Hossein Ahmadi

Do endogenous opioids contribute to the bradycardia of rats with obstructive cholestasis

Endogenous opioids have nitric oxide (NO)‐dependent cardiovascular actions. In the light of biological evidence of accumulation of endogenous opioids in cholestasis and also existence of NO‐dependent bradycardia in cholestatic subjects, this study was carried out to evaluate the role of endogenous opioids in the generation of bradycardia in a rat model of cholstasis. Male Sprague‐Dawley rats were used to induce cholestasis by surgical ligation of the bile duct, with sham‐operated animals serving as a control. The animals were divided into six groups which received naltrexone [20 mg/kg/day, subcutaneously (s.c.)], NG‐l‐nitro‐arginine methyl ester (L‐NAME, 3 mg/kg/day, s.c.), aminoguanidine (200 mg/kg/day, s.c.), l‐arginine (200 mg/kg/day, s.c.), naltrexone + L‐NAME (20 and 3 mg/kg/day, s.c) or saline. One week after the operation, a lead II electrocardiogram (ECG) was recorded and the spontaneously beating atria of the animals were then isolated and the chronotropic responses to epinephrine evaluated. The plasma l‐nitro‐tyrosine level and alanine amino transferase and alkaline phosphatase activities were also measured. The heart rate of cholestatic animals was significantly lower than that of control rats in vivo and this bradycardia was corrected with daily adminstration of naltrexone or L‐NAME. The basal spontaneous beating rate of atria in cholestatic animals was not significantly different from that of sham‐operated animals in vitro. Cholestasis induced a significant decrease in the chronotropic effect of epinephrine. This effect was corrected by daily injection of naltrexone or L‐NAME, or concurrent administration of naltrexone + L‐NAME, and was not corrected by aminoguanidine. l‐arginine had an equivalent effect to L‐NAME and increased the chronotropic effect of epinephrine in cholestatic rats but not in control animals. Bile duct ligation increased the plasma activity of liver enzymes as well as the level of l‐nitro‐tyrosine. l‐arginine and naltrexone treatment significantly decreased the elevation of liver enzymes in bile duct‐ligated rats. Pretreatment of cholestatic animals with naltrexone or L‐NAME decreased the plasma l‐nitro‐tyrosine level. The results suggest that either prevention of NO overproduction or protection against liver damage is responsible for recovery of bradycardia after naltrexone administration.

Factors affecting postoperative morbidity and mortality in isolated coronary artery bypass graft surgery

PurposeThis study was conducted to investigate predictors of mortality before and after isolated coronary artery bypass grafting (CABG).MethodsSingle-institutional data on risk factors and mortality were collected for 8890 patients who underwent isolated CABG by the same group of surgeons. The relationship between risk factors and outcome was assessed using univariate and multivariate analyses in two risk models: a preoperative model (model 1) and then a pre-, intra-, and postoperative model (model 2).ResultsThe mean age of the patients (25.4% women and 74.6% men) was 58.5 ± 9.7 years. Fifty-five (0.6%) patients died after surgery. Hypercholesterolemia was the most common comorbidity factor (61.1%), followed by hypertension, a smoking habit, recent myocardial infarction (MI) <21 days, and diabetes. Postoperative tamponade, graft occlusion, and MI (0.01%) were the least common complications. The patients spent 39.7 ± 33.9 h in the intensive care unit (ICU) postoperatively. Patients were followed up for a minimum of 30 days. The multivariate analysis of our preoperative risk model revealed that the best predictors of operative mortality were a history of diabetes, hypertension, previous CABG, the presence of angina, arrhythmia, Canadian Cardiovascular Society Classification (CCS) of grade III or IV, ejection fraction (EF) ≤30%, three-vessel disease, and left main disease.ConclusionAfter surgery, and with the inclusion of all the pre-, intra-, and postoperative variables into model two, the following were revealed to be prognostic factors for in-hospital mortality: a history of diabetes, hypertension, the presence of angina, CCS grades III or IV, EF −30%, absence of internal mammary artery (IMA) use, prolonged cardiopulmonary bypass (CPB) time, and prolonged ICU stay.

Wavelet based fingerprint image enhancement

Fingerprint image enhancement is aimed at improving the quality of local features for automatic fingerprint identification. It will allow accurate feature extraction and identification. In this paper, we have considered the use of wavelets for fingerprint enhancement mainly due to their spatial localization property as well as capability to use oriented wavelets such as Gabor wavelets for orientation flow estimation. The proposed algorithm consists of two-stage processing: smoothing and Gabor wavelet filtering. Our smoothing part of enhancement algorithm reduces the noise by a new technique based on Gaussian filtering. Since Gaussian filters meet the uncertainty principle at its limits, they are considered here as the best choice for smoothing and noise reduction. The Gabor wavelet is applied to improve the quality of the smoothed image. Gabor filters are commonly used for enhancement in which the frequency and orientation estimation is required for the enhancement. However, the proposed algorithm is independent of the estimation part. Simulation results are included illustrating the capability of the proposed algorithm.

Recommendation quality, transparency, and website quality for trust-building in recommendation agents

A new model for trust-building in recommendation agents is proposed.We consider recommendation quality, transparency, and website quality in the model.We conducted empirical studies in the context of two popular e-commerce websites.The results highlight the importance of perceived transparency for trust-building. Trust is a main success factor for automated recommendation agents on e-commerce sites. Various aspects can contribute to the development of trust toward such an agent, including perceptions about the usefulness of the recommendations, the transparency of the recommendation process, and the general quality of the website. These factors have been analyzed in isolation in the literature though. We propose and evaluate a new trust model that integrates these factors, and allows us to assess their relative importance for trust-building. We conducted empirical studies in the context of two popular e-commerce websites. The findings suggest that transparency is equally important to consumers for building trust as recommendation quality, and that general we site quality contributes to the development of trust. The findings indicate that focusing on recommendation quality may be insufficient and higher levels of adoption of the recommendations can be achieved when several trust-building factors are considered.

A knowledge-based system for breast cancer classification using fuzzy logic method

A knowledge-based system is proposed for breast cancer disease classification.The knowledge-based system uses EM, PCA, CART and fuzzy rule-based methods.WDBC and Mammographic mass datasets are used for the method evaluation.The accuracies obtained by the method are respectively 0.932 and 0.941 for WDBC and Mammographic mass datasets. Breast cancer has become a common disease around the world. Expert systems are valuable tools that have been successful for the disease diagnosis. In this research, we accordingly develop a new knowledge-based system for classification of breast cancer disease using clustering, noise removal, and classification techniques. Expectation Maximization (EM) is used as a clustering method to cluster the data in similar groups. We then use Classification and Regression Trees (CART) to generate the fuzzy rules to be used for the classification of breast cancer disease in the knowledge-based system of fuzzy rule-based reasoning method. To overcome the multi-collinearity issue, we incorporate Principal Component Analysis (PCA) in the proposed knowledge-based system. Experimental results on Wisconsin Diagnostic Breast Cancer and Mammographic mass datasets show that proposed methods remarkably improves the prediction accuracy of breast cancer. The proposed knowledge-based system can be used as a clinical decision support system to assist medical practitioners in the healthcare practice.

Development of an ovine model of myocardial infarction.

Background:  We report experimental myocardial infarction by occluding coronary arteries in ovine models.

Prophylactic ventral cardiac denervation: Does it reduce incidence of atrial fibrillation after coronary artery bypass grafting?

OBJECTIVE This study assessed the prophylactic effect of ventral cardiac denervation on reducing atrial fibrillation after coronary artery bypass grafting. METHODS This randomized prospective study recruited 220 adult patients (aged 42-79 years) who were scheduled to undergo coronary artery bypass grafting. Of these patients, 110 underwent ventral cardiac denervation in addition to coronary artery bypass grafting and 110 underwent only coronary artery bypass grafting. The demographic, intraoperative, and postoperative factors comprising atrial fibrillation were compared between the 2 groups. In addition, the predictive factors of atrial fibrillation in all 220 cases were assessed. RESULTS The mean age and the distribution of gender, body mass index, diabetes mellitus, chronic obstructive pulmonary disease, hypertension, hypercholesterolemia, and left main disease were not significantly different between the 2 groups. Atrial fibrillation incidence was significantly different between the groups (P=.025), with an incidence of 20.9% in the ventral cardiac denervation group and 10% in the control group. Atrial fibrillation occurred in 34 of the 220 patients, and ventral cardiac denervation was considered as a variable to evaluate its possible role in the prevention of postoperative atrial fibrillation. Our multivariate analysis showed age (P=.002; odds ratio,1.098; confidence interval, 1.034-1.165) and ventral cardiac denervation (P=.044; odds ratio,2.32; confidence interval, 1022-5.298) as the predictive factors of atrial fibrillation after coronary artery bypass grafting. CONCLUSIONS Given the surprising results of the present study demonstrating that ventral cardiac denervation is a predictive factor of atrial fibrillation after coronary artery bypass grafting, ventral cardiac denervation should not be routinely considered for the prevention of atrial fibrillation after coronary artery bypass grafting.

Determinant Factors of Renal Failure after Coronary Artery Bypass Grafting with On-Pump Technique

Objective: The aim of the present study was to investigate the determinant factors of acute renal failure (ARF) after isolated on-pump coronary artery bypass grafting (CABG). Subjects and Methods: This was a retrospective study of 13,315 adult patients who underwent isolated CABG with cardiopulmonary bypass (CPB) in Tehran Heart Center from May 2002 to May 2007. The exclusion criteria were age <18, concomitant cardiac and/or noncardiac surgical operations, history of renal failure before surgery, and chronic renal failure requiring dialysis. Preoperative and operative variables were measured, and a multivariate logistic regression model was constructed to identify the independent risk factors for developing renal failure after on-pump CABG. Results: Of the 13,315 patients, 3,347 (25.4%) and 90,883 (74.6%) were females and males, respectively, with a mean age of 58.63 ± 9.48 years. ARF was detected in 85 (0.6%) of the patients with isolated on-pump CABG. The mean age of the patients was 58.63 ± 9.48 years, and 25.5% of them were female. The multivariate logistic regression analysis identified age (OR = 1.035; p = 0.002), female gender (OR = 1.622; p = 0.037), history of peripheral vascular disease (PVD) (OR = 2.579; p = 0.042), diabetes mellitus (OR = 1.918; p < 0.001), emergent and urgent surgery (OR = 1.744 and OR = 7.901, respectively; p = 0.003), CPB time >70 min (OR = 1.944; p = 0.007), and intra-aortic balloon pump (IABP) insertion (OR = 10.181; p < 0.001) as the independent risk factors for ARF. Conclusion: The data showed that age, female gender, positive history of diabetes and PVD, urgent and emergent surgery, CPB time >70 min, and need for IABP were the independent determinant factors of ARF after on-pump CABG.

Total myocardial revascularization for situs inversus totalis with dextrocardia: a case report

We report our experience of two patients suffering from severe coronary artery disease and situs inversus totalis with dextrocardia. The surgeon, standing on the right side of the patients, performed coronary artery bypass grafting by harvesting the right internal mammary artery in lieu of the left one.

Informative wavelet algorithm in diesel engine diagnosis

The informative wavelet methodology is applied for feature extraction and fault classification in a single-cylinder internal combustion engine. The extremely noisy, time-variant and transient vibration signals make wavelets highly suitable for the analysis of such signals in diagnosis applications and can be used to obtain dynamic information about the machine conditions.