A nonfluoroscopic catheter-based mapping technique to ablate focal ventricular tachycardia

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Non-invasive Characterization of Focal Arrhythmia with Electromechanical Wave Imaging in Vivo

There is currently no established method for the non-invasive characterization of arrhythmia and differentiation between endocardial and epicardial triggers at the point of care. Electromechanical wave imaging (EWI) is a novel ultrasound-based imaging technique based on time-domain transient strain estimation that can map and characterize electromechanical activation in the heart in vivo. The objectives of this initial feasibility study were to determine that EWI is capable of differentiating between endocardial and epicardial sources of focal rhythm and, as a proof-of-concept, that EWI could characterize focal arrhythmia in one patient with premature ventricular contractions (PVCs) before radiofrequency (RF) ablation treatment. First, validation of EWI for differentiation of surface of origin was performed in seven (n = 7) adult dogs using four epicardial and four endocardial pacing protocols. Second, one (n = 1) adult patient diagnosed with PVC was imaged with EWI before the scheduled RF ablation procedure, and EWI results were compared with mapping procedure results. In dogs, EWI was capable of detecting whether pacing was of endocardial or epicardial origin in six of seven cases (86% success rate). In the PVC patient, EWI correctly identified both regions and surface of origin, as confirmed by results from the electrical mapping obtained from the RF ablation procedure. These results reveal that EWI can map the electromechanical activation across the myocardium and indicate that EWI could serve as a valuable pre-treatment planning tool in the clinic.

Treatment of Ventricular Arrhythmias and Use of Implantable Cardioverter-Defibrillators to Improve Survival in Older Adult Patients with Cardiac Disease

Ventricular arrhythmia (VA) and sudden cardiac death (SCD) are well-recognized problems in the overall heart failure population, but treatment decisions can be more complex and nuanced in older patients. Sustained VA does not always lead to SCD, but identifies a higher risk population and may cause significant symptoms. Antiarrhythmic drugs (AAD) and catheter ablation are the mainstays for prevention of VA, but have not been shown to improve mortality. The value of implantable cardiac defibrillators (ICDs) may be influenced by patient age. This article discusses long-term treatment of VA and the use of ICDs in the elderly.

Non-invasive imaging of ventricular activation during pacing and arrhythmia: Methods and validation

Cardiovascular disease continued to be a leading killer world widely. Each year, about 400,000 cases of sudden cardiac arrest are reported in the U.S. alone. Clinically, radio-frequency ablative procedure has become widely applied in the treatment of ventricular arrhythmia. Non-invasive approaches have been demonstrated to be able to provide important information on the arrhythmogenesis and potentially assist in the clinical practice. In this work, we develop and validate a novel temporal sparse based imaging method, Cardiac Electrical Sparse Imaging (CESI). Computer simulation and animal validation results demonstrate that the CESI approach is capable of imaging with improved accuracy and robustness by exploiting the temporal sparse property underlying cellular electrophysiology. Overall, a CC of 0.8, RE of 0.2 and LE (localization error) of 7 mm has been achieved on human realistic simulation and good accuracy has been observed in canine simultaneous mapping studies. Also, the technique maintains full temporal resolution (RRE <; 0.04) in terms of the activation sequence under various disturbances and in various pathologies such as premature ventricular complex and ventricular tachycardia. Our promising results indicate the excellent performance of noninvasive imaging of cardiac activation under various arrhythmias, and its potential for aiding clinical management of lethal ventricular arrhythmia.

On the efficiency and accuracy of the single equivalent moving dipole method to identify sites of cardiac electrical activation

We have proposed an algorithm to guide radiofrequency catheter ablation procedures. This algorithm employs the single equivalent moving dipole (SEMD) to model cardiac electrical activity. The aim of this study is to investigate the optimal time instant during the cardiac cycle as well as the number of beats needed to accurately estimate the location of a pacing site. We have evaluated this algorithm by pacing the ventricular epicardial surface and inversely estimating the locations of pacing electrodes from the recorded body surface potentials. Two pacing electrode arrays were sutured on the right and left ventricular epicardial surfaces in swine. The hearts were paced by the electrodes sequentially at multiple rates (120-220 bpm), and body surface ECG signals from 64 leads were recorded for the SEMD estimation. We evaluated the combined error of the estimated interelectrode distance and SEMD direction at each time instant during the cardiac cycle, and found the error was minimum when the normalized root mean square (RMS n ) value of body surface ECG signals reached 15 % of its maximum value. The beat-to-beat variation of the SEMD locations was significantly reduced (p < 0.001) when estimated at 15 % RMS n compared to the earliest activation time (EAT). In addition, the 5-95 % interval of the estimated interelectrode distance error decreased exponentially as the number of beats used to estimate a median beat increased. When the number of beats was 4 or larger, the 5-95 % interval was smaller than 3.5 mm (the diameter of a commonly used catheter). In conclusion, the optimal time for the SEMD estimation is at 15 % of RMS n , and at that time instant a median beat estimated from 4 beats is associated with a beat-to-beat variability of the SEMD location that is appropriate for catheter ablation procedures.

Temporal Sparse Promoting Three Dimensional Imaging of Cardiac Activation

A new Cardiac Electrical Sparse Imaging (CESI) technique is proposed to image cardiac activation throughout the three-dimensional myocardium from body surface electrocardiogram (ECG) with the aid of individualized heart-torso geometry. The sparse property of cardiac electrical activity in the time domain is utilized in the temporal sparse promoting inverse solution, one formulated to achieve higher spatial-temporal resolution, stronger robustness and thus enhanced capability in imaging cardiac electrical activity. Computer simulations were carried out to evaluate the performance of this imaging method under various circumstances. A total of 12 single site pacing and 7 dual sites pacing simulations with artificial and the hospital recorded sensor noise were used to evaluate the accuracy and stability of the proposed method. Simulations with modeling error on heart-torso geometry and electrode-torso registration were also performed to evaluate the robustness of the technique. In addition to the computer simulations, the CESI algorithm was further evaluated using experimental data in an animal model where the noninvasively imaged activation sequences were compared with those measured with simultaneous intracardiac mapping. All of the CESI results were compared with conventional weighted minimum norm solutions. The present results show that CESI can image with better accuracy, stability and stronger robustness in both simulated and experimental circumstances. In sum, we have proposed a novel method for cardiac activation imaging, and our results suggest that the CESI has enhanced performance, and offers the potential to image the cardiac activation and to assist in the clinical management of ventricular arrhythmias.

Management of ventricular arrhythmias in structural heart disease

Ventricular arrhythmias (VA) are a source of significant morbidity and mortality in patients with structural heart disease (SHD). The advent of the implantable cardiac defibrillator (ICD) has had a positive effect on mortality, but the associated morbidity remains a significant problem. Modern treatment of VA has advanced far beyond medical therapy and includes strategies as simple as intelligent ICD programming and as complex as catheter ablation (CA). In these pages, the spectrum of management strategies will be discussed; from anti-arrhythmic drugs and ICD implantation and programming to CA and autonomic modulation. The focus of this review will be on strategies for secondary prevention of VA in patients with SHD, supported by clinical evidence for their utilization.

A method to noninvasively identify cardiac bioelectrical sources

BACKGROUND

We have introduced a method to guide radiofrequency catheter ablation (RCA) procedures that estimates the location of a catheter tip used to pace the ventricles and the target site for ablation using the single equivalent moving dipole (SEMD).

OBJECTIVE

To investigate the accuracy of this method in resolving epicardial and endocardial electrical sources.

METHODS

Two electrode arrays, each of nine pacing electrodes at known distances from each other, sutured on the left- and right-ventricular (LV and RV) epicardial surfaces of swine, were used to pace the heart at multiple rates, while body surface potentials from 64 sites were recorded and used to estimate the SEMD location. A similar approach was followed for pacing from catheters in the LV and RV.

RESULTS

The overall (RV & LV) error in estimating the interelectrode distance of adjacent epicardial electrodes was 0.38 ± 0.45 cm. The overall endocardial (RV & LV) interelectrode distance error, was 0.44 ± 0.26 cm. Heart rate did not significantly affect the error of the estimated SEMD location (P > 0.05). The guiding process error became progressively smaller as the SEMD approached an epicardial target site and close to the target, the overall absolute error was ∼ 0.28 cm. The estimated epicardial SEMD locations preserved their topology in image space with respect to their corresponding physical location of the epicardial electrodes.

CONCLUSION

The proposed algorithm suggests one can efficiently and accurately resolve epicardial electrical sources without the need of an imaging modality. In addition, the error in resolving these sources is sufficient to guide RCA procedures.

Ventricular arrhythmias: state of the art

The management of ventricular tachycardia and ventricular fibrillation in the cardiac intensive care unit can be complex. These arrhythmias have many triggers, including ischemia, sympathetic stimulation, and medication toxicities, as well as many different substrates, ranging from ischemic and nonischemic cardiomyopathies to rare genetic conditions such as Brugada syndrome and long QT syndrome. Different settings, such as congenital heart disease, postoperative ventricular arrhythmias, and ventricular assist devices, increase the complexity of management. This article reviews the variety of situations and cardiac conditions that give rise to ventricular arrhythmias, focusing on inpatient management strategies.

Non-fluoroscopic catheter-based mapping systems in cardiac electrophysiology--from approved clinical indications to novel research usage

BACKGROUND

During 20 years of development of catheter-based technologies in the management of cardiac arrhythmias, electrophysiological mapping/ablation systems have evolved from single-plane fluoroscopic mapping to three-dimensional (3-D) non-fluoroscopic computer-based mapping systems.

METHODS

Based on magnetic technology, the electro-anatomic CARTO mapping system can accurately correlate local electrograms with recording sites, by which the system can reconstruct 3-D maps with colour-coded electrophysiological information superimposed on the anatomy. Whereas the CARTO system is primarily designed for studying cardiac activation and not repolarisation, the system has been widely used in the diagnosis and ablation of cardiac arrhythmias and in the research of basic arrhythmic mechanisms.

RESULTS

In order to study cardiac repolarisation in vivo, an innovative method, the monophasic action potential (MAP) mapping technique, which integrates MAP recording with electroanatomical mapping, has recently been developed in our centre. Using the MAP technique, global sequence and dispersion of atrial/ventricular repolarisation have been evaluated in vivo in both experimental and clinical settings.

CONCLUSION

The innovative MAP technique provides unique research opportunities for in vivo studies of basic electrophysiological mechanisms.

Applicability of the Single Equivalent Moving Dipole Model in an Infinite Homogeneous Medium to Identify Cardiac Electrical Sources: A Computer Simulation Study in a Realistic Anatomic Geometry Torso Model

We have previously proposed an inverse algorithm for fitting potentials due to an arbitrary bio-electrical source to a single equivalent moving dipole (SEMD) model. The algorithm achieves fast identification of the SEMD parameters by employing a SEMD model embedded in an infinite homogeneous volume conductor. However, this may lead to systematic error in the identification of the SEMD parameters. In this paper, we investigate the accuracy of the algorithm in a realistic anatomic geometry torso model (forward problem). Specifically, we investigate the effect of measurement noise, dipole position and electrode configuration in the accuracy of the algorithm. The boundary element method was used to calculate the forward potential distribution at multiple electrode positions on the body surface due to a point dipole in the heart. We have found that the position and not the number of electrodes as well as the site of the origin of the arrhythmia in the heart have a significant effect on the accuracy of the inverse algorithm, while the measurement noise does not. Finally, we have shown that the inverse algorithm preserves the topology of the source distribution in the heart, thus potentially allowing the cardiac electrophysiologist to efficiently and accurately guide the tip of the catheter to the ablation site.

Advances in electrical and mechanical cardiac mapping

Cardiac mapping--recording cardiac activity during electrophysiological testing--has evolved into an indispensable tool in studying the cardiac excitation process, analysing activation patterns, and identifying arrhythmogenic tissue. Cardiac mapping is a broad term that is used here to encompass applications that record electrical or mechanical activity of the heart or both. In recent years, simultaneous and sequential electrical mapping methods have been combined with direct mechanical measurements or imaging techniques to acquire information regarding both the electrical and mechanical activity of the heart (electromechanical mapping) during normal and irregular cardiac behavior. This paper reviews the emerging area of electromechanical mapping from the point of view of the applicable technology, including its history and application.

New Simplified Technique for 3D Mapping and Ablation of Right Ventricular Outflow Tract Tachycardia

OBJECTIVE

To evaluate the safety and efficacy of using a circular multielectrode catheter for mapping and ablation of ventricular tachycardia (VT) or premature ventricular complexes (PVCs) from the right ventricular outflow tract (RVOT).

BACKGROUND

Three-dimensional (3D) mapping systems are commonly used for mapping and ablation of RVOT VT and PVCs. Newer catheters that are circular with multiple electrodes, such as the Lasso catheter, are capable of simultaneously recording from multiple points within a circumferential plane. Given the tubular structure of the RVOT, these catheters could be used for mapping tachycardias from the RVOT.

METHODS

A retrospective cohort study of patients undergoing radiofrequency (RF) ablation of RVOT VT or PVCs was performed. In group 1 (n = 7), mapping was performed with a single ablation catheter and fluoroscopy. In group 2 (n = 10), 3D mapping using ESI (n = 9) or CARTO (n = 1) was performed. In group 3 (n = 12), mapping was performed with a circular multielectrode catheter (n = 12). All ablations were performed with 4-mm tip catheters using RF energy.

RESULTS

Catheter ablation for RVOT VT (n = 15) or PVCs (n = 14) was performed on 29 cases in 26 patients, 9 males. Mean age was 35.9 years. In groups 1, 2, and 3, the mean number of lesions was 17.7 +/- 7.7, 13.6 +/- 7.7, and 18.2 +/- 22.7 and the median number of lesions was 20, 13, and 5, respectively. There were no significant differences in the number of lesions, RF time, fluoroscopy time, procedure time, and acute success rate among the three techniques. There were three complications in group 2 and one in group 3.

CONCLUSION

The use of a circular multielectrode catheter is as effective as the other standard available 3D mapping techniques, both in terms of procedural success and procedural characteristics. Additionally, because of the lower cost associated with using the circular multielectrode catheter approach, further evaluation should be performed to determine whether this is the most cost-effective approach to 3D mapping and ablation of RVOT tachycardias.

Use of novel nonfluoroscopic three-dimensional electroanatomic mapping system to monitor and analyze heart surgery in animal models

BACKGROUND

The new method of three-dimensional (3D) electroanatomic mapping was presented as an important tool for cardiac imaging and intervention. We present herein the first use of this technology for the monitoring, analysis, and development of cardiac surgery at the preclinical stage.

METHODS

The method is based on utilizing a locatable catheter connected to an endocardial mapping and navigating system, to accurately establish the location and orientation of the tip of the mapping catheter and simultaneously record its local electrogram. The 3D geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on six goats that underwent dynamic cardiomyoplasty. Two maps of each animal were performed: preoperative and postoperative during the stimulation protocol of the skeletal muscle.

RESULTS

The electroanatomic mapping system provided detailed maps of the left ventricle during the stimulation protocol, which demonstrated a striking geometric difference between the assisted and the unassisted beats. These geometric changes are best described by referring to left ventricular long-axis movements (22.3 +/- 3.8 degrees vs 3.4 +/- 1.6 degrees, p < 0.001), center-of-mass movements (10.4 +/- 3.0 mm vs 3.9 +/- 1.6 mm, p < 0.005), and the changes in upward movement viewed along the base (7.9 +/- 1.9 mm vs 3.6 +/- 1.7 mm, p < 0.01), middle (13.8 +/- 4.0 mm vs 7.3 +/- 1.8 mm, p < 0.005), and the apex of the heart (28.1 +/- 4.5 vs 5.3 +/- 2.3 mm, p < 0.001) [mean +/- SD].

CONCLUSIONS

The 3D electroanatomic mapping system allows detailed reconstruction of the left ventricular geometry and a clear view of the difference between the assisted and the unassisted beats. This novel monitoring system may serve as an important tool for the analysis and development of new techniques in cardiac surgery.

The reconstruction, from a set of points, and analysis of the interior surface of the heart chamber

Adequate description of heart muscle electrical activity is essential for the proper treatment of cardiac arrhythmias. Contemporary mapping and ablating systems allow a physician to introduce an electrode (catheter) into the human heart, to measure the position of the electrode in space and, simultaneously, the electrical activity timing and the bipolar and unipolar signal amplitudes--which correspond to the electrical viability of the heart muscle. If enough data points are collected, an approximate reconstruction of the heart chamber geometry (anatomy) is possible using also surface data such as the viability and local activity isochrones. Myocardial viability in patients after myocardial infarction is crucial for understanding and treating life threatening arrhythmias. Although there are commercial tools for heart chamber reconstruction, they lack the ability to quantitatively analyse the reconstructed data. Here, we show a method of reconstruction of the left ventricle of the heart from a measured set of data points and perform an interpolation of the measured voltages over the reconstructed surface. Next, we detect regions with voltage in a specified range and compute their areas and circumferences. Our methods allowed us to quantitatively describe the 'normal' muscle, the damaged or scar areas and the border zones between healthy muscle and the scars. In particular, we are able to find geometries of the damaged muscle areas that may be dangerous, e.g. when two such areas lie close to each other creating an isthmus--a macroreentry arrhythmia substrate. This work was inspired by a clinical hypothesis that the size of the border zone corresponds to the rate of occurrence of ventricular arrhythmia in patients after myocardial infarction.

Statistical accuracy of a moving equivalent dipole method to identify sites of origin of cardiac electrical activation

While radio frequency (RF) catheter ablation (RCA) procedures for treating ventricular arrhythmias have evolved significantly over the past several years, the use of RCA has been limited to treating slow ventricular tachycardias (VTs). In this paper, we present preliminary results from computer and animal studies to evaluate the accuracy of an algorithm that uses the single equivalent moving dipole (SEMD) model in an infinite homogeneous volume conductor to guide the RF catheter to the site of origin of the arrhythmia. Our method involves measuring body surface electrocardiographic (ECG) signals generated by arrhythmic activity and by bipolar current pulses emanating from a catheter tip, and representing each of them by a SEMD model source at each instant of the cardiac cycle, thus enabling rapid repositioning of the catheter tip requiring only a few cycles of the arrhythmia. We found that the SEMD model accurately reproduced body surface ECG signals with a correlation coefficients > 0.95. We used a variety of methods to estimate the uncertainty of the SEMD parameters due to measurement noise and found that at the time when the arrhythmia is mostly localized during the cardiac cycle, the estimates of the uncertainty of the spatial SEMD parameters (from ECG signals) are between 1 and 3 mm. We used pacing data from spatially separated epicardial sites in a swine model as surrogates for focal ventricular arrhythmic sources and found that the spatial SEMD estimates of the two pacing sites agreed with both their physical separation and orientation with respect to each other. In conclusion, our algorithm to estimate the SEMD parameters from body surface ECG can potentially be a useful method for rapidly positioning the catheter tip to the arrhythmic focus during an RCA procedure.

Electroanatomic mapping of endocardial right ventricular activation as a guide for catheter ablation in patients with arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular dysplasia is a structural heart disease characterized by fibrofatty degeneration of right ventricular myocardium and arrhythmias of right ventricular origin. The aim of this study was to characterize endocardial right ventricular activation by electroanatomic mapping as a guide for catheter ablation in patients with arrhythmogenic right ventricular dysplasia. Electroanatomic mapping and entrainment procedures were performed in 5 patients with arrhythmogenic right ventricular dysplasia. Endocardial mapping during ventricular tachycardia demonstrated a focal activation pattern with radial spreading of activation from a site of earliest ventricular activation in all directions. Right ventricular activation time (127 +/- 34 ms) was markedly shorter than tachycardia cycle length (415 +/- 92 ms). The site of earliest ventricular activation was found in an aneurysmal outflow tract (n = 2), at the border of aneurysms near the tricuspid annulus (n = 2), and at the apex of the right ventricle (n = 1). Entrainment mapping criteria of these areas of earliest endocardial activity were consistent with exit sites of a reentrant circuit in an area of abnormal myocardium. Fractionated potentials were found 61 +/- 29 ms before the onset of the QRS complex at these sites. Catheter ablation rendered the "clinical" ventricular tachycardia noninducible in four patients but "nonclinical" faster ventricular tachycardias were inducible in three patients. During the follow-up of 7 +/- 3 months after ablation, the frequency of therapies in 4 patients with an implantable cardioverter defibrillator decreased from 49 +/- 61 episodes per month before ablation, to 0.3 +/- 0.5 episodes per month after ablation (P < 0.05). Electroanatomic mapping during ventricular tachycardia facilitates localization of exit sites in relation to aneurysms in diseased right ventricle and may guide catheter ablation in patients with arrhythmogenic right ventricular dysplasia.

Role of contact and noncontact mapping in the curative ablation of tachyarrhythmias

Assessment of the timing of electrical activation recorded by multiple electrodes positioned in various locations within the heart has been the conventional method for mapping cardiac arrhythmias. This technique requires fluoroscopy for catheter manipulation, which in addition to being harmful (ionizing radiation), is inadequate for visualizing the complex three-dimensional cardiac anatomy and lacks reproducibility regarding localization of sites of interest. Because of these limitations, several new mapping systems that can function in a complimentary role to the conventional mapping technique, or can be used independently, have been developed. These new mapping strategies have unique advantages. They overcome the limitations of fluoroscopy by creating accurate three-dimensional intracardiac maps. The ability to localize and accurately display intracardiac catheter positioning and ablation lesion sites facilitate increasingly complex catheter ablation procedures.

Three-dimensional electromechanical mapping: imaging in the operating room of the future

BACKGROUND

Three-dimensional electromechanical mapping has previously been shown to be a clinically important tool for cardiac imaging and intervention. We hypothesized that this technology may be beneficial as an intraoperative modality for assessing cardiac hemodynamics and viability during cardiac surgery. We report here the use of this technology as an imaging modality for intraoperative cardiac surgery.

METHODS

The tip of a locatable catheter connected to an endocardial mapping and navigating system is accurately localized while simultaneously recording local electrical and mechanical functions. Thus the three-dimensional geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on 6 goats that underwent acute dynamic cardiomyoplasty and on 5 dogs that underwent left anterior descending (LAD) coronary artery ligation.

RESULTS

The electromechanical mapping system provided an accurate three-dimensional reconstruction of the beating left ventricle during cardiomyoplasty. After the wrapping procedure, significant end-diastolic area reduction was noted in the base and mid parts of the heart (948 +/- 194 mm2 vs 1245 +/- 33 mm2, p = 0.021; and 779 +/- 200 mm2 vs 1011 +/- 80 mm2, p = 0.016). The area of the cross-section of the apex did not change during the operation. Acute infarcted tissue was characterized 3 days after LAD ligation by concomitant deterioration in both electrical and mechanical function.

CONCLUSIONS

By providing both a clear view of the anatomical changes that occur during cardiac surgery, and an accurate assessment of tissue viability, electroanatomic mapping may serve as an important adjunct tool for imaging and analysis of the heart during cardiac surgery

Advances in cardiac electrophysiology and pacing

Significant advances have been made in the management of cardiac arrhythmias. New technology has enhanced the ability to understand and treat a variety of tachycardias. Excitement and caution surround ablative approaches for atrial fibrillation. The role of ICDs and class III antiarrhythmic drugs in the management of patients at risk for sudden cardiac death has been clarified. A new indication for cardiac pacing is evolving as a supplemental treatment for patients with refractory congestive heart failure. These and other advances provide numerous exciting options for management of cardiac patients.

Electroanatomic magnetic mapping during ablation of isthmus-dependent atrial flutter

INTRODUCTION

Although recent studies have demonstrated that the endpoint of isthmus conduction block is superior to that of termination and subsequent inability to induce atrial flutter (AFl), the optimal method for determining isthmus conduction block has not been determined. Electroanatomic magnetic mapping during coronary sinus (CS) pacing may provide a reliable endpoint for AFl ablation.

METHODS AND RESULTS

Catheter mapping and ablation was performed in 42 patients with isthmus-dependent AFl. The patients were divided into two groups, based on procedural endpoint: Group I (28 patients) - isthmus conduction block was determined based on multipolar catheter recordings and electroanatomic mapping, and Group II (14 patients) - isthmus conduction block was determined by electroanatomic mapping during CS pacing alone. In Group I, ablation procedures were acutely successful in 25 of 28 patients (89 %). A 100 % concordance between the data presented by multipolar catheter recordings and electroanatomic mapping was noted in determining the presence or absence of isthmus conduction block. In Group II, ablation procedures were acutely successful in 13 of 14 patients, 13 (93 %). After a mean of 16.3+/-3.7 months follow up, there was 1 atrial flutter recurrence in the 38 patients (2.6 %) with demonstrated isthmus block at the end of the procedure.

CONCLUSIONS

Electroanatomic magnetic mapping during CS pacing is comparable to the multipolar catheter mapping technique for assessing isthmus conduction block as an endpoint for AFl ablation procedures.

Electromechanical mapping of the heart

Electromechanical endocardial mapping of the heart using a nonfluoroscopic catheter-based system is a new imaging modality that has been studied recently in the experimental setting as well as in patients. Besides its original application in the diagnosis and treatment of various cardiac arrhythmias, it has also been used as an investigational tool for assessing left ventricular function and viability. Finally, the mapping system may be a valuable platform for direct myocardial revascularization using either laser treatment or injection of pharmacologic agents.

Use of multisite electroanatomic mapping to facilitate ablation of intra-atrial reentry following the Mustard procedure

Ablation of intra-atrial reentrant tachycardia following Mustard or Senning procedures has low success rates. The Biosense Carto system was used to map intra-atrial reentry in a 22-year-old woman who had undergone a Mustard procedure. A line of block was created connecting a Mustard baffle suture line to the tricuspid valve annulus, which terminated the arrhythmia and prevented its reinitiation. Multisite electroanatomic mapping was invaluable in defining atrial anatomy and the intra-atrial reentrant pathway, and in creating a contiguous line of block. This mapping may improve ablation success rates in patients following the Mustard or Senning repair.

Catheter ablation of mitral isthmus ventricular tachycardia using electroanatomically guided linear lesions

Mitral isthmus ventricular tachycardia uses a reentrant circuit with a critical isthmus of conduction bounded by the mitral valve proximally and a remote inferior infarction scar distally. Successful catheter ablation requires placement of a lesion to transect the isthmus so as to prevent wavefront propagation. We report a case with previously unsuccessful ablation in which focal isthmus ablation failed to eliminate arrhythmia. Electroanatomic mapping demonstrated a wide tachycardia isthmus, and a linear lesion placed from the edge of the inferior infarct (as demonstrated on the three-dimensional voltage electroanatomic map) to the base of the mitral valve successfully eliminated tachycardia. In some patients with mitral isthmus VT, a wide isthmus requires linear lesion placement to fully transect the isthmus and eliminate tachycardia. Electroanatomic mapping can be used to define isthmus boundaries and thus guide successful ablation.

Nonfluoroscopic three-dimensional mapping for arrhythmia ablation: tool or toy?

INTRODUCTION

Conventional mapping and ablation rely on fluoroscopy, which can result in imprecise positioning of the ablation catheter and long fluoroscopic exposure times. We evaluated a nonfluoroscopic three-dimensional mapping system, termed CARTO, and compared the results of ablation using this technique with those of conventional mapping.

METHODS AND RESULTS

We compared the results of 88 arrhythmia ablations (79 patients) using CARTO with 100 ablations (94 patients) using the conventional technique. The ablations were separated into four groups: (1) AV nodal reentrant tachycardia (AVNRT); (2) atrial tachycardia/flutter; (3) ventricular tachycardia (VT); and (4) bypass tract tachycardia. We compared the success rate, complications, and fluoroscopy and procedure times. The ablation outcomes were excellent and comparable in all four types of the arrhythmias between the two techniques. Major complications included one cardiac tamponade in each group and one second-degree AV block in the conventional group. Fluoroscopy time was shorter using the CARTO technique: 10+/-7 versus 27+/-15 minutes for AVNRT (P < 0.01), 18+/-17 versus 44+/-23 minutes for atrial tachycardia and flutter (P < 0.01), 15+/-12 versus 34+/-31 minutes for VT (P < 0.05), and 21+/-14 versus 53+/-32 minutes for bypass tract tachycardia (P < 0.01). Procedure times were similar except for the bypass tract patients, which was shorter in the CARTO group, 4+/-1.3 versus 5.5+/-2.5 hours (P < 0.01).

CONCLUSION

The electroanatomic three-dimensional mapping technique reduced fluoroscopy time and resulted in excellent outcome without increasing the procedure time.

Epicardial mapping and radiofrequency catheter ablation of ischemic ventricular tachycardia using a three-dimensional nonfluoroscopic mapping system

Endocardial radiofrequency catheter ablation of ischemic left ventricular tachycardia has been of variable success due to multiple factors. Two such factors include the location of the reentrant circuit in the deep myocardium or on the epicardial surface and the inherent limitations of fluoroscopy as a guide for target localization. We report a patient in whom successful epicardial mapping and radiofrequency catheter ablation of an ischemic left ventricular tachycardia was performed using pericardial access and the CARTO electroanatomic mapping system.

Dofetilide in patients with congestive heart failure and left ventricular dysfunction. Danish Investigations of Arrhythmia and Mortality on Dofetilide Study Group

BACKGROUND

Atrial fibrillation occurs frequently in patients with congestive heart failure and commonly results in clinical deterioration and hospitalization. Sinus rhythm may be maintained with antiarrhythmic drugs, but some of these drugs increase the risk of death.

METHODS

We studied 1518 patients with symptomatic congestive heart failure and severe left ventricular dysfunction at 34 Danish hospitals. We randomly assigned 762 patients to receive dofetilide, a novel class III antiarrhythmic agent, and 756 to receive placebo in a double-blind study. Treatment was initiated in the hospital and included three days of cardiac monitoring and dose adjustment. The primary end point was death from any cause.

RESULTS

During a median follow-up of 18 months, 311 patients in the dofetilide group (41 percent) and 317 patients in the placebo group (42 percent) died (hazard ratio, 0.95; 95 percent confidence interval, 0.81 to 1.11). Treatment with dofetilide significantly reduced the risk of hospitalization for worsening congestive heart failure (risk ratio, 0.75; 95 percent confidence interval, 0.63 to 0.89). Dofetilide was effective in converting atrial fibrillation to sinus rhythm. After one month, 22 of 190 patients with atrial fibrillation at base line (12 percent) had sinus rhythm restored with dofetilide, as compared with only 3 of 201 patients (1 percent) given placebo. Once sinus rhythm was restored, dofetilide was significantly more effective than placebo in maintaining sinus rhythm (hazard ratio for the recurrence of atrial fibrillation, 0.35; 95 percent confidence interval, 0.22 to 0.57; P<0.001). There were 25 cases of torsade de pointes in the dofetilide group (3.3 percent) as compared with none in the placebo group.

CONCLUSIONS

In patients with congestive heart failure and reduced left ventricular function, dofetilide was effective in converting atrial fibrillation, preventing its recurrence, and reducing the risk of hospitalization for worsening heart failure. Dofetilide had no effect on mortality.

New advances in class III antiarrhythmic drug therapy

During the past 10 years there has been a major shift in antiarrhythmic drug development from class I to class III antiarrhythmic agents. The first two class III antiarrhythmic drugs that became available, sotalol and amiodarone, also have potent antiadrenergic actions. Newer antiarrhythmic drugs either block a specific ionic current (e.g., dofetilide-induced blockade of the rapidly activating component of the delayed rectifier potassium current) or block multiple ionic channels (e.g., ibutilide and azimilide) in order to prolong atrial and ventricular action potentials without other specific pharmacologic effects. Recent data suggest that these new class III antiarrhythmic drugs are highly effective for treating patients with rhythm disorders with an acceptable degree of proarrhythmia. This manuscript reviews the newer class III agents' effectiveness in treating atrial and ventricular arrhythmias and the recent studies examining drug-induced prolongation of atrial repolarization to prevent or terminate postoperative atrial fibrillation.