Katsushi Hashimoto

X-ray Diffraction from a Left Ventricular Wall of Rat Heart

We studied x-ray diffraction from the left ventricular wall of an excised, perfused whole heart of a rat using x rays from the third-generation synchrotron radiation facility, SPring-8. With the beam at right angles to the long axis of the left ventricle, well-oriented, strong equatorial reflections were observed from the epicardium surface. The reflections became vertically split arcs when the beam passed through myocardium deeper in the wall, and rings were observed when the beam passed into the inner myocardium of the wall. These diffraction patterns were explained by employing a layered-spiral model of the arrangement of muscle fibers in the heart. In a quiescent heart with an expanded left ventricle, the muscle fibers at the epicardium surface were found to have a (1,0) lattice spacing smaller than in the rest of the wall. The intensity ratio of the (1,0) and (1,1) equatorial reflections decreased on contraction with a similar time course in all parts of the wall. The results show that it is possible to assign the origin of reflections in a diffraction diagram from a whole heart. This study offers a basis for interpretation of x-ray diffraction from a beating heart under physiologically and pathologically different conditions.

Additional diagnostic value of first-pass myocardial perfusion imaging without stress when combined with 64-row detector coronary CT angiography in patients with coronary artery disease

Objective Multi-detector coronary CT angiography (CCTA) can detect coronary stenosis, but it has a limited ability to evaluate myocardial perfusion. We evaluated the usefulness of first-pass CT-myocardial perfusion imaging (MPI) in combination with CCTA for diagnosing coronary artery disease (CAD). Methods A total of 145 patients with suspected CAD were enrolled. We used 64-row multi-detector CT (Definition Flash, Siemens). The same coronary CCTA data were used for first-pass CT-MPI without drug loading. Images were reconstructed by examining the signal densities at diastole as colour maps. Diagnostic accuracy was assessed by comparison with invasive coronary angiography. Results First-pass CT-MPI in combination with CCTA significantly improved diagnostic performance compared with CCTA alone. With per-vessel analysis, the sensitivity, specificity, positive predictive value and negative predictive value increased from 81% to 85%, 87% to 94%, 63% to 79% and 95% to 96%, respectively. The area under the receiver operating characteristic curve for detecting CAD also increased from 0.84 to 0.89 (p=0.02). First-pass CT-MPI was particularly useful for assessing segments that could not be directly evaluated due to severe calcification and motion artefacts. Conclusions First-pass CT-MPI has an additional diagnostic value for detecting coronary stenosis, in particular in patients with severe calcification.

Different sizes of centrilobular ground-glass opacities in chest high-resolution computed tomography of patients with pulmonary veno-occlusive disease and patients with pulmonary capillary hemangiomatosis

BACKGROUND Centrilobular ground-glass opacity (GGO) is one of the characteristic findings in chest high-resolution computed tomography (HRCT) of patients with pulmonary veno-occlusive disease (PVOD) and patients with pulmonary capillary hemangiomatosis (PCH). However, clinical differential diagnosis of these two diseases is difficult and has not been established. In order to clarify their differences, we compared the sizes of GGOs in chest HRCT and the sizes of capillary assemblies in pulmonary vascular casts between patients diagnosed pathologically with PVOD and PCH. METHODS We evaluated chest HRCT images for four patients with idiopathic pulmonary arterial hypertension (IPAH), three patients with PVOD and three patients with PCH, and we evaluated pulmonary vascular casts of lung tissues obtained from those patients at lung transplantation or autopsy. RESULTS Centrilobular GGOs in chest HRCT were observed in patients with PVOD and patients with PCH but not in patients with IPAH. We measured the longest diameter of the GGOs. The size of centrilobular GGOs was significantly larger in patients with PCH than in patients with PVOD (5.60±1.43 mm versus 2.51±0.79 mm, P<.01). We succeeded in visualization of the 3-dimensional structures of pulmonary capillary vessels obtained from the same patients with PVOD and PCH undergoing lung transplantation or autopsy and measured the diameters of capillary assemblies. The longest diameter of capillary assemblies was also significantly larger in patients with PCH than in patients with PVOD (5.44±1.71 mm versus 3.07±1.07 mm, P<.01). CONCLUSION Measurement of the sizes of centrilobular GGOs in HRCT is a simple and useful method for clinical differential diagnosis of PVOD and PCH.

Effect of regional myocardial perfusion abnormalities on regional myocardial early diastolic function in patients with hypertrophic cardiomyopathy

SummaryNonuniform hypertrophy of the left ventricle is an important factor in regional diastolic dysfunction in patients with hypertrophic cardiomyopathy (HCM). However, the effect of myocardial perfusion abnormalities on regional diastolic dysfunction has not been established in patients with HCM. We investigated the relationship between regional myocardial perfusion abnormalities and regional early diastolic function in 31 patients with HCM and 8 control patients. Short-axis images of the left ventricle recorded by cine magnetic resonance imaging were divided into ten blocks. The time-to-peak-wall-thickness-thinning rate (TPWR) and the wall thickness were measured in each block. Of the 310 blocks from the patients with HCM, 242 (78%) showed normal thallium-201 uptake (group 1), 40 (13%) showed slightly decreased uptake (group 2), and 28 (9%) showed markedly decreased uptake (group 3). There was no difference in the regional wall thickness among the three groups. The TPWR was longer in patients with HCM than in control patients. It was significantly longer in group 3 (190±45ms) than in group 1 (167±36ms) and group 2 (160±31ms). (P<0.01). The linear regression slope of the relationship between the TPWR and the regional wall thickness was significantly steeper in group 3 than in groups 1 and 2 (P<0.05). In conclusion, abnormalities in regional myocardial perfusion, in addition to regional hypertrophy, contributed to the regional early diastolic dysfunction in patients with HCM.

Altered nano/micro-order elasticity of pulmonary artery smooth muscle cells of patients with idiopathic pulmonary arterial hypertension.

BACKGROUND Idiopathic pulmonary arterial hypertension (IPAH) is a disease characterized by progressively increased resistance of pulmonary arteries. In this study, we evaluated the mechanical property of single pulmonary artery smooth muscles cells (PASMC) from patients with IPAH and tested whether the PASMC showed abnormal response to a vasodilator by use of an atomic force microscope (AFM). METHODS PASMC were isolated and cultured from explanted lungs of 7 patients with IPAH (IPAH-PASMC). Normal vascular specimens from 3 patients with bronchogenic carcinoma were used as normal controls (normal PASMC). The nano/micro-order elasticity of five to ten living PASMC in each sample was measured by parabolic force curves of cantilever deflection/indentation obtained by using an AFM. The elasticity measurements were performed under control conditions and under condition of nitric oxide (NO) treatment (190 and 380 nmol/L). RESULTS There was no significant difference between nano/micro-order elasticity of normal PASMC and that of IPAH-PASMC under the control conditions. In normal PASMC, NO (190 and 380 nmol/L) significantly reduced (i.e., softened) the nano/micro-order elasticity. However, NO did not reduce elasticity in IPAH-PASMC, indicating higher vasodilator-resistive nano/micro-order rigidity in IPAH-PASMC. CONCLUSION Nano/micro-order elasticity change in PASMC in response to vasodilation induced by NO is reduced in patients with IPAH.

Clinical characteristics of responders to treatment with tolvaptan in patients with acute decompensated heart failure: Importance of preserved kidney size

BACKGROUND Recent clinical trials have demonstrated the efficacy of short-term treatment with tolvaptan, an oral vasopressin V2 receptor antagonist, in patients with heart failure. However, the response to tolvaptan varies among patients. The aim of this study was to determine factors associated with response to tolvaptan in patients with acute decompensated heart failure (ADHF). METHODS The Tolvaptan Registry, a prospective, observational, multicenter cohort study performed in Japan, aims to determine factors affecting the responsiveness of tolvaptan in patients with ADHF. We enrolled ADHF patients treated with tolvaptan and they were divided into two groups: responders and non-responders. Responders were defined as subjects who met all of the following three conditions: (1) increasing urine volume during a 24-hour period after the start of tolvaptan treatment; (2) improvement in New York Heart Association functional class; and (3) decrease in cardiothoracic ratio assessed by chest X-ray on day 3 of tolvaptan administration. RESULTS Among the 114 patients, treatment with tolvaptan improved three conditions of heart failure in more than half of all the cohorts (71 patients, 62%). As for baseline characteristics, estimated glomerular filtration rate, urine osmolality, and kidney size were significantly greater in responders than in non-responders. Multivariate logistic analysis revealed that kidney size was independently associated with responders (odds ratio: 1.083, p=0.001, 95% confidence interval 1.031-1.137). CONCLUSIONS The main clinical characteristic of responders to treatment with tolvaptan is that kidney size is preserved.

Ventricular tachycardia in a patient with cardiac lipoma.

These images demonstrate ventricular tachycardia (VT) associated with cardiac lipoma in the left ventricle. A 22-year-old man suffered from an attack t)f palpitations and faintness, for which he was admitted to our hospital. He was found to have regular tachycardia at a rate of 230/min. The tachycardia was terminated by lidocaine. Echocardiography and cardiac catheterization revealed a large mass in the left ventricle beneath the mitral valve.

Dual Antiplatelet Therapy Can Be Discontinued at Three Months after Implantation of Zotarolimus-Eluting Stent in Patients with Coronary Artery Disease

Dual antiplatelet therapy (DAPT) after percutaneous coronary intervention increases the risk of bleeding. We studied the safety and clinical outcomes of switching from DAPT to aspirin monotherapy at 3 months after ZES implantation. We retrospectively evaluated 168 consecutive patients with coronary artery disease who had been implanted with a ZES from June 2009 through March 2010. After excluding 40 patients according to exclusion criteria such as myocardial infarction, 128 patients were divided into a 3-month DAPT group (67 patients, 88 lesions) and a 12-month conventional DAPT group (61 patients, 81 lesions). Coronary angiographic followup and clinical followup were conducted at more than 8 months and at 12 months after ZES implantation, respectively. Minor and major bleeding events, stent thrombosis (ST), and major adverse cardiac events (MACE) (death, myocardial infarction, cerebrovascular accident, target lesion revascularization, and target vessel revascularization) were evaluated. There were no statistically significant differences in the incidences of ST and MACE between the two groups. The incidence of bleeding events was significantly lower in the 3-month group than in the 12-month group (1.5% versus 11.5%, P < 0.05). DAPT can be safely discontinued at 3 months after ZES implantation, which reduces bleeding risk.

An X-ray diffraction study on contraction of rat papillary muscle with different afterloads.

In the crossbridge theory of muscle contraction (Huxley, 1957), muscle shortening is caused by crossbridges rapidly attaching and detaching from actin. At a given moment the number of crossbridges formed during shortening is smaller than in isometric contraction because they cannot keep attached to allow filament sliding. In skeletal muscles, this prediction has been tested by the x-ray diffraction technique (Podolsky et al., 1976; Huxley, 1979; Amemiya et al., 1980; Yagi & Takemori, 1995). Generally, the intensities of the equatorial (1,0) and (1,1) reflections, which are related to the number of myosin heads in the vicinity of the thin filament (Haselgrove & Huxley, 1973) are affected only by shortening with a small load (0–30%). This observation has been explained by the presence of same myosin heads that are weakly attached to actin during shortening (Yagi & Takemori, 1995). They are not actively producing force but remain in the vicinity of the thin filament, making the equatorial intensities close to those during isometric contraction.