Part II-Clinical presentation, electrophysiologic characteristics, and when and how to ablate atriofascicular pathways and long and short decrementally conducting accessory pathways.

Recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, frequently difficult, challenge for the clinical cardiac arrhythmologist. In this second part of our series of reviews relative to this topic, we discuss the steps required to achieve the correct diagnosis and appropriate management in patients with the so-called "Mahaim" variants of pre-excitation. We indicate that, nowadays, it is recognized that these abnormal rhythms are manifest because of the presence of atriofascicular pathways. These anatomical substrates, however, need to be distinguished from the other long and short accessory pathways which produce decremental atrioventricular conduction. The atriofascicular pathways, along with the long decrementally conducting pathways, have their atrial components located within the vestibule of the tricuspid valve. The short decremental pathways, in contrast, can originate in the vestibules of either the mitral or tricuspid valves. As a starting point, careful analysis of the 12-lead electrocardiogram, taken during both sinus rhythm and tachycardias, should precede any investigation in the catheterization room. When assessing the patient in the electrophysiological laboratory, the use of programmed electrical stimulation from different intracardiac locations, combined with entrainment technique and activation mapping, should permit the establishment of the properties of the accessory pathways, and localization of its proximal and distal ends. This should provide the answer to the question "is the pathway incorporated into the circuit underlying the clinical tachycardia". That information is essential for decision-making with regard to need, and localization of the proper site, for catheter ablation.

Unusual variants of pre-excitation: From anatomy to ablation: Part III-Clinical presentation, electrophysiologic characteristics, when and how to ablate nodoventricular, nodofascicular, fasciculoventricular pathways, along with considerations of permanent junctional reciprocating tachycardia.

The recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, but frequently a difficult, challenge for the clinical cardiac arrhythmologist. In this third part of our series of reviews, we discuss the different steps required to come to the correct diagnosis and management decision in patients with nodofascicular, nodoventricular, and fasciculo-ventricular pathways. We also discuss the concealed accessory atrioventricular pathways with the properties of decremental retrograde conduction that are associated with the so-called permanent form of junctional reciprocating tachycardia. Careful analysis of the 12-lead electrocardiogram during sinus rhythm and tachycardias should always precede the investigation in the catheterization room. When using programmed electrical stimulation of the heart from different intracardiac locations, combined with activation mapping, it should be possible to localize both the proximal and distal ends of the accessory connections. This, in turn, should then permit the determination of their electrophysiologic properties, providing the answer to the question "are they incorporated in a tachycardia circuit?". It is this information that is essential for decision-making with regard to the need for catheter ablation, and if necessary, its appropriate site.

An unusual ectopic ventricular rhythm in a young woman.

A case of a 22-year-old young pregnant woman with palpitations and near syncope is presented. Holter monitoring showed very frequent premature beats and runs of wide complex tachycardia, refractory to antiarrhythmic drugs. Electrophysiologic evaluation disclosed spontaneous automatism arising in an atriofascicular pathway. Differential diagnosis is discussed.

Reappraisal and new observations on atrial tachycardia ablated from the non-coronary aortic sinus of Valsalva.

Aims: The clinical characteristics of atrial tachycardias (AT) ablated from the non-coronary aortic sinus (NCS) are thus far described only in small series. We aimed to outline, in a large cohort of patients, the clinical, electrocardiographic, electrophysiological characteristics of this tachycardia. Methods and results: We analysed data pertaining to clinical, electrocardiographic, and electrophysiological characteristics of 43 consecutive patients from an overall cohort of 441 with AT who were successfully ablated from the NCS. The tachycardias ablated from the NCS were paroxysmal (98%) and adenosine sensitive (35/35). The patients were aged 54.6 ± 12.4 years, showing female preponderance (74%). No P wave pattern was predictive of the location of ablation. Electrophysiological findings suggested a possible micro-reentrant mechanism. During tachycardia, atrial electrograms recorded in the NCS preceded the A in the His region by 10.9 ± 7.4 ms. Fractionated atrial electrograms were noted at the site of ablation in 42 patients during the tachycardia. Radiofrequency ablation terminated the tachycardia within 5 s in 88%, with thermal automaticity seen only in 3 patients. The site of ablation at the base of the NCS was adjacent to the presumed site of the retroaortic node, a remnant of the initial atrio-ventricular canal musculature. Conclusions: AT ablated from the NCS is a paroxysmal arrhythmia in middle-aged women, with distinct electrocardiographic and electrophysiological characteristics. We suspect the retroaortic node to be involved in the tachycardia circuit.

Clinical, electrocardiographic, and electrophysiologic characteristics of patients with a fasciculoventricular pathway: the role of PRKAG2 mutation.

BACKGROUND: The ECG, clinical, and electrophysiologic profiles of patients with a fasciculoventricular pathway are well described. Fasciculoventricular pathways occurring in the setting of glycogen storage cardiomyopathy possess unique features. OBJECTIVE: The purpose of this study was to compare the clinical, ECG, and electrophysiologic characteristics of patients with a fasciculoventricular pathway, with or without glycogen storage cardiomyopathy. METHODS: Two groups of patients with a fasciculoventricular pathway were compared: group A consisted of 10 patients with the PRKAG2 mutation (Arg302gln), and group B consisted of 9 patients without the mutation. RESULTS: Thirty percent of group A patients had left ventricular hypertrophy, and none had an additional accessory pathway. Group B patients had no structural heart disease, and 33% had an additional accessory pathway. Group A patients had a slower resting heart rate (56 ± 7 vs 75 ± 10 bpm, P <0.0001), a wider QRS complex (0.15 ± 0.01 vs 0.11 ± 0.02 ms, P = .0004), and a longer HV interval (34 ± 1 vs 25 ± 3 ms, P = .0003). During long-term follow-up, 50% of group A patients developed complete AV block versus none in group B. Eighty percent of group A patients developed atrial flutter and/or atrial fibrillation. No Group B patient had any arrhythmia during follow-up after successful ablation of additional arrhythmia circuits. No sustained ventricular arrhythmia was induced in any patient from either group. CONCLUSION: Patients with a fasciculoventricular pathway associated with the PRKAG2 mutation have distinct clinical, ECG, and electrophysiologic profiles and should be correctly identified because of their ominous long-term prognosis. Patients without the mutation have an excellent arrhythmia-free prognosis after treatment of additional circuits.

Long term outcome of cavotricuspid isthmus cryoablation for the treatment of common atrial flutter in 180 patients: a single center experience.

OBJECTIVE: Recent literature has shown that common type atrial flutter (AFL) can recur late after cavotricuspid isthmus (CTI) catheter ablation using radiofrequency energy (RF). We report the long term outcome of a large group of patients undergoing CTI ablation using cryothermy for AFL in a single center. METHODS: Patients with AFL referred for CTI ablation were recruited prospectively from July 2001 to July 2006. Cryoablation was performed using a deflectable, 10.5 F, 6.5 mm tip catheter. CTI block was reassessed 30 min after the last application during isoproterenol infusion. Recurrences were evaluated by 12-lead ECG and 24 h Holter recording every clinic visit (1/3/6/9 and 12 months after the procedure and yearly thereafter) or if symptoms developed. RESULTS: The 180 enrolled patients had the following characteristics: 39 women (22%), mean age 58 years, no structural heart disease in 86 patients (48%), mean left atrium diameter 44+/-7 mm and mean left ventricular ejection fraction 57+/-7%. The average number of applications per patient was 7 (3 to 20) with a mean temperature and duration of -88 degrees C and 3 min, respectively. Acute success was achieved in 95% (171) of the patients. There were no complications. After a mean follow-up of 27+/-17 (from 12 to 60) months, the chronic success rate was 91%. The majority of the recurrences occurred within the first year post ablation. One hundred and twenty three patients had a history of atrial fibrillation (AF) prior to CTI ablation and 85 (69%) of those remained having AF after cryoablation. In 20 of 57 (35%) patients without a history of AF prior to CTI ablation, AF occurred during follow-up. CONCLUSIONS: This prospective study showed a 91% chronic success rate (range 12 to 60 months) for cryoablation of the CTI in patients with common type AFL and ratified the frequent association of AF with AFL.

Electrocardiogram in patients with fasciculoventricular pathways: a comparative study with anteroseptal and midseptal accessory pathways.

OBJECTIVES: The purpose of this study was to describe the ECG profile of a cohort of patients with fasciculoventricular pathways and compare the profile with the ECG of patients with anteroseptal and midseptal accessory pathways. BACKGROUND: Electrophysiologic findings suggest fasciculoventricular pathways insert into the septal region. Findings also suggest the 12-lead surface ECG during sinus rhythm is similar to the ECG of patients with anteroseptal and midseptal bypass tracts. METHODS: Four different observers analyzed the 12-lead ECG of seven patients with fasciculoventricular pathways (group I) and the ECG of 20 patients with midseptal AV accessory pathways (group II) and 20 patients with anteroseptal AV accessory pathways (group III). The following variables were analyzed: ECG frontal plane QRS and delta wave axis; angle between the QRS and the delta wave axis; QRS width; R/S ratio in lead III; presence of a negative delta wave in inferior leads; and precordial lead transition to R/S >1. RESULTS: The ECG of fasciculoventricular pathways shows a variable pattern. It shares some features with an anteroseptal accessory pathway and others with a midseptal accessory pathway. A narrower QRS width was the most important variable in distinguishing a fasciculoventricular pathway from a septally located AV bypass tract (P <.0001). The angle between the QRS and the delta wave frontal plane axis could differentiate a fasciculoventricular pathway from an anteroseptal bypass tract (P <.0001) but not from a midseptal accessory pathway. CONCLUSIONS: The sinus rhythm ECG of patients with fasciculoventricular pathways shows similarities with ECGs of patients with anteroseptal and midseptal accessory pathways, but the QRS complex usually is narrower. The ECG recorded during sinus rhythm cannot reliably differentiate fasciculoventricular pathways with a broad QRS complex from anteroseptal or midseptal bypass tracts.

25 years of insights into the mechanisms of supraventricular arrhythmias.

The introduction of programmed electrical stimulation of the heart and intracardiac activation mapping 35 years ago made it possible to study the site of origin or pathway of a supraventricular tachycardia and to gain insight into the tachycardic mechanism. Information from these studies has been the basis for the development of new therapies, like arrhythmia surgery, antitachycardia pacing, and catheter ablation. The correlation of intracardiac findings with the 12-lead ECG during the tachycardia resulted in the recognition of characteristic ECG patterns for the different types of supraventricular tachycardias. Currently, gross localization of the site of origin of the arrhythmia is based on the 12-lead ECG during the arrhythmia with fine tuning using intracardiac activation mapping and pacing. These developments during the past 3 decades make accurate arrhythmia diagnosis possible and allow us to offer curative therapies to many of patients suffering from a supraventricular tachycardia.

Electrocardiogram during tachycardia in patients with anterograde conduction over a Mahaim fiber: old criteria revisited.

OBJECTIVES: The aim of this study was to prospectively evaluate the sensitivity, specificity, and positive and negative predictive values of previously described ECG criteria to identify preexcited tachycardia due to decrementally conducting accessory pathways (QRS axis between 0 and -75 degrees , QRS width < or = 0.15 seconds, an R wave in lead I, an rS pattern in lead V(1), RS > 1 QRS transition > V(4), and cycle length between 220 and 450 ms). BACKGROUND: Preexcited tachycardia associated with decrementally conducting right-sided accessory pathways usually shows a rather "narrow" QRS complex and can be difficult to differentiate from supraventricular tachycardia (SVT) with left bundle branch block (LBBB) aberrant conduction. METHODS: We analyzed three groups of patients: 32 patients with an atriofascicular pathway (group I); 8 patients with long (n = 3) or short (n = 5) decrementally conducting right-sided AV pathway (group II); and a control group that consisted of 35 patients with SVT and LBBB (group III). RESULTS: Presence of all six criteria had 87.5% sensitivity in group I and a 0% sensitivity in group II. There were four false negatives in group I. The negative predictive value was 82.5%, with six false positives in group III (five patients with an aberrant LBBB-shaped tachycardia with ventriculoatrial conduction over an accessory AV pathway). The criterion cycle length was not helpful. CONCLUSIONS: Criteria for identifying a tachycardia with anterograde conduction over a Mahaim fiber are helpful only in atriofascicular pathways, with a sensitivity of 87.5% and a negative predictive value of 82.5%. The major cause of false positives was a tachycardia with aberrant LBBB conduction and ventriculoatrial conduction over an accessory AV pathway.

Mahaim fiber: an atriofascicular or a long atrioventricular pathway?

There is debate concerning the distal insertion of Mahaim fibers. Some findings favor an atriofascicular fiber connected with the distal right bundle branch. Other findings favor a long atrioventricular (AV) structure inserting into the myocardium. A patient having a decrementally conducting accessory pathway is reported. Proximal and distal Mahaim potentials were recorded during sinus rhythm, atrial pacing, and antidromic tachycardia. Both proximal and distal M potentials always preceded the QRS complex during sinus rhythm and antidromic tachycardia earlier than the right bundle branch potential. During tachycardia, the distal M potential was recorded 6 ms before the retrograde right bundle potential. Other arguments consistent with an AV connection were a change in the QRS configuration during tachycardia after the first radiofrequency pulse at the site of the distal M potential and absence of right bundle branch block after successful ablation. Conduction through the proximal part of the Mahaim fiber was unaltered after ablation, as assessed by recording the proximal M potential. Electrophysiologic evidence is presented suggesting a long AV accessory pathway inserting close to the distal right bundle branch rather than an atriofascicular connection in this patient with a Mahaim fiber.

Idiopathic left bundle-branch block-shaped ventricular tachycardia may originate above the pulmonary valve.

BACKGROUND: Idiopathic left bundle-branch block (LBBB)-like ventricular tachycardia (VT) is considered to originate in the right ventricular outflow tract (RVOT) or from the aortic root. Both regions are derived from the embryonic outflow tract. We now report that also the pulmonary trunk can give rise to VT, suggesting a common etiology of these tachycardias. METHODS AND RESULTS: We studied 6 patients with symptomatic idiopathic LBBB-VT using electrophysiological mapping techniques. The VT origin was determined by analyzing the electrograms and the angiographic location of the catheter tip at the successful ablation site or the earliest activation site. Eight VTs were induced. Two VTs, with a mean earliest endocardial activation time of -5 and -20 ms and optimal pace mapping, were successfully ablated in the RVOT. In the remaining 6 VTs, the earliest activation site was found in the pulmonary artery, and, at this site, a sharp potential was present -38+/-12 ms before the QRS in 5 VTs. The mean earliest endocardial activation time in the RVOT was -1+/-2 ms. Ablation was attempted in 5 of 6 VTs and resulted in an acutely successful procedure. After a mean follow-up of 10+/-4 months, 1 of 5 patients had a recurrence. CONCLUSIONS: The site of origin of idiopathic LBBB-VT can be in the root of the pulmonary artery, suggesting a myocardial connection from this site to the RVOT. If no good criteria for ablation in the RVOT are found, detailed mapping of the pulmonary artery should be performed.