His bundle pacing insights from electroanatomical mapping: Topography and pacing targets.

OBJECTIVES: To characterize 3D electroanatomical mapping (EAM) of the His bundle (HB) region. BACKGROUND: Visualization of selective (S) and nonselective (NS) HB capture areas by EAM has not been described and may help guide HB pacing (HBP). METHODS: EAM was performed via NavX system in 17 patients (pts) undergoing HBP. HB cloud, S-HB, NS-HB, and right bundle (RB) capture areas were mapped. RESULTS: S-HBP areas were identified in 11, NS-HBP in 14, and RB in 11 pts. Two NS-HBP areas (upper and lower) either separated by S-HBP (8 pts) or almost contiguous (5 pts) were observed. S-HBP area measured: 1.1 ± 0.9 cm2 , NS upper: -1.2 ± 0.9 cm2 , NS lower: -1.2 ± 0.9 cm2 , RB: -1.7 ± 1.3 cm2 , total His cloud: -4.1 ± 2.7 cm2 . Electrocardiogram (ECG) pacemaps were different between upper and lower NS-HBP areas in 13/14 pts (p = .006). ECG differences between NS clouds were present in inferior leads in 9 pts (more negative QRS complex from lower NS area) and in precordial leads in 5 pts. There was no correlation between HBP lead location and capture threshold. R-wave amplitude was higher at more distal locations on HB cloud (p = .02). CONCLUSION: (1) Pacemapping identifies distinct regions that may correspond to HB anatomy. (2) A linear S-HBP area is typically surrounded by two separate NS areas. (3) Pace-map ECGs from upper and lower NS-HBP areas have different morphologies. (4) These EAM features and pace-mapping may be helpful to the implanter.

Synergy between sacubitril and valsartan leads to hemodynamic, antifibrotic, and exercise tolerance benefits in rats with preexisting heart failure.

Simultaneous neprilysin inhibition (NEPi) and angiotensin receptor blockade (ARB) with sacubitril/valsartan improves cardiac function and exercise tolerance in patients with heart failure. However, it is not known whether these therapeutic benefits are primarily due to NEPi with sacubitril or ARB with valsartan or their combination. Therefore, the aim of the present study was to investigate the potential contribution of sacubitril and valsartan to the benefits of the combination therapy on left ventricular (LV) function and exercise tolerance. Heart failure was induced by volume overload via partial disruption of the aortic valve in rats. Therapy began 4 wk after valve disruption and lasted through 8 wk. Drugs were administered daily via oral gavage [sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), and sacubitril (31 mg/kg)]. Hemodynamic assessments were conducted using Millar technology, and an exercise tolerance test was conducted using a rodent treadmill. Therapy with sacubitril/valsartan improved load-dependent indexes of LV contractility (dP/d tmax) and relaxation (dP/d tmin), exercise tolerance, and mitigated myocardial fibrosis, whereas monotherapies with valsartan, or sacubitril did not. Both sacubitril/valsartan and valsartan similarly improved a load-independent index of contractility [slope of the end-systolic pressure-volume relationship ( Ees)]. Sacubitril did not improve Ees. First, synergy of NEPi with sacubitril and ARB with valsartan leads to the improvement of load-dependent LV contractility and relaxation, exercise tolerance, and reduction of myocardial collagen content. Second, the improvement in load-independent LV contractility with sacubitril/valsartan appears to be solely due to ARB with valsartan constituent. NEW & NOTEWORTHY Our data suggest the following explanation for the effects of sacubitril/valsartan: 1) synergy of sacubitril and valsartan leads to the improvement of load-dependent left ventricular contractility and relaxation, exercise tolerance, and reduction of myocardial fibrosis and 2) improvement in load-independent left ventricular contractility is solely due to the valsartan constituent. The findings offer a better understanding of the outcomes observed in clinical studies and might facilitate the continuing development of the next generations of angiotensin receptor neprilysin inhibitors.

Interaction Between Sacubitril and Valsartan in Preventing Heart Failure Induced by Aortic Valve Insufficiency in Rats.

BACKGROUND: Synergistic interactions between neprilysin inhibition (NEPi) with sacubitril and angiotensin receptor type1 blockade (ARB) with valsartan have been implicated in improvement of left ventricular (LV) contractility, relaxation, exercise tolerance, and fibrosis in preexisting heart failure (HF) induced by aortic valve insufficiency (AVI). It is not known whether this pharmacologic synergy can prevent cardiovascular pathology in a similar AVI model. Our aim was to investigate the pharmacology of sacubitril/valsartan in an experimental setting with therapy beginning immediately after creation of AVI. METHODS: HF was induced through partial disruption of the aortic valve in rats. Therapy began 3 hours after valve disruption and lasted 8 weeks. Sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), sacubitril (31 mg/kg), or vehicle were administered daily via oral gavage (N=8 in each group). Hemodynamic assessments were conducted using Millar technology, and an exercise tolerance test was conducted using a rodent treadmill. RESULTS: Only sacubitril/valsartan increased total arterial compliance and ejection fraction (EF). Therapies with sacubitril/valsartan and valsartan similarly improved load-dependent (dP/dtmax) and load independent indices (Ees) of LV contractility, and exercise tolerance, whereas sacubitril did not. None of the therapies improved LV relaxation (dP/dtmin), whereas all reduced myocardial fibrosis. CONCLUSIONS: 1) The synergistic interaction between NEPi and ARB in early therapy with sacubitril/valsartan leads to increased total arterial compliance and EF. 2) Improvement in indices of LV contractility, and exercise tolerance with sacubitril/valsartan is likely because of ARB effect of valsartan. 3) All three therapies provided antifibrotic effects, suggesting both ARB and NEPi are capable of reducing myocardial fibrosis.

A Novel Paradigm for Sacubitril/Valsartan: Beta-Endorphin Elevation as a Contributor to Exercise Tolerance Improvement in Rats With Preexisting Heart Failure Induced by Pressure Overload.

BACKGROUND: Simultaneous angiotensin receptor (AT1) blockade and neprilysin inhibition with the use of sacubitril/valsartan has been recently approved to treat patients with heart failure (HF). Therapeutic benefits of this therapy have been attributed to natriuretic peptide elevation and AT1 receptor blockade. However, that pharmacologic picture may not be complete. The aims of this study were to investigate the pharmacology of sacubitril/valsartan compared with sacubitril and valsartan alone and to examine their impact on peptides up-regulated by neprilysin inhibition, such as beta-endorphin. METHODS AND RESULTS: An HF model was induced by pressure overload via constriction of the suprarenal abdominal aorta in rats. Sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), sacubitril (31 mg/kg), or placebo was administered by daily oral gavage (starting 4 weeks after pressure overload onset and continued for 4 additional weeks; n = 8 in each group). Exercise tolerance testing was conducted using a rodent treadmill and hemodynamic assessments were conducted under anesthesia with the use of Millar left ventricular (LV) conductance technology. Pressure overload led to exercise intolerance by 4 weeks and to hypertension and LV dysfunction and remodeling by 8 weeks. Both sacubitril/valsartan and sacubitril elevated beta-endorphin levels, by 40% and 54%, respectively, and improved exercise tolerance, by 93% and 112%, whereas valsartan did not. Indices of LV dysfunction persisted with the use of sacubitril/valsartan and valsartan therapies and even deteriorated in sacubitril group. CONCLUSIONS: When added to valsartan, sacubitril increases beta-endorphin concentrations and improves exercise tolerance. These data suggest beta-endorphin elevation as a potential mechanism of action leading to improvement in exercise tolerance that is seen with sacubitril/valsartan. This therapeutic benefit is potentially independent from LV function.

Clinical Implications of Brief Device-Detected Atrial Tachyarrhythmias in a Cardiac Rhythm Management Device Population: Results from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes.

BACKGROUND: The RATE Registry (Registry of Atrial Tachycardia and Atrial Fibrillation Episodes) is a prospective, outcomes-oriented registry designed to document the prevalence of atrial tachycardia and/or fibrillation (AT/AF) of any duration in patients with pacemakers and implantable cardioverter defibrillators (ICDs) and evaluate associations between rigorously adjudicated AT/AF and predefined clinical events, including stroke. The appropriate clinical response to brief episodes of AT/AF remains unclear. METHODS: Rigorously adjudicated electrogram (EGM) data were correlated with adjudicated clinical events with logistic regression and Cox models. Long episodes of AT/AF were defined as episodes in which the onset and/or offset of AT/AF was not present within a single EGM recording. Short episodes of AT/AF were defined as episodes in which both the onset and offset of AT/AF were present within a single EGM recording. RESULTS: We enrolled 5379 patients with pacemakers (N=3141) or ICDs (N=2238) at 225 US sites (median follow-up 22.9 months). There were 359 deaths. There were 478 hospitalizations among 342 patients for clinical events. We adjudicated 37 531 EGMs; 50% of patients had at least one episode of AT/AF. Patients with clinical events were more likely than those without to have long AT/AF (31.9% vs. 22.1% for pacemaker patients and 28.7% vs. 20.2% for ICD patients; P<0.05 for both groups). Only short episodes of AT/AF were documented in 9% of pacemaker patients and 16% of ICD patients. Patients with clinical events were no more likely than those without to have short AT/AF (5.1% vs. 7.9% for pacemaker patients and 11.5% vs. 10.4% for ICD patients; P=0.21 and 0.66, respectively). CONCLUSIONS: In the RATE Registry, rigorously adjudicated short episodes of AT/AF, as defined, were not associated with increased risk of clinical events compared with patients without documented AT/AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00837798.

Long-Term Evaluation of Biotronik Linox and Linox(smart) Implantable Cardioverter Defibrillator Leads.

INTRODUCTION: Expert consensus holds that post-market, systematic surveillance of ICD leads is essential to ensure confirmation of adequate lead performance. GALAXY (NCT00836589) and CELESTIAL (NCT00810264) are ongoing multicenter, prospective, non-randomized registries conducted to confirm the long-term safety and reliability of Biotronik leads. METHODS AND RESULTS: ICD and CRT-D patients are followed for Linox and Linox(smart) ICD lead performance and safety for 5 years post-implant. All procedural and system-related adverse events (AEs) were assessed at each follow-up, along with lead electrical parameters. An independent CEC of EPs adjudicated AEs to determine AE category and lead relatedness. The analysis used categories of lead observations per ISO 5841-2 (Third edition). A total of 3,933 leads were implanted in 3,840 patients (73.0% male, mean age 67.0 ± 12.2 years) at 146 US centers. The estimated cumulative survival probability was 96.3% at 5 years after implant for Linox leads and 96.6% at 4 years after implant for Linox(smart) leads. A comparison of the Linox and Linox(smart) survival functions did not find evidence of a difference (P = 0.2155). The most common AEs were oversensing (23, 0.58%), conductor fracture (14, 0.36%), failure to capture (13, 0.33%), lead dislodgement (12, 0.31%), insulation breach (10, 0.25%), and abnormal pacing impedance (8, 0.20%). CONCLUSIONS: Linox and Linox(smart) ICD leads are safe, reliable and infrequently associated with lead-related AEs. Additionally, estimated cumulative survival probability is clinically acceptable and well within industry standards. Ongoing data collection will confirm the longer-term safety and performance of the Linox family of ICD leads.

Tidal volume and minute ventilation parameters derived from pacemaker impedance measurements can predict experimental heart failure development.

BACKGROUND: Specific respiratory patterns and periodic breathing have been associated with heart failure. Less is known regarding changes in tidal volume (TV) and minute ventilation (MV) as a result of early heart failure (HF) decompensation. METHODS AND RESULTS: Twelve adult Yucatan minipigs were implanted with a biventricular pacemaker and a left ventricular pressure sensor. HF was induced using high-rate pacing at 240 paces per minute for 2-4 weeks, followed by 2 weeks of recovery. Left ventricular pressure measurements and weekly echocardiograms verified the development of HF. The right and left ventricular intrathoracic impedance (RVITI and LVITI, respectively) signals were used to determine the respiratory parameters of rate, TV, and MV. Compared to baseline (BL), during HF, the TV dropped 68% for RVITI and 61% for LVITI (P < 0.0001 for both). Correspondingly, MV dropped 34% for RVITI and 27% for LVITI (P < 0.0001 for both). The daily medians of the respiratory rate (RR) and the longest breath interval (LBI) did not change significantly from BL to HF and recovery. However, circadian variation of the RR and the LBI became blunted during HF development. All derived respiratory parameters showed the reverse trend during the recovery period. CONCLUSION: TV and MV change independently from the RR in early HF decompensation. Tracking the changes of TV and MV with an implantable device may provide an additional method for early HF detection and assessment of the response to therapy.

Do baseline diastolic echocardiographic parameters predict outcome after resynchronization therapy? Results from the PROSPECT trial.

INTRODUCTION: Cardiac resynchronization therapy (CRT) can improve clinical and cardiac structural status in heart failure patients. The role of baseline diastolic echocardiographic parameters to characterize the likelihood of positive outcomes is not well known. We explored relationships between diastolic parameters and outcomes 6 months after CRT implant in the Predictors of Response to CRT (PROSPECT) Trial. HYPOTHESIS: We hypothesized that diastolic echocardiographic parameters were associated with clinical and structural outcomes in CRT patients. METHODS: For 426 patients in PROSPECT, a prospective observational trial of CRT, baseline E/A ratio, left atrial (LA) area, isovolumic relaxation time, left ventricular inflow deceleration time, E' velocity, and E/E' ratio were evaluated and related to 6-month clinical composite score (CCS) and left ventricular end-systolic volume (LVESV) reduction using Spearman rank-order correlations. Parameters associated with outcomes were analyzed further by discrete categorization. RESULTS: As continuous variables, only E/A ratio and LA area correlated with CCSs (P = 0.017, P = 0.045, respectively) and relative change in LVESV at 6 months (P < 0.0001, P = 0.001, respectively). As discrete variables, E/A ratio and LA area also correlated with CCSs and LVESV. CONCLUSION: Diastolic echo parameters E/A ratio and LA area were associated with clinical and structural outcomes in CRT patients at 6 months.

Left bundle area pacing: Guiding implant depth by ring measurements.

BACKGROUND: Criteria for successful left bundle area pacing (LBAP) are in flux and currently guided by lead tip measurements. Lead ring measurements during LBAP have not been well studied. OBJECTIVE: The purpose of this study was to investigate dynamics in pacing parameters during successful and unsuccessful lead implant attempts. METHODS: SelectSecure 3830 pacing leads (Medtronic, Inc) guided by C315 sheaths for LBAP were placed for standard pacing indications in 73 patients. Retrospective review of procedural, echocardiographic, and standard pacing data were performed. Depth and lead-septal angle of implanted electrodes were determined from fluoroscopy with septal contrast delineation. Depth was graded in 4 categories according to the degree of ring penetration into the septum. Successful implant was defined by the ability to advance the lead deep into the septum and achieve LBAP criteria (ventricular activation time, QRS width/shape). RESULTS: Ring impedance increased stepwise during successful attempts as opposed to unsuccessful attempts (P = .039). A wider lead-septal angle at implant position correlated with higher ring impedance (P = .036), whereas no association was found with tip impedance. Unipolar ring threshold correlated with depth of lead implant (P = .029). Tip impedance measurements at implant position were less predictive of lead depth and did not correlate with septal thickness. CONCLUSION: Ring pacing parameters are more predictive of lead progress than tip measurements. Lead depth and lead-septal angle can be determined from ring impedance measurements. These measurements may provide determination of lead depth and could obviate the need for contrast injection.

Is competitive atrial pacing a possible trigger for atrial fibrillation? Observations from the RATE registry.

BACKGROUND: A high incidence of asymptomatic atrial tachycardia and atrial fibrillation (AT/AF) has been recognized in patients with cardiac implantable devices (CIED). The clinical significance of these AT/AF episodes remains unclear. Some "device-detected AT/AF" was previously shown to be triggered by competitive atrial pacing (CAP). OBJECTIVE: To investigate and characterize a potential association between CAP and AT/AF in the largest series of observations to date. METHODS: RATE, a multicenter registry, included 5379 patients with CIEDs followed for approximately 2 years. Electrograms (EGMs) from 1352 patients with AT/AF, CAP, or both were analyzed by experienced adjudicators to assess a causal relationship between AT/AF and CAP onset, duration, and morphology. RESULTS: In 225 patients, 1394 episodes of both AT/AF and CAP were present in the same tracing. CAP and AT/AF were strongly associated (P ≤ .02). AT/AF occurred during the course of the study in 71% of patients with CAP. In 62% of the episodes, expert adjudication concluded that CAP triggered AT/AF. The duration and morphology of triggered and spontaneous AT/AF episodes differed. Spontaneous AT/AF episodes were associated with constant EGM morphology, and were either long or extremely short. CAP-triggered AT/AF more often had variable and shorter cycle length EGMs. The incidence of short AT/AF events was higher among triggered episodes (25% vs 12.8%, P < .002). CONCLUSION: Device-triggered AT/AF due to CAP is likely more common than previously recognized. This AT/AF entity differs from spontaneous AT/AF in duration and morphology. Clinical implications of spontaneous and device-triggered AT/AF may be different.

Biventricular pacing improves cardiac function and prevents further left atrial remodeling in patients with symptomatic atrial fibrillation after atrioventricular node ablation.

BACKGROUND: Randomized trials have demonstrated benefits of biventricular (BiV) pacing in patients with advanced heart failure, intraventricular conduction delay, and atrial fibrillation (AF) post-atrioventricular (AV) node ablation. The AV Node Ablation with CLS and CRT Pacing Therapies for Treatment of AF trial (AVAIL CLS/CRT) was designed to demonstrate superiority of BiV pacing in patients with AF after AV node ablation, to evaluate its effects on cardiac structure and function, and to investigate additional benefits of Closed Loop Stimulation (CLS) (BIOTRONIK, Berlin, Germany). METHODS: Patients with refractory AF underwent AV node ablation and were randomized (2:2:1) to BiV pacing with CLS, BiV pacing with accelerometer, or right ventricular (RV) pacing. Echocardiography was performed at baseline and 6 months, with paired data available for 108 patients. RESULTS: The RV pacing contributed to significant increase in left atrial volume, left ventricular (LV) end-systolic volume, and LV mass compared to BiV pacing. Ejection fraction decreased insignificantly with RV pacing compared to significant increase with BiV pacing. Interventricular dyssynchrony significantly decreased with BiV compared with RV pacing. Closed Loop Stimulation did not result in additional echocardiographic changes; heart rate distribution was significantly wider with CLS. All groups showed significant improvement in 6-minute walk distance, quality-of-life score, and New York Heart Association class. CONCLUSION: In conclusion, RV pacing results in significant increase in left atrial volume, LV mass, and worsening of LV contractility compared to patients receiving BiV pacing post-AV node ablation for refractory AF. Closed Loop Stimulation was not associated with additional structural changes but resulted in significantly wider heart rate distribution.

Permanent His-bundle pacing using stylet-directed, active-fixation leads placed via coronary sinus sheaths compared to conventional lumen-less system.

BACKGROUND: The use of coronary sinus (CS) sheaths to deliver stylet-driven leads (SDLs) for His-bundle pacing (HBP) has not been described. Conventionally, HBP is achieved using a stylet-less lead delivered through a customized catheter. OBJECTIVE: The purpose of this study was to characterize the acute and early-term HBP experience with stylet-driven, active-fixation leads delivered through CS sheaths compared to the conventional approach. METHODS: Delivery of Medtronic 4471 and 7742 SDLs was attempted in 27 patients. Delivery was facilitated using CS guide catheters and custom-shaped stylets. Procedural characteristics and lead performance were compared to those of a group of 17 patients in whom delivery of 3830 lumen-less leads (LLLs) was attempted. Patients had heterogeneous pacing indications. RESULTS: HBP with SDL was successful in 24 of 27 patients(89%) compared to 15 of 17 patients (88%) in the LLL group. Mean procedural and fluoroscopy times in the SDL and LLL groups were 129 ± 43 minutes vs 104 ± 43 minutes and 9.6 ± 5.2 minutes vs 8.3 ± 5.0 minutes, respectively (both P = NS). There was a significant difference in procedure and fluoroscopy times within the SDL group between the first and second halves of the series, probably secondary to a learning curve. Acute HBP thresholds were higher with SDL than with LLL (2.6 ± 1.5 V vs 1.5 ± 1.2 V; P = .02) and remained stable at 8.4 ± 5.3 months. Both SDLs exhibited similar pacing thresholds. Two crossovers between groups occurred (1 in each group). Four patients with SDL and 1 patient with LLL exhibited high thresholds during follow-up. CONCLUSION: Permanent HBP using stylet-driven, active-fixation leads delivered through conventional CS sheaths is feasible. Procedural characteristics and lead performance were clinically acceptable.

Direct Visualization of the His Bundle Pacing Lead Placement by 3-Dimensional Electroanatomic Mapping: Technique, Anatomy, and Practical Considerations.

BACKGROUND: His bundle pacing (HBP) remains technically challenging and is currently guided by electrograms and 2-dimensional fluoroscopy. Our objective was to describe a new technique for HBP directly guided by electroanatomic mapping (EAM). METHODS: Twenty-eight patients were included. The atrioventricular septum was mapped via EAM, and His bundle (HB) electrograms, selective, and nonselective HB capture sites were tagged. Pacing leads were connected to EAM, navigated to tagged HB target sites and deployed. Intracardiac electrograms and pacing parameters were recorded. Lead location was tagged on the cloud of HB sites, which was divided into 3 arbitrary segments. In 5 patients, atrioventricular nodal ablation was performed with direct visualization of the HBP lead by EAM. RESULTS: Reproducible navigation of the pacing lead to predetermined HBP locations guided by EAM was achieved in all patients. The lead was successfully deployed in 25 patients. HB cloud area was 360 (212) mm2. There was no correlation between HBP threshold and lead location on the His cloud. The intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlated with its EAM position on the His cloud ( P=0.045). Procedure, fluoroscopy, and mapping times were 116.0 (38.8), 8.6 (6.3), and 9.0 (11.4) minutes, respectively. HBP threshold at implant was 1.5 (2.3) V at 1.5 (1.0) ms. Distance between HB lead and ablation sites was 10.0 (1.3) mm in patients undergoing atrioventricular nodal ablation. CONCLUSIONS: Direct guidance of HBP by EAM allows for direct visualization of the pacing lead on the HB cloud and reproducible navigation to predetermined HB capture sites. Intracardiac electrograms atrial/ventricular ratio at the lead deployment site correlates with His cloud location. EAM can be applied during standard HBP procedures or combined with atrioventricular nodal ablation.

Computed tomography-fluoroscopy overlay evaluation during catheter ablation of left atrial arrhythmia.

AIMS: Proper visualization of left atrial (LA) and pulmonary vein (PV) anatomy is of crucial importance during atrial fibrillation (AF) ablation. This two-centre study evaluated a new automatic computed tomography (CT)-fluoroscopy overlay system (EP navigator, Philips Medical Systems, Best, The Netherlands) and the accuracy of different registration methods. METHODS AND RESULTS: Fifty-six consecutive patients (age: 56 +/- 14) with symptomatic AF underwent contrast CT of the LA/PV prior to ablation. Three registration methods were evaluated and validated by comparison with LA angiography: (i) catheter registration: the placement of catheters in identifiable anatomical structures; (ii) heart contour: based on aligning the fluoroscopy heart contours and the 3D-rendered CT volume; and (iii) spine registration: based on automatically aligning the segmented CT spine on fluoroscopy. Computed tomography segmentation was achieved in all but one patient due to motion artefacts. The mean duration of segmentation was 10 min and average registration lasted 7 min. Catheter and heart contour registration were highly accurate (discrepancy of 1.3 +/- 0.6 and 0.3 +/- 0.5 mm, respectively) when compared with spine registration (17 +/- 9 mm, P < 0.05). The EP navigator was helpful during trans-septal puncture, gave an internal view of the atria and allowed tracking of ablation lesions. CONCLUSION: The EP navigator enabled accurate live integration of CT images and real-time fluoroscopy. Registration utilizing catheter placement or heart contours was stable and reliable.

Remote magnetic navigation system provides a superior catheter stability in acquisition of His bundle electrogram.

INTRODUCTION: Catheter stability is a key prerequisite for a successful EP procedure. Remote magnetic navigation system (RMNS) was recently introduced for the manipulation of EP catheters. It may provide an improved catheter stability but this has not been tested prospectively. We performed a prospective cross-over study which compares the amplitude and stability of the His-electrogram obtained by catheters using RMNS vs conventional manual catheter placement. METHODS: His-electrograms were continuously recorded for 3 min with a conventional His mapping catheter and magnetically tipped catheter capable of alignment in the direction of an externally controlled magnetic field (0.08-0.1 Tesla) in the same patient. First 100 beats of each recording were used for data analysis. The amplitudes of each set of His-electrograms were measured and compared in microvolts. Coefficient of variation of the measured His-signal amplitude was calculated for each beat. Miller's test for the equality of the coefficients of variation and Levene's test of homogeneity of variance were used for statistical analysis. RESULTS: Fourteen patients (6 males; aged 48+/-25 years) were included in the study. His-electrograms were more stable and homogenous with RMNS than manual method in 10/14 patients. Pooled variance of all RMNS recordings was significantly less than pooled variance of manual recordings (p=0.01). CONCLUSION: His-electrogram recording using RMNS is more stable and homogeneous than traditional manual method in most patients. These data indicate a superior catheter stability with RMNS.

Baseline myocardial perfusion predicts response to cardiac resynchronization therapy: a prospective observational study.

PURPOSE: We prospectively determined whether preimplant myocardial perfusion imaging (MPI) predicts outcome with biventricular pacing (BiVP). METHODS: Single-photon emission computed tomography (SPECT) MPI, left ventricular (LV) volumes, ejection fraction (EF), 6-min hall walk (6MW) were assessed at baseline and at 4 months in 19 patients with ischemic cardiomyopathy undergoing BiVP. Clinical and hemodynamic responses were correlated with MPI. RESULTS: Lower global myocardial scar burden predicted hemodynamic response to BiVP, while higher burden was associated with poor response. Clinical improvement with BiVP occurred in 12 (63%) of the patients. Clinical BiVP responders had lower rest/stress MPI score difference. There was a close negative correlation between MPI reversibility and increased 6MW distance. CONCLUSIONS: Baseline MPI is associated with clinical and hemodynamic response to BiVP: greater myocardial scar burden is predictive of poor hemodynamic response, while higher ischemic burden is predictive of poor clinical response. There is a differential response to BiVP by clinical and hemodynamic criteria.

Three-dimensional rotational angiography of the left atrium and esophagus--A virtual computed tomography scan in the electrophysiology lab?

BACKGROUND: Three-dimensional (3D) reconstruction of the heart and surrounding structures has been supplementing traditional two-dimensional imaging to guide diagnostic and therapeutic electrophysiologic procedures. Current methods using computed tomography (CT)/magnetic resonance imaging (MRI) reconstruction have certain limitations. OBJECTIVE: We investigated the feasibility of rotational angiography (RA) combined with simultaneous esophagogram to create an intraprocedural 3D reconstruction of the left atrium (LA) and the esophagus. METHODS: Rotational angiography was performed. Contrast was injected via a pigtail catheter positioned in the left or right pulmonary artery to achieve a levophase venous cycle opacification of the ipsilateral pulmonary veins and adjacent LA. Simultaneous administration of oral contrast allowed a 3D reconstruction of the esophagus in the same image. Qualitative and quantitative comparison between the intraprocedural 3D RA and a remote CT scan was performed in 11 consecutive patients undergoing ablation for atrial fibrillation. RESULTS: Adequate visualization of the pulmonary veins, adjacent posterior LA, and esophagus was achieved in 10 patients. Determination of pulmonary transit time to guide the initiation of RA resulted in better-quality imaging. A close correlation between 3D RA and CT was found. Based on close proximity between the LA and esophagus, the ablation procedure was modified in three patients. CONCLUSIONS: Three-dimensional RA of the LA and esophagus is a promising new method allowing intraprocedural 3D reconstruction of these structures comparable in quality to a CT scan. Further studies refining the method are justified because it could eliminate the need for CT/MRI scans before ablation.