Aging-associated susceptibility to stress-induced ventricular arrhythmogenesis is attenuated by tetrodotoxin.

Aging is associated with increased prevalence of life-threatening ventricular arrhythmias, but mechanisms underlying higher susceptibility to arrhythmogenesis and means to prevent such arrhythmias under stress are not fully defined. We aimed to define differences in aging-associated susceptibility to ventricular fibrillation (VF) induction between young and aged hearts. VF induction was attempted in isolated perfused hearts of young (6-month) and aged (24-month-old) male Fischer-344 rats by rapid pacing before and following isoproterenol (1 µM) or global ischemia and reperfusion (I/R) injury with or without pretreatment with low-dose tetrodotoxin, a late sodium current blocker. At baseline, VF could not be induced; however, the susceptibility to inducible VF after isoproterenol and spontaneous VF following I/R was 6-fold and 3-fold higher, respectively, in old hearts (P < 0.05). Old animals had longer epicardial monophasic action potential at 90% repolarization (APD90; P < 0.05) and displayed a loss of isoproterenol-induced shortening of APD90 present in the young. In isolated ventricular cardiomyocytes from older but not younger animals, 4-aminopyridine prolonged APD and induced early afterdepolarizations (EADs) and triggered activity with isoproterenol. Low-dose tetrodotoxin (0.5 µM) significantly shortened APD without altering action potential upstroke and prevented 4-aminopyridine-mediated APD prolongation, EADs, and triggered activity. Tetrodotoxin pretreatment prevented VF induction by pacing in isoproterenol-challenged hearts. Vulnerability to VF following I/R or catecholamine challenge is significantly increased in old hearts that display reduced repolarization reserve and increased propensity to EADs, triggered activity, and ventricular arrhythmogenesis that can be suppressed by low-dose tetrodotoxin, suggesting a role of slow sodium current in promoting arrhythmogenesis with aging.

Knowledge Gaps in Cardiovascular Care of the Older Adult Population: A Scientific Statement From the American Heart Association, American College of Cardiology, and American Geriatrics Society.

The incidence and prevalence of most cardiovascular disorders increase with age, and cardiovascular disease is the leading cause of death and major disability in adults ≥75 years of age; however, despite the large impact of cardiovascular disease on quality of life, morbidity, and mortality in older adults, patients aged ≥75 years have been markedly underrepresented in most major cardiovascular trials, and virtually all trials have excluded older patients with complex comorbidities, significant physical or cognitive disabilities, frailty, or residence in a nursing home or assisted living facility. As a result, current guidelines are unable to provide evidence-based recommendations for diagnosis and treatment of older patients typical of those encountered in routine clinical practice. The objectives of this scientific statement are to summarize current guideline recommendations as they apply to older adults, identify critical gaps in knowledge that preclude informed evidence-based decision making, and recommend future research to close existing knowledge gaps. To achieve these objectives, we conducted a detailed review of current American College of Cardiology/American Heart Association and American Stroke Association guidelines to identify content and recommendations that explicitly targeted older patients. We found that there is a pervasive lack of evidence to guide clinical decision making in older patients with cardiovascular disease, as well as a paucity of data on the impact of diagnostic and therapeutic interventions on key outcomes that are particularly important to older patients, such as quality of life, physical function, and maintenance of independence. Accordingly, there is a critical need for a multitude of large population-based studies and clinical trials that include a broad spectrum of older patients representative of those seen in clinical practice and that incorporate relevant outcomes important to older patients in the study design. The results of these studies will provide the foundation for future evidence-based guidelines applicable to older patients, thereby enhancing patient-centered evidence-based care of older people with cardiovascular disease in the United States and around the world.

Magnetic resonance imaging in patients with recently implanted pacemakers.

BACKGROUND: Recent studies have shown that magnetic resonance imaging (MRI) of patients with pacemakers can be safely performed under careful monitoring, but they excluded patients with recently implanted devices. Patients with recent implants may be at a greater risk for complications during MRI imaging due to lack of lead and wound maturity. METHODS: We implemented a clinical protocol for MRI imaging of patients with implanted cardiac devices, and prospectively collected data. For this study, we retrospectively analyzed two groups of patients: those with recently implanted (≤42 days) and nonrecently implanted (>42 days) leads at the time of MRI scanning. All devices were interrogated before and after scanning, and were reprogrammed during the scan as per protocol. RESULTS: Of the 219 scans (in 171 patients), eight included patients with recently implanted (range: 7-36 days) and 211 with only nonrecently implanted pacemaker leads. During the scan, there were no complications in the early or late group. In one patient imaged 79 days postimplant, frequent premature ventricular complexes were noted during the scan, requiring no action. No patient reported pain during or immediately after the procedure. No clinically significant changes in function were seen at subsequent follow up (average 104 days post-MRI). Compared to patients with nonrecently implanted leads, there was no difference in any parameter between the two groups. CONCLUSIONS: With a strong clinical indication and with careful monitoring, MRI imaging is feasible in patients with recently implanted pacemakers, although experience is limited.

Causes of Early Mortality After Ventricular Tachycardia Ablation in Patients With Reduced Ejection Fraction.

BACKGROUND: Recognition of the causes of early mortality after ventricular tachycardia (VT) ablation in patients with reduced left ventricular ejection fraction (LVEF) is an essential step toward improving postprocedural outcomes. OBJECTIVES: This study sought to determine the causes of early mortality (≤30 days) after VT ablation in patients with reduced LVEF and to understand further the circumstances surrounding death after the procedure. METHODS: We performed a retrospective analysis of all patients undergoing VT ablation in patients with reduced LVEF from January 1, 2013, to November 10, 2021, at the Mayo Clinic (Rochester, Phoenix, and Jacksonville). Causes of death were identified through a detailed chart review of the electronic health record within the Mayo Clinic system and outside records. RESULTS: A total of 503 patients (mean age 63 ± 13 years, 11.2% women) with ejection fraction <50% were included in the study. The 30-day all-cause mortality rate was 5.0% (n = 25), and the mortality rate due to a procedural complication was 0.4%. Among all 30-day deaths, recurrent VT was the most common primary cause of death (44.0%). This was followed by decompensated heart failure (28.0%), procedure-related death (8.0%), cerebrovascular accident (4.0%), and infection (4.0%). Most patients (91.0%) who died from VT had VT recurrence within 3 days of the ablation. The average PAINESD score among early mortality was 20 ± 4, and 92.0% of these patients (n = 23) had a score >15. Significant predictors of early mortality included nonischemic cardiomyopathy, lower LVEF, electrical storm, and ventricular fibrillation. CONCLUSIONS: The overall early mortality (≤30 days) rate after catheter ablation of VT in patients with reduced LVEF was 5.0%, but the death rate directly due to a procedural complication was only 0.4%. The most common cause of death was recurrent VT, followed by heart failure. Further research into ablation strategies is vital to improving the safety, efficacy, and durability of VT ablation.

Risk factors for implantable defibrillator lead fracture in a recalled and a nonrecalled lead.

INTRODUCTION: The Medtronic Sprint Fidelis implantable cardioverter defibrillator (ICD) lead was "recalled" in October 2007 after 268,000 implants worldwide due to increased failure risk. Manufacturer suggested monitoring has not been shown effective at preventing adverse events. Only limited data exist regarding clinical predictors of Fidelis lead fracture. We sought to identify risk factors for Fidelis fracture to guide clinical monitoring and compare its performance with a control lead. METHODS: Fractured lead cases were retrospectively reviewed for demographic data, implant technique, radiographic appearance and clinical presentation was analyzed. Lead survival was compared using Kaplan-Meir curves. RESULTS: Study patients (n = 1314) experienced 18 Fidelis and 6 Quattro lead fractures. Patients with failed Fidelis leads were younger than those with surviving leads (49.5 vs 64.6 years, P = 0.0066). Fidelis lead fractures often occurred around the time of physical activity. No other measured demographic or technique related factors were associated with lead fracture. Fidelis leads had significantly decreased survival compared with Quattro leads (89.3 vs 98.9% at 30 months). Patients less than 50 years old had significantly decreased lead survival compared with those older than 50 in both Fidelis (79.6% vs 96.5% at 24 months) and Quattro (93.4 vs 99.8%, P < 0.001 at 24 months) leads. CONCLUSIONS: Patients under age 50, with either Fidelis or Quattro ICD leads, are at increased risk of lead fracture compared with patients over 50, particularly around the time of intense physical activity. Aggressive monitoring and advisory programming appears warranted in patients with Fidelis leads as well as especially in younger patients.

Impact of pulsed electromagnetic field therapy on vascular function and blood pressure in hypertensive individuals.

The present study investigated the impact of 12 weeks of pulsed electromagnetic field (PEMF) therapy on peripheral vascular function, blood pressure (BP), and nitric oxide in hypertensive individuals. Thirty hypertensive individuals (SBP > 130 mm Hg and/or MAP > 100 mm Hg) were assigned to either PEMF group (n = 15) or control group (n = 15). During pre-assessment, participants underwent measures of flow-mediated dilation (FMD), BP, and blood draw for nitric oxide (NO). Subsequently, they received PEMF therapy 3x/day for 12 weeks and, at conclusion, returned to the laboratory for post-assessment. Fifteen participants from the PEMF group and 11 participants from the control group successfully completed the study protocol. After therapy, the PEMF group demonstrated significant improvements in FMD and FMDNOR (normalized to hyperemia), but the control group did not (P = .05 and P = .04, respectively). Moreover, SBP, DBP, and MAP were reduced, but the control group did not (P = .04, .04, and .03, respectively). There were no significant alterations in NO in both groups (P > .05). Twelve weeks of PEMF therapy may improve BP and vascular function in hypertensive individuals. Additional studies are needed to identify the mechanisms by which PEMF affects endothelial function.

Leadless pacemaker: Performance and complications.

Traditional transvenous cardiac pacemakers have pitfalls due to lead- and device pocket-related complications. Leadless pacemakers were developed and introduced into clinical practice to overcome the shortcomings of traditional transvenous pacemakers. In this review, we provide a description of leadless pacemaker devices, and summarize existing data on device performance. We also describe associated complications during implantation procedure as well as during the follow-up period. Although current generation devices are limited to single-chamber pacing, future generation devices are expected to progress to multi-chamber multi-component pacing systems, and eventually to battery-less devices.

Knowledge Gaps in Cardiovascular Care of the Older Adult Population: A Scientific Statement From the American Heart Association, American College of Cardiology, and American Geriatrics Society.

The incidence and prevalence of most cardiovascular disorders increase with age, and cardiovascular disease is the leading cause of death and major disability in adults ≥75 years of age; however, despite the large impact of cardiovascular disease on quality of life, morbidity, and mortality in older adults, patients aged ≥75 years have been markedly underrepresented in most major cardiovascular trials, and virtually all trials have excluded older patients with complex comorbidities, significant physical or cognitive disabilities, frailty, or residence in a nursing home or assisted living facility. As a result, current guidelines are unable to provide evidence-based recommendations for diagnosis and treatment of older patients typical of those encountered in routine clinical practice. The objectives of this scientific statement are to summarize current guideline recommendations as they apply to older adults, identify critical gaps in knowledge that preclude informed evidence-based decision making, and recommend future research to close existing knowledge gaps. To achieve these objectives, we conducted a detailed review of current American College of Cardiology/American Heart Association and American Stroke Association guidelines to identify content and recommendations that explicitly targeted older patients. We found that there is a pervasive lack of evidence to guide clinical decision making in older patients with cardiovascular disease, as well as a paucity of data on the impact of diagnostic and therapeutic interventions on key outcomes that are particularly important to older patients, such as quality of life, physical function, and maintenance of independence. Accordingly, there is a critical need for a multitude of large population-based studies and clinical trials that include a broad spectrum of older patients representative of those seen in clinical practice and that incorporate relevant outcomes important to older patients in the study design. The results of these studies will provide the foundation for future evidence-based guidelines applicable to older patients, thereby enhancing patient-centered evidence-based care of older people with cardiovascular disease in the United States and around the world.

Knowledge Gaps in Cardiovascular Care of Older Adults: A Scientific Statement from the American Heart Association, American College of Cardiology, and American Geriatrics Society: Executive Summary.

The incidence and prevalence of most cardiovascular disorders increase with age, and cardiovascular disease (CVD) is the leading cause of death and major disability in adults aged 75 and older. Despite the effect of CVD on quality of life, morbidity, and mortality in older adults, individuals aged 75 and older have been markedly underrepresented in most major cardiovascular trials, and virtually all trials have excluded older adults with complex comorbidities, significant physical or cognitive disabilities, frailty, or residence in nursing homes and assisted living facilities. As a result, current guidelines are unable to provide evidence-based recommendations for diagnosis and treatment of older adults typical of those encountered in routine clinical practice. The objectives of this scientific statement are to summarize current guideline recommendations as they apply to older adults, identify critical gaps in knowledge that preclude informed evidence-based decision-making, and recommend future research to close existing knowledge gaps. To achieve these objectives, a detailed review was conducted of current American College of Cardiology/American Heart Association (ACC/AHA) and American Stroke Association (ASA) guidelines to identify content and recommendations that explicitly targeted older adults. A pervasive lack of evidence to guide clinical decision-making in older adults with CVD was found, as well as a paucity of data on the effect of diagnostic and therapeutic interventions on outcomes that are particularly important to older adults, such as quality of life, physical function, and maintenance of independence. Accordingly, there is a critical need for a multitude of large population-based studies and clinical trials that include a broad spectrum of older adults representative of those seen in clinical practice and that incorporate relevant outcomes important to older adults in the study design. The results of these studies will provide the foundation for future evidence-based guidelines applicable to older adults and enhance person-centered care of older individuals with CVD in the United States and around the world.

Variability of phase shift between blood pressure and heart rate fluctuations: a marker of short-term circulation control.

BACKGROUND: We postulated that the variability of the phase shift between blood pressure and heart rate fluctuation near the frequency of 0.10 Hz might be useful in assessing autonomic circulatory control. METHODS AND RESULTS: We tested this hypothesis in 4 groups of subjects: 28 young, healthy individuals; 13 elderly healthy individuals; 25 patients with coronary heart disease; and 19 patients with a planned or implanted cardioverter-defibrillator (ICD recipients). Data from 5 minutes of free breathing and at 2 different, controlled breathing frequencies (0.10 and 0.33 Hz) were used. Clear differences (P<0.001) in variability of phase were evident between the ICD recipients and all other groups. Furthermore, at a breathing frequency of 0.10 Hz, differences in baroreflex sensitivity (P<0.01) also became evident, even though these differences were not apparent at the 0.33-Hz breathing frequency. CONCLUSIONS: The frequency of 0.10 Hz represents a useful and potentially important one for controlled breathing, at which differences in blood pressure-RR interactions become evident. These interactions, whether computed as a variability of phase to define stability of the blood pressure-heart rate interaction or defined as the baroreflex sensitivity to define the gain in heart rate response to blood pressure changes, are significantly different in patients at risk for sudden arrhythmic death. In young versus older healthy individuals, only baroreflex gain is different, with the variability of phase being similar in both groups. These measurements of short-term circulatory control might help in risk stratification for sudden cardiac death.

Syncope Evaluation in the Emergency Department Study (SEEDS): a multidisciplinary approach to syncope management.

BACKGROUND: The primary aim and central hypothesis of the study are that a designated syncope unit in the emergency department improves diagnostic yield and reduces hospital admission for patients with syncope who are at intermediate risk for an adverse cardiovascular outcome. METHODS AND RESULTS: In this prospective, randomized, single-center study, patients were randomly allocated to 2 treatment arms: syncope unit evaluation and standard care. The 2 groups were compared with chi2 test for independence of categorical variables. Wilcoxon rank sum test was used for continuous variables. Survival was estimated with the Kaplan-Meier method. One hundred three consecutive patients (53 women; mean age 64+/-17 years) entered the study. Fifty-one patients were randomized to the syncope unit. For the syncope unit and standard care patients, the presumptive diagnosis was established in 34 (67%) and 5 (10%) patients (P<0.001), respectively, hospital admission was required for 22 (43%) and 51 (98%) patients (P<0.001), and total patient-hospital days were reduced from 140 to 64. Actuarial survival was 97% and 90% (P=0.30), and survival free from recurrent syncope was 88% and 89% (P=0.72) at 2 years for the syncope unit and standard care groups, respectively. CONCLUSIONS: The novel syncope unit designed for this study significantly improved diagnostic yield in the emergency department and reduced hospital admission and total length of hospital stay without affecting recurrent syncope and all-cause mortality among intermediate-risk patients. Observations from the present study provide benchmark data for improving patient care and effectively utilizing healthcare resources.

Noncontact mapping to guide ablation of right ventricular outflow tract tachycardia.

OBJECTIVES: [corrected] The aim of this study was to determine whether noncontact mapping is feasible in the right ventricle and assess its utility in guiding ablation of difficult-to-treat right ventricular outflow tract (RVOT) ventricular tachycardia (VT). BACKGROUND: In patients without inducible arrhythmia, RVOT VT may be difficult to ablate. Noncontact mapping permits ablation guided by a single tachycardia complex, which may facilitate ablation of difficult cases. However, the mapping system may be geometry-dependent, and it has not been validated in the unique geometry of the RVOT. METHODS: Ten patients with left bundle inferior axis VT, no history of myocardial infarction and normal left ventricular function underwent noncontact guided ablation; seven had failed previous ablation and three had received a defibrillator. All noncontact maps were analyzed by a blinded reviewer to determine whether the arrhythmia focus was epicardial and to predict on the basis of the map whether arrhythmia would recur. RESULTS: The procedure was acutely successful in 9 of 10 patients. During a mean follow-up of 11 months, 7 of 9 patients remained arrhythmia-free. Both patients in whom the blinded reviewer predicted failure had arrhythmia recurrence: one due to epicardial origin with multiple endocardial exit sites and one due to discordance between site of lesion placement and earliest activation on noncontact map. CONCLUSIONS: Mechanisms of ablation failure in RVOT VT include absence of sustained arrhythmia, difficulty with substrate localization and epicardial origin of arrhythmia. In this study, noncontact mapping was safely and effectively used to guide ablation of patients with difficult-to-treat RVOT VT.

Familial atrial fibrillation is a genetically heterogeneous disorder.

OBJECTIVES: The aims of this study were to identify and characterize familial cases of atrial fibrillation (AF) in our clinical practice and to determine whether AF is genetically heterogeneous. BACKGROUND: Atrial fibrillation is not generally regarded as a heritable disorder, yet a genetic locus for familial AF was previously mapped to chromosome 10. METHODS: Of 2,610 patients seen in our arrhythmia clinic during an 18-month study period, 914 (35%) were diagnosed with AF. Familial cases were identified by history and medical records review. Four multi-generation families with autosomal dominant AF (FAF 1 to 4) were tested for linkage to the chromosome 10 AF locus. RESULTS: Fifty probands (5% of all AF patients; 15% of lone AF patients) were identified with lone AF (age 41 +/- 9 years) and a positive family history (1 to 9 additional relatives affected). In FAF 1 to 3, AF was associated with rapid ventricular response. In contrast, AF in FAF-4 was associated with a slow ventricular response and, with progression of the disease, junctional rhythm and cardiomyopathy. Genotyping of FAF 1 to 4 with deoxyribonucleic acid markers spanning the chromosome 10q22-q24 region excluded linkage of AF to this locus. In FAF-4, linkage was also excluded to the chromosome 3p22-p25 and lamin A/C loci associated with familial AF, conduction system disease, and dilated cardiomyopathy. CONCLUSIONS: Familial AF is more common than previously recognized, highlighting the importance of genetics in disease pathogenesis. In four families with AF, we have excluded linkage to chromosome 10q22-q24, establishing that at least two disease genes are responsible for this disorder.

Choice of pacemakers in patients aged 75 years and older: ventricular pacing mode vs. dual-chamber pacing mode.

Half of all pacemakers implanted in the United States are for patients aged 75 years and older. The expectations and needs of an older group are different from patients who are younger, yet it is only recently that different pacing mode benefits for elderly persons have been tested in clinical trials. Some of the results have been surprising and suggest new algorithms for management. Other issues are still on the threshold of investigation. These include pacing for heart failure in elderly patients and pacing combined with cardioverter-defibrillator implantation.

Ventilatory gas exchange and early response to cardiac resynchronization therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) is an accepted intervention for chronic heart failure (HF), although approximately 30% of patients are non-responders. The purpose of this study was to determine whether exercise respiratory gas exchange obtained before CRT implantation predicts early response to CRT. METHODS: Before CRT implantation, patients were assigned to either a mild-moderate group (Mod G, n = 33, age 67 ± 10 years) or a moderate-severe group (Sev G, n = 31, age 67 ± 10 years), based on abnormalities in exercise gas exchange. Severity of impaired gas exchange was based on a score from the measures of VE/VCO(2) slope, resting PETCO(2) and change of PETCO(2) from resting to peak. All measurements were performed before and 3 to 4 months after CRT implantation. RESULTS: Although Mod G did not have improved gas exchange (p > 0.05), Sev G improved significantly (p < 0.05) post-CRT. In addition, Mod G did not show improved right ventricular systolic pressure (RSVP; pre vs post: 37 ± 14 vs 36 ± 11 mm Hg, p > 0.05), yet Sev G showed significantly improved RVSP, by 23% (50 ± 14 vs 42 ± 12 mm Hg, p < 0.05). Both groups had improved left ventricular ejection fraction (p < 0.05), New York Heart Association class (p < 0.05) and quality of life (p < 0.05), but no significant differences were observed between groups (p > 0.05). No significant changes were observed in brain natriuretic peptide in either group post-CRT. CONCLUSION: Based on pre-CRT implantation ventilatory gas exchange, subjects with the most impaired values appeared to have more improvement post-CRT, possibly associated with a decrease in RVSP.

Global remodeling of the ventricular interstitium in idiopathic myocardial fibrosis and sudden cardiac death.

OBJECTIVE: Characterization of a distinct, and as yet unexplained phenotype of sudden cardiac death (SCD). BACKGROUND: In a subgroup of patients with SCD, postmortem findings are limited to isolated idiopathic myocardial fibrosis (IMF). The absence of confounding factors may facilitate evaluation of the relationship between myocardial fibrosis and ventricular arrhythmogenesis. METHODS: Six patients with IMF were identified from a postmortem, consecutive 13-year series of 270 subjects presenting with SCD. Ventricular interstitial remodeling was assessed quantitatively and qualitatively and comparisons made with 6 age- and sex-matched control subjects who suffered noncardiac death. Myocardial collagen volume fraction and perivascular fibrosis ratio were determined and evidence for inflammatory response and apoptotic cell death was sought. The potential role of transforming growth factor beta 1 (TGF-beta(1)) in the pathogenesis of IMF was evaluated. RESULTS: Overall myocardial collagen volume fraction was 1.6-fold higher in IMF (mean age 34 +/- 4 yrs) vs. controls (mean age 34 +/- 4 yrs, .022 +/- .001 vs .013 +/- .001; P < .001). Collagen volume fraction increase was diffuse but disproportionately so in the LV inferior wall (3.4-fold increase; .035 +/- .005 vs .012 +/- .018; P < .001). Perivascular fibrosis ratio was also increased (.770 +/- .014 vs .723 +/- .010; P = .007). There was no evidence of either myocardial inflammatory response or myocyte apoptosis in cases or controls. Expression of TGF-beta(1) was significantly increased in IMF vs controls. CONCLUSION: IMF involves diffuse and heterogeneous remodeling of the ventricular interstitium, with a predilection for the LV inferior wall. TGF-beta(1) is a potential mediator of interstitial remodeling in IMF and SCD.

Heart rate-dependent electrocardiogram abnormalities in patients with postural tachycardia syndrome.

We recently published data suggesting the presence of an intrinsic sinus node abnormality in a subgroup of patients with the postural tachycardia syndrome (POTS). Based on the hypothesis that more widespread abnormalities of cardiac electrophysiologic properties may be present in POTS, we undertook a study to compare cardiac conduction and repolarization at different heart rate levels in patients with POTS and healthy controls. Eleven healthy controls and fourteen patients with POTS participated in the study. Acquisition of 12-lead electrocardiogram recordings were made during supine rest and during gradual head-up tilt. The heart rate of controls was titrated by isoproterenol infusion to match the heart rate of patients. Indices for cardiac conduction (PR interval, QRS duration, and R wave axis) and repolarization (QT interval, QTc interval, and T wave axis) were then compared at different heart rate levels. The PR interval decreased with increasing heart rate in controls more than in patients, resulting in a significantly longer PR interval in patients at the fastest heart rate level. The QT and QTc intervals were significantly shorter in POTS over the entire analyzed heart rate range. The T wave axis decreased with increasing heart rate in patients only. This resulted in a significantly lower T wave axis in patients at the fastest heart rate level. Our data suggest abnormalities of atrioventricular conduction and ventricular repolarization in patients with POTS. These findings may reflect intrinsic cardiac electrophysiologic abnormalities or may be secondary due to abnormalities of cardiac autonomic innervation.

Atrial fibrillation.

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

Influence of lung volume, fluid and capillary recruitment during positional changes and exercise on thoracic impedance in heart failure.

UNLABELLED: It is unclear how dynamic changes in pulmonary-capillary blood volume (Vc), alveolar lung volume (derived from end-inspiratory lung volume, EILV) and interstitial fluid (ratio of alveolar capillary membrane conductance and pulmonary capillary blood volume, Dm/Vc) influence lung impedance (Z(T)). The purpose of this study was to investigate if positional change and exercise result in increased EILV, Vc and/or lung interstitial fluid, and if Z(T) tracks these variables. METHODS: 12 heart failure (HF) patients underwent measurements (Z(T), EILV, Vc/Dm) at rest in the upright and supine positions, during exercise and into recovery. Inspiratory capacity was obtained to provide consistent measures of EILV while assessing Z(T). RESULTS: Z(T) increased with lung volume during slow vital capacity maneuvers (p<0.05). Positional change (upright→supine) resulted in an increased Z(T) (p<0.01), while Vc increased and EILV and Dm/Vc decreased (p<0.05). Moreover, during exercise Vc and EILV increased and Dm/Vc decreased (p<0.05), whereas, Z(T) did not change significantly (p>0.05). CONCLUSION: Impedance appears sensitive to changes in lung volume and body position which appear to generally overwhelm small acute changes in lung fluid when assed dynamically at rest or during exercise.

Syncope management unit: evolution of the concept and practice implementation.

Syncope, a clinical syndrome, has many potential causes. The prognosis of a patient experiencing syncope varies from benign outcome to increased risk of mortality or sudden death, determined by the etiology of syncope and the presence of underlying disease. Because a definitive diagnosis often cannot be established immediately, hospital admission is frequently recommended as the "default" approach to ensure patient's safety and an expedited evaluation. Hospital care is costly while no studies have shown that clinical outcomes are improved by the in-patient practice approach. The syncope unit is an evolving practice model based on the hypothesis that a multidisciplinary team of physicians and allied staff with expertise in syncope management, working together and equipped with standard clinical tools could improve clinical outcomes. Preliminary data have demonstrated that a specialized syncope unit can improve diagnosis in a timely manner, reduce hospital admission and decrease the use of unnecessary diagnostic tests. In this review, models of syncope units in the emergency department, hospital and outpatient clinics from different practices in different countries are discussed. Similarities and differences of these syncope units are compared. Outcomes and endpoints from these studies are summarized. Developing a syncope unit with a standardized protocol applicable to most practice settings would be an ultimate goal for clinicians and investigators who have interest, expertise, and commitment to improve care for this large patient population.