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Biomedical subjects

B Acar

Publications and source records attributed to B Acar.

At least 19 recordsLinked to original sources
PubMed2006

The value of the levels of acute phase reactants for the prediction of familial Mediterranean fever associated amyloidosis: a case control study.

In order to determine the role of levels of acute phase proteins (APPs) for the development of amyloidosis in familial Mediterranean fever (FMF) patients, the levels of serum amyloid A (SAA), C reactive protein (CRP), fibrinogen and erythrocyte sedimentation rate were measured in paired sera of 36 FMF patients during and in between acute attacks, 39 of their healthy parents (obligate heterozgotes), and 15 patients with FMF associated amyloidosis. To compare the levels of APPs, 39 patients with chronic infections or inflammatory diseases who may develop secondary amyloidosis, 20 patients with acute infections who are known to have elevated acute phase response but will never develop amyloidosis and 19 healthy controls were included. The median levels of all APPs are increased in the patients with FMF during attacks and a significant decrease was observed after the attack was over. The level of SAA was above reference range in all FMF patients during the attack free period and the level of at least one other APP was also above normal in 64% of the patients. Both CRP and SAA levels were found to be higher in obligate heterozygotes compared to controls. The levels of SAA in patients with FMF during the attack-free period, obligate heterozygotes and patients with FMF-amyloidosis were found to be similar. The levels in each group were found to be higher than SAA levels found in healthy controls yet lower than the levels measured in the patients with acute infections and patients with chronic inflammation or chronic infections. In conclusion, our results show that SAA level reflects subclinical inflammation with high sensitivity but its value for the prediction of amyloid formation process seems to be low.

Acute-Phase Proteins↗
PubMed2006

The "nutcracker phenomenon" with orthostatic proteinuria: case reports.

The nutcracker phenomenon refers to compression of the left renal vein between the aorta and the superior mesenteric artery. Clinical features are hematuria, abdominal pain, left flank pain, pelvic or scrotal discomfort due to varicocele or ovarian vein syndrome. In this report, 2 patients with orthostatic proteinuria, in whom nutcracker phenomenon was detected as a cause, are presented. One of them had posterior nutcracker with also asymptomatic varicocele that was detected during ultrasonographic examination. Nutcracker phenomenon is a rare but important clinical condition that should be considered in the differential diagnosis of patients with proteinuria and hematuria.

Adolescent↗
PubMed2003

Analysis and generalized correction of the effect of spatial gradient field distortions in diffusion-weighted imaging.

Nonuniformities of magnetic field gradients can cause serious artifacts in diffusion imaging. While it is well known that nonlinearities of the imaging gradients lead to image warping, those imperfections can also cause spatially dependent errors in the direction and magnitude of the diffusion encoding. This study shows that the potential errors in diffusion imaging are considerable. Further, we show that retrospective corrections can be applied to reduce these errors. A general mathematical framework was formulated to characterize the contribution of gradient nonuniformities to diffusion experiments. The gradient field was approximated using spherical harmonic expansion, and this approximation was employed (after geometric distortions were eliminated) to predict and correct the errors in diffusion encoding. Before the corrections were made, the experiments clearly revealed marked deviations of the calculated diffusivity for fields of view (FOVs) generally used in diffusion experiments. These deviations were most significant farther away from the magnet's isocenter. For an FOV of 25 cm, the resultant errors in absolute diffusivity ranged from approximately -10% to +20%. Within the same FOV, the diffusion-encoding direction and the orientation of the calculated eigenvectors can be significantly altered if the perturbations by the gradient nonuniformities are not considered. With the proposed correction scheme, most of the errors introduced by gradient nonuniformities can be removed.

Anisotropy↗
PubMed2001

T-wave morphology differences between patients with and without arrhythmic complication of ischemic heart disease.

The study investigated the differences in T-wave morphology between normal controls, patients with an uncomplicated follow-up after a myocardial infarction (MI), and patients with ischaemic heart disease and a history of ventricular tachycardia/fibrillation (VT/VF). The study population consisted of 164 healthy patients (age 53.4 +/- 18.7 years old, 80 women), 123 VT/VF patients (age 63.8 +/- 10.1 years old, 15 women), and 196 MI patients (age 59.2 +/- 10.0 years old, 23 women). In all patients, supine resting signal-averaged orthogonal electrocardiograms were obtained. After singular value decomposition of electrocardiogram signal, 2 T-wave morphology descriptors were calculated: total cosine R to T describing the global angle between repolarisation and depolarisation loops, and percentage of loop area expressing the irregularity of the T-wave loop (a more irregular wave results in a lower percentage of loop area value). Both parameters were practically uncorrelated (Controls: r = - .106, MI r = .161, and VT/VF r = .173) and different between individual groups of patients: total cosine R to T (Control vs. MI: P = 4.3 x 10(-8), Control vs. VT/VF: P = 2.7 x 10(-16), MI vs. VT/VF: P = 3.1 x 10(-6)), percentage of loop area (Control vs. MI: P = 0.07, Control vs. VT/VF: P = 1.1 x 10(-8), MI vs. VT/VF: P = 2.9 x 10(-5), all nonparametric Mann-Whitney test). The comparisons of cumulative histograms also revealed significant differences between all three groups for both parameters (Kruskal-Wallis ANOVA test). Thus, these numerical descriptors of T-wave morphology are powerful indicators of arrhythmic complications among patients with ischaemic heart disease. They also differentiate between patients with stable uncomplicated ischaemic heart disease and healthy controls.

Electrocardiography↗
PubMed2001

A statistical 3-D pattern processing method for computer-aided detection of polyps in CT colonography.

Adenomatous polyps in the colon are believed to be the precursor to colorectal carcinoma, the second leading cause of cancer deaths in United States. In this paper, we propose a new method for computer-aided detection of polyps in computed tomography (CT) colonography (virtual colonoscopy), a technique in which polyps are imaged along the wall of the air-inflated, cleansed colon with X-ray CT. Initial work with computer aided detection has shown high sensitivity, but at a cost of too many false positives. We present a statistical approach that uses support vector machines to distinguish the differentiating characteristics of polyps and healthy tissue, and uses this information for the classification of the new cases. One of the main contributions of the paper is the new three-dimensional pattern processing approach, called random orthogonal shape sections method, which combines the information from many random images to generate reliable signatures of shape. The input to the proposed system is a collection of volume data from candidate polyps obtained by a high-sensitivity, low-specificity system that we developed previously. The results of our ten-fold cross-validation experiments show that, on the average, the system increases the specificity from 0.19 (0.35) to 0.69 (0.74) at a sensitivity level of 1.0 (0.95).

Adult↗
PubMed2000

Analysis of 12-lead T-wave morphology for risk stratification after myocardial infarction.

BACKGROUND: The stratification of post-myocardial infarction (MI) patients at risk of sudden cardiac death remains important. The aim of the present study was to assess the prognostic value of novel T-wave morphology descriptors derived from resting 12-lead ECGs. METHODS AND RESULTS: In 280 consecutive post-MI patients, a 12-lead ECG was recorded before discharge, optically scanned, and digitized. For the present study, 5 T-wave morphology descriptors were automatically calculated after singular value decomposition of the ECG signal. The total cosine R-to-T (TCRT [describes the global angle between repolarization and depolarization wavefront]) and the T-wave loop dispersion were univariately associated (P:=0.0002 and P:<0.002, respectively, U: test) with 27 prospectively defined clinical events in 261 patients (mean follow-up 32+/-10 months). Kaplan-Meier event probability curves for strata above and below the median confirmed the strong risk discrimination by TCRT and T-wave loop dispersion (P:<0.003 and P:<0.001, respectively, log-rank test). On Cox regression analysis, with the entering of age, left ventricular ejection fraction, heart rate, QRS width, reperfusion therapy, beta-adrenergic-blocker treatment, and standard deviation of R-R intervals on 24-hour Holter monitoring, TCRT (P:<0.03) yielded independent predictive value, whereas T-wave loop dispersion was of borderline independence (P:=0.064). Heart rate (P:<0.02), left ventricular ejection fraction (P:<0.02), and reperfusion therapy (P:<0.02) also remained in the final model. CONCLUSIONS: Computerized T-wave morphology analysis of the 12-lead resting ECG permits independent assessment of post-MI risk and an improved risk stratification when combined with other risk markers.

Analysis of Variance↗
PubMed2000

Automatic ectopic beat elimination in short-term heart rate variability measurement.

Our studies deal with fully automatic measurement of heart rate variability (HRV) in short term electrocardiograms. Presently, all existing HRV analysis programs require user intervention for ectopic beat identification, especially of supraventricular ectopic beats (SVE). This makes the HRV measurement in large, e.g. epidemiological studies problematic. In this paper, we present a fully automatic algorithm for the discrimination of the ventricular (VE) and SVE ectopic beats from the normal QRS complexes suited for a reliable HRV analysis. The QRS identification is based on the template matching method. The ectopic beats are identified based on several morphological and timing properties of the electrocardiogram (ECG) signal. The method incorporates several approaches and makes HRV analysis of large numbers of electrocardiograms feasible. It uses the template matching for the basic morphology check of the QRS complex and the P-wave, the timing information to avoid unnecessary ectopic beat checks and to adjust thresholds and it also looks for a special QRS morphology, which is common in VEs. We used a testing set of 69 electrocardiograms selected from a large number of recordings. The selected ECGs contained abnormalities including ectopic beats, right branch bundle block, respiratory arrhythmia, blocked atrial extrasystole, high amplitude and wide T-waves. The evaluation of our method showed a specificity of 0.99, supraventricular ectopic beat sensitivity of 0.99 and ventricular ectopic beat sensitivity of 0.98.

Algorithms↗
PubMed2000

Anger attacks in depressed Turkish outpatients.

Anger attacks have been described as sudden spells of anger accompanied by symptoms of autonomic activation and have been experienced by patients as uncharacteristic of them and inappropriate to the situations in which they had occurred. The aim of this study was to assess the prevalence of anger attacks in a non-Western depressed population. We also wanted to see whether depression in patients with anger attacks was qualitatively different from depression without anger attacks. The Anger Attacks Questionnaire, designed by Fava et al. to assess these attacks, was administered to 88 medication-free consecutive outpatients diagnosed as major depression according to DSM-IV criteria by two psychiatrists. The patients also were assessed by the Beck Depression Inventory, the Beck Anxiety Inventory, the Beck Hopelessness Scale, and the Spielberger's State-Trait Anger Expression Inventory. Forty-three (49%) of these patients had reported having anger attacks. The patients with anger attacks were significantly more depressed and anxious than patients without anger attacks. Anger-out and trait anger measures were significantly higher in depressed patients with anger attacks than patients without anger attacks. Patients with anger attacks also scored higher in hopelessness measure and there was a trend toward statistical significance. Our results are in line with previous literature which show, that anger attacks are prevalent in depressed patients. We also conclude that patients with anger attacks constitute a more depressed population than those without anger attacks. Severity of depression emerges as the strongest predictor of the presence of anger attacks in our study.

Adult↗
PubMed2000

New descriptors of homogeneity of the propagation of ventricular repolarization.

Available descriptors of irregularities of ventricular repolarization are of limited clinical value. We studied the effect of autonomic variations on several new descriptors of the three-dimensional T loop. Twelve-lead digital ECGs were recorded continuously in 40 healthy subjects at baseline in the supine position, during postural changes (supine-->sitting-->standing-->supine-->standing), and during Valsalva maneuver performed three times in the supine and three times in the standing positions. A minimum dimensional space was constructed from the 12-lead ECG, using singular value decomposition, on the basis of median ECG beats constructed from 10-second consecutive ECG recordings. Temporal variations (TLA and PL, which measure the T loop area, and LD, the interlead relationship during repolarization) and wavefront direction descriptors (TCRT, the deviation between the QRS and T vectors) were calculated and expressed as normalized values. Values of TLA, PL, and TCRT were significantly lower in the sitting than in the supine position (-38,139 +/- 9099 vs 47,133 +/- 7511, -0.017 +/- 0.005 vs 0.033 +/- 0.005 and -0.032 +/- 0.019 vs 0.071 +/- 0.015, respectively, P < 0.001 for all) and decreased further in the standing position (-88,288 +/- 14,468, -0.067 +/- 0.013, -0.198 +/- 0.025, respectively, P < 0.001 for all). LD increased from supine to sitting (98.7 +/- 29.4 vs -87.5 +/- 15.2, P < 0.001) and increased further, though nonsignificantly in the standing position (118.3 +/- 35.2). TLA, PL, and TCRT decreased from baseline during Valsalva in the supine (-34,118 +/- 11,424 vs 62,234 +/- 12,215, -0.038 +/- 0.014 vs 0.065 +/- 0.010, -0.08 +/- 0.03 vs 0.10 +/- 0.02, respectively, P < 0.001 for all) and standing positions (-108,263 +/- 21,051 vs -68,909 +/- 10,271, -0.109 +/- 0.014 vs -0.048 +/- 0.009, -0.30 +/- 0.035 vs -015 +/- 0.016, respectively, P < 0.05 for all). LD was significantly increased by Valsalva in the supine position (13 +/- 46 vs -153 +/- 30, P < 0.001) and nonsignificantly in the standing position (99 +/- 50 vs 86 +/- 30, P = NS). There were significant correlations among TLA, PL, and LD, and no significant correlation between TCRT and any of the temporal variation descriptors. These new temporal and wavefront direction descriptors are sensitive and rapid detectors of autonomic effects on ventricular repolarization.

Adolescent↗
PubMed2000

QT dispersion does not represent electrocardiographic interlead heterogeneity of ventricular repolarization.

INTRODUCTION: QT dispersion (QTd, range of QT intervals in 12 ECG leads) is thought to reflect spatial heterogeneity of ventricular refractoriness. However, QTd may be largely due to projections of the repolarization dipole rather than "nondipolar" signals. METHODS AND RESULTS: Seventy-eight normal subjects (47+/-16 years, 23 women), 68 hypertrophic cardiomyopathy patients (HCM; 38+/-15 years, 21 women), 72 dilated cardiomyopathy patients (DCM; 48+/-15 years, 29 women), and 81 survivors of acute myocardial infarction (AMI; 63+/-12 years, 20 women) had digital 12-lead resting supine ECGs recorded (10 ECGs recorded in each subject and results averaged). In each ECG lead, QT interval was measured under operator review by QT Guard (GE Marquette) to obtain QTd. QTd was expressed as the range, standard deviation, and highest-to-lowest quartile difference of QT interval in all measurable leads. Singular value decomposition transferred ECGs into a minimum dimensional time orthogonal space. The first three components represented the ECG dipole; other components represented nondipolar signals. The power of the T wave nondipolar within the total components was computed to measure spatial repolarization heterogeneity (relative T wave residuum, TWR). QTd was 33.6+/-18.3, 47.0+/-19.3, 34.8+/-21.2, and 57.5+/-25.3 msec in normals, HCM, DCM, and AMI, respectively (normals vs DCM: NS, other P < 0.009). TWR was 0.029%+/-0.031%, 0.067%+/-0.067%, 0.112%+/-0.154%, and 0.186%+/-0.308% in normals, HCM, DCM, and AMI (HCM vs DCM: NS, other P < 0.006). The correlations between QTd and TWR were r = -0.0446, 0.2805, -0.1531, and 0.0771 (P = 0.03 for HCM, other NS) in normals, HCM, DCM, and AMI, respectively. CONCLUSION: Spatial heterogeneity of ventricular repolarization exists and is measurable in 12-lead resting ECGs. It differs between different clinical groups, but the so-called QT dispersion is unrelated to it.

Adult↗
PubMed1999

Spatial, temporal and wavefront direction characteristics of 12-lead T-wave morphology.

Three new approaches for the analysis of ventricular repolarisation in 12-lead electrocardiograms (ECGs) are presented: the spatial and temporal variations in T-wave morphology and the wavefront direction difference between the ventricular depolarisation and repolarisation waves. The spatial variation characterises the morphology differences between standard leads. The temporal variation measures the change in interlead relationships. A minimum dimensional space, constructed by ECG singular value decomposition, is used. All descriptors are measured using the ECG vector in the constructed space and the singular vectors that define this space. None of the descriptors requires time domain measurements (e.g. the precise detection of the T-wave offset), and so the inaccuracies associated with conventional QT interval related parameters are avoided. The new descriptors are compared with the conventional measurements provided by a commercial system for an automatic evaluation of QT interval and QT dispersion in digitally recorded 12-lead ECGs. The basic comparison uses a set of 1100 normal ECGs. The short-term intrasubject reproducibility of the new descriptors is compared with that of the conventional measurements in a set of 760 ECGs recorded in 76 normal subjects and a set of 630 ECGs recorded in 63 patients with hypertrophic cardiomyopathy (ten serial recordings in each subject of both these sets). The discriminative power of the new and conventional parameters to distinguish normal and abnormal repolarisation patterns is compared using the same set. The results show that the new parameters do not correlate with the conventional QT interval-related descriptors (i.e. they assess different ECG qualities), are generally more reproducible than the conventional parameters, and lead to a more significant separation between normal and abnormal ECGs, both univariately and in multivariate regression models.

Adolescent↗
PubMed1999

SVD-based on-line exercise ECG signal orthogonalization.

An orthogonalization method to eliminate unwanted signal components in standard 12-lead exercise electrocardiograms (ECG's) is presented in this work. A singular-value-decomposition-based algorithm is proposed to decompose the signal into two time-orthogonal subspaces; one containing the ECG and the other containing artifacts like baseline wander and electromyogram. The method makes use of redundancy in 12-lead ECG. The same method is also tested for reconstruction of a completely lost channel. The online implementation of the method is given. It is observed that the first two decomposed channels with highest energy are sufficient to reconstruct the ST-segment and J-point. The dimension of the signal space, on the other hand, does not exceed three. Data from 23 patients, with duration ranging from 9 to 21 min, are used.

Algorithms↗
PubMed1998

Relation between bone mineral content and clinical, hormonal and biochemical parameters in postmenopausal women.

We studied factors related to bone mass after a natural or surgical menopause in 73 healthy women attending the menopause clinic of a university hospital. In the natural menopause group we found inverse correlations between bone mineral density (BMD) vs. menopausal duration; BMD vs. body mass index (BMI) and BMI vs. inorganic phosphate (Pi), borderline correlations between weight vs. thyroxin (T4) and weight vs. luteinising hormone (LH) and a positive correlation between androstenedione (D4A) vs. urinary calcium (Uca). In the surgical menopause group we found some negative correlations (BMD vs. menopausal duration, BMI vs. Pi; BMI vs. dehydroepiandrosterone sulphate (DS), weight vs. DS and cortisol vs. Uca) and some positive correlations (BMD vs. free testosterone (fT), BMD vs. calcium (Ca), and BMD vs. Uca). We concluded that the serum hormone levels we measured were not useful markers of current bone mineral status.

Adult↗
PubMed1995

Risk factors for Wolfe's dysplasia of mammograms in postmenopausal Turkish women.

OBJECTIVE: The aim was to ascertain whether menstrual, reproductive and hormonal risk factors for breast cancer are present in women with dysplastic mammographic patterns and to investigate possible trends towards breast cancer. METHOD: This prospective case-control study was designed in a university hospital. Thirty-two turkish postmenopausal women were evaluated for the associations between obesity, parity, age, age at menarche, age at menopause, total lactation period and dysplasic mammographic patterns. RESULTS: We found an increasing trend of dysplasia with increasing age at menarche. This association contradicts the well established one for breast cancer. The effects of parity and total lactation period on dysplasia were similar. Although nulliparity had some protective effects on dysplasia, relative risk (RR) increased to some extent with an increase in parity and lactation period. Later menopause and older age were associated with an increase risk of dysplasia, whereas an apparent protection was given by greater body mass index. CONCLUSION: Onset of the menopause increases the risk of dysplasia and the estrogenic milieu may have some role in the initiation and progression of dysplasia.

Aging↗
PubMed1994

Plasma copper, zinc and magnesium levels in patients with premenstrual tension syndrome.

We measured plasma Cu. Zn and Mg levels in 40 women suffering from premenstrual tension syndrome (PMTS) and in 20 control subjects by atomic absorption spectrophotometer. Mean plasma Cu, Zn and Mg levels, the Zn/Cu ratio were 80.2 +/- 6.00 micrograms/dl, 112.6 +/- 8.35 micrograms/dl, 0.70 +/- 0.18 mmol/l, and 1.40 +/- 0.10 in the PMTS group; and 77.0 +/- 4.50 micrograms/dl, 117.4 +/- 9.50 micrograms/dl, 0.87 +/- 0.10 mmol/l, and 1.51 +/- 0.05 in the control group respectively. The mean Mg level and the Zn/Cu ratio were significantly lower in PMTS patients than in the control group. Plasma Mg and Zn levels were diminished significantly during the luteal phase compared to the follicular phase in PMTS group. Mg deficiency may play a role in the etiology of PMTS.

Copper↗
PubMed1993

Diminished growth hormone responses to L-dopa in polycystic ovarian disease.

OBJECTIVE: To investigate the GH secretion capacity in polycystic ovarian syndrome (PCOS). DESIGN: Prospective. SETTING: Reproductive endocrinology unit. PATIENTS: Nineteen women with clinical and endocrinologic signs of PCOS were compared with 10 healthy weight-matched volunteers with normal menstrual rhythm and no history of endocrine or reproductive abnormality. INTERVENTIONS: Standard GH reserve estimates were affected in all subjects using oral L-Dopa. The test was carried out after an overnight fast on cycle days 5 to 8 in menstruating subjects; the test was done randomly in patients with amenorrhea. RESULTS: Both PCOS and control groups responded to L-Dopa over a 3-hour period with significant elevations in GH concentrations. The control group showed significantly higher values than the PCOS group at 90, 120, and 180 minutes. CONCLUSION: The findings indicate that PCOS patients demonstrate a relative deficiency in GH reserve.

Adolescent↗