Comparative Analysis of the Clustering Quality in Self-Organizing Maps for Human Posture Classification.

The objective of this article is to develop a methodology for selecting the appropriate number of clusters to group and identify human postures using neural networks with unsupervised self-organizing maps. Although unsupervised clustering algorithms have proven effective in recognizing human postures, many works are limited to testing which data are correctly or incorrectly recognized. They often neglect the task of selecting the appropriate number of groups (where the number of clusters corresponds to the number of output neurons, i.e., the number of postures) using clustering quality assessments. The use of quality scores to determine the number of clusters frees the expert to make subjective decisions about the number of postures, enabling the use of unsupervised learning. Due to high dimensionality and data variability, expert decisions (referred to as data labeling) can be difficult and time-consuming. In our case, there is no manual labeling step. We introduce a new clustering quality score: the discriminant score (DS). We describe the process of selecting the most suitable number of postures using human activity records captured by RGB-D cameras. Comparative studies on the usefulness of popular clustering quality scores-such as the silhouette coefficient, Dunn index, Calinski-Harabasz index, Davies-Bouldin index, and DS-for posture classification tasks are presented, along with graphical illustrations of the results produced by DS. The findings show that DS offers good quality in posture recognition, effectively following postural transitions and similarities.

The Measure of Motion Similarity for Robotics Application.

A new measure of motion similarity has been proposed. The formulation of this measure is presented and its logical basis is described. Unlike in most of other methods, the measure enables easy determination of the instantaneous synergies of the motion of body parts. To demonstrate how to use the measure, the data describing human movement is used. The movement is recorded using a professional motion capture system. Two different cases of non-periodic movements are discussed: stepping forward and backward, and returning to a stable posture after an unexpected thrust to the side (hands free or tied). This choice enables the identification of synergies in slow dynamics (stepping) and in fast dynamics (push recovery). The trajectories of motion similarity measures are obtained for point masses of the human body. The interpretation of these trajectories in relation to motion events is discussed. In addition, ordinary motion trajectories and footprints are shown in order to better illustrate the specificity of the discussed examples. The article ends with a discussion and conclusions.

Gait features analysis using artificial neural networks - testing the footwear effect.

PURPOSE: The aim of this paper is to provide the methods for automatic detection of the difference in gait features depending on a footwear. METHODS: Artificial neural networks were applied in the study. The gait data were recorded during the walk with different footwear for testing and validation of the proposed method. The gait properties were analyzed considering EMG (electromyography) signals and using two types of artificial neural networks: the learning vector quantization (LVQ) classifying network, and the clustering competitive network. RESULTS: Obtained classification and clustering results were discussed. For comparative studies, velocities of the leg joint trajectories, and accelerations were used. The features indicated by neural networks were compared with the conclusions formulated analyzing the above mentioned trajectories for ankle and knee joints. CONCLUSIONS: The matching between experimentally recorded joint trajectories and the results given by neural networks was studied. It was indicated what muscles are most influenced by the footwear, the relation between the footwear type and the muscles work was concluded.

Assessment of cardiovascular function following transcatheter aortic valve implantation based on six-minute walk test.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is presently a recognized treatment mo-dality for patients with severe aortic stenosis ineligible for surgery. It reduces mortality as compared to the conservative treatment. It is further expected from this therapy to improve quality of life by improving of the cardiovascular function performance. The aim of this study is to compare patients' cardiovascular system efficiency in the 6-minute walk test (6MWT) made before and after TAVI and at the 6-12-month follow-up. METHODS: From January 2009 until February 2012, in the Silesian Center for Heart Diseases in Zabrze, TAVI was performed in 104 patients. Eighty-two patients who underwent 6MWT before surgery were qualified for the analysis. The average age of the patients was 76.0 ± 9.17 years, women made 45.1%. The risk of surgical treatment according to the Logistic Euroscore averaged 22.76 ± 12.63%, and by the Society of Thoracic Surgeons - 5.55 ± 3.34%. The 6MWT was performed within 1 month before the TAVI procedure, up to a month after the procedure and during the 6-12-month follow-up. RESULTS: The 6-minute walk test after TAVI was performed by 64 patients, and after 6-12 month follow-up by 46 patients. The average distance in 6MWT increased from 268.4 ± 89.0 m before treat-ment to 290.0 ± 98.2 m after the procedure (p = 0.008) and 276.1 ± 93.5 m to 343.1 ± 96.7 m after 6-12 months (p < 0.0001). CONCLUSIONS: Transcatheter aortic valve implantation procedures significantly improve function of the cardiovascular system evaluated by the 6MWT in 1- and 6-12-month observations. (Cardiol J 2017; 24, 2: 167-175).

Stroke and death prediction with CHA2DS2-vasc score after myocardial infarction in patients without atrial fibrillation.

AIMS: The CHA2DS2-VASc score is widely used to stratify the risk of stroke in patients with nonvalvular atrial fibrillation. The aim of the study was to assess whether the CHA2DS2-VASc score might be useful to identify patients at a high risk of ischemic stroke and death among individuals after acute myocardial infarction and with no history of atrial fibrillation. METHODS: We analysed consecutive patients with acute myocardial infarction admitted to our centre between 2003 and 2008. On the basis of the CHA2DS2-VASc score, four groups were distinguished: low-risk (1 point), intermediate-risk (2-3 points), high-risk (4-5 points) and very high-risk (>5 points). Data on long-term follow-up were screened to identify patients who experienced stroke or died during remote observation. RESULTS: Out of 2980 registry participants, 333 were excluded because of atrial fibrillation and/or ongoing therapy with oral anticoagulants. Finally, 2647 individuals were included into the analysis. An ischemic stroke occurred in 71 (2.68%) patients, whereas 439 (16.58%) died during a median follow-up of 41.5 months. The risk of stroke and death increased four-fold in the high-risk group compared with the low-risk group (P < 0.001). Every point in the CHA2DS2-VASc score was independently associated with 41% increase in stroke risk and 23% increase in mortality rate (for both P < 0.001). CONCLUSION: The mortality rate and risk of stroke were strongly associated with the CHA2DS2-VASc scores. Hence, this scoring system could be useful to identify high-risk patients with no history of atrial fibrillation, in whom additional preventive measures might be beneficial to improve the outcome.

Prognostic significance of HbA1c in patients with AMI treated invasively and newly detected glucose abnormalities.

BACKGROUND: Glucose abnormalities are frequent comorbidities influencing prognosis in patients with cardiovascular diseases. The objective of this study was to evaluate prognostic role of HbA1c in patients with acute myocardial infarction (AMI) treated invasively, who had newly detected glucose abnormalities. DESIGN: Single-centre registry encompassed 2146 survivors of AMI. In all patients without diabetes mellitus (DM), oral glucose tolerance test was performed before hospital discharge and interpreted according to the guidelines. METHODS: From the study population, two major groups with defined new glucose abnormalities and estimated HbA1c were selected: 457 patients with impaired glucose tolerance (IGT) and 306 patients with newly detected DM (newDM). In each of these groups, the median value of HbA1c was calculated and established as the cut-off point for further analysis. The median HbA1c for IGT group was 5.9% and for newDM was 7.0%. RESULTS: Patients with IGT and HbA1c ≤ 5.9% had significantly lower posthospital mortality (4.5%) than those with HbA1c >5.9% (25.0%; p<0.001). Similarly, patients with newDM and HbA1c ≤7.0% had lower mortality (6.4%) than those with HbA1c >7.0% (14.3%; p<0.05). Multivariate regression analysis revealed that increase of HbA1c was one of the strongest independent risk factors of death among IGT patients (HR 2.9, 95% CI 2.7-3.1; p < 0.001) and newDM (HR 1.53, 95% CI 1.39-1.66; p<0.05). CONCLUSIONS: Increase of HbA1c in patients with newly detected glucose abnormalities was associated with significantly reduced survival after AMI treated invasively. Moreover, increase of HbA1c in patients with IGT and newDM was one of the strongest independent risk factors of death in these populations.

Role of impaired glucose tolerance in patients with acute myocardial infarction in relation to sex.

INTRODUCTION: Impaired glucose tolerance (IGT) has a negative impact on the outcome of patients with acute myocardial infarction (AMI). OBJECTIVES: The aim of the study was to compare the effect of IGT on early and late prognosis in women and men with AMI treated with percutaneous coronary intervention (PCI). PATIENTS AND METHODS: Based on the results of oral glucose tolerance test, 560 patients with IGT (395 men, 165 women) were selected out of a single center registry of 2733 consecutive patients with AMI. Sex­related mortality and major adverse cardiovascular events (MACEs) including myocardial reinfarction, stroke, or repeat revascularization during hospitalization and long­term follow­up were compared in the whole study population and within the high­risk subgroups. RESULTS: Mortality and MACE rates were comparable between men and women except for a higher stroke rate in women (4.8% vs. 1.5%, P <0.05). No significant differences were observed in the subgroups of patients with reduced ejection fraction (<35%) and those aged above 70 years, during both short and long­term follow­up. However, in women compared with men, higher stroke rates were observed in the subgroup of patients with incomplete revascularization (6.9% vs. 1.1%, P <0.05) and higher total mortality rates in the subgroup with renal dysfunction (40% vs. 16%, P <0.05). Female sex was an independent risk factor for stroke (hazard ratio [HR], 2.94; P = 0.048) and MACEs (HR, 1.45; P = 0.009), but not for death, in the population of patients with AMI and IGT. CONCLUSIONS: Mortality in women and men with AMI treated with PCI with concomitant IGT is comparable, but female sex is an independent risk factor for stroke and MACEs, particularly worsening prognosis in patients with renal dysfunction.

The prognostic value of different glucose abnormalities in patients with acute myocardial infarction treated invasively.

BACKGROUND: Diabetes (DM) deteriorates the prognosis in patients with coronary heart disease. However, the prognostic value of different glucose abnormalities (GA) other than DM in subjects with acute myocardial infarction (AMI) treated invasively remains unclear. AIMS: To assess the incidence and impact of GA on clinical outcomes in AMI patients treated with percutaneous coronary intervention (PCI). METHODS: A single-center, prospective registry encompassed 2733 consecutive AMI subjects treated with PCI. In all in-hospital survivors (n = 2527, 92.5%) without the history of DM diagnosed before or during index hospitalization standard oral glucose tolerance test (OGTT) was performed during stable condition before hospital discharge and interpreted according to WHO criteria. The mean follow-up period was 37.5 months. RESULTS: The incidence of GA was as follows: impaired fasting glycaemia - IFG (n = 376, 15%); impaired glucose tolerance - IGT (n = 560, 22%); DM (n = 425, 17%); new onset DM (n = 384, 15%); and normal glucose tolerance - NGT (n = 782, 31%). During the long-term follow-up, death rate events for previously known DM, new onset DM and IGT were significantly more frequent than those for IFG and NGT (12.3; 9.6 and 9.4 vs. 5.6 and 6.4%, respectively, P < 0.05). The strongest and common independent predictors of death in GA patients were glomerular filtration rate < 60 ml/min/1,73 m^2 (HR 2.0 and 2.8) and left ventricle ejection fraction < 35% (HR 2.5 and 1.8, all P < 0.05) respectively. CONCLUSIONS: Glucose abnormalities are very common in AMI patients. DM, new onset DM and IGT increase remote mortality. Impaired glucose tolerance bears similar long-term prognosis as diabetes.

Advanced glycation end product accumulation in the cardiomyocytes of heart failure patients with and without diabetes.

BACKGROUND: Non-enzymatic coupling of protein and lipid cellular structures with glucose leading to the formation of advanced glycation end products (AGE) plays a role in aging and the development of diabetic complications, but its contribution to myocardial pathology is unclear. We aimed to assess the role of heart failure on AGE formation in patients with or without diabetes mellitus type 2 (DM2). MATERIAL/METHODS: Heart tissue specimens from 136 patients undergoing transplantation were grouped as follows: 14 cases of ischemic cardiomyopathy (ICM) and DM2, 8 cases of dilated cardiomyopathy (DCM) and DM2, 67 cases of ICM without DM2, and 47 cases of DCM without DM2. Fourteen heart samples were from the autopsies of patients with DM2 without heart disease, and 20 heart samples were from organ donors in whom the heart was wasted. AGE deposits were localized immunohistochemically counted using a semiquantitative scale and characterized by their staining pattern. RESULTS: Positive staining was present in all samples from both cardiomyopathy groups with DM2, in 71% of healthy hearts from the DM2 subjects, in 51% of ICM non-diabetic hearts, and in 38% of DCM non-diabetic hearts, and in only 15% of the organ donors. Mixed-diffuse and granular AGE patterns were characteristic for DM2, while a diffuse pattern was more frequently observed in heart failure patients without diabetes. The semiquantitative results supported increased AGE accumulation in patients with DM2 and/or cardiomyopathy. CONCLUSIONS: The amount of AGE in cardiomyocytes increases significantly in both diabetes and heart failure, with a staining pattern typical for each condition.

Effect of cardiac resynchronization on gradient reduction in patients with obstructive hypertrophic cardiomyopathy: preliminary study.

BACKGROUND: The purpose of this study was to assess the effectiveness of cardiac resynchronization therapy (CRT) in terms of outflow tract gradient reduction and functional improvement in symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM) requiring implantable cardioverter-defibrillator (ICD) implantation. METHODS: Eleven consecutive symptomatic HOCM patients with a significant (≥40 mmHg) gradient and indications for ICD, but without indications for resynchronization, underwent CRT-D implantation. Nine of them (four female, median age of 50 years) in whom the procedure succeeded were screened for New York Heart Association (NYHA) class, outflow gradient, mechanical dyssynchrony, QRS-width change, and 6-minute walking distance (6MWD) and peak oxygen consumption (VO(2)peak) improvement after 6 months and remotely. RESULTS: After 6 months of pacing, NYHA class decreased (median 1 vs 2, respectively); peak (33 vs 84 mmHg) and mean (13 vs 38 mmHg) outflow tract gradients were reduced; and QRS width (143 vs 105 ms), intraventricular dyssynchrony (35 vs 55 ms), and VO(2)peak (19.5 vs 14.2 mL/kg/min) increased significantly (all P < 0.05) compared to baseline. In six of nine patients (67%), the peak gradient was reduced >50% and reached <40 mmHg. After a median of 36 months, the outflow gradient decreased even more (8 mmHg) and was significantly (P < 0.05) lower than after 6 months of CRT. CONCLUSIONS: These preliminary data suggest that CRT seems to be an effective method of reducing the outflow tract gradient and improving the functional status of symptomatic HOCM patients requiring ICD implantation. Our findings need to be confirmed by more extensive studies.

Motion synthesis and force distribution analysis for a biped robot.

In this paper, the method of generating biped robot motion using recorded human gait is presented. The recorded data were modified taking into account the velocity available for robot drives. Data includes only selected joint angles, therefore the missing values were obtained considering the dynamic postural stability of the robot, which means obtaining an adequate motion trajectory of the so-called Zero Moment Point (ZMT). Also, the method of determining the ground reaction forces' distribution during the biped robot's dynamic stable walk is described. The method was developed by the authors. Following the description of equations characterizing the dynamics of robot's motion, the values of the components of ground reaction forces were symbolically determined as well as the coordinates of the points of robot's feet contact with the ground. The theoretical considerations have been supported by computer simulation and animation of the robot's motion. This was done using Matlab/Simulink package and Simulink 3D Animation Toolbox, and it has proved the proposed method.

Advanced glycation end-products in myocardium-supported vessels: effects of heart failure and diabetes mellitus.

BACKGROUND: Disturbed glucose metabolism, particularly in diabetes, is an important but not the sole factor leading to advanced glycation end-product (AGE) formation. The AGE amount and its distribution in cardiopathic myocardial tissues in the presence or absence of diabetes are not well documented. The aim of this study was to assess AGE deposition in unaffected myocardial vessels in heart failure patients with and without diabetes mellitus type 2 (DM2) undergoing transplantation. METHODS: The following groups were established: 14 hearts harvested from subjects with ischemic cardiopathy and DM2; 8 hearts from subjects with dilated cardiopathy with DM2; 67 hearts from subjects with ischemic cardiopathy; 47 hearts from subjects with dilated cardiopathy; and 14 hearts from autopsy cases with diagnosed DM2. A control group consisted of 20 heart donors. AGE localization was determined immunohistochemically in tissue sections. A semi-quantitative scale was used to assess reaction intensity in arteries, arterioles, capillaries, venules and veins. RESULTS: Both types of cardiomyopathy increased AGE accumulation in intramyocardial veins more than in arteries. The presence of DM2 significantly increased AGE in arterioles and capillaries, especially when coexisting with cardiomyopathy. The type of cardiopathy did not influence the pattern of AGE accumulation in myocardial vessels. CONCLUSION: Both chronic heart failure and DM2 intensified AGE pathology and changed the susceptibility of myocardial vasculature to glycation. However, chronic heart failure increases AGE deposition mostly in veins, whereas DM2 predisposes arterioles to AGE accumulation.

Prognosis in diabetic patients with acute myocardial infarction treated invasively is related to renal function.

BACKGROUND: The prevalence of diabetes mellitus (DM) and chronic kidney disease (CKD) is rapidly increasing. Both comorbidities are considered significant risk factors for cardiovascular complications. The aim of the study was to evaluate the impact of DM with and without CKD on prognosis in patients with acute myocardial infarction (AMI) treated invasively. MATERIAL/METHODS: This single-center prospective study encompassed 3334 AMI-patients without cardiogenic shock, who were divided into 2 major groups: 999 patients with type 2 DM diagnosed prior to or during index hospitalization, and 2335 non-diabetics. All diabetic patients were divided with respect to their renal status into: diabetics with CKD (DM-CKD; n=264) and without (DM-nCKD; n=735). Short- and long-term outcomes were compared between study groups. Independent predictors of death and composite end-point were selected with multivariate Cox-regression model. RESULTS: Mortality rates were significantly higher in DM group compared to nDM in all observation periods. DM-CKD was associated with excessive total mortality (35.6%) when compared to DM-nCKD (11.6%, P<0.001) and to nDM (9.8%, P<0.001). Mortality and major adverse cardiovascular event rates did not differ significantly between DM-nCKD and nDM groups. Diabetes coexisting with CKD was one of the strongest independent risk factors for death (hazard ratio 1.93; confidence interval 1.79-2.07; P<0.001). CONCLUSIONS: The prognosis in diabetics with AMI is significantly related to renal function. Diabetics without CKD had similar prognosis to non-diabetics. Multivariate analyses showed that unlike diabetes without renal dysfunction, DM-CKD was an independent risk factor for cardiovascular complications and total mortality.

Power spectral density in balance assessment. Description of methodology.

One of the methods used in clinical setting to assess the balance function is the measurement of the centre of pressure trajectory (COP). The COP trajectory is strongly dependent on the body centre of mass trajectory (COM), but in case of balance problems the corrective signals influence this dependence. The aim of the present study is to explore the possibility of using power spectral density function of the COP vs. COM signal in assessing the amount of correction signals. As the aim was a methodological one, only one healthy adult subject participated in the study. This subject performed five balance tasks of increasing difficulty. The COP trajectory was recorded using the Kistler force plate, and COM trajectory was calculated based on the marker trajectories placed on the subject's body and simultaneously recorded with VICON 460 system. The COM data were subtracted from COP trajectory in anteroposterior (AP) and lateral direction. Next the power spectral density (PSD) was calculated for the new signals. The power spectral density is very low for easiest condition, but increases with the difficulty of task. Moreover, it also provides information in which plane (sagittal or frontal) more correction movements are needed to maintain stability.

Postural stability in symmetrical gaits.

In this paper the method of stability analysis of dynamic symmetrical gaits is discussed. The problem of dynamic postural equilibrium, taking into account the role of compliant feet, is solved. The equilibrium conditions are split between the foot attachment points and the points within the foot-end area. The present method is useful for motion synthesis, taking into account robot parameters. It also helps in the robot foot design. As an illustrative example a four-legged diagonal gait is considered. The theoretical results were verified by implementing and observing the diagonal gait in four-legged machine with and without feet.

Biological inspiration used for robots motion synthesis.

This work presents a biologically inspired method of gait generation. Bipedal gait pattern (for hip and knee joints) was taken into account giving the reference trajectories in a learning task. The four coupled oscillators were taught to generate the outputs similar to those in a human gait. After applying the correction functions the obtained generation method was validated using ZMP criterion. The formula suitable for real-time motion generation taking into account the positioning errors was also formulated. The small real robot prototype was tested to be able walk successfully following the elaborated motion pattern.

Triple-site versus standard cardiac resynchronization therapy study (TRUST CRT): clinical rationale, design, and implementation.

BACKGROUND: Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure (HF), lowered LV ejection fraction, and wide QRS. However, many patients (< or =40%) do not respond to this form of pacing. TRUST CRT is a prospective, single-center, randomized, single-blind, parallel, and controlled study that has been designed to treat patients with moderate to severe HF (NYHA III-IV), QRS > or =120 ms, sinus rhythm, LV dysfunction (EF < or = 35%), and signs of mechanical dyssynchrony. OBJECTIVE: The primary objective will evaluate the 6-month's combined endpoint of alive status, freedom from hospitalization for HF or heart transplantation, relative > or =10% increase in LV ejection fraction, > or =10% in peak oxygen consumption, and > or =10% in 6-minute walking distance. METHODS: Patients with HF receiving optimal pharmacotherapy, with LV dysfunction, mechanical dyssynchrony, wide QRS and sinus rhythm will be randomized in a 1: 1 fashion to standard or triple-site CRT-D. Patients will be followed for 1 week, 1, 3, and 6 months during a blind phase, then every 6 months until study completion. One hundred patients will be enrolled by the study center. CONCLUSIONS: TRUST CRT is a randomized, clinical trial in CRT candidates to evaluate the effectiveness of triple-site pacing versus standard resynchronization in patients with HF.

Mid-term outcomes of triple-site vs. conventional cardiac resynchronization therapy: a preliminary study.

BACKGROUND: The primary objectives of this study were to compare the implantation course of triple-site (double left-single right) and conventional cardiac resynchronization devices. The secondary target was to assess mid-term outcomes of both types of cardiac resynchronization therapy (CRT). METHODS: Fifty-four patients with NYHA classes III-IV, left ventricular EFor=120 ms were included; 27 received triple-site pacemakers (TRIV group), 27 conventional CRT devices (BIV group). Procedural course, clinical data, QRS duration, echocardiographic parameters, peak oxygen consumption (VO2max) and 6-minute walking distance (6MWD) were screened for inter-group differences. RESULTS: Procedure duration was higher in TRIV than in BIV group (197.6 vs. 137.6 min, P<0.001), fluoroscopy exposure and complication-rates were similar. After 3 months of CRT, triple-site pacing was associated with a more significant (P<0.05) NYHA class reduction (by 1.4 vs. 1.0 class, respectively), increase in VO(2) max (2.9 vs. 1.1 mL/kg/min) and 6MWD (98.7 vs. 51.6 m) than conventional CRT. A higher EF and more improved intraventricular synchrony were observed in the TRIV than in the BIV group. The response rate in the TRIV group was 96.3% vs. 62.9% in the conventional group (P=0.002). Triple-site stimulation was an independent predictor of response to CRT (adjusted odds ratio 26.4, P=0.01). CONCLUSIONS: Triple-site resynchronization appears to be more beneficial than conventional CRT. Upgrade to triple-site CRT may be considered in non-responders to standard resynchronization.

Triple-site biventricular pacing in patients undergoing cardiac resynchronization therapy: a feasibility study.

AIMS: To evaluate implantation safety and efficiency of triple-site (double left-single right) cardiac resynchronization therapy (CRT) and to assess the outcome of this procedure. METHODS AND RESULTS: Twenty-six patients with New York Heart Association (NYHA) class III-IV, left ventricular ejection fraction (EF) < or = 35%, and QRS > or = 120 ms underwent triple-site CRT. Procedural course and complications were analysed. NYHA class, QRS duration, echocardiographic parameters, peak oxygen consumption (VO(2)max), and 6 min walking distance (6MWD) were assessed at baseline and after 3 months. Responders were defined by survival, by no re-hospitalization for heart failure, and by >10% EF, VO(2)max, and 6MWD increase. Implantation was successful in 22 patients (84.6%). Procedure duration (199.1 min) and fluoroscopy time (38.7 min) were higher than in standard procedures. Two clinically silent coronary sinus dissections occurred intra-operatively; one phrenic nerve stimulation and one pocket infection were observed during follow-up. After 3 months of CRT, a significant reduction (P < 0.05) of NYHA class, increment of VO(2)max, 6MWD, EF, and improvement of indices of dyssynchrony were observed. Response rate in the studied group was 95.4%. CONCLUSION: Triple-site resynchronization appears to be a safe and efficient treatment method, with high response rate. Further studies are needed to evaluate the role of this pacing mode in CRT.

Influence of reciprocating tachycardia on the development of atrial fibrillation in patients with preexcitation syndrome.

BACKGROUND: We sought to evaluate the influence of atrio-ventricular reentrant tachycardia (AVRT) on atrial pressures during tachycardia and the presence of atrial fibrillation (AF) in patients with preexcitation syndrome. METHODS: The study population consisted of 88 patients (37 females, mean age 37.3 years) with left-sided accessory pathway and AVRT induced during electrophysiologic study. The AF-inducible group consisted of 32 patients with sustained episodes of AF provoked during electrophysiologic study, whereas the noninducible group comprised 56 patients without AF. RESULTS: We found significantly higher values of maximal and mean left (LAP) and right (RAP) atrial pressures in the AF group compared with noninducible group: LAP max 32.0 versus 20.8, LAP mean 21.6 versus 13.2, RAP max 15.2 versus 11.5, RAP mean 8.2 versus 6.2 respectively (P < 0.001). When analyzing the effect of AVRT on atrial pressures, we found a significant (P < 0.001) negative correlation between anterograde conduction times during tachycardia and LAP max and LAP mean in the whole population, but a significant positive correlation between retrograde conduction time and left atrial pressures. Similar effects of AVRT on the right atrial pressures were found. CONCLUSIONS: Atrial pressures during AVRT, which depend on the electrophysiological features of tachycardia, play an important role in the genesis of atrial fibrillation in patients with preexcitation syndrome.