Differential Diagnosis of Supraventricular Tachycardia

Paroxysmal Tachycardia Diagnosed by ECG247 Smart Heart Sensor in a Previously Healthy Child

Supraventricular tachycardia (SVT) is the most common symptomatic heart rhythm disorder in children and adolescents. ECG recordings of the heart rhythm during episodes is necessary for the diagnosis and for the selection of treatment. However, conventional long-term ECG recording systems may miss the diagnosis due to the disease's intermittent nature. Novel adhesive patch ECG monitors, like ECG247 Smart Heart Sensor, may represent new important diagnostic tools in children and adolescents with symptoms of heart rhythm disorders. We report a case of tachyarrhythmia in a previously healthy 12-year-old child.

Incessant Focal Atrial Tachycardia Leading to Tachycardiomyopathy

A 22-year-old man presented with severe left ventricular (LV) dysfunction and progressive heart failure. The 12-lead electrocardiogram showed short runs of supraventricular tachycardia suggestive of focal atrial tachycardia. The patient underwent successful radiofrequency ablation. There was a complete recovery of symptoms and LV function at six months of follow-up. We discuss the importance of identifying tachycardiomyopathy as a reversible cause of heart failure.

Syncope and Palpitations: A Review

Syncope and palpitations are common complaints for patients presenting to their primary care provider. They represent symptoms that most often have a benign etiology but rarely can be the first warning sign of a serious condition, such as arrhythmias, structural heart disease, or noncardiac disease. The history, physical examination, and noninvasive testing can, in most cases, distinguish benign from pathologic causes. This article introduces syncope and palpitations, with emphasis on the differential diagnoses, initial presentation, diagnostic strategy, and various management strategies.

Permanent junctional reciprocating tachycardia in infants and Children

Permanent junctional reciprocating tachycardia (PJRT) is a rare form of supraventricular tachycardia (SVT). It generally presents in infants but can be difficult to diagnose. The characteristic EKG findings, response to Adenosine and persistence or frequent recurrences are helpful in making the diagnosis. It is usually difficult to manage with the initial and single medications used in SVT. Many patients are misdiagnosed and not treated effectively and end up having end stage cardiomyopathy and are diagnosed in patients referred for transplant. Hence all patients referred for a cardiac transplant with dilated cardiomyopathy need to be evaluated for this arrhythmia. If appropriate treatment is started early in the course, the failure can be ameliorated, and the cardiomyopathy can be resolved.

Principles of differential diagnostic pacing maneuvers: serial versus parallel conduction

In this article we will review differential diagnostic pacing maneuvers. It is not meant to be an exhaustive review of all such maneuvers. Rather, we offer some general analytic principles as they apply to electrophysiology (EP) and illustrate their use through several examples. Our hope is to provide a framework for thinking about electrogram data that acts more like a compass and map than like a specific set of directions. Amongst the most helpful pieces of advice that we can offer the EP trainee is to actively try to picture the waves of electricity spreading through the heart, passing beneath the recording electrodes and generating the electrograms you seek to interpret. Digest the fact that more than one propagation pattern can result in the same electrogram pattern and that differential diagnostic pacing is aimed at distinguishing between these possibilities. A fundamental tenet of differential diagnostic maneuvers of any kind (not simply pacing) is to choose a test that maximizes the difference between possible explanations. This perspective and a careful and meticulous cataloguing of what you can unambiguously conclude from the electrograms versus what remains to be determined via pacing offers the best approach to succeeding at EP. We will discuss pacing maneuvers in three contexts: differential diagnosis of narrow complex tachycardia, mapping of accessory pathways, and Para-Hisian pacing.

Patient with Long RP Tachycardia

This article discusses the case of a 50-year-old man who presented with a history of palpitations and was diagnosed with long RP tachycardia.

Patient perception of symptoms and quality of life following ablation in patients with supraventricular tachycardia

OBJECTIVES

It remains unclear which symptom experiences and aspects of quality of life (QOL) change after ablation in patients with supraventricular tachycardia (SVT). To determine how patient perceptions of symptoms and QOL change after ablation, we used a single group pretest-posttest design.

METHODS

Patients with SVT (n=52; mean age 41+/-17 years; 65% female) completed generic and disease-specific measures at baseline and 1 month after ablation.

RESULTS

Significant improvement after ablation was noted on virtually all measures (P <.05). Patients reported decreases from baseline regarding frequency and duration of episodes, number of symptoms, and impact of SVT on routine activities. All symptoms decreased in prevalence; however, no symptoms were completely eliminated at 1-month follow-up. Women, more so than men, reported larger changes in symptom and QOL scores after ablation.

CONCLUSIONS

Despite the small sample, statistically significant improvement was found after ablation in a variety of patients with different symptoms and QOL indices.

Atrioventricular nodal reentrant tachycardia with 2:1 block in pediatric patients

BACKGROUND

Episodic 2:1 block occurs in 9% of adults with atrioventricular nodal reentry tachycardia (AVNRT), but developmental differences in conduction physiology among children could influence this phenomenon.

OBJECTIVE

This study sought to characterize the frequency and mechanism of 2:1 block during AVNRT in the pediatric population.

METHODS

Records of 179 patients (mean age 13.5 +/- 3.4 years) undergoing ablation for AVNRT were reviewed.

RESULTS

Periods of 2:1 AVNRT were observed in 31 cases (17%). A His potential was visible on the blocked beats of 13, absent in 17, and undetermined in 1. Compared with 148 patients with exclusive 1:1 conduction, those with 2:1 AVNRT had: (1) longer baseline slow pathway refractory period (351 +/- 71 msec vs. 278 +/- 65 msec, P =.04), (2) shorter atrial cycle length during AVNRT (303 +/- 54 msec vs. 333 +/- 62 msec, P =.01), and (3) a higher incidence of bundle-branch aberration (35% vs. 18%, P =.03). Long-short oscillations in atrial cycle length were observed in 55% of patients during 2:1 AVNRT, but not during 1:1 AVNRT.

CONCLUSION

A pattern of 2:1 block occurs in 17% of pediatric patients with AVNRT undergoing ablation. Although this incidence is higher than in older patients, the mechanism appears identical. These data provide further evidence that functional block within or below the His bundle is the mechanism of 2:1 AVNRT, regardless of the presence of a His potential. Oscillations in atrial cycle length are common during 2:1 AVNRT in children and may contribute to the block pattern, but are not a requisite.

Electrophysiologic and electrocardiographic characteristics of focal atrial tachycardia arising from superior tricuspid annulus

OBJECTIVES

This study describes the electrophysiologic and electrocardiographic characteristics of focal atrial tachycardia (AT) arising from superior tricuspid annulus in six (1.9%) patients of a consecutive series of 320 patients.

METHODS

Six patients (mean age 42 +/- 22 years) with a mean cycle length of 326 ms of a consecutive series of 320 patients undergoing radiofrequency ablation for focal AT were mapped.

RESULTS

During electrophysiologic study, tachycardia could be induced in five patients with programmed atrial extrastimuli while a spontaneous onset and offset with 'warm-up and cool-down' phenomenon was seen in the other patient. During tachycardia, P-wave morphology in Lead I, II, III and aVF was upright in all the six patients. The precordial leads were dominantly negative or isoelectric in V(1)-V(2) and positive in V(5)-V(6) with a transition at V(3) or V(4). Moreover, the tachycardia was sensitive to intravenous administration of adenosine triphosphate in five of six patients.

CONCLUSIONS

Radiofrequency ablation was performed successfully in all patients (mean 4.5 +/- 1.2 applications). No recurrence of AT was observed after a mean follow-up of 8 +/- 6 months. Thus, AT arising from superior tricuspid annulus is rare. Radiofrequency ablation of this kind of AT is safe and effective.

Supraventricular tachycardia and the struggle to be believed

BACKGROUND

Little research exists examining patient experiences of life with supraventricular tachycardia (SVT). Realistic expectations of symptoms, patient management strategies, and treatment options are important components of patient education and treatment decisions.

AIM

This descriptive qualitative study explored patients' experiences living with SVT.

METHODS

Grounded theory methodology was used with semi-structured interviews of 25 SVT patients undergoing radiofrequency ablation treatment.

RESULTS

The main core category that emerged from the data was the "struggle to be believed". The struggle or work of living with SVT entails: (1) living with the uncertainty of the occurrence and duration of an episode, (2) "covering up" to manage symptoms and appear normal, (3) searching for causative factors to prevent further episodes, and (4) experimenting with management techniques to shorten or end episodes.

CONCLUSION

Clinical diagnosis and referral for ablation treatment were more difficult for women suggesting existence of a gender bias. As with many other chronic conditions, the illness trajectory work is formidable. Patients in this study with SVT, however, reported facing the additional difficulty of being believed. Disruptions in self-esteem and personal relationships are the effects of not being believed. Providers could avoid minimizing women's symptoms by listening seriously and offering realistic expectations; including insight into patient experiences and the trajectory of the dysrhythmia; and efficacy of drug and ablation treatments.

Focal Atrial Tachycardia I: Clinical Features, Diagnosis, Mechanisms, and Anatomic Location

Atrial tachycardia (AT) may be focal or macroreentrant. In this review we will concentrate on focal AT. The diagnosis of focal AT may be made from a standard electrocardiogram (ECG); however, in some cases differentiation from other forms of supraventricular tachycardia may be difficult. Focal AT may be due to several different mechanisms, including abnormal automaticity, triggered activity, and microreentry. Focal AT does not occur randomly throughout the atria but has a characteristic anatomic distribution. In this review, we particularly focus on the clinical features, diagnosis, mechanisms, and anatomic location of focal AT.

Palpitations: A proper evaluation and approach to effective medical therapy

Palpitations are a common complaint seen in the outpatient setting and the vast majority are benign, although they are occasionally a manifestation of potentially life-threatening conditions. We offer a step-wise guide to the evaluation and management of these patients with the primary goal to identify patients at highest risk for serious arrhythmias. We offer a brief overview of effective management of the varied causes of palpitations.

Electrophysiologic characteristics of verapamil-sensitive atrial tachycardia originating from the atrioventricular annulus

We examined the electrophysiologic characteristics and mechanisms of verapamil-sensitive atrial tachycardia (AT) originating from the atrioventricular (AV) annulus in 18 patients. AT originated from the AV node vicinity (AV nodal AT, 10 patients) and the area distant from the AV node (non-AV nodal AT, 8 patients). There was no significant difference in the tachycardia cycle length between AV nodal and non-AV nodal AT. For both types of AT, tachycardia was inducible by atrial extrastimulation with an inverse relation between the coupling and the postpacing intervals. A single extrastimulus delivered from the earliest atrial activation site reset both ATs with an inverse relation between the coupling interval and return cycle. Also no significant difference was observed in the percentage of the excitable gap to tachycardia cycle length between AV nodal and non-AV nodal AT. Concealed entrainment was observed by rapid atrial pacing delivered from the earliest atrial activation site for both ATs. These findings suggest that these ATs are due to reentry. Intravenous administration of verapamil (2.5 to 5 mg) and adenosine triphosphate (5 mg) terminated AT in all patients. AT was successfully ablated at the earliest atrial activation site in all patients. It was shown that this form of AT in which a calcium channel-dependent substrate is involved arises not only from the vicinity of the AV node but also along the AV annulus with common electrophysiologic characteristics. These suggest the presence of a distinct entity of tachycardia more appropriately classified as verapamil-sensitive AV annular AT.

Clinical and electrophysiologic characteristics of left septal atrial tachycardia

OBJECTIVES

It was the purpose of this study to define the electrophysiologic (EP) identity of left septal atrial tachycardia (AT).

BACKGROUND

The clinical and EP characteristics of this particular type of arrhythmia have not been fully described.

METHODS

A total of 120 patients with AT underwent invasive EP evaluation. Five patients (two men and three women; mean age 49 +/- 15 years) with left septal AT were identified. Mapping of the right and left atrium was performed using conventional electrode catheters (five patients) and a three-dimensional electroanatomic mapping system (three patients) followed by radiofrequency (RF) ablation at the earliest site of local endocardial activation.

RESULTS

Five tachycardias with a mean cycle length of 320 +/- 94 ms were mapped, and the earliest endocardial electrogram occurred 22 +/- 10 ms before the onset of the surface P-wave. Three left septal ATs were found to be originating from the left inferoposterior atrial septum and two from the left midseptum. During tachycardia, positive (three patients), biphasic negative-positive deflection (one patient), or isoelectric (one patient) P waves were recorded in lead V(1). The inferior leads demonstrated a positive or biphasic P-wave morphology in four of five patients (80%). Four patients were given both adenosine and verapamil during AT. In three of four patients, verapamil successfully terminated AT after adenosine had failed. Adenosine successfully terminated AT in one of four patients. Successful RF ablation was performed in all patients (mean 2.2 +/- 1.7 RF applications) without affecting atrioventricular conduction properties. No recurrence of AT was observed after a mean follow-up of 14 +/- 8 months.

CONCLUSION

Left septal AT ablation is safe and effective. There was no consistent P-wave morphology associated with this particular type of AT. This arrhythmia appears to be resistant to adenosine and moderately responsive to calcium antagonists.

Atrial components contributing to pseudo r' deflection in lead V1 in slow/fast atrioventricular nodal reentrant tachycardia: analysis of the atrial activation sequence by basket catheter isochronal mapping

Electrocardiographic recognition of the P' wave during tachycardia is very useful in the diagnosis of supraventricular tachycardias. In slow/fast (S/F) atrioventricular nodal reentrant tachycardia (AVNRT), no discrete P' waves are observed on ECG and pseudo r' deflection in lead V1 (pseudo r') is commonly recognized. However, the atrial components that contribute to the genesis of pseudo r' in lead V1 have not been described and this study aimed to clarify them by analysis of the whole activation sequence of the right atrium using Basket catheter isochronal mapping. The study group comprised 48 patients with AVNRT. Pseudo r' was defined as an upward deflection in the terminal portion of the QRS complex during tachycardia that was not recognized during sinus rhythm and it occurred in 45 patients (94%). During S/F AVNRT, the retrograde atrial activation was earliest on His bundle electrogram, followed by the coronary sinus ostium, distal coronary sinus and high right atrium. Only the high lateral aspect of the right atrium was activated after the end of the QRS complex. The interval between the onset of QRS in multiple surface ECG leads and the atrial activities on high right atrium was similar to the V-r' interval in lead V1 (111+/-20ms, 117+/-11 ms) and correlated with the V-r' interval (r=0.56). Pseudo r' deflection in lead V1 is a highly sensitive indicator of S/F AVNRT, and appears to result from the activation of the superolateral aspect of the right atrium.

Diagnostic value of tachycardia features and pacing maneuvers during paroxysmal supraventricular tachycardia

OBJECTIVES

The purpose of this prospective study was to quantitate the diagnostic value of several tachycardia features and pacing maneuvers in patients with paroxysmal supraventricular tachycardia (PSVT) in the electrophysiology laboratory.

BACKGROUND

No study has prospectively compared the value of multiple diagnostic tools in a large group of patients with PSVT.

METHODS

One hundred ninety-six consecutive patients who had 200 inducible sustained PSVTs during an electrophysiology procedure were included. The diagnostic values of four baseline electrophysiologic parameters, nine tachycardia features and five diagnostic pacing maneuvers were quantified.

RESULTS

The only tachycardia characteristic that was diagnostic of atrioventricular (AV) nodal reentry was a septal ventriculoatrial (VA) time of <70 ms, and no pacing maneuver was diagnostic for AV nodal reentry. An increase in the VA interval with the development of a bundle branch block was the only tachycardia characteristic that was diagnostic for orthodromic tachycardia, but it occurred in only 7% of all tachycardias. An atrial-atrial-ventricular response upon cessation of ventricular overdrive pacing was diagnostic of atrial tachycardia, and this maneuver could be applied to 78% of all tachycardias. Burst ventricular pacing excluded atrial tachycardia when the tachycardia terminated without depolarization of the atrium, but the result could be obtained only in 27% of patients.

CONCLUSIONS

This prospective study quantitates the diagnostic value of multiple observations and pacing maneuvers that are commonly used during PSVT in the electrophysiology laboratory. The findings demonstrate that diagnostic techniques rarely provide a diagnosis when used individually. Therefore, careful observations and multiple pacing maneuvers are often required for an accurate diagnosis during PSVT. The results of this study provide a useful reference with which new diagnostic techniques can be compared.

Congenital Heart Surgery Nomenclature and Database Project: arrhythmias

This discussion of arrhythmia terminology attempts to classify rhythm disorders for which surgical therapy may be necessary. The subject was debated and reviewed by members of the STS-Congenital Heart Surgery Database Committee and representatives from the European Association for Cardiothoracic Surgery, for the purpose of establishing a unified reporting system. Efforts were made to include all relevant nomenclature categories, using synonyms where appropriate. Extant surgical ablative procedures, detailed methods of pacemaker insertion, and AICD technology are discussed. A comprehensive database set is presented that is based on a hierarchical scheme. Data are entered at various levels of complexity and detail, which can be determined by the clinician. These data can lay the foundation for comprehensive risk stratification analyses. A minimum database set is also presented, which will allow for data sharing and will lend itself to basic interpretation of trends. Outcome tables relating diagnoses, procedures, and various risk factors are presented.

Radiofrequency catheter ablation of tachycardia in children with and without congenital heart disease: indications and limitations

From 1993 to 1998, a total of 100 consecutive pediatric patients with tachycardia (45 male and 55 female, aged 1 year 10 months to 17 years, 11+/-4 year) who underwent electrophysiological study were reviewed. Eleven of them were younger than 5 years. Two had tachycardia-related cerebrovascular accident. Congenital heart disease was found in 12 patients. After propofol anesthesia, the clinical tachycardia could not be induced in three (two atrial tachycardia and one AV nodal re-entrant tachycardia) and became nonsustained in five (atrial tachycardia). Mechanical ablation occurred in three and two had subsequent recurrences. Among the 85 cases who received radiofrequency ablation, the overall final success rate of RF ablation for all diagnoses was 94% with a diagnosis-specific success rate ranging from 100 to 57%. Tachycardia cardiomyopathy was noted in four (three atrial tachycardia and one junctional ectopic tachycardia) and all regressed after successful ablation. Success in two patients with left posterioseptal accessory pathway could only be achieved by delivering the energy at the middle cardiac vein. Two patients with right atrial isomerism had an 'AV nodal-to-AV nodal tachycardia' which was eliminated by ablation. Total recurrence rate was 13% but final success was achieved in all during re-study except the three patients who refused re-intervention. The atrial tachycardia developed in postoperative congenital heart disease was associated with the lowest success rate (57%) and highest recurrence rate (25%). Procedure-related complications occurred in four; two with transient brachial palsy, one with first-degree AV block and one with blood loss requiring blood transfusion. In conclusion, the experience of this single center confirmed the efficacy and safety of radiofrequency catheter ablation in treating pediatric arrhythmias, but the limitations in postoperative arrhythmias and the effects of propofol on tachycardia induction (especially the atrial tachycardia) need to be improved.

Computer-assisted animation of atrial tachyarrhythmias recorded with a 64-electrode basket catheter

OBJECTIVES

The aim of this study was to assess the value of a new mapping technique based on computer-assisted animation of multielectrode basket catheter (BC) recordings in patients with atrial arrhythmias.

BACKGROUND

The three-dimensional activation patterns of cardiac arrhythmias are not completely understood owing to limitations of conventional mapping techniques.

METHODS

The study included 32 patients with atrial tachycardia (AT) and 38 patients with atrial flutter (AFL). A software program was developed to analyze the activation patterns based on 56 bipolar electrograms recorded with a 64-electrode BC deployed in the right atrium (RA).

RESULTS

The total time needed for the animation of activation patterns of atrial arrhythmias was 5 +/- 0.8 min. In 22 patients with right AT, the animated maps revealed that arrhythmia was unifocal in 15 patients, multifocal in 2 patients, polymorphic in 4 patients and reentrant in 1 patient. In 10 patients with left AT, breakthroughs on the right side of the septum (2 in 8 patients and 1 in 2 patients) and a left-to-right activation of the RA were demonstrated. In patients with typical AF, the reentrant excitation was a broad activation front with preferential propagation around the tricuspid annulus. In patients with atypical AFL, the reentry circuit involved one of the venae cavae and a line of block located in the posterior wall.

CONCLUSIONS

The computer-assisted animation of multiple electrograms recorded with a BC is a valuable mapping tool that delineates the three-dimensional activation patterns of various atrial arrhythmias. The technique is appropriate for complex, short-lived or unstable arrhythmias.

Clinical experience with a novel multielectrode basket catheter in right atrial tachycardias

BACKGROUND

The complexity of atrial tachycardias (ATs) makes the electroanatomic characterization of the arrhythmogenic substrate difficult with conventional mapping techniques. The aim of our study was to evaluate possible advantages of a novel multielectrode basket catheter (MBC) in patients with AT.

METHODS AND RESULTS

In 31 patients with AT, an MBC composed of 64 electrodes was deployed in the right atrium (RA). The possibility of deployment, spatial relations between MBC and RA, MBC recording and pacing capabilities, mapping performance, and MBC-guided ablation were assessed. MBC deployment was possible in all 31 patients. The MBC was left in the RA for 175+/-44 minutes. Stable bipolar electrograms were recorded in 88+/-4% of electrodes. Pacing from bipoles was possible in 64+/-5% of electrode pairs. The earliest activity intervals, in relation to P-wave onset, measured from the MBC and standard roving catheters were 41+/-9 and 46+/-6 ms, respectively (P=0.21). Radiofrequency ablation was successful in 15 (94%) of 16 patients in whom it was attempted, including 2 patients with polymorphic right atrial tachycardia (RAT), 2 with RAT-atrial flutter combination, 1 with macroreentrant AT, and 1 with focal origin of atrial fibrillation.

CONCLUSIONS

These data demonstrate that MBC can be used safely in patients with right atrial arrhythmias. The simultaneous multielectrode mapping aids in the rapid identification of sites of origin of the AT and facilitates radiofrequency ablation procedures. The technique is especially effective for complex atrial arrhythmias.

Heterogeneity of anterograde fast-pathway and retrograde slow-pathway conduction patterns in patients with the fast-slow form of atrioventricular nodal reentrant tachycardia: electrophysiologic and electrocardiographic considerations

OBJECTIVES

This study sought to define the electrophysiologic and electrocardiographic characteristics of fast-slow atrioventricular nodal reentrant tachycardia (AVNRT).

BACKGROUND

In fast-slow AVNRT the retrograde slow pathway (SP) is located in the posterior septum, whereas the anterograde fast pathway (FP) is located in the anterior septum; however, exceptions may occur.

METHODS

Twelve patients with fast-slow AVNRT were studied. To determine the location of the retrograde SP, atrial activation during AVNRT was examined while recording the electrograms from the low septal right atrium (LSRA) on the His bundle electrogram and the orifice of the coronary sinus (CS). Further, to investigate the location of the anterograde FP, single extrastimuli were delivered during AVNRT both from the high right atrium and the CS.

RESULTS

The CS activation during AVNRT preceded the LSRA in six patients (posterior type); LSRA activation preceded the CS in three patients (anterior type), and in the remaining three both sites were activated simultaneously (middle type). In the anterior type, CS stimulation preexcited the His and the ventricle without capturing the LSRA electrogram (atrial dissociation between the CS and the LSRA), suggesting that the anterograde FP was located posterior to the retrograde SP. In the posterior and middle types, high right atrial stimulation demonstrated atrial dissociation, suggesting that the anterograde FP was located anterior to the SP. In the posterior and middle types, retrograde P waves in the inferior leads were deeply negative, whereas they were shallow in the anterior type.

CONCLUSIONS

Fast-slow AVNRT was able to be categorized into posterior, middle and anterior types according to the site of the retrograde SP. The anterior type AVNRT, where an anteriorly located SP is used in the retrograde direction and a posteriorly located FP in the anterograde direction, appears to represent an anatomical reversal of the posterior type which uses a posterior SP for retrograde and an anterior FP for anterograde conduction. Anterior type AVNRT should be considered in the differential diagnosis of long RP (RP > PR intervals) tachycardias with shallow negative P waves in the inferior leads.

Clinical differentiation of narrow QRS complex tachycardias

Supraventricular tachycardias generally present with narrow QRS complexes and are quite commonly seen in the emergency department. Regular narrow QRS complex tachycardias occur in all age groups and may be associated with minimal symptoms, such as palpitations, or, present with hemodynamic compromise resulting in syncope. While history and physical examination are indispensable, they usually do not lead to a definitive diagnosis. The diagnosis is made by careful analysis of the 12-lead ECG. Therapy is based on hemodynamic assessment and understanding of the tachycardia mechanism.

2:1 atrioventricular block during atrioventricular node reentrant tachycardia

OBJECTIVES

The purpose of this study was to determine the incidence and to clarify the mechanism of 2:1 atrioventricular (AV) block during AV node reentrant tachycardia induced in the electrophysiology laboratory.

BACKGROUND

In patients with 2:1 AV block during AV node reentrant tachycardia, the absence of a His bundle potential in the blocked beats has been considered evidence of intranodal, lower common pathway block.

METHODS

In consecutive patients with AV node reentrant tachycardia, the incidence of 2:1 AV block and the response to atropine and a single ventricular extrastimulus was observed.

RESULTS

Persistent 2:1 AV block occurred in 13 of 139 patients with AV node reentrant tachycardia. A His bundle deflection was present in the blocked beats in eight patients and absent in five. Patients with 2:1 AV block had a shorter tachycardia cycle length than did patients without such block (mean +/- SD 312 +/- 32 vs. 353 +/- 55 ms, p < 0.01). Atropine did not alter the 2:1 block in any patient. In every patient, a single ventricular extrastimulus introduced during the tachycardia converted the 2:1 block to 1:1 conduction.

CONCLUSIONS

The incidence of induced 2:1 AV block during AV node reentrant tachycardia is approximately 10%. The lack of a response to atropine and the consistent conversion of 2:1 block to 1:1 conduction by a ventricular extrastimulus indicate that, regardless of the presence or absence of a His bundle potential in blocked beats, 2:1 block during AV node reentrant tachycardia is due to functional infranodal block.

Paroxysmal supraventricular tachycardias

Paroxysmal supraventricular tachycardia (PSVT) is a distinct clinical syndrome. Most patients present with the abrupt onset of palpitations, dizziness, dyspnea, or chest pain. The electrocardiogram (ECG) demonstrates a fast heart rate (150-250 beats per min), a regular rhythm, and most often, a narrow QRS complex. The P wave is usually hidden within the QRS complex. PSVT is caused by reentry, and the tachycardias are classified, electrophysiologically, according to the anatomic location of the reentry circuit. Atrioventricular nodal reentry is the most common form of PSVT. In A-V nodal reentry, there are two conducting pathways (alpha and beta) that have different conduction times and refractory periods; both pathways are confined to the A-V nodal and perinodal atrial tissue. The other common form of PSVT, termed atrioventricular reciprocating tachycardia, depends on an anatomically distinct, or "accessory," pathway that may conduct impulses between the atria and the ventricles, while bypassing the AV node. The two forms of PSVT may be distinguished in many cases by examining the 12-lead electrocardiogram. In the majority of cases of A-V nodal reentry, the atria and ventricles are depolarized simultaneously, and the P waves are hidden in the QRS complex. If the reentry circuit includes an accessory pathway, the P wave always follows the QRS, and usually the R-P interval exceeds 70 msec. Several principles should guide the management of PSVT: (a) Unstable patients require emergent electrical cardioversion; (b) A 12-lead ECG should be obtained immediately to confirm that the tachycardia has a narrow complex (ventricular tachycardia may masquerade as PSVT if only a single lead is examined); (c) Vagal maneuvers may be attempted (the Valsalva maneuver is safer and more efficacious, especially in the elderly); and (4) In most patients, adenosine is the first-line agent to treat PSVT. Contraindications to adenosine and drug interactions are noted in this article. In addition, the use of adenosine in wide complex tachycardias and the indications for admission and referral for electrophysiologic evaluation are discussed.

Comparison of atrial-His intervals during tachycardia and atrial pacing in patients with long RP tachycardia

INTRODUCTION

The purpose of this study is to describe a simple and reliable diagnostic maneuver that allows for the rapid differentiation of atypical AV nodal reentrant tachycardia (AVNRT) from other causes of long RP tachycardia. Long RP tachycardias may be caused by atypical AVNRT, orthodromic reciprocating tachycardia (ORT) involving a slowly conducting retrograde accessory pathway, or atrial tachycardia. The differentiation of atypical AVNRT from ORT or atrial tachycardia may be difficult, especially when the differential diagnosis includes a posteroseptal accessory pathway or an atrial tachycardia arising in the posteroseptal right atrium.

METHODS AND RESULTS

Twelve patients with atypical AVNRT, 21 with ORT, and 12 with an atrial tachycardia diagnosed using conventional criteria were enrolled in this study. The atrial-His (AH) interval was measured at the His-bundle position during the tachycardia and during atrial pacing from the high right atrium at the tachycardia cycle length in the setting of sinus rhythm. In patients with atypical AVNRT, the mean AH interval was 69 69 msec +/- 50 msec (+/- SD) longer during high right atrial pacing than during the tachycardia (P < 0.001). In 10 of 12 patients with atypical AVNRT, the AH interval during atrial pacing was more than 40 msec longer than the AH interval measured during the tachycardia. In contrast, in patients with ORT or atrial tachycardia, the differences in AH interval between atrial pacing and tachycardia were never more than 20 and 10 msec, respectively.

CONCLUSION

The difference in the AH interval between atrial pacing and the tachycardia allows a simple and rapid means of differentiating atypical AVNRT from other types of long RP tachycardias.

Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients

OBJECTIVES

This study sought to determine the accuracy of transesophageal electrophysiologic studies in diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients.

BACKGROUND

Transesophageal electrophysiologic studies are a relatively noninvasive means of characterizing supraventricular tachycardia. Although widely used, to our knowledge no data exist that directly compare information obtained from transesophageal electrophysiologic studies with that from intracardiac electrophysiologic studies.

METHODS

We reviewed the records of 57 pediatric patients undergoing both transesophageal and intracardiac electrophysiologic studies at our institution. The results of these studies were compared with respect to mechanism of tachycardia, localization of accessory atrioventricular (AV) connections (if present) and characterization of anterograde accessory connection conduction properties.

RESULTS

Tachycardia mechanisms were concordant in 56 of 57 patients: orthodromic reciprocating tachycardia in 43, antidromic reciprocating tachycardia in 1, both orthodromic and antidromic tachycardia in 2, AV node reentrant tachycardia in 5, atrial reentrant tachycardia in 4 and ectopic atrial tachycardia in 2. Of 29 patients with orthodromic reciprocating tachycardia using a concealed accessory connection, transesophageal study predicted the accessory connection site through changes induced by transient bundle branch block in 12. By the Bland-Altman method in 14 patients with pre-excitation, the anterograde accessory connection effective refractory period determined by transesophageal study compared favorably with that determined by intracardiac study (mean difference 5.0 ms, limits of agreement -55 and 65 ms).

CONCLUSIONS

Transesophageal electrophysiologic studies are a highly accurate means of diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients.

P-wave signal-averaged electrocardiogram in patients with idiopathic mitral valve prolapse syndrome and supraventricular arrhythmias

The aim of the study was to assess whether the P-wave triggered signal-averaged ECG (SAECG) used in patients with idiopathic mitral valve prolapse syndrome could predict the risk of the development of supraventricular arrhythmias. Fifty patients with idiopathic mitral valve prolapse syndrome (15 men, 35 women, mean age: 37 +/- 9 years) were prospectively studied. P-wave triggered SAECG was recorded with a commercially available system (HIPEC-200HA Aerotel). The following parameters were calculated: the root-mean-square voltage for the terminal 10, 20, 30 ms of filtered P-wave (RMS10,20,30) and time duration of filtered P-wave (PWD). Nine patients with mitral valve prolapse syndrome (18%) revealed the occurrence of supraventricular arrhythmias on Holter monitoring whereas of the remaining 41 (82%), no clinically relevant supraventricular arrhythmias were detected. We found PWD values to be significantly longer in patients with supraventricular arrhythmias when compared with those without arrhythmias: 119.8 +/- 6.9 ms vs. 111.7 +/- 12.1 ms, respectively, P < 0.02. We conclude that P-wave triggered SAECG could be a useful technique for detecting patients with idiopathic mitral valve prolapse syndrome at risk of paroxysmal supraventricular arrhythmias.

Prevalence and prognostic significance of exercise-induced supraventricular tachycardia in apparently healthy volunteers

The prevalence, characteristics, and prognostic significance of supraventricular tachycardia (SVT) occurring during maximal treadmill exercise testing were examined in 843 male and 540 female asymptomatic volunteers aged 20 to 94 years from the Baltimore Longitudinal Study of Aging who underwent exercise testing a mean of 2.3 times between 1977 and 1991. Exercise-induced SVT occurred during at least 1 test in 51 men (6.0%) and 34 women (6.3%), p = NS for gender. The 85 subjects with exercise-induced SVT were significantly older than the 1,298 free from this arrhythmia (66.0 +/- 13.5 vs 49.7 +/- 18.0 years, respectively, p < 0.001). The prevalence of SVT increased with age in men (p < 0.001) but not in women. Ninety-eight percent of the 141 discrete episodes of exercise-induced SVT were paroxysmal SVT, with heart rates varying from 105 to 290 beats/min (mean 186.3 +/- 43.3); only 16% were > 10 beats in duration and only 4% of subjects were symptomatic. Nearly half (44%) of SVT episodes occurred at peak effort. Coronary risk factors, echocardiographic left atrial size (3.3 +/- 6.7 vs 3.3 +/- 0.6 cm), and the prevalence of exercise-induced ischemic ST-segment depression (11% vs 13%) were similar in 85 subjects with SVT and 170 control subjects matched for age and sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic significance of transient complete atrioventricular block during radiofrequency ablation of atrioventricular node reentrant tachycardia

One hundred eighty-six consecutive patients underwent radiofrequency ablation and were divided into 2 groups: group 1 included 19 patients (13 women, mean age 50 +/- 15 years) with transient atrioventricular (AV) block during the procedure. The duration of AV block ranged from 4 seconds to 30 minutes (mean 2.8 +/- 7.0 minutes); and group 2 included 167 patients (142 women, mean age 40 +/- 17 years) without transient AV block. Follow-up was 8.6 +/- 8.3 months in group 1 and 10.1 +/- 9.4 months in group 2. No significant differences were observed between the 2 groups concerning the ablation approach (fast or slow pathway), the number of radiofrequency applications, and recurrences of tachycardia. Four patients from group 1 who underwent fast pathway ablation developed late complete AV block, whereas no patient in group 2 had such a complication (p = 0.0001). Late complete AV block occurred 20 hours, 6 days, 1 month, and 25 days after ablation, respectively, and was not related to the duration of transient AV block. Another patient from group 1 developed an asymptomatic 2:1 AV block during exercise, 3 months after slow pathway ablation. Transient AV block, a common finding occurring as often during fast as during slow pathway ablation, did not preclude recurrences of tachycardia but was associated with late complete AV block.

Mechanisms of adenosine-mediated actions on cellular and clinical cardiac electrophysiology

OBJECTIVE

To provide insights into the molecular mechanisms of adenosine-mediated cardiac cellular electrophysiology and how information about these mechanisms can be used to facilitate diagnostic and therapeutic approaches to various clinical arrhythmias.

DESIGN

A review of (1) adenosine metabolism and receptors in the cardiac system, (2) adenosine-mediated signal transduction pathways in the regulation of cellular electrophysiology in various cardiac cell types, and (3) the clinical usefulness of adenosine in cardiac electrophysiology is presented.

RESULTS

The effects of adenosine on cardiac electrophysiologic properties are consequences of complex interactions among the specific cardiac target structures, the density and type of adenosine receptors, and the effector systems. The easy application of adenosine and its short half-life, favorable side-effects profile, and electrophysiologic properties make it an excellent diagnostic and therapeutic tool for the initial assessment of various tachyarrhythmias.

CONCLUSION

The direct adenosine-activated KACh (potassium acetylcholine) channel signal transduction system explains the effects of adenosine on the sinus node, atrioventricular node, and atrial myocardium. The indirect adenosine-inhibited adenylate cyclase system accounts for its negative inotropic effects on the catecholamine-entrained contractility in atrial and ventricular myocardium. Because of the recent purification and cloning of adenosine receptors and subunits of G proteins, additional adenosine-mediated electrophysiologic mechanisms can be explored.

Effectiveness of radiofrequency catheter ablation for treatment of atrial tachycardia

Catheter ablation has been used to treat atrioventricular node reentrant and atrioventricular reentrant tachycardias with extremely high success rates. The suitability of catheter ablation for treatment of atrial tachycardia, a much less common type of supraventricular tachycardia, has not been well addressed. Fifteen patients (8 females) ranging from 10 to 83 years (mean 38 +/- 22) were referred for catheter ablation of supraventricular tachycardia. The diagnosis of atrial tachycardia was established by standard electrophysiologic techniques. A combination of activation and pace mapping was used to identify a suitable site for radiofrequency current catheter ablation. Medical therapy was unsuccessful in all but 1 patient. Two patients had surgically corrected congenital heart disease, 2 had coronary artery disease and 1 had dilated cardiomyopathy. Seven patients had depressed left ventricular function. Six patients had incessant tachycardias. Presumed tachycardia mechanism was automatic in 11 patients and reentrant in 4. Mean tachycardia cycle length was 372 +/- 74 ms. Catheter ablation was acutely successful in 12 patients (80%) with application of 11.1 +/- 6.6 lesions at a mean voltage of 60 +/- 9 V. In the other 3 patients, 16 to 38 lesions were applied. At a mean follow-up of 18.5 +/- 6.5 months, 2 patients have had recurrences with different P-wave morphologies and underwent a second successful catheter ablation procedure. An additional 2 patients had recurrences with the same P-wave morphology and 1 underwent a second successful catheter ablation procedure. Thus, radiofrequency ablation can be used in a diverse population of patients with atrial tachycardia with an acute success rate of 80% and a long-term success rate of 73%.

Atrial late potentials: paroxysmal supraventricular tachycardia versus paroxysmal atrial fibrillation

The atrial signal averaged electrocardiogram has been used to detect patients at risk for paroxysmal atrial fibrillation but not yet for paroxysmal supraventricular tachycardia. The P-wave-triggered signal-averaged electrocardiogram, during sinus rhythm, was obtained from 97 subjects divided in groups as follows: 30 controls (Group C), 38 patients with documented paroxysmal atrial fibrillation (Group A) and 29 with documented paroxysmal supraventricular tachycardia (Group B). The atrial duration, root mean square of last 20 and 30 ms and the P-QRS segment were measured. Atrial late potentials were considered to exist when: atrial duration was > 120 ms and root mean square of last 20 ms were < 3.5 microV. The atrial duration (ms) was significantly shorter (P < 0.001) in Group C (113.4 +/- 8) than in Group A (138.5 +/- 23.8) and Group B (134.3 +/- 14.3). The root mean square (microV) of last 20 ms was significantly higher (P < 0.001) in Group C (5.2 +/- 2.5) than in Group A (2.5 +/- 1.3) and Group B (3.1 +/- 1.8). Atrial late potentials were present in 3/30 controls, 32/38 of Group A cases and 23/29 of Group B. The specificity and sensitivity were, respectively: 0.90, 0.84, for Group A, and 0.90, 0.79 for Group B. The P-QRS segment (ms) was significantly shorter (P < 0.01) in Group B (12.5 +/- 9.4) than in Group C (32.5 +/- 16.9) and Group A (20.5 +/- 13.4).(ABSTRACT TRUNCATED AT 250 WORDS)

The response of paroxysmal supraventricular tachycardia to overdrive atrial and ventricular pacing: can it help determine the tachycardia mechanism?

INTRODUCTION

Standard electrophysiologic techniques generally allow discrimination among mechanisms of paroxysmal supraventricular tachycardia. The purpose of this study was to determine whether the response of paroxysmal supraventricular tachycardia to atrial and ventricular overdrive pacing can help determine the tachycardia mechanism.

METHODS AND RESULTS

Fifty-three patients with paroxysmal supraventricular tachycardia were studied. Twenty-two patients had the typical form of atrioventricular (AV) junctional (nodal) reentry, 18 patients had orthodromic AV reentrant tachycardia, 10 patients had atrial tachycardia, and 3 patients had the atypical form of AV nodal reentrant tachycardia. After paroxysmal supraventricular tachycardia was induced, 15-beat trains were introduced in the high right atrium and right ventricular apex sequentially with cycle lengths beginning 10 msec shorter than the spontaneous tachycardia cycle length. The pacing cycle length was shortened in successive trains until a cycle of 200 msec was reached or until tachycardia was terminated. Several responses of paroxysmal supraventricular tachycardia to overdrive pacing were useful in distinguishing atrial tachycardia from other mechanisms of paroxysmal supraventricular tachycardia. During decremental atrial overdrive pacing, the curve relating the pacing cycle length to the VA interval on the first beat following the cessation of atrial pacing was flat or upsloping in patients with AV junctional reentry or AV reentrant tachycardia, but variable in patients with atrial tachycardia. AV reentry and AV junctional reentry could always be terminated by overdrive ventricular pacing whereas atrial tachycardia was terminated in only one of ten patients (P < 0.001). The curve relating the ventricular pacing cycle length to the VA interval on the first postpacing beat was flat or upsloping in patients with AV junctional reentry and AV reentry, but variable in patients with atrial tachycardia. The typical form of AV junctional reentry could occasionally be distinguished from other forms of paroxysmal supraventricular tachycardia by the shortening of the AH interval following tachycardia termination during constant rate atrial pacing.

CONCLUSIONS

Atrial and ventricular overdrive pacing can rapidly and reliably distinguish atrial tachycardia from other mechanisms of paroxysmal supraventricular tachycardia and occasionally assist in the diagnosis of other tachycardia mechanisms. In particular, the ability to exclude atrial tachycardia as a potential mechanism for paroxysmal supraventricular tachycardia has important implications for the use of catheter ablation techniques to cure paroxysmal supraventricular tachycardia.

Differentiation of paroxysmal narrow QRS complex tachycardias using the 12-lead electrocardiogram

OBJECTIVES

The purpose of this study was to evaluate the utility of the 12-lead electrocardiogram (ECG) for differentiating paroxysmal narrow QRS complex tachycardias.

BACKGROUND

Previous studies evaluating the utility of the 12-lead ECG for differentiating paroxysmal supraventricular tachycardia types have shown conflicting results on the usefulness of some ECG criteria, and some criteria that are considered to be useful have never been formally evaluated.

METHODS

Two hundred forty-two ECGs demonstrating paroxysmal narrow QRS complex (< 0.11 ms) tachycardia (rate > or = 120 beats/min) were analyzed. All ECGs were analyzed by an observer who had no knowledge of the mechanism of the tachycardia.

RESULTS

There were 137 atrioventricular (AV) reciprocating tachycardias, 93 AV node reentrant tachycardias and 12 atrial tachycardias. Six criteria were found to be significantly different between tachycardia types by univariate analysis. A P wave separate from the QRS complex was observed more frequently in AV reciprocating tachycardia (68%) and atrial tachycardias (75%). A pseudo r' deflection in lead V1 and a pseudo S wave in the inferior leads were more common in AV node reentrant tachycardia (58% and 14%, respectively); QRS alternans was present more often during AV reciprocating tachycardia (27%). When a P wave was present, an RP/PR interval ratio > or = 1 was more common in atrial tachycardias (89%). During sinus rhythm, manifest pre-excitation was observed more often in patients with AV reciprocating tachycardia (45%). By multivariate analysis, the presence of a P wave separate from the QRS complex, pseudo r' deflection in lead V1, QRS alternans during tachycardia and the presence of pre-excitation during sinus rhythm were independent predictors of tachycardia type. These criteria correctly identified 86% of AV node reentrant tachycardias, 81% of AV reciprocating tachycardias and incorrectly assigned the tachycardia type in 19% of cases.

CONCLUSIONS

Several features on the ECG are useful for differentiating supraventricular tachycardia type. However, approximately 20% of tachycardias may be incorrectly classified on the basis of analysis of the ECG; therefore, the ECG should not serve as the sole means for determining tachycardia mechanism.

Comparison of the cost of radiofrequency catheter modification of the atrioventricular node and medical therapy for drug-refractory atrioventricular node reentrant tachycardia

The purpose of this study was to determine the charges for radiofrequency catheter modification of the atrioventricular (AV) node in 15 patients with symptomatic AV node reentrant tachycardia despite pharmacologic therapy and to compare these charges with the estimated charges for health care utilization by the same patients before the catheter procedure was performed. There were seven men and eight women with a mean age of 50 +/- 17 years. The mean duration and frequency of symptoms were 16 +/- 9 years and 4.5 +/- 6 episodes/month, respectively. Fourteen of the 15 patients required only one procedure for diagnosis and cure of AV node reentrant tachycardia and 1 patient required two sessions. All patients underwent electrophysiologic study before discharge from the hospital to confirm the short-term efficacy of the procedure. The mean duration of the hospital stay was 3 +/- 1.5 days and the mean total charge/patient expressed in 1991 dollars was $15,893 +/- $3,338 for catheter modification. These total charges consisted of hospital charges of $8,105 +/- $2,466 and physician charges of $7,788 +/- $971. All patients had a successful outcome and required no additional antiarrhythmic therapy. The estimated cost of health care utilization for these 15 patients before cure of AV node reentrant tachycardia was $7,651/patient per year. These estimated costs included charges incurred for emergency room visits, office visits, hospitalizations and antiarrhythmic drug therapy. In conclusion, the results of this study indicate that the annual health care costs incurred by patients who have symptomatic, drug-refractory paroxysmal supraventricular tachycardia caused by AV node reentry are substantial.(ABSTRACT TRUNCATED AT 250 WORDS)