Evaluation of left atrial degeneration for the prediction of atrial fibrillation: usefulness of integrated backscatter transesophageal echocardiography.

OBJECTIVES: The purpose of this study was to elucidate the usefulness of integrated backscatter (IBS) transesophageal echocardiography (TEE) for the evaluation of atrial degeneration and clarify whether atrial degeneration predicts the occurrence of atrial fibrillation (AF). BACKGROUND: One of the causes of AF is pathological degeneration of the left atrium (LA). However, there is no appropriate method to evaluate degeneration of the LA in the clinical setting. METHODS: The IBS images were acquired with TEE with a 4- to 7-MHz transducer. The IBS values were calculated as the average power of the backscattered signal from regions of interest (ROI). In the pathological study, we measured IBS values of 21 left atrial specimens obtained from 10 autopsied hearts. Relative interstitial area in the ROI was automatically calculated by a personal computer. In the clinical study, we measured IBS values of the entire LA wall at 5-mm intervals (except the posterior wall) in 42 patients (18 non-AF patients, 14 paroxysmal AF patients, and 10 chronic AF patients). Each IBS value was color-coded to construct 3-dimensional maps. RESULTS: There was a weak correlation between the relative interstitial area and IBS values (r = 0.45, p = 0.038). Average corrected IBS values of total voxels in color-coded maps in the AF group (24.4 +/- 6.4 dB) and the paroxysmal AF group (23.9 +/- 9.6 dB) were significantly greater than those in the non-AF group (15.6 +/- 7.4 dB, p = 0.007), whereas there was no significant difference in LA diameter between the paroxysmal AF group (39.4 +/- 6.5 mm) and the non-AF group (36.7 +/- 5.5 mm). CONCLUSIONS: With IBS-TEE, we can identify an increase in atrial degeneration that might predict the occurrence of AF before LA dilation.

Tissue characterization of coronary plaques: comparison of integrated backscatter intravascular ultrasound with virtual histology intravascular ultrasound.

BACKGROUND: Integrated backscatter (IB) intravascular ultrasound (IVUS) and IVUS Virtual Histology (VH) have been developed for tissue characterization, but have never been compared directly. The purpose of this study was to compare the overall agreement between IB-IVUS and IVUS-VH in the tissue characterization of plaques from the same coronary arterial cross-section. METHODS AND RESULTS: Images were acquired from 46 coronary arteries from 25 cadavers. Of a total of 392 histology/IVUS image pairs, 152 pairs were diagnosed as Stary's type III, IV, Va, Vb and Vc, and compared for IB-IVUS, IVUS-VH and histology. In the qualitative comparison, the overall agreement between histological and IB-IVUS diagnoses was higher (kappa = 0.81, 95% confidence interval (CI): 0.74-0.89) than that of the IVUS-VH diagnoses (kappa = 0.66, 95%CI: 0.56-0.75). The % fibrosis area determined by IB-IVUS was significantly correlated with the relative area of fibrosis based on histology (r = 0.67, p < 0.001). In the quantitative comparison, the overall agreement between the histological and IB-IVUS diagnoses was higher (kappa = 0.83, 95% CI: 0.75-0.91) than that of the IVUS-VH diagnoses (kappa = 0.73, 95% CI: 0.63-0.83). CONCLUSION: Based on histology as the gold standard, IB-IVUS provided higher diagnostic accuracy than IVUS-VH for tissue characterization of coronary plaques.

Dual blockade of the rennin-angiotensin system versus maximal recommended dose of angiotensin II receptor blockade in chronic glomerulonephritis.

BACKGROUND: Proteinuria and hypertension are predictors of poor renal outcome in chronic glomerulonephritis (CGN). At the same level of blood pressure (BP) control, we evaluated which is superior, dual blockade of the rennin-angiotensin system (RAS) with both angiotensin-converting enzyme inhibitor (ACEI) and angiotensin II type 1 (AT-1) receptor blockade (ARB) or single blockade of ARB to reduce proteinuria and to preserve renal function in patients with CGN. METHODS: In this prospective, parallel, open study of 86 patients with CGN, we compared the effects on proteinuria and renal functions of 36 months with comparable blood pressure (BP) control achieved by candesartan cilexetil (candesartan, 4-12 mg/day) or benazepril hydrochrolide (benazepril, 2.5-10 mg/day) with candesartan (4 mg/day). Aiming at BP 125/75 mmHg or less, the dose of candesartan (single blockade) or benazepril (dual blockade) was increased. RESULTS: Dual blockade decreased proteinuria more than single blockade with ARB (-42.3 vs. -60.5%, P < 0.01). Renal plasma flow (RPF) and glomerular filtration fraction (GFR) did not change significantly in either group. The filtration fraction (FF) decreased dual blockade more than single blockade (-1.7 vs. -19.0%, P < 0.05). Decreased FF was associated with the reduction of proteinuria (P < 0.05). Six percent of patients with dual blockade were not able to continue the study because of a dry cough. CONCLUSION: Long-term dual blockade decreased proteinuria more than single blockade with ARB. Although ARB and ACEI have a glomerular size-selective function for proteinuria, a greater antiproteinuric effect may depend on renal hemodynamics, especially FF. Increased levels of bradykinin after ACEI can decrease FF and ameliorate proteinuria. Dry cough is a significant adverse effect of ACE inhibitor.

Development of integrated backscatter intravascular ultrasound for tissue characterization of coronary plaques.

Tissue characterization of plaques of coronary arteries is important to clarify the process of acute coronary syndrome and prevent it. The purpose of this study is to develop an online integrated backscatter intravascular ultrasound (IB-IVUS) system and validate the diagnostic accuracy for the characterization of coronary plaques. A personal computer equipped with custom software was connected to an IVUS imaging system. Images were acquired from 242 segments of 46 coronary arteries from 25 cadavers obtained at autopsy. In the training study, a total of 724 regions-of-interests on color-coded maps were compared with histologic images. In the validation study, a total of 192 cross-sections of coronary arteries were evaluated. Receiver operating characteristic curve analysis showed that the cut-off points of -49 dB (area under curve = 0.98) and -29 dB (area under curve = 0.99) were the most reliable predictors of lipid pools, fibrosis and calcification. In the validation study, the analysis using IB values classified fibrous, lipid-rich and fibrocalcific plaque components with a high accuracy of 93%, 90% and 96%, respectively. The overall agreement between histologic and IB-IVUS diagnoses (n = 175) was high (Cohen's kappa = 0.81). The IB-IVUS system provides high diagnostic accuracy for analysis of tissue characteristics of coronary plaques.