Successful Catheter Ablation for Paroxysmal Supraventricular Tachycardia with Two Alternating Cycle Lengths.

A 62-year-old male was transferred to our hospital complaining of palpitations. His heart rate was 185/min. Electrocardiogram showed a narrow QRS regular tachycardia and the tachycardia changed spontaneously to another narrow QRS tachycardia with two alternating cycle lengths. The arrhythmia was stopped by the administration of adenosine triphosphate. Findings from electrophysiological study suggested that there was an accessory pathway (AP) and dual atrioventricular (AV) nodal pathways. After AP ablation, any other tachyarrythmias were not induced. We supposed that the tachycardia was paroxysmal supraventricular tachycardia involving AP and anterograde conduction alternating between slow and fast AV nodal pathways.

A-V-V-A response to single atrial premature depolarization in a narrow QRS tachycardia: What is the mechanism?

We present an atypical response to single atrial premature depolarization (APD) in a long RP' tachycardia. APD advanced the His-bundle potential immediately after it and resulted in a VA block; however, tachycardia persisted and consequently exhibited an A-V-V-A response. We propose the mechanism for an A-V-V-A response to APD in a long RP' tachycardia.

Narrow QRS Tachycardia: What Is the Mechanism?

A 45-year-old man was referred for radiofrequency catheter ablation of narrow QRS tachycardia that terminated with intravenous adenosine. A 12-lead electrocardiogram showed no baseline pre-excitation. The echocardiogram was essentially normal. The electrophysiological study showed a normal atrial-His interval of 110 ms and a His-ventricular interval of 44 ms during sinus rhythm. An anterograde study demonstrated no dual atrioventricular nodal physiology. Atrial pacing protocols easily and reproducibly induced a narrow QRS tachycardia. What is the mechanism of the tachycardia?

Discordant responses to his refractory premature ventricular beats (PVBs) during a regular narrow QRS tachycardia. What is the mechanism.

A 32-year-old lady was evaluated for recurrent episodes of palpitation. During one of the palpitation episodes a regular narrow QRS tachycardia was documented, and it got terminated with the administration of IV adenosine. The baseline 12 lead electrocardiogram (ECG) did not show any manifest preexcitation. There was no evidence of structural heart disease by echocardiogram. Patient underwent an electrophysiology (EP) study after informed consent. Quadripolar catheters were placed at the His region and right ventricular (RV) apex. A decapolar catheter was placed in the coronary sinus (CS) with CS 9, 10 dipoles at CS OS region and CS 1, 2 dipoles at CS distal region. A mapping & ablation catheter was positioned at right atrial (RA) appendage. Baseline atrial and ventricular pacing protocols could not be performed as both atrial and ventricular pacing were easily inducing a regular narrow QRS tachycardia. His refractory premature ventricular beats [PVBs] were delivered from RVRV apex and left ventricular [LV] free wall. Discordant responses were obtained. What is the mechanism?

Regular narrow QRS tachycardia. What is the mechanism?

A 45-years-old lady with no structural heart disease on echocardiogram presented with recurrent episodes of palpitation. There was no baseline preexcitation. Twelve lead surface electrocardiograms (ECG) recorded during one of the episodes are provided. What is the likely mechanism of the tachycardia? [Figure: see text].

A rare case of narrow QRS tachycardia with "hidden" concealed left-sided accessory pathway.

A 54-year-old-woman with narrow QRS tachycardia (heart rate, 210 beats per minute) was admitted to the authors' hospital. Tachycardia terminated after administration of adenosine. The 12-lead electrocardiogram after conversion to sinus rhythm was unremarkable. During electrophysiological study, tachycardia could be easily induced by programmed atrial stimulation without jump phenomenon. The cycle length was 260 ms. During tachycardia, the atrial activation sequence in the coronary sinus (CS) was distal-to-proximal. However, during decremental ventricular pacing, retrograde conduction showed exclusively proximal-to-distal activation in the CS. What is the underlying mechanism?

Interesting response to ventricular overdrive pacing during regular narrow QRS tachycardia. What is the mechanism?

33 year old gentleman has undergone an electrophysiology study for recurrent paroxysmal palpitation. During one of the episodes of palpitation a regular narrow QRS tachycardia was documented which has terminated with intravenous adenosine. Baseline electrocardiogram did not show any pre-excitation. Atrial-His (AH) and His-Ventricular (HV) intervals were normal at baseline. There was no evidence of dual atrioventricular (AV) nodal physiology. Earliest atrial electrogram during ventricular pacing was recorded at coronary sinus (CS) 9,10 dipoles placed at CS OS region. Narrow QRS tachycardia with cycle length (TCL) of 400 ms and earliest retrograde atrial activation at CS 9,10 dipoles was induced with programmed ventricular stimulation. Ventricular overdrive (VOD) pacing was performed at 30 ms shorter than TCL during the tachycardia (Fig: 1). What is the mechanism of tachycardia?