Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

Atrioventricular nodal reentrant tachycardia is the most common type of supraventricular tachycardia. The initiation and maintenance of tachycardia is caused by the characteristic anatomic and electrophysiologic properties of the atrioverntricular node. Acute management for the termination of tachycardia includes pharmacologic and non-pharmacologic management. There are several options for preventing recurrence of tachycardia, and radiofrequency ablation for modulation of tachycardia circuit can be considered as a primary strategy. A thorough understanding of the unique electrophysiologic features is very essential for optimal management and best possible outcome in cases of invasive management.

Supraventricular Tachycardia by Concealed Bypass Tract

Concealed bypass tract (CBT) results from incomplete development of the atrioventricular (AV) annulus. CBT conducts only in a retrograde direction, and therefore does not cause pre-excitation on standard electrocardiograms. The most common tachycardia associated with CBT is an orthodromic atrioventricular reentrant tachycardia (AVRT): a pathway involving anterograde circuitry through the AV node and His Purkinje system and retrograde conduction over the accessory pathway. Orthodromic AVRT accounts for approximately 90%-95% cases of AVRT. Most incidences of CBT occur at the left free wall. Vagal maneuvers and/or intravenous (IV) adenosine are recommended for first line acute management of AVRT. However, pharmacological therapy with IV diltiazem, verapamil, or beta blockers can also be effective for acute treatment for orthodromic AVRT in patients who do not show pre-excitation on their resting ECG during sinus rhythm. The first-line ongoing therapy for AVRT is catheter ablation of CBT; when catheter ablation is not indicated or preferred, oral beta blockers, diltiazem, verapamil, flecainide, propafenone, or amiodarone are recommended.

Significance of ST-segment Depression during Paroxysmal Supraventricular Tachycardia.

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.

Catheter cryoablation of atrio-ventricular nodal reentrant tachycardia. A clinical review / Crioablación con catéter de la taquicardia por reentrada intranodal. Una revisión clínica

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.

La crioablación es un nuevo método en la electrofisiología cardiaca intervensionista para la ablación percutánea de las arritmias cardiacas. El mapeo criotérmico permite la evaluación funcional de un sitio en particular antes de la ablación permanente; de esta manera, el tejido blanco puede confirmarse como seguro para el procedimiento. Esto es útil en la ablación de alto riesgo, por ejemplo, cerca del haz de His o del nodo AV compacto. En la última década, varios estudios se han orientado a la crioablación para la taquicardia de reentrada del nodo AV (TRNAV). Las experiencias actuales indican que la crioablación de la taquicardia de reentrada del nodo AV es efectiva y segura. Sin embargo, la apertura para ampliar su uso está parcialmente limitada por su eficacia ligeramente menor al compararla con el empleo de la radiofrecuencia. Se justifican ensayos clínicos futuros con objeto de evaluar el éxito a largo plazo de la ablación criotérmica en comparación con la radiofrecuencia. Para las ablaciones de alto riesgo, la crioenergía es muy útil y debería ser usada sistemáticamente. Este artículo consiste en una revisión sobre los efectos inmediatos y a largo plazo de la crioablación en pacientes que presentan episodios de taquicardia por reentrada del nodo AV.

Differences of hemodynamic changes during supraventricular tachycardias: simulation of AVRT and AVNRT in dogs / 대한내과학회지

BACKGROUND: Tachyarrhythmias have various clinical features according to their tachycardia rates, systolic function of the left ventricle, the origin site and the mechanisms. Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) might cause different hemodynamic changes due to their different mechanisms. METHODS: To evaluate the hemodynamic differences of supraventricular tachycardias, atrial tachycardia (atrial pacing with AOO mode, 180/min, group I), AVRT (VA pacing interval 80 msec with DOO mode, 180/min, group II) and AVNRT (VA pacing interval 0 msec, 25 msec with DOO mode, 180/min, group III) were simulated in eleven dogs. Hemodynamic parameters were systemic arterial pressure including systolic, mean and diastolic arterial pressure (SAP, MAP, DAP respectively), mean pulmonary arterial wedge pressure (MPAWP) and cardiac output (CO). RESULTS: The MAP was highest in group I (87.0+/-20.4 mmHg) and decreased with decreasing VA interval of no significance. The SAP was higher in group II (109.8+/-22.6 mmHg) than in group III (95.3+/-27.1 mmHg) (p<0.05). The level of MPAWP had no significant differences among three groups and showed no peculiar pattern with changes of VA interval. The CO was higher in group I (1.18+/-0.32 L/min) than in other two groups with significant difference (p<0.01) and decreased with shortening of VA interval without significance. CONCLUSION: Above results suggested that the AVRT and AVNRT have different effects on hemodynamic changes, those from different timing of atrial contraction, especially on SAP and CO. So hemodynamic compromise during tachycardia could be more severe in AVNRT than in AVRT inspite of their similar QRS morphology and tachycardia rate.

Clinical significance of accelerated junctional rhythm during slow pathway catheter ablation for atrioventricular nodal reentrant tachycardia / 中国实用内科杂志

Objective Accelerated junctional rhythm (AJR) always occur during slow pathway catheter ablation for atrioventricular nodal reentrant tachycardia (AVNRT), the clinical significance of it has not been gotten in agreement. The aim of this study is to search for an association between AJR and ablation target site or tachycardia recurrence.Methods The data of 247 patients with AVNRT who received radiofrequency ablation procedure during April 1995 to October 1999 was analyzed. All these people were divided into two groups (212 patients in the successful ablation group or group 1, 35 patients in the recurrence group or group 2). The AJR was divided into two distinct pattern:type Ⅰ(continuous AJR that persisted until the end of energy delivery) and type Ⅱ (intermit AJR alternated with sinus rhythm during slow pathway ablation, which was eliminated immediately when stopping energy delivery ). Results\ The results showed that patients in group 1 exhibited better AJR response, most of them were seen with type Ⅱ AJR. However most of the people in group 2 had no AJR response throughout energy delivery , few of them had type Ⅰ AJR response. The AJR response of group 1 started relatively earlier than that of group 2(3 2?1 8 vs 5 7?2 5 ,P

Predictors of successful catheter ablation of AV nodal reentrant tachycardia / 대한내과학회지

Catheter ablation of the AV nodal slow pathway using radiofrequency (RF) energy has been established as the first-line curative therapeutic modality of recurrent symptomatic AV nodal reentrant tachycardia (AVNRT). In contrast to catheter ablation of the AV bypass tract, there was no useful marker to localize succesful site of the pathway. This study was performed to determine predictors of successful catheter ablation of the AV nodal slow pathway in patients with AVNRT. METHODS: Forty patients (18 men, 22 women; 47.9+/-13.3 years) with AVNRT undergoing successful catheter ablation of the AV nodal slow pathway were included in this study, in which 217 attempts were tried to ablate the AV nodal slow pathway. Characteristics of local atrial electrogram, anatomical site at each attempt, junctional rhythm during RF delivery were analyzed (40 successful, 177 failed). Maximum difference and duration of atrial electrograms were measured and local atrial electrograms were classified into 5 types (A1, A2, B1, B2 and C type) according to the type and the degree of fragmentation. Finally, the occurrence of junctional rhythm during RF discharge and its onset time were compared between successful and failed attempts. RESULTS: There was no significant difference in the maximum difference of amplitude and duration of atrial electrograms between successful and failed attempts. The success rate in each type of atrial electrogram was significantly different. And, the success rate in non-C type atrial electrograms (A1, A2, B1, and B2) was significantly higher than that in type C atrial electrograms (25.0% vs 10.3%, p<0.01). No significant difference was noted in success rates according to attempted sites. Junctional rhythms during radiofrequency application occured significantly more frequent in successful attempts than in failed attempts (87.5% vs 47.5%, p<0.001). The time to onset of junctional rhythm was not different between successful and failed attempts (5.2+/-4.9 sec vs 6.1+/-5.5 sec). CONCLUSION: Fragmented local atrial electrogram and junctional rhythm during RF energy delivery may be used to predict successful catheter ablation of AVNRT. It is recommended that RF energy should be applied to the site where fragmented atrial electrogram is recorded and terminated if junctional rhythm does not develop within 15 seconds after starting RF energy delivery.

Predictors of successful catheter ablation of AV nodal reentrant tachycardia / 대한내과학회지

Catheter ablation of the AV nodal slow pathway using radiofrequency (RF) energy has been established as the first-line curative therapeutic modality of recurrent symptomatic AV nodal reentrant tachycardia (AVNRT). In contrast to catheter ablation of the AV bypass tract, there was no useful marker to localize succesful site of the pathway. This study was performed to determine predictors of successful catheter ablation of the AV nodal slow pathway in patients with AVNRT. METHODS: Forty patients (18 men, 22 women; 47.9+/-13.3 years) with AVNRT undergoing successful catheter ablation of the AV nodal slow pathway were included in this study, in which 217 attempts were tried to ablate the AV nodal slow pathway. Characteristics of local atrial electrogram, anatomical site at each attempt, junctional rhythm during RF delivery were analyzed (40 successful, 177 failed). Maximum difference and duration of atrial electrograms were measured and local atrial electrograms were classified into 5 types (A1, A2, B1, B2 and C type) according to the type and the degree of fragmentation. Finally, the occurrence of junctional rhythm during RF discharge and its onset time were compared between successful and failed attempts. RESULTS: There was no significant difference in the maximum difference of amplitude and duration of atrial electrograms between successful and failed attempts. The success rate in each type of atrial electrogram was significantly different. And, the success rate in non-C type atrial electrograms (A1, A2, B1, and B2) was significantly higher than that in type C atrial electrograms (25.0% vs 10.3%, p<0.01). No significant difference was noted in success rates according to attempted sites. Junctional rhythms during radiofrequency application occured significantly more frequent in successful attempts than in failed attempts (87.5% vs 47.5%, p<0.001). The time to onset of junctional rhythm was not different between successful and failed attempts (5.2+/-4.9 sec vs 6.1+/-5.5 sec). CONCLUSION: Fragmented local atrial electrogram and junctional rhythm during RF energy delivery may be used to predict successful catheter ablation of AVNRT. It is recommended that RF energy should be applied to the site where fragmented atrial electrogram is recorded and terminated if junctional rhythm does not develop within 15 seconds after starting RF energy delivery.

Coronary Sinus Morphology in Patients with Supraventricular Tachycardia

BACKGROUND: Coronary sinus catheterization is important in electrophysiological studies. However the mor-phologic feature of the coronary sinus and its significance in patients with supraventricular tachycardia (SVT) have not been determined. During diagnostic electrophysiological studies, coronary sinus catheterization was easier in patients with atrioventricular nodal reentry tachycardia (AVNRT) than in patients with atrioventricular reentry tachycardia (AVRT). Therefore, we studied coronary sinus morphology in patients with SVT and compared AVNRT and AVRT patients. METHODS: The size and shape of the coronary sinus were measured in 13 patients who underwent retrograde coronary sinus venogram during electrophysiologic study between May and June 1996. The diagnosis was 7 cases of AVNRT, 2 of Wolff-Parkinson-White syndrome and 4 of concealed bypass tracts (mean age, 40 years : male vs female, 1 : 1.2). RESULTS: The mean coronary sinus ostial diameter was 10.4+/-2.0 mm:for AVNRT, it was 11.4+/-2.2 mm, and for AVRT it was 9.3+/-1.0 mm in left anterior oblique projection (p=0.031). The mean coronary sinus-to-spine angle was 82.6+/-17.4degrees : AVNRT 95.4+/-24.4degrees and AVRT 67.7+/-15.2degrees in anterior posterior projection (p=0.035). CONCLUSION: The coronary sinus ostial diameter of AVNRT patients was significantly larger than that of AVRT patients. This finding may have important implications for arrythmia pathogenesis in such patients.

Electrophysiologic Factors Responsible for the Induction of AV Nodal Reentrant Tachycardia / 대한내과학회지

OBJECTIVES: Although a subtle balance between conduction time of the antgrade slow pathway and refractory period of the retrograde fast pathway is known to play the most critical role in the induction of AV nodal reentrant tachycardia(AVNRT), other electrophysiologic factors such as concealed conduction in to the fast pathway have been suggested to be responsible. The present study was performed to determine the electrophysiologic factors responsible for the induction of AVNRT. METHODS: Total 34 subjects undergoing electrophysiologic study(EPS) including 9 normal subjects(SAVNP), 7 subjects with dual AV nodal pathways(DAVNP) but no inducible AVNBT, and 18 inducible AVNRT patients were included in this study. EPS was performed using the conventional technique. To evaluate the presence of concealed conduction into the fast AV nodal pathway(FP) and its effects on the effective refractory period(ERP) of the FP (FP-ERP) to a subsequent impulse, single(A2) and double atrial extrastimuli(A2A3) were given. FP-ERP of conducted A2 [FP-ERP-A2(+)] was measured with a second atrial extrastimulus(A3) following a first atrial extrastimulus(A2), which was delivered at a coupling interval 20-30ms longer than FP-ERP. ERPs of non-conducted A2 [FP-ERP-A(-)] was measured with A3 following A2 at coupling intervals 20 ms shorter than FP-ERP. Concealed conduction was considered to be present when A1A3 interval of A3 blocked at the FP with a longest A2A3 interval was longer than FP-ERP. Concealment index(CI)-1 and CI-2 were calculated by dividing FP-ERP-A2(-) by FP-ERP-A2(+) and FP-ERP, respectively. In addition, relationship between antegrade slow pathway conduction time(A2H2) and retrograde fast pathway conduction time(HA), retrograde AV conduction system block cycle length(VA-BCL), and retrograde AV conduction system EBP(VA-ERP) was evaluated by a regression analysis. RESULTS: Concealed conduction was present in all the subjects. CI-1 was 0.63 +/- 0.04 and CI-2, 0.79 +/- 0.04 in SAVNP and 0.67 +/- 0.11, 0.68 +/- 0.07 respectively, in AVNRT patients in whom the antegrade slow pathway(SP) was ablated with catheter ablation, showing no significant difference in CI between 2 groups. At the time of induction of AVNRT with A2, A2H2. was significantly correlated with FP-ERP and FP-CT(r=OA43, p=0.04; r=0.507, p=0,02, respectively). By multivariate regression analysis, it was derived that A2H2 should be greater than "0.79 FP-ERP+1.57 FP-CT-0.44 HA-190(ms)" (r=0.71, p<0.05). CONCLUSION: Induction of typical AVNRT with A2 is determined by conduction time of the slow pathway, refractory period and conduction velocity of the fast pathway, and concealed conduction into the fast pathway.