ACC/AHA/ESC Guidelines for the Management of Patients With Supraventricular Arrhythmias—Executive Summary

Cardiac arrythmias: multimodal assessment integrating body surface ECG mapping into cardiac imaging

PURPOSE

To demonstrate the feasibility of comprehensive assessment of cardiac arrhythmias by combining body surface electrocardiographic (ECG) mapping (BSM) and imaging.

MATERIALS AND METHODS

This study was approved by the institutional review board, and all patients gave written informed consent. Twenty-seven patients referred for electrophysiologic procedures in the context of ventricular tachycardia (VT) (n = 9), Wolff-Parkinson-White (WPW) syndrome (n = 2), atrial fibrillation (AF) (n = 13), or scar-related ventricular fibrillation (VF) (n = 3) were examined. Patients underwent BSM and imaging with multidetector computed tomography (CT) (n = 12) and/or delayed enhanced magnetic resonance (MR) imaging (n = 23). BSM was performed by using a 252-electrode vest that enabled the computation of epicardial electrograms from body surface potentials. The epicardial geometry used for BSM was registered to the epicardial geometry segmented from imaging data by using an automatic algorithm. The output was a three-dimensional cardiac model that integrated cardiac anatomy, myocardial substrate, and epicardial activation.

RESULTS

Acquisition, segmentation, and registration were feasible in all patients. In VT, this enabled a noninvasive assessment of the arrhythmia mechanism and its location with respect to the myocardial substrate, coronary vessels, and phrenic nerve. In WPW syndrome, this enabled understanding of complex accessory pathways resistant to previous ablation. In AF and VF, this enabled the noninvasive assessment of arrhythmia mechanisms and the analysis of rotor trajectories with respect to the myocardial substrate. In all patients, models were successfully integrated in navigation systems and used to guide mapping and ablation.

CONCLUSION

By combining information on anatomy, substrate, and electrical activation, the fusion of BSM and imaging enables comprehensive noninvasive assessment of cardiac arrhythmias, with potential applications for diagnosis, prognosis, and ablation targeting. Online supplemental material is available for this article.

Cryoablation versus radiofrequency ablation of atrioventricular nodal reentrant tachycardia

BACKGROUND

Ablation of the slow pathway is an established cure for atrioventricular nodal reentrant tachycardia (AVNRT). Periprocedural damage to the conduction system is a major concern during AVNRT ablation, and cryoablation (CRYO) has been suggested to improve the procedural safety compared to standard radiofrequency (RF) ablation, without reducing the procedural success.

OBJECTIVE

We performed a systematic review and meta-analysis of studies comparing CRYO with RF ablation of AVNRT.

METHODS

We searched PubMed, CENTRAL, the BioMed Central, EMBASE, CardioSource, clinicaltrials.gov, and ISI Web of Science (January 1980 to July 2013). No language restriction was applied. Two independent reviewers screened titles and abstracts to identify studies that compared the procedural outcomes of AVNRT ablation with either CRYO or RF energy. Two independent reviewers assessed the risk of bias according to the Cochrane Collaboration, and extracted patient, study characteristics, and procedural outcome data. Results are expressed as odds ratio (OR) or as weighted mean difference (WMD) with their 95 % confidence interval (CI).

RESULTS

Fourteen studies (5 prospective randomized and 9 observational) with 2,340 patients (mean age range 13 to 53 years, 1,522 (65 %) females) were included in the analysis. RF ablation was performed in 1,262 (54 %) patients, while CRYO in 1,078 (46 %) patients. Acute success (abolition of dual atrioventricular node physiology or single echo beats) was achieved in 88 % of patients treated with RF versus 83 % of those treated with CRYO (OR = 0.72, 95 % CI 0.46 to 1.13; P = 0.157). RF ablation was associated with shorter total procedure time (WMD = -13.7 min, 95 % CI -23 to -4.3 min; P = 0.004), but slightly longer fluoroscopy time (WMD = +4.6 min 95 % CI +1.7 to +7.6 min; P = 0.002). Permanent atrioventricular block occurred in 0.87 % RF cases and in no CRYO case (OR = 3.60, 95 % CI 1.09 to 11.81; P = 0.035). Over a median follow-up of 10.5 months (range 6 to 12 months), freedom from recurrent AVNRT was 96.5 % in the RF group versus 90.9 % in the CRYO group (OR = 0.40, 95 % CI 0.28 to 0.58; P < 0.001). At meta-regression analysis, no clinical or procedural variable had a significant interaction with the results above.

CONCLUSIONS

In patients undergoing AVNRT ablation, RF significantly reduces the risk of long-term arrhythmia recurrence compared to CRYO, but is associated with a higher risk of permanent atrioventricular block.

Characterization of the impact of catheter-tissue contact force in lesion formation during cavo-tricuspid isthmus ablation in an experimental swine model

AIMS

Catheter-tissue contact is critical for effective lesion creation. The objective of this study was to determine in an experimental swine model the pathological effects of cavo-tricuspid isthmus ablation using two systems that provide reliable measures of the pressure at the catheter tip during radiofrequency ablation procedures.

METHODS AND RESULTS

We performed the procedure in eight pigs in our experimental electrophysiology laboratory after right femoral vein dissection and insertion of a 12 Fr. introducer during general anaesthesia and endotracheal intubation. The target contact force during the applications was <10 grs. (axial or lateral), 10-20, 20-30, and >30 grs. in two pigs each. The power was set at 40 W and maximum target temperature at 45°C. We performed a radiofrequency line dragging from the tricuspid valve to the inferior vena cava in the eight pigs. Euthanasia of the animals was carried out a week after the procedure and a pathological examination of the lesions was performed. In the endocardial macroscopic analysis the extent of lesions, presence of thrombus, transmurality, and endothelial rupture was assessed. External surface was examined searching for transmural lesions. The mean contact force applied was 18.7 ± 8.4 grs. and the mean depth of the lesions was 3.6 ± 2 mm. Lesions were never transmural with average forces <10 grs., and the mean depth was very low (0.75 mm). To achieve transmural lesions contact forces of at least 20 grs. were required. We found a positive correlation (r = 0.85, P < 0.05) between the average force during the applications and depth of the lesions.

CONCLUSION

When ablating the cavo-tricuspid isthmus in a swine model, contact forces of at least 20 grs. are required to achieve transmural lesions. Catheter-tissue contact is critical for effective lesion creation. This information is important for improving ablation efficacy.

Efficacy of antiarrhythmic drugs in adults with congenital heart disease and supraventricular tachycardias

Supraventricular tachycardias (SVTs) are a major cause of morbidity in adults with congenital heart disease (CHD). Few data exist on safety and efficacy of antiarrhythmic drugs in this population. Our aim was to determine the efficacy of antiarrhythmic drugs in adults with CHD and first-onset SVT on maintaining sinus rhythm after conversion. This was a multicenter retrospective study including adults with CHD and first-onset SVT from January 2008 to January 2011. First-onset SVT occurred in 92 of 7,171 patients without previous SVT (mean age 51 ± 16 years, 57% women). SVTs included atrial fibrillation and flutter in >80% of the patients. Most of these patients had septal defects (50%) and left-sided lesions (21%). The acute management of SVTs resulted in sinus rhythm in 83 patients, and 89% of these patients were instituted on oral antiarrhythmics to prevent SVT recurrence. After a mean follow-up of 2.5 ± 1.4 years, only 45% of the patients were free from SVT. Class III antiarrhythmics (85% sotalol and 15% amiodarone) were associated with a significantly lesser risk of SVT recurrence compared with all other antiarrhythmic drugs (hazard ratio 0.5, 95% confidence interval 0.27 to 0.96, p = 0.036). However, adverse effects of medication occurred in 22% of the patients, mainly in patients taking amiodarone. In conclusion, in adults with CHD and first-onset SVTs, class III antiarrhythmics are more efficacious in maintaining sinus rhythm after cardioversion than other antiarrhythmics. Sotalol may be considered as the first-choice therapy as this is associated with fewer adverse effects than amiodarone.

Supraventricular and ventricular arrhythmias

Cardiac arrhythmias comprise of a heterogeneous group of disorders which manifest in a wide range of clinical presentations. They can be associated with underlying cardiac disease and portend a grave prognosis, with some arrhythmias being rapidly fatal. Other arrhythmias, however are relatively benign and can be asymptomatic or may be a mere inconvenience for the patient. All primary care physicians can expect to encounter some forms of arrhythmias during the course of their practice. This review article provides a brief overview of the commonly seen tachyarrhythmias for the general practitioner and provides relevant updates on the recent developments in our understanding of their mechanisms and management.

Structure, function and clinical relevance of the cardiac conduction system, including the atrioventricular ring and outflow tract tissues

It is now over 100years since the discovery of the cardiac conduction system, consisting of three main parts, the sinus node, the atrioventricular node and the His-Purkinje system. The system is vital for the initiation and coordination of the heartbeat. Over the last decade, immense strides have been made in our understanding of the cardiac conduction system and these recent developments are reviewed here. It has been shown that the system has a unique embryological origin, distinct from that of the working myocardium, and is more extensive than originally thought with additional structures: atrioventricular rings, a third node (so called retroaortic node) and pulmonary and aortic sleeves. It has been shown that the expression of ion channels, intracellular Ca(2+)-handling proteins and gap junction channels in the system is specialised (different from that in the ordinary working myocardium), but appropriate to explain the functioning of the system, although there is continued debate concerning the ionic basis of pacemaking. We are beginning to understand the mechanisms (fibrosis and remodelling of ion channels and related proteins) responsible for dysfunction of the system (bradycardia, heart block and bundle branch block) associated with atrial fibrillation and heart failure and even athletic training. Equally, we are beginning to appreciate how naturally occurring mutations in ion channels cause congenital cardiac conduction system dysfunction. Finally, current therapies, the status of a new therapeutic strategy (use of a specific heart rate lowering drug) and a potential new therapeutic strategy (biopacemaking) are reviewed.

Radiofrequency catheter ablation of the accessory pathway adversely affected the left ventricular outflow tract pressure gradient in a patient with hypertrophic obstructive cardiomyopathy

Although hypertrophic cardiomyopathy (HCM) with an accessory pathway is encountered in clinical practice, there is little evidence of a coherent strategy for ablation of the accessory pathway in patients with HCM. We present the case of a 61-year-old man who had type B Wolff-Parkinson-White (WPW) syndrome with hypertrophic obstructive cardiomyopathy (HOCM). Due to paroxysmal atrial fibrillation, he underwent radiofrequency catheter ablation of the accessory pathway located in the right postero-lateral wall to prevent secondary symptomatic events. His LV dyssynchrony improved after the procedure, but the degree of the LV outflow tract (LVOT) pressure gradient was increased. To stabilize the LVOT pressure gradient, he needed additional medications. This case shows that patients with HOCM should be carefully evaluated before making a decision concerning ablation of the accessory pathway.

Access to cardiac rehabilitation does not equate to attendance

BACKGROUND/AIMS

Timely access to appropriate cardiac care is critical for optimizing positive outcomes after a cardiac event. Attendance at cardiac rehabilitation (CR) remains less than optimal (10%-30%). Our aim was to derive an objective, comparable, geographic measure reflecting access to cardiac services after a cardiac event in Australia.

METHODS

An expert panel defined a single patient care pathway and a hierarchy of the minimum health services for CR and secondary prevention. Using geographic information systems a numeric/alpha index was modelled to describe access before and after a cardiac event. The aftercare phase was modelled into five alphabetical categories: from category A (access to medical service, pharmacy, CR, pathology within 1 h) to category E (no services available within 1 h).

RESULTS

Approximately 96% or 19 million people lived within 1 h of the four basic services to support CR and secondary prevention, including 96% of older Australians and 75% of the indigenous population. Conversely, 14% (64,000) indigenous people resided in population locations that had poor access to health services that support CR after a cardiac event.

CONCLUSION

Results demonstrated that the majority of Australians had excellent 'geographic' access to services to support CR and secondary prevention. Therefore, it appears that it is not the distance to services that affects attendance. Our 'geographic' lens has identified that more research on socioeconomic, sociological or psychological aspects to attendance is needed.

Aborted sudden cardiac death as first presentation of Wolff-Parkinson-White syndrome

Sudden cardiac death (SCD) can be the first clinical manifestation of Wolff-Parkinson-White (WPW) syndrome. Catheter ablation of accessory pathways is now a safe and effective procedure, and is widely recommended in patients with WPW syndrome. However, management of the asymptomatic WPW patient remains controversial. Recent studies have readdressed the issue of risk stratification and prophylactic catheter ablation. We describe a case of malignant arrhythmia and aborted SCD as first presentation of WPW syndrome in a previously asymptomatic 17-year-old patient.

Guidelines for maintenance of adult patients with brain death and potential for multiple organ donations: the Task Force of the Brazilian Association of Intensive Medicine the Brazilian Association of Organs Transplantation, and the Transplantation Center of Santa Catarina

INTRODUCTION

The organ shortage for transplantation, the principal factor that increases waiting lists, has become a serious public health problem. In this scenario, the intensivist occupies a prominent position as one of the professionals that first has a chance to identify brain death and to be responsible for the maintenance of the potential deceased donor.

OBJECTIVE

This report attempts to establish guidelines for care and maintenance of adult deceased donor organs guiding and standardizing care provided to patients with brain death.

METHOD

These guidelines were composed by intensivists, transplant coordinators, professionals from various transplant teams, and used transplant center. The formulated questions were forwarded to all members and recommendations were constructed after an extensive literature review selecting articles with the highest degree of evidence.

RESULTS

Guidelines were developed in the form of questions reflecting frequent experiences in clinical intensive care practices. The main questions were: Is there an optimal interval for keeping organs of deceased donors viable? What actions are considered essential for maintaining deceased donors in this period? What are the limits of body temperature? How should the patient be warmed? Which laboratory tests should be performed? What is the collection interval? What are the limits in the laboratory and the capture scenario? What are the limits of blood pressure? When and how should one use catecholamines?

CONCLUSIONS

This pioneer project involved a multidisciplinary team working in organ transplantation seeking to provide treatment guidance to increase the number of viable organs from deceased adult donors.

Information on myocardial ischemia and arrhythmias added by prehospital electrocardiograms

BACKGROUND

The prehospital electrocardiogram (ECG) allows earlier identification of acute ST-segment elevation myocardial infarction (STEMI). Its utility for detection of other acute cardiac events, as well as for transient ST-segment abnormalities no longer present when the first hospital ECG is performed, is not well characterized.

OBJECTIVE

We sought to examine whether the prehospital ECG adds supplemental information to the first ECG obtained in hospital, by comparing data on possible cardiac ischemia and arrhythmias provided by the two ECGs, in ambulance patients later diagnosed as having cardiac disorders, including STEMI.

METHODS

Ambulance personnel acquired 12-lead ECGs for patients suspected of having an acute ischemic event, prior to transport to hospital. The first emergency department 12-lead ECG was provided by medical records at the receiving hospital, and the principal hospital diagnosis for the event was extracted from chart data. Two cardiologists, blinded to the hospital diagnosis, provided their consensus interpretation of 1,209 pairs of ECGs, noting the presence or absence of specific abnormalities on each tracing.

RESULTS

Among the 82 patients who had an eventual hospital diagnosis of STEMI, the study cardiologists identified 71 with ST-segment elevations on the ECGs they examined. The vast majority of these (97%) were observed on both ECGs, but the prehospital ECG showed ST-segment elevation for two additional patients (3%). No additional instances were seen only on the hospital ECG. Among the 116 patients with a hospital diagnosis of non-ST-segment elevation myocardial infarction (NSTEMI), the cardiologists identified 36 with ST-segment depressions: 28 (78%) of these were present on both ECGs, seven (19%) only on the prehospital ECG, and one (3%) only on the hospital ECG. Among the 567 patients with any cardiac hospital diagnosis, the cardiologists identified 87 with arrhythmias: 73 (84%) on both ECGs, 12 (14%) only on the prehospital ECG, and two (2%) only on the hospital ECG.

CONCLUSIONS

Beyond identifying ST-segment elevation earlier, prehospital ECGs detect important transient abnormalities, information not otherwise available from the first emergency department ECG. These data can expedite diagnosis and clinical management decisions among patients suspected of having an acute cardiac event. The prehospital ECG should be fully integrated into emergency medicine practice.

Differences in clinical and echocardiographic parameters between paroxysmal and persistent atrial flutter in the AURUM 8 study: targets for prevention of persistent arrhythmia?

PURPOSE

Cavotricuspid isthmus-dependent atrial flutter (AFL) can occur in a paroxysmal or persistent pattern. The aim of this study was to identify clinical, echocardiographic, and electrophysiological risk factors independently associated with persistence of AFL.

METHODS

Patients of the recently published AURUM 8 study with paroxysmal versus persistent AFL were compared with respect to clinical and echocardiographic baseline characteristics as well as procedural parameters. The AURUM 8 study is a randomized, multicenter clinical trial comparing the efficacy and safety of gold versus platinum-iridium 8-mm-tip ablation. AFL was paroxysmal in 218 patients and persistent in 210 patients.

RESULTS

Univariate analysis revealed that patients with persistent AFL had higher New York Heart Association class (P = 0.002), shorter time since 1st AFL episode (median 0.18 vs 0.34, P = 0.037), a higher prevalence of previous coronary artery bypass grafting surgery (17% vs 9%, P = 0.02), left ventricular hypertrophy (17% vs 8%, P = 0.005), dyspnea during AFL (P < 0.001), mitral regurgitation (P = 0.002), tricuspid regurgitation (P = 0.049), and pulmonary hypertension (P = 0.01). Palpitations during AFL were less frequent in patients with persistent AFL (P = 0.001). Multivariate analysis revealed that age, weight, AFL diagnosis after initiation of class IC or III antiarrhythmic drugs for atrial fibrillation, history of left ventricular hypertrophy, dyspnea during AFL and mitral regurgitation on echocardiography were significant independent variables associated with persistent AFL. A history of atrial fibrillation and palpitations during AFL were independently associated with paroxysmal AFL.

CONCLUSIONS

We were able to identify clinical and echocardiographic risk factors associated with persistence of typical AFL. Treatment of these risk factors can potentially not only prevent the transition from paroxysmal to persistent AFL, but maybe also the development or initiation of AFL in general.

Prophylactic Radiofrequency Ablation in Asymptomatic Patients With Wolff–Parkinson–White Is Not Yet a Good Strategy

Background—

Therapeutic management of asymptomatic patients with a Wolff–Parkinson–White (WPW) pattern is controversial. We compared the risk:benefit ratios between prophylactic radiofrequency ablation and no treatment in asymptomatic patients with WPW.

Methods and Results—

Decision analysis software was used to construct a risk–benefit decision tree. The target population consisted of 20- to 40-year-old asymptomatic patients with WPW without structural fatal heart disease or a family history of sudden cardiac death. Baseline estimates of sudden death and radiofrequency ablation complication rates were obtained from the literature, an empirical data survey, and expert opinion. The outcome measure was death within 10 years. Sensitivity analyses determined the variables that significantly impacted the decision to ablate or not. Threshold analyses evaluated the effects of key variables and the optimum policy. At baseline, the decision to ablate resulted in a reduction of mortality risk of 8.8 patients for 1000 patients compared with abstention. It is necessary to treat 112 asymptomatic patients with WPW to save one life over 10 years. Sensitivity analysis showed that 3 variables significantly impacted the decision to ablate: (1) complication of radiofrequency ablation, (2) success of radiofrequency ablation, and (3) sudden death in asymptomatic patients with WPW.

Conclusions—

This study provides a decision aid for treating asymptomatic patients with the WPW ECG pattern. Using the model and the population we tested, prophylactic catheter ablation is not yet ready for widespread clinical use.

Severity of nocturnal cardiac arrhythmias correlates with intensity of sleep apnea in men

Various cardiac arrhythmias frequently occur in patients with sleep apnea, but complex analysis of the relationship between their severity and the probable arrhythmogenic risk factors is conflicting. The question is what cardiovascular risk factors and how strongly they are associated with the severity of cardiac arrhythmias in sleep apnea. Adult males (33 with and 16 without sleep apnea), matched for cardiovascular co-morbidity were studied by polysomnography with simultaneous ECG monitoring. Arrhythmia severity was evaluated for each subject by a special 7-degree scoring system. Laboratory, clinical, echocardiographic, carotid ultrasonographic, ambulatory blood pressure, and baroreflex sensitivity values were also assessed. Moderate sleep apnea patients had benign, but more exaggerated cardiac arrhythmias than control subjects (2.53 ± 2.49 vs. 1.13 ± 1.64 degrees of cumulative severity, p < 0.05). We confirmed strong correlations between the arrhythmia severity and known arrhythmogenic risk factors (left ventricular ejection fraction and dimensions, right ventricular diameter, baroreflex sensitivity, carotid intima-media thickness, age, previous myocardial infarction, and also apnea-hypopnea index). In multivariate modelling only the apnea-hypopnea index indicating the sleep apnea intensity remained highly significantly correlated with the cumulative arrhythmia severity (beta = 0.548, p < 0.005). In conclusion, sleep apnea modifying cardiovascular risk factors and structures or functions provoked various nocturnal arrhythmias. The proposed scoring system allowed a complex analysis of the contribution of various triggers to arrhythmogenesis and confirmed the apnea-hypopnea index as an independent risk for nocturnal cardiac arrhythmia severity in sleep apnea.

Electrophysiological predictors of propafenone efficacy in prevention of atrioventricular nodal re-entrant and atrioventricular re-entrant tachycardia

Aim

To assess the efficacy of propafenone in prevention of atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic atrioventricular tachycardia (AVRT) based on the clinical results of arrhythmia recurrence and find the electrophysiological predictor of propafenone effectiveness.

Methods

This retrospective study included 44 participants in a 12-month period, who were divided in two groups: group A – in which propafenone caused complete ventriculo-atrial block and group B – in which propafenone did not cause complete ventriculo-atrial block.

Results

Group A had significantly lower incidence of tachycardia than group B (95% vs 70.8%, P = 0.038), and complete ventriculo-atrial block predicted the efficacy of propafenone oral therapy in the prevention of tachycardia (sensitivity 87.5%, specificity 52.8%, positive predictive value 95%, negative predictive value 29.2%). Patients with AVNRT in group B who did not experience the recurrences of tachycardia had significantly shorter echo zone before intravenous administration of propafenone than the patients who experienced episodes of sustained tachycardia (median 40 ms [range 15-60 ms] vs 79 ms [range 50-180 ms], P = 0.008).

Conclusion

In patients with non-inducible tachycardia, complete ventriculo-atrial block can be used as an electrophysiological predictor of the efficacy of propafenone oral therapy in the prevention of tachycardia. In patients with non-inducible AVNRT, but without complete ventriculo-atrial block, propafenone was more effective in patients with shorter echo zone of tachycardia.

[The electrophysiology of Wolff-Parkinson-White in the asymptomatic patient with activity or with high professional risk]

OBJECTIVE

Describe the electrophysiological characteristics in subjects with asymptomatic Wolff-Parkinson-White with sports activities or high professional responsibility.

METHODS

Nineteen subjects, mean age 33 ± 13 years (group A). The electrophysiological characteristics were compared with a matched group with symptomatic WPW (group B).

RESULTS

At baseline the anterograde refractory period and the anterograde conduction 1:1 over the accessory pathway were longer in group A (300 ± 48 ms vs 262 ± 32 ms, p < 0.05 and 355 ± 108 ms vs 307 ± 86 ms, p < 0.05), respectively. None of group A had a anterograde refractory period< 250 ms and 58% showed absence of retrograde conduction over the accessory pathway vs 4% of group B (p < 0.001). Induction of tachycardia was significantly less in group A (5%) than in group B (92%) (p < 0.001). Atrial fibrillation was induced in only one of group A vs 32% of group B (p < 0.001).

CONCLUSION

We confirm the benign electrophysiological characteristics in asymptomatic compared to symptomatic subjects. Poor anterograde conduction along with absence of retrograde conduction explains the low frequency of tachyarrhythmias and would not support the routine investigation of all asymptomatic subjects. But, due to possible consequences, remains the systematic indication for preventive ablation in the subgroup of asymptomatic subjects with sporting activities or high professional responsibility.

Cardiovascular disasters in pregnancy

Cardiovascular emergencies in pregnancy are rare but often catastrophic. This article reviews the diagnosis and management of venous thromboembolism, aortic dissection, acquired heart disease and cardiomyopathy, acute myocardial infarction, and cardiac dysrhythmias in the setting of pregnancy. It also reviews updated resuscitation guidelines for cardiac arrest and perimortem cesarean section.

Serious Cardiac Arrhythmias After Stroke

Background and Purpose—

Patients with acute cerebrovascular events are susceptible to serious cardiac arrhythmias, but data on the time course and the determinants of their onset are scarce.

Methods—

The prospective Stroke-Arrhythmia-Monitoring-Database (SAMBA) assessed cardiac arrhythmias with need for urgent evaluation and treatment in 501 acute neurovascular patients during the first 72 hours after admission to a monitored stroke unit. Arrhythmias were systematically detected by structured processing of telemetric data. Time of arrhythmia onset and predisposing factors were investigated.

Results—

Significant cardiac arrhythmias occurred in 25.1% of all patients. Incidence was highest during the first 24 hours after admission. Serious arrhythmic tachycardia (ventricular or supraventricular >130 beats/min) was more frequent than bradycardic arrhythmia (sinus-node dysfunction, bradyarrhythmia, or atrioventricular block °II and °III). Arrhythmias were independently associated with higher age and severer neurological deficits as measured by the National Institutes of Health Stroke Scale on admission.

Conclusions—

The risk for significant cardiac arrhythmia after an acute cerebrovascular event is highest during the first 24 hours of care and declines with time during the first 3 days. Along with established vascular risk factors, the National Institutes of Health Stroke Scale may be considered for a stratified allocation of monitoring capabilities.

Clinical Trial Registration—

URL: www.clinicaltrials.gov . Unique identifier: NCT01177748.

Diagnosis and management of sudden death in children

PURPOSE OF REVIEW

Sudden death is a leading cause of death in industrialized nations. Sudden death in children represents a relatively small proportion of sudden death in the population, but has devastating effects on families and communities, and often attracts significant attention.

RECENT FINDINGS

Several recent studies show that a portion of previously unexplained sudden death in children is due to cardiac conditions which are potentially identifiable by 'molecular autopsy' or investigation of family members. As some of these conditions that may present with sudden death can be detected by ECG, the controversial role of screening asymptomatic children will be discussed, as will the question of increased risk associated with stimulant medications. Recent pharmacologic and nonpharmacologic advancements for those with identifiable conditions at increased risk of sudden death will be reviewed.

SUMMARY

Recent developments have refined our understanding of the various causes of sudden death in children. Post-mortem genetic testing and/or investigation of family members can be fruitful in determining a cause and identifying at-risk relatives. Given the available and potential treatments for specific disorders with increased risk of sudden death, the benefit of identifying such disorders early is clear. The debate regarding universal ECG screening is social and political, as well as scientific.

Rationale and design of the NO-PARTY trial: near-zero fluoroscopic exposure during catheter ablation of supraventricular arrhythmias in young patients

INTRODUCTION

Radiofrequency catheter ablation is the mainstay of therapy for supraventricular tachyarrhythmias. Conventional radiofrequency catheter ablation requires the use of fluoroscopy, thus exposing patients to ionising radiation. The feasibility and safety of non-fluoroscopic radiofrequency catheter ablation has been recently reported in a wide range of supraventricular tachyarrhythmias using the EnSite NavX™ mapping system. The NO-PARTY is a multi-centre, randomised controlled trial designed to test the hypothesis that catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system results in a clinically significant reduction in exposure to ionising radiation compared with conventional catheter ablation.

METHODS

The study will randomise 210 patients undergoing catheter ablation of supraventricular tachyarrhythmias to either a conventional ablation technique or one guided by the EnSite NavX™ mapping system. The primary end-point is the reduction of the radiation dose to the patient. Secondary end-points include procedural success, reduction of the radiation dose to the operator, and a cost-effectiveness analysis. In a subgroup of patients, we will also evaluate the radiobiological effectiveness of dose reduction by assessing acute chromosomal DNA damage in peripheral blood lymphocytes.

CONCLUSIONS

NO-PARTY will determine whether radiofrequency catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system is a suitable and cost-effective approach to achieve a clinically significant reduction in ionising radiation exposure for both patient and operator.

Asymptomatic Wolff-Parkinson-White Syndrome: Who Should Be Treated?

This article discusses the merits of electrophysiology study (EPS) and/or ablation for asymptomatic preexcitation Wolff-Parkinson-White (WPW) ECG pattern. Sudden deaths in asymptomatic patients are too few to merit broad screening and aggressive intervention. It also discusses the risks of ablation and the low predictive accuracy of EPS. When WPW is an incidental finding, the decision to proceed with investigation and ablation can be made considering patients' situations and preferences. An invasive strategy is targeted at patients concerned about the low risk of life-threatening arrhythmia as a first presentation after a discussion of the risks and benefits.

Asymptomatic Wolff-Parkinson-White Syndrome Should be Ablated

Wolff-Parkinson-White syndrome (WPW) is associated with a small but lifetime risk of cardiac arrest and/or sudden cardiac death (SCD). However, the exact risk is not well defined, particularly in asymptomatic persons. Over recent years the authors have collected and reported new follow-up data among a large number of asymptomatic WPW patients, particularly children, intensively followed. These data have significantly contributed to the knowledge and definition of the natural history of WPW from childhood to adulthood. The risk of SCD is higher in asymptomatic children than in adults, and early ablation can be offered only to selected subjects after electrophysiologic testing.

Acute adenosine increases cardiac vagal and reduces sympathetic efferent nerve activities in rats

Adenosine is the first drug of choice in the treatment of supraventricular arrhythmias. While the effects of adenosine on sympathetic nerve activity (SNA) have been investigated, no information is available on the effects on cardiac vagal nerve activity (VNA). We assessed in rats the responses of cardiac VNA, SNA and cardiovascular variables to intravenous bolus administration of adenosine. In 34 urethane-anaesthetized rats, cardiac VNA or cervical preganglionic sympathetic fibres were recorded together with ECG, arterial pressure and ventilation, before and after administration of three doses of adenosine (100, 500 and 1000 μg kg(-1)). The effects of adenosine were also assessed in isolated perfused hearts (n = 5). Adenosine induced marked bradycardia and hypotension, associated with a significant dose-dependent increase in VNA (+204 ± 56%, P < 0.01; +275 ± 120%, P < 0.01; and +372 ± 78%, P < 0.01, for the three doses, respectively; n = 7). Muscarinic blockade by atropine (5 mg kg(-1), i.v.) significantly blunted the adenosine-induced bradycardia (-56.0 ± 4.5%, P < 0.05; -86.2 ± 10.5%, P < 0.01; and -34.3 ± 9.7%, P < 0.01, respectively). Likewise, adenosine-induced bradycardia was markedly less in isolated heart preparations. Previous barodenervation did not modify the effects of adenosine on VNA. On the SNA side, adenosine administration was associated with a dose-dependent biphasic response, including overactivation in the first few seconds followed by a later profound SNA reduction. Earliest sympathetic activation was abolished by barodenervation, while subsequent sympathetic withdrawal was affected neither by baro- nor by chemodenervation. This is the first demonstration that acute adenosine is able to activate cardiac VNA, possibly through a central action. This increase in vagal outflow could make an important contribution to the antiarrhythmic action of this substance.

Dexmedetomidine: therapeutic use for the termination of reentrant supraventricular tachycardia

OBJECTIVES

The current drug of choice for reentrant supraventricular tachycardia (SVT) is adenosine followed by verapamil or diltiazem. Although limitations and significant adverse events have been encountered over the years, an alternative effective and safe agent has not been available. Dexmedetomidine has recently been shown to have potential antiarrhythmic effects, and here we describe our experience in the acute termination of reentrant SVT.

DESIGN

Retrospective case series.

SETTING

Quaternary University Children's Hospital, Cardiac Intensive Care Unit.

PATIENTS

Patients who received dexmedetomidine for SVT in the past 5 years.

INTERVENTIONS

None.

OUTCOME MEASURES

SVT episodes terminated with dexmedetomidine were compared with episodes terminated with adenosine.

RESULTS

Fifteen patients, median age of 10 days (6-16), were given 27 doses of dexmedetomidine, mean dose 0.7 ± 0.3 mcg/kg, for a total of 27 episodes of SVT. Successful termination occurred in 26 episodes (96%) at a median time of 30 seconds (20-35). Duration of sinus pause was 0.6 ± 0.2 seconds, there was one episode of hypotension and no bradycardia and sedation lasted for 34 ± 8 minutes. Five patients received 27 doses of adenosine, with an overall successful cardioversion in 17 patients (63%) (P= .0017). Transient bradycardia and hypotension was seen in three patients (11%), agitation in 16 patients (59%), and broncospasm in one patient. Median sinus pause was 2.5 seconds (2-9) (P < .001).

CONCLUSIONS

Dexmedetomidine appears to have novel antiarrhythmic properties for the acute termination of reentrant SVT. Although adenosine is very effective, dexmedetomidine may prove to possess a more favorable therapeutic profile with increased effectiveness and fewer side effects.

Risk of Arrhythmia and Sudden Death in Patients With Asymptomatic Preexcitation

Background—

The incidence of sudden cardiac death (SCD) and the management of this risk in patients with asymptomatic preexcitation remain controversial. The purpose of this meta-analysis was to define the incidence of SCD and supraventricular tachycardia in patients with asymptomatic Wolff-Parkinson-White ECG pattern.

Methods and Results—

We performed a systematic search of prospective, retrospective, randomized, or cohort English-language studies in EMBASE and Medline through February 2011. Studies reporting asymptomatic patients with preexcitation who did not undergo ablation were included. Twenty studies involving 1869 patients met our inclusion criteria. Participants were primarily male with a mean age ranging from 7 to 43 years. Ten SCDs were reported involving 11 722 person-years of follow-up. Seven studies originated from Italy and reported 9 SCDs. The risk of SCD is estimated at 1.25 per 1000 person-years (95% confidence interval [CI], 0.57–2.19). A total of 156 supraventricular tachycardias were reported involving 9884 person-years from 18 studies. The risk of supraventricular tachycardia was 16 (95% CI, 10–24) events per 1000 person-years of follow-up. Children had numerically higher SCD (1.93 [95% CI, 0.57–4.1] versus 0.86 [95% CI, 0.28–1.75]; P =0.07) and supraventricular tachycardia (20 [95% CI, 12–31] versus 14 [95% CI, 6–25]; P =0.38) event rates compared with adults.

Conclusion—

The low incidence of SCD and low risk of supraventricular tachycardia argue against routine invasive management in most asymptomatic patients with the Wolff-Parkinson-White ECG pattern.

LV dyssynchrony as assessed by phase analysis of gated SPECT myocardial perfusion imaging in patients with Wolff-Parkinson-White syndrome

PURPOSE

The purpose of this study was to evaluate left ventricular (LV) mechanical dyssynchrony in patients with Wolff-Parkinson-White (WPW) syndrome pre- and post-radiofrequency catheter ablation (RFA) using phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).

METHODS

Forty-five WPW patients were enrolled and had gated SPECT MPI pre- and 2-3 days post-RFA. Electrophysiological study (EPS) was used to locate accessory pathways (APs) and categorize the patients according to the AP locations (septal, left and right free wall). Electrocardiography (ECG) was performed pre- and post-RFA to confirm successful elimination of the APs. Phase analysis of gated SPECT MPI was used to assess LV dyssynchrony pre- and post-RFA.

RESULTS

Among the 45 patients, 3 had gating errors, and thus 42 had SPECT phase analysis. Twenty-two patients (52.4%) had baseline LV dyssynchrony. Baseline LV dyssynchrony was more prominent in the patients with septal APs than in the patients with left or right APs (p < 0.05). RFA improved LV synchrony in the entire cohort and in the patients with septal APs (p < 0.01).

CONCLUSION

Phase analysis of gated SPECT MPI demonstrated that LV mechanical dyssynchrony can be present in patients with WPW syndrome. Septal APs result in the greatest degree of LV mechanical dyssynchrony and afford the most benefit after RFA. This study supports further investigation in the relationship between electrical and mechanical activation using EPS and phase analysis of gated SPECT MPI.

Application of Geographic Modeling Techniques to Quantify Spatial Access to Health Services Before and After an Acute Cardiac Event

Background

Access to cardiac services is essential for appropriate implementation of evidence-based therapies to improve outcomes. The Cardiac Accessibility and Remoteness Index for Australia (Cardiac ARIA) aimed to derive an objective, geographic measure reflecting access to cardiac services.

Methods and Results

An expert panel defined an evidence-based clinical pathway. Using Geographic Information Systems (GIS), the team developed a numeric/alphabetic index at 2 points along the continuum of care. The acute category (numeric) measured the time from the emergency call to arrival at an appropriate medical facility via road ambulance. The aftercare category (alphabetic) measured access to 4 basic services (family doctor, pharmacy, cardiac rehabilitation, and pathology services) when a patient returned to his or her community. The numeric index ranged from 1 (access to principal referral center with cardiac catheterization service ≤1 hour) to 8 (no ambulance service, >3 hours to medical facility, air transport required). The alphabetic index ranged from A (all 4 services available within a 1-hour drive-time) to E (no services available within 1 hour). The panel found that 13.9 million Australians (71%) resided within Cardiac ARIA 1A locations (hospital with cardiac catheterization laboratory and all aftercare within 1 hour). Those outside Cardiac 1A were overrepresented by people >65 years of age (32%) and indigenous people (60%).

Conclusions

The Cardiac ARIA index demonstrated substantial inequity in access to cardiac services in Australia. This methodology can be used to inform cardiology health service planning and could be applied to other common disease states within other regions of the world.