Rapid detection of isthmus block and rhythm change using local electrogram changes during complex atrial flutter ablation.

AIMS: Multiple re-entry circuits may operate simultaneously in the atria in the form of dual loop re-entry using a common isthmus, or multiple re-entrant loops without a common isthmus. When two or more re-entrant circuits coexist, ablation of an individual isthmus may lead to a seamless transition (without significant changes in surface electrocardiogram, coronary sinus activation or tachycardia cycle length) to a second rhythm, and the isthmus block can go unnoticed. METHODS AND RESULTS: We hypothesize and subsequently illustrate in three patient cases, methods to rapidly identify a transition in the rhythm and isthmus block using local electrogram changes at the ablation site. CONCLUSION: Local activation sequence changes, electrogram timing, and the behaviour of pre-existing double potentials can reveal isthmus block promptly when rhythm transitions occur during ablation of multiloop re-entry tachycardias.

Novel approach to intracardiac defibrillator placement in patients with atriopulmonary Fontan: Ventricular defibrillation with an atrial positioned ICD lead.

INTRODUCTION: The Fontan procedure, used to palliate univentricular physiology, eliminates direct venous access to the ventricle and complicates implantable cardioverter-defibrillator (ICD) placement. METHODS AND RESULTS: We describe two patients with Fontan palliation who underwent a novel transvenous approach to ICD placement. The approach uses a transvenous bipolar lead placed in a coronary sinus branch for ventricular sensing, and a defibrillation lead placed in the right atrium for atrial sensing and ventricular defibrillation. CONCLUSION: Transvenous ICD implantation is possible in some patients with an atriopulmonary Fontan. This approach avoids a redo sternotomy for epicardial leads and excludes the need for lead placement in the systemic circulation.

Left atrial hypertension and the risk of early incident heart failure after atrial fibrillation ablation.

INTRODUCTION: Elevated left atrial pressure (LAP) during catheter ablation of atrial fibrillation (AF) is associated with an increased risk of AF recurrence, but it is unknown if this correlates with heart failure (HF). The objective of the study was to determine if elevated LAP after AF ablation correlates with HF events. METHODS: Prospective, single-center, cohort study measuring LAP and right atrial pressure (RAP) during AF ablation in 100 patients. The primary endpoint was clinical HF within 30 days of ablation. The secondary outcome was AF-free HF. RESULTS: One hundred patients (63% male, mean age 64.5) were enrolled and 20% had clinical HF within 30 days. Bivariate correlates included mitral valve (MV) disease, persistent AF, class III antiarrhythmics, LAP, and recurrent AF. Multivariate analysis revealed class III antiarrhythmics were protective (odds ratio [OR]: 0.24 [0.1-0.5], p = .04), while MV disease (OR: 8.7 [3.3-23], p = .03) and loop diuretics (OR: 4.8 [2.6-9.1], p = .01) were hazardous. AF-free HF occurred in 9% of patients and correlated with higher LAP and RAP, and chronic kidney disease. CONCLUSION: Patients with HF after AF ablation had higher LAP. MV disease, diuretic use, and class III antiarrhythmics also correlated to HF. These present opportunities to target future interventions to reduce a common complication of AF ablation.

Mechanism and interpretation of two-for-one response to premature atrial complexes during atrioventricular node re-entry tachycardia.

AIMS: The response to premature atrial complexes (PACs) during tachycardia has been shown to differentiate atrioventricular nodal re-entrant tachycardia (AVNRT) from focal junctional tachycardia (JT). His refractory PAC (HrPACs) perturbing the next His (resetting with fusion) is diagnostic of AVNRT and such a late PAC fusing with the native beat cannot reset the focal source of JT. Early PAC advancing the immediate His with continuation of tachycardia suggests JT but can also occur in AVNRT due to simultaneous conduction through the AV nodal fast and slow pathways [two-for-one response (TFOR)]. The objective of this study was to evaluate the incidence and mechanism of TFOR after early premature atrial complexes (ePACs) during AVNRT and to differentiate it from the known response to ePACs during JT. METHODS AND RESULTS: Typical AVNRT cases were diagnosed using standard criteria. We evaluated the responses to scanning PACs delivered during tachycardia in 100 patients undergoing AV node slow pathway modification for AVNRT. The responses to HrPACs and ePACs delivered from coronary sinus os or high right atrium were retrospectively reviewed. In 10 patients, ePACs advanced the immediate His with continuation of tachycardia. In all 10 cases, HrPACs advanced the next His, confirming AVNRT as the mechanism, and indicating a TFOR. CONCLUSION: A TFOR can occur in a small number of patients during AVNRT and is therefore not diagnostic of JT. However, HrPACs always perturbed the next His in these cases, confirming the diagnosis of AVNRT and allowing for differentiation from JT.

Predictors of successful ultrasound-guided lead implantation.

BACKGROUND: Technical advances have improved the safety of cardiac implantable electronic device (CIED) insertion, but periprocedural complications persist. Despite ultrasound (US) guidance for vascular access being feasible and exhibiting shorter fluoroscopy times, it is not widely adopted for insertion of CIEDs. Thus, we studied the use of US for CIED insertion to (1) quantify the success rate of venous cannulation, (2) identify predictors of failed cannulation, and (3) quantify the rate of complications using US guidance. METHODS: We studied 166 consecutive patients who underwent US-guided CIED implantation. Anatomic parameters of the axillary vein were measured. The primary outcome was success (group 1) or failure (group 2) to obtain vascular access utilizing US guidance. Secondary outcomes included pneumothorax and hematoma. RESULTS: Successful US-guided cannulation occurred in 154 of 166 patients (93%). No patient had a pneumothorax. Hematoma occurred in 1 of 166 patients (0.01%). Group 2 exhibited higher male proportion at 11 of 12 (92%) compared with 94 of 154 (61%) in group 1 (P = .03), increased vein depth at 3.84 versus 2.85 cm (P = .003), more right-sided implants (P = .03), higher weight at 104.6 versus 85.3 kg (P = .017), higher body mass index at 35.6 versus 29.2 kg/m2 (P = .049), and higher body surface area at 2.24 versus 1.99 m2 (P = .013). Other parameters were statistically nonsignificant. In multivariate analysis, vein depth remained significantly associated with failure. CONCLUSION: Using US guidance for CIED implantation is successful in the vast majority (93%) of patients. Rare cases of unsuccessful cannulation were associated with right-sided implants and increased venous depth.

Persistent 2-for-1 Atrioventricular Node Anterograde Conduction During a Supraventricular Tachycardia.

We present a case of persistent dual AV node conduction during AV node reentry tachycardia as a new clinical manifestation of 2-for-1 AV node conduction. The interpretation of the complex physiology ponders the possibility of an accessory pathway mediated atrioventricular reentry existing with more ventricular than atrial events.

Diagnostic utility of early premature ventricular complexes in differentiating atrioventricular reentrant and atrioventricular nodal reentrant tachycardias.

BACKGROUND: His-refractory premature ventricular complexes perturbing a supraventricular tachycardia (SVT) establish the presence of an accessory pathway (AP). Earlier premature ventricular complexes (ErPVCs) may perturb SVTs but are considered nondiagnostic. OBJECTIVE: The purpose of this study was to test the hypothesis that an ErPVC will always show a difference >35 ms in its advancement of the next atrial activation during atrioventricular nodal reentrant tachycardia (AVNRT). During atrioventricular reentrant tachycardia (AVRT), a PVC delivered close to the circuit can result in greater advancement of atrial activation due to retrograde conduction via an AP. Thus, an AP response, defined as ErPVC (H1S2) advancing the subsequent atrial activation (A1-A2) more than this minimum difference (A1A2 ≤ H1S2+35 ms), establishes the presence of an AP. METHODS: Sixty-five consecutive patients with SVT were retrospectively evaluated. ErPVCs were defined when the ventricular pacing stimulus was >35 ms ahead of the His during tachycardia. RESULTS: Among the 65 cases, 43 were AVNRT and 22 AVRT. Fourteen AVRT cases had an AP response with a mean H1S2+35 ms of 336 ± 58 ms and A1A2 of 309 ± 51ms. No AVNRT cases had an AP response. The specificity of an AP response to ErPVC in predicting AVRT was 100%. CONCLUSION: An AP response to PVCs (A1A2 ≤ H1S2+35 ms) is 100% specific for the presence of an AP.

Differentiating Atrioventricular Reentry Tachycardia and Atrioventricular Node Reentry Tachycardia Using Premature His Bundle Complexes.

BACKGROUND: Current maneuvers for differentiation of atrioventricular node reentry tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) lack sensitivity and specificity for AVRT circuits located away from the site of pacing. We hypothesized that a premature His complex (PHC) will always perturb AVRT because the His bundle is obligatory to the circuit. Further, AVNRT could not be perturbed by a late PHC (≤20 ms ahead of the His) due to the retrograde His conduction time. Earlier PHCs can advance the AVNRT circuit but only by a quantity less than the prematurity of the PHC. METHODS: High-output pacing at the distal His location delivered PHCs. AVRT was predicted when late PHCs perturbed tachycardia or when earlier PHCs led to atrial advancement by an amount equal or greater than the degree of PHC prematurity. RESULTS: Among the 73 supraventricular tachycardias, the test accurately predicted AVRT (n=29) and AVNRT (n=44) in all cases. Late PHC advanced the circuit in all 29 AVRTs and none of the AVNRTs (sensitivity and specificity, 100%). With earlier PHCs, the degree of atrial advancement was equal or greater than the PHC prematurity in 26/29 AVRTs and none of the AVNRTs (90% sensitivity and 100% specificity). The mean prematurity of the PHC required to perturb AVNRT was 48 ms (range, 28-70 ms) and the advancement less than the prematurity of the PHC (mean, 32 ms; range, 18-54 ms). CONCLUSIONS: The responses to PHCs distinguished AVRT and AVNRT with 100% specificity and sensitivity.

Avoiding Bladder Catheters During Atrial Fibrillation Ablation.

OBJECTIVES: This study sought to determine if atrial fibrillation (AF) ablation can be performed safely without bladder catheterization. BACKGROUND: Patients undergoing AF ablation often receive bladder catheters. Catheterization is associated with potential complications. The ABCD-AF (Avoiding Bladder Catheters During Atrial Fibrillation) ablation study evaluates the advantages of performing AF ablation without routine catheterization. METHODS: In this single-center, prospective, randomized controlled trial, 80 patients received bladder catheterization (group A), and 80 patients received only as-needed catheterization (group B). The primary endpoint was a composite of cystitis, urethral injury, hematuria, dysuria, or urinary retention. RESULTS: The mean patient age was 63 ± 13 years, and 33% of patients were female. The primary outcome was reached in 45 patients in group A and 11 patients in group B (p < 0.001). Urinary tract infection occurred in 7 patients in group A and 2 patients in group B (p = 0.17). Urinary retention occurred in 12 patients in group A and 5 patients in group B (p = 0.07). Randomization to catheterization carried an odds ratio of 8.1 (95% confidence interval [CI]: 3.7 to 17.5; p < 0.001), and male sex carried an odds ratio of 3.8 (95% CI: 1.7 to 8.6; p = 0.001) for the primary endpoint. On subgroup analysis, randomization to undergo catheterization had no association with the primary outcome in female patients but had an odds ratio of 14.6 (95% CI: 5.6 to 38.1; p < 0.001) in male patients. In multivariable analysis, sex and catheter status remained independently associated with the primary outcome. CONCLUSIONS: Bladder catheterization can be safely avoided in patients undergoing AF ablation and is associated with a significant reduction in adverse outcomes, especially in men.

Mammary tumor induction in transgenic mice expressing an RNA-binding protein.

We have analyzed mammary tumors arising in transgenic mice expressing a novel, multifunctional RNA-binding protein. The protein, which we call the c-myc mRNA coding region instability determinant binding protein (CRD-BP), binds to c-myc, insulin-like growth factor II, and beta-actin mRNAs, and to H19 RNA. Depending on the RNA substrate, the CRD-BP affects RNA localization, translation, or stability. CRD-BP levels are high during fetal development but low or undetectable in normal adult tissues. The CRD-BP is linked to tumorigenesis, because its expression is reactivated in some adult human breast, colon, and lung tumors. These data suggest the CRD-BP is a proto-oncogene. To test this idea, the CRD-BP was expressed from the whey acidic protein (WAP) promoter in mammary epithelial cells of adult transgenic mice. The incidence of mammary tumors was 95% and 60% in two lines of WAP-CRD-BP mice with high and low relative CRD-BP expression, respectively. Some of the tumors metastasized. Nontransgenic mice did not develop mammary tumors. H19 RNA and insulin-like growth factor II mRNA were up-regulated significantly in non-neoplastic WAP-CRD-BP mammary tissue. WAP-CRD-BP mice are a novel model for mammary neoplasia and might provide insights into human breast cancer biology.