The observational period between September 2009 and August 2010 was defined as period B. We compared the incidence of emergent VAIVT and X‐ray exposure time during the period A to B. 131 patients with AV fistula were assigned. 13 patients were excluded due to death, hospital transfer or re‐operation of their accesses. During period A, 57 VAIVTs were carried out, and 37 cases (65%) were emergent. During period B, 42 VAIVTs were carried out, and 11 cases (25%) were emergent. The incidence of emergent intervention therapy was lower during period B than period A (P < 0.001). The amount of X‐ray exposure time per patient was decreased in patients who received VAIVT during both periods (P < 0.03). Systematic evaluation of vascular access by CDUS decreased the incidence of emergent VAIVT and X‐ray exposure time.

A Case of Henoch-Schönlein Purpura with Acute Kidney Injury Accompanied by Severe Gross Hematuria and Erythrocytes-Casts Occlusion in Distal Tubules

A 77-year-old man came to our hospital with purpura on lower extremities, severe gross hematuria, and acute kidney injury (AKI). On presentation, he was generally edematous and had no oliguria. Any signs of volume depletion were not detected. After the diagnosis of Henoch-Schönlein purpura (HSP) was confirmed, we initiated hydration and daily oral administration of prednisolone (PSL) (0.6 mg/kg). AKI improved gradually, but hematuria and fecal occult blood (FOB) did not disappear and sustained for four weeks. Therefore, we added mizoribine (MZR) (1 mg/kg/day) to oral PSL. Three weeks after MZR was administered, both of hematuria and positive FOB resolved. Renal biopsy specimen, after AKI improved, showed some erythrocytes-casts occlusion in distal tubules, not severe mesangial cell proliferation, crescents, IgA depositions, or vasculitis. These pathological pictures suggest that one of the causes of renal manifestations might be erythrocytes-casts occlusion in distal tubules, which is similar to the pathological findings of warfarin-related nephropathy. In our case, massive gross hematuria was observed and supposed to make numerous erythrocytes-casts in tubules, and it might lead to acute tubular injury and AKI. Following his clinical improvement, we tapered oral prednisolone to a dose of 0.4 mg/kg/day and discharged him. This case shows that we should consider occlusive erythrocytes-casts as one of the causes of AKI when we treat HSP patients with severe gross hematuria.