Reentrant Supraventricular Tachycardia Research Articles

Atrioventricular Nodal Reentrant Tachycardia in Implantable Cardioverter Defibrillators: Diagnosis and Troubleshooting.

Inappropriate therapies are frequent in patients with implantable cardioverter defibrillators (ICDs) and are associated with adverse outcomes, including increased mortality. Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common reentrant supraventricular tachycardia (SVT) and a cause of inappropriate therapies in these patients. In the present article we review the problem of AVNRT in ICD patients with a focus on diagnosis and the available algorithms to improve arrhythmia discrimination and prevent inappropriate shocks.

The mechanisms of spontaneous termination of reentrant supraventricular tachycardias

BackgroundAtrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) often terminate spontaneously, presumably due to changes in the electrophysiological properties of the reentrant circuit. However, the mechanism of spontaneous termination of these arrhythmias is incompletely understood. MethodsWe included 70 consecutive patients with reentrant supraventricular tachycardias (35 AVNRT, 35 AVRT) in whom the arrhythmia ended spontaneously during the electrophysiologic study. We determined in each patient the duration of the induced arrhythmia, site of block, beat-to-beat oscillations in tachycardia cycle-length (CL), A-H, H-V, H-A and V-A intervals. ResultsIn 21/34 (62%) patients with AVNRT and 19/30 (63%) with orthodromic AVRT, tachycardia termination was preceded by progressive increase in tachycardia CL due to prolongation of the A–H interval (Mobitz type-I pattern). In 13/34 patients with AVNRT (38%) and 11/30 with orthodromic AVRT (37%), termination occurred suddenly without a preceding change in CL, with block ensuing retrogradely either in the fast AV nodal pathway or the accessory pathway (Mobitz type-II pattern). In 4/5 patients with antidromic AVRT the tachycardia ended at the retrograde limb with previous prolongation of the VA interval. ConclusionSpontaneous termination of AVNRT and AVRT is a time-related phenomenon. Despite different pathways being involved in these two reentrant tachycardias, termination can follow antegrade or retrograde block in similar ratio (60% antegradely and 40% retrogradely). Antegrade block is preceded by prolongation of the AH interval (Mobitz type-I), whereas retrograde block occurs unexpectedly in the retrograde limb (Mobitz type-II). Fatigue of conduction appears to be involved in this phenomenon.

Supraventricular tachycardia during pediatric anesthesia: a case series and qualitative analysis

Study ObjectiveTo perform a qualitative analysis of noncardiac patients who developed suspected intraoperative supraventricular tachycardia (SVT) during general anesthesia. DesignRetrospective database analysis and chart review. SettingOperating room of a university-affiliated children’s hospital. MeasurementsThe records of children without cardiac disease who received general anesthesia at The Children’s Hospital of Philadelphia from July 1998 through June 2011 were reviewed. Patients with heart rate values above 180 beats per minute were identified, as were specific medications or key words in the free-text fields of the anesthesia records that would be indicative of a tachyarrhythmia. Each case was reviewed by at least two authors; each patient was assigned a diagnosis classification of “highly suspicious” or “unlikely” SVT. The highly suspicious SVT cases were examined in detail to determine the specific aims. Main Results36 subjects out of a total of 285,353 anesthetics administered during the study period were suspected by the anesthesia care team to have had an episode of intraoperative SVT: 22 were “highly suspicious” events, and 14 were “unlikely” events. The highly suspicious SVT events occurred in all phases of anesthesia, and none led to any hemodynamic instability. Effective treatments included vagal maneuvers, pharmacologic antiarrhythmics, or no treatment if the event resolved spontaneously before treatment. Six patients had outpatient follow-up and three received antiarrhythmic medications to control ongoing SVT. ConclusionsSVT during the intraoperative period in noncardiac pediatric patients was uncommon. When it occurred, it was not associated with clinically significant patient morbidity. For some patients, the anesthesia unmasked a predisposition for re-entrant SVT and those patients remained on maintenance antiarrhythmic therapy following discharge home.

Both atrioventricular nodal reentrant and atrioventricular reentrant tachycardias in one patient: a case report

E-mail: ivanzeljkov@gmail.com The two most common supraventricular tachycardias are typical (slow-fast) atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic atrioventricular reentrant tachycardia (AVRT) using accessory pathway (AP). Nowadays, a leading method in the treatment of supraventricular re-entrant tachycardias is radio-frequent (RF) catheter ablation during the electrophysiological (EP) study. We report the case of a 46-year old woman on whom an EP study was performed due to the presence of paroxysmal supraventricular tachycardia documented in 12-lead ECG. During the EP study, at baseline, supraventricular tachycardia was induced very easily and it corresponded to orthodromic AVRT (frequency of 190-200/min) using concealed, left lateral AP (PPI TCL = 100 ms; VAV pattern, preceding positive for AP). However, during the study, AVRT spontaneously converted to the typical slow-fast AVNRT (frequency 150/min) using the slow AV node pathway (PPI TCL >150 ms; VA < 30 ms; preceding negative for AP; jump noted at programmed pacing (500+280 ms) from right atrium as well as echo beat). During the EP study, a slow pathway was localized and then ablated using the RF catheter ablation. By performing the transseptal puncture of the interatrial septum, the left lateral wall AP was also successfully localized and then ablated using the RF catheter ablation. The patient remained asymptomatic for more than 6 months after the successful ablation procedures. To the authors' best knowledge, the coexistence of AVRT and AVNRT is not reported in the literature.

Randomised Evaluation of modified Valsalva Effectiveness in Re-entrant Tachycardias (REVERT) study

IntroductionThe Valsalva manoeuvre (VM) is a recommended first-line physical treatment for patients with re-entrant supraventricular tachycardia (SVT), but is often ineffective in standard practice. A failed VM is typically followed...

Two-dimensional echocardiographic features of the inferior right atrial isthmus: the role of vestibular thickness in catheter ablation of atrial flutter

The aim of this study was to examine the feasibility of transthoracic two-dimensional (2D)-echocardiography in defining the cavo-tricuspid isthmus (CTI) anatomy and its value concerning the ease of catheter ablation of isthmic atrial flutter (AF). CTI analysis was accomplished in 39 cases: 16 necropsy specimens and 23 patients. Sixteen were patients with isthmus-dependent AF and seven controls with other supraventricular re-entrant tachycardias. Two-dimensional transthoracic echocardiography and a right atrium angiogram were performed before radiofrequency catheter ablation (RFCA). The measurements of the CTI with angiography were compared with those taken with echocardiography and correlation was excellent (r= 0.91; P < 0.0001). In normal patients, the dimension of the vestibular thickness was successfully compared and validated with the histological examination of the necropsy specimens: histology median 6.8 mm, range 4.4-10.5 vs. echo median 6.2 mm, range 5.4-8.7; P: NS. Vestibular thickness was greater in complex than in simple RFCA (13.6 ± 1.9 mm vs. 10.0 ± 2.3 mm; P = 0.01). When vestibular thickness ≥11.5 mm, the ablation prone to be complex (sensitivity 83.3%, specificity 80%, positive predictive value 71.4%, and negative predictive value 88.9%). Two-dimensional transthoracic echocardiography clearly depicts the inferior isthmus and, displaying the thickness of the tricuspid vestibule, it was related with complexity of the ablation procedure in isthmus-dependent AF.

Prehospital Synchronized Electrical Cardioversion of a Poorly Perfused SVT Patient by Paramedics

Synchronized Direct Current Cardioversion (SDC) is an established therapy for the termination of supraventricular tachycardia (SVT - either atrio-ventricular nodal reentry tachycardia (AVNRT) or atrio-ventricular reentrant tachycardia (AVRT)) with poor perfusion. The evidence is extremely limited with regard to the safety and effectiveness of this therapy. In Australia, half of the eight ambulance services include SDC within their clinical practice guidelines for the management of poorly perfused SVT; however the degree of variation in the application of SDC across these guidelines suggests a need to quantify the practice. This case provides a previously unreported example of the safety and effectiveness of prehospital SDC for SVT (with poor perfusion precipitated by a Valsalva Maneuver) by Victorian paramedics, and discusses the available literature regarding the effectiveness and safety of this practice.

206: Isoproterenol infusion is more frequently required for the induction of atrioventricular node reentrant tachycardia than for the induction of atrioventricular reentrant tachycardia

Supraventricular reentrant tachycardia (SVT) can be due to atrioventricular node reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT) in a concealed or an overt accessory pathway (AP) in patients with a Wolff-Parkinson-White syndrome (WPW). The purpose of the study was to look for the mode of SVT induction and to correlate the mode of induction with the mechanism of the tachycardia. 1818 patients were consecutively referred for a SVT. 438 had a WPW (group I). Remaining patients had a normal ECG. At electrophysiological study (EPS), SVT was related to AVRT in 251 patients (group II), to typical AVNRT in 969 patients (group II) and to atypical AVNRT in 160 patients (group IV). Atrial pacing and programmed atrial stimulation with one and 2 extrastimuli were performed in control state (CS). If SVT was not induced, the protocol was repeated after isoproterenol (0.02 to 1 μg. min -1 ) infused to increase sinus rate to at least 130 bpm. Groups differed by age and gender: group I was younger than group II (36±17 vs 42±17 years) (p < 0.001). Group II was younger than group III (49±19)(p <0.001) and group III was younger than group IV (55±19) (p < 0.001). Gender in group I and II was more frequently male (55%, 57%) than in group III (36%) and IV (36%)(p<0.000). SVT induction required more frequently isoproterenol infusion among patients of group III with a typical AVNRT (32%) and IV with atypical AVNRT (33%) than in patients of group I (26%)(p<0.05) or group II (24%) (p < 0.02). Men required more frequently isoproterenol than women only in group I (p<0.0001). The youngest patients required more frequently isoproterenol than other but the differences were only significant in group III (47±19 vs 51±9 years, p<0.005). Isoproterenol infusion is more frequently required in patients with typical or atypical AVNRT than in patients with AVRT using an overt or a concealed AP. The youngest patients with AVNRT required isoproterenol infusion for the SVT induction more frequently than adults. Isoproterenol is required more frequently in men than in women only in patients with a WPW syndrome.

Antitachycardia pacing reduces appropriate and inappropriate shocks in children and congenital heart disease patients

Antitachycardia pacing (ATP) can reduce implantable cardioverter-defibrillator shocks, but its use in children and patients with congenital heart disease (CHD) is not well described. To review the efficacy of ATP in children and patients with CHD. We reviewed implantable cardioverter-defibrillator therapies in children and patients with CHD (aged 2-52 years) at our institution. Appropriate therapies were defined as those delivered for true ventricular tachycardia (VT) or ventricular fibrillation; other therapies were defined as inappropriate. During a median follow-up of 4 years (range 0.5-15 years), 17 of 79 patients (23%) received appropriate therapy and 14 received ATP for 100 episodes of VT. ATP was highly successful (88%) in terminating VT, and only 10 of 100 episodes required a shock. Shocks were effective in terminating VT/ventricular fibrillation in 21 of 24 episodes (87%). The outcomes of appropriate therapy were similar for ATP and shocks (success 88% vs 87%, failure 9% vs 8%, acceleration 3% vs 4% for ATP and shocks, respectively). Thirty-one patients (39%) received inappropriate therapy. Inappropriate ATP (without subsequent shocks) was delivered to 11 patients for the following: sinus tachycardia (19 episodes in 7 patients) with slowing of the rate after ATP, T-wave oversensing (2 episodes in 2 patients) with loss of oversensing after ATP, and reentrant supraventricular tachycardia (14 episodes in 2 patients) terminated with ventricular ATP. ATP is highly efficacious for VT in children and patients with CHD. In addition to reducing appropriate shocks, inappropriate shocks due to sinus or supraventricular tachycardia can be significantly reduced with ATP.

Dexmedetomidine: Therapeutic Use for the Termination of Reentrant Supraventricular Tachycardia

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. Retrospective case series. Quaternary University Children's Hospital, Cardiac Intensive Care Unit. Patients who received dexmedetomidine for SVT in the past 5 years. None. SVT episodes terminated with dexmedetomidine were compared with episodes terminated with adenosine. 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). 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.

Extracorporeal membrane oxygenation support for intractable primary arrhythmias and complete congenital heart block in newborns and infants

To describe the experience with extracorporeal membrane oxygenation support for intractable primary arrhythmias in newborns and infants. Retrospective study. A tertiary care pediatric hospital. Patients younger than 1 yr supported with extracorporeal membrane oxygenation for primary cardiac arrhythmias were identified from the institutional extracorporeal membrane oxygenation registry. Extracorporeal membrane oxygenation support. Clinical characteristics and outcomes were investigated for patients with primary cardiac arrhythmia supported with extracorporeal membrane oxygenation. Outcomes investigated were time from initiation of extracorporeal membrane oxygenation support to arrhythmia control, duration of extracorporeal membrane oxygenation support, and results of interventions performed while supported with extracorporeal membrane oxygenation. We summarized the independent categorical and continuous variables using frequencies, percentages, and medians and ranges, respectively. Extracorporeal membrane oxygenation support was used in nine patients for rescue therapy for primary tachyarrhythmia and bradycardia. The primary arrhythmias were: focal atrial tachycardia (n = 2); reentrant supraventricular tachycardia (n = 3); junctional ectopic tachycardia (n = 2); and congenital complete atrioventricular block (n = 2) patients. Seven patients presented with severe hemodynamic compromise, with six patients requiring extracorporeal cardiopulmonary resuscitation. All patients required extracorporeal membrane oxygenation within 24 hrs of initial presentation. Balloon atrial septostomy was performed in three patients and ablation was performed in two patients. Sinus rhythm was achieved in all reentrant supraventricular tachycardia and rate control was established in both patients with focal atrial tachycardia and in one patient with junctional ectopic tachycardia while using extracorporeal membrane oxygenation support. All patients survived to hospital discharge, and median follow-up for the cohort was 5 yrs. There was one late death; all survivors had good overall and neurologic outcomes. The requirement of extracorporeal membrane oxygenation support in newborns and infants with intractable arrhythmia is rare. Extracorporeal membrane oxygenation support does potentially carry morbidity; however, to prevent arrhythmia-related mortality, extracorporeal membrane oxygenation support and/or extracorporeal cardiopulmonary resuscitation should be considered in the management of hemodynamically unstable primary arrhythmias as an emergent lifesaving procedure.

Twin Atrioventricular Nodes Connecting to Sling of Conduction Tissue in Congenitally Corrected Transposition Associated With Straddling Tricuspid Valve

This report describes a case of reentrant supraventricular tachycardia relating to "twin" atrioventricular nodes in a 6-year-old female patient with congenitally corrected transposition of the great arteries associated with straddling tricuspid valve. Straddling and overriding of the tricuspid valve literally or by definition indicate malalignment of the inlet part of the ventricular septum and atrial septum by an abnormally large ventriculoatrial septal angle. Therefore, anterior atrioventricular conduction tissues are expected in this setting; however, the present report describes an exception to the rule that combination of straddling tricuspid valve is unlikely to be associated with twin atrioventricular nodes/sling. The patient underwent successful ablation of one atrioventricular node, eliminating the tachycardia, and subsequently Fontan-type palliation.

Diagnostic and Prognostic Value of Electrophysiologic Study in Patients With Nondocumented Palpitations

The 12-lead electrocardiogram helps to define the arrhythmic mechanism in patients with palpitations. However, in the setting of nondocumented palpitations the value of the electrophysiologic study (EPS) needs additional investigation. We investigated the utility of the EPS in patients with nondocumented palpitations. A total of 172 patients with normal electrocardiographic findings and nondocumented palpitations underwent an EPS. The clinical and electrophysiologic characteristics were assessed. The symptoms were long-lasting (>5 minutes) in 56%. Sudden onset was present in 99%, and termination was rapid in 65%. Neck palpitations were reported in 36%. The EPS findings were normal in 86 patients (50%); atrioventricular nodal reentrant tachycardia was induced in 43, orthodromic reentrant tachycardia in 9, and nonsustained atrial tachycardia/fibrillation (AT/AF) in 34. Long-lasting episodes, sudden termination, and neck palpitations predicted positive EPS findings and were associated with reentrant supraventricular tachycardia (p<0.001). The induction of AT/AF was associated with age >50 years and structural heart disease (p<0.001). After 53 ± 36 months of follow-up, 92% of patients with negative EPS findings were symptom free. Only 32% of patients with induced AT/AF remained free of symptoms (p<0.001). The recurrence of palpitations was more prevalent among patients with structural heart disease and aged >50 years (p<0.001). In conclusion, 50% of patients with nondocumented palpitations had positive EPS findings. A long duration, sudden termination, and neck palpitations, together with structural heart disease and age >50 years, predicted tachycardia inducibility and recurrence and could help in selecting patients suitable for EPS and ablation.

325 Diagnostic and prognostic value of troponin elevation associated with symptomatic paroxysmal reentrant supraventricular tachycardia

Cardiac troponin is the gold standard for the diagnosis and risk stratification in acute coronary syndrome (ACS). Troponin elevation associated with symptomatic paroxysmal reentrant supraventricular tachycardia (PSVT) has been described in short series but long term prognosis has not been yet reported. Overall survival in patients with and without ACS The aim of the present study was to evaluate the diagnostic and prognostic value of troponin I elevation following PSVT. From January 2003 to September 2009, all consecutive patients (n = 27, 52% females, median age 52 years) admitted for PSVT and troponin I elevation (mean 0.42 μg/l, range: 0.19–5.9) were included. None of the patients had a history of CAD. Thirteen patients (48.1%) were current smokers and 9 (33.3%) had no cardiovascular risk factor. All patients had narrow QRS during PSVT and the aetiology was nodal reentrant tachycardia in all except for one patient with preexcitation morphology in sinus rhythm. Coronary angiogram has been performed in 25 patients. Twenty three had angiographically normal coronary arteries. A single vessel disease (coronary stenosis >50%) was found in 2 patients and maximal stress echocardiography was normal in both patients. Two patients who declined coronary angiogram had normal maximal stress echocardiography. During follow-up (median 43 months, range: 4–82), none of the patients experienced ACS or cardiac death. One of the patients died from cancer after 63 months of follow up. Recurrence of PSVT requiring medical intervention occurred in 4 (14.8%) patients, atrial fibrillation in 3 (11%) patients and radiofrequency catheter ablation of atrioventricular nodal reciprocating tachycardia had been performed in 5 (18.5%) patients. Troponin I elevation following PSVT is common, not related to obstructive CAD or plaque rupture and is not associated with adverse short and long term prognosis.

308 Are there indications for supraventricular re-entrant tachycardia in the youth?

Radiofrequency (RF) ablation of paroxysmal supraventricular tachycardia (SVT) that could be an atrioventricular node re-entrant tachycardia (AVNRT) or AV reentrant tachycardia (AVRT) through a concealed accessory pathway (AP) is widely used in adults, but the indications remain controversed in children and teenagers. The purpose of the study was to evaluate the clinical and electrophysiological factors of indications of AVNRT and AVRT ablation in the youth and the results of the procedure. 66 children or teenagers aged from 6 to 18 years (15 ± 2) among 1099 patients consecutively recruited for SVT; they had a normal ECG in sinus rhythm; AVNRT or AVRT was confirmed at electrophysiological study (EPS). Patients with anterograde conduction through an AP were excluded. RF ablation was indicated in 26 children or teenagers (39%) (group I) significantly less frequently than in adults (668/1033; 65%) (p < 0.0000). 40 other children were not treated or received beta blockers (group II). Group I and II have the same age (15 ± 2.6 vs 15 ± 2.8). Male gender tended to be less frequent in group I (9/26; 35%) than in group II (20/40; 50%) (NS, 0.2). At EPS, group I had more frequently a concealed AP (13/26; 50%) than group II (8/40; 20%) (p < 0.01). The incidence of concealed AP in group I is higher than in adults (102 of 668 procedures;15%) (p < 000000). In remaining children, ablation of slow pathway was performed in 13 children. There were no complications, but failures or reappearances of SVT after ablation were frequent (6/26; 23%), more frequent in AVRT (4/13) than in AVNRT (2/13) (NS) and were related to the age (12.7 ± 3 vs 16 ± 2; p < 0.002). They tended to be more frequent than in adults (77/668; 11.5%) (p < 0.07). In group II, 3 children continue the beta blockers and other children are not treated. The indications of slow pathway remain rare in children. Most of the indications of SVT ablation in the youth which are rare, concern generally the children and teenagers with concealed AP. The results are almost as good as in adults, mainly for the slow pathway ablation and in teenagers.

Charcoal hemoperfusion in an infant with supraventricular tachycardia and seizures secondary to amitriptyline intoxication

Tricyclic antidepressant (TCA) overdose is one of the common causes of drug poisoning and it has cardiovascular, respiratory and neurological side effects. An 18-month male infant was admitted to our pediatric emergency service due to poisoning with amitriptyline. The infant was unconscious. Tachycardia, irregular and shallow breathing, and tonic-clonic seizures were observed on physical examination. An electrocardiogram displayed a narrow complex tachycardia that was consistent with re-entrant supraventricular tachycardia (SVT). Although antiarrhythmic and anticonvulsive agents were administrated, SVT and seizures persisted. Charcoal hemoperfusion (HP) was performed for 4 hours. The infant's clinical condition has improved after the charcoal HP, seizures and SVT were not observed. It is concluded that charcoal HP can be used efficiently in patients with severe amitriptyline intoxication.

Acute amiodarone toxicity due to an administration error: could excipient be responsible?

Acute amiodarone toxicity due to an administration error: could excipient be responsible?

Influence of Ventriculoatrial Timing on Hemodynamics and Symptoms During Supraventricular Tachycardia

Patients with reentrant supraventricular tachycardia (SVT) are often highly symptomatic and the mechanism of symptoms is not well understood. We hypothesized that variation in ventriculoatrial interval (QRS to P) modulates the left atrial pressure and symptoms during tachycardia. Three hundred twenty-six patients awaiting electrophysiological study completed a questionnaire regarding "neck pounding" or "shirt flapping" during tachycardia. Mean left atrial pressure was measured during simulated atrioventricular reentry tachycardia (AVRT) and atrioventricular nodal reentry tachycardia (AVNRT) in 18 patients. Pulmonary venous flow reversal was assessed using transesophageal echocardiography in 12 dogs when pacing at 220 bpm with different VA delays (0 to 250 ms). "Shirt flapping" is present more often during AVNRT than during AVRT (58.6% vs 43.8%, respectively, P < 0.05). Simulated AVNRT is associated with higher left atrial pressure compared with AVRT (19.4 +/- 4.8 mmHg vs 13.7 +/- 3.9 mmHg, respectively, P < 0.05). In dogs, pulmonary venous flow reversal during atrial systole was observed with significantly decreasing amplitude as VA delays increased: 668 +/- 167% at 0 ms; 492 +/- 138% at 100 ms; 278 +/- 148% at 180/ms; and 134 +/- 91% at 220 ms. "Shirt flapping" and "neck pounding" frequently occur during AVNRT. LA contractions during AV valve closure increase left atrial pressure and may explain differences in certain symptoms between AVNRT and AVRT.

Hypertrophic Cardiomyopathy with Preexcitation: Insights from Noninvasive Electrocardiographic Imaging (ECGI) and Catheter Mapping

Hypertrophic Cardiomyopathy and Preexcitation. Fasciculoventricular pathway has been described as an unusual variant of preexcitation. Electrocardiographic imaging (ECGI) is a novel imaging modality for noninvasive electroanatomic mapping of epicardial activation and repolarization. We present a case of an 18-year-old male with hypertrophic cardiomyopathy (HCM) and an electrocardiogram (ECG)-based diagnosis of Wolff-Parkinson-White (WPW) syndrome, who underwent a noninvasive ECGI study to image ventricular activation, followed by an electrophysiology study (EPS). The ECGI electroanatomic isochrone map showed early activation of the epicardial aspect of the atrioventricular (A-V) groove and an aberrant posterior-base-to-apex progression of activation in the left ventricular (LV) epicardium. The EPS showed a likely fasciculoventricular pathway (FVP) without any inducible tachycardia. While FVP has been described before, this is the first report of detailed quantitative three-dimensional characterization of electrical activation sequence of a heart with this type of preexcitation, using a novel noninvasive imaging modality (ECGI). In spite of abnormal ventricular activation, the EPS demonstrated that the FVP is not capable of supporting reentrant supraventricular tachycardia or rapidly conducted atrial fibrillation.

Characterization of Supraventricular Tachycardia in Infants: Clinical and Instrumental Diagnosis

Supraventricular tachycardia (SVT) is the most common symptomatic arrhythmias in children. Re-entry tachycardias are the most common form, on the contrary automatic tachycardias are relatively rare. There are four types or re-entry: along anomalous pathway with bi-directional (Wolff-Parkinson-White) or unidirectional conduction, intranodal re-entry, intra-atrial re-entry that is common after surgical procedure, and finally the uncommon sinus node re-entry. Automatic tachycardias may be atrial or junctional. The different types of tachycardia have a different incidence according to the age: in the first year of age re-entry along anomalous pathway is the dominant form, while intranodal reentry becomes common during adolescence. The age at the beginning of tachycardia is important for long term prognosis. When SVT starts in the first months of life it disappears in 80% of cases within the first year of life; on the contrary, if tachycardia starts later spontaneous remission is detected in only 15%-20% of patients. In infancy heart failure is the more common presenting symptom, thereafter palpitations become the principal cause of recognition of SVT. Syncope is reported in about 8% of cases and in another 15% usually neonates and infants, the SVT has an occasional detection. Electrocardiogram (ecg) usually allows the precise diagnosis of various types of SVT, and every effort should be made to record ecg during tachycardia. The parameters that should be evaluated are: heart rate, P wave axis, PR and RP interval, and finally presence or absence of AV block. Short lasting episodes should be difficult to be recorded; in these cases cardio-call and trans-telephonic transmission represent useful techniques to obtain SVT demonstration. Patients with SVT require a complete evaluation with others diagnostic techniques: echocardiogram, Holter monitoring, stress test, that should be chosen according the type of tachycardia. Electrophysiologic evaluation is now rarely performed for diagnostic purpose; trans-esophageal atrial stimulation being less invasive than intracardiac evaluation is more extensively employed when diagnosis of SVT is uncertain. Transesophageal stimulation is useful in the following situations: 1) evaluation of patients with symptoms suggestive of paroxistic tachycardia but without ecg documentation, 2) to assess the mechanism responsible for re-entry tachycardia: macro re-entry versus intranodal re-entry 3) to evaluate characteristics of anomalous pathway with bi-directional conduction, and 4)to terminate re-entrant SVT.