Bobby John

Electrical remodelling of the left and right atria due to rheumatic mitral stenosis

AIMS To characterize the atrial remodelling in mitral stenosis (MS). METHODS AND RESULTS Twenty-four patients with severe MS undergoing commissurotomy and 24 controls were studied. Electrophysiological evaluation was performed in 12 patients in each group by positioning multi-electrode catheters in both atria to determine the following: effective refractory period (ERP) at 10 sites at 600 and 450 ms; conduction time; conduction delay at the crista terminalis (CT); and vulnerability for atrial fibrillation (AF). P-wave duration (PWD) was determined on the surface ECG. In the remaining 12 patients in each group, electroanatomic maps of both atria were created to determine conduction velocity and identify regions of low voltage and electrical silence. Patients with MS had larger left atria (LA) (P < 0.0001); prolonged PWD (P = 0.0007); prolonged ERP in both LA (P < 0.0001) and right atria (RA) (P < 0.0001); reduced conduction velocity in the LA (P = 0.009) and RA (P < 0.0001); greater number (P < 0.0001) and duration (P< 0.0001) of bipoles along the CT with delayed conduction; lower atrial voltage in the LA (P < 0.0001) and RA (P < 0.0001); and more frequent electrical scar (P = 0.001) compared with controls. Five of twelve with MS and none of the controls developed AF with extra-stimulus (P = 0.02). CONCLUSION Atrial remodelling in MS is characterized by LA enlargement, loss of myocardium, and scarring associated with widespread and site-specific conduction abnormalities and no change or an increase in ERP. These abnormalities were associated with a heightened inducibility of AF.

High-Density Mapping of Atrial Fibrillation in Humans: Relationship Between High-Frequency Activation and Electrogram Fractionation

Introduction: Sites of complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) have been implicated in maintaining atrial fibrillation (AF); however, their relationship is poorly understood.

Left atrial remodeling in patients with atrial septal defects

BACKGROUND Information regarding left atrial (LA) substrate in conditions predisposing to atrial fibrillation (AF) is limited. OBJECTIVE This study sought to characterize the left atrial remodeling that results from chronic atrial stretch caused by atrial septal defect (ASD). METHODS Eleven patients with hemodynamically significant ASDs and 12 control subjects were studied. The following were evaluated using multipolar catheters: effective refractory period (ERP) at 7 sites, P-wave duration (PWD), conduction time, and inducibility of AF. LA electroanatomic maps were created to determine atrial activation, and regional conduction and voltage abnormalities. RESULTS Patients with ASDs showed significant LA enlargement (P <0.001), unchanged or prolonged atrial ERPs, increase in LA conduction times (P = 0.03), prolonged PWD (P <0.001), regional conduction slowing (P <0.001), greater number of double potentials or fractionated electrograms (P <0.0001), reduced atrial voltage (P <0.001), and more frequent electrical scar (P = 0.005) compared with control subjects. In addition, patients with ASDs showed a greater propensity for sustained AF with single extrastimuli (4 of 11 vs. 0 of 12, P = 0.04). CONCLUSION ASDs are associated with chronic left atrial stretch, which results in remodeling characterized by LA enlargement, loss of myocardium, and electrical scar that results in widespread conduction abnormalities but with no change or an increase in ERP. These abnormalities were associated with a greater propensity for sustained AF.

The Effect of Electrogram Duration on Quantification of Complex Fractionated Atrial Electrograms and Dominant Frequency

Introduction: Sites of complex fractionated atrial electrograms (CFAEs) and highest dominant frequency (DF) have been proposed as critical regions maintaining atrial fibrillation (AF). This study aimed to determine the minimum electrogram recording duration that accurately characterizes CFAE or DF sites for ablation without unduly lengthening the procedure.

Reverse Remodeling of the Atria After Treatment of Chronic Stretch in Humans: Implications for the Atrial Fibrillation Substrate

OBJECTIVES The aim of this report was to study the effect of chronic stretch reversal on the electrophysiological characteristics of the atria in humans. BACKGROUND Atrial stretch is an important determinant for atrial fibrillation. Whether relief of stretch reverses the substrate predisposed to atrial fibrillation is unknown. METHODS Twenty-one patients with mitral stenosis undergoing mitral commissurotomy (MC) were studied before and after intervention. Catheters were placed at multiple sites in the right atrium (RA) and sequentially within the left atrium (LA) to determine: effective refractory period (ERP) at 10 sites (600 and 450 ms) and P-wave duration (PWD). Bi-atrial electroanatomic maps determined conduction velocity (CV) and voltage. In 14 patients, RA studies were repeated >or=6 months after MC. RESULTS Immediately after MC, there was significant increase in mitral valve area (2.1 +/- 0.2 cm(2), p < 0.0001) with decrease in LA (23 +/- 7 mm Hg to 10 +/- 4 mm Hg, p < 0.0001) and pulmonary arterial pressures (38 +/- 16 mm Hg to 27 +/- 12 mm Hg, p < 0.0001) and LA volume (75 +/- 20 ml to 52 +/- 18 ml, p < 0.0001). This was associated with reduction in PWD (139 +/- 19 ms to 135 +/- 20 ms, p = 0.047), increase in CV (LA: 1.3 +/- 0.3 mm/ms to 1.7 +/- 0.2 mm/ms, p = 0.006; and RA: 1.0 +/- 0.1 mm/ms to 1.3 +/- 0.3 mm/ms, p = 0.002) and voltage (LA: 1.7 +/- 0.6 mV to 2.5 +/- 1.0 mV, p = 0.005; and RA: 1.8 +/- 0.6 mV to 2.2 +/- 0.7 mV, p = 0.09), and no change in ERP. Late after MC, mitral valve area remained at 2.1 +/- 0.3 cm(2) (p = 0.7) but with further decrease in PWD (113 +/- 19 ms, p = 0.04) and RA ERP (at 600 ms, p < 0.0001), with increase in CV (1.0 +/- 0.1 mm/ms to 1.3 +/- 0.2 mm/ms, p = 0.006) and voltage (1.8 +/- 0.7 mV to 2.8 +/- 0.6 mV, p = 0.002). CONCLUSIONS The atrial electrophysiologic and electroanatomic abnormalities that result from chronic stretch due to MS reverses after MC. These observations suggest that the substrate predisposing to atrial arrhythmias might be reversed.

Image integration using NavX fusion: Initial experience and validation

BACKGROUND Three-dimensional virtual anatomic navigation is increasingly used during mapping and ablation of complex arrhythmias. NavX Fusion software aims to mold the virtual anatomy to the patients computed tomography (CT) image; however, the accuracy and clinical usefulness of this system have not been reported. OBJECTIVE The purpose of this study was to assess the accuracy and describe the initial experience of CT image integration using NavX Fusion for atrial fibrillation ablation. METHODS This study consisted of 55 consecutive patients undergoing atrial fibrillation ablation using NavX Fusion navigation. Left atrial NavX geometries were compared to a corresponding CT for geometric match. Geometric match, expressed as the difference in millimeters between CT and NavX geometry, was calculated for the original geometry (GEO-1), field scaled and primary fused geometry (GEO-2), and final secondary fused geometry (GEO-3). Navigational accuracy was assessed by moving the catheter to 10 discrete anatomic sites and determining the distance between the catheter tip and the closest GEO-2, GEO-3, and CT surface. Fusion integration time and procedural and fluoroscopic durations were recorded to assess clinical usefulness. RESULTS GEO-1, GEO-2 and GEO-3 were associated with CT-GEO errors of 6.6+/-2.8 mm, 4.1+/-0.7 mm, 1.9+/-0.4 mm, respectively. Navigational accuracy was not significantly different for GEO-2, GEO-3, and CT at 3.4+/-1.6 mm to any surface. A significant (P < or =.001) inverse curvilinear relationship was present between case number and the time required for image integration (r(2) = 0.35) and the fluoroscopic time normalized for procedural duration (r(2) = 0.18). CONCLUSION Image integration using the NavX Fusion software is highly accurate and is associated with a progressive reduction in fluoroscopic time relative to procedural duration.

High‐Density Mapping of the Sinus Node in Humans: Role of Preferential Pathways and the Effect of Remodeling

Sinus Node Mapping. Introduction: The area of the functional sinus node complex exceeds that of the anatomical sinus node; however, reasons for this discrepancy are unknown. We aimed to characterize the functional sinus node complex in health and disease with high‐density simultaneous mapping.

Complications after posterior dislocation of the hip

Thirty-five consecutive patients with unilateral posterior dislocation of the hip were studied for complications at an average follow-up of 4.6 years (range 2–10 years). Thompson–Epstein type IV dislocation was most frequent (10/35), reflecting an increase in high-speed motor vehicles in the developing countries. It is also a severe injury that leads to a maximum number of complications, which include avascular necrosis, osteoarthosis, sciatic nerve injury and heterotrophic ossification. Avascular necrosis and osteoarthritis of the hip were observed maximally in type IV patients, even when reduction was achieved in less than twelve hours and may reflect the severity of initial injury. Heterotrophic ossification was observed in five of the ten patients with type IV dislocation and was associated with multiple attempts at reduction. Sciatic nerve injury did not recover completely in all cases, especially when reduction was delayed over twelve hours. Observing that the greatest numbers of complications were seen among patients with type IV dislocations, it may be prudent to warn such individuals about the likely prognosis at the outset, especially in today’s world when the demands and expectations are high.Résumé35 patients consécutifs présentant une luxation postérieure de la hanche ont été étudiés avec un recul moyen de 4,6 ans (2 à 10 ans). Les luxations de type 4 de Thompson–Epstein sont les plus fréquentes (10/35) et sont le reflet de l’augmentation de la vitesse des véhicules à moteur dans les pays développés. Il s’agit également de traumatismes sévères qui ont conduit la plupart du temps à des complications de nécroses avasculaires, de lésions dégénératives, de lésions du nerf sciatique et d’ossification hétérotopique. Ce sont les traumatismes sévères qui ont été à l’origine du maximum de complications. Les nécroses avasculaires et les arthroses de hanche sont surtout observées chez les patients de type IV, même si la réduction a été réalisée avant 12 heures. Les ossifications hétérotopique sont été observées chez 5 patients sur 10, notamment dans les luxations de type 4, les lésions du nerf sciatique n’ont jamais récupéré complètement surtout lorsque la réduction a été retardée après 12 heures. Il faut remarquer que le plus grand nombre de complications ont été observées chez les patients dont la luxation était de type IV. Il est plus prudent dans ce cas là de faire part du pronostic réservé à ces patients, d’autant plus que la demande et l’attente d’un résultat parfait est très importante dans le monde d’aujourd’hui.

Direction-dependent conduction in lone atrial fibrillation

BACKGROUND Patients with lone atrial fibrillation (AF) have an abnormal atrial substrate. OBJECTIVE The purpose of this study was to determine the role of direction-dependent conduction in patients with lone AF. METHODS Twenty-four patients with paroxysmal lone AF and 24 reference patients with left-sided accessory pathways were studied. Multipolar catheters placed at the lateral right atrium, crista terminalis, coronary sinus (CS), and left atrial roof were used to determine direction-dependent conduction characteristics. Biatrial electroanatomic maps were created during sinus rhythm and with distal CS pacing to characterize direction-dependent differences in conduction velocities, electrogram complexity, and voltage. RESULTS Differing wavefront directions caused changes in conduction velocity (P <.001), biatrial activation times (P <.001), electrogram fragmentation (P <.001), site-specific conduction delays (P <.001), and voltage (P <.001) in both lone AF and reference patients. These direction-dependent abnormalities were amplified in lone AF patients compared to reference patients, who exhibited greater slowing in conduction velocities (P = .02), prolongation of biatrial activation time (P = .04), increase in number (P <.001) and length (P <.001) of lines of conduction block, increase in proportion of fractionated electrograms (P <.001), and decrease in voltage (P = .03) during distal CS pacing compared to sinus rhythm. CONCLUSION This study demonstrates the marked direction-dependent conduction abnormalities present in patients with lone AF. These results provide further insights into the critical interplay between the underlying abnormal substrate and differing wavefront directions. The study suggests that direction-dependent conduction abnormalities may explain in part the greater arrhythmogenicity of ectopic triggers from the left atrium rather than the right atrium.

Characterization of Atrial Remodeling Studied Remote from Episodes of Typical Atrial Flutter

Atrial electrical remodeling has been shown after termination of atrial flutter (AFL); however, whether abnormalities persist beyond an arrhythmic episode is not known. We aimed to characterize the atrial substrate, remote from arrhythmia, in patients with typical AFL. We compared 20 patients, studied remote from episodes of typical AFL and without a history of atrial fibrillation, to 20 reference patients. Multipolar catheters placed at the lateral right atrium (RA), coronary sinus, crista terminalis, and septal RA measured the effective refractory period at 5 sites; conduction characteristics at the crista terminalis; and the conduction time along the lateral RA and coronary sinus. Electroanatomic right atrial maps were created to determine regional differences in voltage and conduction. Patients with AFL demonstrated the following compared to the reference patients: a larger right atrial volume (121 +/- 30 vs 83 +/- 24 ml, p = 0.005); a prolonged P-wave duration (122 +/- 18 vs 102 +/- 11 ms, p = 0.007); a longer right atrial activation time (107 +/- 23 vs 85 +/- 14 ms, p = 0.02); a prolonged conduction time along the lateral RA (67 +/- 4 vs 47 +/- 3 ms, p <0.001); a slower mean conduction velocity (1.2 +/- 0.2 vs 2.1 +/- 0.6 mm/ms, p <0.001); a greater proportion of fractionated electrographic findings (16 +/- 4% vs 10 +/- 6%, p = 0.006); more frequent abnormal electrographic findings at the crista terminalis (4.1 +/- 2.6 vs 1.0 +/- 1.1, p = 0.001); a prolonged corrected sinus node recovery time (318 +/- 71 vs 203 +/- 94 ms, p = 0.02); a trend toward greater effective refractory period (232 +/- 29 vs 213 +/- 12 ms, p = 0.06); and a lower voltage (2.1 +/- 0.5 vs 3.0 +/- 0.5 mV, p <0.001). In conclusion, studied remote from arrhythmia, patients with AFL demonstrated significant and diffuse atrial abnormalities characterized by structural changes, conduction abnormalities, and sinus node dysfunction. These persisting abnormalities characterize the substrate underlying typical AFL and may account for the subsequent development of atrial fibrillation.