Multimodality imaging for patient evaluation and guidance of catheter ablation for atrial fibrillation - current status and future perspective.

Left atrial catheter ablation is an established non-pharmacological therapy for the treatment of atrial fibrillation. The importance of a noninvasive multimodality imaging approach is emphasized by the current guidelines for the various phases of the ablation work-up e.g. patient identification, therapy guidance and procedural evaluation. Advances in the capabilities of imaging modalities and the increasing cost of healthcare warrant a review of the multimodality approach. This review discusses the application of cardiac imaging for pulmonary vein and left atrial ablation divided into stages: pre-procedural stage (assessment of left atrial dimensions, left atrial appendage thrombus and pulmonary vein anatomy), peri-procedural stage (integration of anatomical and electrical information) and post-procedural stage (evaluation of efficacy by assessment of tissue properties). Each section is dedicated to one of the subtopics of a stage, allowing a thorough comparison to be made between the strengths and weaknesses of the different imaging modalities and the identification of one that exhibits the potential for a single technique approach.

Surgical treatment of atrial fibrillation : a systematic review.

BACKGROUND: The recently published overwhelming number of publications on the surgical treatment of AF, using a wide variety of techniques, blurred any precise appreciation of the nowadays surgical treatment of AF. As a consequence, the "state of the art" of the surgical technique of AF is ill-defined. OBJECTIVES: In this review the efficacy of the alternative sources of energy (radiofrequency-microwave and cryoablation; (group I) and the classical "cut and sew" Cox-Maze III (group II), which claims a 97-99% sinus rhythm (SR) success rate, were evaluated in the surgical treatment of atrial fibrillation (AF). METHODS: A computerized search in the PubMed and Medline database was conducted. Only original, English written, clinical manuscripts on the surgical treatment of atrial fibrillation citing the clinical outcome, including the postoperative sinus rhythm, were included. The following data were registered: the absolute numbers and percentages of treated patients, gender (male versus female) distribution, the type of arrhythmia (permanent or paroxysmal AF), type of surgery (mitral or non-mitral valve or a lone AF surgical procedure), postoperative morbidity (bleeding, the use of an intra-aortic balloon pump, cerebral vascular accident), postoperative pacemaker implantations, 30-day mortality, survival and sinus rhythm conversion. The mean values for age (years), left atrial diameter (mm), preoperative duration of AF (years) and left ventricular ejection fraction (%) were also recorded. RESULTS: Forty-eight studies were included comprising 3832 patients: 2279 in group I and 1553 in group II. The mean duration of AF, left atrial diameter and LVEF were 5.4 versus 5.5 years (p=0.90), 55.5 versus 57.8 mm (p=0.23) and 57 versus 58% (p=0.63). The postoperative SR rates for group I and II were 78.3 versus 84.9% (p=0.03). However, the "cut and sew" Cox-Maze III was conducted in younger patients (55.0 versus 61.2 years; p=0.005), more often to treat paroxysmal (22.9 versus 8.0%) and lone AF (19.3 versus 1.6%). Alternative sources of energy were predominantly used to treat permanent AF (92.0%), almost always as a concomitant surgical procedure (98.4%) and increasingly in combination with non-mitral valve surgery (18.5%). After correction for these variations, the postoperative SR conversion rates for group I and II did not differ significantly anymore. CONCLUSIONS: We could not identify any significant difference in the postoperative SR conversion rates between the classical 'cut and sew' and the alternative sources of energy, which were used to treat atrial fibrillation.

Increased dispersion and shortened refractoriness caused by verapamil in chronic atrial fibrillation.

OBJECTIVES: The objective was to assess the effect ofverapamil on atrial fibrillation (AF) cycle length and spatial dispersion of refractoriness in patients with chronic AF. BACKGROUND: Previous studies have suggested that verapamil prevents acute remodeling by AF. The effects of verapamil in chronic AF are unknown. METHODS: During electrophysiologic study in 15 patients with chronic AF (duration >1 year), 12 unipolar electrograms were recorded from right atrial free wall, right atrial appendage and coronary sinus, along with monophasic action potential recordings from the right atrial appendage. The mean fibrillatory interval at each atrial recording site was used as an index for local refractoriness. Dispersion of refractoriness was calculated as the standard deviation of all local mean fibrillatory intervals expressed as a percentage of the overall mean fibrillatory interval. After baseline measurements, verapamil (0.075 mg/kg intravenous in 10 min) was infused and the measurements were repeated. RESULTS: After administration ofverapamil, mean fibrillatory intervals shortened by a mean of 16.6 +/- 3.3 ms (p < 0.001) at the right free wall, 15.0 +/- 3.5 ms (p < 0.001) at the appendage and 17.1 +/- 3.2 ms (p < 0.01) in the coronary sinus. Monophasic action potential duration decreased by 15.9 +/- 4.0 ms (p < 0.01). Dispersion of refractoriness increased in all patients from 3.8 +/- 0.8 to 5.1 +/- 1.8 (p < 0.001). A strong correlation between mean fibrillatory intervals and action potential duration was found, both before and after verapamil. CONCLUSIONS: Verapamil caused shortening of refractoriness and increase in spatial dispersion of refractoriness in patients with chronic AF. This implies that verapamil is not useful in reversing the remodeling process in these patients.

Catheter ablation of incisional atrial tachycardia using a novel mapping system: LocaLisa.

Incisional atrial tachycardia occurs due to reentry around surgical scars. Pharmacological therapy is often ineffective. This study assessed the efficacy of a novel mapping system (LocaLisa) in facilitating catheter ablation of incisional atrial tachycardia circuits. Eight consecutive patients (four men, four women) with incisional atrial tachycardia (median age 23.5 years, range 9-44) following previous repair of congenital heart defects underwent transcatheter mapping and ablation of the arrhythmogenic substrate using a mapping system (LocaLisa) that allows localization of endocardial electrodes in a three-dimensional space. Critical isthmuses for the tachycardia circuits were identified by demonstrating concealed entrainment using standard pacing and mapping techniques. Scars and natural anatomic barriers were marked on the LocaLisa image. Lines of block were created by radiofrequency current application between scars and natural anatomic barriers, or between two scars, to close isthmuses demonstrated to be critical for the reentrant circuit. All lines of block were verified in both directions. All reentrant circuits around incisions were successfully ablated. Seven additional tachycardia mechanisms were identified in four patients (common atrial flutter [n = 4], atrioventricular nodal [AVN] reentry [n = 2], ectopic atrial tachycardia [n = 1]) and were also ablated in a single session. The mean fluoroscopy time was 28.4 +/- 13.8 minutes. All patients are arrhythmia-free at a median follow-up of 20 (6-22) months. The LocaLisa mapping system is effective for identification of scars and ablation targets, for confirming lines of block, and facilitating ablation of complex reentrant circuits.

Ventricular tachycardia as a complication of atrial flutter ablation.

A 61-year-old woman with dilated cardiomyopathy, who previously underwent successful radiofrequency catheter ablation for atrial flutter, developed monomorphic ventricular tachycardia (VT). The site of VT origin was the inferobasal right ventricle adjacent to the previous atrial isthmus ablation area. The most likely mechanism for the VT was scar-related reentry, the scar being the result of previous radiofrequency lesions in the atrial isthmus. The VT was successfully ablated.

Identification of the substrate of atrial vulnerability in patients with idiopathic atrial fibrillation.

BACKGROUND: Experimental studies have shown that atrial fibrillation (AF) causes remodeling, which facilitates AF perpetuation. AF may also, however, occur in patients without remodeling and underlying structural cardiac disease. The substrate for enhanced vulnerability in these patients is unknown. METHODS AND RESULTS: We studied 43 patients without structural heart disease: 18 patients with documented sporadic paroxysmal AF and 25 control patients without AF. In each patient, a decapolar catheter was positioned against the right atrial free wall, and a quadripolar catheter was positioned in the right atrial appendage. Unipolar electrograms were recorded. Atrial vulnerability was assessed according to an increasingly aggressive stimulation protocol. Mean local fibrillatory interval (FI) was used as an index of local refractoriness. Spatial dispersion of refractoriness was assessed through the calculation of the coefficient of dispersion (CD), which was defined as the SD of mean local FI expressed as a percentage of the mean FI. In the AF group, AF was induced with a single extrastimulus in 16 of 18 patients; the CD was 5.4+/-2.6, and the mean FI was 164+/-29 ms. In the control group, AF could be induced only with more aggressive pacing in 23 of the 25 patients; the CD was 1.4+/-0.7 (P<0.0001), and the mean FI was 175+/-26 ms (NS). CONCLUSIONS: Patients with idiopathic AF showed increased dispersion of refractoriness, which may be the substrate for the observed enhanced inducibility and spontaneous occurrence of AF.

Clinical application of an integrated 3-phase mapping technique for localization of the site of origin of idiopathic ventricular tachycardia.

BACKGROUND: Radiofrequency (RF) catheter ablation provides curative treatment for idiopathic ventricular tachycardia (VT). METHODS AND RESULTS: Nineteen consecutive patients with an idiopathic VT underwent RF catheter ablation. An integrated 3-phase mapping approach was used, consisting of the successive application of online 62-lead body surface QRS integral mapping, directed regional paced body surface QRS integral mapping, and local activation sequence mapping. Mapping phase 1 was localization of the segment of VT origin by comparing the VT QRS integral map with a database of mean paced QRS integral maps. Mapping phase 2 was body surface pace mapping during sinus rhythm in the segment localized in phase 1 until the site at which the paced QRS integral map matched the VT QRS integral map was identified (ie, VT exit site). Mapping phase 3 was local activation sequence mapping at the circumscribed area identified in phase 2 to identify the site with the earliest local endocardial activation (ie, site of VT origin). This site became the ablation target. Ten VTs were ablated in the right ventricular outflow tract, 2 at the basal LV septum, and 7 at the midapical posterior left ventricle. A high long-term ablation success (mean follow-up duration, 14+/-9 months) was achieved in 17 of the 19 patients (89%) with a low number of RF pulses (mean, 3.3+/-2.2 pulses per patient). CONCLUSIONS: This prospective study shows that integrated 3-phase mapping for localization of the site of origin of idiopathic VT offers efficient and accurate localization of the target site for RF catheter ablation.

LocaLisa: new technique for real-time 3-dimensional localization of regular intracardiac electrodes.

BACKGROUND: Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate if a systematic lesion pattern is required in the treatment of complex arrhythmogenic substrates. METHODS AND RESULTS: We developed a new technique for online 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy within the right atrium, right ventricle, and left ventricle by comparing measured and true interelectrode distances of a decapolar catheter. Long-term stability was analyzed by localization of the most proximal His bundle before and after slow pathway ablation. Electrogram recordings were unaffected by the applied electrical field. Localization data from 3 catheter positions, widely distributed within the right atrium, right ventricle, or left ventricle, were analyzed in 10 patients per group. The relationship between measured and true electrode positions was highly linear, with an average correlation coefficient of 0.996, 0.997, and 0.999 for the right atrium, right ventricle, and left ventricle, respectively. Localization accuracy was better than 2 mm, with an additional scaling error of 8% to 14%. After 2 hours, localization of the proximal His bundle was reproducible within 1.4+/-1.1 mm. CONCLUSIONS: This new technique enables accurate and reproducible real-time localization of electrode positions in cardiac mapping and ablation procedures. Its application does not distort the quality of electrograms and can be applied to any electrode catheter.

Accuracy of the LocaLisa system in catheter ablation procedures.

Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate in the ablation of complex arrhythmogenic substrates. We developed a new technique for real-time 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy by comparing measured and true interelectrode distances between the tip and the 10th electrode of a decapolar catheter, and the tip and the 4th electrode of a quadripolar catheter during catheter ablation procedures. Long-term stability was analyzed by localization of the proximal His bundle before and after slow pathway ablation. Accuracy achieved with the 54-mm distance between the two outer electrodes of the decapolar catheters was 101% +/- 15%, 95% +/- 10%, and 97% +/- 8% in the right atrium, right ventricle, and left ventricle, respectively. During catheter ablation procedures, the measured distance between the tip and 4th electrode of the mapping catheter was 100% +/- 15% in atrial flutter, 100% +/- 12% in slow pathway ablation, and 100% +/- 14% in ablations for left ventricular tachycardia. After 2 hours, localization of the proximal His bundle was reproducible within 1.4 +/- 1.1 mm. The LocaLisa technique allows for reproducible, real-time nonfluoroscopic 3D visualization of standard mapping and ablation catheters and is sufficiently accurate for the creation of linear radiofrequency lesions. The freedom of catheter choice makes the LocaLisa system an invaluable tool in catheter mapping and ablation procedures.

Cost-effectiveness of implantable defibrillator as first-choice therapy versus electrophysiologically guided, tiered strategy in postinfarct sudden death survivors. A randomized study.

BACKGROUND: Rising costs of health care, partly as a result of costly therapeutic innovations, are of concern to both the medical profession and healthcare authorities. The implantable cardioverter-defibrillator (ICD) is still not remunerated by Dutch healthcare insurers. The aim of this study was to evaluate the cost-effectiveness of early implantation of the ICD in postinfarct sudden death survivors. METHODS AND RESULTS: Sixty consecutive postinfarct survivors of cardiac arrest caused by ventricular tachycardia or fibrillation were randomly assigned either ICD as first choice (n = 29) or a tiered therapy starting with antiarrhythmic drugs and guided by electrophysiological (EP) testing (n = 31). Median follow-up was 729 days (range, 3 to 1675 days). Fifteen patients died, 4 in the early ICD group and 11 in the EP-guided strategy group (P = .07). For quantitative assessment, the cost-effectiveness ratio was calculated for both groups and expressed as median total costs per patient per day alive. Because effectiveness aspects other than mortality are not incorporated in this ratio, other factors related to quality of life were used as qualitative measures of cost-effectiveness. The cost-effectiveness ratios were $63 and $94 for the early ICD and EP-guided strategy groups, respectively, per patient per day alive. This amounts to a net cost-effectiveness of $11,315 per patient per year alive saved by early ICD implantation. Costs in the early ICD group were higher only during the first 3 months of follow-up, but as a result of the high proportion of therapy changes, including arrhythmia surgery and late ICD implantation, costs in the EP-guided strategy group became higher after that. Patients discharged with antiarrhythmic drugs as sole therapy had the lowest total costs. This subset, however, showed extremely high mortality, resulting in a poor cost-effectiveness ratio ($196 per day). Invasive therapies and hospitalization were the major contributors to costs. If quality-of-life measures are taken into account, the cost-effectiveness of early ICD implantation was even more favorable. Recurrent cardiac arrest and cardiac transplantation occurred in the EP-guided strategy group only, whereas exercise tolerance, total hospitalization duration, number of invasive procedures, and antiarrhythmic therapy changes were significantly in favor of early ICD implantation. CONCLUSIONS: In terms of cost-effectiveness, early ICD implantation is superior to the EP-guided therapeutic strategy in postinfarct sudden death survivors.