Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity.

OBJECTIVES: To characterize the nature of atrial fibrillation (AF) activation in human persistent AF (PerAF) using modern tools including activation, directionality analyses, complex-fractionated electrogram, and spectral information. BACKGROUND: The mechanism of PerAF in humans is uncertain. METHODS AND RESULTS: High-density epicardial mapping (128 electrodes/6.75 cm(2)) of the posterior LA wall (PLAW), LA and RA appendage (LAA, RAA), and RSPV-LA junction was performed in 18 patients with PerAF undergoing open heart surgery. Continuous 10 s recordings were analysed offline. Activation patterns were characterized into four subtypes (i) wavefronts (broad or multiple), (ii) rotational circuits (≥2 rotations of 360°), (iii) focal sources with centrifugal activation of the entire mapping area, or (iv) disorganized activity [isolated chaotic activation(s) that propagate ≤3 bipoles or activation(s) that occur as isolated beats dissociated from the activation of adjacent bipole sites]. Activation at a total of 36 regions were analysed (14 PLAW, 3 RSPV-LA, 12 LAA, and 7 RAA) creating a database of 2904 activation patterns. In the majority of maps, activation patterns were highly heterogeneous with multiple unstable activation patterns transitioning from one to another during each recording. A mean of 3.8 ± 1.6 activation subtypes was seen per map. The most common patterns seen were multiple wavefronts (56.2 ± 32%) and disorganized activity (24.2 ± 30.3%). Only 2 of 36 maps (5.5%) showed a single stable activation pattern throughout the 10-s period. These were stable planar wavefronts. Three transient rotational circuits were observed. Two of the transient circuits were located in the posterior left atrium, while the third was located on the anterior surface of the LAA. Focal activations accounted for 11.3 ± 14.2% of activations and were all short-lived (≤2 beats), with no site demonstrating sustained focal activity. CONCLUSION: Human long-lasting PerAF is characterized by heterogeneous and unstable patterns of activation including wavefronts, transient rotational circuits, and disorganized activity.

Absence of gender-based differences in the atrial and pulmonary vein substrate: a detailed electroanatomic mapping study.

BACKGROUND: Gender-based differences in the clinical nature of cardiac arrhythmias such as atrial fibrillation (AF) are well established. OBJECTIVE: The purpose of this study was to identify any such gender-based differences in the underlying pulmonary vein and atrial substrate. METHODS AND RESULTS: Thirty-eight patients with no history of AF undergoing catheter ablation for supraventricular tachycardia (SVT) and 55 with paroxysmal or persistent AF undergoing catheter ablation of AF underwent detailed electroanatomic mapping of the pulmonary veins and atria. Refractory periods in multiple locations, sinus node function, endocardial bipolar voltage, pulmonary vein and atrial conduction, and bipolar electrogram complexity were analyzed. There were no significant between-gender differences in age or other clinical variables known to impact on the atrial or pulmonary vein substrate. In neither the AF nor the non-AF cohorts were there any significant differences in atrial or pulmonary vein refractoriness, sinus node function, any measure of PV electrophysiology, or any measure of atrial electrophysiology. CONCLUSION: No systematic between-gender differences were observed in the PV or atrial substrate either in those with or without a history of AF, with a similar prevalence of the cardiovascular comorbidities frequently associated with atrial remodeling and AF seen in both male and female groups.

Catheter-tissue contact force determines atrial electrogram characteristics before and lesion efficacy after antral pulmonary vein isolation in humans.

INTRODUCTION: Electrogram (EGM) characteristics are used to infer catheter-tissue contact. We examined if (a) atrial EGM characteristics predicted CF and (b) compared the value of CF versus other surrogates for predicting lesion efficacy. METHODS AND RESULTS: Twelve paroxysmal AF patients underwent pulmonary vein isolation using radiofrequency (RF) ablation facilitated by a novel CF-sensing catheter. Operators were blinded to CF. EGM amplitude, width, and morphology were measured pre- and post-RF. At each RF site, average CF, force-time integral (FTI), impedance fall, time to impedance plateau, maximum power, catheter tip temperature, and total energy delivered were recorded. An effective lesion was defined based on previously validated EGM criteria for transmural lesions. There was a moderate correlation between CF and EGM amplitude (r = 0.19) and EGM width (r = -0.22). Pre-RF, EGM amplitude, and width had modest to poor discriminative capacity for identifying preablation CF (e.g., EGM amplitude identified CF>20 g with sensitivity and specificity of 67% and 60%, respectively). Preablation CF, FTI, and total energy delivered during RF were the only independent predictors of effective lesion formation. Neither pre-RF EGM amplitude/width nor power, temperature, and impedance changes during RF predicted effective lesion formation. An average CF >16 g or FTI >404 g*s had excellent sensitivity and specificity (>80%) for identifying an effective lesion. CONCLUSIONS: EGM characteristics do not reliably predict either CF before the onset of RF, nor do they predict the likelihood of an effective lesion. CF parameters were superior to power, temperature, and impedance changes during RF in predicting lesion efficacy.

Atrial electrical and structural remodeling associated with longstanding pulmonary hypertension and right ventricular hypertrophy in humans.

INTRODUCTION: Pulmonary hypertension (PH) is common to a range of cardiopulmonary conditions and is associated with atrial arrhythmias. However, little is known of the isolated atrial effects of PH and right atrial dilatation (RA) in humans. To avoid the confounding effects of PH-associated disease states, we performed detailed electrophysiological (EP) and electroanatomic (EA) mapping of the RA in patients with idiopathic PH. METHODS AND RESULTS: Eight PH patients (mean pulmonary arterial [PA] pressure 39.0 ± 15.8 mmHg) and 16 age-matched controls (mean PA pressure 11.5 ± 4.1 mmHg, P < 0.0001) were studied. Corrected sinus node recovery times (cSNRT), atrial effective refractory periods (ERPs), conduction delay at the crista terminalis (CT), and inducibility of atrial fibrillation (AF) were evaluated. EA mapping (pacing cycle length 600 and 300 milliseconds) was performed to determine RA global and regional voltage, conduction velocities, atrial activation times, fractionated electrograms and double potentials. Patients with PH demonstrated a prolongation in cSNRT without significant change in atrial ERP and an increase in AF inducibility. PH was associated with lower tissue voltage (1.8 ± 0.4 mV in PH vs 2.2 ± 0.4 mV in controls, P = 0.02), increased low voltage areas (13.7 ± 8.2% in PH vs 6.2 ± 3.7% in controls, P < 0.01) and the presence of electrically silent areas. Conduction velocities were slower (global 67.3 ± 5.6 cm/s vs 92.8 ± 4.0 cm/s, P < 0.001) and fractionated electrograms and double potentials were more prevalent (14.7 ± 4.4% vs 6.3 ± 4.1, P < 0.01) in PH compared with controls, respectively. CONCLUSION: Idiopathic PH is associated with RA remodeling characterized by: generalized conduction slowing with marked regional abnormalities; reduced tissue voltage; and regions of electrical silence. These changes provide important insights into the isolated effects of PH fundamental to a range of clinical conditions associated with AF.

Electroanatomic remodeling of the left atrium in paroxysmal and persistent atrial fibrillation patients without structural heart disease.

INTRODUCTION: The nature of the atrial substrate thought to contribute toward maintaining atrial fibrillation (AF) outside the pulmonary veins remains poorly defined. Therefore, our objective was to determine whether patients with paroxysmal and persistent AF have an abnormal electroanatomic substrate within the left atrium (LA). METHODS AND RESULTS: Thirty-one patients with AF (17 paroxysmal AF and 14 persistent AF) were compared with 15 age-matched controls with left-sided supraventricular tachycardia (SVT). High-density 3-dimensional electroanatomic maps were created and the LA was divided into 8 segments for regional analysis. Bipolar voltage, conduction, and effective refractory periods (ERPs) of the posterior LA, left atrial appendage (LAA), and distal coronary sinus (CSd) and percentage complex signals were assessed. In the majority of LA regions, compared with controls, AF patients had: (1) lower mean voltage and a higher percentage low voltage; (2) slower conduction; and (3) more prevalent complex signals. Many of these changes were more marked in the persistent than the paroxysmal AF group. CONCLUSIONS: Patients with AF have lower regional voltage, increased proportion of low voltage, slowed conduction, and increased proportion of complex signals compared to controls. Many of these changes are more pronounced in persistent AF patients, suggesting there may be a progressive nature to the changes. Differences occurred in the absence of structural heart disease. These substrate abnormalities provide further insight into the progressive nature of atrial remodeling and the mechanisms involved in maintenance of AF.

Electroanatomic remodelling of the pulmonary veins associated with age.

AIMS: Increasing age is a significant risk factor for developing atrial fibrillation (AF). Pulmonary vein (PV) triggers are critical in the mechanism of AF, but little is known of the substrate changes that occur within the PVs with ageing. Therefore, we sought to identify whether ageing is associated with electroanatomic changes within the pulmonary veins. METHODS AND RESULTS: Twenty-five patients undergoing ablation for left-sided supraventricular tachycardia had high-density 3D electroanatomic maps of all four PVs created. Patients were divided into two groups: group 1 aged <50 years and group 2 aged >50 years. Mean-voltage (MV), % low-voltage (LV < 0.5 mV), conduction, signal complexity, and PV muscle sleeve length and diameter were assessed. Age was 33 ± 8 vs. 66 ± 8 years for groups 1 and 2, respectively (P < 0.001). Group 2 demonstrated: (i) lower MV within the PVs (1.66 ± 1.1 vs. 1.88 ± 1.1 mV, P < 0.001); (ii) increased % LV (5.0 vs. 1.1%, P < 0.001), and increased voltage heterogeneity within the PVs (65 ± 14 vs. 55 ± 8%, P < 0.05); (iii) regional and global conduction slowing in the PVs; and (iv) increased % complex signals within the PVs (1.4 vs. 0.4%, P = 0.009). There was no difference in PV sleeve length or diameter. CONCLUSION: Increasing age is associated with PV electroanatomic changes characterized by a significant reduction in PV voltage, conduction slowing, and increasing signal complexity. These observations provide new insights into the potential mechanisms behind the increased prevalence of AF with advancing age.

Atrial electrical and structural changes associated with longstanding hypertension in humans: implications for the substrate for atrial fibrillation.

UNLABELLED: INTRODUCTION: Hypertension (HT) is the most common modifiable risk factor for atrial fibrillation (AF), yet little is known of the atrial effects of chronic HT in humans. We aimed to characterize the electrophysiologic (EP) and electroanatomic (EA) remodeling of the right atrium (RA) in patients with chronically treated systemic HT and left ventricular hypertrophy (LVH) without a history of AF. METHODS AND RESULTS: Twenty patients with (systolic BP 145 ± 10 mmHg) and without (BP 119 ± 11 mmHg, P < 0.01) systemic HT underwent detailed conventional EP and EA voltage and activation mapping. We measured RA refractoriness at the coronary sinus and high septum at cycle lengths (CLs) 600 and 450 ms, and RA conduction velocities, activation times, and voltages at a global and regional level at CLs 600 ms and 300 ms. HT was associated with slowing of global (73 ± 17 cm/s vs 96 ± 12 cm/s in controls, P < 0.01) and regional conduction velocity particularly in the posterior RA (70 ± 17 cm/s vs 96 ± 12 cm/s in controls, P < 0.01) at the crista terminalis (fractionation and double potentials in HT 72%± 4 vs 43%± 23 in controls, P = 0.04). Mean RA voltage was similar between the 2 groups, however HT was associated with an increase in areas of low voltage (<0.5 mV; HT 13% vs controls 9%, P = 0.04). Sustained AF was induced in 30% HT patients and no controls. CONCLUSION: Chronically treated systemic HT with LVH is accompanied by atrial remodeling characterized by: (i) global conduction slowing, (ii) regional conduction delay particularly at the crista terminalis, and (iii) increased AF inducibility. These changes may in part be responsible for the increased propensity to AF associated with systemic HT.

Electroanatomic properties of the pulmonary veins: slowed conduction, low voltage and altered refractoriness in AF patients.

INTRODUCTION: Rapid PV activity is critical in initiating and maintaining AF. The underlying substrate responsible for this remains uncertain. We sought to identify if patients with paroxysmal (PAF) and persistent atrial fibrillation (PeAF) have an abnormal substrate within the pulmonary veins (PVs). METHODS AND RESULTS: Thirty-nine patients with AF (21 PAF, 18 PeAF) were compared with 15 age-matched controls with left-sided accessory pathways (AVRT). High-density 3D electroanatomic maps of the PVs were created. PV voltage, conduction, PV muscle sleeve length, effective refractory periods (ERPs) of the PVs, posterior left atrium (PLA), left atrial appendage (LAA) and distal coronary sinus (CSd), and signal complexity were assessed. Compared with controls, the PVs of AF patients had (1) lower mean-voltage and a higher % low-voltage; (2) shorter PV muscle sleeves; (3) slower conduction; (4) shorter ERP; and (5) more prevalent complex signals. Compared with the PAF group, the PeAF group had (1) higher % low voltage; (2) slower conduction; and (3) more complex signals. In PAF patients, the PLA and LAA ERPs were longer than controls and the PV ERP was shorter than controls; in PeAF patients PLA and LAA ERPs were reduced, but to a lesser extent than in the PVs. AF induction occurred during PV ERP testing in both AF groups, but not controls. CONCLUSIONS: PAF and PeAF patients demonstrate electrical and electroanatomic remodeling of the PVs compared to control patients without prior AF. Some of these changes were more marked in PeAF.

The relationship between complex fractionated electrograms and atrial low-voltage zones during atrial fibrillation and paced rhythm.

AIMS: Mapping of atrial fibrillation (AF) involves identification of low-voltage regions associated with complex fractionated electrograms (CFE) which theoretically represent abnormal substrate and targets for ablation. Whether low-voltage CFE areas also identify abnormal substrate during paced rhythm is unknown. METHODS AND RESULTS: Twelve patients with persistent AF undergoing ablation of AF had high-density three-dimensional electroanatomic maps created during AF and paced rhythm (24 maps) and the mean voltage during AF and paced rhythm was compared for eight segments of the left atrium (LA). The following were correlated during AF and paced rhythm: regional mean voltage; %low voltage (defined as <0.5 mV); and extent of CFE. In addition, the relationship between the extent of CFE in AF: (i) %low voltage and (ii) conduction during paced rhythm were determined. Mean voltage was lower during AF than paced rhythm for all regions and globally (0.7 ± 0.2 mV vs. 2.1 ± 0.6 mV, P < 0.001). The regional and overall %low voltage of the LA was greater during AF than paced rhythm (53 ± 19% vs. 9 ± 2%, P < 0.001). There was no correlation between mean voltage or %low voltage during AF and paced rhythm. Complex fractionated electrograms were prevalent throughout all regions during AF, but did not correlate with %low voltage, fractionation, or slowed conduction during paced rhythm. CONCLUSION: Areas of CFE and low voltage recorded during AF frequently demonstrate normal atrial myocardial characteristics (normal conduction, electrograms, and voltage) during sinus rhythm. Therefore, AF CFE sites do not necessarily identify regions of an abnormal atrial substrate. However, this does not exclude the possibility that CFE might identify a focal driver or source occurring in a region of normal atrial myocardium.

Predictors of acute and long-term success of slow pathway ablation for atrioventricular nodal reentrant tachycardia: a single center series of 1,419 consecutive patients.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Slow pathway (SP) ablation is the first-line treatment approach with a high acute success rate and a low risk of inadvertent complete atrioventricular (AV) block. However, there is still some uncertainty as to the most appropriate procedural endpoints and the impact of these on risk of recurrence. We report the acute and long-term results of SP ablation in a large single-center consecutive series and analyze predictors of acute success and late recurrence. METHODS: The study included 1,448 consecutive procedures in 1,419 patients with AVNRT (mean age 49 ± 17 years, 66% women) who underwent SP ablation using a combined electrophysiologic and anatomic approach. Univariate and multivariate analysis was performed for potential predictors of acute success and late recurrence. RESULTS: Acute success was achieved in 98.1%. Transient (first, second, or third degree) AV block occurred during the procedure in 20 (1.41%) patients. One patient (0.07%) had persistent first-degree and transient second-degree AV block after ablation and underwent pacemaker implant at day 21. Of the 1,391 patients with successful ablation, 22 patients (1.5%) developed AVNRT recurrence during a follow-up period of 63 ± 38 months. The only independent predictor of reduced procedural success was the presence of atypical AVNRT (hazard ratio 3.1, P = 0.04). Independent predictors of AVNRT recurrence were age <20 years and female gender (hazard ratios 14.1 and 3.7, respectively). No significant difference in the incidence of late recurrence was observed in patients with or without residual slow-pathway conduction, or according to use of isoproterenol testing or general anesthesia. However, patients with a single echo with recurrence had a significantly larger echo window (median 85 ms) than those without (median 30 ms, P = 0.01). CONCLUSIONS: This study demonstrates in a large consecutive single-center series that SP ablation using radiofrequency energy is a highly effective procedure with an extremely low risk of inadvertent AV block and a low recurrence rate. We found that single-AV nodal echo beats represented a procedural endpoint that did not predict AVNRT recurrence but that a large echo window is associated with recurrence. Recurrence rates in this series were higher in young women, possibly reflecting a more conservative approach to ablation in this age group.

The effect of electrode density on the interpretation of atrial activation patterns in epicardial mapping of human persistent atrial fibrillation.

BACKGROUND: Mechanisms sustaining human persistent atrial fibrillation (AF) remain debated, with significant differences between high-density epicardial and global endocardial mapping studies. A key difference is the density of recording electrodes. OBJECTIVE: We aimed to determine the differences in the prevalence of different atrial activation patterns, and specifically in the prevalence of rotational activations, with varying densities of bipolar electrodes. METHODS: Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded using a triangular plaque (6.75 cm(2) area; 117 bipoles; 2.5-mm inter-bipole spacing) applied to the left atrial posterior wall or right atrial free wall. Dynamic wavefront mapping based on the timing of atrial electrograms was applied to 2 discrete 10-second AF segments. The spacing between bipolar electrode locations was increased from 2.5 × 3.5 mm in the horizontal and oblique directions to 5.0 × 3.5, 5.0 × 7.1, and 7.5 × 10.6 mm, with wavefront mapping repeated at each density. RESULTS: As density reduced, there was a significant change in relative proportions of the various activation patterns (F=3.69; P < .001). Simple broad wavefront activations became more prevalent (20% ± 8% to 54% ± 8%; P < .05) and complex patterns became less prevalent (48% ± 8% to 9% ± 8%; P < .05) with reducing density. The prevalence of rotational activity declined with bipole density, from median 5.0% (range 0.9%-12.1%) to 0% (range 0%-1.5%) (P = .03). The largest change occurred between inter-bipole spacings of 5.0 × 3.5 and 5.0 × 7.1 mm. CONCLUSION: Apparent activation patterns in persistent AF vary significantly with electrode density. Low density underestimates the prevalence of complex and rotational patterns. The largest difference occurs between an inter-bipole spacing of 5.0 × 3.5 and a spacing of 5.0 × 7.1 mm. This may have important implications for mapping technology design.

Remodeling of sinus node function in patients with congestive heart failure: reduction in sinus node reserve.

BACKGROUND: Experimental and clinical studies have demonstrated diffuse atrial remodeling in congestive heart failure (CHF). We hypothesized that patients with CHF would demonstrate derangement of sinus node function. METHODS AND RESULTS: Eighteen patients with symptomatic CHF (left ventricular ejection fraction, 26+/-5%) and 18 age-matched control subjects were studied. Under autonomic blockade, the following were evaluated: intrinsic sinus cycle length, corrected sinus node recovery time (CSNRT), sinoatrial conduction time, number and duration of fractionated electograms or double potentials along the crista terminalis, and location of the earliest sinus activity. Electroanatomic mapping was performed to evaluate the location and nature of the sinus node complex, to characterize sinoatrial propagation, and to evaluate conduction abnormalities and voltage amplitude along the crista terminalis. Patients with CHF demonstrated the following findings compared with age-matched control subjects: prolongation of the intrinsic sinus cycle length (P=0.005), prolongation of CSNRT (P<0.0001), caudal localization of sinus activity both during sinus rhythm (P=0.03) and after pacing (P=0.002), prolongation of sinoatrial conduction time (P=0.02), greater number (P<0.0001) and duration (P<0.0001) of fractionated electrograms or double potentials along the crista terminalis, loss of voltage amplitude along the crista terminalis (P=0.02), and abnormal and circuitous propagation of the sinus impulse. CONCLUSIONS: This study demonstrates that patients with CHF have significant sinus node remodeling characterized by anatomic and structural changes along the crista terminalis with a reduction in functional sinus node reserve. This finding may have implications for the development of clinical bradycardia in CHF and for the use of negatively chronotropic agents and pacing in this condition.

Effect of chronic right atrial stretch on atrial electrical remodeling in patients with an atrial septal defect.

BACKGROUND: Adults with an atrial septal defect (ASD) frequently develop late atrial arrhythmias. We sought to characterize the pattern and persistence of atrial electrical remodeling caused by chronic right atrial (RA) stretch in this group. METHODS AND RESULTS: Thirteen ASD patients without atrial arrhythmia (42+/-10 years old; RA volume, 65+/-16 mL) and 17 normal control subjects (44+/-11 years old; RA volume, 38+/-8 mL) had electrophysiological study to measure (1) atrial effective refractory period (AERP) from the low lateral/high lateral/high septal RA and distal coronary sinus (CS), (2) dispersion of AERP, (3) lateral-RA and CS conduction time during constant pacing, (4) conduction delay across the crista terminalis measuring the number of crista catheter bipoles (0-10) recording discrete double potentials during pacing, (5) corrected sinus node recovery time, and (6) P-wave duration. After ASD closure (8.3+/-5.6 months), follow-up echo studies (n=12) and electrophysiological study (n=4) were performed. The low-lateral AERP, P-wave duration, sinus node recovery time, and extent of conduction delay across the crista terminalis were significantly greater in ASD patients. No differences were found for other measured electrophysiological study parameters. At follow-up, there was incomplete resolution of RA volume (47+/-12 mL; P<0.01 versus before surgery), a trend toward shortening of the AERP at the lateral RA and an increase at the distal CS and high septal RA, but persisting extensive, widely split crista double potentials. CONCLUSIONS: Chronic RA stretch because of ASD causes electrical remodeling with modest increases in RA ERP, conduction delay at the crista terminalis, and sinus node dysfunction. Conduction delay at the crista terminalis persists beyond ASD closure and may contribute to the long-term atrial arrhythmia substrate in this condition.

Electrical remodeling of the atria in congestive heart failure: electrophysiological and electroanatomic mapping in humans.

BACKGROUND: Atrial fibrillation (AF) frequently complicates congestive heart failure (CHF). However, the electrophysiological substrate for AF in humans with CHF remains unknown. We evaluated the electrophysiological and electroanatomic characteristics of the atria in patients with CHF. METHODS AND RESULTS: Twenty-one patients (aged 53.7+/-13.6 years) with symptomatic CHF (left ventricular ejection fraction 25.5+/-6.0%) and 21 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (LRA), high septal right atrium, and distal coronary sinus (CS); conduction time along the CS and LRA; corrected sinus node recovery times; P-wave duration; and conduction at the crista terminalis. In a subset, electroanatomic mapping was performed to determine atrial activation, regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with CHF demonstrated an increase in atrial ERP with no change in the heterogeneity of refractoriness, an increase of atrial conduction time along the LRA and the CS, prolongation of the P-wave duration and corrected sinus node recovery times, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated regional conduction slowing with a greater number of electrograms with fractionation or double potentials, associated with areas of low voltage and electrical silence (scar). Patients with CHF demonstrated an increased propensity for AF with single extrastimuli, and induced AF was more often sustained. CONCLUSIONS: Atrial remodeling due to CHF is characterized by structural changes, abnormalities of conduction, sinus node dysfunction, and increased refractoriness. These abnormalities may be responsible in part for the increased propensity for AF in CHF.

Electrophysiological and electroanatomic characterization of the atria in sinus node disease: evidence of diffuse atrial remodeling.

BACKGROUND: The normal sinus pacemaker complex is an extensive structure within the right atrium. We hypothesized that patients with sinus node disease (SND) would have evidence of diffuse atrial abnormalities. METHODS AND RESULTS: Sixteen patients with symptomatic SND and 16 age-matched controls were studied. The following were evaluated: effective refractory periods (ERPs) from the high and low lateral right atrium (RA), high septal RA, and distal coronary sinus (CS); conduction time along the CS and lateral RA; P-wave duration; and conduction at the crista terminalis. Electroanatomic mapping was performed to define the sinus node complex and determine regional conduction velocity, double potentials, fractionated electrograms, regional voltage, and areas of electrical silence. Patients with SND demonstrated significant increase in atrial ERP at all right atrial sites, increased atrial conduction time along the lateral RA and CS, prolongation of the P-wave duration, and greater number and duration of double potentials along the crista terminalis. Electroanatomic mapping demonstrated the sinus node complex in SND to be more often unicentric, localized to the low crista terminalis at the site of the largest residual voltage amplitude. There was significant regional conduction slowing with double potentials and fractionation associated with areas of low voltage and electrical silence (or scar). CONCLUSIONS: SND is associated with diffuse atrial remodeling characterized by structural change, conduction abnormalities, and increased right atrial refractoriness. There was a change in the nature of sinus pacemaker activity with loss of the normal multicentric pattern of activation, caudal shift of the pacemaker complex, and abnormal and circuitous conduction around lines of conduction block.

Reversal of atrial mechanical stunning after cardioversion of atrial arrhythmias: implications for the mechanisms of tachycardia-mediated atrial cardiomyopathy.

BACKGROUND: Atrial mechanical stunning develops on termination of chronic atrial arrhythmias and is implicated in the genesis of thromboembolic complications after cardioversion. The mechanisms responsible for atrial mechanical stunning are unknown. The effects of atrial rate, isoproterenol, and calcium on atrial mechanical function in patients with atrial stunning have not been evaluated, and it is not known if atrial stunning can be reversed. METHODS AND RESULTS: Thirty-five patients with chronic atrial flutter (AFL) undergoing radiofrequency ablation were studied. Fifteen patients in sinus rhythm undergoing ablation for paroxysmal AFL were studied as control for effects of the procedure. Left atrial appendage emptying velocities (LAAEVs) and spontaneous echocardiographic contrast (LASEC) were assessed by transesophageal echocardiography during AFL, after reversion to sinus rhythm, during atrial pacing at cycle lengths of 750 to 250 ms, after a postpacing pause, and with isoproterenol or calcium. With termination of AFL, LAAEV decreased from 59.0+/-3.7 cm/s to 18.8+/-1.4 cm/s (P<0.0001) and LASEC grade increased from 0.9+/-0.1 to 2.2+/-0.2 (P<0.0001). Pacing increased LAAEV to a maximum of 38.4+/-3.2 cm/s (P<0.0001) and reduced LASEC grade to 1.9+/-0.2 (P=0.005). Isoproterenol and calcium reversed atrial mechanical stunning with LAAEV increasing to 89.3+/-12.6 cm/s (P=0.0007) and 50.2+/-10.5 cm/s (P=0.005), respectively, and LASEC grade decreasing to 0.2+/-0.1 (P=0.001) and 1.4+/-0.2 (P=0.01), respectively. The postpacing pause increased LAAEV to 69.3+/-3.7 cm/s (P<0.0001). No change in LAAEV was observed in the paroxysmal AFL group. CONCLUSION: Atrial mechanical stunning can be reversed by pacing at increased rates and through the administration of isoproterenol or calcium. These findings suggest a functional contractile apparatus in the mechanically remodeled atrium as a result of chronic atrial flutter.

Electrophysiologic and electroanatomic changes in the human atrium associated with age.

OBJECTIVES: The purpose of this study was to characterize the pattern of atrial remodeling seen with human aging. BACKGROUND: Atrial fibrillation (AF) occurs in 3% to 4% of the population over 65 years of age. It is associated with thromboembolic complications, worsening heart failure, and increased mortality, yet the electrical and structural remodeling that occurs with human aging remains unknown. METHODS: Thirteen patients (66.4 +/- 1.7 years) > or =60 years (group A), 13 patients (50 +/- 2.1 years) age 31 to 59 years (group B), and 15 patients (24.7 +/- 1.0 years) < or =30 years (group C) underwent conventional electrophysiologic studies and electroanatomic mapping. We measured atrial refractoriness (ERP) at the distal coronary sinus (CS); low and high lateral right atrium (LRA) and the high septal right atrium at 600, 500, and 400 ms; maximum corrected sinus node recovery time (CSNRT); P-wave duration (PWD); conduction time (CT) along the CS and LRA; and discrete double potentials (DP) along the crista. RESULTS: Aging was associated with an increase in atrial ERP, prolonged CT along the CS, increased PWD and CSNRT. There was no significant change in dispersion of refractoriness or rate adaptation. Electroanatomic mapping revealed diffuse areas of low voltage with regional conduction slowing. Both techniques demonstrated a greater number of DPs and fractionated signals along the crista terminalis with aging. CONCLUSIONS: Aging is associated with regional conduction slowing, anatomically determined conduction delay at the crista, and structural changes that include areas of low voltage. In addition, impairment of sinus node function and an increase in atrial ERP occurred with aging. This electrical and structural remodeling may explain the increased propensity to AF with aging.

Scar-related right atrial macroreentrant tachycardia in patients without prior atrial surgery: electroanatomic characterization and ablation outcome.

BACKGROUND: Few descriptions of right atrial macroreentrant atrial tachycardia involving regions of spontaneous "scar" have been reported. OBJECTIVES: We describe the electrocardiographic, electrophysiologic, and electroanatomic characteristics of an unusual RA macroreentrant atrial tachycardia in eight patients with spontaneous RA scarring. METHODS: Eight of 286 patients with macroreentrant atrial tachycardia treated with radiofrequency ablation had RA spontaneous scarring and underwent conventional electrophysiologic studies and electroanatomic mapping. RESULTS: Eight patients (age 53 +/- 12 years) had symptoms for 58 +/- 62 months and had not responded to 2.5 +/- 0.8 antiarrhythmic drugs and 1.0 +/- 0.9 DC cardioversions. All patients had overall normal systolic function, and five had mild atrial enlargement. Scarring was present in the posterolateral wall extending from the crista terminalis toward the tricuspid annulus. The proportion of RA classified as scar was 31% +/- 14% (range 11%-46%). Stable circuits were around scar in seven patients, through a "channel" within the scar in four, and typical cavotricuspid isthmus-dependent flutter in five. Radiofrequency ablation sites included the cavotricuspid isthmus; between the inferior vena cava, superior vena cava, or crista terminalis and scar; or a channel in the scar. ECG morphology of the RA free wall tachycardias varied, depending upon whether cavotricuspid isthmus block was present. Radiofrequency ablation of all inducible circuits was successful in six patients and of all clinical circuits in seven. At follow-up of 20 +/- 13 months, six patients are free from macroreentrant atrial tachycardia, one has infrequent nonsustained macroreentrant atrial tachycardia, and one is controlled with previously ineffective medication. Five had sinus node dysfunction requiring permanent pacemaker implant. CONCLUSIONS: Extensive spontaneous scarring of the RA is an unusual cause of macroreentrant atrial tachycardias, both cavotricuspid isthmus dependent and independent in the same patient. Radiofrequency ablation is an effective treatment. Sinus node dysfunction requiring permanent pacemaker is common. The cause is unknown.

Temporal Stability of Rotors and Atrial Activation Patterns in Persistent Human Atrial Fibrillation: A High-Density Epicardial Mapping Study of Prolonged Recordings.

OBJECTIVES: This study aimed to determine the spatiotemporal stability of rotors and other atrial activation patterns over 10 min in longstanding, persistent AF, along with the relationship of rotors to short cycle-length (CL) activity. BACKGROUND: The prevalence, stability, and mechanistic importance of rotors in human atrial fibrillation (AF) remain unclear. METHODS: Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded over 10 min using a triangular plaque (area: 6.75 cm2; 117 bipoles; spacing: 2.5 mm) applied to the left atrial posterior wall (n = 9) and the right atrial free wall (n = 4). Activations were identified throughout 6 discrete 10-s segments of AF spanning 10 min, and dynamic activation mapping was performed. The distributions of 4,557 generated activation patterns within each mapped region were compared between the 6 segments. RESULTS: The dominant activation pattern was the simultaneous presence of multiple narrow wave fronts (26%). Twelve percent of activations represented transient rotors, seen in 85% of mapped regions with a median duration of 3 rotations. A total of 87% were centered on an area of short CL activity (<100 ms), although such activity had a positive predictive value for rotors of only 0.12. The distribution of activation patterns and wave-front directionality were highly stable over time, with a single dominant pattern within a 10-s AF segment recurring across all 6 segments in 62% of mapped regions. CONCLUSIONS: In patients with longstanding, persistent AF, activation patterns are spatiotemporally stable over 10 min. Transient rotors can be demonstrated in the majority of mapped regions, are spatiotemporally associated with short CL activity, and, when recurrent, demonstrate anatomical determinism.

Relationship between the electrocardiographic atrial fibrillation cycle length and left atrial remodeling: a detailed electroanatomic mapping study.

BACKGROUND/OBJECTIVE: The purpose of this study was to characterize the association between the extent of left atrial electroanatomic remodeling in atrial fibrillation and the atrial fibrillation cycle length derived from lead V1 of the surface ECG (V1AFCL). METHODS: Twenty-three patients in atrial fibrillation (AF) who presented for AF ablation underwent detailed electroanatomic mapping of the left atrium. The digital 12-lead ECG was exported for offline analysis, with signal filtering and QRST subtraction used to reveal the fibrillatory baseline in lead V1. Mean V1AFCL was determined by direct annotation of the fibrillatory baseline, and the corresponding dominant V1AFCL was determined by Fourier transformation to derive the dominant frequency from the frequency power spectrum. The simultaneous AFCL from proximal and distal coronary sinus recordings was determined using the same methods. The strength of the association between various left atrial remodeling variables and V1AFCL was determined. RESULTS: The 2 methods of deriving V1AFCL and intracardiac AFCL were found to produce highly equivalent results. V1AFCL showed significant correlation with intracardiac AFCL derived from both proximal and distal coronary sinus recordings. A longer V1AFCL was associated with slower left atrial conduction velocity and greater signal complexity but not with other remodeling variables, including left atrial size, atrial refractoriness, and mean endocardial voltage. CONCLUSION: A longer atrial fibrillatory cycle length in surface ECG lead V1 is significantly associated with parameters of more advanced left atrial electroanatomic remodeling, specifically slower atrial conduction and more extensive electrogram fractionation.