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Barchan dunes of the Kharga Depression, Western Desert, Egypt, have been assessed in terms of their morphometry, grain size, and migration rate using remote sensing and GIS techniques and field and laboratory work. Thirty-seven sites were chosen along the Kharga dune belt and subdivided into northern, central, and southern sectors. At each site, several barchans were subjected to morphometric measurements (length, width, height, length of eastern and western horns, and length of windward and leeward sides). The rate and direction of 160 barchans were also measured for the period between 2002 and 2018. Grain size analysis was carried out on sand samples taken from the crest of these dunes. Statistically, significant relationships have been found between the morphometric parameters, dune migration, and grain size attributes. The analysis of the morphology of the barchan dunes, their movement, and the nature of sedimentary materials provide essential information for assessing and evaluating their environmental hazards.

The current study deals with textural, mineralogical, and geochemical characteristics of the barchan dune sands of Abu Muharak dune belts in the Kharga Depression. Abu Muharak is the longest dune belt in the Western Desert of Egypt. Sand samples from 37 sites were texturally, petrologically, and chemically analyzed. Our goals were to interpret the provenance of the sands in terms of grain size, petrology, and geochemistry and correlate these data with the proposed source such as Nubian sandstone, Pleistocene alluvial, and Holocene lacustrine sediments as well as ancient aeolian deposits exposed at the Kharga Depression. The present study concludes that the Moghra sandstone is the main source of the Abu Muharak dune belt with local contributions from Pleistocene alluvial and dune deposits as well as weathered Nubian sandstone in the Kharga Depression.

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Background We hypothesized that cardiovascular physiology differs in reflex syncope patients compared with the general population, predisposing such individuals to vasovagal reflex. Methods In this multicohort cross-sectional study, we compared aggregate data of resting SBP, DBP, pulse pressure (PP) and heart rate (HR), collected from six community-based cohort studies (64 968 observations) with those from six databases of reflex syncope patients (6516 observations), subdivided by age decades and sex. Results Overall, in male individuals with reflex syncope, SBP (-3.4 mmHg) and PP (-9.2 mmHg) were lower and DBP (+2.8 mmHg) and HR (+5.1 bpm) were higher than in the general population; the difference in SBP was higher at ages above 60 years. In female individuals, PP (-6.0 mmHg) was lower and DBP (+4.7 mmHg) and HR (+4.5 bpm) were higher than in the general population; differences in SBP were less pronounced, becoming evident only above 60 years. Compared with male individuals, SBP in female individuals exhibited slower increase until age 40 years, and then demonstrated steeper increase that continued throughout remaining life. Conclusion The patients prone to reflex syncope demonstrate a different resting cardiovascular haemodynamic profile as compared with a general population, characterized by lower SBP and PP, reflecting reduced venous return and lower stroke volume, and a higher HR and DBP, suggesting the activation of compensatory mechanisms. Our data contribute to a better understanding why some individuals with similar demographic characteristics develop reflex syncope and others do not. Video abstract http://links.lww.com/HJH/B580.

Vasovagal syncope is a common cause of syncope which, if recurrent, can have multiple negative consequences such as injury and occupational disability. Various medications can be used to decrease the recurrence of vasovagal syncope but there are no drugs that can be used by patients to interrupt a perceived vasovagal episode.A phase I study was performed to evaluate the tolerability and safety of a gel formulation containing capsaicin (1 mg), phenylephrine HCL (PE) and caffeine citrate (200 mg) (CPC) in normal adult volunteers. Secondary objectives were to characterize the pharmacokinetics (PK) of the CPC formulation and the highest dose of PE needed to achieve a target increase in systolic BP of at least 40 mmHg. After receiving the first dose, a second dose of the CPC mixture was administered at 2 h. Suboptimal changes in systolic blood pressure (SBP) were noted at PE doses of 0.6, 1.2, and 1.8 mg, therefore a second cohort was studied at PE doses of 10, 20, and 30 mg. Blood samples were collected in rapid sequence and were assayed for all three drugs.A total of 17 subjects received the drug with no serious adverse effects reported. All doses were well tolerated, although the capsaicin content usually caused expected temporary oral and gastric discomfort. One subject did not complete the study because of a vasovagal reaction that was associated with the frequent blood sampling. There was a 5-25 min lag in the appearance of measurable blood concentrations of capsaicin and phenylephrine. Most subjects had baseline caffeine concentrations from dietary use, with a gradual increase noted after 15 min consistent with GI absorption. Although the intended criterion of a 40 mmHg increase in SBP was not reached, a clinically significant increase in BP for at least 15 min was noted in the six subjects who received the highest dose of PE (30 mg), with a gradual decline over the next 2 h.The ternary mixture of capsaicin, phenylephrine, and caffeine was well tolerated when administered as two sublingual/oral doses over a 2-h period.

By the beginning of the twenty-first century, education in public and private schools, as well as higher education institutions, was undergoing rapid methodological changes, shifting from huge residential to online, blended, and wireless teaching and learning. On the other hand, assessment, despite being regarded as the backbone of educational systems and the main operating mechanism of classroom educational programs, is either neglected or done irregularly, as in the case of diagnostic needs and formative assessments. Furthermore, the benefits of face-to-face communication, education, counselling, guidance, and follow-up of students' learning successes are often lacking in online schooling (OLS). As a result, it is critical for OLS to adopt a compatible systemic approach to first deliver curricula, instruction, and learning in more rational ways; second, fill the assessment gap that current schooling is suffering from; and third, mentor students of blended learning toward their achievement goals. The systemic assessment framework presented in this study for measuring blended achievement in transnational schools as collaborative learning communities is intended to serve above ultimate reforming purposes.

Syncope is a commonly encountered and challenging problem in medical practice. Presentations are variable, and the causal mechanism often remains elusive even after extensive (and often expensive) evaluation. Clinical practice guidelines have been developed to help guide the multidisciplinary approach necessary to diagnose and manage the broad spectrum of patients presenting with syncope. The American College of Cardiology/American Heart Association, in collaboration with the Heart Rhythm Society, published its first syncope guidelines in 2017. The European Society of Cardiology released the fourth iteration of its syncope guidelines in 2018. This review highlights the differences and congruencies between the 2 sets of recommendations, their implications for clinical practice, the remaining gaps in understanding, and areas of future research.

Introduction Congenital portosystemic shunts (CPSS) are rare vascular malformations that can lead to severe complications. With advanced imaging techniques, diagnosis is becoming more feasible occurring in fetal life. Different approaches have been adopted to manage these cases, with an increased utilization of interventional therapy recently. This cohort aims to describe the course of children diagnosed with CPSS and the impact of interventional therapy on the outcome. Methods Retrospective chart review was done for all patients who were diagnosed with CPSS in our institution between January 2006 and December 2015. Results Six patients were diagnosed with CPSS. During this period, 8,680 mothers carrying 9548 fetuses underwent fetal ultrasound examinations. Three patients were diagnosed antenatally at a median [IQ] gestational age of 33 [26–33] weeks, and three patients were diagnosed postnatally at 0, 2, and 43 months, respectively. At a median follow-up of 87 [74–110] months, 5 patients are alive; 4 of whom had received transcatheter closure for different indications, and one who had spontaneous resolution of her CPSS. One infant died at the age of 6 weeks secondary to sepsis. Conclusion CPSS can result in significant complications in children. Interventional therapy is feasible at any age group, but long-term follow-up is warranted.

BACKGROUNDWe hypothesized that cardiovascular physiology differs in reflex syncope patients compared with general population, predisposing such subjects to vasovagal reflex.METHODSIn this multicohort cross-sectional study, we compared resting systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP) and heart rate (HR), collected from 6 community-based cohort studies (64,968 observations) with those from 6 databases of reflex syncope patients (6516 observations), subdivided by age decades and sex.RESULTSOverall, in males with reflex syncope, SBP (−3.4 mmHg) and PP (−9.2 mmHg) were lower and DBP (+2.8 mmHg) and HR (+5.1 bpm) were higher than in the general population; the difference in SBP was higher at ages >60 years. In females, PP (−6.0 mmHg) was lower and DBP (+4.7 mmHg) and HR (+4.5 bpm) were higher than in the general population; differences in SBP were less pronounced, becoming evident only above 60 years. Compared with males, SBP in females exhibited slower increase until age 40, and then demonstrated steeper increase that continued throughout life.CONCLUSIONThe patients prone to reflex syncope demonstrate a different resting cardiovascular hemodynamic profile characterized by reduced venous return and stroke volume, evidenced by lower SBP and PP, and compensatory increase in HR and vascular resistance, the latter expressed by elevated DBP. The data presented here contribute to our understanding why some subjects with similar demographic characteristics develop reflex syncope and others not.

Background: Asthma and atrial fibrillation (AF) share an underlying inflammatory pathophysiology. We hypothesized that persistent asthmatics are at higher risk for developing AF and that this association would be attenuated by adjustment for baseline markers of systemic inflammation. Methods: The MESA (Multi-Ethnic Study of Atherosclerosis) is a prospective longitudinal study of adults free of cardiovascular disease at baseline. Presence of asthma was determined at exam 1. Persistent asthma was defined as asthma requiring use of controller medications. Intermittent asthma was defined as asthma without use of controller medications. Participants were followed for a median of 12.9 (interquartile range, 10–13.6) years for incident AF. Multivariable Cox regression models were used to assess associations of asthma subtype and AF. Results: The 6615 participants were a mean (SD) 62.0 (10.2) years old (47% male, 27% black, 12% Chinese, and 22% Hispanic). AF incidence rates were 0.11 (95% CI, 0.01–0.12) events/10 person-years for nonasthmatics, 0.11 (95% CI, 0.08–0.14) events/10 person-years for intermittent asthmatics, and 0.19 (95% CI, 0.120.49) events/10 person-years for persistent asthmatics (log-rank P =0.008). In risk-factor adjusted models, persistent asthmatics had a greater risk of incident AF (hazard ratio, 1.49 [95% CI, 1.03–2.14], P =0.03). IL (Interleukin)-6 (hazard ratio, 1.26 [95% CI, 1.13–1.42]), TNF (tumor necrosis factor)-α receptor 1 (hazard ratio, 1.09 [95% CI, 1.08–1.11]) and D-dimer (hazard ratio, 1.10 [95% CI, 1.02–1.20]) predicted incident AF, but the relationship between asthma and incident AF was not attenuated by adjustment for any inflammation marker (IL-6, CRP [C-reactive protein], TNF-α R1, D-dimer, and fibrinogen). Conclusions: In a large multiethnic cohort with nearly 13 years follow-up, persistent asthma was associated with increased risk for incident AF. This association was not attenuated by adjustment for baseline inflammatory biomarkers.

Glenn N. Levine, MD, FACC, FAHA, Chair Patrick T. O’Gara, MD, MACC, FAHA, Chair-Elect Jonathan L. Halperin, MD, FACC, FAHA, Immediate Past Chair [#][1] Sana M. Al-Khatib, MD, MHS, FACC, FAHA Kim K. Birtcher, MS, PharmD, AACC Biykem Bozkurt, MD, PhD, FACC, FAHA Ralph G. Brindis, MD, MPH

Backgrounds The purpose of the study was to assess the clinical outcome of patients with situational syncope (SS) compared to patients with vasovagal syncope (VVS). Methods We assessed the prevalence, patients’ characteristics, and outcome of consecutive patients with SS and VVS who presented to the Faint and Fall Clinic (University of Wisconsin) between January 2013 and December 2015. Results SS was found in 55/1,401 (4.0%) syncope patients with follow-up data available in 47 patients: defecation (n = 16), micturition (n = 15), cough (n = 10), swallow (n = 3), laughter (n = 1), sneeze (n = 1), and cough plus laughter (n = 1). Over the same time period, 252/1,401 patients (18%) were diagnosed with VVS with follow-up data available in 171 patients. Compared with VVS patients, SS patients were older, more likely to be male, had a higher prevalence of hypertension, had an absence of prodromes, and experienced more injuries at the time of syncope (P = 0.01 for all). During a mean follow-up duration of 15.4 ± 9.1 months, syncope recurred in 5/47 (10.6%) patients with SS and 16/171 (9.4%) patients with VVS. The recurrence rates at 1 year and 2 years were 20% (95% SE ± 13) and 40% (95% SE ± 20) for the SS group, and 23% (95% SE ± 13) and 43% (95% SE ± 20) for the VVS group (P = 0.6). No patient died. Conclusions We have shown in a large cohort of consecutive patients with syncope that SS is a relatively infrequent form of reflex syncope with different clinical characteristics but similar recurrence rate to VVS.

Syncope/Collapse is a common syndrome in the general population caused by various etiologies. Given the often, complex presentations, there is a wide variability in the management of patients with syncope/collapse resulting in significant differences in outcome and high cost burden. Syncope units (SUs) have been developed with the intent of ensuring a systematic approach toward the evaluation of patients with transient loss of consciousness from risk stratification to diagnosis, therapy, and follow-up. Several studies have shown that SUs improve the rate of diagnosis and decrease rates of admissions and unnecessary tests utilization. The ideal SU should have resources for interdisciplinary testing and consultations available in a timely manner. In this chapter, we discuss the several models of successful SUs available in addition to future perspectives in addressing this ongoing challenge.

In this chapter, we explore the economic impact of syncope and potential strategies to attenuate the burden. Syncope is a very common problem with an estimated yearly cost greater than $10 billion USD annually in the USA alone. Direct costs include costs of health care-delivery, while indirect cost includes the impact on patient and society such as loss of productivity and earning potential. Drivers of direct cost include the high admission rate, unnecessary tests utilization, and unexplained syncope. Decreasing both direct and indirect costs is contingent on obtaining an accurate diagnosis through a standardized approach informed by the guidelines. More advanced data methods such as machine learning, point-of-care software, telemedicine, and use of non-physician providers may also help further reduce cost, and expand cost-effective state-of-the-art syncope care in areas where it is much needed.

The sinus node (SN) has unique tissue, cellular, and subcellular characteristics for automaticity that are responsive to physiologic needs. Autonomic regulation of the SN determines SN rate. In the absence of the autonomic regulation, the intrinsic heart rate (IHR) can be measured and used to assess intrinsic abnormalities. Inappropriate sinus tachycardia (IST) is a rare clinical syndrome characterized by elevated resting heart rate (HR) and/or exaggerated HR response to exercise. IST occurs in the absence of physiology demand and patients may present with or without symptoms. Symptoms in patients with IST can be variable including palpitations, fatigue, and sensation of a racing heartbeat. The prevalence of IST is incompletely defined due to incomplete sampling, reporting, and absence of symptoms in some patients. It is clinically recognized that a high number of symptomatic IST patients are female with a variable age range of 18–50 years of age. There are several theories of the mechanistic etiology of IST, which can be categorized as either intrinsic or extrinsic. IST patients can present with symptoms similar to those seen in patients with postural orthostatic tachycardia syndrome and focal atrial tachycardia. A detailed history and assessment of the P-wave morphology are crucial in making the correct diagnosis. Successful management requires treatment approaches directed toward specific symptoms/overlapping syndromes as well as HR control. Newer drug therapy has become more effective than invasive SN modification with ablation, and future research into IST initiating etiology will undoubtedly improve the long-term successful treatment.

The autonomic nervous system is designed to maintain physiologic homeostasis. Its widespread connections make it vulnerable to disruption by many disease processes including primary etiologies such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure and secondary etiologies such as diabetes mellitus, amyloidosis, and immune-mediated illnesses. The result is numerous symptoms involving the cardiovascular, gastrointestinal, and urogenital systems. Patients with autonomic dysfunction (AUD) often have peripheral and/or cardiac denervation leading to impairment of the baroreflex, which is known to play a major role in determining hemodynamic outcome during orthostatic stress and low cardiac output states. Heart rate and plasma norepinephrine responses to orthostatic stress are helpful in diagnosing impairment of the baroreflex in patients with orthostatic hypotension (OH) and suspected AUD. Similarly, cardiac sympathetic denervation diagnosed with MIBG scintigraphy or

Syncope is a commonly encountered and challenging problem in medical practice. Presentations are variable, and the causal mechanism often remains elusive even after extensive (and often expensive) evaluation. Clinical practice guidelines have been developed to help guide the multidisciplinary approach necessary to diagnose and manage the broad spectrum of patients presenting with syncope. The American College of Cardiology/American Heart Association, in collaboration with the Heart Rhythm Society, published its first syncope guidelines in 2017. The European Society of Cardiology released the fourth iteration of its syncope guidelines in 2018. This review highlights the differences and congruencies between the 2 sets of recommendations, their implications for clinical practice, the remaining gaps in understanding, and areas of future research.

Objectives The purpose of this study was to better understand the role of the baroreflex in tilt-induced vasovagal syncope (VVS). Background 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. Methods 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). Results 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). Conclusions 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.

Background According to the ACC/AHA/HRS guidelines, cardiac pacing is reasonable in patients with bifascicular block (BF-B) and syncope when other causes have been excluded. The purpose of this study was to assess the long-term outcome of patients with BF-B and unexplained syncope following cardiac pacing. Methods and results Between 2009 and 2015, we identified 43 consecutive patients (mean age of 78 ± 12 years, 64% males) who presented with syncope and BF-B and had received a pacemaker (PM). During a mean follow-up period of 31 ± 21 months, syncope recurred in seven patients (16%): 7% (95% standard error [SE] ± 3%) at 1 year and 18% (95% SE ± 7%) at 5 years. At univariable analysis, the only predictor of syncope recurrence was empiric pacing (P = 0.03). There were no syncope recurrences in the 12 patients who received a PM following a positive electrophysiological study (EPS) and the five patients with documentation of paroxysmal atrioventricular block (AVB) during cardiac monitoring (insertable loop recorder [ILR]), (EPS/ILR Group, n = 17) compared to seven of 26 (27%) patients who received empiric pacing (Empiric Group, n = 26; P = 0.02). Progression to high-degree AVB was documented during follow-up in 16 (37%) patients: nine of 17 (53%) patients in the EPS/ILR Group and seven of 26 (27%) patients in the Empiric Group (P = 0.11). There were no injuries reported during ILR monitoring. Conclusions We have shown that syncope recurs not infrequently in patients with BF-B who received pacing for syncope. Nearly one in four patients who had empiric pacing suffered syncope recurrence compared to no recurrences in patients who received a PM following a positive EPS or documentation of transient AVB.

The period of recorded history extends to 5,000 years BC, where Sumerian-Akkadian script confirmed the fact of being the oldest discovered record of coherent writing from the preliterate period around the 3000 BC (SE Alcock, 2001; Woods, 2010). Since that date of early basic literacy of human history, B.C pioneers, philosophers, leaderships and professionals exerted every efforts to advance their local environments in politics, state identity, public administration, urban centers, culture and faith, education, innovative thoughts and arts, and civic daily life. Consequently, B.C significant ancient states and civilizations arose and flourished into world sovereign empires, exceeding in several fields their contemporary counterparts the so-called “Big Powers” in the 21st century A.C. Even these “Big Powers” proved helpless in resisting the invisible virus “Corona”, which caused the death of hundreds of thousands of persons, and is threatening millions of others in facing health problems or termination later. The status of world states (powerful or marginal) is determined by the quality of its educational systems. Further, the future of civic and productive students as adults is dependent upon the rigor of schooling methodologies, which encompass: learners who are dedicated to learn; teachers who guide and teach; peers who are collaborative learning partners; curricula, which are served by textbooks and material in the classrooms; methods, techniques and technologies as communicative tools of education and management messages; and school environments, which physically host most education factors, processes and services. Hence, this research article examined the educational methodologies cumulative from BC Sophists to the ICTs revolution at 2000+ A.C. a Comparative analytic review was conducted to specify the advances and setbacks accrued during the extended 500B.C-2000+A.C years in the lives of generations as future crucial professional, leaderships and pioneer assets of society.

The autonomic nervous system is designed to maintain physiologic homeostasis. Its widespread connections make it vulnerable to disruption by many disease processes including primary etiologies such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure and secondary etiologies such as diabetes mellitus, amyloidosis, and immune-mediated illnesses. The result is numerous symptoms involving the cardiovascular, gastrointestinal, and urogenital systems. Patients with autonomic dysfunction (AUD) often have peripheral and/or cardiac denervation leading to impairment of the baroreflex, which is known to play a major role in determining hemodynamic outcome during orthostatic stress and low cardiac output states. Heart rate and plasma norepinephrine responses to orthostatic stress are helpful in diagnosing impairment of the baroreflex in patients with orthostatic hypotension (OH) and suspected AUD. Similarly, cardiac sympathetic denervation diagnosed with MIBG scintigraphy or 18F-DA PET scanning has also been shown to be helpful in distinguishing preganglionic from postganglionic involvement and in diagnosing early stages of neurodegenerative diseases. In this chapter, we review the causes of AUD, the pathophysiology and resulting cardiovascular manifestations with emphasis on the diagnosis and treatment of OH.

Background The mechanism of inappropriate sinus tachycardia ( IST ) remains incompletely understood. Methods and Results We prospectively compared 3 patient groups: 11 patients with IST ( IST Group), 9 control patients administered isoproterenol (Isuprel Group), and 15 patients with cristae terminalis atrial tachycardia (AT Group). P‐wave amplitude in lead II and PR interval were measured at a lower and higher heart rate ( HR 1 and HR 2, respectively). P‐wave amplitude increased significantly with the increase in HR in the IST Group (0.16±0.07 mV at HR 1=97±12 beats per minute versus 0.21±0.08 mV at HR 2=135±21 beats per minute, P =0.001). The average increase in P‐wave amplitude in the IST Group was similar to the Isuprel Group ( P =0.26). PR interval significantly shortened with the increases in HR in the IST Group (146±15 ms at HR 1 versus 128±16 ms at HR 2, P PR interval was noted in the Isuprel Group ( P =0.6). In contrast, patients in the atrial tachycardia Group experienced PR lengthening during atrial tachycardia when compared with baseline normal sinus rhythm (153±25 ms at HR 1=78±17 beats per minute versus 179±29 ms at HR 2=140±28 beats per minute, P Conclusions We have shown that HR increases in patients with IST were associated with an increase in P‐wave amplitude in lead II and PR shortening similar to what is seen in healthy controls following isoproterenol infusion. The increase in P‐wave amplitude and absence of PR lengthening in IST support an extrinsic mechanism consistent with a state of sympatho‐excitation with cephalic shift in sinus node activation and enhanced atrioventricular nodal conduction.

We have previously shown that up to one-third of patients develop no change or an increase in sinus node cycle length (SNCL) during ventricular fibrillation (VF). The purpose of the present study was to investigate the mechanism of SNCL changes during VF in a swine model. We hypothesized that changes in SNCL during VF are vagally-mediated. In 33 anesthetized pigs DC current was used to induce VF for 10 s followed by defibrillation. SNCL changes were assessed during VF and compared to baseline. Animals that had ventriculo-atrial conduction during VF were excluded. Post-defibrillation, the pigs were randomized to receive atropine, propranolol, atropine + propranolol or placebo followed by repeat VF induction and measurement of SNCL changes. Ventriculo-atrial conduction was present in 14 pigs prohibiting SNCL measurements. In the remaining 19 animals, 10 demonstrated SNCL shortening (S-Group) and 9 demonstrated non-shortening (NS-Group). Atropine decreased the absolute change in SNCL from 51.2 to 26.6 ms (n = 6; p = 0.03). It attenuated the SNCL shortening previously observed in the S-Group (−99.2 ms versus −47.9 ms, p = 0.04) and reversed the SNCL prolongation initially observed in the NS-Group (27.1 ms versus −6.5 ms, p = 0.13). Similarly, atropine + propranolol decreased the absolute change in SNCL from 33.3 to 12.2 ms (n = 4; p = 0.05). No significant changes were noted with propranolol or placebo. The SNCL changes during VF appear to be vagally-mediated. The clinical implications vis-a-vis defibrillation threshold and future device programming await future studies.

The European Society of Cardiology (ESC) has played an important role in advancing our understanding of the causes, optimal investigation, and management of syncope through publication of practice guidelines in 2001, 2004, and 2009.1–3 The 2009 ESC guidelines recommend the establishment of formal Syncope Units (SUs)—either virtual or physical site within a hospital or clinic facility—with access to syncope specialists and specialized equipment.3 In response, this position statement by the European Heart Rhythm Association (EHRA) endorsed by the Heart Rhythm Society (HRS) offers a pragmatic approach to the rationale and requirement for an SU, based on specialist consensus, existing practice and scientific evidence (see Appendix). The panel consists of specialists who have experience in developing and leading such units representing cardiology, geriatric and general internal medicine, neurology, and emergency medicine. This document is addressed to physicians and others in administration, who are interested in establishing an SU in their hospital, so that they can meet the standards proposed by ESC-EHRA-HRS.1–3 ### Definition of syncope and transient loss of consciousness Syncope is a transient loss of consciousness (T-LOC) due to transient global cerebral hypoperfusion, and is characterized by rapid onset, short duration, and spontaneous complete recovery. This definition of syncope has been developed by the Task Force for the Diagnosis and Management of Syncope of the ESC and endorsed by the EHRA, European Heart Failure Association and European Heart Rhythm Society. Transient loss of consciousness is a term that encompasses all disorders characterized by self-limited LOC, irrespective of mechanism.1–3 By including the mechanism of unconsciousness, i.e. transient global cerebral hypoperfusion, the current syncope definition excludes other causes of T-LOC such as epileptic seizures and concussion, as well as certain common syncope mimics, such as psychogenic pseudosyncope. ### Definition of a Syncope Unit An SU is a facility featuring a standardized approach to the diagnosis and management …

Syncope is defined as transient loss of consciousness due to global cerebral hypoperfusion. It is characterized by having a relatively rapid onset, brief duration with spontaneous and full recovery. The major challenge in the evaluation of patients with syncope is that most patients are asymptomatic at the time of their presentation. A thorough history and physical examination including orthostatic assessment are crucial for making the diagnosis. After initial evaluation, short-term risk assessment should be performed to determine the need for admission. If the short-term risk is high, inpatient evaluation is needed. If the short-term risk is low, outpatient evaluation is recommended. In patients with suspected cardiac syncope, monitoring is indicated until a diagnosis is made. In patients with suspected reflex syncope or orthostatic hypotension, outpatient evaluation with tilt-table testing is appropriate. Syncope units have been shown to improve the rate of diagnosis while reducing cost and thus are highly recommended.

Neuroendocrine syncope is a newly proposed term to embody both syncope of reflex and adenosine-related etiology. Recent publications on tilt testing have revealed the presence of a hypotensive tendency in some patients, even in the face of severe cardioinhibition. This new understanding may allow better selection of older reflex syncope patients, documented by ECG loop recorder, for successful pacing where tilt testing is ideally negative for a good result in terms of few syncope recurrences and prompts a less aggressive management policy when hypotensive medication is required. Furthermore, plasma adenosine levels not only define a new group of patients who have low adenosine and will respond well to cardiac pacing but also, by assessing adenosine receptor affinity, offer a possible explanation for vasodepression accompanying severe cardioinhibition. The question of the timing of loss of consciousness in reflex syncope needs to be addressed because, if consciousness is lost before asystole, pacing is likely to be ineffective.

Background 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. Methods 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. Results 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 (P < 0.01). 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. Conclusions 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.