Persistent AV Research Articles

Comparison between cryotherapy and radiofrequency energy sources for parahisian accessory pathway percutaneous ablation.

Catheter ablation of parahisian accessory pathways (PHAP) are challenging due to their proximity to the normal conduction system. Retrospective studies suggest that cryoablation has a better safety profile but a higher recurrence rate when compared to radiofrequency ablation (RFCA). The objective of this study was to compare the results of parahisian AP ablation performed by electrophysiologists with experience in both technologies. Prospective single-center, non-blinded and 1:1 model was used. Patients included had parahisian AP confirmed by an electrophysiological study and referred for radiofrequency or cryotherapy ablation according to current guidelines, under fluoroscopic guidance. No electroanatomic mapping was used. A total of 30 patients (mean age of 25±9.4 years; 90% male) were enrolled between Oct/2018 to Feb/2020. Acute success rate between RFCA and CRYO were similar (93% vs. 87%, p = 0.54). A nonsignificant reduction in short-term recurrence rate for RFCA (14% vs. 30%, p = 0.3) and mechanical trauma (6% vs. 20%; p = 0.28) was observed. Long-term recurrence rate and event-free survival time were similar in both groups after 1-year follow-up (p = 0.286). No persistent complete AV block or conduction disturbance was also observed. Considering the limitation of a small sample size and the lack of use of electroanatomic mapping for RFCA, the efficacy and safety profile of parahisian AP ablation with RFCA was not different from CRYO, when performed by experienced electrophysiologists. No cases of permanent complete AV block were reported with either energy modalities.

Feasibility and effectiveness of left bundle branch area pacing after TAVR: the single center experience

Abstract Introduction Transcatheter aortic valve replacement (TAVR) is a safe alternative to open-heart surgery in patients with symptomatic severe aortic stenosis and high surgical risk due to multiple comorbidities, advanced age, and severe left ventricle dysfunction. Due to anatomical considerations of the atrioventricular node, conduction abnormalities requiring the implantation of a pacemaker are common findings after TAVR. High-grade atrioventricular block and new-onset left bundle branch block (LBBB) are the most commonly reported conduction abnormalities after TAVR. Purpose The aim of our study was to assess the feasibility, success rates, and effectiveness of LBBAP in patients requiring pacing after TAVR. Methods A total of 302 patients underwent the TAVR procedure in our institution in the period from January 2022 to November 2023. In this cohort, 38 patients required ventricular pacing in the postoperative period. 16 patients who underwent permanent pacing using LBBAP were included in this observational study. Patients undergoing traditional right ventricular pacing biventricular pacing or leadless pacemaker implantation were excluded from the study. Results LBBAP was successfully performed in 16 patients (89%). 2 patients underwent conventional CRT implantation (1 cardiac resynchronization therapy pacemaker and 1 cardiac resynchronization therapy defibrillator) in order to severe calcification and presence of fibrotic tissue in the target area. The mean age was 60.5±2.74 years, and 10 patients (62.5%) were women. According to the patient’s medical history, 14 patients (84%) had hypertension; coronary artery disease – 2 (12.5%), 2 (12.5%) patients had atrial fibrillation and atrial flutter, and 7 (43.5%) patients had diabetes mellitus. The mean left ventricle ejection fraction (LVEF) was 46.2±14.7%. Interventricular septal thickness 11.8 ± 1.9 mm. Type of conduction diseases: Infranodal AV block and LBBB were present in 9 (56.5%) patients. 5 (31,25%) patients had persistent complete AV block and 2 (12,25%) had Mobitz II AV block. In 2 patients we observed congestive heart failure combined with LBBB. Pre-TAVR QRS morphology was normal in 15 (93%), and RBBB morphology in 1 (7%). The mean QRS duration at baseline was 105±20 ms. Pre-implant QRS duration 135±52 ms. The single-chamber pacemaker was implanted in 1 patient, dual-chamber pacemaker - 13 patients, and cardiac resynchronization therapy defibrillators in 2 patients. Procedural duration and fluoroscopy times were 105. ± 31.9 min and 18 ± 11 min, respectively. Conclusion Complete AV block and new-onset LBBB after TAVR is still an important issue. LBBB correction using conduction system pacing technology is an effective strategy for this type of patient. LBBAP is one of the most exciting developments in pacing therapy over the last few years. Long-term clinical outcomes and safety of physiological pacing data are limited and require further investigations

Changes in Cardiac Structure and Function Following Fistula Ligation in Kidney Transplant Recipients (Cohort Study)

Purpose: International guidelines recommend that haemodialysis access is provided by an arteriovenous fistula (AVF), which enables frequent, reliable access to the circulation, but there are no guidelines to suggest whether these AVFs need to be ligated after kidney transplantation. Cardiovascular morbidity and mortality remain high in recipients of a kidney transplant, the persistence of a patent arteriovenous fistula (AVF) after transplantation may contribute to ongoing maladaptive cardiovascular remodelling. The ability to reverse this maladaptive remodelling by ligation of this AVF is unknown. We conducted this trial to evaluate the effect of AVF ligation on cardiac structure and function in stable kidney transplant recipients. Also we studied the ability of preoperative echocardiographic and non-invasive hemodynamic measurements, including the effects of acute temporary occlusion of the fistula, to predict postoperative left ventricular diameter and mass reduction, by the closure of the fistula.
 Materials and Methods: Nonrandomized controlled trial. kidney transplant recipients (>12 months after transplantation with stable graft function) were divided into 2 groups. The first referred for surgical arteriovenous fistula closure. The second group didn’t receive Fistula closure (control). Standard echocardiographic parameters, heart rate, and blood pressure were assessed preoperatively (fistula closure) at baseline. These measurements were repeated 6 months after surgical closure.
 Findings: Seventeen kidney transplant patients were prospectively studied with 11 case and 6 controls with no fistula closure. Surgical fistula closure decreased left ventricular end-diastolic diameter and mass indexes (29.9_2.4to 27.4_2.1 mm/m2, P<0.001, and 141_37 to 132_39 g/m2, P<0.05, respectively), whereas no changes were seen in controls after a similar delay. Postoperative left ventricular end-diastolic diameter and mass reductions correlated best with the increases in total peripheral resistance (r_0.85, P<0.0001) and mean arterial blood pressure (r_0.64, P_0.006), respectively.
 Conclusions. Surgical closure of arteriovenous fistula reduces left ventricular diameter and mass in kidney transplant recipients. The best predictors of those morphological changes are the rise in blood pressure and total peripheral resistance induced by temporary occlusion of the fistula.
 Implications to Theory, Practice and Policy: Surgical closure of persistent AV fistula after renal transplantation to correct LV geometry and improve symptoms in terms of exertional dyspnea and palpitations.

Left bundle branch area pacing as a first line pacing strategy, which patients should we consider?

Abstract Background A higher right ventricular (RV) pacing burden in those with permanent pacemakers results in accelerated pacing induced cardiomyopathy, in addition to increased incidence of heart failure and mortality [1–3]. This process may necessitate upgrade to a biventricular system in time, as the cardiomyopathy progresses. Physiological conduction system pacing targets such as His-bundle pacing (HBP) or Left Bundle Branch Area Pacing (LBBAP) have been shown to generate comparatively narrower QRS complexes and thus mitigate this cardiomyopathy development [4,5]. The 2021 ESC guidelines have a class 2b indication for consideration of HBP as an alternative to RV pacing in those with AV block and left ventricular ejection fraction >40%, who are anticipated to have >20% ventricular pacing burden [6]. Purpose To retrospectively identify ECG, echocardiographic, permanent pacemaker (PPM) setting and patient factors associated with high RV pacing burden that may aid selection of those who may benefit from conduction system pacing (CSP). Methods We retrospectively identified 300 consecutive patients who underwent cardiac implantable electronic device insertion in our Electrophysiology Lab from the years 2017–2018. We excluded patients who underwent generator replacements, in addition to those who had biventricular devices or implantable cardioverter defibrillators inserted. We collated ECG, echo, past medical history and pacing data for each patient over a three-year follow up period. Data were analysed using SPSS v.26. Results 160 patients met inclusion criteria. Those with an RV pacing burden >20% were categorised group one (n=85) and those with <20% in group two (n=75). Baseline characteristics of these two groups are compared in Table 1 and Table 2. Our analysis showed that significant differences between these groups included a lower mean HR (Table 1) (55.1±17.8 vs 57.63±17.4) with a more prolonged PR interval (225.7ms ± 8.34 vs. 188.6ms ± 6.62) or atrial fibrillation/flutter (AF/AFL) on admission ECG. There were more males with a greater mean age (High Ventricular Paced (VP) = 76.6 years ± 8.4 vs Low VP = 71.23 years ± 12.3) in the higher VP group, and they demonstrated more incidence of dilated RA/RV on echo (Enlarged RA = 30.5%; Enlarged RV = 23.6% vs 10% and 8.4% respectively). There were significant differences in PPM indications and setting between groups (Table 2), with the higher VP groups having PPM inserted for persistent high-grade AV block (CHB = 31.5% vs 4.9% and Mobitz 2 = 9.6% vs 0%) and had less MVP mode activated (Mode switch algorithm = 13.3% vs 71%). Conclusion Our data suggests that those with persistent high grade AV block such as Mobitz 2 or CHB should be considered for CSP. Other considerations include older age, male sex, dilated RV/RA, prolonged PR, lower intrinsic HR or AF/AFL on admission ECG. PPM mode switching settings to reduce RV pacing burden should be utilised where possible. Funding Acknowledgement Type of funding sources: None.

P383 THIRD–DEGREE ATRIOVENTRICULAR BLOCK AND HYPERCALCEMIA: NOT ALWAYS JUST THE HEART

Abstract A 81–year–old lady was admitted to the ER due to anorexia, fever and oliguria. Previous medical history was unknown as she had arrived in Italy one month before and her son was not aware of it. Upon arrival she was soporous and bradicardic. Physical examination consisted of mild pulmonary rales, diffuse abdominal pain and leg edema. ECG showed a third–degree atrioventricular block with narrow QRS and average heart rate of 40 bpm with no signs of ischemia. X–ray showed mild congestion. She was admitted to CCU. Blood tests showed hypoglicemia (53 mg/dL), anemia (Hb 9.9g/dL), low platelet count, renal dysfunction (creatinine 1.43mg/dL), high C–reactive protein, normal potassium but high calcemia (13 mg/dL). To investigate hypercalcemia parathyroid hormone was dosed and was in range, so a CT scan was needed to rule out pancreatitis, cancer or bone lesions. Also a cardiac echo was done: it showed a hypertrophic left ventricle with preserved contractility, no significant valvular dysfunctions, normal right sections with pulmonary hypertension, no pericardial effusion. While performing the subcostal view however multiple formations were seen at the hepatic level. CT scan confirmed multiple pathological conglomerating lymphadenopathies in the abdomen towards the femoral region, reaching 5 cm of diameter; no bone lesions were found. Inguinal lymph node biopsy was performed. Due to persistent complete AV block along with persistent hypercalcemia and hypoglycemia despite medical therapy, considering the electrolyte imbalance not corrigible due to a malignancy a pacemaker was implanted. The result of the lymph node biopsy was consistent with a form of Diffuse Large B–Cell Lymphoma. This case highlights how a 3–rd degree AV block may present with non–specific symptoms. When it is found it may not always represent a pure cardiac problem as sometimes it is the epiphenomenon of a systemic disease. Particularity of this case is that cardiologists are less used to take into consideration calcium balance. Nevertheless, although infrequent, hypercalcemia is a cause of significant conduction disease. After having looked for it, searching for its etiology is mandatory as some could be reversible and thus the AV block as well. For this reason, when a complete AV block is found ruling out hypercalcemia is fundamental, taking into consideration that the conduction disease may represent the first red flag of an unknown malignancy

Cryofreezing for slow-pathway modification in patients with slow-fast AVNRT: Efficacy, safety, and electroanatomical relation between sites of transient AV block and sites of successful cryoablation.

Cryoablation has emerged as an alternative to radiofrequency ablation for treating atrioventricular nodal reentrant tachycardia (AVNRT). The aim of this prospective study was to evaluate the efficacy and safety of cryoapplication at sites within the mid/high septal region of Koch's triangle and the relation between sites of transient AV block (AVB) and sites of successful cryoablation. Included were 45 consecutive patients undergoing slow-fast AVNRT cryoablation. Initial delivery of cryoenergy was to the mid-septal to high septal region of Koch's triangle. Transient AVB occurred during cryoenergy delivery in 62% (28/45) of patients. Median distance between sites at which cryofreezing successfully eliminated slow pathway conduction and sites of AVB was 4.0 (3.25-5.0) mm. Sites of successful cryoablation tended to be to the left and inferior to the AVB sites. The atrial/ventricular electrogram ratio was significantly lower at sites of successful cryoablation than at AVB sites (0.25 [0.17-0.56] vs. 0.80 [0.36-1.25], p < .001). Delayed discrete or fractionated atrial electrograms were recorded more frequently at sites of successful cryoablation than at AVB sites (78% vs. 20%, p < .001). No persistent AV conduction disturbance occurred, and 96% (43/45) of patients showed absence of recurrence at a median follow-up time of 25.0 months. Cryoablation of slow-fast AVNRT and targeting the mid/high septal region of Koch's triangle was highly successful. AVB frequently emerged near the site at which the slow pathway was eliminated but always resolved by regulating the energy delivery under careful monitoring, and it may be distinguishable by its local electrogram features.

EXTRA-CARDIAC SHUNT: AN UNUSUAL CAUSE OF STROKE

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Embolic phenomenon, while not contributing as much as a cause as atherosclerotic disease for ischemic stroke, remains an important cause for ischemic stroke. While atrial fibrillation represents the majority of the patients in this subset, there are other less conspicuous causes. Here, we present a case of an ischemic stroke, found to be due to an isolated extra-cardiac shunt without a patent foramen ovale. CASE PRESENTATION: A 56-year-old right-handed female with no significant past medical history presented with left-sided weakness concerning for acute stroke. On admission, her National Institute of Health Stroke Scale (NIHSS) was 20. MRI showed an occlusion of the right middle cerebral artery at M1 and right carotid terminus. Dual anti-platelet therapy (DAPT) and statin were started. Revascularization was achieved with thrombectomy. Deep vein thrombosis was ruled out and trans-thoracic echocardiogram was unremarkable. Telemetry revealed persistent first-degree AV block. Suspecting a cardioembolic etiology, a loop recorder was placed and DAPT was changed to apixaban. Trans-esophageal echocardiogram ruled out valvular abnormalities or clots, but identified an extra-cardiac shunt, suspected to be from pulmonary arteriovenous malformation (PAVM). Despite the findings, the patient declined further workup in the hospital and was discharged with medical management. DISCUSSION: PAVM, often associated with Osler-Weber-Rendu disease (OWRD) or migraines is a rare cause for stroke.[1] The absence of a capillary bed allows small thrombi or bacteria to reach the systemic circulation. The resulting manifestations can be severe, including cerebrovascular accidents and brain or intra-medullary abscesses.[2] In a study involving over 700 patients with stroke, only 4 with isolated PAVM were identified, suggesting this is a very rare presentation.[3] In our patient, however, there was no history of migraines or clinical features of OWRD other than PAVM (1 out of 4 per Curacao diagnostic criteria). Therefore, we believe the stroke was likely secondary to an isolated PAVM. Studies reported varied approaches on management of isolated PAVM, with majority opted for embolization. There was also varied recommendations on anti-platelet therapy or anti-coagulation. Our patient was managed with anti-coagulation therapy. CONCLUSIONS: Cryptogenic strokes in low-risk patients warrant evaluating for less common causes, such as AVM, as the implications could be devastating. Although there are treatments that lower the risk of recurrent strokes, little is known on the best practice for patients with isolated PAVM. REFERENCE #1: Peery WH. Clinical Spectrum of Hereditary Hemorrhagic Telangiectasi (Osler-Weber-Rendu Disease). Am J Med. 1987;82:9. REFERENCE #2: Kawano H, Hirano T, Ikeno K, Fuwa I, Uchino M. Brain Abscess Caused by Pulmonary Arteriovenous Fistulas without Rendu-Osler-Weber Disease. Intern Med. 2009;48(6):485-487. REFERENCE #3: Kimura K, Minematsu K, Nakajima M. Isolated pulmonary arteriovenous fistula without Rendu-Osler-Weber disease as a cause of cryptogenic stroke. J Neurol Neurosurg Psychiatry. 2004;75(2):311-313. DISCLOSURES: No relevant relationships by Vernon Chan, source=Web Response No relevant relationships by Dana Daoud, source=Web Response No relevant relationships by Jayaram Thimmapuram, source=Web Response

Cryoablation of atypical atrioventricular nodal reentry tachycardia.

Data on ablation for atypical recurrent atrioventricular nodal reentry tachycardia (AVNRT) and long-term follow-up are generally sparse. Furthermore, the rate of recurrence and safety of cryoablation for atypical AVNRT has not been established. We compared patients cryoablated for atypical AVNRT and typical AVNRT during long-term follow-up. All patients (n = 2612) who underwent catheter ablation for AVNRT at the Karolinska University Hospital between January 2009 and August 2019 were analyzed. A total of 91 patients undergoing first-time cryoablation for atypical AVNRT were included. A control group with first-time cryoablation for typical AVNRT was matched in a 1:1 ratio. Patients were followed-up for recurrences for a median of 5.0 years (interquartile range: 3.1-7.5 years). After 5 years, AVNRT recurrence occurred in 10 patients (11.0%) in the atypical AVNRT group and in 8 patients (8.8%) in the typical AVNRT group (hazard ratio: 1.31 [95% confidence interval: 0.52-3.32]; p = 0.568). The duration of the index procedure was significantly longer for atypical compared to typical AVNRT ablation (132.1 ± 49.2 min vs. 110.1 ± 38.8 min; p = 0.001). Transient AV blocks occurred in a similar fashion in the atypical compared to typical group (11 [12.1%] vs. 4 [4.9%]; p = 0.103). However, no ablation induced persistent AV block developed in either group. Cryoablation for atypical AVNRT showed similar rate of recurrences and safety compared to typical AVNRT during long-term follow-up.

Перший досвід застосування в Україні системи NVT Allegra для транскатетерної імплантації протеза аортального клапана та перспективи рутинних інтервенційних втручань на клапані аорти

Мета роботи – представити перший в Україні досвід використання приладу NVT Allegra для проведення процедури транскатетерної імплантації протеза аортального клапана (TAVI) пацієнтам з високим хірургічним ризиком із вираженим аортальним стенозом.Матеріали і методи. У статті наведені клінічні випадки двох пацієнтів віком 90 та 80 років із вираженим аортальним стенозом із середніми градієнтами трансаортального кровотоку 32 та 76 мм рт. ст. та площею відкриття аортального клапана 0,4 та 0,6 см2 відповідно. Обидва пацієнти були визнані хворими з високим хірургічним ризиком.Результати та обговорення. Обом пацієнтам була проведена транскатетерна імплантація протеза аортального клапана трансфеморальним доступом. Після імплантації середні градієнти трансаортального кровотоку становили 13 та 8 мм рт. ст. відповідно. Резидуальна параклапанна недостатність була невеликого ступеня в обох випадках. Висновки. Система NVT Allegra для проведення транскатетерної імплантації протеза аортального клапана є приладом третього покоління, який дозволяє успішно та безпечно виконувати інтервенційну заміну клапана аорти.

Long-term experience of atrioventricular node ablation in patients with refractory atrial arrhythmias.

Atrial fibrillation and other atrial tachyarrhythmias are increasing with age and concomitant morbidity. First options in symptomatic patients are drug treatment and catheter ablation. Nevertheless, a considerable number of patients suffer from refractory atrial tachyarrhythmias despite treatment. Atrioventricular node ablation (AVNA) may be helpful in many of these patients. Therefore, we investigated AVNA patients with a long-term follow-up. We enrolled 82 patients with a follow-up longer than 1year receiving AVNA for drug- and ablation-resistant atrial tachyarrhythmias (AA) in a retrospective manner. Mean follow-up duration was 48 ± 24months. 50% of the patients initially received AVNA to optimize biventricular pacing in cardiac resynchronization therapy, the other 50% because of refractory symptomatic tachyarrhythmias. Persistent AV block was achieved in every patient. Symptom relief and patient satisfaction were high during follow-up. Due to system upgrades there were 63% of patients with a biventricular system during follow-up. In these patients, left-ventricular ejection fraction (LV-EF) increased by 7% (42-49%) after ablation. AVNA is effective in increasing biventricular pacing as well as for symptom relief in patients with refractory atrial tachyarrhythmias. AVNA should be considered as a valuable option in patients with refractory atrial tachyarrhythmias lacking other treatment options.

Factors predicting persistence of AV nodal block in post‐TAVR patients following permanent pacemaker implantation

A common complication of transcatheter aortic valve repair (TAVR) is development of conduction defects requiring pacemaker (PPM) implantation. These defects are not universally permanent. To determine the incidence and predictors of persistent device dependency in patients with PPM implantation following TAVR with a self-expanding prosthesis. Records of patients who underwent post-TAVR PPM implantation were reviewed. Patients with persistent complete AV block (AVBIII) one month post-TAVR were compared to those regaining conduction. Between September 2014 and March 2017, 485 patients underwent TAVR with a self-expanding prosthesis; 77 (15.9%) underwent PPM implantation for AVBIII. Device interrogation at one month was available for 61 patients (79%): 22 (36.1%) had resolution of AVBIII while 39 (63.9%) remained pacemaker-dependent. Pre-TAVR right bundle branch block was more frequent in device-dependent patients (19 of 38, 50% vs 4 of 22, 18%; RR 2.75; P=.01). Device-dependence was associated with AVBIII as the first postprocedural rhythm (37 of 39, 95% vs 12 of 22, 55%; RR 1.74; P<.0001), earlier implantation (median 1d, IQR: 0-1.5d vs 2d, IQR: 1.0-4.0d, P=.0004), and a shorter duration of hospitalization (median 3d, IQR: 2-3.5d vs 4d, IQR: 2-5.75d, P=.03). Pacemaker dependence was also associated with a higher prosthesis-to left ventricular outflow tract (LVOT) diameter (1.45 ± 0.11vs 1.39 ± 0.07; P=.02) and the lack of prior aortic valvuloplasty (5 of 39, 13%vs 8 of 22, 36%; RR 0.35; P=.03). In patients receiving a PPM following self-expanding TAVR, a long-term pacing requirement can be predicted from the timing of AV block, existing conduction-system disease, larger prosthesis-to-LVOT diameter, and the lack of aortic valvuloplasty.

Indication of permanent cardiac pacing after transcatheter aortic valve implantation (TAVISTIM NCT02337140)

Regarding the extent of TAVI's indication to patients with intermediary risks, it seems essential to lower its complication. Conduction disturbances after TAVI remains a major complication without any standardized guidelines to help with its treatment. The primary end-point of this study is to confirm that standard criterion for pacing are reliable in post-TAVI conduction disorders and to analyze the contribution of a systematic electrophysiological study. In TAVI patients, indications for pacing were persistent high-degree atrioventricular block or bundle branch block appearance associated to HV interval longer than 70 ms, 24 hours after the procedure. After a two-month follow-up, clinical and ECG evaluation and 24-hour ECG Holter monitoring were realized in patients without pacemaker and compared to data obtained from the devices in pacemaker implanted patients (% of ventricular pacing > 1%; presence of more than 1 AVB episode). A total of 165 consecutive patients who underwent TAVI were prospectively included. Out of the 165 patients included, 157 were sampled: 20 in the high grade persistent AV block, 5 in the persistent bundle branch heart block with HV interval > 70 ms, 13 with HV interval < 70 ms, and 119 in the temporary conduction disturbances group. Amongst the 22 patients implanted with PMK following the protocol, only 1 had conduction recovery. On the other hand there were 14 patients who didn’t benefit from a PMK implant but should have. HV interval in the bundle branch block group has an 88% specificity and a 44% sensibility. None of the pacing indication would have been missed if considered at day 3 instead of day 2, independently of HV measurement. From this experimental protocol it appears that an HV based algorithm has a good specificity but a poor sensibility. Conduction disorders are stable at day 3 and allow to decide if pacing is needed. Besides QRS duration, PR interval might be of interest in predicting risk of AV block after TAVI.

A tick beat in the electrocardiogram: Persistent third degree block as only manifestation of Lyme disease

Lyme disease is the most common tick-borne illness in North America. A 23-year-old female presented to our emergency department with a chief complaint of sudden dyspnea and chest pain. An electrocardiogram revealed a third degree heart block. She was a resident of the Northeast region of Mexico and referred a recent travel to an endemic area for Borrelia burgdorferi in the center of Mexico in the past weeks. Lyme carditis was diagnosed after enzyme linked immunosorbent assay for IgM antibodies against B. burgdorferi was reported positive and corroborated by a confirmatory immunoblot analysis. Persistent AV block was the only manifestation in our patient, a presentation scarcely reported in literature.

Safety and Efficacy of Cryoablation vs Radiofrequency Ablation of Septal Accessory Pathways: Systematic Review of the Literature and Meta-Analyses

<h3>Background</h3> Radiofrequency ablation (RFCA) of septal accessory pathway (SAPs) locations is associated with a significant rate of first procedure failures and complications. Several single-center studies suggest that cryothermal ablation might be a safer alternative. The purpose of our study was to systematically review the available literature, including the nonpublished experience of our center, and to compare the safety and efficacy of RFCA vs cryoablation of SAPs. <h3>Methods</h3> We conducted an electronic search in MEDLINE guided by key terms. In addition, manual review of editorials, review articles, textbooks, and guidelines was undertaken. The search was restricted to studies in humans and publication dates between January 1991 and December 2012. We recorded patient numbers, demographics, procedural data, outcome data, and procedural complications. A random effects meta-analysis model was performed using Stata (version 10.1, StataCorp, College Station, TX). <h3>Results</h3> Of the 927 articles screened, 128 were selected for detailed review and 55 were finally retained for analysis: 35 reported RFCA between 1991 and 2012, 20 articles reported cryoablation between 2002 and 2012. Of them, 24 studies referred totally or partially to pediatric patients. Additionally, we included our single-center experience of 118 consecutive SAPs undergoing cryoablation. Overall, 3775 patients constitute our study population: 3328 in the RFCA cohort and 447 in the cryoablation cohort. Efficacy outcomes consistently favored RFCA compared to cryoablation. Acute procedural success rate of cryoablation was 84% (95% confidence interval [CI] 78%–88%) vs RFCA 90% (95% CI 87%–92%). Recurrence rate of cryoablation was 21% (95% CI 18%–26%) vs RFCA 11% (95% CI 10%–12%). Long-term success rate after multiple ablation procedures of cryoablation was 73% (95% CI 63%–81%) vs RFCA 90% (95% CI 86%–93%). There were no reported cases of persistent AV block with cryoablation compared to 2.8% (95% CI 2.2%–3.5%) with RFCA. <h3>Conclusions</h3> Studies of RFCA for treatment of SAPs report higher efficacy rates than do studies using cryoablation. However, the excellent safety profile of cryoablation makes it the energy of choice in high-risk SAP ablation, particularly in young individuals.

Management of Postoperative Arrhythmias in Pediatric Patients

Post-operative arrhythmias occur commonly following pediatric cardiac surgery and can result in significant hemodynamic deterioration. Arrhythmias are more likely in the immediate post-operative period due to myocardial injury and ischemia, high catecholamine levels and electrolyte disturbances. At the same time, these arrhythmias are more likely to cause hemodynamic compromise due to the relatively tenuous cardiovascular function of patients immediately after cardiac surgery. Treatment of tachyarrhythmias often requires addressing two separate goals: termination of the arrhythmia and prevention of recurrences. These two objectives necessitate different treatment strategies in reentrant arrhythmias such as orthodromic reciprocating tachycardia, atrial fibrillation and intra-atrial reentrant tachycardia, including atrial flutter. Termination usually involves vagal maneuvers, adenosine administration, rapid pacing, or direct-current cardioversion. Prevention of recurrences, on the other hand, may require antiarrhythmic medications, although removal of central venous lines in the heart should be considered. Conversely, for automatic tachyarrhythmias, such as junctional ectopic tachycardia and ectopic atrial tachycardia, termination and prevention of recurrences usually involve similar modalities, including cooling, antiarrhythmic medications and correction of electrolyte abnormalities. Bradyarrhythmias, either sinus node dysfunction or AV block, can be treated by pacing with temporary epicardial wires in the short-term. In patients with persistent AV block for 7days, however, permanent pacemaker placement may be required.

Comparison of Two Strategies to Reduce Ventricular Pacing in Pacemaker Patients

Managed Ventricular Pacing (MVP) and Search AV+ (SAV+) are two pacing algorithms designed to reduce ventricular pacing. MVP promotes conduction by operating in AAI/R mode with backup ventricular pacing during atrioventricular block (AVB). SAV+ operates in DDD/R mode with a nominal AV extension of 290 ms during atrial sensing and 320 ms during atrial pacing. The reduction in ventricular pacing was compared with these two algorithms in pacemaker patients. The EnRhythm and EnPulse clinical studies assessed the percentage of ventricular pacing (%VP) after 1 month. Each patient's AVB status was assigned using the following hierarchical categories: persistent third-degree AVB (p3AVB), episodic third-degree AVB (e3AVB), second-degree AVB (2AVB), first-degree AVB (1AVB), and no AVB (nAVB). The%VP was tabulated for each AVB status category. Data were available from 322 patients of whom 129 received DDD(R) pacing with the MVP algorithm activated and 193 patients with DDD(R) pacing and the SAV+ function activated, each for a month period. MVP resulted in a significantly lower median%VP than SAV+ in all AVB categories except for p3AVB: nAVB (0.3 vs 2.9, P < 0.0001), 1AVB (0.9% vs 80.6%, P < 0.0001), 2AVB (37.6 vs 99.3, P< 0.002), e3AVB (1.2 vs 42.2, P = 0.02), p3AVB (98.9 vs 100, P = 1.00). MVP resulted in a greater reduction in%VP than SAV+ across all patient groups except persistent third-degree AV block. The greatest reduction in%VP was observed in patients with mildly impaired AV conduction.

High resistance of atrioventricular node to cryoablation: A great safety margin targeting perinodal arrhythmic substrates

Findings from animal studies and small series of patients support the greater safety of cryoenergy over radiofrequency in the ablation of arrhythmic substrates near the AV node. The purpose of this study was to systematically evaluate the electrophysiologic effects of successive cryoenergy applications to the human AV node in order to better define the safety margin of cryothermal ablation. In 15 patients referred for AV nodal ablation, 94 cryomapping and 105 cryoablation applications were delivered through a 6-mm-tip cryothermal ablation catheter (Freezor Xtra, CryoCath) at predefined sites of the triangle of Koch. Temporary effects on AV conduction were observed in 18 (19%) cryomapping and 38 (36%) cryoablation applications. Persistent effects were observed in 9 (9%) cryoablation applications. Persistent effects were associated with cryoablation at the superior third of the triangle of Koch (P = .05), nadir tip temperature < or = -79 degrees C (P = .007), and effect onset time < or =15 seconds (P = .03). Temperature and effect onset time remained statistically significant after multivariate adjustment (P = .01 and .02, respectively). Overall, persistent complete AV block was achieved with cryoenergy in only one patient. In two additional patients, AV conduction remained modified. In the remaining patients, persistent complete AV block was achieved with radiofrequency (median one application per patient). The low rate of persistent AV conduction impairment observed with attempts to cryoablate the AV node supports a great safety margin of perinodal cryothermal ablation.

P1-51: Time-dependent response effects of AV nodal cryoablation at minimal temperatures

Cryothermal ablation is considered the energy of choice in high risk perinodal ablations, due to the absence of persistent AV block cases reported in the literature. Adverse electrophysiologic effects may be observed during cryoablation (at −70° to −80°C) with complete recovery when the application is immediately interrupted. However, if the application is maintained long enough, a permanent lesion is created. We aimed to establish the safety margin in cryoablation applications duration at minimal temperatures (−80°C).

Reduction of Right Ventricular Pacing in Patients with Sinus Node Dysfunction Using an Enhanced Search AV Algorithm

Dual chamber pacing typically results in a high percentage of ventricular pacing. A number of studies have been conducted suggesting detrimental effects of ventricular desynchronization produced by long-term RV pacing. Pacemaker algorithms that extend the AV interval to uncover intrinsic AV conduction have been utilized to reduce ventricular pacing. These algorithms are often limited to AV intervals below 250 ms limiting the ventricular pacing reduction. We hypothesized that by allowing AV intervals to extend beyond 300 ms, a marked reduction in RV pacing can be achieved. A total of 30 patients (17 men, mean age 71 +/- 9) with standard Brady indications, and implanted with a Medtronic Kappa 700 pacemaker, were randomized to 2-week treatments with default Search AV (KSAV) parameters or Enhanced Search AV (ESAV) parameters. The Enhanced Search AV algorithm included the capability for continuous adjustment of AV delays and the ability to auto disable in patients with persistent AV block. Among patients with intact AV conduction, percent VP was greater in KSAV versus ESAV (70 +/- 40% vs 19 +/- 28%, P < 0.001). In patients with persistent AV block, the algorithm suspended appropriately and there was no significant change in the percent VP between both arms of the study. In 18/22 patients, percent VP was reduced below 40%. Substantial reduction in ventricular pacing can be achieved by allowing the AV interval parameters to extend beyond 300 ms using the ESAV algorithm. In patients with AV block, ESAV suspended and patients were paced at their nominal settings.

A23-3 VVIR pacing versus DDDR pacing in patients with persistent atrial fibrillation after AV node ablation

Bacground. Both VVIR pacing and DDDR pacing may be implanted in patients (pts) with persistent atrial fibrillation (AF) after AV node ablation. However, it is still uknown which type of pacing offers greater benefit in this group of pts. Methods. Eighty six pts with persistent AF and AV node ablation were randomly assigned to VVIR or DDDR pacinmg. Pts in VVIR pacing group (n=44) received anticoagulant therapy. Pts in DDDR pacing group (n=42) received antiarrhythmic and anticoagulant drugs. The study end point was a composite of cardiovascular deaths, heart failure, thromboembolic complications, or severe adverse effect of antiarrhythmic drugs. Results. The baseline clinical data were similar among the two pacing groups. Sixty percent of pts had hypertension and 26% coronary artery disease. At a mean follow-up period of 21.6 months, the primary end point occurred in 14 pts (31.8%) in VVIR pacing grup and in 14 pts (33%) in DDDR pacing group. The distribution of the various components of the primary end point was similar in VVIR and DDDR pacing groups. Pts in DDDR pacing group had lower incidence of chronic AF than those in VVIR pacing group (23.8% versus 88%, P<0.001). Conclusion. VVIR pacing is not inferior to DDDR pacing for the prevention of death or morbidity due to cardiovascular causes in pts with persistent AF after AV node ablation, but results in higher development of chronic AF.