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Effect of pressing time on physical and mechanical properties of phenolic-impregnated bamboo strips was evaluated. Bamboo strips (Gigantochloa scortechinii) were impregnated with low molecular weight phenol formaldehyde (LMwPF) resin. Samples were submerged in LMwPF resin using a vacuum chamber of 750 mmHg for 1 h before it was released within 1.5 h. Treated strips were dried in an oven with a temperature of 60 °C within 6–9 h. It was hot pressed at 14 kg m−2 and a temperature of 140 °C for 5, 8, 11, 14 and 17 min. The physical and mechanical properties of the test indicated that the properties of phenolic-treated strips have significantly increased as compared to control samples. Dimensional stability (water absorption, thickness swelling and linear expansion) of the phenolic-treated properties were significantly lower than control after 5-min pressing time. The antishrink efficiency (ASE) of phenolic-treated strips increased when pressing time were extended from 5 to 17 min. The mean value of modulus of rupture (MOR) for the control samples (177 N mm−2) showed a significant difference with phenolic-treated strips after 17-min pressing time (224 N mm−2). However, there is no significant difference in compression parallel to grain. The MOE of phenolic-treated strips was 21,777 N mm−2 and for control was 18,249 N mm−2, whereas the compression parallel to grain values for phenolic-treated and control samples were 94 and at 77 N mm−2, respectively.

Background Arrhythmias are reported during pregnancy, although hospitalization for these infrequent events is not fully characterized. The frequency and outcome of arrhythmias during pregnancy are unknown. Methods Between 1992 and 2000, there were 136,422 pregnancy-related admissions to Parkland Memorial Hospital (Dallas, TX, USA). Using the discharge diagnosis data bank and the International Classification of Disease, 9th revision, Clinical Modification (ICD-9-CM) coding system, we identified 226 admissions (218 patients) where cardiac arrhythmias and intrauterine pregnancy were both reported. Results The most common rhythm disturbances during pregnancy were sinus tachycardia (ST), sinus bradycardia (SB), or sinus arrhythmia (SA) (104 episodes/100,000 pregnancies). This was followed by paroxysmal supraventricular tachycardia (PSVT) and premature beats, with a frequency of 24/100,000 and 33/100,000, respectively. Paroxysmal supraventricular tachycardia occurred most frequently in the third trimester or peripartum. All episodes terminated spontaneously or were safely terminated with medical therapy. Advanced heart block or lethal arrhythmias were exceedingly rare during pregnancy. Conclusion Most frequently reported cardiac arrhythmias in pregnancy are benign and do not require intervention. Supraventricular tachycardia (SVT), being one of the most common complicated cardiac arrhythmias during pregnancy, can be treated effectively and safely with standard medical therapy. Ventricular arrhythmias or high-degree atrioventricular block (AVB) during pregnancy are extremely rare. Cardiac arrest is also rare, and is often caused by a different etiology from the conventional ones for sudden cardiac death. Copyright © 2008 Wiley Periodicals, Inc.

Introduction: Several noninvasive measures of cardiac risk such as heart rate variability (HRV) cannot be used in patients with atrial fibrillation (AF). One promising exception is the measure of ventricular cycle length entropy (VCLE) where initial data suggest that a reduction in VCLE portends an increased risk of cardiac death in patients with chronic AF. In this study, we hypothesized that measures of short-term HRV during sinus rhythm would correlate with measures of cycle length entropy during paroxysms of AF. Methods: We tested 25 Holter recordings of paroxysmal AF from the Physionet AF Prediction Database. We calculated HRV parameters including standard deviation of all NN intervals (SDNN), the root mean square root of the differences between adjacent NN intervals (RMSSD), standard deviation of 5-minute averages of NN intervals (SDANN), percentage of adjacent NN interval differences >50 ms (pNN50), and interbeat correlation coefficient (ICC) from 30 minutes of normal sinus rhythm, and entropy measures (the Shannon Informational Entropy [ShEn] and Average of Approximate Entropy [ApEn]) from 5 minutes of AF that occurred during the same 24-hour monitor. Pairwise correlations were used to assess associations, as regression residuals were normally distributed. Results: The mean entropy measures during AF were: ShEn: 4.78 ± 0.82, ApEn: 0.198 ± 0.21. When assessed during the 30 minutes immediately preceding AF onset, ICC showed a significant negative correlation with both ShEn (r =–0.65, P < 0.001) and ApEn (r =–0.60, P < 0.01). RMSSD also correlated with both ShEn (r = 0.41, P = 0.04) and ApEn (r = 0.39, P = 0.05), but other HRV measures showed no correlation with VCLE during AF. Conclusion: Reductions in RMSSD or increases in ICC, two short-term HRV measures that are known to reflect parasympathetic function in sinus rhythm, are correlated with reductions in the entropy of ventricular response intervals during AF. Our findings suggest that entropy during AF may be modulated, in part, by vagal innervation.

This is the second case report in literature that describes the simultaneous acoustic cardiographic, electrocardiographic, and invasive hemodynamic events that occurred before, during and after ventricular fibrillation that was successfully cardioverted to sinus rhythm. The absence of heart sounds, which are linked to the lack of effective myocardial contractility, correlated well with invasive hemodynamic data, indicating the lack of perfusion during ventricular fibrillation. These observations, coupled with the challenges of pulse detection as a sign of adequate perfusion during resuscitation suggest that acoustic cardiography may be a potentially effective supplemental diagnostic tool during the resuscitation of malignant arrhythmias.

Although modest elevations in pacing rate improve cardiac output and induce reflex sympathoinhibition, the threshold rate above which hemodynamic perturbations induce reflex sympathoexcitation remains unknown. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressures (MAP) and sympathetic nerve activity (SNA) were measured during normal sinus rhythm (NSR) and atrioventricular (AV) sequential pacing in 25 patients. Pacing was performed at 100, 120, and 140 beats/min with an AV interval of 100 ms. Patients were divided into two groups based on normal or abnormal left ventricular ejection fraction (LVEF): group 1 ( n = 11; mean LVEF, 55%) and group 2 ( n = 14; mean LVEF, 31%). In group 1, relative to NSR, SBP decreased an average of 2%, 3%, and 8% at 100, 120, and 140 beats/min ( P < 0.001), respectively. DBP and MAP increased 9%, 15%, and 15% ( P = 0.001) and 3%, 6%, and 5% [ P = not significant (NS)], respectively. In group 2, SBP reductions were even greater, with an average decrease of 4%, 8%, and 16% ( P < 0.001). Whereas DBP increased 9%, 9%, and 8% at 100, 120, and 140 beats/min ( P = NS), MAP increased 3% and 2% at 100 and 120 beats/min but decreased 3% at 140 beats/min ( P = 0.001). SNA recordings were obtained in 11 patients (6 in group 1 and 5 in group 2). In group 1, SNA decreased during all rates, with a mean 21% reduction. In group 2, however, SNA decreased at 100 and 120 beats/min (49% and 38%) but increased 24% at 140 beats/min. Patients with depressed LVEF exhibited altered hemodynamic and sympathetic responses to rapid sequential pacing. The implications of these findings in device programming and arrhythmia rate control await future studies.

In this study influence of outdoor exposure on surface quality of five Malaysian species, Merbau ( Intsia palembanica ), dark red meranti ( Shorea spp.), balau ( Shorea spp.) keranji ( Dialium spp.), and keruing ( Dipterocarpus spp.) were evaluated. Surface roughness of the samples exposed to outdoor environment ranging from 1 week to 4 weeks were determined using a stylus type equipment. Three roughness parameters average roughness ( R a ), mean peak-to-valley height ( R z ), and maximum roughness ( R max ) calculated from the surface profiles of the samples employing a profilometer were used for the analyses. Control samples of keranji had the smoothest surface with an average R a value of 3.90 μm while keruing had the roughest surface with 8.20 μm among five species. None of the samples from five different species resulted in significant differences in roughness values within 1-week interval during the outdoor exposure at 95% confidence level. Roughness measurements taken from the surface of control samples and samples exposed for 4-week outdoor from belau, keruing, and dark red meranti showed significant difference at 95% confidence level. These differences were not significant in the case of merbau and keranji. Based on the findings from this study it appears that stylus method can be used to evaluate surface quality of various tropical species as function of outdoor exposure.

In this work, we analyze the behavior of the particle phase in the flow of a particle-laden mixture through a porous medium. An attempt is made to model the diffusion and dispersion processes, and to quantify the deviation terms that arise when intrinsic volume averaging is used to derive the flow equations.

Background Studies have suggested that patients with atrial fibrillation ( AF ) have impairment in the baroreflex. It is not clear whether these findings are the result of the associated comorbid conditions or the arrhythmia itself. We hypothesized that AF is associated with impairment in baroreflex function and that the arrhythmia itself is a contributing factor. Methods and Results Twenty‐four patients with persistent AF referred for cardioversion were enrolled. A second group of patients with no history of AF matched for age and left ventricular ejection fraction was identified and served as the control group. In the AF group, baroreflex gain ( BRG ) was measured on the day of cardioversion (Day 1) and again at 30 days post‐cardioversion (Day 30) in patients who remained in sinus rhythm ( SR ). The clinical characteristics of patients with AF were not different than those of the control group. The mean BRG in the AF group on Day 1 was significantly lower than the mean BRG of the control group (5.2±3.6 versus 10.8±5.5 ms/mm Hg, P AF recurrence before the 30‐day follow‐up and 14 patients remained in SR . In the group that remained in SR , BRG increased from 4.1±3.7 ms/mm Hg on Day 1 to 7.0±6.0 ms/mm Hg on Day 30 ( P Conclusion We have shown that AF is associated with impairment of the baroreflex and that restoration of SR improves BRG . Our data suggest that AF might be a contributing factor to the observed impairment in BRG and that restoring SR might help improve baroreflex function.

The purpose of this study was to better understand the role of the baroreflex in tilt-induced vasovagal syncope (VVS).The role of the baroreflex in tilt-induced VVS remains controversial. The authors hypothesized that: 1) patients with positive tilt table test (TTT) results have greater baroreflex gain (BRG) compared with patients with negative TTT results; and 2) patients with tilt-induced asystole have greater BRG compared with patients without asystole.Using the sequence method, BRG measurements were obtained in 438 consecutive patients undergoing TTT. Two hundred sixty-eight patients (61%) had positive TTT results (mean age 50 ± 21 years; 34% men), and 170 patients (39%) had negative TTT results (mean age 48 ± 21 years; 35% men).Mean BRG was significantly higher in patients with positive TTT results compared with those with negative TTT results (12.9 ± 6.0 ms/mm Hg vs. 11.5 ± 6.0 ms/mm Hg; p = 0.01). Among the 268 patients with positive TTT results, 23 (9%) had more than 3 s of asystole (mean age 37 ± 17; 30% men), and 245 patients had a mixed vasodepressor or cardioinhibitory response without asystole (mean age 51 ± 17 years; 34% men). Mean BRG was greater in patients with tilt-induced asystole (3 s) compared with patients without asystole (15.3 ± 5.9 ms/mm Hg vs. 12.7 ± 5.9 ms/mm Hg; p = 0.03).The results of this study demonstrate that baseline BRG was higher in patients with positive TTT results compared with those with negative TTT results, with greater values noted in patients with tilt-induced asystole (3 s) compared with those without asystole.

The failure characteristics of bamboo Gigantochloa scortechinii caused by the effect of artificial compressive stress at 50%, 80% and maximum loading were discussed. The failure characteristics of fibre cell wall damaged by compression test was analysed and related to the anatomical structure of bamboo. This study consisted of microscopic examination on bamboo fibre obtained by sectioning and maceration and observed using Polarised Light Microscopy and Scanning Electron Micrograph (SEM).The results indicate that failure mode in bamboo from compression load parallel to the grain are mainly slip planes observed at different parts of the cell walls. Macroscopic failure was observed mainly after the samples were tested to maximum load. In the 50% samples, very little slip planes were seen while more frequent slip planes were observed from the 80% samples. The difference in slip plane angle measured and number of observations made from different stress loadings could be related to the anisotropic and p...

An experiment was conducted to study the effect of grafting on yield, quality and shelf life of tomato using simplified open soilless system vs. conventional soil cultivation. The experiment was carried out at Al-Karama station which represents areas north of the Dead Sea where soil salinity is the limiting factor for higher yields. Cecilia F1 cv. (most commercial tomato cultivar grown in Jordan) grafted on two rootstocks (He-man and Spirit) was compared with non-grafted Cecilia (control) plants in both simplified open soilless system (containers filled with volcanic tuff) and conventional soil cultivation. Uniform 45 days-old seedlings of grafted and nongrafted Cecilia were transplanted in two 500m 2 uncontrolled plastic houses on Nov. 4, 2004, irrigated with nutrient solution after taking into consideration nutrients available in irrigation water. Fruits were harvested at full mature stage to determine fruit yield, number of fruits per plant and fruit weight. Random fruit samples from cluster 3 and 5 were used to determine fruit outer and inner quality and shelf life. The results showed that fruit yield was improved by grafting in both growing systems. Fruit yield increased by 12-27% in soilless cultivation and by 16-38% in soil cultivation with grafting Cecilia on He-Man and Spirit, respectively. Fruit quality in terms of total soluble solids, antioxidant capacities, vitamin C, lycopene and βcarotene content were reduced or slightly improved by grafting in both growing systems. However, fruit size and shelf life were not affected and fruit firmness improved by grafting but these parameters were improved in soilless as compared with soil cultivation. This variations in our results between soilless and soil cultivation and the behavior of the rootstocks might due to the fact that plants grown in soilless culture were not under salt stress as compared with those grown in soil. The result also showed that using simplified open soilless system improved productivity and fruit quality in terms of fruit size, shelf life and firmness. However, more studies needed o determine the effect of grafting on inner quality of tomato fruit.

We have recently shown that atrial fibrillation is associated with an increase in sympathetic nerve activity (SNA) compared with sinus rhythm. It remains unclear, however, whether these findings are true at various rates and whether the magnitude of sympathoexcitation is related to the degree of irregularity.To determine the role of irregularity in mediating the SNA changes at various pacing rates. Univariate analysis showed that as the irregularity increased, SBP increased (r = 0.44, P.001) but that MAP and DBP did not change significantly.Using custom-made software, atrioventricular sequential pacing with predetermined rates (100, 120, and 140 bpm) and irregularities (standard deviation = 0%, 5%, 15%, and 25% of mean cycle length) was performed in 23 patients referred for electrophysiologic evaluation. Pacing at each rate/irregularity was performed for 2 minutes, with 2 minutes of recovery in between. Systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP), central venous pressure (CVP), and SNA were measured at baseline and during pacing.Univariate analysis showed that as the irregularity increased, SBP increased (r = 0.44, P.001 but that MAP and DBP did not change significantly. A significant correlation was found between the pacing irregularity and SNA, with greater sympathoexcitation noted at greater degrees of irregularity (r = 0.2, P = .04). A five-variable linear model using DBP, MAP, CVP, and degree of pacing irregularity to predict SNA was highly statistically significant (r = 0.46, P.001). After controlling for hemodynamic changes, for every 1% increase in irregularity, there was a 6.1% increase in SNA.We have shown that greater degrees of irregularity cause greater sympathoexcitation and that the effects of irregular pacing on SNA are independent of the hemodynamic changes.

Atrial fibrillation (AF) and congestive heart failure (CHF) affect millions of patients in the United States. Several studies suggest that AF and in particular the irregular ventricular response might be contributing to the left ventricular dysfunction. Studies that compared pharmacologic rate control to atrioventricular junction (AVJ) ablation followed by right ventricular pacing which restores a regular ventricular response, failed to show an improvement when compared to pharmacological rare control. These results might be explained by the fact that while AVJ ablation restored a regular ventricular response, it subjected patients to the detrimental effects of RV apical pacing. The AVERT-AF trial (Atrio-VEntricular Junction Ablation Followed by Resynchronization Therapy in patients with CHF and AF) is a prospective, randomized, double-blinded, multicenter trial that will be testing the hypothesis that AVJ ablation followed by biventricular pacing significantly improves exercise capacity and functional status compared to pharmacologic rate control in patients with chronic AF and depressed ejection fraction, regardless of rate or QRS duration. A total of 180 patients will be enrolled to test the primary endpoint, which is exercise duration. Patients_enrollment will begin in summer 2006 and is expected to be completed in 2008. The results of this trial should help define the best treatment option for this common arrhythmia in patients with left ventricular dysfunction.

The purpose of this manuscript is to review the current literature regarding the role of the autonomic nervous system (ANS) in atrial fibrillation (AF). We will be reviewing its effect on initiation, maintenance, and termination of AF, with emphasis on the role of baroreflex gain (BRG) and autonomic reflexes in the maintenance of this arrhythmia. While it is generally accepted that the ANS plays an important role in AF, the extent of that role remains controversial. Much of the controversy could be explained by the time frame during which the autonomic measurements were made, the differences in patient population, and possibly the differential effect of the autonomic changes on the trigger versus the substrate. While vagal stimulation results in shortening of the atrial effective refractory period and increased dispersion of refractoriness, its effect on the "trigger" might be antiarrhythmic. During AF, cardiac filling pressure increases while arterial blood pressure decreases sending conflicting messages to the medulla. The acute effect is an increase in sympathetic activity to ensure adequate hemodynamic stability. On the other hand, the long-term effects might be impairment in the cardiopulmonary BRG and changes that accentuate the presence of AF. While radiofrequency ablation has provided us with a unique insight into the role of possible denervation in AF suppression, the exact mechanisms involved are far from being completely understood. Today, in an era where great technological advances have occurred, our need to understand the role of the ANS in AF is greater than ever.

La oxigenoterapia hiperbárica (OHB) es una modalidad de terapéutica física que se fundamenta en la obtención de presiones parciales de oxígeno elevadas, al respirar oxígeno puro en el interior de una cámara a una presión superior a la atmosférica. El objetivo de esta revisión es clarificar los mecanismos de acción y los efectos de esta terapéutica física, los problemas que puede plantear y sobre todo las indicaciones actuales. En cirugía oral y maxilofacial, la OHB se utiliza como tratamiento complementario en procesos de osteítis y osteomielitis maxilo-mandibular, en infecciones necrotizantes de partes blandas (a nivel cervical, periodontal, gingival,…), en la prevención (muy importante) y el tratamiento de la osteradionecrosis, en los retrasos de cicatrización (de fracturas, de implantes dentales, de injertos/colgajos de difícil viabilidad), en la rehabilitación implantológica de pacientes oncológicos irradiados. Es preciso utilizar los protocolos establecidos y generar estudios que sostengan científicamente su utilización; de este modo se podría paliar la poca consistencia de los estudios publicados que hemos encontrado.Hyperbaric oxygen therapy (HBO) is a physical therapeutic modality based on obtaining high partial pressures of oxygen, on breathing pure oxygen inside a chamber at a pressure that is greater than that of the atmosphere. The object of this revision is to clarify the action mechanisms and the effects of the physical therapy, the problems that may arise and more especially the current indications for its use. In oral and maxillofacial surgery, HBO is used as complementary treatment for maxillo-mandibular osteitis and osteomyelitis, for necrotizing infections of soft tissue (on a cervical, periodontal, gingival... level), for the prevention (very important) and treatment of osteoradionecrosis, for healing delays (fractures, dental implants, grafts/flaps with difficult viability), for implantological rehabilitation of irradiated oncological patients. It is necessary to use the protocols that have been established and to generate studies that scientifically support its use; in this sense the lack of consistency that we have found is the studies that have been published could be reduced.

BACKGROUND Chronic right ventricular pacing has been reported to promote cardiac dyssynchrony. The PAVE trial prospectively compared chronic biventricular pacing to right ventricular pacing in patients undergoing ablation of the AV node for management of atrial fibrillation with rapid ventricular rates. METHODS AND RESULTS One hundred and eighty-four patients requiring AV node ablation were randomized to receive a biventricular pacing system (n = 103) or a right ventricular pacing system (n = 81). The study endpoints were change in the 6-minute hallway walk test, quality of life, and left ventricular ejection fraction. Patient characteristics were similar (64% male; age: 69 +/- 10 years, ejection fraction: 0.46 +/- 0.16; 83%, NYHA Class II or III). At 6 months postablation, patients treated with cardiac resynchronization had a significant improvement in 6-minute walk distance, (31%) above baseline (82.9 +/- 94.7 m), compared to patients receiving right ventricular pacing, (24%) above baseline (61.2 +/- 90.0 m) (P = 0.04). There were no significant differences in the quality-of-life parameters. At 6 months postablation, the ejection fraction in the biventricular group (0.46 +/- 0.13) was significantly greater in comparison to patients receiving right ventricular pacing (0.41 +/- 0.13, P = 0.03). Patients with an ejection fraction

Background— Although the hemodynamic changes associated with atrial fibrillation (AF) have been extensively studied, the neural changes remain unclear. We hypothesized that AF is associated with an increase in sympathetic nerve activity (SNA) and that the irregular ventricular response contributes to this state of sympathoexcitation. Methods and Results— In 8 patients referred for an electrophysiological study, SNA, blood pressure (BP), central venous pressure (CVP), and heart rate were recorded during 3 minutes of normal sinus rhythm (NSR) and 3 minutes of induced AF. In 5 of 8 patients who converted to NSR, right atrial (RA) pacing was performed for 3 minutes in atrial pacing triggered by ventricular sensing mode triggered by playback of an FM tape previously recorded from the right ventricle during AF (RA-irregular) and atrial pacing inhibited by atrial sensing mode at a rate equal to the mean heart rate obtained during AF (RA-regular). SNA data were expressed as percentage of baseline during NSR. SNA increased in all 8 patients during induced AF compared with NSR (171±40% versus 100%, respectively; P P =0.02). Similarly, SNA was significantly higher during RA-irregular pacing compared with RA-regular pacing (124±24% versus 91±20%, respectively; P =0.03). BP and CVP were not significantly different between the 2 pacing modes. Conclusions— Induced AF results in a significant increase in SNA, which is in part attributable to the irregular ventricular response. Our findings suggest that restoring NSR or regularity might be beneficial, particularly in patients with heart failure.

Background— The purpose of this study was to assess the effect of the serotonin reuptake inhibitor paroxetine hydrochloride (Paxil, SmithKline Beecham) on cardiovascular reflexes. We hypothesized that Paxil prevents neurally mediated syncope (NMS) by attenuating the sympathoinhibition and vagotonia associated with a vasovagal reaction. Methods and Results— In a double-blind randomized study, 25 healthy subjects with a positive response to either carotid sinus massage (CSM) or lower body negative pressure (LBNP) received Paxil (20 mg/d) or placebo for 6 weeks. Arterial baroreflex sensitivity (BRS), muscle sympathetic nerve activity (SNA), baroreflex control of SNA, blood pressure, and heart rate responses to CSM and LBNP were measured at baseline and at 6 weeks. Nineteen subjects completed the study (Paxil, n=9; placebo, n=10). In the Paxil group, BRS decreased significantly compared with baseline (15.8±4.0 ms/mm Hg versus 11.0±2.6 ms/mm Hg, P =0.05); however, all 9 subjects continued to have a positive response to LBNP with presyncope. Paxil did not attenuate the sympathoinhibition or vagotonia associated with a positive LBNP response and had no significant effect on baroreflex control of SNA. In the control group, no significant change in BRS was noted compared with baseline. Seven out of 9 subjects who had a positive LBNP response at baseline had a repeat positive LBNP response, and the subject with a positive CSM at baseline had a negative response at 6 weeks. Conclusions— Paxil decreases arterial BRS but does not prevent the presyncope associated with LBNP. The effect of Paxil on the autonomic reflexes in patients with neurally mediated syncope remains unclear.

This study assesses the effect of biventricular pacing on sympathetic nerve activity (SNA) in patients with depressed ejection fraction and intraventricular conduction delay (IVCD). Biventricular pacing has been shown to result in hemodynamic improvement in patients with depressed ejection fraction and IVCD. The effect of biventricular pacing on SNA, however, remains unclear. A total of 15 men with a mean ejection fraction of 25 +/- 4% were enrolled. Arterial pressure, central venous pressure and SNA were recorded during 3 minutes of right atrial (RA) pacing and RA-biventricular pacing. Pacing was performed at a rate 5 to 10 beats faster than sinus rhythm, with an atrioventricular interval equal to 100 ms during RA-biventricular pacing. RA-biventricular pacing resulted in greater arterial pressures (p0.05) than RA pacing (146 +/- 15/83 +/- 11 vs 141 +/- 15/80 +/- 10 mm Hg). There were no differences in central venous pressures between the 2 pacing modes (p = 0.76). SNA was significantly less during RA-biventricular pacing (727 +/- 242 U) than during RA pacing (833 +/- 332 U) (p0.02). Furthermore, there was a positive correlation between baseline QRS duration and the decrease in SNA noted with RA-biventricular pacing (r = 0.58, p = 0.03). Biventricular pacing results in improved hemodynamics and a decrease in SNA compared with intrinsic conduction in patients with left ventricular dysfunction and IVCD. If the current findings are also present with chronic biventricular pacing, then this form of therapy may have a positive impact on mortality.

Focal junctional tachycardia (FJT) is characterized by a rapid often irregular narrow complex tachycardia with episodes of atrioventricular (AV) dissociation. This uncommon arrhythmia is most likely due to abnormal automaticity or triggered activity. The patients are often quite symptomatic and if left untreated may develop heart failure particularly if their tachycardia is incessant. In patients refractory to medical management, the role of radiofrequency ablation involves either (1) selective ablation of the tachycardia focus while preserving AV conduction or as a last resort (2) AV junction ablation followed by pacemaker implantation. The clinician should first assess whether ventriculoatrial (VA) conduction is present or absent during tachycardia. If present, radiofrequency ablation should be applied at the site of earliest retrograde atrial activation. In the absence of VA conduction and hence an atrial target site, sequential lesions should be applied in the posterior septum (slow pathway region) followed by lesions applied in midseptum and anteroseptum respectively if tachycardia persists. To further minimize the risk of AV nodal block, some authors delivered radiofrequency energy during atrial overdrive pacing to assess AV conduction during ablation. Others recommended mapping the perinodal region and applying radiofrequency ablation at the site where catheter manipulation resulted in tachycardia termination. Using this ablative approach, the risk of AV block is around 5-10%.

Despite significant progress in the past three decades including the publication of guidelines, the development of several emergency room syncope decision rules and more generic risk scores, and the institution of formal dedicated syncope facilities, the management (diagnosis and therapy) of syncope is still largely unsatisfactory. A Position Paper commissioned by the Canadian Cardiovascular Society1 addresses the quality of evidence of the standardized methods of management of syncope proposed in recent years and gave pragmatic interpretation of strong vs. weak recommendations based on the GRADE system.2 In brief, there is little persuasive evidence that emergency room syncope rules and diagnostic syncope units provide efficient care and improved outcomes. While we congratulate the Canadian colleagues for their objective comprehensive evaluation, we think their conclusions reflect some major pitfalls that persist in the approach to patients with syncope: 1. Difficulty identifying patients at high risk (in particular those at short-term risk). This problem inevitably leads to an increase in the number of inappropriate hospitalizations, tests utilization, and eventually higher costs. 2. High rate of unexplained diagnosis. It seems that the most complex (i.e. with competing possible causes) and potentially severe syncope cases that require specialized treatment remain undiagnosed.3 Indeed, patients with unexplained syncope tend to be older and more frequently have structural heart disease or electrocardiographic abnormalities. Conversely, a diagnosis is more easily obtained in healthy young patients without structural heart disease, who are known to have a favourable outcome. The paradox is that the more we need a precise diagnosis, the more difficult it is to obtain one. 3. High rate of misdiagnosis. Typically patients are asymptomatic at the time of evaluation and the opportunity to capture a …

This study is to develop a dynamic prediction tool for daily operation quality control in PETRONAS Kertih's refinery using Design for Six Sigma (DFSS) methodology. Catalytic reforming process was selected as the case study background where the relationship of operation parameters which influences the coke content deposited on the process catalyst was studied. The prediction model allows future estimation of the coke content on the catalyst and in turn assist in reducing future downtime of the unit which might cause RM20,000 per day of PONC (Price of Non Conformance). The related input-output operation data were obtained from the plant and 10 process operation parameters were categorized as key process input variables. Using Response Surface Methodology, dynamic modeling of the coke content was developed for prediction and analysis of the relationship between the coke content and the 10 process inputs. The prediction model passed the 2-sample 2-T Test, hence the prediction model was reliable where there was no statistically difference between the mean in actual and the predicted values.

Background: Atrial fibrillation (AF) is highly prevalent and poses a significant public health burden on the aging population. We hypothesized that AF independently predicts myocardial infarction (MI) in the Cardiovascular Health Study (CHS). Methods: AF was evaluated longitudinally in participants free of cardiovascular disease at baseline in the CHS. Participants were followed for a mean (standard deviation, SD) 12.7 (5.8) years for development of fatal or nonfatal MI. Cox regression models were utilized to assess the associations of time-updated AF and MI in fully adjusted models and models with gender interaction. Results: Of the 5888 participants in the CHS, 4158 met the inclusion criteria. The mean (SD) age was 72.3 (5.4) years old (38.3% male, 14.3% African-American). Eighty-two had prevalent AF; 1005 developed incident AF during follow up (AF group, n=1087). To avoid bias, participants diagnosed with AF at the same time as their MI were not included in the AF group. Baseline total cholesterol (212.4 [38.6] mg/dL), systolic blood pressure (SBP, 136.1 [21.4] mmHg), and diabetes mellitus prevalence (13.6%) were similar between groups. AF updated as a time-varying exposure was associated with a higher risk of MI: hazard ratio (HR) 1.61, [95% CI 1.32-1.96], after adjusting for age, gender, race, SBP, total and high-density lipoprotein cholesterol, current smoking, fasting glucose, education, alcohol use, C-reactive protein, body-mass index, diabetes, anti-arrhythmic use, and time-updated use of aspirin, anti-hypertensive and lipid medications. Women were at higher risk (HR 2.00 [95% CI 1.53-2.62]) than men (HR 1.33 [95% CI 0.99-1.77]) (p for interaction=0.02). Conclusion: In a large cohort study with over a decade of follow-up, AF was associated with an increased risk for MI. This association was more pronounced in women.

The purpose of this study was to assess the relationship between changes in sinus node cycle length (SNCL) during ventricular fibrillation (VF) and the peripheral changes in blood pressure (BP) and sympathetic nerve activity (SNA) in human subjects. We hypothesized that patients with no SNCL shortening during VF have a vasovagal-like response with a greater decrease in BP and SNA when compared to patients with SNCL shortening.SNCL, BP, and SNA recordings were attempted in 24 patients undergoing the implantation of a dual-chamber implantable defibrillator. Changes were measured during the first 5 seconds of VF and compared with the 5 seconds prior to VF induction.SNCL shortened during VF in nine patients (mean%∆SNCL = -12 ± 8%) and remained unchanged or lengthened in seven patients (mean%∆SNCL = 7 ± 7%). Eight patients had ventriculoatrial (VA) conduction prohibiting assessment of SNCL changes. In patients with SNCL shortening, the %∆MBP (mean BP) was -47 ± 6% compared to -58 ± 8% in patients with no SNCL shortening (P0.01). In patients with VA conduction, the %∆MBP was -54 ± 3%. SNA recordings were successfully obtained in four patients. When compared to baseline, SNA increased by 34 ± 30% in two patients with SNCL shortening, decreased by 25% in one patient with SNCL lengthening, and by 90% in the fourth patient with VA conduction.We have shown that patients with no SNCL shortening have a significantly greater decrease in MBP during VF when compared to patients with SNCL shortening. The underlying mechanism appears to be reflex mediated with a vasovagal-like response in patients with no SNCL shortening.

Hypoxia plays a significant role in tumor progression and aggressiveness and implicated in resistance to radiotherapy and chemotherapy. This study aims to characterize the changes in gene expression associated with chronic hypoxia in MCF7 breast cancer cell line and identify a possible biomarker for hypoxia in breast cancer. Breast cancer cells (MCF7) were exposed to 8-hour hypoxic episodes (

Background —The purpose of our study was to define the incidence and mechanisms of atypical right atrial flutter. Methods and Results —A total of 28 (8%) of 372 consecutive patients with atrial flutter (AFL) had 36 episodes of sustained atypical right AFL. Among 24 (67%) of 36 episodes of lower loop reentry (LLR), 13 (54%) of 24 episodes had early breakthrough at the lower lateral tricuspid annulus, whereas 11 (46%) of 24 episodes had early breakthrough at the high lateral tricuspid annulus, and 9 (38%) of 24 episodes showed multiple annular breaks. Bidirectional isthmus block resulted in elimination of LLR. A pattern of posterior breakthrough from the eustachian ridge to the septum was observed in 4 (14%) of 28 patients. Upper loop reentry was observed in 8 (22%) of 36 episodes and was defined as showing a clockwise orientation with early annular break and wave-front collision over the isthmus. Two patients had atypical right AFL around low voltage areas (“scars”) in the posterolateral right atrium. Conclusions —Atypical right AFL is most commonly associated with an isthmus-dependent mechanism (ie, LLR or subeustachian isthmus breaks). Non–isthmus-dependent circuits include upper loop reentry or scar-related circuits.

Background —Previous studies have shown the importance of the timing of atrial and ventricular systole on the hemodynamic response during supraventricular tachycardia (SVT). However, the reflex changes in autonomic tone during SVT remain poorly understood. Methods and Results —Eleven patients with permanent dual-chamber pacemakers were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and peripheral muscle sympathetic nerve activity (SNA) were recorded during DDD pacing at a rate of 175 bpm (cycle length 343 ms) with an atrioventricular (AV) interval of 30, 200 and 110 ms, simulating tachycardia with near-simultaneous atrial and ventricular systole, short-RP tachycardia (RPPR). Each pacing run was performed for 3 minutes separated by a 5-minute recovery period. All patients demonstrated an abrupt fall in BP, an increase in CVP, and an increase in SNA regardless of the AV interval. The decreases in SBP, DBP, and MAP and the increase in CVP were significantly less during long-RP tachycardia (AV interval 110 ms) than during the other 2 pacing modes ( P P Conclusions —These data suggest that the superior maintenance of hemodynamic stability during long-RP tachycardia is accompanied by reduced sympathoexcitation, which is primarily mediated by the arterial baroreceptors, with a modest cardiopulmonary vasodepressor effect.

Passengers who have ventricular fibrillation aboard commercial aircraft rarely survive, owing to the delay in obtaining emergency care and defibrillation.In 1997, a major U.S. airline began equipping its aircraft with automated external defibrillators. Flight attendants were trained in the use of the defibrillator and applied the device when passengers had a lack of consciousness, pulse, or respiration. The automated external defibrillator was also used as a monitor for other medical emergencies, generally at the direction of a passenger who was a physician. The electrocardiogram that was obtained during each use of the device was analyzed by two arrhythmia specialists for appropriateness of use. We analyzed data on all 200 instances in which the defibrillators were used between June 1, 1997, and July 15, 1999.Automated external defibrillators were used for 200 patients (191 on the aircraft and 9 in the terminal), including 99 with documented loss of consciousness. Electrocardiographic data were available for 185 patients. The administration of shock was advised in all 14 patients who had electrocardiographically documented ventricular fibrillation, and no shock was advised in the remaining patients (sensitivity and specificity of the defibrillator in identifying ventricular fibrillation, 100 percent). The first shock successfully defibrillated the heart in 13 patients (defibrillation was withheld in 1 case at the family's request). The rate of survival to discharge from the hospital after shock with the automated external defibrillator was 40 percent. A total of 36 patients either died or were resuscitated after cardiac arrest. No complications arose from use of the automated external defibrillator as a monitor in conscious passengers.The use of the automated external defibrillator aboard commercial aircraft is effective, with an excellent rate of survival to discharge from the hospital after conversion of ventricular fibrillation. There are not likely to be complications when the device is used as a monitor in the absence of ventricular fibrillation.

The development of ventricular arrhythmias is often a consequence of the interaction between structural abnormalities of the heart and transient disturbances in the electrophysiologic milieu. The critically ill patient is particularly susceptible to arrhythmias given the metabolic, ischemic, and neurohormonal stressors present in the intensive care unit. The significance of ventricular arrhythmias in the acute care setting is related to the presence of reversible causes and the extent of underlying heart disease. Long-term management of these patients is guided by an assessment of the risk for recurrent arrhythmias and the degree of left ventricular systolic dysfunction. In the absence of a reversible cause, symptomatic sustained arrhythmias are usually treated with an implantable cardioverter-defibrillator, a therapy that improves survival in this patient population. In many cases, however, proper long-term management of patients with ventricular arrhythmias is less clear, and the approach must be guided by a thorough understanding of the pathophysiology and the fundamental mechanisms of arrhythmogenesis.

OBJECTIVESThe aim of this study was to determine the changes in sympathetic nerve activity (SNA) after atrioventricular junction (AVJ) ablation in patients with chronic atrial fibrillation (AF).BACKGROUNDPolymorphic ventricular tachycardia (PMVT) has been reported after AVJ ablation in patients paced at a rate of ≤70 beats/min. We hypothesized that AVJ ablation results in sympathetic neural changes that favor the occurrence of PMVT and that pacing at 90 beats/min attenuates these changes.METHODSSympathetic nerve activity, 90% monophasic cardiac action potential duration (APD90), right ventricular effective refractory period (ERP) and blood pressure measurements were obtained in 10 patients undergoing AVJ ablation. Sympathetic nerve activity was analyzed at baseline and during and after successful AVJ ablation for at least 10 min. Data were also collected after ablation at pacing rates of 60 and 90 beats/min. The APD90 and ERP were measured before and after AV block during pacing at 120 beats/min.RESULTSSympathetic nerve activity increased to 134 ± 16% of the pre-ablation baseline value (p < 0.01) after successful AVJ ablation plus pacing at 60 beats/min and decreased to 74 ± 8% of baseline (p < 0.05) with subsequent pacing at 90 beats/min. Both APD90 and ERP increased significantly.CONCLUSIONS1) Ablation of the AVJ followed by pacing at 60 beats/min is associated with an increase in SNA. 2) Pacing at 90 beats/min decreases SNA to or below the pre-ablation baseline value. 3) Cardiac APD and ERP increase after AVJ ablation. The increase in SNA, along with the prolongation in APD, may play a role in the pathogenesis of ventricular arrhythmias that occur after AVJ ablation.

Sudden cardiac death accounts for approximately 300,000 deaths annually in the U.S., and most of these are secondary to ventricular tachycardia (VT) and fibrillation in patients with coronary artery disease. Most patients with cardiac death die before reaching the hospital, which brought about a tremendous amount of research focused at identifying patients at high risk. Several trials were initiated to test the effectiveness of various therapeutic measures in these high-risk patients. A history of myocardial infarction, depressed left ventricular function and nonsustained VT have all been identified as independent risk factors for future arrhythmic death. Similarly, patients with a history of sustained VT or a history of sudden cardiac death are a high-risk group and should be aggressively evaluated and treated. The purpose of this article is to discuss risk stratification and primary prevention of sustained ventricular arrhythmias. We also review the recent secondary prevention trials and discuss the options available in the management of patients with sustained ventricular arrhythmias.

The approach to patients with symptomatic ventricular tachycardia (VT) depends on the presence and type of structural heart disease. In patients with underlying heart disease and ventricular fibrillation or sustained symptomatic VT with hemodynamic compromise, the implantable cardioverter-defibrillator (ICD) is superior to antiarrhythmic drugs for the improvement of overall survival. These patients should receive an ICD unless contraindications are present. For patients with sustained VT and a structurally normal heart (idiopathic VT), radiofrequency catheter ablation is a reasonable option. If patients are symptomatic, nonsustained VT should be treated with beta-adrenergic blocking agents or antiarrhythmic drugs, which should be selected on the basis of the underlying cardiovascular substrate. In patients with coronary artery disease, depressed left ventricular function, and nonsustained VT, we recommend the use of programmed electrical stimulation for additional risk stratification. If a sustained ventricular arrhythmia is induced, an ICD should be implanted.

It is apparent that pacing threshold increases following an ICD shock, although the degree of change observed is dependent on the method used to assess pacing and the lead design used. We previously demonstrated a rise in postshock pacing threshold using a lead with integrated bipolar pacing in which the distal shocking coil also serves as the pacing anode. In this study, we sought to investigate whether the postshock pacing threshold increased significantly in an endocardial, steroid-eluting lead with dedicated bipolar pacing electrodes. Twenty patients (16 men, 4 women; median age 73, ejection fraction [EF] 0.17-0.58) were studied during pectoral ICD implantation (Medtronic active can model 7221Cx or 7223Cx with model 6932-65 lead). The diastolic pulse width pacing threshold at 1 or 2 V was determined. Pacing rate was set > or = 100/min at twice diastolic threshold output to assess pacing immediately following the first DFT test shock. For subsequent shocks, the output was adjusted to establish postshock thresholds as 1, 2, 3, or 4 times the diastolic threshold. The postshock threshold was defined as the output yielding 100% capture > or = 2.5 seconds following a shock. In 8 of 20 patients (ratio 0.40 +/- 0.11), a rise in the post-shock threshold was shown by failure of consistent capture when pacing at 2 times diastolic threshold > or = 2.5 seconds after a DFT test shock. Two of these patients failed at 3 times threshold, but none failed at 4 x threshold. Five of 12 patients with successful capture of 2 times threshold failed to capture at threshold. The postshock threshold increased by a mean factor of 2.83 +/- 0.83 in the group of patients with a threshold rise. Following ICD shock in an active can, steroid-eluting lead system with dedicated bipolar pacing, the post-shock threshold increases significantly. Our studies suggest a need for postshock pacing to be set at least 4 x threshold regardless of the lead design.

Atrial stunning, as assessed by left atrial appendage emptying and increased spontaneous echo contrast, is known to occur following direct-current cardioversion of atrial fibrillation (AF) and atrial flutter (AFl). Little is known on atrial mechanical function and the time course of atrial recovery following radiofrequency ablation of AFl. Fourteen patients undergoing radiofrequency ablation of persistent typical counterclockwise AFl were enrolled. Two-dimensional and pulse Doppler transesophageal echocardiography (TEE) were performed before ablation and immediately following restoration of sinus rhythm. Left atrial spontaneous echo contrast grades, left atrial appendage emptying fractions, and peak left atrial appendage emptying velocities were measured. Transthoracic echocardiography (TTE) was performed immediately after ablation, then repeated after 1 day, 1 week, and 6 weeks to measure peak transmitral velocities and percent atrial contribution to ventricular filling. Left atrial appendage emptying velocities decreased significantly following AFl termination (44 ± 23 cm/s before ablation vs 25 ± 14 cm/s after ablation, p = 0.01). Left atrial appendage emptying fractions also decreased significantly (0.48 ± 0.1 preablation vs 0.34 ± 0.17 postablation, p = 0.02). New spontaneous echo contrast developed in 4 patients (29%) after ablation. Four patients had complete atrial standstill after ablation, and 1 patient developed a new left atrial appendage thrombus. The percent atrial contribution to ventricular filling recovered progressively over 6 weeks with significant improvement in peak transmitral velocities at day 7. Thus, atrial stunning occurs after catheter ablation of AFl and may lead to rapid formation of thrombus in the left atrial appendage. Significant improvement in left atrial function occurs in 7 days.

Dusty gas flow through porous media is analysed in this work in an attempt to study the effects of the permeability on the flow geometries that are possible for the two-dimensional flow at hand. We consider the two cases of constant and variable particle number density.

Computational uncertainties inevitably arise due to equivalence representation of a continuum phenomenon by a discrete model, and the subsequent numerical solution of the model which gives rise to a loss of accuracy. In this note, we consider the connection between convergence and uncertainty and identify the functional quantification and modelling that are needed to investigate the propagation of uncertainties due to the numerical scheme, the grid and the adjacent grid points, into the uncertainty in final computed solution when an initial boundary value problem is considered.

An exact solution to the two-dimensional, viscous fluid flow, as governed by the Navier-Stokes equations, is obtained for Riabouchinsky-type flows. A modified solution methodology is developed in this work to better handle the type of flow considered, and is promising in overcoming some of the disadvantages of the traditional approach.

To review our experience with cases of narrow complex tachycardia with VA block, highlighting the difficulties in the differential diagnosis, and the therapeutic implications. Prior reports of patients with narrow complex tachycardia with VA block consist of isolated case reports. The differential diagnosis of this disorder includes: automatic junctional tachycardia, AV nodal reentry with final upper common pathway block, concealed nodofascicular (ventricular) pathway, and intra-Hissian reentry. Between June 1994 and January 1996, six patients with narrow complex tachycardia with episodes of ventriculoatrial block were referred for evaluation. All six patients underwent attempted radiofrequency ablation of the putative arrhythmic site. Three of six patients had evidence suggestive of a nodofascicular tract. Intermittent antegrade conduction over a left-sided nodofascicular tract was present in two patients and the diagnosis of a concealed nodofascicular was made in the third patient after ruling out other tachycardia mechanisms. Two patients had automatic junctional tachycardia, and one patient had atrioventricular nodal reentry with proximal common pathway block. Attempted ablation in the posterior and mid-septum was unsuccessful in patients with nodofascicular tachycardia. In contrast, those with atrioventricular nodal reentry and automatic junctional tachycardia readily responded to ablation. The presence of a nodofascicular tachycardia should be suspected if: (1) intermittent antegrade preexcitation is recorded, (2) the tachycardia can be initiated with a single atrial premature producing two ventricular complexes, and (3) a single ventricular extrastimulus initiates SVT without a retrograde His deflection. The presence of a nodofascicular pathway is common in patients with narrow complex tachycardia and VA block. Unlike AV nodal reentry and automatic junctional tachycardia, the response to ablation is poor.

Many structures used at sea must be able to withstand the occasional extreme weather conditions and the risk of underwater explosions. This applies not only for military ships and submarines but also for tankers and civil exploration and extraction platforms. An understanding is therefore required of the effects of shock induced water waves and unbounded fluid-structure interaction on floating and submerged structures. For modelling purposes these structures may be considered as a system of five components: the structure itself, any fluid within it, the surrounding fluid including the effects of cavitation, the farfield fluid medium and the effect of shock waves. The first two are sufficiently well understood, the remaining three are the subject of continuous research. Recent developments have created new possibilities for treating the farfield fluid medium. Hence, this paper which discusses the various methods used in the modelling of this problem.