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

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.

[Cardiopulmonary emergencies during pregnancy and the postpartum period]

The number of patients who develop cardiac problems during pregnancy are increasing and represent to date the major cause of maternal death in western countries. Pregnancy induces several changes which together increase the hemodynamic burden on the cardiovascular system and can also cause a prothrombotic state. Hence, latent or apparent cardiac disease can acutely decompensate during pregnancy. From a cardiovascular perspective, pregnancies are most often complicated by acute coronary syndromes, peripartum cardiomyopathy, arrhythmias, or pulmonary embolism. Due to potential fetal harm conventional diagnostic and therapeutic approaches are limited by the restricted use of radiogenic cardiac imaging and applicable medications. Therefore, knowledge about available therapeutic options is of greatest importance, since guideline recommendations have clearly been demonstrated to reduce morbidity and mortality in acute cardiac emergencies during pregnancy.

Risk of malignant arrhythmias in initially symptomatic patients with Wolff-Parkinson-White syndrome: results of a prospective long-term electrophysiological follow-up study

BACKGROUND

The available amount of detailed long-term data in patients with Wolff-Parkinson-White syndrome is limited, and no prospective electrophysiological studies looking at predictors of malignant arrhythmia are available.

METHODS AND RESULTS

Among 8575 symptomatic Wolff-Parkinson-White patients with atrioventricular reentrant tachycardia referred for electrophysiological test, 369 (mean age, 23±12.5 years) declined catheter ablation and were followed up. The primary end point of the study was to evaluate over a 5-year follow-up the predictors and characteristics of patients who develop malignant arrhythmias. After a mean follow-up of 42.1±10 months, malignant arrhythmias developed in 29 patients (mean age, 13.9±5.6 years; 26 male), resulting in presyncope/syncope (25 patients), hemodynamic collapse (3 patients), or cardiac arrest caused by ventricular fibrillation (1 patient). Of the remaining 340 patients, 168 (mean age, 34.2±9.0 years) remained asymptomatic up to 5 years, and 172 (mean age, 13.6±5.1 years) had benign recurrence, including sustained atrioventricular reentrant tachycardia (132 patients) or atrial fibrillation (40 patients). Compared with the group with no malignant arrhythmias, the group with malignant arrhythmias showed shorter accessory-pathway effective refractory period (P<0.001) and more often exhibited multiple accessory pathways (P<0.001), and atrioventricular reentrant tachycardia triggering sustained pre-excited atrial fibrillation was more frequently inducible (P<0.001). Multivariable analysis demonstrated that short accessory-pathway effective refractory period (P<0.001) and atrioventricular reentrant tachycardia triggering sustained pre-excited atrial fibrillation (P<0.001) were independent predictors of malignant arrhythmias.

CONCLUSIONS

Symptomatic patients with Wolff-Parkinson-White syndrome generally have a good outcome, and predictors of malignant arrhythmias are similar to those reported for asymptomatic patients with ventricular pre-excitation.

Adenosine and hypoxia-inducible factor signaling in intestinal injury and recovery

The gastrointestinal mucosa has proven to be an interesting tissue in which to investigate disease-related metabolism. In this review, we outline some of the evidence that implicates hypoxia-mediated adenosine signaling as an important signature within both healthy and diseased mucosa. Studies derived from cultured cell systems, animal models, and human patients have revealed that hypoxia is a significant component of the inflammatory microenvironment. These studies have revealed a prominent role for hypoxia-induced factor (HIF) and hypoxia signaling at several steps along the adenine nucleotide metabolism and adenosine receptor signaling pathways. Likewise, studies to date in animal models of intestinal inflammation have demonstrated an almost uniformly beneficial influence of HIF stabilization on disease outcomes. Ongoing studies to define potential similarities with and differences between innate and adaptive immune responses will continue to teach us important lessons about the complexity of the gastrointestinal tract. Such information has provided new insights into disease pathogenesis and, importantly, will provide insights into new therapeutic targets.

Economic impact to employers of treatment options for cardiac arrhythmias in the US health system

OBJECTIVE

To measure relative employer-sponsored postablation costs for cardiac arrhythmias (CA), specifically atrial fibrillation (AF).

METHODS

Regression-Controlled Employee/Spouse Database study (2001 to 2008) comparing CA patients with and without ablation and AF patients with and without ablation. Regression-adjusted monthly medical, pharmacy, sick leave, and short-term disability costs were calculated 11 months before index to 36 months after index (first ablation date or average date for nonablation patients). Relative pre/postindex comparisons between ablation and nonablation cohorts were calculated and time until ablation procedure cost recovery extrapolated.

RESULTS

Few CA (280 of 11,291; 2.48%) and AF (93 of 3062; 3.04%) patients received ablation. Ablation cohorts cost less than nonablation cohorts postablation. Estimated total ablation-period costs were recovered 38 to 50 months postablation, including employee absence payment recovery within 18 months.

CONCLUSION

Current ablation use in employer-sponsored health plans may improve health care and absence costs over time.

Acute Chest Pain and Broad Complex Tachycardia. A Non-typical Case of Pre-excited Atrial Fibrillation

Wolff-Parkinson-White syndrome is a common condition in the emergency department. A case is presented of a 76-year-old patient with acute chest pain and broad complex tachycardia. Despite the fact that previous and post cardioversion ECG tracings in sinus rhythm showed no signs of pre-excitation, the characteristic pattern of pre-excited atrial fibrillation (AF) is recognized and after successful DC cardioversion the patient is referred for catheter ablation of the accessory pathway. This case illustrates a non-typical presentation of the WPW syndrome, with an older patient than usual with slight signs of pre-excitation. We highlight the need for high grades of suspicion for the early recognition of pre-excited AF when attending patients with tachycardia and the obligation to know the distinctive aspects of its management for this potentially life-threatening arrhythmia.

Electroanatomical mapping and radiofrequency ablation of tachycardia originating in pulmonary vein in an adult patient

A 29-year-old male was admitted to our outpatient clinic because of palpitation and documented narrow QRS arrhythmia. Based on the ECG, supraventricular tachycardia was diagnosed, electrophysiological examination was indicated and ablation therapy was recommended. During positioning of the catheter the patient developed arrhythmia. On the coronary sinus catheter the activation spread from distal to proximal electrodes, suggesting left atrial origin. During atrial entrainment pacing long return cycle was observed and distal coronary sinus pacing resulted in a 15 ms longer cycle length than the arrhythmia. Therefore, the left atrial origin of the arrhythmia was confirmed and double transseptal puncture was performed. Lasso and irrigated tip catheter were introduced into the left atrium and electroanatomical mapping was performed with CARTO3 system. After electroanatomical mapping the origin of tachycardia was located proximally in the left superior pulmonary vein. Ablation was started at the earliest activation point, where acceleration was observed and the arrhythmia stopped after the first ablation. Pulmonary vein isolation was completed, and bidirectional block could be confirmed. After 30 minutes the arrhythmia was not inducible. During follow-up, Holter-examination was negative and the patient remained asymptomatic. The pulmonary vein tachycardia is a supraventricular arrhythmia that can occur at any age, but the diagnosis based on the ECG is not always simple. Detailed electroanatomical mapping is very important in the diagnosis of this type of arrhythmia, although it can be verified with conventional electrophysiological methods as well. Focal ablation may be a therapeutic option; however, total isolation of pulmonary veins can be more effective. Orv. Hetil., 2011, 152, 1374–1378.

A pediatric case of cardiomyopathy induced by inappropriate sinus tachycardia: efficacy of ivabradine

We report the case of a 16-year-old boy with cardiomyopathy induced by inappropriate sinus tachycardia (IST). The patient was resistant to treatment with conventional rate-decreasing medications. Therapy with the selective sinus node I(f) current inhibitor ivabradine was started. After 3 months of ivabradine therapy, an improvement in ejection fraction and a successful decrease in heart rate were observed. No side effects occurred. We suggest that ivabradine, currently used to treat stable angina, could be considered as a second-line treatment in patients with symptomatic and refractory IST.

EGC diagnosis of paroxysmal supraventricular tachycardias in patients without preexcitation

This review is aimed at discussing the diagnostic value of the different electrocardiographic criteria so far described in the differential diagnosis of the major forms of paroxysmal supraventricular tachycardias (PSVTs). The predictive value of different combinations of these independent electrocardiographic (ECG) signs in distinguishing atrioventricular reentrant tachycardias (AVRTs) through a concealed accessory pathway (AP) versus atrioventricular nodal reentrant tachycardias (AVNRTs) are discussed in detail. In addition, the adjunctive diagnostic value of simple, bedside clinical variables and their combinations to the ECG interpretation in differentiating both tachycardia mechanisms is also reviewed.

CARDIAC ARRHYTHMIAS DURING PREGNANCY: A CLINICAL APPROACH

Physiologic changes in maternal haemodynamics, hormones and autonomic properties contribute to arrhythmias in pregnancy. While arrhythmias most commonly occur in pregnant women with structural heart disease or those with a history of cardiac arrhythmias, they can also occur de novo in women with no documented cardiac disease.

Systematic review of pregnancy in women with inherited cardiomyopathies

Pregnancy exposes women with inherited cardiomyopathies to increased risk for heart failure and arrhythmias. In this paper, we review the clinical course and management of pregnant women with the following inherited cardiomyopathies: hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, left ventricular non-compaction cardiomyopathy, and restrictive cardiomyopathy. We also discuss peripartum cardiomyopathy. Pregnancy is generally well tolerated in asymptomatic patients with inherited cardiomyopathies. However, worsening of the clinical condition can occur during pregnancy, despite intensive medical treatment. If prior cardiac events, poor functional class (New York Heart Association class III or IV), or advanced left ventricular systolic dysfunction are present, the risk of maternal cardiac complications during pregnancy are markedly increased. The postpartum condition is generally no worse than the antepartum condition, but no long-term follow-up studies have been reported. Preconception evaluation and counselling are important aspects of managing women with inherited cardiomyopathies. Genetic counselling and DNA testing should be offered to all women following the diagnosis of an inherited cardiomyopathy.

"Near-zero" fluoroscopic exposure in supraventricular arrhythmia ablation using the EnSite NavX™ mapping system: personal experience and review of the literature

PURPOSE

Radiofrequency catheter ablation (RFCA) of supraventricular tachyarrhythmias carries a small but non-negligible radiation risk. Studies in children already showed the feasibility of using three-dimensional mapping systems as the primary guide for catheter visualization and positioning in these RFCAs. We aim to demonstrate the feasibility and safety of such an approach in young and middle-aged patients.

METHODS

Fifty patients (age 34 ± 12) with supraventricular tachyarrhythmias underwent electrophysiological study; of these, 47 patients proceeded to RFCA guided by the EnSite NavX(TM) system (23 with atrioventricular nodal reentry tachycardia, 16 with an accessory pathway, six with typical atrial flutter, and two with right atrial tachycardia).

RESULTS

In 38/50 cases (76%), electroanatomical mapping avoided fluoroscopy entirely, including four cases requiring access to the left heart chambers by a retrograde approach. In the remaining 12/50 cases (24%), fluoroscopy use was limited to 122 ± 80 s, with a correspondingly low radiation exposure (dose area product 1.3 ± 1.1 mGy × m(2)). All procedures were acutely successful, with a procedural time of 113 ± 37 minutes, and without incurring in any major complication. Over a mean follow-up of 12 ± 3 months, we observed one recurrence of pre-excitation and one relapse of atrial flutter.

CONCLUSIONS

Our study shows that non-fluoroscopic RFCA of supraventricular tachyarrhythmias using the EnSite NavX(TM) system is feasible, safe, and effective in a population of relatively young adults. Our experience of a non-fluoroscopic approach in these procedures deserves consideration, particularly in the young or in other patients at higher radiation risk.

Adenosine generation and signaling during acute kidney injury

Acute kidney injury (AKI) is among the leading causes of morbidity and mortality in hospitalized patients. Particularly in the perioperative period, the most common cause of AKI is renal ischemia. At present, therapeutic modalities to prevent or treat AKI are extremely limited and the search for novel therapeutic interventions for ischemic AKI is an area of intense investigation. Recent studies implicate the endogenous signaling molecule, adenosine, in kidney protection from ischemia. As such, enzymatic production of adenosine from its precursor molecules ATP and AMP, and signaling events through adenosine receptors, play a critical role in attenuating renal inflammation and preserving kidney function during episodes of renal ischemia. Utilizing genetic mouse models with defects in adenosine generation or signaling provide strong evidence for the key role of extracellular adenosine in adapting renal tissues to limited oxygen availability and attenuating hypoxia-driven inflammation of the kidneys. Moreover, experimental therapeutics targeting individual adenosine receptors demonstrate strong prophylactic or therapeutic effects during murine AKI. If these experimental strategies can be translated into a clinical setting, adenosine receptor therapeutics may become an integral part in the prevention or treatment of AKI from renal ischemia.

The pharmaceutical pipeline for atrial fibrillation

Atrial fibrillation (AF) is associated with a significant burden of morbidity and increased risk of mortality. Beyond outstanding advances in catheter ablation procedures, antiarrhythmic drug therapy remains a corner-stone to restore and maintain sinus rhythm. However, potentially life-threatening hazards (proarrhythmia) and significant non-cardiac organ toxicity have made new drug development of prominent relevance. Multichannel blocking, atrial selectivity, and the reduction of the risk of adverse events have all constituted the main theme of modern antifibrillatory drug development. Dronedarone, an analog of amiodarone, has the unique characteristic of being the first antiarrhythmic drug demonstrated to reduce hospitalizations in AF. Dronedarone is associated with less systemic toxicity than amiodarone, although being less effective for sinus rhythm maintenance. Atrial selective agents have been developed to target ion channels expressed selectively in the atria. Among the most promising drugs of this class is vernakalant, which has been shown effective for the acute conversion of AF with small risk of proarrhythmia. Finally, increasing evidences support antiarrhythmic effectiveness of traditional non-antiarrhythmic drugs, such as renin-angiotensin system blockers, statins, and omega-3 fatty acids. In this article, we will focus on recent advances in antiarrhythmic therapy for AF, reviewing the possible clinical utility of novel antifibrillatory agents.

Outcome of invasive electrophysiological procedures and gender: are males and females the same?

The aim of this review is to summarize the available evidence on gender-related differences in outcome of invasive electrophysiological procedures. Gender exerts significant influences on the epidemiology, pathophysiology, and clinical presentation of many cardiac rhythm disorders. Women with supraventricular arrhythmias have a higher incidence of atrioventricular nodal reentrant tachycardia, a lower prevalence of atrioventricular accessory pathways, and increased arrhythmia inducibility during luteal phases of the menstrual cycle. Catheter ablation of supraventricular arrhythmias appears equally effective in the 2 genders, although women present to catheter ablation later, with more symptoms, and after having failed more antiarrhythmic drugs. The outcome of catheter ablation of atrial fibrillation in women has been reported worse than in men, which may be explained by a later referral. Accordingly, women present to catheter ablation with a higher incidence of long-standing persistent atrial fibrillation. Of note, the outcome of catheter ablation of atrial flutter does not seem to differ between genders. To date, with regard to ventricular arrhythmias, no gender-related differences in outcome of catheter ablation procedures have been reported. However, pathophysiology and risk factors underlying ventricular arrhythmias appear different in the two genders. Severe left ventricular dysfunction does not perform equally as a predictor for sudden cardiac death in women as compared to men, and the survival benefit of prophylactic implantable cardioverter-defibrillator (ICD) implantation in women is inconclusive. On the other hand, the clinical outcome after cardiac resynchronization therapy seems to be more favorable in women, who experience a greater degree of reverse left ventricular remodeling.

Antiarrhythmic Drug Therapy of Supraventricular Tachycardia

Pharmacologic therapy is commonly used for the acute treatment and termination of paroxysmal supraventricular tachycardia (SVT) and continues to be an important long-term option for some patients. Drug choice depends on the correct diagnosis of the arrhythmia and an understanding of its mechanism. Pharmacologic agents commonly used in the acute and chronic treatment of SVT are reviewed along with their effect on the various types of SVT. Drugs that are well tolerated with minimal side effects are preferred over agents with perhaps more efficacy but higher risk of toxicity.

Concept of the five 'A's for treating emergency arrhythmias

Cardiac rhythm disturbances such as bradycardia (heart rate < 50/min) and tachycardia (heart rate > 100/min) require rapid therapeutic intervention. The supraventricular tachycardias (SVTs) are sinus tachycardia, atrial tachycardia, AV-nodal reentrant tachycardia, and tachycardia due to accessory pathways. All SVTs are characterized by a ventricular heart rate > 100/min and small QRS complexes (QRS width < 0.12 ms) during the tachycardia. It is essential to evaluate the arrhythmia history, to perform a good physical examination, and to accurately analyze the 12-lead electrocardiogram. A precise diagnosis of the SVT is then possible in more than 90% of patients. In ventricular tachycardia (VT) there are broad QRS complexes (QRS width > 0.12 s). Ventricular flutter and ventricular fibrillation are associated with chaotic electrophysiologic findings. For acute therapy, we will present the new concept of the five 'A's, which refers to adenosine, adrenaline, ajmaline, amiodarone, and atropine. Additionally, there are the 'B,' 'C,' and 'D' strategies, which refer to beta-blockers, cardioversion, and defibrillation, respectively. The five 'A' concept allows a safe and effective antiarrhythmic treatment of all bradycardias, tachycardias, SVTs, VT, ventricular flutter, and ventricular fibrillation, as well as of asystole.

Do inhaled anticholinergics increase or decrease the risk of major cardiovascular events?: a synthesis of the available evidence

There has been recent uncertainty about whether the inhaled anticholinergic agents ipratropium bromide and tiotropium bromide increase or decrease cardiovascular risk in the treatment of patients with chronic obstructive pulmonary disease (COPD). This article synthesizes the available data in order to understand the controversy. COPD is a common cause of hospitalizations and is a rapidly increasing cause of mortality worldwide. Despite the heavy burden of COPD-related illness, the leading cause of hospitalization in COPD patients is cardiovascular disease. This link between COPD and cardiovascular disease is in part due to the fact that both diseases share common risk factors, such as tobacco smoking and advanced age. It is also hypothesized that systemic inflammation in COPD increases the risk for cardiac events such as myocardial infarction. Inhaled anticholinergics reduce COPD-related hospitalizations and respiratory deaths compared with placebo, and tiotropium bromide is more effective than ipratropium bromide. In randomized trials, patients receiving tiotropium bromide have lower discontinuation rates than those receiving placebo and, therefore, contribute more person-years to the analyses. In a recent large 4-year tiotropium bromide trial, the proportion of patients who died was similar in the tiotropium bromide and placebo groups, whereas the death rate per person-years was lower with tiotropium bromide, indicating longer overall survival. There has been conflicting evidence concerning cardiovascular risk associated with inhaled anticholinergics. One meta-analysis found that the risk for major cardiovascular events was higher with anticholinergics compared with placebo or active comparator controls, whereas two subsequent meta-analyses that included new trial data found no difference in risk. In a recent pooled safety analysis, when incidence rates of events over time were evaluated, tiotropium bromide was associated with a lower rate of major cardiovascular events and cardiovascular deaths compared with placebo. This risk reduction was mainly because of a reduction in serious cardiac events such as myocardial infarction and congestive heart failure. In conclusion, inhaled anticholinergics, especially tiotropium bromide, reduce COPD-related hospitalizations and deaths, and may improve total survival over time. Many COPD patients have concomitant cardiovascular disease processes. Thus, trials may observe more cardiovascular events associated with anticholinergics than with placebo, but this differential is eliminated when evaluating the rate of events per person-years of exposure. New evidence indicates that tiotropium bromide may actually reduce the incidence of cardiovascular events and deaths over time. It is possible that the reduction in respiratory morbidity could improve functional status and reduce adverse cardiac outcomes over time. Further studies are needed to address this important issue.

Adenosine: an old drug newly discovered

Over decades, anesthesiologists have used intravenous adenosine as mainstay therapy for diagnosing or treating supraventricular tachycardia in the perioperative setting. More recently, specific adenosine receptor therapeutics or gene-targeted mice deficient in extracellular adenosine production or individual adenosine receptors became available. These models enabled physicians and scientists to learn more about the biologic functions of extracellular nucleotide metabolism and adenosine signaling. Such functions include specific signaling effects through adenosine receptors expressed by many mammalian tissues; for example, vascular endothelia, myocytes, hepatocytes, intestinal epithelia, or immune cells. At present, pharmacological approaches to modulate extracellular adenosine signaling are evaluated for their potential use in perioperative medicine, including attenuation of acute lung injury; renal, intestinal, hepatic and myocardial ischemia; or vascular leakage. If these laboratory studies can be translated into clinical practice, adenosine receptor-based therapeutics may become an integral pharmacological component of daily anesthesiology practice.

Autonomic nervous system modulation before the onset of sustained atrioventricular nodal reentry tachycardia

INTRODUCTION

Our study was designed to analyze dynamic changes in autonomic tone before the onset of typical sustained atrioventricular nodal reentry tachycardia (AVNRT) in a large group of patients without structural heart disease.

MATERIALS AND METHODS

Twenty-four-hour Holter tapes from 42 consecutive patients (27 men and 15 women; aged 30 + or - 21 years) with several episodes of sustained typical AVNRT were analyzed. The diagnosis was validated by transesophageal electrophysiological study. The time-domain calculated parameters were SDNN, SDANN, rMSSD, pNN50; the frequency-domain parameters were low-frequency power (LF, 0.04-0.15 Hz), high-frequency power (HF, 0.15-0.40 Hz), very low-frequency power (VLF, 0.008 to 0.04 Hz) and LF/HF. The mean values in the hour before the onset of sustained AVNRT were compared with the mean values of 2 hours before and 1 hour after the onset of sustained AVNRT.

RESULTS

The mean SDNN, rMSSD, pNN50, HF were significantly decreased during the hour preceding the onset of AVNRT, when compared to the mean values observed during the time periods selected. Instead, the LF values and LF/HF were increased before the onset of sustained AVNRT. No significant change in the VLF and atrial ectopic beats were observed.

CONCLUSION

This study suggests that sustained typical AVNRT episodes are preceded by increase in adrenergic drive.