Non-invasive electroanatomic mapping to reduce mapping time during catheter ablation of outflow tract ventricular premature depolarizations.

PURPOSE: Ventricular premature depolarizations (VPD) commonly arise from the septal anterior right ventricular outflow tract (sRVOT), the left coronary cusp (LCC), and the distal great cardiac vein (dGCV), and share common ECG characteristics. To assess the diagnostic accuracy of non-invasive electroanatomic mapping (NIEAM) in differentiating VPD origin between sRVOT, LCC and dGCV and quantify its clinical utility in eliminating unnecessary mapping and ablation. METHODS: ECGs and NIEAMs (CardioInsight, Medtronic) from 32 patients (56.3 ± 15.2 years) undergoing ablation for VPDs originating from sRVOT, LCC, or dGCV were blindly reviewed for their diagnostic accuracy in predicting the SOO. A 2-step algorithm using NIEAM-based activation timing of the superior basal septum of < 22.5 ms and lateral mitral annulus of > 60.5 ms was compared with subjective ECG evaluation, the maximum deflection index (MDI), and the V2 transitional ratio in predicting SOO. We calculated the mapping and ablation time that could have been avoided had the operators relied on activation timing by NIEAM in designing their mapping and ablation strategy. RESULTS: NIEAM was superior to subjective ECG evaluation, MDI, and V2 transition ratio in predicting the SOO yielding a sensitivity and specificity of 96.9% and 98.4% respectively. Using NIEAM in determining the SOO would have obviated 22 ± 4.5 min of mapping in the wrong chamber and prevented unnecessary ablation of 4.5 ± 1.8 min. CONCLUSION: NIEAM has high diagnostic accuracy in differentiating between sRVOT, LCC, and dGCV VPDs, and can significantly reduce mapping time, obviating the need for unnecessary access and ablation.

Anatomic predictors of recurrence after cryoablation for atrial fibrillation: a computed tomography based composite score.

BACKGROUND: Effective pulmonary vein isolation (PVI) with cryoablation depends on adequate occlusion of pulmonary veins (PV) by the cryoballoon and is therefore likely to be affected by PV and left atrial (LA) anatomical characteristics and variants. Thus, the objective of this study was to investigate the effect of LA and PV anatomy, evaluated by computed tomography (CT), on acute and long-term outcomes of cryoablation for atrial fibrillation (AF). METHODS: Fifty-eight patients (64.72 + 9.44 years, 60.3% male) undergoing cryoablation for paroxysmal or early persistent AF were included. Pre-procedural CT images were analyzed to evaluate LA dimensions and PV anatomical characteristics. Predictors of recurrence were identified using regression analysis. RESULTS: 60.3% of patients had two PVs on each side with separate ostia, whereas 29.3% and 10.3% had right middle and left common PVs, respectively. The following anatomic characteristics were found to be independent predictors of recurrence: right superior PV ostial max:min diameter ratio > 1.32, left superior PV ostial max:min diameter ratio > 1.2, right superior PV antral circumference > 69.1 mm, right inferior PV antral circumference > 61.38 mm, right superior PV angle > 22.7°. Using these factors, LA diameter and right middle PV, a scoring model was created for prediction of "unfavorable" LA-PV anatomy (AUC = 0.867, p = 0.000009, score range = 0-7). Score of ≥ 4 predicted need for longer cryoenergy ablation (p = 0.039) and more frequent switch to radiofrequency energy (p = 0.066) to achieve PVI, and had a sensitivity of 83.3% and specificity of 82.5% to predict clinical recurrence. CONCLUSION: CT-based scoring system is useful to identify "unfavorable" anatomy prior to cryo-PVI, which can result in procedural difficulty and poor outcomes.

Early recurrence of atrial fibrillation after pulmonary vein isolation: a comparative analysis between cryogenic and contact force radiofrequency ablation.

BACKGROUND: Early recurrence (ER) of atrial fibrillation (AF) within 90 days post-ablation is observed in up to 50% of patients and has been attributed to transient inflammation. The importance of ER in current era of pulmonary vein isolation (PVI) with cryoballoon ablation (CBA) and contact-force catheter radiofrequency ablation (cfRFA) has not been clearly reported. In addition, it is not known whether there are differences between types of ablation energy used during PVI. METHODS: Study population was drawn from a prospective multicenter database of AF ablation. Consecutive patients undergoing first-time ablation with PVI alone, using either second-generation CBA or cfRFA catheters were included. Patients were followed at 0.5, 3, 6, and 12 months to assess recurrence. Predictors of late recurrence (LR), defined as recurrence outside the blanking period, were assessed by Cox proportional hazards regression models. Freedom from LR was calculated and compared between two groups using the Kaplan-Meier method and log-rank test. RESULTS: Study cohort included 300 patients (1:1 CBA:RFA, age 63.6 ± 10.3 years, 67% male). There were no baseline characteristic differences between the CBA and cfRFA groups. ER occurred in 23.3% and 16.7% of patients in the CBA and cfRFA groups, respectively (p = 0.149). One-year freedom from LR was similar for both groups (72.7% CBA vs. 78% cfRFA, p = 0.287). Fifty-two patients (25 CBA and 27 cfRFA) underwent repeat ablation and no difference in durability of PVI was found. ER was the only common independent predictor of LR for either group and for the entire cohort (HR 2.3). CONCLUSIONS: In our series of AF ablation using second-generation cryoballoon and contact-force RFA catheters, recurrence in the "blanking period" is seen in 20% and remains predictive of late recurrence irrespective of the energy used.

Conduction patterns of idiopathic arrhythmias from the endocardium and epicardium of outflow tracts: New insights with noninvasive electroanatomic mapping.

BACKGROUND: Idiopathic arrhythmias commonly arise from the septal right ventricular outflow tract (RVOT), sinuses of Valsalva (SoV), and great cardiac vein (GCV). Predicting the exact site of origin is important for preparation for catheter ablation. OBJECTIVE: The purpose of this study was to examine the diagnostic value of noninvasive electroanatomic mapping (NIEAM) to differentiate between septal RVOT, SoV, and GCV origin and compare it to that of 12-lead electrocardiography (ECG). METHODS: NIEAM maps (CardioInsight, Medtronic) were generated during spontaneous ventricular premature depolarizations (VPDs) and threshold pacing from septal RVOT, SoV, and GCV. Origin prediction using NIEAM was compared to algorithmic ECG criteria (maximal deflection index; V2 transition ratio) and subjective ECG evaluation. RESULTS: Sixty NIEAMs (18 spontaneous VPDs and 42 pace-maps) from 31 patients (age 56 ± 16 years) were analyzed. NIEAM showed distinct conduction patterns, best visualized at the base of the heart: septal RVOT VPDs propagate toward the tricuspid annulus, depolarizing the septum from inferior to superior; SoV VPDs engage the superior septum early; and GCV VPDs move laterally along the mitral annulus, depolarizing the heart from left to right. Activation of the lateral mitral annulus >60.50 ms and the superior basal septum <22.5 ms from onset predicts RVOT and SoV origin, respectively, in 100% of cases. NIEAM was superior to maximum deflection index in predicting GCV origin (100% vs 42.2% accuracy) and superior to V2 transition ratio in predicting SoV origin (100% vs 75.9% accuracy). CONCLUSION: Arrhythmias arising from the outflow tracts follow distinct propagation patterns depending on the origin. A 2-step algorithm using activation timing by NIEAM yields 100% diagnostic accuracy in predicting origin.

Use of a lateral infraclavicular puncture to obtain proximal venous access with occluded subclavian/axillary venous systems for cardiac rhythm devices.

BACKGROUND: Venous occlusion is not uncommon and total venous obstruction with more proximal patency may occur in as many as 10% of previous implants. Many techniques are available to obtain ipsilateral access; however, most require special equipment or skills. We describe a technique of infraclavicular cannulation of the brachiocephalic vein ipsilateral to the occlusion that is safe and feasible for most implanters. METHODS: Fourteen patients with subclavian/axillary occlusions ipsilateral to the implanted device and requiring revision or upgrade of their system or venous occlusion with contraindication to implant on the contralateral side underwent lead addition/placement via a brachiocephalic approach. Following venography, an 18-gauge needle was used to gain brachiocephalic access. The needle was initially positioned in a lateral infraclavicular location. The needle was then advanced under the clavicle in a horizontal plane and advanced toward the sternal notch under fluoroscopic guidance. RESULTS: Fourteen patients underwent an attempt at brachiocephalic access. Cannulation of the brachiocephalic was possible in all 14 and lead(s) were successfully implanted in all. There were no complications with the procedure, specifically no pneumothoraces. In follow-up (mean 36 months, range 1-86 months), all implanted leads function well, with no evidence of lead failure or impedance changes. CONCLUSION: A lateral infraclavicular approach is a safe and effective technique for obtaining brachiocephalic access when the subclavian/axillary vein is occluded. This technique is easy to learn and may be useful for implanters without the equipment or skills needed for lead extraction or microdissection or in cases where patients refuse these procedures.

Right-sided implantation and subpectoral position are predisposing factors for fracture of a 6.6 French ICD lead.

BACKGROUND: The Medtronic Sprint Fidelis (Medtronic Inc., Minneapolis, MN, USA) lead family is associated with an unacceptable incidence of premature lead failure. There are limited data on risk factors for lead fracture. We hypothesized that factors leading to potential increased forces on the lead related to device implantation or technique may be associated with premature lead failure. METHODS: We reviewed the implant data from our group and identified 176 patients who received active fixation Medtronic Fidelis (Model 6931, single coil and Model 6949, dual coil) leads. Implant data, including age, sex, venous access site, implant side, implant location, and number of venous leads were reviewed. Hospital, pacemaker clinic, and Medtronic registration databases were reviewed for evidence of lead failure, replacement, or abandonment. Data was evaluated in univariate and multivariate regression analyses. RESULTS: Of the 176 leads implanted, 10 (5.7%) were noted to develop malfunction. This presented as inappropriate shocks from sensed noise or elevated impedance measurements. Of the above noted implant features, only right-sided (vs left-sided) implant (hazard ratio [HR] 18.8, 95% confidence intervals [CI] 3.8, 93.3), and subpectoral implant (vs prepectoral; HR 14.31, 95% CI 3.2, 64.0) were predictive of lead failure in maximally adjusted models. CONCLUSIONS: We have identified both right-sided implantation and subpectoral generator positioning as factors associated with premature lead malfunction in Fidelis active fixation leads. Clinical decisions regarding patient management should incorporate these findings in regard to lead replacement in high-risk patients.

Clinical comparison of ICD detection algorithms that include rapid-VT zones.

INTRODUCTION: The safe use of antitachycardia pacing (ATP) to terminate rapid ventricular tachycardias (VTs) (cycle length 240-320 ms) is predicated on the ability of implantable cardioverter defibrillators (ICDs) to distinguish rapid VT from ventricular fibrillation (VF). We set out to compare the time to device charging following the induction of VF of various ICD multizone detection algorithms for rapid VT/VF discrimination. METHODS AND RESULTS: Data on the time to device charging following the induction of VF at the time to device implantation were collected on 62 consecutive patients in a nonrandomized prospective cohort fashion. Multizone programming for the Boston Scientific, Medtronic, and St. Jude Medical devices was based on prior clinically validated data. Sixty-two subjects were studied (Boston Scientific = 16, Medtronic = 27, St. Jude Medical = 19) and 124 tests for VF detection were performed (Boston Scientific = 32, Medtronic = 54, St. Jude Medical = 38). Mean time to charging was significantly prolonged in the Boston Scientific group as was the percentage of tests where charge initiation occurred >5 seconds from VF-induction: 4.24, 3.99, and 3.00 seconds and 19%, 4%, and 0% for the Boston Scientific, Medtronic, and St. Jude Medical groups, respectively, P < 0.05. ATP was the first therapy administered in 9.4% of tests in the Boston Scientific group. CONCLUSION: The Boston Scientific multizone VT/VF discrimination algorithm results in a prolonged time to VF detection, and consequently, prolonged time to appropriate initiation of device charging. Further studies are needed to determine whether prolonged detection times lead to clinically significant events.

Meta-analysis to assess the appropriate endpoint for slow pathway ablation of atrioventricular nodal reentrant tachycardia.

BACKGROUND: There are little data on the appropriate endpoint for slow pathway ablation that balances acceptable procedural times, recurrence rates, and complication rates. This study compared recurrence rates of three commonly utilized endpoints of slow pathway ablation for atrioventricular nodal reentrant tachycardia (AVNRT). METHODS: We performed a meta-analysis of AVNRT slow pathway ablation cohorts by searching electronic databases, the Internet, and conference proceedings. Inclusion criteria were age >18 years, >20 human subjects per study, primary AVNRT ablation, English language publication, and >1 month of follow-up. Data were analyzed with a fixed-effects model using Comprehensive Meta-Analysis software version 2.2.046 (Biostat, Englewood, NJ, USA). RESULTS: We included 10 studies encompassing 1,204 patients with a mean age of 41-53 years. Endpoints were complete slow pathway ablation, residual jump only, and single remaining echo beat. Pooled estimates revealed 28 of 641 patients (4.4%) with complete slow pathway ablation, 13 of 192 patients (6.8%) with a residual jump only, and 24 of 371 patients (6.5%) with one echo had recurrences. With uniform isoproterenol use after ablation, there was no significant difference in recurrence rates among the endpoints. However, when isoproterenol was utilized after ablation only if needed to induce AVNRT before ablation, a significantly higher recurrence rate occurred in patients with a residual jump (P = 0.002), a single echo (P = 0.003), or the combined group of a residual jump and/or one echo (P = 0.001). CONCLUSIONS: Isoproterenol should be used routinely after slow pathway modification, when a residual jump and/or single echo remain.

Standardization and validation of an automated algorithm to identify fractionation as a guide for atrial fibrillation ablation.

BACKGROUND: Atrial fibrillation catheter ablation is frequently guided by identification of fractionated electrograms, which are thought to be critical for maintenance of the arrhythmia. Objective automated means for identifying fractionation independent of physician interpretation have not been standardized or validated. OBJECTIVE: The purpose of this study was to standardize and validate an automated algorithm to rapidly identify fractionated electrograms for high-density atrial fibrillation fractionation mapping. METHODS: Left and right atrial fractionation maps were generated by EnSite NavX 6.0 software, using standardized ablation catheters in eight patients with atrial fibrillation. Two blinded electrophysiologists interpreted all electrograms as either fractionated or not fractionated. A stepwise approach was used to optimize automated settings to accurately identify fractionation. High-density fractionation maps were generated with a 20-pole mapping catheter in eight other patients. Two blinded electrophysiologists interpreted all electrograms as near field or far field. The algorithm was refined to optimize settings to exclude far-field signals and retain near-field signals. The sampling segment length was adjusted to optimize recording time to ensure reproducibility. RESULTS: Using 1,514 points, the automated software achieved sensitivity of 0.75 and specificity of 0.80 for identification of fractionated electrograms. Using 725 points collected via multipole catheters with optimal automated settings, 94% of near-field fractionated electrograms were accurately identified. A 6-second sampling length was needed for reproducible fractionation measurements. CONCLUSION: Standardized settings of EnSite NavX 6.0 software with 6-second data collection per point can rapidly and accurately generate high-density fractionation maps independent of physician electrogram interpretation. This may allow for an automated, standardized approach to atrial fibrillation fractionated ablation.

Evaluation of the abdominal aorta and the renal arteries with an intracardiac echocardiography probe placed in the inferior vena cava: a feasibility study.

BACKGROUND: Ultrasound evaluation of the abdominal aorta and its branches is usually performed transabdominally. Not infrequently, the image quality is suboptimal. Recently, an intracardiac echocardiography probe has become commercially available. These probes are usually inserted intravenously and advanced to the right heart for diagnostic and monitoring purposes during procedures such as atrial septal defect closure and pulmonary vein isolation. Because of the close anatomic relation between the abdominal aorta and the inferior vena cava, we hypothesized that these probes would be useful in the evaluation of the abdominal aorta and the renal arteries. METHODS: Sixteen patients with normal renal function and no history of hypertension who were undergoing a pulmonary vein isolation procedure or atrial septal defect closure were studied. In each patient, the intracardiac echocardiography probe was inserted in the femoral vein and advanced to the right atrium for the evaluation of the left atrium and the pulmonary veins during the procedure. At the end of the therapeutic procedure, the probe was withdrawn into the inferior vena cava for the evaluation of the aorta and renal arteries. RESULTS: High-resolution images of the abdominal aorta from the diaphragm to its bifurcation were easily obtained in all patients. These images allowed for the evaluation of arterial size, shape, and blood flow. Both renal arteries were easily visualized in each patient. With the probe in the inferior vena cava, both renal arteries were parallel to the imaging plane and, therefore, accurate measurement of renal blood flow velocity and individual renal blood flow were measured.

Percutaneous treatment of the superior vena cava syndrome via an excimer laser sheath in a patient with a single chamber atrial pacemaker.

A 21-year-old woman presented with a pacemaker-associated superior vena cava (SVC) syndrome refractory to medical therapy. In the past, treatment of this condition has involved surgical exploration which is invasive. With the evolution of percutaneous techniques, treatment has included venoplasty and stenting over the pacemaker lead. There is limited experience with a more advanced percutaneous technique in which the lead is extracted by an excimer laser sheath. The extraction is immediately followed by venoplasty and stenting at the site of stenosis with subsequent implantation of a new permanent pacemaker at the previously occluded access site. The patient underwent this procedure which proved to be safe, minimally invasive, and an efficient method of treating SVC syndrome secondary to a single chamber atrial pacemaker.

Why a sawtooth? Inferences on the generation of the flutter wave during typical atrial flutter drawn from radiofrequency ablation.

BACKGROUND: Typical atrial flutter (AFL) is a macroreentrant arrhythmia characterized by a counterclockwise circuit that passes through the cavotricuspid isthmus with passive depolarization of the left atrium. These electrical events are thought to be responsible for the classic "sawtooth" wave of atrial flutter seen on the surface electrocardiogram characterized by a gradual downward deflection followed by a sharp negative deflection. It has been suggested that the negative flutter wave is a result of passive depolarization of the left atrium. We hypothesized that interruption of the circuit within the isthmus would prevent the reentrant wave from depolarizing the left atrium thus eliminating the component of the electrocardiogram reflecting left atrial depolarization. METHODS: We examined 100 cases of atrial flutter with the typical "sawtooth" pattern referred for radiofrequency ablation. Ninety-seven of the 100 were successfully ablated. All cases were reviewed for termination of atrial flutter with the last intracardiac electrogram just lateral to the site of linear ablation and surface flutter wave at the moment of termination not obscured by the QRS segment or the T-wave. Seventeen of the 97 met these criteria. RESULTS: Seventeen of the 17 cases demonstrated a gradual negative deflection as the last discernible wave of atrial activity followed by an isoelectric period and resumption of normal sinus rhythm. The last generated wave lacked the sharp negative downstroke. CONCLUSION: These results suggest that the sharp negative deflection of flutter waves likely correlates with the wavefront's penetration of the interatrial septum and passive depolarization of the left atrium.

Cardiac vein angioplasty for biventricular pacing.

Biventricular pacing for the treatment of congestive heart failure has consistently demonstrated improvement in quality-of-life and reduction in heart failure symptoms. Though the over-the-wire systems will be helpful in overcoming many existing obstacles to optimal lead placement, anatomic variability will still limit overall success. Cardiac vein angioplasty may be required for deployment of leads into tortuous or obstructed cardiac veins. This case report describes the angioplasty of a focal cardiac vein stenosis allowing for successful implantation of a left ventricular pacing lead. The safety of this procedure is unknown, though the risks may be acceptable in certain patients.