Disturbances in atrial rhythm and conduction following the surgical creation of an atrial septal defect by the Blalock-Hanlon technique

Research accomplishments in pediatric electrophysiology: a historical review

Arrhythmia management in young patients plays a small but important role within the broader discipline of cardiac electrophysiology (EP). By virtue of its sharp focus on developmental cardiology, congenital heart defects, and hereditary channelopathies, pediatric EP has contributed in significant ways to improved understanding of rhythm disorders in patients of all ages. Scientific progress in the field was recently reviewed at the 2012 meeting of the Heart Rhythm Society, where historical details of pioneering investigations in pediatric EP were highlighted. In this article, we hope to summarize those details and acknowledge the roles of individuals and organizations that were instrumental in developing the subspecialty.

Prevention of unbalanced lung perfusion and atrial arrhythmias after the lateral tunnel operation

BACKGROUND

The lateral tunnel operation has become increasingly popular with pediatric cardiac surgeons, as it is technically reproducible, is relatively easy to perform, and can be used in a variety of patients with single-ventricle physiology. The main drawbacks of the original operation are uneven blood flow distribution to the lungs and increasing incidence of supraventricular arrhythmias over time.

METHODS

In 1988, we modified this technique by avoiding narrowing of the tunnel at the superior vena cava-atrial junction, avoiding incorporation of the crista terminalis in the baffle suture line, and minimizing damage to the sinoatrial node. Between 1988 and 1995, 19 patients underwent this operation at Marie-Lannelongue Hospital in Paris.

RESULTS

There was one early death and no late deaths. At a mean follow-up of 5.2 years, all survivors are in New York Heart Association class I. Early atrial flutter, related to atrial scarring secondary to multiple previous surgical procedures, developed in 1 patient, and late atrial flutter developed in 1 patient who had a previous Blalock-Hanlon atrial septectomy. All patients are currently in sinus rhythm. Atrial flutter did not occur in 17 patients who had had no previous atrial wall surgical procedure.

CONCLUSIONS

We believe that the good long-term clinical results are directly attributable to our modifications, which ensure optimal hemodynamics and absence of rhythm disturbances. All patients who had not previously undergone operation on the atrial wall were free from supraventricular tachyarrhythmias at a mean follow-up of 5.2 years. This is a consequence of protecting the sinus node, crista terminalis, and Bachmann's bundle.

Electrophysiologic study of dysrhythmias after atrial operations in dogs

Experiments were conducted with 159 dogs to investigate the mechanism of persistent dysrhythmias clinically encountered after atrial-level operations. Those found after incisions to the internodal pathways (INPs) of the right atrium were analyzed using cardiac mapping in an anesthetized or extracorporeally perfused state. Longitudinal incisions of the posterior INP often allowed inducible sustained atrial flutter, with circus movement of excitation around the right atrium near the tricuspid orfice. Sustained atrial flutter thus produced was modified in cycle length by coexisting division of the middle INP but inhibited by that of the anterior INP. Its incidence increased at chronic stage, with marked cicatricial changes. The disrupted anterior INP markedly prolonged conduction time to the atrioventricular node and A-H interval compared with the other disruptions. Persistent atrioventricular junctional rhythm developed in about 50% of the animals after disruption of all three INPs or anterior and posterior INPs; division of the anterior INP was the common potent factor, although no single blocked INP produced persistent junctional rhythm. Our results support the "summation theory." The incidence of junctional rhythm and hypoxia of the sinoatrial node (flow rate of less than 10 mL.100 g-1.min-1) were markedly enhanced by coexisting blockade of atrial feeding arteries in addition to division of the anterior INP. In conclusion, massive posterior INP disruption is a potent anatomic substrate in producing sustained atrial flutter, middle INP division a modifier, and anterior INP division an inhibitor. Division of the anterior INP is a potent anatomic substrate in producing junctional rhythm, and hypoxia involving the sinoatrial node reacts as its synergic factor.

Transesophageal study of recurrent atrial tachycardia after atrial baffle procedures for complete transposition of the great arteries

Transesophageal study was used for diagnosis and treatment of 51 episodes of tachycardia in 13 patients with complete transposition of the great arteries who had undergone atrial baffle procedure. At the time of atrial baffle procedure, patients were 6 to 36 months old (mean 23). Tachycardia (1 to 17 episodes per patient) first occurred 1 to 23 days (4 patients) or 1.8 to 12 years (9 patients) after atrial baffle. Transesophageal study was performed using a bipolar silicone rubber-coated catheter. Tachycardia conversion was accomplished with stimulation bursts using 4 to 10 stimuli 9.9 ms in duration at 20 to 28 mA and an interstimulus interval of 50 to 100 ms less than the atrial cycle length. All tachycardia episodes had regular atrial cycle lengths ranging from 200 to 350 ms. In 12 patients, second-degree atrioventricular (AV) block was observed during tachycardia, suggesting primary atrial tachycardia. However, in 1 patient, occurrence of AV block always resulted in tachycardia termination, suggesting the presence of AV reentrant tachycardia. Transesophageal stimulation converted 48 of 51 tachycardia episodes to sinus/junctional rhythm. Ten tachycardia episodes in 6 patients were transiently converted to atrial fibrillation lasting 3 seconds to 28 minutes before spontaneous conversion to sinus junctional rhythm. Conversion attempts were unsuccessful on 3 occasions. Acceleration of ventricular rate after stimulation necessitated DC cardioversion on 1 occasion. Conversion was not achieved in 2 tachycardia episodes using stimuli less than 10 mA. Transesophageal study is a safe and effective minimally invasive technique for diagnosis and treatment of tachycardia in infants and children who have had atrial baffle for transposition of the great arteries.

Sir Thomas Lewis redivivus: from pebbles in a quiet pond to autonomic storms

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Cardiac rhythm and conduction before and after anatomic correction of transposition of the great arteries

To assess pre- and postoperative arrhythmias associated with anatomic correction of transposition of the great arteries, 34 patients had 145 standard electrocardiograms (ECGs) and 24 of these patients had 46 24-hour ECGs from 11 months before to 54 months after anatomic repair. Twenty-two patients underwent balloon atrial septostomy and 7 surgical atrial septectomy before the initial 24-hour ECG. Anatomic correction included repair of a large ventricular septal defect in 16 patients and an aortopulmonary window in 1 patient. The preoperative standard ECG showed sinus rhythm in every patient. Preoperative 24-hour tapes revealed sinus arrhythmias in 2, sinus bradycardia at a rate of less than or equal to 50 beats/min in 1, junctional rhythm in 1 and rare premature ventricular contractions (PVCs) in 1. The postoperative 24-hour ECG showed atrioventricular dissociation in 1 patient, rare premature atrial contractions in 7, rare PVCs in 8 and sinus bradycardia with junctional escape in 1. Eight patients had PVCs on the postoperative ECG that were not noted on preoperative tapes. No patient had prolonged bradycardia (less than or equal to 50 beats/min), life-threatening arrhythmias or sudden death. Except for 1 patient with atrioventricular dissociation believed to be secondary to a preventable cause, 34 patients followed for 890 patient-months after anatomic correction for transposition of the great arteries had no significant arrhythmias.

A new instrument for surgical creation of an atrial septal defect

An instrument for surgical creation of an atrial septal defect (ASD) was designed and tested in puppies weighing an average of 4.7 kg. Oxygen saturations were obtained in both atria, the superior vena cava, and the inferior vena cava before and after septectomy. The instrument has a cutting cylinder introduced into the right atrium (RA) through the right atrial appendage with a second part (base-plate) inserted into the left atrium (LA) just posterior to the interatrial groove. In 21 animals (Group 1), a single hole was created in dogs killed 48 hours later. In 9 animals (Group 2), an attempt was made to create two adjoining holes. In 14 animals (Group 3), a single hole was created and the dogs were allowed to triple their body weight before they were killed. Group 1 dogs demonstrated a 10% increase in average venae cavae--RA oxygen saturation immediately after septectomy and a 9.4 +/- 0.37 mm diameter of the ASD at death; in Group 2, there was a 14% average step-up and a 12.7 +/- 0.6 mm diameter of the ASD; and in Group 3, the diameter of the ASD was 11.5 +/- 0.4 mm, representing a 50% increase in average area with dog growth compared with that of Group 1. After this experience in the production of ASDs in 44 experimental animals, we find that this instrument seems to be reliable, simple, and safe.

Fine structure of cells and their histologic organization within internodal pathways of the heart: clinical and electrocardiographic implications

The fine structure of the normal internodal pathways was studied in 1 human and 2 canine hearts and correlated with histologic observations on more than 100 human and 10 canine hearts. From the electron microscopic studies six different kinds of myocardial cells were classified from two locations: the Eustachian ridge (posterior internodal pathway) and the Bachmann bundle (anterior internodal pathway). Five of the six kinds of cells (working myocardial cells, Purkinje-like cells, either broad or slender transitional cells and P cells, all previously described) were present in both locations. A sixth cell, pleomorphic and dark in appearance, with a special intertwined relation to P cells, is newly designated as an ameboid cell. It was found solely in the Eustachian ridge. In the same area a rare direct contact between a nerve and a myocardial cell was observed. The importance of these different kinds of cells, their respective cell connections, and their topographic locations inside the internodal pathways are discussed relative to certain functions such as rapid conduction and subsidiary pacemaking. The possible influence of these factors on clinical electrocardiographic changes is considered.

Cardiac arrhythmias following the creation of an atrial septal defect in patients with transposition of the great arteries

In 64 children with transposition of the great arteries who underwent a Blalock-Hanlon procedure, pre- and postoperative electrocardiograms were studied regarding the incidence and nature of rhythm disturbances. In another group of 19 patients with transposition of the great arteries, the atrial septal defect was created by a different surgical technique (fossa ovalis resection); this group was studied in the same way and the results were compared.

After the Blalock-Hanlon procedure seven patients developed arrhythmias including atrio-ventricular (A-V) dissociation, wandering pacemaker, bradycardia, atrial flutter, supraventricular tachycardia, supraventricular premature beats, and ectopic atrial rhythm. After fossa ovalis resection rhythm disturbances were present in three patients.

Despite their relatively high incidence it seems unlikely that arrhythmias are a major factor contributing to death irrespective of the technique used; some arrhythmias are transient and serious disturbances of long duration are rare.

Balloon septostomy for transposition of the great arteries

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