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Jasbir Sra

Publications and source records attributed to Jasbir Sra.

At least 19 recordsLinked to original sources
PubMed2006

Registration of 3D computed tomographic images with interventional systems: implications for catheter ablation of atrial fibrillation.

Despite the great promise catheter ablation offers in the treatment of complex arrhythmias such as atrial fibrillation (AF), long procedure times and somewhat suboptimal results hinder the widespread use of this technique. As fluoroscopy does not provide contrast differentiation between the area of interest and the surrounding structures, there is a lack of proper intra procedure image guidance. Segmentation of anatomical structures such as the left atrium (LA) can be performed using images obtained with modalities such as computed tomography (CT). However, unlike the cardiac mapping systems, these imaging systems do not track catheters in real time. This review addresses the evolving concept of image registration to deliver therapy in cardiac arrhythmias.

Atrial Fibrillation↗
PubMed2006

Posterior left atrial-esophageal relationship throughout the cardiac cycle.

BACKGROUND: Radiofrequency energy delivered throughout the cardiac cycle has the potential to cause thermal injury to the esophagus if the anatomical relationship between the posterior left atrium and the esophagus changes during cardiac motion. OBJECTIVE: To assess the posterior left atrial-esophageal relationship throughout the cardiac cycle. METHODS: In this study, the anatomical relationship between the posterior left atrium and the esophagus was assessed throughout the cardiac cycle in 10 consecutive patients. All patients underwent contrast-enhanced, ECG-gated CT scanning. Left atrial volumes and the esophageal structure were generated from the reconstructed data at 10 phases of the cardiac cycle from 5% to 95% of the R-R interval. The posterior left atrial-esophageal anatomical relationship was measured at four levels, the superior pulmonary vein ostial site, and the upper, mid and lower left atrium. RESULTS: There were significant variations in the left atrial-esophageal relationship in the 10 patients. The relative movement between the esophagus and the posterior left atrium throughout the cardiac cycle in the anteroposterior and right-to-left orientations was 0.55 +/- 0.99 mm and 0.60 +/- 1.02 mm (95% confidence interval, 2.03 and 1.98 respectively). CONCLUSIONS: Under normal conditions, there is little change in the anatomical relationship between the posterior left atrium and the esophagus during the entire cardiac cycle. However, due to the interpatient variability at the esophageal location, identification of esophageal location may help prevent complications during catheter ablation procedures involving the left atrium.

Adult↗
PubMed2006

Combined use of 1C and III agents for highly symptomatic, refractory atrial fibrillation.

BACKGROUND: Despite advances in non-pharmacologic therapy for atrial fibrillation (AF), some patients remain highly refractory. OBJECTIVE: We report our experience with the unique combined use of 1C and III agents in patients with highly refractory paroxysmal atrial fibrillation. MATERIALS AND METHODS: Six patients with symptomatic AF (three persistent) were selected after failing multiple antiarrhythmic medications and radiofrequency ablation. They were started on flecainide or propafenone and sotalol or dofetilide during three days of inpatient monitoring. No patient had coronary artery disease. All patients had loop recorder follow-up and ECG recordings during clinic visits for a mean follow-up of 9 +/- 11 months. RESULTS: After therapy, all patients had complete, sustained control of their symptoms with no evidence of AF or proarrhythmia on monitoring. One patient had recurrence of AF after stopping sotalol and was started back on the drug with complete control. CONCLUSIONS: Combined therapy with a 1C and III agent may be an effective alternative for the treatment of selective, highly refractory AF. Careful patient selection and hospitalization for initiation is necessary to minimize potential proarrhythmic effects. As this is a short-term therapy, further study is needed to assess the extent of efficacy in a larger number of patients.

Adult↗
PubMed2005

Registration of three-dimensional left atrial computed tomographic images with projection images obtained using fluoroscopy.

BACKGROUND: Anatomic structures such as the left atrium and the pulmonary veins (PVs) are not delineated by fluoroscopy because there is no contrast differentiation between them and the surrounding anatomy. Representation of an anatomic structure via a 3D model obtained from computed tomography (CT) imaging and subsequent projection of these images over the fluoroscopy system may help in navigation of the mapping and ablation catheter to the appropriate sites during electrophysiology procedures. METHODS AND RESULTS: In this feasibility study, in vitro experiments were performed with a plastic heart model (phantom) with 2 catheters or radiopaque platinum beads placed in the phantom at the time of CT imaging and fluoroscopy. Subsequently, 20 consecutive patients underwent contrast-enhanced, ECG-gated CT scanning. Left atrial volumes were generated from the reconstructed data at &75% of the R-R interval during the cardiac cycle. Similarly, the superior vena cava and the coronary sinus were also reconstructed from these images. During the electrophysiology procedure, digital records (cine sequences) were obtained. Using predetermined algorithms, both the phantom model and the patients' 3D left atrial models derived from the CT were registered with projection images of fluoroscopy. Registration was performed with a transformation that linked the superior vena cava and the coronary sinus from the CT model with a catheter placed inside the coronary sinus via the superior vena cava. Registration was successfully accomplished with the plastic phantom and in all 20 patients. Registration accuracy was assessed in the phantom by assessing the overlapping beads seen both in the CT and the fluoroscopy images. The mean registration error was 1.4 mm (range 0.9 to 2.3 mm). Accuracy of the registered images was assessed in patients with recordings from a basket catheter placed sequentially in the superior PVs and by injecting contrast into the PVs to assess overlapping of contrast-filled PVs with the corresponding vessels on the registered images. The images could be calibrated quite accurately. Any rotational error, which was usually minor, could be corrected by rotating the images as needed. CONCLUSIONS: Registration of 3D models of the left atrium and PVs with fluoroscopic images of the same is feasible and could enable appropriate navigation and localization of the mapping and ablation catheter during procedures such as atrial fibrillation ablation.

Aged↗
PubMed2005

Atrial tachycardia arising from the coronary sinus musculature: electrophysiological characteristics and long-term outcomes of radiofrequency ablation.

OBJECTIVES: We sought to describe the electrophysiological features and long-term outcome after radiofrequency catheter ablation (RFCA) of atrial tachycardia (AT) arising from the coronary sinus (CS) musculature. BACKGROUND: Atrial tachycardia requiring RFCA deep within the CS has been described in isolated case reports. However, the mechanism and exact site of origin of this tachycardia have not been well elucidated. METHODS: The study included 8 patients (5 men) of a consecutive series of 283 patients undergoing RFCA for focal AT. RESULTS: In sinus rhythm, a discrete potential (P) was noted after the CS atrial electrogram and during tachycardia, the CS (P) preceded the surface P-wave by 30 to 50 ms. The CS (P) always preceded the earliest electrogram in the left atrium (LA). Three-dimensional electroanatomical mapping was available in four patients, and in one case it showed earliest activation in the CS with rapid spread to the proximal CS and then to the LA. Ablation of the AT initially attempted from the earliest site in the LA in three patients was unsuccessful. In all patients the tachycardia was safely and successfully ablated at a site 3.6 cm within the CS. There has been no recurrence over a follow-up of 37 +/- 13 months. CONCLUSIONS: Focal AT emanating deep within the CS musculature can be recognized by a discrete potential associated with the CS atrial signal both during sinus rhythm and tachycardia. Long-term success without complications can be accomplished by ablating within the CS in close proximity to the CS (P).

Adolescent↗
PubMed2005

Catheter location, tracking, cardiac chamber geometry creation, and ablation using cutaneous patches.

OBJECTIVE: The ability to construct a three-dimensional (3-D) surface model of the endocardium and track the location of catheters within a cardiac chamber, using only cutaneous patches, would be a useful advancement in treating arrhythmias. We tested the feasibility of such a system, Ensite NavX (Endocardial Solutions, Inc., St. Paul, MN, USA), in patients undergoing catheter ablation for SVTs. METHODS: Sixteen patients with 20 arrhythmias undergoing ablation were selected. Skin electrode patches were placed on the chest to create a 3-D coordinate system. A low-amplitude, 5.7 kHz signal emitted from the patches was received by conventional catheters positioned in the heart. Catheter location was determined by measuring the field strength received by the catheters. Location points were successively acquired while catheters were moved throughout the chamber. This information was collected and processed by a workstation to create a detailed 3-D model of the endocardial surface. Anatomic landmarks were labeled on the model as the mapping catheter was navigated. 3-D cardiac chamber geometry reconstruction, landmark labeling, and real time catheter tracking were performed successfully in all patients. Up to six catheters, with a total of up to 26 intracardiac electrodes, were tracked simultaneously. RESULTS: Constructed geometries, including major vessels and valves, correlated closely with traditional anatomic models as well as intracardiac recordings and fluoroscopic images. CONCLUSIONS: Real-time catheter tracking and 3-D cardiac chamber model construction is feasible using cutaneous patches and conventional catheters. This approach may be useful in the treatment of patients with cardiac arrhythmias where ablation therapy is primarily anatomically based.

Adult↗
PubMed2005

Feasibility and validation of registration of three-dimensional left atrial models derived from computed tomography with a noncontact cardiac mapping system.

OBJECTIVES: The purpose of this study was to determine the feasibility and assess the validity of registering three-dimensional (3D) models from computed tomographic (CT) images using a cardiac mapping system. BACKGROUND: Registration of 3D anatomic models with an interventional system could help identify and navigate mapping and ablation catheters over a complex structure such as the left atrium (LA). METHODS: ECG-gated, contrast-enhanced cardiac CT imaging was performed in 14 patients with atrial fibrillation. Segmentation was used to create 3D models of the LA. The 3D models were registered with the mapping system using a series of fiducial points. Registration was accomplished retrospectively in the first 10 patients, and catheter navigation was visualized from recorded data. In the final four patients, registration was accomplished in real time during electrophysiologic study. The mapping catheter position, as it was navigated inside the LA, was applied to the registered model in real time. For the validation study, temporary pacing leads were implanted in the LA of 10 dogs. Following this, CT scanning, segmentation, LA model importation, and registration was described previously. After registration, a mapping catheter was positioned at the site of each buried lead according to the registered model with no fluoroscopic guidance. A radiofrequency lesion was created at this location, and the dog was sacrificed, the heart removed and stained, and the distance between the buried lead and the lesion measured. RESULTS: During the feasibility study, the location of the catheter in the registered model correlated with fluoroscopy, angiography, and intracardiac electrograms. LA endocardial potentials during sinus rhythm and any premature atrial contractions also were successfully delineated over the registered models. In the validation study, the mean target registration error was 2.0 +/- 3.6 mm. CONCLUSIONS: Registration of CT-derived 3D models of the LA using a cardiac mapping system is feasible and accurate.

Animals↗
PubMed2004

The implantable cardioverter defibrillator: technology, indications, and impact on cardiovascular survival.

Since the introduction of the implantable cardioverter defibrillator (ICD) for the management of patients with high risk of arrhythmic SCD, there has been increasing use of this device. Its basic promise to effectively terminate ventricular tachycardia (VT)-ventricular fibrillation (VF) has been repeatedly met. In several randomized trials, the ICD has been shown to be superior to conventional anti-arrhythmic therapy, both in patients with documented VT-VF (secondary prevention) and those with high risk such as left ventricular ejection fraction and no prior sustained VT-VF (primary prevention). In both groups, the ICD showed overall and cardiac mortality reduction. The device now can more accurately detect VT-VF and differentiate these from other arrhythmias through a series of algorithms and direct-chamber sensing. Therapy options include painless antitachycardia pacing, low-energy cardioversion, and high-energy defibrillation. The technique implant is now simple as a pacemaker with one lead attached to an active (hot) can functioning as the other electrode. Among other improvements is its weight, volume, multiprogrammability, and storage of information,dual-chamber pacing and sensing, dual-chamber defibrillation, and addition of biventricular pacing for cardiac synchronization. It is anticipated that further improvement in ICD technology will take place and the list of indications will grow.

Algorithms↗