Left Voltage Research Articles

High Plasma Concentrations of Transforming Growth Factor-.BETA. and Tissue Inhibitor of Metalloproteinase-1 - Potential Non-Invasive Predictors for Electroanatomical Remodeling of Atrium in Patients With Non-Valvular Atrial Fibrillation -

The degree of electroanatomical remodeling of the left atrial (LA) affects the clinical outcome after rhythm control of atrial fibrillation (AF). Our hypothesis was that plasma concentrations of transforming growth factor (TGF)-β and tissue inhibitor of metalloproteinase (TIMP)-1 reflect LA voltage and structural remodeling in patients with non-valvular AF. In the study, 242 patients (male 79.4%, 55.1 ± 11.0 years old) with AF (155 paroxysmal AF, 87 persistent AF) underwent catheter ablation. Pre-ablation plasma concentrations of TGF-β and TIMP-1 and the degree of electroanatomical remodeling quantified by LA voltage map (NavX) and 3D-CT were evaluated. The mean LA voltage and volume were compared in patients with high TGF-β (≥10.0 ng/ml, H-TGF) vs. low TGF-β (<10.0 ng/ml, L-TGF) and high TIMP-1 (≥1.1 ng/ml, H-TIMP) vs. low TIMP-1 (<1.1 ng/ml, L-TIMP). Patients with H-TGF had lower mean LA voltage (P=0.014) and greater LA volume (P=0.022), particularly, posterior venous LA volume (P=0.005) than those with L-TGF. In patients with H-TIMP, the mean LA voltage (P=0.019) was lower than those with L-TIMP. LA volume was significantly higher (P<0.001) in patients with ejection fraction ≤58% than those with >58%. In patients with non-valvular AF, high plasma concentrations TGF-β and TIMP-1 and low ejection fraction were closely related with electroanatomical remodeling of LA.

Relationship between the Long-Term Result of PVI and Left Atrial Bipolar Voltage during AF Rhythm

Background: Atrium scaring is associated with the result of pulmonary vein isolation (PVI) for the atrial fibrillation (AF). Previous reports have been the area or distribution of myocardium fibrosis correlated with the bipolar voltage map on sinus rhythm. We evaluated the relationship between the long-term result of PVI and left atrial bipolar voltage during AF rhythm as a left atrial substrate. Methods: Forty-six consecutive AF patients (61±10 years old, 31 males) from March to December in 2007 underwent electroanatomical mapping (CARTO) during AF prior to circumferential PVI, and were stored the mean peak-to-peak amplitude of the bipolar electograms as a voltage map. If needed, the multi-sessions including the substrate ablation were performed for the recurrence cases. We retrospectively observed the surface area and distribution of the low voltage zones (LVZ) changing cut-off limit from 0.1 mV to 0.8 mV and evaluated the extent of LVZ by counting the LVZ regions (LVZ score; 0–5) at baseline. Results: The mean LA volume was 116±35 ml. During the follow-up (mean; 28 months) 39 patients (84.7%) had no recurrence of AF without any anti-arrhythmic agents (AAAs). When we defined the LVZ areas as below 0.2 mV, the LVZ score correlated with clinical outcome (sensitivity 100%, specificity 87.2%, AUC 0.91). Conclusions: The distribution of the LVZs below 0.2 mV during AF associated the long-term outcome of the PV isolation.

A Novel Finding: Atrial Substrate Properties and Long-Term Results of Catheter Ablation in Chronic Atrial Fibrillation Patients with Left Atrial Spontaneous Echo Contrast

Background: The atrial substrate in chronic atrial fibrillation (AF) patients with left atrial spontaneous echo contrast (LASEC) has not been previously reported. Methods: Of 36 consecutive patients with chronic AF who received stepwise ablation approach, 18 patients with an LASEC (group I) were compared with 18 age-gender-left atrial volume matched patients without an LASEC (group II). The atrial substrate properties including atrial voltage, dominant frequency (DF), and complex fractionated electrograms (CFEs) in the bi-atrial were evaluated. Result: The left atrial voltage (1.0±0.6 vs. 1.6±0.7 mV, p=0.04), total activation time (119±20 vs. 103±13 msec, p<0.001) and DF (7.3±1.3 vs. 6.6±0.7 Hz, p<0.001) differed between group I and group II, respectively. The bi-atrial CFEs did not differs between group. After a mean follow-up of 30±13 month, there were significant differences in the anti-arrhythmic drugs (1.1±0.3 vs. 0.7±0.5, p=0.02) needed after ablation, and recurrence as persistent AF (92% vs. 50%, p=0.03) between group I and group II, respectively. After multiple procedures, there were more group II patients that remained in SR, when compared with group I (78% vs. 44%, p=0.04). Conclusion: There was a poorer atrial substrate, lesser SR maintenance after catheter ablation and need for more anti-arrhythmic drugs in the chronic AF patients with LASEC when compared with those without LASEC.

Radiofrequency Ablation of Atrial Fibrillation Raises Plasma Levels of Nerve Growth Factor-beta, and Is Associated with Post-Ablation Premature Ventricular Contractions

Introduction: Nerve growth factor-β (NGF-β) expression is increased after radiofrequency ablation (RFA) in patients with atrial fibrillation (AF), indicating cardiac nerve sprouting. We investigated relationship between NGF-β levels before and after RFA and variables in Holter monitoring after RFA in AF patients. Methods: This study included 307 AF patients (236 men, 55.7±11.1 years, 209 paroxysmal AF) underwent RFA. Plasma levels of NGF-β were quantified before and after RFA and Holter monitoring was performed 3 months after RFA. Continuous variables were assessed using the median value as cut-off points. Results: NGF-β levels increased after RFA, compared to before RFA (20.98±14.24 vs. 29.57±19.47 pg/mL, p 17.20 pg/mL had higher proportions of premature ventricular contractions (PVCs) (0.06±0.36 vs. 0.01±0.09%, p=0.038) and LF/HF ratio (1.36±0.52 vs. 1.22±0.41, p=0.007) in Holter monitoring than those with ≤17.20 pg/mL. In patients without increase of NGF-β after RFA, left atrial (LA) was larger (68.3±20.2 vs. 56.9±19.0 mL, p=0.010), and LA appendage voltage (1.97±1.05 vs. 2.53±1.50 mV, p=0.028) and LF/HF ratio (1.15±0.40 vs. 1.32±0.48, p=0.020) were lower, compared to those with increase of NGF-β. Conclusion: Higher pre-RFA NGF-β levels were related to high frequency of PVCs and LF/HF ratio in Holter monitoring after RFA. Lower NGF-β levels were related with electroanatomical remodeling of LA, including larger LA and lower LA voltage.

Associations between the atrial electromechanical interval, atrial remodelling and outcome of catheter ablation in paroxysmal atrial fibrillation

ObjectiveThe atrial electromechanical (PA–PDI) interval was reported to be a useful predictor of new-onset atrial fibrillation (AF) and the occurrence of AF after coronary artery bypass surgery. The aim of...

Atrial Substrate Properties and Outcome of Catheter Ablation in Patients With Paroxysmal Atrial Fibrillation Associated With Diabetes Mellitus or Impaired Fasting Glucose

Diabetes mellitus has been reported to be an independent risk factor of atrial fibrillation (AF). The present study investigated the atrial substrate properties and clinical outcome of catheter ablation in patients with paroxysmal AF and abnormal glucose metabolism. A total of 228 patients with paroxysmal AF who had undergone catheter ablation for the first time were enrolled. An abnormal glucose metabolism (n = 65) was defined as diabetes mellitus or an impaired fasting glucose. We analyzed the clinical and electrophysiologic characteristics in, and the clinical outcome of, patients with AF with and without an abnormal glucose metabolism. The right atrial (107.2 ± 15.4 vs 96.0 ± 16.5 ms, p < 0.001) and left atrial (108.4 ± 22.3 vs 94.0 ± 17.5 ms, p < 0.001) total activation times were significantly longer in the patients with AF and an abnormal glucose metabolism than in those without an abnormal metabolism. Furthermore, the right atrial (1.46 ± 0.61 vs 2.00 ± 0.70 mV, p < 0.001) and left atrial (1.48 ± 0.74 vs 2.05 ± 0.78 mV, p < 0.001) bipolar voltages were significantly lower in those with AF and an abnormal glucose metabolism than in those without. The AF recurrence rate was also greater in the patients with an abnormal glucose metabolism (18.5% vs 8.0%, p = 0.022) than in those without. The follow-up duration was 18.8 ± 6.4 months. In conclusion, an abnormal glucose metabolism affects the biatrial substrate properties with an intra-atrial conduction delay, decreased voltage, and greater recurrence rate after catheter ablation.

Different Patterns of Atrial Remodeling After Catheter Ablation of Chronic Atrial Fibrillation

Multiple remodeling patterns have been observed after catheter ablation of atrial fibrillation (AF). We aimed to clarify the electrical/structural properties associated with recurrences after ablation of chronic AF. After a stepwise ablation procedure in 120 consecutive patients with persistent/long-lasting persistent AF, 36 had a recurrence of AF (Group 1/Group 2: recurrence with paroxysmal/persistent AF, n = 16/20). During the first procedure, the left atrial (LA) bipolar voltage did not differ between the 2 groups, and the LA volume was smaller in Group 1 than in Group 2 and it was the only factor predicting the recurrent types (P = 0.009, OR = 1.04). In the second procedure, the bipolar voltage of the global left atrium increased (1.33 ± 0.11 mV vs 1.76 ± 0.16 mV, P = 0.001) in Group 1 and decreased (1.31 ± 0.14 mV vs 0.90 ± 0.12 mV, P = 0.01) in Group 2, when compared with that of the first procedure. The LA low-voltage area (<0.5 mV) decreased in Group 1, and increased in Group 2. The LA volume (90 ± 8 cm(3) vs 72 ± 8 cm(3), P = 0.002) decreased in the second procedure in Group 1. It remained the same in Group 2. The right atrial substrates did not change between the procedures. After a follow-up of 27 ± 3 months, all patients in Group 1 and 14 patients in Group 2 remained in sinus rhythm (P = 0.02). A better outcome with reverse electrical and structural remodeling occurred after the ablation of chronic AF when the recurrence was paroxysmal AF. Progressive electrical remodeling without any structural remodeling developed in those with a recurrence involving persistent AF.

Prognostic Implications of the High-Sensitive C-Reactive Protein in the Catheter Ablation of Atrial Fibrillation

Previous studies have reported that increased high-sensitive C-reactive protein (hs-CRP) levels are associated with an inflammatory state. This study investigated the association among hs-CRP, substrate properties, and long-term clinical outcomes after catheter ablation of atrial fibrillation (AF). A total of 137 patients with AF (54 +/- 13 years) who underwent mapping and catheter ablation were included. The hs-CRP was measured before the first ablation procedure. The substrate properties (initiating triggers, biatrial mean voltage, and high-frequency sites) of the 2 atria and long-term outcome were investigated in patients in the low hs-CRP group (<75%, 2.92 mg/L) and high hs-CRP group (>75%, 2.92 mg/L). Patients with a higher hs-CRP were associated with an increased number of identified nonpulmonary vein ectopies (34.4% vs 17%, p = 0.034), lower mean left atrial (LA) voltage (1.72 +/- 0.73 vs 1.92 +/- 0.72 Hz, p = 0.045), and higher-frequency sites in the left atrium (71% vs 37%, p = 0.027). After a median follow-up period of 15 months, the single-procedure success rate (72% vs 53%, p = 0.008) and final success rate after multiple procedures (94% vs 81%, p = 0.02) were higher in the low hs-CRP group. In a multivariable regression model adjusted for other potential covariates, hs-CRP level (p = 0.021) and LA diameter (p = 0.032) were independent predictors of recurrence. In conclusion, baseline CRP levels before the first AF ablation procedure had an independent prognostic value in predicting long-term recurrence. Patients with a high hs-CRP level were associated with an abnormal LA substrate and high incidence of nonpulmonary vein AF sources.

The Impact of Diastolic Dysfunction on the Atrial Substrate Properties and Outcome of Catheter Ablation in Patients With Paroxysmal Atrial Fibrillation

The presence of diastolic dysfunction increases the risk of atrial fibrillation (AF), and might be associated with the left atrial (LA) substrate. The aim of the present study was to investigate the relationships between the diastolic dysfunction, atrial substrate and outcome of the catheter ablation. Eighty-three patients with paroxysmal AF were enrolled. Diastolic dysfunction was defined as a left ventricular ejection fraction (LVEF) of ≥ 50%, and one of the following criteria: (1) a mitral inflow early filling velocity to atrial filling velocity ratio (E/A) of ≤ 0.75; or (2) an E/A ratio of >0.75 and a ratio of the mitral inflow early filling velocity to the velocity of the early medial mitral annular ascent of >10. Patients with diastolic dysfunction were older than those with normal cardiac function. There were no differences in the other baseline characteristics, LA diameter, or LVEF. A decreased LA voltage, and higher recurrence rate were noted in patients with diastolic dysfunction. In the univariate analysis, the patients with recurrence had a lower LA voltage and greater diastolic dysfunction. The multivariate analysis also indicated diastolic dysfunction and LA voltage as independent predictors of recurrence. The patients with diastolic dysfunction developed a different atrial substrate and had a worse outcome of catheter ablation for atrial fibrillation.

Left Atrial Voltage during Atrial Fibrillation in Paroxysmal and Persistent Atrial Fibrillation Patients

Left atrial (LA) endocardial voltage characteristics assessed during atrial fibrillation (AF) have not been previously compared in different AF types. This study was aimed at investigating the LA voltages and volumes in patients with paroxysmal and persistent AF. LA electroanatomic voltage maps acquired during AF were compared between consecutive patients without major structural heart disease undergoing first catheter ablation for paroxysmal AF (n = 100) or persistent AF (n = 100). The groups were comparable in baseline clinical characteristics. Patients with persistent AF presented with lower median LA voltage (median 0.41, interquartile range [IQR] 0.31-0.51 mV versus median 0.99, IQR 0.47-1.56 mV; P < 0.001), and maximum LA voltage (4.07 +/- 1.76 vs 6.42 +/- 2.16 mV; P < 0.001). They also had a higher proportion of the LA points exhibiting voltage <0.2 mV (30 +/- 20 vs 12 +/- 11%; P < 0.001) and voltage 0.2-1.0 mV (55 +/- 15 vs 42 +/- 19%; P < 0.001). They further displayed higher LA volume/body surface area (75 +/- 16 vs 58 +/- 13 mL/m(2); P < 0.001). In the multivariate regression model, both LA voltage (P < 10(-9)) and LA volume (P < 10(-5)) were significant determinants of AF type. Patients with persistent AF had significantly lower LA voltage compared with patients with paroxysmal AF even after adjustment for differences in indexed LA volume. LA voltage represents an independent covariate of clinical manifestation of AF.

The Relationship Between Endocardial Voltage and Regional Volume in Electroanatomical Remodeled Left Atria in Patients with Atrial Fibrillation: Comparison of Three‐Dimensional Computed Tomographic Images and Voltage Mapping

Long-standing atrial fibrillation (AF) changes left atrial (LA) morphology, and the LA size is related to recurrence after radiofrequency catheter ablation (RFCA). We hypothesize that LA morphology, based on embryological origin, affects the outcome of RFCA. We analyzed 3D computed tomographic (CT) images of LA in 70 patients with AF (54 males, 55.6 +/- 10.5 years old, paroxysmal AF (PAF):persistent AF (PeAF) = 32:38) who underwent RFCA. Each LA image was divided into venous atrium (VA), anterior LA (ALA), LA appendage (LAA), and both antrum. Absolute and relative volumes were calculated, and the lengths of linear ablation sites were measured. (1) In patients with the mean LA voltage < or = 2.0 mV, LA volume, especially ALA, was larger (P < 0.01) compared to those with LA voltage > 2.0 mV. (2) The total LA volume was significantly larger (P < 0.01) and LAA voltages (P < 0.05) and conduction velocities (P < 0.05) were lower in patients with PeAF than in those with PAF. (3) In patients with recurrence, LA volume was generally larger (P < 0.01) than in those without recurrence. In PAF patients with recurrence, the relative volume of ALA was significantly larger (P < 0.01) than those without recurrence. Morphologically remodeled LA has low endocardial voltage, and enlargement of ALA is more significant in electroanatomically remodeled LA. The disproportional enlargement of ALA was observed more often in PAF patients with recurrence after ablation than those without recurrence.

Acute Effect of Circumferential Pulmonary Vein Isolation on Left Atrial Substrate

The left atrial (LA) substrate plays an important role in the maintenance of atrial fibrillation (AF). However, little is known about the acute effect of circumferential pulmonary vein isolation (CPVI). This study was to investigate the acute change of LA activation, voltage and P wave in surface electrocardiogram (ECG) after CPVI. Electroanatomic mapping (NavX) was performed in 50 patients with AF (mean age = 54 +/- 10 years, 36 males) who underwent only CPVI. The mean peak-to-peak bipolar voltage and total activation time of LA were obtained during sinus rhythm before and immediately after CPVI. The average duration and amplitude of P waves in 12-lead ECG were also analyzed before and after CPVI. Change in the earliest LA breakthrough sites could cause decreased LA total activation time. Downward shift in the breakthrough site was inversely proportional to the proximity of the breakthrough site to the radiofrequency lesions. A shortening of P-wave duration and decrease in voltage after CPVI were observed after CPVI. Patients with recurrent AF had less voltage reduction in the atrial wall 1 cm from the circumferential PV lesions compared with those without recurrent AF (60.1 +/- 11.7% vs 74.1 +/- 6.6%, P = 0.002). Reduction of voltage < or = 64.4% in this area after CPVI is related with recurrent AF. CPVI could result in acute change of LA substrate, involving LA activation and voltage. Less reduction of voltage in the atrial wall adjacent to the circumferential PV lesions after CPVI may be associated to the recurrence of AF.

Electrophysiologic Characteristics of Complex Fractionated Atrial Electrograms in Patients with Atrial Fibrillation

The underlying mechanisms of complex fractionated atrial electrogram (CFAE) during radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF) have not yet been clearly elucidated. We explored the relationships between CFAE and left atrial (LA) voltage, or conduction velocity (CV). In 50 patients with AF (23 paroxysmal AF [PAF], 41 males, mean age 55.76 +/- 10.16 years), the CFAE (average index of fractionation of electrograms during AF by interval-analysis algorithm, cycle length [CL]<or= 120 ms) areas, voltage, and CV were measured at eight different quadrants in each patient's LA by analyzing a NavX-guided, color-coded CFAE CL map, a voltage map, and an isochronal map (500 ms pacing) generated by contact bipolar electrograms (70-100 points in the LA). The results were: (1) CFAE areas were predominantly located in the septum, roof, and LA appendage; (2) CFAE area had lower voltage than those in non-CFAE area and was surrounded by the areas of high voltage (P < 0.0001); (3) The CFAE areas had low CVs compared with non-CFAE areas (P < 0.001); and (4) The percentage of CFAE area was lower in patients with persistent atrial fibrillation (PeAF) compared with those with PAF (P < 0.05). The CFAE area, which is primarily located at the septum, has a low voltage with a lower CV, and is surrounded by high-voltage areas. Underlying electroanatomical complexity is associated with clustering of CFAEs.

Retrograde Ethanol Infusion in the Vein of Marshall

Background— The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation because of its autonomic innervation, its location anterior to the left pulmonary veins, and its drainage in the coronary sinus. Methods and Results— We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium toward the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation. The ERP decreased from 113.6�35.0 to 82.2�25.4 ms ( P &lt;0.05) after vagal stimulation. After VOM ethanol infusion, vagally-mediated ERP decrease was eliminated (from 108.6�24.1 to 96.4�16.9 ms, P =NS). The abolition of vagal effects was limited to sites near the VOM (ERP, 104�14 versus 98.6�12.2 ms postvagal stimulation; P =NS), as opposed to sites remote to VOM (ERP, 107.2�14.9 versus 78.6�14.7 ms postvagal stimulation; P &lt;0.05). To test feasibility in humans, 6 patients undergoing pulmonary vein antral isolation had successful VOM cannulation and ethanol infusion; left atrial voltage maps demonstrated new scar involving the inferoposterior left atrial wall extending toward the left pulmonary veins. Conclusions— Ethanol infusion in the VOM achieves significant left atrial tissue ablation, abolishes local vagal responses, and is feasible in humans.

Regional Endocardial Left Atrial Voltage and Electrogram Fractionation in Patients with Atrial Fibrillation

Heterogeneities in electrophysiological properties may contribute to the development of atrial fibrillation, and regional disparities in endocardial voltage in the left atrium have been related to arrhythmogenic mechanisms. This study aimed at investigating endocardial voltage in different regions of the left atrium in patients with atrial fibrillation (AF). Thirty-six patients (aged 56 +/- 7 years, 10 female) scheduled for circumferential ablation for paroxysmal AF were studied. Voltage measurements were performed during AF and with constant right ventricular pacing in the anterior, posterior, superior and inferior walls outside the antrum of the left (LPV), and right (RPV) pulmonary veins, by means of electroanatomical mapping. There was a high agreement among measurements performed in the endocardium of the posterior atrial wall (ICC > 0.70), and moderate agreement among measurements performed in the superior and inferior walls (0.50 < ICC< 0.70), outside both PV antra. The posterior left atrial wall demonstrated significantly higher voltages both outside the LPV antrum (1.29 +/- 1.36 mV) and the RPV antrum (1.20 +/- 0.63 mV) compared to the inferior, anterior and superior walls (0.47 +/- 0.49, 0.68 +/- 0.69, and 0.61 +/- 0.83 mV outside the LPV antrum, and 0.39 +/- 0.23, 0.65 +/- 0.49, and 0.49 +/- 0.24 mV outside the RPV antrum, respectively). Fractionated electrograms were mainly identified at the posterior left atrial wall, outside the right PV antrum. During AF, the posterior wall displays significantly higher voltage and electrogram fractionation compared with other parts of the left atrial endocardium outside the antra of both pulmonary veins in patients with paroxysmal AF.

Predicting factors for atrial fibrillation acute termination during catheter ablation procedures: Implications for catheter ablation strategy and long-term outcome

Termination of atrial fibrillation (AF) can be achieved by catheter ablation. It has been used as one of the procedural endpoints for AF ablation. The purpose of this study was to investigate the factors that predict AF termination and the association with long-term outcomes. Eighty-five consecutive AF patients (33 paroxysmal, 52 nonparoxysmal) underwent three-dimensional mapping and catheter ablation. A stepwise ablation approach included circumferential pulmonary vein (PV) isolation and left atrial (LA) linear ablation, followed by LA and right atrial (RA) electrogram-based (complex fractionated atrial electrogram) ablation. Clinical and electrophysiologic characteristics were assessed to evaluate the predictors of acute AF termination. In univariate analysis, a diagnosis of paroxysmal AF, shorter AF history, absence of history of heart failure, smaller LA diameter, longer postablation coronary sinus cycle length, lower LA and RA mean dominant frequencies, lower RA max dominant frequency, and higher LA voltage were related to acute termination of AF during ablation. Multivariate analysis showed that smaller LA diameter and lower preablation mean RA dominant frequency were independent predictors of AF termination. Multivariate analysis also showed that larger LA diameter and the presence of RA non-PV ectopy during the index procedure could predict late recurrence during long-term (13 +/- 8 months) follow-up. LA size and RA non-PV drivers are important for acute termination of AF and for long-term success. Careful selection of patients, extensive RA mapping, and LA ablation may enhance long-term ablation efficacy.

Abstract 4655: Retrograde Ethanol Infusion in the Vein of Marshall for Ablation of Atrial Fibrillation: Tissue Ablation, Effects on Regional Vagal Innervation and First Human Experience

The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation and its location anterior to the left pulmonary veins and drainage in the coronary sinus. We studied 14 dogs. A coronary sinus venogram showed a VOM in 10, which was successfully cannulated with an angioplasty wire and a 2 mm balloon. In 5 dogs, electroanatomical (Carto) maps of the left atrium were performed at baseline and after ethanol (100%, 4 – 8 cc) was infused in the VOM, which demonstrated the creation of a new crescent-shaped scar in the left atrium, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 dogs, both cervical vagal trunks were isolated in the carotid sheath and cuff stimulation electrodes were attached to them. Effective refractory periods (ERP) were measured in 3 sites of the left atrium, before and after high-frequency bilateral vagal stimulation. The baseline ERP was 113.6±35.0 ms, and decreased to 82.2±25.4 ms (p&lt;0.05) after vagal stimulation. After alcohol infusion in VOM, vagally-mediated ERP decrease was eliminated (from 108±27.2 ms to 95.6 ±16.7ms, p=NS). This elimination of vagal effects was not uniform and was limited in sites in proximity with the VOM (baseline ERP 105±18.7ms vs post vagal 98.±37.6ms, p=NS, as opposed to 106.7±27.1ms vs post vagal 73.3±19.7ms, p&lt;0.05, in sites remote to VOM). We also tested feasibility of VOM alcohol infusion in humans: 2 patients undergoing pulmonary vein antral isolation had successful VOM cannulation: left atrial voltage maps demonstrated new scar involving the infero-posterior left atrial wall extending towards the left pulmonary veins. Retrograde alcohol infusion in the VOM achieves significant left atrial tissue ablation, abolishes local vagal responses and is feasible in humans.

Abstract 2751: Correlation of Left Atrial Voltage Maps with Cardiovascular MR Provides Evidence of Pre-existent Scar in Atrial Fibrillation Patients

Introduction: There is increasing evidence for and interest in detecting electrically silent left atrial (LA) myocardium which may be the substrate of atrial fibrillation (AF). Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) might detect these areas of pre-existent scar as high signal in the LA wall. We sought to correlate the extent low-voltage areas in AF patients with clinical parameters of LA volume and type of AF, and to correlate areas of low voltage with areas of high signal on LGE CMR, indicating areas of scarred tissue. Methods: Twenty-two patients with AF underwent high resolution atrial LGE CMR on a 1.5 T CMR scanner and bipolar voltage electroanatomic mapping (Carto, Biosense Webster). The number of the LA mapping points with low (&lt; 0.1mV) voltage was calculated for each patient. LA systolic volume was measured, indexed to BSA. Using the voltage maps, blood-LA contrast to noise ratio (CNR) was measured on the LGE CMR images in two areas, low and high voltage areas (N=10). Hypothesis testing used t-tests and p&lt;0.05. Results: The average extent of LA low voltage was 8 % of the LA. Four (18%) patients had no low voltage regions. The extent of low voltage for patients with non-paroxysmal vs. paroxysmal AF was 11 ± 13% vs. 4 % ± 5 % (p=0.08). The extent of low voltage for patients with larger than median LA volumes vs. smaller LA volumes was 12 ± 13% vs. 1 ± 1 % (p=0.027). In 10 patients in which LGE was measured in low and high voltage regions, the CNR was 10 vs. 6 (p=0.016). Conclusions: Patients with extensive low voltage regions in the LA have larger LA volumes. The CNR is higher in low-voltage regions, suggesting that such regions of possible scar can be identified by LGE CMR. This research has received full or partial funding support from the American Heart Association, AHA National Center.

Impairment of the Atrial Substrates by Chronic Cigarette Smoking in Patients with Atrial Fibrillation

Smoking is a major risk factor for cardiovascular disease. The impact of smoking on the right and left atrial substrates is unknown. This study included 88 patients (age 50 +/- 13 years, M/F = 71/17) who underwent four pulmonary veins isolation (PVI) for paroxysmal atrial fibrillation (AF). The mean voltage and total activation time of the individual atria were obtained by using a NavX mapping system, and were compared between the patients with and without a previous smoking history. The dose effect was evaluated by the smoking intensity-duration, defined as the number of packs per day plus how many years they had been smoking. The right atrial (RA) mean voltage was lower in the patients with a previous history of smoking than in those without a history of smoking (1.92 +/- 0.49 vs 2.17 +/- 0.56 mV, P < 0.05). The left atrial (LA) mean voltage was similar between the two groups (1.73 +/- 0.67 vs 1.82 +/- 0.48 mV, P = 0.488). Further, the total activation time of the RA was longer in the patients with a previous history of smoking than in those without a history of smoking, but not so for the LA. Furthermore, the voltage reduction in the RA was related to the smoking intensity-duration (Pearson's correlation, r = 0.650, P < 0.001). In patients with atrial fibrillation, the RA mean voltage and total activation time were significantly correlated to smoking and had a dose-dependent effect.

Do the Left Atrial Substrate Properties Correlate with the Left Atrial Mechanical Function? A Novel Insight from the Electromechanical Study in Patients with Atrial Fibrillation

The atrial substrate is the determinant of occurrence and maintenance of atrial fibrillation (AF), which can induce remodeling of atrial function and structure. This study investigated the relationship between the left atrial (LA) substrate properties and LA mechanical function. Forty-four consecutive patients (50.3 +/- 10.7 years old, 33 men) who presented with sinus rhythm during echocardiographic study before receiving catheter ablation for AF were enrolled. The LA diameter, LA volume, ratio of early and late transmitral filling flow velocities (E/A), LA appendage flow velocity, and transmitral velocity-time integral (VTI) were measured by the echocardiography. The LA empty fraction (LAEF), which was obtained via dividing the difference between maximal and minimal LA volume by maximal LA volume, was calculated as a parameter of the global LA contractile function. The LA global contact voltage mapping (NavX system) was performed before pulmonary vein isolation. Mean LA voltage and LA low voltage zone index (LVZ index, area with voltage < 0.5 mV, divided by total LA surface area) showed significant correlation with LA diameter and volume, but only the LA LVZ index showed significant correlation with A-wave velocity, transmitral A-wave VTI, and LAEF (r =-0.340, -0.411, -0.426; P = 0.024, 0.006, 0.005, respectively). We divided the LA LVZ index into three groups (< 10%, 10-20%, > 20%). The LAEF got worse and the transmitral A-wave VTI percentage (divided by transmitral VTI) decreased as LA LVZ index increased. The LA substrate properties showed close correlation with LA size, but only the LA LVZ index correlated with the LA mechanical function.