Parvin C. Dorostkar

Mapping and radiofrequency ablation of intraatrial reentrant tachycardia after the senning or mustard procedure for transposition of the great arteries

The Senning and Mustard procedures are often associated with the development of atrial tachyarrhythmias, which may be a cause of sudden death. We hypothesized that atrial surgery creates barriers to impulse propagation, establishing potential routes for atrial reentry, and that mapping combined with knowledge of the surgical anatomy could identify zones that are critical to the tachycardia to be targeted for radiofrequency catheter ablation. Patients underwent mapping to identify early sites of atrial activation that were related to anatomic or surgically created obstacles, with confirmation by pacing to demonstrate concealed entrainment. Radiofrequency lesions were placed to connect these obstacles, while observing for tachycardia termination. Thirteen tachycardias were attempted in 10 patients, 10 successfully. Three patients had 2 distinct tachycardias. Successful sites were in right atrial tissue, although in many, a retrograde approach to the pulmonary venous atrium was necessary. Ablation of the clinically documented tachycardia was successful in 9 of 10 patients. The most common successful site was the region of the coronary sinus mouth, approached antegrade or retrograde. Ablation of intraatrial reentrant tachycardias after the Senning or Mustard procedure is feasible using concealed entrainment mapping techniques, but requires a detailed knowledge of the individual surgical anatomy and the ability to approach the pulmonary venous atrium. Radiofrequency ablation offers significant advantages over other management modalities in this patient group.

Electrophysiologic Effects of Adenosine in Patients With Supraventricular Tachycardia

BACKGROUND We correlated the electrophysiologic (EP) effects of adenosine with tachycardia mechanisms in patients with supraventricular tachycardias (SVT). METHODS AND RESULTS Adenosine was administered to 229 patients with SVTs during EP study: atrioventricular (AV) reentry (AVRT; n=59), typical atrioventricular node reentry (AVNRT; n=82), atypical AVNRT (n=13), permanent junctional reciprocating tachycardia (PJRT; n=12), atrial tachycardia (AT; n=53), and inappropriate sinus tachycardia (IST; n=10). There was no difference in incidence of tachycardia termination at the AV node in AVRT (85%) versus AVNRT (86%) after adenosine, but patients with AVRT showed increases in the ventriculoatrial (VA) intervals (13%) compared with typical AVNRT (0%), P<0.005. Changes in atrial, AV, or VA intervals after adenosine did not predict the mode of termination of long R-P tachycardias. For patients with AT, there was no correlation with location of the atrial focus and adenosine response. AV block after adenosine was only observed in AT patients (27%) or IST (30%). Patients with IST showed atrial cycle length increases after adenosine (P<0.05) with little change in activation sequence. The incidence of atrial fibrillation after adenosine was higher for those with AVRT (15%) compared with typical AVNRT (0%) P<0.001, or atypical AVNRT (0%) but similar to those with AT (11%) and PJRT (17%). CONCLUSIONS The EP response to adenosine proved of limited value to identify the location of AT or SVT mechanisms. Features favoring AT were the presence of AV block or marked shortening of atrial cycle length before tachycardia suppression. Atrial fibrillation was more common after adenosine in patients with AVRT, PJRT, or AT. Patients with IST showed increases in cycle length with little change in atrial activation sequence after adenosine.

Electroanatomical mapping and ablation of the substrate supporting intraatrial reentrant tachycardia after palliation for complex congenital heart disease

In patients with congenital heart disease who have undergone palliative surgical interventions postoperative arrhythmias frequently complicate tbe clinical course. Intraatrial reentrant tachycardias(LAHTs) are one of the most common forms of postoperative arrhythmias in these patients and can lead to significant morbidity and even mortality. Drug therapy and/or antitachycardia pacing have been disappointing. Ablative therapy with radiofrequency energy offers a potential for cure for these patients but the conventional approach using multielectrode recordings and fluoroscopic guidance is technically difficult and provides limited success. Recent development of a novel nonfluoroscopic technology with electroanatomical mapping using the CARTO mapping/ablation system has shown promising results in defining the arrhythmia circuit, facilitating diagnosis, and guiding ablative therapy. Rased on our preliminary experience, a systematic approach to postoperative IART using electroanatomical mapping is described. Further studies are needed to fully evahiate the impact of this new technology on the management and therapy of IART.

Clinical Course of Persistent Junctional Reciprocating Tachycardia

OBJECTIVE The purpose of this study is to review the clinical course of persistent junctional reciprocating tachycardia (PJRT) in 21 patients spanning a wide age range to examine the electrophysiologic characteristics of the conduction system in these patients with PJRT, particularly in regards to its incessant nature and to evaluate the long-term response to radiofrequency ablation. BACKGROUND Persistent junctional reciprocating tachycardia is uncommon, occurring in 1% of patients with supraventricular tachycardia. Its presentation, course and treatment are incompletely characterized. METHODS The clinical, electrocardiographic, electrophysiologic and echocardiographic data of 21 patients with PJRT were reviewed. RESULTS In 9 of these 21 patients, the mean tachycardia cycle length increased significantly (p < 0.0001) as the patients grew, from a mean tachycardia cycle length of 308+/-64 ms in the patients less than 2 years, 414+/-57 ms in the patients between 2 years and 5 years, to 445+/-57 ms in the patients greater than 5 years, primarily due to slowing of retrograde conduction in the accessory pathway. Persistent junctional reciprocating tachycardia was associated with impaired ventricular function in 11, improving spontaneously in 4 and, after successful ablation of the accessory pathway, in 7. All patients except one were uncontrolled on one or more medications. Ablation of the accessory pathway was successful in 19 of 21 patients. CONCLUSIONS We conclude that PJRT is characterized by an onset in early childhood and by an age-related prolongation of the tachycardia cycle length mediated primarily through conduction delay in the concealed, retrogradely conducting accessory pathway. Ablation of the accessory pathway provides definitive treatment for PJRT.

Electrophysiology of "incisional" reentrant atrial tachycardia complicating surgery for congenital heart disease

Intraatrial reentrant tachycardia, which occurs frequently in patients who have undergone corrective surgery for congenital heart disease, presents a challenge to successful management. Because the surgical repair sites are invariably critical to the development and maintenance of reentrant atrial tachycardia, we use the term “incisional reentry” to describe these arrhythmias. An understanding of the electrophysiology of such “incisional reentry,” and techniques to identify a critical isthmus, are essential for successful ablation of these circuits. A critical isthmus may be identified by the presence of entrainment with concealed fusion. Confirmation that the site is critical to the tachycardia circuit is obtained by an analysis of the relationship between the postpacing interval and the tachycardia cycle length. Advances in mapping from multiple simultaneous sites, along with the ability to create larger, deeper lesions will be needed in order to cure a larger number of these patients. Ultimately, in some cases one must consider each procedure palliative rather than curative, as the disease progresses and substrate evolves and more tachycardia circuits become active.

Narrow complex tachycardia with VA block: Diagnostic and therapeutic implications

To review our experience with cases of narrow complex tachycardia with VA block, highlighting the difficulties in the differential diagnosis, and the therapeutic implications. Prior reports of patients with narrow complex tachycardia with VA block consist of isolated case reports. The differential diagnosis of this disorder includes: automatic junctional tachycardia, AV nodal reentry with final upper common pathway block, concealed nodofascicular (ventricular) pathway, and intra‐Hissian reentry. Between June 1994 and January 1996, six patients with narrow complex tachycardia with episodes of ventriculoatrial block were referred for evaluation. All six patients underwent attempted radiofrequency ablation of the putative arrhythmic site. Three of six patients had evidence suggestive of a nodofascicular tract. Intermittent antegrade conduction over a left‐sided nodofascicular tract was present in two patients and the diagnosis of a concealed nodofascicular was made in the third patient after ruling out other tachycardia mechanisms. Two patients had automatic junctional tachycardia, and one patient had atroventricular nodal reentry with proximal common pathway block. Attempted ablation in the posterior and mid‐septum was unsuccessful in patients with nodofascicular tachycardia. In contrast, those with atrioventricular nodal reentry and automatic junctional tachycardia readily responded to ablation. The presence of a nodofascicular tachycardia should be suspected if: (1) intermittent antegrade preexcitation is recorded, (2) the tachycardia can be initiated with a single atrial premature producing two ventricular complexes, and (3) a single ventricular extrastimulus initiates SVT without a retrograde His deflection. The presence of a nodofascicular pathway is common in patients with narrow complex tachycardia and VA block. Unlike AV nodal reentry and automatic junctional tachycardia, the response to ablation is poor.

Stent redilation in canine models of congenital heart disease: Pulmonary artery stenosis and coarctation of the aorta

In a canine puppy model, pulmonary artery stenosis was created by banding the left pulmonary artery to 30-40% of its original diameter. Animals underwent right heart catheterization and angiography 1-2 mo later, and Palmaz P308 stents were implanted. Stent redilation was performed 3-5 mo later. One mo postredilation, the animals were restudied and sacrificed. Coarctations of the aorta were created by transverse aortic incision and longitudinal repair. P308 stent implantation was performed 2-3 mo later. Stent redilation was performed after 6-10 mo, and the animals were restudied and sacrificed 1-2 mo later. Stent implantation was performed in 6 puppies with pulmonary artery stenosis, as 2 animals developed postoperative pulmonary arterial hypoplasia, precluding stenting. The stenosis diameter increased from 4.8 +/- 0.5 mm to 7.4 +/- 0.6 mm (mean +/- SE) following stenting (P = 0.005), and increased further to 9.2 +/- 0.7 mm following redilation (P < 0.001). There were no significant vessel tears or ruptures. Coarctation stenting was performed in 8 animals. The coarctation was dilated from 5.8 +/- 0.9 mm to 9.8 +/- 0.6 mm (P < 0.001), and to 13.5 +/- 0.5 mm at redilation (P = 0.002). Redilation could not be performed in 1 animal. Aortic rupture and death occurred in 2 of 7 animals at redilation. Stent implantation and redilation in experimental pulmonary artery stenosis appears safe and effective. Though stent implantation for coarctation of the aorta appears safe, there was a 28% aortic rupture rate at stent redilation in this model.

Asystole and Severe Bradycardia in Preterm Infants

Transient episodes of apnea and bradycardia are common in preterm infants. Pronounced asystole or sinus arrest, however, is relatively rare and the clinical significance of such events is unknown. Objective: The purpose of our study was to: (1) evaluate the prevalence of severe bradycardic and asystolic events in infants studied with polygraphic cardiorespiratory monitoring, (2) characterize these events, and (3) correlate the events with other clinical findings. Methods: A total of 583 studies were performed in 454 preterm infants at a post-conceptional age 37.4 ± 2.5 (range 34–42 weeks). Asystolic pauses were defined as no QRS complex for ≧3 s consistent with a heart rate <20 beats per minute (bpm). Severe bradycardia was defined as no QRS for ≧2 s consistent with a heart rate of 21–30 bpm. Results: Eight infants (29.5 ± 3.9 weeks’ gestational age, birth weight 1,283 ± 445 g) met the criteria of having had at least 1 asystolic event (heart rate ≤20 bpm). These infants had a total of 32 episodes of bradycardia ≤30 bpm, of which 22 episodes were classified as asystole. During the asystolic episodes, the P-R interval remained unchanged in 21 of 22 episodes and prolonged in 1. One patient had non-sustained ventricular tachycardia before resumption of normal sinus rhythm. All asystolic events were associated with apnea (mean duration of 17.7 ± 9.4 s) and O2 saturations fell by 10 ± 6%. A pH probe study was available in 9 of 22 asystolic events and 6 of 10 severe bradycardic events. Gastroesophageal reflux was temporally related to only one asystolic and two bradycardic events. Clinical follow-up of these infants at a mean age of 14 months (range 1–46) reveals no symptomatic sequelae; although 1 infant died from multisystem failure associated with multiple congenital anomalies. Conclusions: Asystolic pauses occur in 1.8% of a selected population of preterm infants who have been experiencing cardiorespiratory events, are related to respiratory pauses, and appear to have a benign long-term outcome, although future study should incorporate long-term neurodevelopmental outcome.

Quantitative effects of functional bundle branch block in patients with atrioventricular reentrant tachycardia.

Changes in the retrograde conduction time (ventriculoatrial [VA]) interval during functional bundle branch block (BBB) have been used to separate septal from free wall accessory pathways (APs), but different values of the VA interval prolongation (deltaVA) have been described in different reports. A total of 95 patients with single nondecremental APs who developed BBB during atrioventricular reentrant tachycardia were studied. Free wall APs were found in 60 patients, and 35 had septal APs. For patients with free wall APs, complete and incomplete BBB ipsilateral to the atrial insertion site of APs were observed in 39 of 60 patients (65%) and 31 of 60 patients (52%), respectively. For patients who had both complete (QRS > or = 120 ms) and incomplete (QRS <120 ms) BBB during atrioventricular reentrant tachycardia, deltaVA for patients with complete BBB was significantly greater than in those with incomplete BBB, 59 +/- 19 ms versus 30 +/- 11 ms, p <0.001. For patients with septal APs and complete and incomplete BBB during tachycardia, the mean deltaVA for those with complete BBB was 31 +/- 20 ms and was significantly longer than in patients with incomplete BBB (14 +/- 6 ms), p <0.001. There was no significant difference in deltaVA between those with free wall APs and incomplete BBB compared with those with septal APs and complete BBB. The criteria of QRS > or = 120 ms associated with deltaVA > or =40 ms served to best separate free wall from septal APs with a sensitivity of 88% and a specificity of 89%. Left anterior fascicular block was associated with marked lengthening of deltaVA for those with left free wall APs, whereas a left posterior fascicular block pattern resulted in a marked increase in the deltaVA for patients with posteroseptal APs. In the absence of fascicular block patterns, a deltaVA > or =40 ms provides strong evidence of a free wall AP, with a sensitivity of 95% and a specificity of 100%. The left posterior fascicle appears to provide predominant innervation of the posterior septum.

Outcomes of emergent cardiac catheterization following pediatric cardiac surgery

Background: Although there is agreement of the importance of cardiac catheterization, especially interventional procedures, cardiac catheterization in postoperative critical care unit (CCU) period is often debated. The focus of this study was to explore the indications for and determinants of outcome after cardiac catheterization in this setting. Methods: Between March 2004 and October 2006, 49 children (2.8% of cardiac surgeries) underwent 62 catheterizations before discharge from the CCU. Morphological, surgical, and catheterization data were accrued and analyzed using parametric competing risks models and multivariable risk‐hazard analysis. Results: Median age at surgery was 167 days (0–13.5 years) and time to catheterization was 8.5 (0–84) days following surgery. Catheterization procedures were either interventional (n = 35) or noninterventional (n = 27). Children who required a more urgent investigation following initial surgery more often had deployment of a stent at catheterization (P = 0.01) or subsequent surgical pulmonary artery augmentation (P < 0.01). Surgical reoperation was required following 23 (37%) catheterizations and was more common following index surgery involving a cavopulmonary shunt. Overall mortality was high (43%). Delayed invasive investigation beyond 2–3 weeks (P = 0.04) or a splinted sternum (P < 0.001) were risk factors for death. In addition, reoperation after a noninterventional catheterization predicted worse survival (P < 0.001). Conclusions: The need for invasive investigation in the immediate CCU period is associated with a poor outcome, especially when the investigation is delayed or an intervention is not possible. Identification of at‐risk patients may improve outcomes. Best outcomes follow expedient catheterization with definitive management (often stent deployment or pulmonary artery augmentation).