Narrowing of the superior vena cava-right atrium junction during radiofrequency catheter ablation for inappropriate sinus tachycardia: analysis with intracardiac echocardiography

Initial experience of a novel method for electrical isolation of the superior vena cava using cryoballoon in patients with atrial fibrillation

BACKGROUND

Damage to the sinus node (SN) has been described as a potential complication of superior vena cava (SVC) isolation. There have been reports of permanent SN injury requiring pacemaker implantation during isolation of the SVC.

HYPOTHESIS

It is safe and effective to isolate SVC with the second-generation 28-mm cryoballoon by using a novel method.

METHODS

Forty-three patients (including six redo cases) with SVC-related atrial fibrillation (AF) from a consecutive series of 650 patients who underwent cryoballoon ablation were included. After pulmonary vein isolation was achieved, if the SVC trigger was identified, the SVC was electrically isolated using the cryoballoon. First, the cryoballoon was inflated in the right atrium (RA) and advanced towards the SVC-RA junction. After total occlusion was confirmed by dye injection with total retention of contrast in the SVC, the SVC-RA junction was determined. Next, the cryoballoon was deflated, advanced into SVC, then reinflated, and pulled back gently. The equatorial band of the cryoballoon was then set slightly (4.32 ± 0.71 mm) above the SVC-RA junction for isolation of the SVC.

RESULTS

Real-time SVC potential was observed in all patients during ablation. The mean time to isolation was 24.5 ± 10.7 s. The SVC was successfully isolated in all patients. The mean number of freeze cycles was 2.5 ± 1.4 per patient, and the mean ablation time was 99.8 ± 22.7 s. A transient phrenic nerve (PN) injury occurred in one patient (2.33%). There were no SN injuries. Freedom from AF rates at 6 and 12 months was 97.7% and 93.0%, respectively.

CONCLUSIONS

This novel method for SVC isolation using the cryoballoon is safe and feasible when the SVC driver during AF is determined and could avoid SN injury. PN function should still be carefully monitored during an SVC isolation procedure.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Three simple but interesting transthoracic echocardiographic road maps for proximal superior vena cava visualisation in healthy young adults

Background

Although much is known about the technical aspects of inferior vena cava visualization, it is much less about its counterpart: the superior vena cava (SVC). The aims of this study therefore, were to describe in detail the different possible two dimensional echocardiographic SVC visualization techniques in healthy young adults and to provide a series of values for its dimensions and Doppler signals.

Methods

The proximal SVC visualization through the three transthoracic windows was initially established in several adult patients, with or without cardiovascular implantable devices. Subsequently a group of 70 completely healthy adults (35 males and 35 females) were studied to determine the values of SVC dimensions and its pulse Doppler signal characteristics. The visualization windows included: a) Modified apical 5-champber view, b) Modified parasternal short axis view of great vessels and c) Modified subcostal view. The SVC dimensions were measured 3–5 cm above the RA-SVC junction at the end of both hold cardiac and respiratory cycles (systole, diastole and inspiration/expiration, respectively). The peak pulse Doppler velocities were only measured at the end-held expiration.

Results

The largest end systolic proximal SVC dimensions at the end of the expiration and inspiration ranged from 8 to 14.0 mm (11 ± 2 mm) and 8.0–14.0 mm (11 ± 2 mm) respectively, and the highest S wave velocity ranged from 0.5 to 0.7 m/s (0.6 ± 0.0 m/s).

Conclusion

This study has provided a detailed technical description for transthoracic proximal SVC visualization in a group of 70 healthy adults and has furnished sets of values for its dimensions and Doppler signal parameters.

Pregnancy-related inappropriate sinus tachycardia: A cohort analysis of maternal and fetal outcomes

Background

Little literature exists regarding the syndrome of inappropriate sinus tachycardia during pregnancy. We aimed to further understand the natural history of inappropriate sinus tachycardia in pregnancy, and to explore maternal and fetal outcomes.

Methods

A retrospective, observational cohort analysis of 19 pregnant women who presented with inappropriate sinus tachycardia.

Results

42% attended the emergency department on more than one occasion with symptoms of inappropriate sinus tachycardia; 32% required hospital admission and 26% required pharmacological therapy. There were no maternal deaths, instances of heart failure or acute coronary syndrome, and no thromboembolic or haemorrhagic complications during pregnancy. Rates of caesarean section were similar to the background rate of our unit (32% and 27%, respectively). Rates of induction were notably elevated (58% vs 25%).

Conclusion

Inappropriate sinus tachycardia in pregnancy is associated with high rates of hospitalization and induction of labour, which may not be mandatory given the clinical findings in this group of women.

Sinus Node Sparing Hybrid Thoracoscopic Ablation Outcomes in Patients with Inappropriate Sinus Tachycardia (SUSRUTA-IST) Registry

BACKGROUND

Medical treatment of inappropriate sinus tachycardia (IST) remains suboptimal. Radiofrequency sinus node (RF-SN) ablation has poor success and higher complication rates.

OBJECTIVE

We aimed to compare clinical outcomes of the novel SN sparing hybrid ablation technique with those of RF-SN modification for IST management.

METHODS

This is a multicenter prospective registry comparing the SN sparing hybrid ablation strategy with RF-SN modification. The hybrid procedure was performed using an RF bipolar clamp, isolating superior vena cava/inferior vena cava with the creation of a lateral line across the crista terminalis while sparing the SN region (identified by endocardial 3-dimensional mapping). RF-SN modification was performed by endocardial and/or epicardial mapping and ablation at the site of earliest atrial activation.

RESULTS

Of the 100 patients (hybrid ablation group, n = 50; RF-SN group, n = 50), 82% were women, and the mean age was 22.8 years. Normal sinus rhythm and rate were restored in all patients in the hybrid group (vs 84% in the RF-SN group; P = .006). Hybrid ablation was associated with significantly better improvement in mean daily heart rate and peak 6-minute walk heart rate compared with RF-SN ablation. The RF-SN group had a significantly higher rate of redo procedures (100% vs 8%; P < .001), phrenic nerve injury (14% vs 0%; P = .012), lower acute pericarditis (48% vs 92%; P < .0001), permanent pacemaker implantation (50% vs 4%; P < .0001) than did the hybrid ablation group.

CONCLUSION

The novel sinus node sparing hybrid ablation procedure appears to be more efficacious and safer in patients with symptomatic drug-resistant IST with long-term durability than RF-SN ablation.

Efficacy of medical and ablation therapy for inappropriate sinus tachycardia: A single-center experience

BACKGROUND

Effective therapy for inappropriate sinus tachycardia (IST) remains challenging with high rates of treatment failure and symptom recurrence. It is uncertain how effective pharmacotherapy and procedural therapy are long-term, with poor response to medical therapy in general.

METHODS

We retrospectively reviewed all patients with the diagnosis of IST at a tertiary academic medical center from 1998 to 2018. We extracted data related to prescribing patterns and symptom response to medical therapy and sinus node modification (SNM), assessing efficacy and periprocedural complication rates.

RESULTS

A total of 305 patients with a formal diagnosis of IST were identified, with 259 (84.9%) receiving at least one prescription medication related to the condition. Beta-blockers were the most commonly used medication (n = 245), with a majority of patients reporting no change or worsening of symptoms, and poor response was seen to other medication classes. Improvement was seen significantly more often with ivabradine than beta blockers, though the sample size was limited (p = .003). Fifty-five patients (18.0% of all IST patients), mean age 32.0 ± 9.1 years, underwent a SNM procedure, with an average of 1.8 ± 0.9 procedures per patient. Acute symptomatic improvement (<6 months) was seen in 58.2% of patients. Long-term complete resolution of symptoms was seen in 5.5% of patients, modest improvement in 29.1%, and no long-term benefit was seen in 65.5% of patients.

CONCLUSIONS

Among all medical therapies, there were high rates of treatment failure or symptom worsening in over three-quarters of patients in our study. Ivabradine was most beneficial, though the sample size was small. While most patients receiving SNM ablation for IST perceive an acute symptomatic improvement, almost two-thirds of patients have no long-term improvement, and resolution of symptoms is quite rare. AV node ablation with pacemaker implantation following lack of response to SNM offered increased success, though the sample size was limited.

Respiratory variability of sinus node activation in humans: insights from ultra-high-density mapping

PURPOSE

Experimental data suggest that shifts in the site of origin of the sinus node (SN) correlate with changes in heart rate and P wave morphology. The direct visualization of the effect of respiration on SN electrical activation has not yet been reported in humans. We aimed to measure the respiratory shifting of the SN activation using ultra-high-density mapping.

METHODS

Sequential right atrial (RA) activation mapping during sinus rhythm (SR) was performed. Three maps were acquired for each patient: basal end-expiratory (Ex), end-inspiratory (Ins), and end-expiratory under isoproterenol (Iso). The earliest activation site (EAS) was defined as the earliest unipolar electrograms (EGM) with a QS pattern and was localized with respect to the ostium of the superior vena cava (SVC; negative values if EAS inside the SVC).

RESULTS

In 20 patients, 49 maps in SR were acquired (20 Ex, 19 Ins, and 10 Iso). Expiratory (944 ± 227 ms) and inspiratory (946 ± 227 ms) SR cycle lengths were similar, but shortened under isoproterenol (752 ± 302 ms). Activation was unicentric in 33 maps and multicentric in 16: 4 during Ins, 10 during Ex, and 2 Iso. EAS location was significantly more cranial in expiration than in inspiration (0.27 ± 12.1 vs 5 ± 11.51 mm, p = 0.01). Iso infusion tends to induce a supplemental cranial shift (-4.07 ± 15.83 vs 0.27 ± 12.7 mm, p = 0.21). EAS were found in SVC in 22.7% of maps (30% Ex, 21% Ins, and 8% Iso).

CONCLUSION

Inspiration induces a significant caudal shift of the earliest sinus activation. In one-third of the cases, sinus rhythm earliest activation is inside the SVC.

Superior vena cava-right atrium junction flow-pattern post-transcatheter closure of patent foramen ovale

BACKGROUND

The patent foramen ovale (PFO) occluder is a bulky metallic device. Its impact on the normal blood flow at the superior vena cava-right atrial (SVC-RA) junction is not clear.

METHODS

We examined SVC-RA junction flow-pattern using pulsed-wave (PW) ultrasound Doppler in 21 patients (4 male, aged 52.7 ± 9 years) who underwent PFO device closure 4-120 months previously, in comparison with 21 age- and sex-matched controls (4 male, aged 51 ± 8.5 years) with structurally normal hearts.

RESULTS

Mean systolic flow velocity at the SVC-RA junction was 60 ± 11 cm/s in the PFO closure group and 64 ± 17 cm/s in the control group (P = 0.27). Mean diastolic blood flow velocity at the SVC-RA junction in those groups was 30 ± 8 and 35 ± 9 cm/s, respectively (P = 0.1).The mean systolic wave duration was 439 ± 52 ms in the PFO closure group and 422 ± 67 ms in the control group (P = 0.4). The mean diastolic wave duration was 320 ± 75 and 277 ± 88 ms, respectively (P = 0.12).

CONCLUSION

The study results show that transcatheter PFO closure does not affect the normal blood flow at the SVC-RA junction.

Early and Delayed Alteration of Atrial Electrograms Around Single Radiofrequency Ablation Lesion

Purpose: The acute effect of radiofrequency (RF) ablation includes local necrosis and oedema. We investigated the spatiotemporal change of atrial electrograms in the area surrounding the site of single standardized pulse of RF energy.

Methods: The study enrolled 12 patients (45–67 years, 10 males) with paroxysmal atrial fibrillation (AF) undergoing ablation procedure with irrigated-tip ablation catheter and 3D navigation. The high-density mapping/remapping (129 ± 63 points) within the circular area with radius of ~10 mm, centered at the pre-specified posterior left pulmonary vein antrum ablation site was performed at baseline, immediately after single RF energy delivery (25 W, 30 s, 20 ml/min) and after 30 min waiting period. Bipolar voltages of atrial electrograms (A-EGM-biV) were averaged within the central and 12 adjacent left atrium segments and their relative change was studied.

Results: After the ablation, overall A-EGM-biV within the mapping zone (3.51 ± 1.89 mV at baseline) reduced to 2.83 ± 1.77 mV (immediately) and to 2.68 ± 1.58 mV (after 30 min waiting period). In per-segment pair-wise comparison, we observed highly significant change in A-EGM-biV that extended up to the distance of 8.8 mm from the lesion core. The maximum early A-EGM-biV attenuation by 39–49% (P < 0.001) was registered in segments adjacent to pulmonary vein ostia. The subsequent (delayed) A-EGM-biV reduction by 17–24% (P < 0.05) was observed in opposite direction from the lesion center.

Conclusions: Significant alteration of atrial electrograms was detectable rather distant from the central lesion. Spatiotemporal development of ablation lesion was eccentric/asymmetric. While acute A-EGM-biV reduction can be attributed predominantly to direct thermal injury, delayed effects are probably due to oedema progression.

Catheter Ablation of Paroxysmal Atrial Fibrillation Originating from Non-pulmonary Vein Areas

Pulmonary veins (PVs) are a major source of ectopic beats that initiate AF. PV isolation from the left atrium is an effective therapy for the majority of paroxysmal AF. However, investigators have reported that ectopy originating from non-PV areas can also initiate AF. Patients with recurrent AF after persistent PV isolation highlight the need to identify non-PV ectopy. Furthermore, adding non-PV ablation after multiple AF ablation procedures leads to lower AF recurrence and a higher AF cure rate. These findings suggest that non-PV ectopy is important in both the initiation and recurrence of AF. This article summarises current knowledge about the electrophysiological characteristics of non-PV AF, suitable mapping and ablation strategies, and the safety and efficacy of catheter ablation of AF initiated by ectopic foci originating from non-PV areas.

High density mapping of inappropriate sinus tachycardia further looks into potential mechanisms

Inappropriate sinus tachycardia (IST) is an incompletely understood condition associating unexpectedly fast sinus rates and debilitating symptoms whose management by sinus node modification/ablation demonstrated limited long-term success. We report about a case of IST who underwent two RF procedures using high density mapping system, highlighting some possibly specific features and discussing potential mechanisms.

The Role of Superior Vena Cava Isolation in the Management of Atrial Fibrillation

The superior vena cava (SVC) has been identified as one of the most common sources of non-pulmonary vein triggers for atrial fibrillation (AF). SVC isolation has been shown to improve long-term maintenance of normal sinus rhythm in patients with paroxysmal AF. However, ablation at the SVC is associated with risks of phrenic nerve injury, sinus node dysfunction, and SVC stenosis. The use of electroanatomical mapping, intracardiac echocardiography, compound motor action potentials, and segmental (rather than circumferential) ablation are all strategies to reduce complications. Given these risks, SVC isolation is most effective as an adjunct to pulmonary vein isolation for patients with paroxysmal AF who have been found to have an arrhythmogenic SVC.

Inappropriate sinus tachycardia in pregnancy: a benign phenomena?

The syndrome of inappropriate sinus tachycardia (IST) is a well-described and generally benign condition outside pregnancy. There is, however, little information in the literature about IST during pregnancy and nothing about the likely mechanism in such cases. Equally there is a paucity of information about the effects on maternal and fetal well-being in patients who develop IST during pregnancy. Here, we describe the case of a woman who developed IST for the first time during pregnancy. We have first given a brief clinical summary of events and then follow this with the patient's personal account which she has written herself specifically for this case report. We believe that this case highlights some of the important issues associated with the condition when it occurs during pregnancy. We hope that the publication of this case report will increase the awareness of IST during pregnancy. This is important as we believe that the correct diagnosis and understanding of the condition and its consequences will allow clinicians to manage women afflicted by the condition empathetically and appropriately.

Ablation of Inappropriate Sinus Tachycardia: A Systematic Review of the Literature

OBJECTIVES

The goal of this study was to describe short- and long-term outcomes in all patients referred for inappropriate sinus tachycardia ablation, along with the potential complications of the intervention.

BACKGROUND

Sinus node (SN) ablation/modification has been proposed for patients refractory to pharmacological therapy. However, available data derive from limited series.

METHODS

The electronic databases MEDLINE, Embase, CINAHL, Cochrane, and Scopus were systematically searched (January 1, 1995-December 31, 2015). Studies were screened according to predefined inclusion and exclusion criteria.

RESULTS

A total of 153 patients were included. Their mean age was 35.18 ± 10.02 years, and 139 (90.8%) were female. All patients had failed to respond to maximum tolerated doses of pharmacological therapy (3.5 ± 2.4 drugs). Mean baseline heart rates averaged 101.3 ± 16.4 beats/min according to electrocardiography and 104.5 ± 13.5 beats/min according to 24-h Holter monitoring. Two electrophysiological strategies were used, SN ablation and SN modification, with the latter being used more. Procedural acute success (using variably defined pre-determined endpoints) was 88.9%. Consistently, all groups reported high-output pacing from the ablation catheter to confirm absence of phrenic nerve stimulation before radiofrequency delivery. Need of pericardial access varied between 0% and 76.9%. Thirteen patients (8.5%) experienced severe procedural complications, and 15 patients (9.8%) required implantation of a pacemaker. At a mean follow-up interval of 28.1 ± 12.6 months, 86.4% of patients demonstrated successful outcomes. The symptomatic recurrence rate was 19.6%, and 29.8% of patients continued to receive antiarrhythmic drug therapy after procedural intervention.

CONCLUSIONS

Inappropriate sinus tachycardia ablation/modification achieves acute success in the vast majority of patients. Complications are fairly common and diverse. However, symptomatic relief decreases substantially over longer follow-up periods, with a corresponding high recurrence rate.

Strategies for phrenic nerve preservation during ablation of inappropriate sinus tachycardia

BACKGROUND

Radiofrequency (RF) ablation can alleviate drug-refractory inappropriate sinus tachycardia (IST). However, phrenic nerve (PN) injury and other complications limit its use.

OBJECTIVE

The purpose of this study was to characterize the maneuvers used to avoid PN injury and the long-term clinical outcomes.

METHODS

The study consisted of a retrospective analysis of consecutive patients who underwent ablation for IST.

RESULTS

RF ablation was performed on 13 consecutive female patients with drug-refractory IST. Eleven patients exhibited PN capture at desired ablation sites. In 1 patient, PN capture was not continuous throughout the respiratory cycle and ventilation holding sufficed to avoid PN injury. In 10 patients, pericardial access (PA) and balloon insertion was required. Initially (n = 4) a posterior PA was used, which was replaced by an anterior PA in the subsequent 6 cases. PA to optimal balloon positioning time was significantly lower in anterior vs posterior PA (16.3 ± 6 minutes vs 58 ± 21.3 minutes, P = .01), as was fluoroscopy time (15.66 ± 16.72 min vs 35.9 ± 1.8 min, P = .03). RF ablation successfully reduced sinus rate to <90 bpm in 13 of 13 patients. Procedure times and total RF times were not significantly different in anterior vs posterior PA. Major complications occurred in 2 patients, including unremitting pericardial bleeding requiring open-chested repair in 1 patient and sinus pauses mandating pacemaker implantation in the other patient. Long-term symptom control after follow-up of 811 ± 42 days was successful in 84.6%.

CONCLUSION

Ventilation holding and/or pericardial balloon insertion are frequently warranted in IST ablation. Anterior PA appears to facilitate the procedure over posterior PA.

Catheter ablation of inappropriate sinus tachycardia

Catheter ablation for inappropriate sinus tachycardia (IST) is recommended for patients symptomatic for palpitations and refractory to other treatments. The current approach consists in sinus node modification (SNM), achieved by ablation of the cranial part of the sinus node to eliminate faster sinus rates while trying to preserve chronotropic competence. This approach has a limited efficacy, with a very modest long-term clinical success. To overcome this, proper patient selection is crucial and an epicardial approach should always be considered. This brief review will discuss the current role and limitations of catheter ablation in the management of patients with IST.

Superior Vena Cava Isolation In Ablation Of Atrial Fibrillation

Superior vena cava (SVC) is one of the most important non-pulmonary vein (PV) origins of atrial fibrillation (AF). SVC isolation (SVCI) is effective especially in patients with paroxysmal AF from SVC origin. However, SVCI should be carefully performed because of potential complications such as phrenic nerve paralysis, SVC stenosis, and sinus node injury There are two major different approaches to treat SVC focus in the ablation of AF. The conventional approach is to perform SVCI only if AF from the SVC origin is actually recognized using pacing maneuvers and/or isoproterenol infusions. Another approach is the empiric empiricprophylactic SVCI in addition to PV isolation in all cases. The rate of AF freedom one year after initial AF ablation by empiric SVCI was almost same as the conventional method (85-90% AF freedom). Additionally, the conventional method has also a good result even 5 years after ablation (,73.3% AF freedom). Because of the excellent result in the conventional approach and possible complications after the SVCI, the empiric SVCI + PVI in all AF cases is still controversial. Patients with a long SVC myocardial sleeve are possible candidates for empiric SVCI in addition to PVI.

Modeling atrial arrhythmias: impact on clinical diagnosis and therapies

Atrial arrhythmias are the most frequent sustained rhythm disorders in humans and often lead to severe complications such as heart failure and stroke. Despite the important insights provided by animal models into the mechanisms of atrial arrhythmias, direct translation of experimental findings to new therapies in patients has not been straightforward. With the advances in computer technology, large-scale electroanatomical computer models of the atria that integrate information from the molecular to organ scale have reached a level of sophistication that they can be used to interpret the outcome of experimental and clinical studies and aid in the rational design of therapies. This paper reviews the state-of-the-art of computer models of the electrical dynamics of the atria and discusses the evolving role of simulation in assisting the clinical diagnosis and treatment of atrial arrhythmias.

Correlative anatomy for the electrophysiologist: ablation for atrial fibrillation. Part I: pulmonary vein ostia, superior vena cava, vein of Marshall

Ablation procedures for atrial fibrillation (AF) have become an established and increasingly used option for managing patients with symptomatic arrhythmia. The anatomic structures relevant to the pathogenesis of AF and ablation procedures are varied and include the pulmonary veins (PVs), other thoracic veins, the left atrial myocardium, and autonomic ganglia. Exact regional anatomic knowledge of these structures is essential to allow correlation with fluoroscopy and electrograms, and, importantly, to avoid complications from damage of adjacent structures within the chest. We have presented this information in a 2-part series. In the present article, we examine the general anatomic characteristics of the PVs, superior vena cava, and vein of Marshall. Features of particular relevance for the invasive electrophysiologist are pointed out. In a subsequent article, we discuss the regional anatomy of the left and right atria and anatomic considerations in preventing complications during AF ablation.

Full-motion two- and three-dimensional pulmonary vein imaging by intracardiac echocardiography after pulmonary vein isolation

BACKGROUND

The pulmonary veins (PVs) are topographically complex and motile, so angiographic visualization of the PVs anatomy is limited. An imaging technique that accurately portrays the pulmonary vein (PV) anatomy would be valuable during and after catheter ablation procedures.

PURPOSE

We investigated whether three-dimensional (3D) intracardiac echocardiography (ICE) can visualize radiofrequency (RF)-induced tissue changes after PV isolation.

METHODS

We performed 3D ICE studies with a 9F, 9-MHz ICE catheter after segmental or extended PV isolation. The ICE catheter was placed 3-4 cm inside the PV ostium and mounted onto a pullback device. Sequential two-dimensional (2D) images of the full length of the vein were obtained in 0.3 mm steps with cardiac and respiratory cycle gating. Each image was fed into a computer, and the aggregate data set was reconstructed into a 3D, full-motion image. RF lesion location and lesion size were studied on 67 pullback images from 29 patients.

RESULTS

The 2D and 3D reconstruction was possible for 27 left superior PVs, 13 left inferior PVs, 26 right superior PVs, and one right inferior PV. The ablation site was identified 3-7 mm inside the PV ostium, and a 1/2 - 4/5 circumferential area was ablated with no clinically relevant stenosis. No significant differences were found on the ablated area or ablation site between segmental and extensive PV isolation.

CONCLUSION

The 2D and 3D ICE of the PVs provides detailed anatomical information of the proximal PVs, and RF-induced tissue changes in the PV wall can be visualized by ICE.

Electrical Isolation of the Superior Vena Cava: An Adjunctive Strategy to Pulmonary Vein Antrum Isolation Improving the Outcome of AF Ablation

PV isolation at the antrum (PVAI) has improved safety and efficacy of ablation procedures for atrial fibrillation (AF). AF triggers from the superior vena cava (SVC) may compromise the outcome of PVAI.

PURPOSE

We evaluated the (1) incidence of SVC triggers, (2) feasibility of empiric SVC electrical isolation (SVCI) as an adjunct to PVAI, and (3) SVCI safety.

METHODS AND RESULTS

Of 190 patients (group I), 24 (12%) showed SVC triggers. Following PVAI, seven patients had AT originating from the SVC and three had AF. After SVCI, all 24 patients were arrhythmia-free 450 +/- 180 days post procedure. In the subsequent 217 patients (group II), empirical SVCI was performed following PVAI. Sixty-six of all 407 patients (16%) experienced recurrence of AF. A repeat procedure in 25 of the 66 patients showed that five (20%) had AF recurrence initiated by SVC triggers, of whom four were among group I patients (4/190; 2%) and one was from group II (1/217; 0.4%), (P < 0.05). Transient diaphragmatic paralysis can be avoided by pacing at the lateral aspect of the SVC using high output (30 mA). There was no SVC stenosis on CT scans before or 3 months after the procedure. There was no sinus node injury.

CONCLUSIONS

The SVC harbors the majority of non-PV triggers of AF. SVCI is feasible, safe, and may be considered as an adjunctive strategy to PVAI for ablation of AF. The long-term favorable outcome of this hybrid approach remains to be evaluated in a larger series of patients.

Use of Noncontact Mapping and Saline-Cooled Ablation Catheter for Sinus Node Modification in Medically Refractory Inappropriate Sinus Tachycardia

BACKGROUND

Inappropriate sinus tachycardia (IST) is characterized by heart rate (HR) increase out of proportion to stress level. Radiofrequency (RF) modification of the sinus node (SN) is an accepted treatment modality for medically refractory IST. We describe a new technique using noncontact mapping and a saline irrigated catheter for SN modification.

METHODS

Seven consecutive patients with medically refractory IST were referred for ablation. Intrinsic heart rate (IHR) was calculated with complete autonomic blockade by atropine and propranolol. Isoproterenol (ISO) 1 mcg/min was initiated and increased to 10 mcg/min. Site of earliest activation was tagged at each dose of ISO once stable HR was achieved. RF ablation to target site of earliest activation at peak HR on ISO 10 mcg/min was performed. With any change in P-wave morphology, activation was reassessed and the new site of earliest activation targeted. Endpoint was a decrease in HR and change in P-wave morphology in lead III and aVF.

RESULTS

Five of seven patients had abnormal IHR. Mean number of RF lesions was 25 (10-52). All patients had either flattening of the P wave or development of negative P waves in leads III and aVF post RF associated with a decrease in HR of > or = 25% from baseline off ISO. A caudal shift of the site of early activation compared with baseline was observed. One patient who had a prior SN modification developed symptomatic intermittent junctional bradycardia and required an atrial pacemaker 2 weeks later. The other 6 patients in follow-up from 6 to 24 months had no further IST.

CONCLUSIONS

Noncontact mapping using the described technique in conjunction with the saline-cooled ablation catheter for SN modification in the treatment of IST may provide effective HR control.

Acute and Chronic Effects of Extensive Radiofrequency Lesions in the Canine Caval Veins: Implications for Ablation of Atrial Arrhythmias

BACKGROUND

Although radiofrequency (RF) ablation within the caval veins has been increasingly used to treat a variety of atrial tachyarrhythmias, the consequences of RF ablation in the caval veins are unknown. We explored the acute and chronic angiographic and pathological effects of extensive RF ablation in the caval veins.

METHODS

Under fluoroscopy guidance, conventional (4 mm tip, 60 degrees C, 60 seconds) RF applications (n = 6-7) were delivered in each vena cava (from +/-2 cm into the vein to the veno-atrial junction) of 15 dogs (10 +/- 3 kg). Animals were killed 1 hour and 5 weeks after ablation for histological analysis. Angiography was performed before ablation (acute dogs only) and at sacrifice to assess the degree of vascular stenosis.

RESULTS

In acute dogs (n = 5), luminal narrowing was noted in 10/10 (100%) targeted veins (mild in two; moderate in three and severe in five, including two total occlusions). In the six chronic animals that completed the protocol (four died during follow-up), stenosis was also observed in 12/12 (100%) ablated veins (mild in six; moderate in four and severe in two). Of these, one superior vena cava was suboccluded with development of extensive collateral circulation. Histologically, acute lesions displayed typical transmural coagulative necrosis, whereas chronic lesions revealed intimal proliferation, necrotic muscle replaced with collagen, endovascular contraction, and disruption and thickening of the internal elastic lamina.

CONCLUSION

In this model, extensive RF ablation in the caval veins may result in significant vascular stenosis. These findings may have implications for catheter ablation of arrhythmias originating within the caval veins.

Intracardiac echocardiographic anatomy for the interventional electrophysiologist

The development of intracardiac echo has led to an increasing appreciation of the important relationship between arrhythmia mechanism and anatomy. This review describes the anatomic structures involved in arrhythmia mechanism that may be imaged with ICE and the use of intracardiac echo to guide mapping and ablation.