Atrial dissociation: an electrophysiologic finding in a patient with transposition of the great arteries.

Complete interatrial block with two independent atrial rhythms is demonstrated by intracardiac electrograms in a patient with transposition of the great arteries who had undergone a Mustard operation. The atrial conduction abnormalities produced by the Mustard procedure with subsequent baffle revision are related to damaged anatomic interatrial connections and are similar to conduction abnormalities produced in experimental models of interatrial block.

Mechanisms and relevance of arrhythmias induced by high-current programmed ventricular stimulation.

Programmed ventricular stimulation was performed at 10 mA with up to 3 extrastimuli in 15 patients studied for indications other than sustained ventricular tachycardia and with no sustained arrhythmias induced at twice diastolic threshold. Stimulation with 10 mA produced 6 new instances of ventricular fibrillation (VF), 1 of which may have been clinically relevant. No sustained ventricular tachycardia was induced. VF was induced with triple extrastimuli in 5 of 6 cases. The increased arrhythmogenicity of 10-mA stimulation was related to shortened ventricular refractory periods (S2 267 +/- 21 vs 231 +/- 22 ms, p less than 0.0001; S3 217 +/- 15 vs 178 +/- 15 ms, p less than 0.0005) and did not occur without at least 2 extrastimulus coupling intervals being less than was possible at twice diastolic threshold. Stimulation with 10 mA also resulted in greater increments in extrastimulus local conduction time (27 +/- 19 vs 54 +/- 15 ms, p less than 0.001) and intraventricular conduction time (27 +/- 17 vs 45 +/- 18 ms, p less than 0.005) as coupling intervals were shortened from 360 ms to just beyond ventricular refractoriness. VF was induced more frequently in patients with cardiomyopathy (p less than 0.05). Thus, the increase in arrhythmogenicity with 10-mA stimulation with triple extrastimuli is predominantly manifest as VF, which occurs with considerable frequency and is of uncertain clinical significance. This technique should be used with great caution, and only after other stimulation modalities have been attempted.

Radiofrequency catheter ablation of ventricular tachycardia in right ventricular cardiomyopathy: use of concealed entrainment to identify the slow conduction isthmus bounded by an aneurysm and the tricuspid annulus.

Radiofrequency (RF) catheter ablation of ventricular tachycardia (VT) in patients with a right ventricular (RV) cardiomyopathy has only rarely been successful. This report demonstrates reentrant VT in the setting of RV cardiomyopathy in which the tricuspid valve annulus acted as one of the barriers of an isthmus of slow conduction, identified by the presence of entrainment with concealed fusion. The RF pulse was further targeted by analysis of the relationship between the postpacing interval with the tachycardia cycle length, and of the local activation time with the stimulation time. Long-term clinical follow-up has documented no recurrent VT.

Sinus node modification using radiofrequency current in a patient with persistent inappropriate sinus tachycardia.

Radiofrequency catheter modification of the sinus node for persistent inappropriate sinus tachycardia has not been previously reported. This article describes a patient in whom radiofrequency current was used to ablate an incessant automatic tachycardia focus mapped to the region of the sinus node, where a discrete multicomponent electrogram demonstrating earliest atrial activation was recorded. A transient junctional rhythm developed immediately after ablation, with rapid subsequent emergence of a stable rhythm having normal sinus nodal characteristics.

Ventricular tachycardia induction: comparison of triple extrastimuli with an abrupt change in ventricular drive cycle length.

This study compares two stimulation protocols in 47 patients not inducible with double extrastimuli administered during two paced cycle lengths at the right ventricular apex. Method I uses triple extrastimuli; method II, an abrupt short-to-long change in cycle length, single and double extrastimuli. Clinical arrhythmias included sustained ventricular tachycardia or fibrillation (11 patients; group I); nonsustained ventricular tachycardia (27; group II); and no documented ventricular arrhythmia (9; group III). Together, methods I and II rendered 21 of 47 patients inducible; seven were inducible by both methods. No group III patient became inducible. The two techniques were equally likely to produce tachycardias in groups I and II; to induce rapid, pleomorphic, or sustained tachycardias, and tachycardias greater than 10 beats. Since both methods can be applied at the right ventricular apex and increase sensitivity without producing tachycardia in patients with a low suspicion for ventricular arrhythmias, they may facilitate serial drug testing with an indwelling catheter, reducing the need for left-sided studies.

Ablation of 'incisional' reentrant atrial tachycardia complicating surgery for congenital heart disease. Use of entrainment to define a critical isthmus of conduction.

BACKGROUND: Intra-atrial reentrant tachycardia occurs frequently after surgery for congenital heart disease and is difficult to treat. We tested the hypotheses that intra-atrial reentrant tachycardia in patients who had undergone prior reparative surgery for congenital heart disease could be successfully ablated by targeting a protected isthmus of conduction bounded by natural and surgically created barriers and that entrainment techniques could be used to identify these zones. METHODS AND RESULTS: Eighteen consecutive patients with 26 intra-atrial reentrant tachycardias complicating surgery for congenital heart disease (9 atrial septal defect repair, 4 Fontan, 2 Mustard, 2 Senning, and 1 Rastelli procedure) underwent electrophysiological study and ablation attempts. Mapping of activation was facilitated by the deployment of catheters with multiple electrodes. Sites for ablation were sought that demonstrated entrainment with concealed fusion and at which the postpacing interval minus the tachycardia cycle length and the stimulus to P wave minus the activation time were < 30 ms. These sites were considered to be within a narrow isthmus critical to the tachycardia mechanism. Anatomic barriers bordering the critical isthmus of conduction were identified on anatomic grounds, by the presence of areas of electrical silence or by the demonstration of split potentials signifying a line of block. Success was achieved in 15 patients with 21 arrhythmias. The median number of radiofrequency applications was 5. There was a wide range of activation times at successful sites (-30 to -250 ms). At a mean duration of follow-up of 17 +/- 8 months, 11 patients were asymptomatic and 9 did not require antiarrhythmia therapy. CONCLUSIONS: Successful ablation of intra-atrial reentrant tachycardia complicating surgery for congenital heart disease may be achieved by creation of an ablative lesion in a critical isthmus of conduction bounded by anatomic barriers. This isthmus may be identified by the presence of entrainment with concealed fusion and an analysis of the relationship between the postpacing interval and the tachycardia cycle length and between the activation time and the stimulus time. Because this isthmus is invariably confined on at least one aspect by a surgical repair site that is of central importance to the tachycardia mechanism, we suggest that this type of arrhythmia be given the descriptive designation of "incisional reentry."