Novel analysis of ventriculoatrial interval prolongation during a narrow QRS tachycardia using a right atrial nondecremental-midseptal accessory pathway

Figures

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  Figure 1. A supraventricular reentrant tachycardia (SVT). A: Electrocardiogram (ECG). Arrowheads indicate negative P waves in inferior leads. B: Intracardiac recordings. A, H, and V indicate atrial, His bundle, and ventricular depolarizations, respectively. Tracings from top to bottom indicate surface ECG leads I, II, V1, V4, and intracardiac electrograms of high right atrium (HRA, p and d; proximal and distal electrode pair), His bundle (HB, proximal 9-10 and distal 1-2), coronary sinus (CS), and right ventricle (RV). A tachycardia has a cycle length of 240 ms (atrio-His [AH] 130 ms and His-atrial [HA] interval 110 ms) and a retrograde concentric atrial activation sequence. Order of ECG leads and intracardiac recordings and abbreviations are also the same as below figures. C: Initiation by RV apex constant pacing with a cycle length of 600 ms in sinus rhythm. ABLd and p indicate distal and proximal electrode pair of an ablation catheter, respectively; CSos indicates the ostium of the coronary sinus. After 3 RV stimuli (Sts) from the left conduct to atrial myocardium (marked by asterisks) over an accessory pathway retrogradely and afterward 4 atrial depolarizations appeared, an SVT with a…

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  Figure 2. Termination of tachycardia. A: A premature stimulus (St) at the right ventricular apex (RV) delivered immediately after registration of antegradely depolarized His bundle (H; arrow) can terminate tachycardia due to ventriculoatrial block (VAB). B: RV overdrive pacing with a cycle length of 230 ms. A1/A2 and V1/V2 indicate atrial and ventricular depolarizations during tachycardia before (1)/after (2) the first St (arrow) from the left, respectively. A3 indicates an atrial depolarization owing to the second St. A1-A2 interval (235 ms) is shortened without change of V1-V2 (and H-H) interval (255 ms). Also, the second reduces a VA interval and succeedingly the third can result in VAB. C: Ablation fluoroscopic images. ABL = radiofrequency ablation; CS = coronary sinus; HB = His bundle; HRA = high right atrium; LAO = left anterior oblique view; RAO = right anterior oblique view; RV = right ventricular apex catheter. D: Ablation energy application. ABLd indicates distal electrode pair of ablation catheter. Asterisks indicate putative accessory pathway potentials. Vertical line indicates commencement of radiofrequency catheter ablation (RF). Tachycardia terminates instantaneously by RF.

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  Figure 3. Comparison of ventriculoatrial (VA) intervals. A: A nonsustained orthodromic atrioventricular reentrant tachycardia (AVRT) with a cycle length of 320 ms. An AVRT was induced by constant pacing with a cycle length of 330 ms (St-St) from the proximal electrode pair of coronary sinus (CS9,10). A VA interval during AVRT was 180 ms, measured as an interval from the onset of QRS to the positive peak of the atrial potential on high right atrium (HRA) (shown by an arrow). St = stimulus artefact; VAB = ventriculoatrial block. B: Right ventricular apex (RV) pacing with a cycle length of 330 ms in sinus rhythm. A VA interval during RV constant pacing with a cycle length of 330 ms was 160 ms. RV pacing with the shorter cycle length resulted in 2:1 VAB. C: Ladder diagrams during AVRT and RV pacing. AP = accessory pathway; AVN = atrioventricular node; HB = His bundle; LV-IVS = interventricular septum of left ventricle; RA-IASm = mid-interatrial septum of right atrium; RV-IVS = interventricular septum of right ventricle. Solid lines indicate VA intervals during AVRT and RV pacing. Solid and broken arrows indicate antegrade and retrograde activation conduction sequences, respectively. Asterisk…