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Objective: Catheter-based modulation of the slow pathway is the first-line therapy of atrioventricular nodal reentrant tachycardia (AVNRT), the most common supraventricular tachycardia (SVT). In patients with a typical history, in whom AVNRT is not inducible during an electrophysiological study, the current guidelines allow consideration of empirical slow pathway modulation (ESPM) under the precondition that both, dual nodal pathway physiology (DNPP) and an ECG documentation compatible with AVNRT exist. This recommendation is based on small series. Furthermore, it is unknown whether ESPM is beneficial in the presence of ECG documentation but the absence of DNPP or vice versa in the presence of DNPP but absence of ECG documentation. Methods: Out of 3003 patients who underwent slow pathway modulation from 1993 to 2013, we included 116 patients (68 female; median age 47.0 years) with symptomatic tachycardia who had non-inducible SVT. All patients either had ECG documentation of SVT (66 %) or DNPP (89 %) or both (54 %). All patients underwent ESPM. No severe complications occurred. Results: After a follow-up time of 64 ± 5.3 months, 81 % of all patients had benefited from ESPM (49 % freedom of symptoms, 32 % improvement). In patients with ECG documentation but absence of DNPP 100 % benefited (85 % freedom of symptoms; 15 % improvement). In patients with DNPP but absence of ECG documentation 75 % benefited (40 % freedom of symptoms, 35 % improvement). Conclusion: In a large cohort of patients, ESPM is a safe procedure that improves clinical symptoms in the majority of patients during long-term follow-up. We show for the first time that this also applies for cases where there is no DNPP but a characteristic ECG documentation, and vice versa. [ABSTRACT FROM AUTHOR]

Radiofrequency catheter ablation of the slow pathway is considered to be the treatment of choice for patients with atrioventricular nodal reentrant tachycardia. We report a 34-year-old female with mirror image dextrocardia due to unilateral pulmonary agenesis who underwent successful slow pathway ablation for typical atrioventricular nodal reentrant tachycardia. Using contrast injection, cardiac anatomy was identified in a short time and successfully ablated. [ABSTRACT FROM AUTHOR]

Background The data supporting the practice of empiric slow pathway ablation (ESPA) in patients with documented supraventricular tachycardia (SVT) who are non-inducible at electrophysiology study (EPS) is limited. The aim of this study is to assess the efficacy of ESPA in adults. Methods A multi-center cohort study of patients who had ESPA between January 2008 and October 2013 was performed. Patients were identified by screening sequential SVT ablation procedures. Results Forty-three (5%) out of 859 SVT ablation procedures were identified as ESPA. The median age was 53 (IQR: 24) years; 63% were female. All patients had pre-EPS documentation of SVT (either strip or ECG). In 23 (53.5%) cases, pre-EPS ECG showed short RP tachycardia. Thirty-two (74.4%) patients had dual atrioventricular nodal physiology (DAVNP) plus echo beats. Junctional rhythm (JR) as procedural endpoint was noted in 39 (90.7%) patients. In 18 (41.9%) patients, the abolishment of DAVNP was achieved. No complications were encountered. A median follow-up of 17 months (range: 6 to 31 months) revealed 83.7% (36 of 43) success rate, defined as the absence of pre-procedural symptoms and any documented sustained arrhythmia. As compared to patients with recurrence (n = 7), patients with no recurrence (n = 36) had significantly higher prevalence of clinical short RP tachycardia (61.1% vs. 14.3%, p = 0.038), and EPS finding of DAVNP plus echo beats (80.6% vs. 42.9%, p = 0.034). Conclusions ESPA is a reasonable approach in patients with documented SVT, in particular in short RP tachycardia, who are not inducible at EPS. Larger studies are required to assess this practice. [ABSTRACT FROM AUTHOR]

Background: ST-segment depression in ECG is a common finding during paroxysmal supraventricular tachycardia. The exact mechanism and etiology of this ST-segment depression is not always evident. In this study we have tried to evaluate the significance of ST-segment depression during supraventricular tachycardia. Methods: Hospitalized patients for elective electrophysiological study with previous (EPS) history of supraventricular tachycardia with or without ST-segment depression were evaluated clinically, by coronary angiogram and EPS. Data were analyzed by appropriate statistical methods and comparison made between groups with ST-segment depression (Group A) and without ST-segment depression (Group B). Results: Total number of patients was 66. Equal number of patients (33) was in each group. The mean age of patients was 43.8 years. There was female predominance (M:F ratio 2:3). The mean heart rate during supraventricular tachycardia was 161 beats/min. Age, sex, coronary artery disease risk factors and heart rate during an episode of supraventricular tachycardia did not have any significant influence on ST-segment depression. Significant coronary artery disease was found in two patients in Group A and one patient in Group B. Electrophysiological study revealed that Atrio ventricular reentry tachycardia (AVRT) and AV nodal reentry tachycardia (AVNRT) were present in 28 (42.4%) and 38 (57.6%) cases respectively. Patients of group A exhibit AVRT significantly more than patients of group B.The sensitivity of ST-segment depression in correctly diagnosing coronary artery disease (CAD) was 66.7% while the specificity was 50.8%. The sensitivity of ST-segment depression in correctly differentiating AVRT was 83.3% while the specificity was 66.7%. The positive predictive value (PPV) and Negative predictive value (NPV) of the test were 75% and 76.9% respectively. Conclusion: ST-segment depression during episode of supraventricular tachycardia is a poor indicator of coronary artery disease. Presence of ST-segment depression can differentiate AVRT from AVNRT. However, >2 mm ST-segment depression was proved to be an excellent predictor of AVRT. [ABSTRACT FROM AUTHOR]

A 66-year-old woman with palpitations was referred to our center for catheter ablation due to drug-refractory, common type atrioventricular nodal tachycardia (AVNRT). A selective slow pathway ablation was attempted. A fast junctional rhythm with transient ventriculoatrial block followed by transient prolongation of the A–H interval occurred immediately after the radiofrequency (RF) application at the coronary sinus ostium (CSOS) level. To assess the location of the fast pathway and His bundle, we sought to visualize the anatomy of the triangle of Koch (TOK) by three-dimensional computed tomography (CT). [ABSTRACT FROM AUTHOR]

The article presents a case study of a 44-year-old woman with idiopathic dilated cardiomyopathy who have rescued by dual-chamber Boston Scientific Teligen 100 implantable cardioverter defibrillator (ICD). Topics discussed include electrophysiological study with induction of atrioventricular nodal reentrant tachycardia (AVNRT); continuous rhythm monitoring; and using device tracings and application of principles making successful rescuing.

'2 for 1 phenomenon' is simultaneous anterograde conduction over the fast and slow pathways of the atrioventricular (AV) nodal pathway, leading to a double ventricular response from each atrial beat. This phenomenon can initiate AV nodal reentrant tachycardia (AVNRT). The unique induction of AVNRT was observed in a patient with an implantable cardioverter defibrillator in our case. Minimal to no retrograde invasion of the slow pathway from the anterogradely conducted fast pathway depolarization is the most accepted explanation. [ABSTRACT FROM AUTHOR]

Background The incidence and electrocardiographic characteristics of atrial tachycardia (AT) among long RP tachycardias have not been fully elucidated. Methods and results Thirty-six patients with 37 long RP tachycardias were classified as having AT ( n =23) or non-AT ( n =14). We analyzed the electrocardiographic features, including the ratio between the RP and PR intervals (RP/PR ratio), P-wave morphology, and P-wave duration. The RP/PR ratio was higher in AT than in non-AT (2.01±0.54 vs. 1.57±0.24, P <0.001). A negative P wave in the inferior leads was less common in AT (4/23 vs. 13/14, P <0.01). The P-wave duration was longer in AT than in non-AT (105±13 ms vs. 84±10 ms, P <0.001). The fulfillment of any 2 of the following had a specificity and a positive predictive value of 100% for AT: RP/PR ratio of ≥1.65, absence of negative P wave in the inferior leads, or a P-wave duration of >96 ms. Conclusion AT accounted for nearly two thirds of long RP tachycardias in this cohort. Electrocardiographic features, including the RP/PR ratio, polarity of the P wave, and P-wave duration were useful in the differentiation of AT. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to retrospectively investigate clinical and electrophysiologic characteristics of typical AVNRT with relatively slow tachycardia rates below the average value compared to faster ones, in patients without structural heart disease. Methods: The present study retrospectively included a total of 1,150 patients receiving successful slow-pathway radio frequency ablation for typical slow-fast AVNRT. Patients were divided into two groups according to their tachycardia cycle length: group I included 1,018 patients with tachycardia cycle length < 400 msn and group II included 132 patients with cycle length > 400 msn. Patients with another form of arrhythmia other than typical AVNRT, the existence of structural heart disease, preexisting prolonged PR interval, history of clinically documented AF, and reasons capable of causing AF were accepted as exclusion criterias. Results: The patients in group II were older than those in group 1 ( p=0.039), and male ratio was significantly higher in group II compared to group I ( p=0.02). Wenckebach cycle length and AV node antegrade effective refractory period values before the RF ablation were significantly higher in group II compared to group I ( p=0.0001 and 0.01, respectively). Right atrium effective refractory period values in both pre- and post-ablation period were significantly higher in group I compared to group II ( p=0.0001 and 0.004, respectively). The existence of atrial vulnerability before ablation was significantly higher in group II compared to group I ( p=0.007); however, there was no difference between the two groups in terms of atrial vulnerability after the ablation. In addition, while the ratio of anterior location as an ablation site near the His-bundle region was significantly higher in group II, the ratio of posterior location was significantly higher in group I ( p=0.0001 for both). Conclusion: Our experience demonstrates that clinical and electrophysiologic characteristics of AVNRT patients with relatively slower tachycardia rates were quite different compared to the faster AVNRT cases. [ABSTRACT FROM AUTHOR]

Introduction: Mapping of the antegrade fast pathway (A-FP) exact sites and antegrade slow pathway (A-SP) input locations has not been well described. Methods: In 56 patients with slow-fast atrioventricular nodal reentrant tachycardia (SF-AVNRT), pacing during sinus rhythm and entrainment pacing during SF-AVNRT were performed at various sites in the triangle of Koch and coronary sinus (CS) to identify the A-FP and A-SP inputs. User-defined threedimensional electro-anatomical mapping of the stimulus-His potential (St-H) interval and anatomical location was performed. The A-FP input was defined as the site of the shortest St-H interval, and A-SP input as the site of the shortest St-H interval and with a postpacing-interval equal to the tachycardia cycle length. The locations of the A-FP and A-SP inputs were mapped as a ratio of the distance between the His bundle (HB) and CS orifice (CSO), and the HB-CSO axis was divided into three zones: superior-, mid-, and inferior septum. The distance between the A-SP and A-FP inputs was calculated using the distance from each input to the HB and HB-CSO axis. Results: Only 30 patients were included in this study because the A-SP mapping failed in 26. The A-SP input was distributed to the superior septum in four, mid- or inferior septum in 25, and CS in one. An A-SP input which was located less than 10 mm from the A-FP input was observed in one of four patients with a superior septum A-SP. Conclusions: An A-SP input at the superior septum seemed to be a potential risk for atrioventricular nodal injury during ablation. [ABSTRACT FROM AUTHOR]

Aims Radiofrequency (RF) ablation is effective for ablation of atrial arrhythmias. However, RF ablation in the vicinity of the atrioventricular (AV) node is associated with a risk of inadvertent, irreversible high-grade AV block, depending on the type of substrate. Cryoablation is an alternative method. The objective was to investigate the acute and long-term risks of AV block during cryoablation. Methods and results We studied 1303 consecutive cryoablations of substrates in the vicinity of the AV node in 1201 patients (median age 51 years, range 6–89 years) on acute and long-term impairment to the AV nodal conduction system. The arrhythmias treated were AV nodal reentrant tachycardias (n=1116), paraseptal and superoparaseptal accessory pathways (n=100), and focal atrial tachycardias (n=87). In 158 (12%) procedures, cryomapping (38 cases) or cryoablation (120 cases) were stopped due to transient AV block (first-degree AV block 74 cases, second-degree AV block 67 cases, and third-degree AV block 17 cases) after which another site was tested. Transient AV block occurred within seconds of mapping up to 3 min of ablation. The incidence of AV block was similar for different substrates. In most cases, AV nodal conduction was restored within seconds but in two cases transient AV block lasted 21 and 45 min, respectively. There were no cases of acute permanent AV blocks. No late AV blocks occurred during follow-up (mean 24 months, range 6–96 months). Conclusion Cryoablation adjacent to the AV node carries a negligible risk of permanent AV block. Transient AV block during ablation is a benign finding. [ABSTRACT FROM PUBLISHER]

Meta-Analysis of Cryoablation for AVNRT Introduction Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common supraventricular tachycardia referred for ablation. High success rates have been accompanied with a small risk of atrioventricular (AV) block. Cryoablation has been used as an alternative to radiofrequency (RF) ablation, but studies have been underpowered in comparing the 2 techniques. Methods and Results An electronic search and hand-search of reference lists for published and unpublished data was carried out. Comparative studies (cohort and randomized controlled trials) of RF versus cryoablation for AVNRT were identified independently by 2 reviewers. Searches were limited to English language human studies. The primary metameter was long-term AVNRT recurrence (>2 months postprocedure and ECG/electrophysiology study [EPS]-documented) and secondary metameters included acute procedural failure and AV block requiring pacing. A total of 5,617 patients in 14 trials were included in this systematic review. Acute procedural failure with cryoablation was slightly higher than with RF ablation, but the difference was not statistically significant (risk ratio [RR] 1.44 [95% confidence interval; CI 0.91-2.28], P = 0.12). Long-term recurrence was higher with cryoablation (RR 3.66 [95% CI 1.84-7.28], P = 0.0002) even after adjusting for larger (6 mm) cryocatheter tips, 'insurance lesions' and longer (>6 months) follow-up duration. RF ablation for AVNRT was associated with permanent AV block in 0.75% of patients, but was not reported in any patients treated with cryoablation (n = 1066, P = 0.01). Conclusions Cryoablation is a safe and effective treatment for AVNRT. Although late-recurrence is more common with cryoablation than with RF ablation, avoidance of permanent AVN block makes it an attractive option in patients where the avoidance of AV block assumes higher priority (such as children and young adults). [ABSTRACT FROM AUTHOR]

Background Anatomical considerations and risks related to x-ray exposure make atrioventricular nodal reentrant tachycardia (AVNRT) ablation in pediatric patients a concerning procedure. We aimed to evaluate the feasibility, safety, and efficacy of performing fluoroless slow-pathway cryoablation guided by the electroanatomic (EA) mapping in children and adolescents. Methods Twenty-one consecutive patients (mean age 13.5 ± 2.4 years) symptomatic for AVNRT were prospectively enrolled to right atrium EA mapping and electrophysiological study prior to cryoablation. Cryoablation was guided by slow-pathway potential and performed using a 4-mm-tip catheter. Results Sustained slow-fast AVNRT was inducible in all the patients with a dual AV nodal physiology in 95%. Acute success was achieved in 100% of the patients with a median of two cryo-applications. Fluoroless ablation was feasible in 19 patients, while in two subjects 50 seconds and 45 seconds of x-ray were needed due to difficult progression of the catheters along the venous system. After a mean follow-up of 25 months, AVNRT recurred in five patients. All the recurrences were successfully treated with a second procedure. In three patients, a fluoroless cryoablation with a 6-mm-tip catheter was successfully performed, while in the remaining two patients, a single pulse of 60 seconds of radiofrequency energy was applied under fluoroscopic monitoring. No complications occurred. Conclusions Combination of EA mapping systems and cryoablation may allow to perform fluoroless slow-pathway ablation for AVNRT in children and adolescents in the majority of patients. Fluoroless slow-pathway cryoablation showed a high efficacy and safety comparable to conventional fluoroscopy guided procedures. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Right ventricular entrainment represents a useful tool for differentiating atrioventricular nodal re-entrant tachycardia (AVNRT) from orthodromic re-entrant tachycardia (ORT) using an accessory pathway. However, inability to entrain PSVT by pacing can be observed in some patients. Aim of study: Assessing whether the resetting response to SVT by single or double right ventricular extra-stimuli is a useful maneuver to differentiate AVNRT from OAVRT by calculating the difference between the stimulus-atrial interval during resetting of SVT and the VA interval during SVT (SA–VA). Methods: Electrophysiological study was conducted with a calculation of the SA–VA interval after resetting of the tachycardia by ventricular extra stimulus and differential entrainment from RV apex and base, then comparing the two methods regarding sensitivity and specificity in differentiating AVNRT from OAVRT conducted on 25 patients. Results: Measuring the SA–VA interval after resetting of the tachycardia by an extra stimulus during the His refractoriness during the tachycardia showed in AVNRT a mean of 145.76±31.53 and in OAVRT a mean±SD of 91.52±12.79 with a high statistical significance, with a cutoff point of 107ms above which the SVT is expected to be AVNRT, and below which OAVRT. Using this technique could differentiate AVNRT from OAVRT with an overall sensitivity of 100% and specificity of 76.47%, in comparison to a specificity of 81.8% when using the technique of differential entrainment from RV apex and base. Conclusion: Resetting of SVT by ventricular extra-stimuli is a useful maneuver for differentiating AVNRT from ORT and is applicable even when entrainment is impossible. [Copyright &y& Elsevier]

Abstract: Introduction: Radio frequency ablation of the slow pathway has become first-line therapy for the elimination of AV nodal reentrant tachycardia (AVNRT). Slow pathway ablation is guided by a combination of fluoroscopic landmarks, electrogram morphology, and the induction of accelerated junctional rhythm (JR) during the application of radiofrequency energy. Although JR occurs usually during slow pathway ablation of AVNRT, the pattern of JR has not been adequately studied.13 Aim of the study: To investigate in detail the characteristics of junctional rhythm occurring during radiofrequency ablation of atrioventricular nodal reentrant tachycardia AVNRT among Egyptians. Methods: This study included 30 patients who underwent electrophysiological study for narrow complex supraventricular regular tachycardia which revealed to be AVNRT. Results: Thirty (100%) patients showed induction of junctional rhythm at the successful ablation sites. JR was a very sensitive predictor of successful ablation but not so specific with specificity of 60%. Sex patterns of JR were observed. The most common pattern of JR was sinus–junctional–junctional (SJJ) while sinus–junctional-block (SJB) was the least. The most specific pattern for effective ablation was junctional–junctional–junctional (JJJ), while intermittent burst was the least. P value is 0.001 i.e. highly significant. Conclusion: Junctional rhythm is a sensitive predictor of successful ablation. The pattern of JR is a useful predictor of successful ablation. Egyptian population has distinctive patterns of JR during AVNRT ablation. [Copyright &y& Elsevier]

Exercise-related palpitations, vertigo, and syncope may be caused by benign etiologies but can also herald life-threatening arrhythmias. The precise diagnosis of these findings is therefore essential and potentially life saving but often is a challenge for sports physicians and cardiologists. Leadless, ambulatory HR monitors with chest strap transmitters have been designed to steer exercise intensity in athletes with a baseline sinus rhythm. However, they also can capture arrhythmias. Presented here are three cases of varying arrhythmias: atrial fibrillation, atrioventricular nodal reentrant tachycardia, and ectopic atrial tachycardia that demonstrate the utility of HR monitors designed for athletic purposes in facilitating the diagnosis of arrhythmias and guiding appropriate treatment. [ABSTRACT FROM AUTHOR]

Background Inducibility of sustained tachycardia is preferred prior to cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT). Method The Pediatric Electrophysiology Database of a single institution was retrospectively reviewed for patients with clinical sustained (≥30 seconds of symptoms) AVNRT documented by noninvasive means who underwent cryoablation for AVNRT to determine if intermediate-term success with cryoablation for AVNRT can be achieved without inducibility of sustained AVNRT during electrophysiology study (EPS). Results There were no differences between patients with sustained (≥30 seconds of tachycardia) AVNRT (N = 67) and patients with nonsustained (ns, ≥3 beats and <30 seconds of tachycardia) AVNRT at EPS (N = 16). Acute success was achieved without PR prolongation in all patients. Although duration of follow-up was shorter for the sustained group than the nonsustained group (2.7 ± 1.6 years vs 3.8 ± 1.4 years, P = 0.008), recurrence rate was similar (6% vs 6.3%, P = 0.6). In patients with only nonsustained AVNRT at EPS, supportive findings for procedural effectiveness seen: (1) Dual atrioventricular node physiology (DAVNP) was eliminated in 14/14, (2) the fast pathway effective refractory period (FPERP) decreased after ablation in 10/11, (3) sustained slow pathway conduction was eliminated in 8/8 including both patients without discrete DAVNP prior to ablation, and (4) FPERP increased during lesion formation in 10/10. Conclusion Intermediate-term success can be achieved with cryoablation of ns AVNRT. Attention should be paid to supportive indicators of damage to slow pathway. [ABSTRACT FROM AUTHOR]

Aim: Dual atrioventricular nodal physiology (DAVNP) is a frequent finding in patients with suspected or documented supraventricular tachycardia (SVT). Empiric slow pathway ablation (ESPA) is sometimes performed in patients with DAVNP without inducible SVT at the time of electrophysiological study. Evidence to guide this practice in the adult population is limited. This study was aimed to assess the practice of ESPA by adult electrophysiologists in Canada. Methods: All Canadian interventional electrophysiologists ( n = 81) were invited to complete a web-based questionnaire assessing their practice of ESPA in patients with suspected and documented SVT. Operator experience, reimbursement models, diagnostic, and treatment decisions regarding ESPA were assessed with case scenarios. Results: Forty-one responses (50 %) were obtained. Ninety-five percent of the responders stated that the evidence for ESPA is lacking or limited. Responders were more likely to perform ESPA in the setting of non-inducible SVT when there was documentation of the clinical arrhythmia (64 vs. 31 % ( p = 0.017)). The threshold to perform ESPA was highly variable. Longer time in practice ( r = 0.38, p = 0.017) and less perceived complications with ESPA ( r = 0.31, p = 0.05) were correlated with the practice of ESPA, whereas length of ablation waiting lists ( r = −0.15, p = 0.38), number of procedures performed per day ( r = 0.11, p = 0.51) and type of reimbursement ( p = 0.24) were not associated with the practice of ESPA. The perceived complication rate with ESPA was <1 %. Conclusion: Variability in the practice of ESPA in cases of non-inducible SVT exists. Documentation of the clinical arrhythmia, operator experience, and perceived low complication rates positively influence this practice. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to assess memory functioning among children and adolescents with atrial-ventricular nodal re-entry tachycardia (AVNRT) and atrial-ventricular re-entry tachycardia (AVRT). Material/ Methods: A total of 113 pediatric cardiology clinic patients (62 F, 51 M), aged 9-18 years, who were scheduled for radiofrequency ablation due to AVRT or AVNRT underwent neuropsychological examination. Patients who had suffered a cardiac arrest, or had a congenital heart defect, neurological disorders or other diseases affecting cognitive or emotional development were excluded from the study. The control group consisted of 41 patients diagnosed at the same clinic who did not show any significant cardiovascular or nervous system disorders. Standardized tests were used to measure verbal and visual memory and visuo-spatial functions (Auditory-Verbal Learning Test, Benton Visual Retention Test and Rey's Complex Figure Test). Results:cognitive disorders were found significantly more frequently in the study group (47.8%) than in the control group (22%; Chi2=8.30, p=0.004). An early age at the onset of attacks, especially under the age of six, was an important factor that negatively affected cognitive functioning (Chi2=3.87, p=0.04). Conclusions: AVNRT and AVRT in childhood have adverse effects on cognitive and emotional development. [ABSTRACT FROM AUTHOR]

A case of radiofrequency catheter ablation of atrioventricular (AV) nodal reentry tachycardia, in a patient with transposition of the great arteries after venous rerouting according to Mustard, is described. An electroanatomical map of the His and AV nodal region was created from inside the systemic venous atrium. Retrograde mapping of the pulmonary venous atrium was performed and the arterial catheter retracted to a position in close proximity to the venous catheter inside the intraatrial baffle. This position was chosen to deliver radiofrequency current. (PACE 2012; 35:e287-e290) [ABSTRACT FROM AUTHOR]

The article presents a case study of a 43 year old female patient who presented to an emergency room with heart palpitations and received a diagnosis of irregular narrow complex tachycardia. A discussion of the mechanisms which could have led to the patient's narrow complex tachycardia is presented.

Slow-pathway ablation is the treatment of choice for atrioventricular nodal reentrant tachycardia (AVNRT). Cryoablation is effective and safe, but its widespread use seems to be limited by a slightly lower long-term clinical efficacy when compared to radiofrequency (RF) ablation. However, the occurrence of atrioventricular block requiring permanent pacing with RF remains clinically relevant (about 1%). This review summarizes current experiences accumulated during the last decade with cryotechnology in terms of acute and long-term results for AVNRT and compares it with those of RF ablation. We describe the advantages of cryo compared to RF ablation. Our data suggest that pursuing procedural endpoint up to slow pathway complete ablation may improve long-term clinical success of cryoablation. We also focus on potential benefit that can be expected by using cryocatheters leading to larger and deeper freeze. For high-risk ablations, cryoenergy should be used systematically. (PACE 2012; 35:233-240) [ABSTRACT FROM AUTHOR]

The article discusses the mechanism in repetitive nonsustained supraventricular tachycardia. The case involves the onset of unsustained narrow complex tachycardia with variable ventriculoatrial relationship in a 59-year-old woman. A differential diagnosis includes junctional ectopic tachycardia, atroventricular (AV) nodal reentry tachycardia, multifocal atrial tachycardia with bystander accessory pathway, or focal atrial tachycardia combined with orthodromic AV reentry.

Purpose: Modification of the slow pathway (SP) of the atrio-ventricular node by radiofrequency ablation is the most effective treatment to cure AV nodal reentry tachycardia (AVNRT). However, this therapy may be complicated by AV-block (AVB). We sought to evaluate the predictive value of the A(H) -A(Md) interval-the electrical delay between atrial signals on the His- and the ablation-catheter-upon development of AVB during SP ablation. Methods: The associations between A(H) -A(Md) interval, occurrence of ventriculo-atrial block (VAB) during junctional activity (JA) and transient or permanent AVB were analyzed retrospectively for 1585 RF applications at the SP in 393 patients diagnosed with AVNRT. The value of A(H) -A(Md) was further tested prospectively in 118 AVNRT patients, who were only ablated at targets with intervals >20 ms. Results: Forty-six RF deliveries resulted in transient or permanent AV-conduction disturbances. Shorter A(H) -A(Md) intervals were associated with the occurrence of VAB during JA ( p < 0.001) and AVB ( p < 0.001). A(H) -A(Md) was the strongest predictor for VAB or AVB in multivariate regression analyses, followed by the radiological distance between the catheters. In the prospective study, permanent high-degree AVB was not observed when the A(H) -A(Md) at the ablation site was >20 ms. Conclusion: The A(H) -A(Md) interval is a better predictor for occurrence of conduction block during ablation for AVNRT than the radiological distance between the His- and the ablation-catheter. The risk of permanent AVB can be minimized, if only sites with an A(H) -A(Md) longer than 20 ms are targeted for ablation. [ABSTRACT FROM AUTHOR]

The author reflects on atrioventricular node reentrant tachycardia and on the article "Spontaneously Alternating Forms of the Atrioventricular Node Reentrant Tachycardia," by X. Liu, T. Liu, M. Shehata, A. Nahapetian, A. Amorn, S. Chugh and X. Wang. He suggests that reentrant tachycardia is in many ways the poster child for invasive cardiac electrophysiology. He argues that the research which Liu did should serve as an example for all who see phenomena in the electrophysiology laboratory.

Dual atrioventricular (AV) nodal physiology is a substrate for the development of AV nodal reentrant tachycardia (AVNRT). However, the risk of developing AVNRT in patients with dual AV nodal physiology is not known. The purpose of this study is to identify the risk of developing AVNRT in children and adolescents with incidental findings of dual AV nodal physiology after accessory pathway ablation. This is a single center retrospective study of patients who underwent intracardiac electrophysiology study at The Children's Hospital, Denver, from March 1993 to August 2008, with findings of dual AV nodal physiology after successful ablation of an accessory pathway. Follow-up was obtained by chart review with the primary outcome of recurrent supraventricular tachycardia. Extended clinical follow-up was also achieved through phone contact with patients or parents of patients. Mean age at initial electrophysiology study was 12.8 years (±3.7 years). Follow-up was obtained on all 66 patients for a mean duration of 3.1 years (±2.8 years). Mean age at follow-up was 15.8 years (±4.6 years). Recurrent supraventricular tachycardia occurred in nine of the 66 patients (13.6%). AVNRT was induced in two of the 66 patients (3.0%). This study supports the hypothesis that incidental dual AV nodal physiology does not predict AVNRT in children and adolescents with after successful accessory pathway ablation. (PACE 2010; 33:1528-1532) [ABSTRACT FROM AUTHOR]

Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentry tachycardia (AVNRT). The difference in the entrainment response from the RV apex in comparison with the RV base has not been tested. Fifty-nine consecutive patients referred for ablation of supraventricular tachycardia (SVT) were included. Entrainment of SVT was performed from the RV apex and base, pacing at 10-40-ms faster than the tachycardia cycle length. SA interval was calculated from stimulus to earliest atrial electrogram. Ventricle to atrium (VA) interval was measured from the RV electrogram (apex and base) to the earliest atrial electrogram during tachycardia. The SA-VA interval from apex and base was measured and the difference between them was calculated. Thirty-six AVNRT and 23 AVRT patients were enrolled. Mean age was 44 ± 12 years; 52% were male. The [SA-VA]apex-[SA-VA]base was demonstrable in 84.7% of patients and measured −9.4 ± 6.6 in AVNRT and 10 ± 11.3 in AVRT, P < 0.001. The difference was negative for all AVNRT cases and positive for all septal accessory pathways (APs). The difference between entrainment from the apex and base is readily performed and is diagnostic for all AVNRTs and septal APs. (PACE 2010; 1335-1341) [ABSTRACT FROM AUTHOR]

Cryoablation is a new method in interventional cardiac electrophysiology for percutaneous catheter ablation of cardiac arrhythmias. Cryothermal mapping enables the functional assessment of a particular site before permanent ablation. In this way, the targeted tissue may be confirmed as safe for ablation. This is useful in high-risk ablation, for example, next to the His bundle or the compact AV node. In the last decade, several studies have been addressed to AV-nodal reentry tachycardia (AVNRT) cryoablation. Current experiences indicate that cryoablation for AV-nodal reentry tachycardia is effective and safe. However, its wide use seems to be somewhat limited by a slightly lower efficacy when compared to radiofrequency. Further studies evaluating long-term success of cryothermal ablation versus radiofrequency are warranted. However, for high-risk ablations, cryoenergy is very helpful and should be systematically used. This article is a review of acute and long-term effects of cryoablation in patients suffering of AV-nodal reentry tachycardia episodes. [ABSTRACT FROM AUTHOR]

Background: Cryoablation with 4- and 6-mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid-term outcomes, and complications related to the use of the 8-mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. Methods: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8-mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. Results: Cryoablation with an 8-mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 ± 2.2 years, weight 62.0 ± 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second- or third-degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow-up of 11.6 ± 3.3 months. Conclusion: Cryoablation with an 8-mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients. (PACE 2010; 33:681–686) [ABSTRACT FROM AUTHOR]

The article presents the case study of a 67-year-old retired police officer who had an episode of sustained monomorphic wide complex tachycardia that required defibrillation. The patient's physical condition is discussed who felt light-headed and fatigued. The results of the patient's laboratory examinations including coronary angiography and transthoracic echocardiogram which led to the diagnosis of tachycardia.

Aim: To present our center's experience of AVNRT ablation with two-catheter ablation technique. Methods and Results: 276 patients with the diagnosis of typical AVNRT were finally included into the study. Slow pathway ablation was performed with twocatheter ablation technique. Successfull ablation was obtained in 275 patients (99.6%). The procedure and fluoroscopy times were 48 ± 4.5 and 15.3 ± 3.2 minutes, respectively. Complications occurred in 7 (2.5%) patients. None of the ablations were resulted in complete AV block requiring pacemaker. Conclusion: Two-catheter AVNRT ablation technique could be performed with shorter fluoroscopic and total procedural times, less complication rates and low cost; therefore could be regarded as quick, safe and cost-effective treatment modality with experienced operators. [ABSTRACT FROM AUTHOR]

Introduction: Radiofrequency catheter ablation aiming slow pathway modulation is a widely established procedure with high success and low recurrence rates in patients with atrioventricular nodal reentry tachycardia (AVNRT). However, the necessity of a waiting period following successful slow pathway modulation to increase the long-term success rates has not been systematically evaluated thus far. Methods and Results: This prospective study comprised 138 consecutive patients (mean age 50.3 ± 15.1 years) with AVNRT. These patients were randomly assigned to two groups: in group I (n = 70), a waiting period of 30 min was part of the procedure, whereas in group II (n = 68), the procedure ended without a waiting period. Electrophysiological standard parameters, i.e., ERP of RA, fast and slow pathway, RV as well as antegrade and retrograde AV node conduction capacity, were assessed prior to and after the ablation. During a follow-up period of 22.8 ± 5.9 months, four patients in group I and three patients in group II developed recurrence of AVNRT (4.9%; P = 0.4). The mean procedure time was 115.1 ± 23.6 min in the group with and 88.9 ± 23.3 min in the group without waiting period (P = 0.009). No high degree AV-node conduction block was observed during the study. Conclusion: In the present study we could show that no long-term benefit results from a 30 min waiting period for patients who underwent an acutely successful catheter ablation for AVNRT. We therefore conclude that a 30-min waiting period can be omitted in standard procedures, thus resulting in significant shorter procedure durations. [ABSTRACT FROM AUTHOR]

Background Supraventricular tachycardia (SVT) is a common tachyarrhythmia among pediatric patients. Usually, non-preexcited SVT is attributable to either atrioventricular nodal reentry tachycardia (AVNRT) or unidirectional retrograde accessory pathway (URAP), but these cannot be differentiated on a baseline electrocardiogram (ECG). The ability to identify the SVT mechanism in children may guide decision-making about treatment and counseling regarding electrophysiology study (EPS). Clinical experience suggested that ectopic atrial rhythm (EAR) is more frequently observed on preablation ECGs of pediatric patients with AVNRT. This study aimed to determine whether EAR is predictive of AVNRT. Methods A 10-year single-center retrospective review was conducted with patients who underwent ablation for SVT from 1997 through 2006. All pediatric patients with documented AVNRT or URAP during EPS were included. The exclusion criteria specified prior ablation, Wolff-Parkinson-White syndrome, or complex congenital heart disease. A patient was considered to have EAR if a preablation ECG had a p-wave axis less than 0° or greater than 90° or a wandering atrial pacemaker with at least three different p-wave morphologies. Results The review found 457 eligible patients ages 0.5 to 21 years: 285 with AVNRT and 172 with URAP. Patients with congenital heart defects represented 5.6% of the AVNRT group and 2.9% of the URAP group. Ectopic atrial rhythm was seen in 45 (16%) of 285 patients with AVNRT compared with 10 (6%) of 172 URAP patients ( p = 0.001). The sensitivity and specificity of EAR for AVNRT was 16% and 94%, respectively, and the positive predictive value was 82%. There was no difference in heart rate or QRS duration between the two groups. Conclusion On preablation ECG for pediatric SVT patients, EAR is a reasonably specific marker for AVNRT. [ABSTRACT FROM AUTHOR]

Abstract: As many as 1 in 250 children experience supraventricular tachycardia (SVT), but its presentation is often vague and its symptoms mistakenly attributed to other common pediatric conditions. If SVT is correctly identified in a timely manner, most children will go on to live normal healthy lives. SVT is not covered in depth in most pediatric advanced practice nursing programs, but because of its prevalence, it should be familiar to all pediatric primary care providers. This article reviews common mechanisms of SVT and their age-related presentation, diagnosis, and management. A case study of an 8-year-old boy with SVT is presented. [Copyright &y& Elsevier]

Abstract: Background: Emergence of junctional rhythm (JR) during radiofrequency (RF) current delivery directed at the periatrioventricular nodal region has been shown to be a marker of success in atrioventricular nodal reentrant tachycardia (AVNRT). Whereas the characteristics of JR during RF ablation of slow pathway have already been studied, the electrophysiologic features of different patterns of JR are yet to be evaluated. The aim of this study was to investigate in detail the characteristics of the JR that develops during the RF ablation of the slow pathway. Materials and Results: The study population consisted of 95 patients: 56 women and 33 men (mean age, 47.2 ± 16.3 years) who underwent slow pathway ablation because of AVNRT. A combined anatomical and electrogram mapping approach was used, and AVNRT was successfully eliminated in all patients. This study identified 7 patterns for JR during the RF ablation of slow pathway: junction-junction-junction, sinus-junction-sinus, intermittent burst, sparse, no junction, sinus-junction-junction, and sinus-junction-block . The characteristics of JR, such as mean cycle length and total number, were gathered. The incidence of JR was significantly higher during effective applications of RF energy than during ineffective applications (P = .001). The mean number of junctional ectopy was 19.6 ± 19. The total number of junctional ectopy was significantly higher during effective applications of RF energy than during ineffective applications (24.6 ± 18.8 vs 8.4 ± 13.2; P < .001). We found a significant difference between the effective and ineffective applications of RF energy in the mean cycle length of the junctional ectopy (464.6 ± 167.5 vs 263.4 ± 250.2; P < .01). The patterns of JR were compared between effective and ineffective applications. We managed to show a significant correlation between patterns of JR and successful ablation (P = .01). Logistic regression analysis revealed that the presence of sinus-junction-sinus, sinus-junction-junction, and sinus-junction-block patterns of JR was a predictor of a successful RF ablation (confidence interval [CI], 1.67-15.92 [P < .004]; CI, 1.02-85.62 [P = .048]; and CI, 1.06-32.02 [P = .042], respectively). Conclusion: This study confirms that JR is often present during successful slow pathway ablation. The pattern of JR is useful as indicator of success. [Copyright &y& Elsevier]