Comparison of Atrial-His Intervals During Tachycardia and Atrial Pacing in Patients with Long RP Tachycardia

Long RP Tachycardia. Introduction : The purpose of this study is to describe a simple and reliable diagnostic maneuver that allows for the rapid differentiation of atypical AV nodal reentrant tachycardia (AVNRT) from other causes of long KP tachycardia. Long RP tachycardias may he caused by atypical AVNRT, orthodromic reciprocating tachycardia (ORT) involving a slowly conducting retrograde accessory pathway, or atrial tachycardia. The differentiation of atypical AVNRT from ORT or atrial tachycardia may be difficult, especially when the differential diagnosis includes a posteroseptal accessory pathway or an atrial tachycardia arising in the posteroseptal right atrium.
Methods and Results : Twelve patients with atypical AVNRT, 21 with ORT, and 12 with an atrial tachycardia diagnosed using conventional criteria were enrolled In this study. The atrial-His (AH) interval was measured at the His-bundle position during the tachycardia and during atrial pacing from the high right atrium at the tachycardia cycle length in the setting of sinus rhythm. In patients with atypical AVNRT, the mean AH interval was 69 msec ± 50 msec (± SD) longer during high right atrial pacing than during the tachycardia (P < 0.001). In 10 of 12 patients with atypical AVNRT, the AH interval during atrial pacing was more than 40 msec longer than the AH interval measured during the tachycardia. In contrast, in patients with ORT or atrial tachycardia, the differences in AH interval between atrial pacing and tachycardia were never more than 20 and 10 msec, respectively.
Conclusion : The difference in the AH interval between atrial pacing and the tachycardia allows a simple and rapid means of differentiating atypical AVNRT from other types of long RP tachycardias.     

Long R–P′ Paroxysmal Supraventricular Tachycardia: What Is the Mechanism?

Deciphering the electrophysiologic mechanism of a long R–P′ paroxysmal supraventricular tachycardia typically requires an invasive electrophysiologic study. We present a case where analysis of a simple surface 12‐lead ECG was sufficient for the diagnosis.     

Management of the Child with Wolff-Parkinson-White Syndrome and Supraventricular Tachycardia:

Management of the Child with WPW. In the next decade, "better" management will be defined by cost effectiveness including morbidity, mortality, and cost. We used a cost-effectiveness model for children with Wolff-Parkinson-White syndrome (WPW) and supraventricular tachycardia (SVT) comparing medical, surgical, and catheter ablative treatment between age 5 years (estimated average age at first recurrence after infancy) and age 21. Charges were quantitated from actual hospital bills; mortality was estimated from the literature; morbidity was assessed by estimating the number of hours in SVT, hours in clinic, hours in routine hospital bed, and hours in hospital intensive care; and the hours were then multiplied by a severity factor, normalized to 1.0 for 1 hour of SVT (0.5 for 1 hour in clinic, 0.75 for routine hospital, and 2.0 for intensive care). Overall charges (5 to 21 years old) for catheter ablation ($17,236) were 39% of surgical management and 57% of medical management; estimated mortality for catheter ablation (5 to 21 years old including failures that reverted to medical management) was 0.15%, which was 10% of medical management and 28% of surgical management; morbidity for catheter ablation was 27.6 units, which was 32% of medical management and 36% of surgical management. Sensitivity analysis demonstrated that the catheter ablation strategy remained preferable throughout the range of plausible values of cost, mortality, and morbidity (including a repeat procedure for initial failures). Therefore, catheter ablation has lower cost, mortality, and morbidity than either medical management or surgery and is the treatment of choice for the child 5 years of age or older with WPW and SVT. This type of analysis can be used for other forms of chronic disease in children.     

Dexmedetomidine: Therapeutic Use for the Termination of Reentrant Supraventricular Tachycardia

Objectives. 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. Design. Retrospective case series. Setting: Quaternary University Children's Hospital, Cardiac Intensive Care Unit. Patients: Patients who received dexmedetomidine for SVT in the past 5 years. Interventions: None. Outcome Measures: SVT episodes terminated with dexmedetomidine were compared with episodes terminated with adenosine. Results. 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). Conclusions. 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.     

国人室上性心动过速的性别特征及逆行P波对其折返径路的诊断价值

对９０例室上性心动过速（ＳＶＴ）患者的性别特征与逆行Ｐ波（Ｐ＇）分析结果发现：国人隐匿性房室旁道（ＣＡＰ）多于房室结双通道（ＤＡＶＮＰ），前者以男性为主，后者以女性为主；约２／３的旁道位于左游离壁（ＬＦＷ），１／３位于间隔及右游离壁，ＬＦＷ男性多见，间隔旁道女性多见；房室折返性心动过速Ｐ＇明显且Ｒ－Ｐ＇≥７０ｍｓ，房室结折返性心动过速多无Ｐ＇或Ｒ－Ｐ＇＜７０ｍｓ；Ｐ＇和Ｒ－Ｐ＇对ＡＶＲＴ和ＡＶＮＲＴ的手术前后诊断符合率为１００％。提示：心电图正常者，ＳＶＴ时Ｐ＇明显的男性，多为ＣＡＰ，且多在ＬＦＷ；ＳＶＴ时无Ｐ＇的女性，多为ＤＡＶＮＰ。     

Electrocardiographic Diagnosis of Atrial Tachycardia: Classification,P‐Wave Morphology,and Differential Diagnosis with Other Supraventricular Tachycardias

Atrial tachycardia is defined as a regular atrial activation from atrial areas with centrifugal spread, caused by enhanced automaticity, triggered activity or microreentry. New ECG classification differentiates between focal and macroreentrant atrial tachycardia. Macroreentrant atrial tachycardias include typical atrial flutter and other well characterized macroreentrant circuits in right and left atrium. Typical atrial flutter has been described as counterclockwise reentry within right atrial and it presents a characteristic ECG “sawtooth” pattern on the inferior leads. The foci responsible for focal atrial tachycardia do not occur randomly throughout the atria but tend to cluster at characteristic anatomical locations. The surface ECG is a very helpful tool in directing mapping to particular areas of interest. Atrial tachycardia should be differentiated from other supraventricular tachycardias. We propose a diagnostic algorithm in order to help the physician to discriminate among those. Holter analysis could offer further details to differentiate between atrial tachycardia and another supraventricular tachycardia. However, if the diagnosis is uncertain, it is possible to utilize vagal maneuvers or adenosine administration. In conclusion, in spite of well–known limits, a good interpretation of ECG is very important and it could help the physician to manage and to treat correctly patients with atrial tachycardia.     

Hyperventilation Facilitates Induction of Supraventricular Tachycardia: A Novel Method and the Possible Mechanism

INTRODUCTION: Hyperventilation has been demonstrated to alter autonomic function. Sympathomimetic drugs (isoproterenol) and parasympatholytic drugs (atropine) may be needed to facilitate induction of supraventricular tachycardia (SVT). The aim of this study was to test the clinical utility and mechanisms of hyperventilation to facilitate SVT initiation. METHODS AND RESULTS: Fourteen patients with clinically documented SVT (9 AV nodal reentrant tachycardia and 5 AV reciprocating tachycardia) but noninducible during baseline electrophysiologic study were included. Immediately after hyperventilation test (at least 30 respirations/min) for 2 minutes, systolic blood pressure, sinus cycle length, anterograde and retrograde 1:1 conduction, and induced SVT were measured. Arterial blood gas, pH, and heart rate variability before and after hyperventilation were measured. Seven of nine patients with AV nodal reentrant tachycardia and 3 of 5 patients with AV reciprocating tachycardia could be induced immediately after the hyperventilation test. After hyperventilation, anterograde AV and retrograde VA 1:1 conduction were improved, sinus cycle length was decreased, and heart rate variability were decreased in both groups. CONCLUSION: Hyperventilation can facilitate induction of SVT. Improvement of conduction properties and changes of autonomic function are the possible mechanisms.     

The Response of Paroxysmal Supraventricular Tachycardia to Overdrive Atrial and Ventricular Pacing:

Pacing During Supraventricular Tachycardia. Introduction: Standard electrophysiologic techniques generally allow discrimination among mechanisms of paroxysmal Supraventricular tachycardia. The purpose of this study was to determine whether the response of paroxysmal Supraventricular tachycardia to atrial and ventricular overdrive pacing can help determine the tachycardia mechanism. Methods and Results: Fifty-three patients with paroxysmal Supraventricular tachycardia were studied. Twenty-two patients had the typical form of atrioventricular (AV) junctional (nodal) reentry, 18 patients had orthodromic AV reentrant tachycardia, 10 patients had atrial tachycardia, and 3 patients had the atypical form of AV nodal reentrant tachycardia. After paroxysmal Supraventricular tachycardia was induced, 15-beat trains were introduced in the high right atrium and right ventricular apex sequentially with cycle lengths beginning 10 msec shorter than the spontaneous tachycardia cycle length. The pacing cycle length was shortened in successive trains until a cycle of 200 msec was reached or until tachycardia was terminated. Several responses of paroxysmal Supraventricular tachycardia to overdrive pacing were useful in distinguishing atrial tachycardia from other mechanisms of paroxysmal Supraventricular tachycardia. During decremental atrial overdrive pacing, the curve relating the pacing cycle length to the VA interval on the first beat following the cessation of atrial pacing was flat or upsloping in patients with AV junctional reentry or AV reentrant tachycardia, but variable in patients with atrial tachycardia. AV reentry and AV junctional reentry could always be terminated by overdrive ventricular pacing whereas atrial tachycardia was terminated in only one of ten patients (P < 0.001). The curve relting the ventricular pacing cycle length to the VA interval on the first postpacing beat was flat or upsloping in patients with AV junctional reentry and AV reentry, but variable in patients with atrial tachycardia. The typical form of AV junctional reentry could occasionally be distinguished from other forms of paroxysmal Supraventricular tachycardia by the shortening of the AH interval following tachycardia termination during constant rate atrial pacing. Conclusions: Atrial and ventricular overdrive pacing can rapidly and reliably distinguish atrial tachycardia from other mechanisms of paroxysmal Supraventricular tachycardia and occasionally assist in the diagnosis of other tachycardia mechanisms. In particular, the ability to exclude atrial tachycardia as a potential mechanism for paroxysmal Supraventricular tachycardia has important implications for the use of catheter ablation techniques to cure paroxysmal Supraventricular tachycardia.     

射频导管消融慢径路治疗程控刺激不能诱发且无明显跳跃的房室结折返性心动过速疗效分析

目的观察无A—H间期跳跃和不能诱发的房室结折返性心动过速（AVNRT）慢径路消融特点和远期疗效。方法经电生理检查证实无旁道参与的阵发性室上性心动过速患者100例,分成三组：能诱发AVNRT,有明显跳跃（A组,n=40）;不能诱发AVNRT,但有A—H间期〉50ms的明显跳跃（B组,1=40）;不能诱发AVNRT且没有A—H间期〉50ms的明显跳跃（C组．n=20）。比较术后各组电生理数值及消融远期疗效。结果与消融术前相比．术后各组患者的房室结顺传文氏周期均延长（P〈0．05）;消融术后房室结顺传有效不应期较术前缩短,差异有统计学意义（P〈0．05）;三组均出现缓慢交接区心律。术后随访12个月．各组复发率差异无统计学意义（P〉0．05）。结论无A—H间期跳跃且程控刺激不能诱发的AVNRT的慢径路消融是安全有效的。缓慢交接区心律是消融有效的标志。     

Postextrasystolic U Wave Augmentation, a New Marker of Increased Arrhythmic Risk in Patients Without the Long QT Syndrome

Objectives. We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias.

Background. Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the “pause-dependent long QT syndrome.” However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown.

Methods. We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after a PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group).

Results. Postextrasystolic T wave changes did not correlate with a history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, a low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias.

Conclusions. Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.

(J Am Coll Cardiol 1996;28:1746–52)>     

Surgical Division of Right and Left Free Wall Accessory Atrioventricular Electrical Connections in a Child with Incessant Supraventricular Tachycardia

Abstract: Surgical division of right and left free wall accessory atrioventricular electrical connections in a child with incessant supraventricular tachycardia. D. Richards, A. Denniss, P. Russell, D. Johnson, N. Buchanan, C. Whight, A. Chong and J. Uther, Aust. N.Z. J. Med., 1982, 12 , pp. 52–55.
A child with Wolff-Parkinson-White syndrome developed incessant supraventricular tachycardia refractory to medical therapy and countershocks. Supraventricular tachycardias incorporating both right and left free wall accessory atrioventricular electrical connections were demonstrated. The more frequent, broad complex tachycardia utilised both the accessory connections and was independent of the atrioventricular node. The less frequent, narrow complex tachycardia utilised the atrioventricular node for anterograde conduction and the left sided accessory connection for retrograde conduction. Surgical division of the accessory connections restored normal sinus rhythm and eliminated supraventricular tachycardia.