High-density mapping of Koch's triangle during sinus rhythm and typical atrioventricular nodal re-entrant tachycardia, integrated with direct recording of atrio-ventricular node structure potential.

BACKGROUND: The mechanism of typical slow-fast atrioventricular nodal re-entrant tachycardia (AVNRT) and its anatomical and electrophysiological circuit inside the right atrium (RA) and Koch's Triangle (KT) are not well known. OBJECTIVE: To identify the potentials of the compact AV node and inferior extensions and to perform accurate mapping of the RA and KT in sinus rhythm (SR) and during AVNRT, to define the tachycardia circuit. METHODS: Consecutive patients with typical AVNRT were enrolled in 12 Italian centers and underwent mapping and ablation by means of a basket catheter with small electrode spacing for ultrahigh-density mapping and a modified signal-filtering toolset to record the potentials of the AV nodal structures. RESULTS: Forty-five consecutive cases of successful ablation of typical slow-fast AVNRT were included. The mean SR cycle length (CL) was 784.1 ± 6 ms and the mean tachycardia CL was 361.2 ± 54 ms. The AV node potential had a significantly shorter duration and higher amplitude in sinus rhythm than during tachycardia (60 ± 40 ms vs. 160 ± 40 ms, p < .001 and 0.3 ± 0.2 mV vs. 0.09 ± 0.12 mV, p < .001, respectively). The nodal potential duration extension was 169.4 ± 31 ms, resulting in a time-window coverage of 47.6 ± 9%. The recording of AV nodal structure potentials enabled us to obtain 100% coverage of the tachycardia CL during slow-fast AVNRT. CONCLUSION: Detailed recording of the potentials of nodal structures is possible by means of multipolar catheters for ultrahigh-density mapping, allowing 100% of the AVNRT CL to be covered. These results also have clinical implications for the ablation of right-septal and para-septal arrhythmias.

C-reactive protein and left atrial appendage velocity are independent determinants of the risk of thrombogenesis in patients with atrial fibrillation.

BACKGROUND: The association between inflammatory status and thrombosis in patients with atrial fibrillation (AF) is unclear. We studied the correlation between inflammation and the risk of thrombogenesis in patients with AF and the relationship of inflammation with other factors associated with thrombotic risk. METHODS: We studied 150 consecutive patients (69 men, age 65+/-12 years) with persistent non-valvular AF who had transesophageal echocardiography prior to cardioversion. Patients underwent also measurements of high-sensitivity C-reactive protein, fibrinogen, D-dimer, and hematocrit levels. RESULTS: Patients were divided into two groups according to the presence (n=52) or absence (n=98) of dense spontaneous echo contrast (SEC) in left atrium or left atrial appendage. The two groups were similar for age, sex, and major clinical risk factors. Patients with dense SEC had significantly larger left atrium diameter (p=0.007), lower left atrial appendage mean velocity (p<0.0001), and higher levels of C-reactive protein (p=0.003), D-dimer (p=0.008), and fibrinogen (p=0.006). At multivariate analysis, only left atrial appendage velocity (odds ratio: 19.11; 95% confidence interval 4.2-80.9) and C-reactive protein (odds ratio: 3.41; 95% confidence interval 1.2-9.8) were significantly associated with thrombus and/or dense SEC. However, there was no relationship between C-reactive protein levels and left atrial appendage velocity (p=0.24, r=-0.09). CONCLUSIONS: Our results show that left atrial appendage velocity and C-reactive protein are independently associated with the risk of thromboembolism in AF. Thus, blood stasis and inflammation appear to constitute two major distinct components of thrombogenesis.

Role of electroanatomic mapping in assessing the extent of atrial standstill: diagnostic and therapeutic implications.

Atrial standstill is characterized by failure of atrial excitation, either spontaneous or induced by atrial electric stimulation. We report the case of a 38-year-old man with severe bradycardia and junctional escape rhythm associated with dilative cardiomyopathy. Electroanatomic mapping showed the absence of atrial viability in almost the entire right atrial endocardial surface and excluded the feasibility of atrial pacing.

Pacing failure due to microdislodgement of ventricular pacing lead detected by home monitoring technology.

A 68-year-old woman affected by sick sinus syndrome was implanted with a dual-chamber pacemaker provided by home monitoring technology. After discharge, an increase in ventricular threshold and a high variability of R wave measurements were detected early by the home monitoring system. Manual tests confirmed the presence of pacing and sensing failure and a normal ventricular impedance. The pacing lead integrity and a stable position of the lead tip in right ventricular apex were assessed by chest X-ray. A diagnosis of microdislodgement was made. After a second procedure for ventricular lead repositioning, no further malfunctions were detected.

Catheter ablation of isolated premature ventricular contractions arising from the sinus of Valsalva.

Monomorphic premature ventricular contractions (PVCs) are a benign phenomenon in patients without structural heart disease. The focal source is usually localised in the right ventricular outflow tract and more rarely in the left ventricular outflow tract. We report two cases of frequent isolated PVCs treated with radiofrequency catheter ablation. Ventricular dysfunction was documented in one patient and the potential contribution of arrhythmia to ventricular dysfunction was suspected. In both patients electroanatomic mapping of the right and left ventricular outflow tracts was performed, which allowed identification of the earliest ventricular activation during PVCs. The site of the earliest ventricular activation was documented in both cases at the left coronary cusp of the aortic valve. Aortography was performed to disclose the relationship between the ablation catheter and the anatomic structure of the aortic root. PVCs were successfully eliminated with radiofrequency application in both patients.

Relation of C-reactive protein to long-term risk of recurrence of atrial fibrillation after electrical cardioversion.

The aim of this study is to assess the role of C-reactive protein (CRP) in predicting long-term risk of atrial fibrillation (AF) recurrence after electrical cardioversion. CRP levels are associated with the presence of AF and failure of electrical or pharmacologic cardioversion, but no previous study has assessed their predictive role in long-term follow-up after successful electrical cardioversion. One hundred two consecutive patients (age 67 +/- 11 years; 58 men) with nonvalvular persistent AF who underwent successful biphasic electrical cardioversion were studied. High-sensitivity CRP was measured immediately before cardioversion. Follow-up was performed up to 1 year in all cases. Patients were divided into 4 groups according to CRP quartiles. Patients in the lowest CRP quartile (<1.9 mg/L) had significantly lower rates of AF recurrence (4% vs 33% at 3 months in the other 3 groups combined, p = 0.007, and 28% vs 60% at 1 year, p = 0.01). The 4 groups were similar in age, gender, ejection fraction, and left atrial size. Survival analysis confirmed that patients in the lowest CRP quartile had a lower recurrence rate (p = 0.02). Cox regression analyses using age, gender, hypertension, diabetes, ejection fraction, left atrial diameter, use of antiarrhythmic drugs, angiotensin-converting enzyme inhibitors or angiotensin II antagonists, and statins, and CRP quartiles as covariates showed that only CRP was independently associated with AF recurrence during follow-up (hazard ratio 4.98, 95% confidence interval 1.75 to 14.26, p = 0.003). In conclusion, low CRP is associated with long-term maintenance of sinus rhythm after cardioversion for nonvalvular AF.

Left atrial ablation versus biatrial ablation for persistent and permanent atrial fibrillation: a prospective and randomized study.

OBJECTIVES: The aim of this study was to compare--in patients with persistent and permanent atrial fibrillation (AF)--the efficacy and safety of left atrial ablation with that of a biatrial approach. BACKGROUND: Left atrium-based catheter ablation of AF, although very effective in the paroxysmal form of the arrhythmia, has an insufficient efficacy in patients with persistent and permanent AF. METHODS: Eighty highly symptomatic patients (age, 58.6 +/- 8.9 years) with persistent (n = 43) and permanent AF (n = 37), refractory to antiarrhythmic drugs, were randomized to two different ablation approaches guided by electroanatomical mapping. A procedure including circumferential pulmonary vein, mitral isthmus, and cavotricuspid isthmus ablation was performed in 41 cases (left atrial ablation group). In the remaining 39 patients (biatrial ablation group), the aforementioned approach was integrated by the following lesions in the right atrium: intercaval posterior line, intercaval septal line, and electrical disconnection of the superior vena cava. RESULTS: During follow-up (mean duration 14 +/- 5 months), AF recurred in 39% of patients in the left atrial ablation group and in 15% of patients in the biatrial ablation group (p = 0.022). Multivariable Cox regression analysis showed that ablation technique was an independent predictor of AF recurrence during follow-up. CONCLUSIONS: In patients with persistent and permanent AF, circumferential pulmonary vein ablation, combined with linear lesions in the right atrium, is feasible, safe, and has a significantly higher success rate than left atrial and cavotricuspid ablation alone.

Recovery of cardiac function after ablation of atrial tachycardia arising from the tricuspid annulus.

Tachycardia-induced cardiomyopathy is a reversible form of heart failure. An early diagnosis and an effective cure of the underlying tachycardia are crucial for a favorable outcome. Different kinds of atrial and ventricular arrhythmias may induce tachycardiomyopathy. Focal atrial tachycardia may be easily suppressed by means of transcatheter ablation. Relationships between focal atrial tachycardia and tachycardiomyopathy have not been deeply analyzed. In the present paper we report a case of a 76-year-old man with tachycardia-induced cardiomyopathy caused by recurrences of focal atrial tachycardia arising from the tricuspid annulus. The arrhythmia was successfully treated with transcatheter ablation. In the follow-up no recurrences of the arrhythmia occurred and a significant improvement in myocardial function was observed.

Atrial flutter and atrial fibrillation: which relationship? New insights into the electrophysiological mechanisms and catheter ablation treatment.

Atrial fibrillation (AF) and atrial flutter (AFL) are two arrhythmias commonly associated in clinical practice. This association generally reflects a similar arrhythmogenic substrate. It has been observed that the development of isthmus-dependent AFL is often preceded by AF. The conversion from AF to AFL develops thanks to a line of functional block in the right atrial free wall. In this subset a particular condition is represented by typical AFL that occurs during the treatment with class IC or III antiarrhythmic drugs in patients with previous AF. A hybrid approach (antiarrhythmic drugs and catheter ablation) has been proposed as a possible treatment of drug-induced AFL. The conversion from AFL to AF is less frequent and may be due to several mechanisms: a shortening of the length of the line of functional block, atrial ectopic beats or rapid atrial rhythm, focal activation from the pulmonary veins, alternans of atrial action potentials. Also, atypical right and left AFL can determine AF. Finally, atypical AFL may occur after AF ablation, and could be prevented by associated cavotricuspid isthmus ablation.

N-3 Fatty acids for the prevention of atrial fibrillation after coronary artery bypass surgery: a randomized, controlled trial.

OBJECTIVES: The aim of this study was to assess the efficacy of preoperative and postoperative treatment with n-3 polyunsaturated fatty acids (PUFAs) in preventing the occurrence of atrial fibrillation (AF) after coronary artery bypass graft surgery (CABG). BACKGROUND: Postoperative AF is a common complication of CABG. There is growing clinical evidence that PUFAs have cardiac antiarrhythmic effects. METHODS: A total of 160 patients were prospectively randomized to a control group (81 patients, 13 female, 64.9 +/- 9.1 years) or PUFAs 2 g/day (79 patients, 11 female, 66.2 +/- 8.0 years) for at least 5 days before elective CABG and until the day of discharge from the hospital. The primary end point was the development of AF in the postoperative period. The secondary end point was the hospital length of stay after surgery. All end points were independently adjudicated by two cardiologists blinded to treatment assignment. RESULTS: The clinical and surgical characteristics of the patients in the two groups were similar. Postoperative AF developed in 27 patients of the control group (33.3%) and in 12 patients of the PUFA group (15.2%) (p = 0.013). There was no significant difference in the incidence of nonfatal postoperative complications, and postoperative mortality was similar in the PUFA-treated patients (1.3%) versus controls (2.5%). After CABG, the PUFA patients were hospitalized for significantly fewer days than controls (7.3 +/- 2.1 days vs. 8.2 +/- 2.6 days, p = 0.017). CONCLUSIONS: This study first demonstrates that PUFA administration during hospitalization in patients undergoing CABG substantially reduced the incidence of postoperative AF (54.4%) and was associated with a shorter hospital stay.

Long-term follow-up of right atrial ablation in patients with atrial fibrillation:.

INTRODUCTION: The aim of this study was to evaluate the efficacy and the impact on quality of life of a new ablative approach to the right atrium in patients with atrial fibrillation (AF). METHODS AND RESULTS: Seventy-four symptomatic patients with paroxysmal (n = 49) or permanent (n = 25) refractory AF underwent radiofrequency ablation. A nonfluoroscopic electroanatomic mapping system was used to perform the following lesions: (1) an isthmus line between the tricuspid annulus and the inferior vena cava; (2) a posterior intercaval line from the superior vena cava and the inferior vena cava; (3) a septal line from the superior vena cava to the fossa ovalis, proceeding to the coronary sinus ostium where a circumferential line around the ostium was performed, and then on to the inferior vena cava; and (4) a transversal lesion connecting the posterior intercaval and the septal lesions. In addition, electrical disconnection of the superior vena cava was performed. There were no complications. Postablation remapping showed the absence of discrete electrical activity inside and just around the ablation lines. Electrical disconnection of the superior vena cava was obtained in all patients. After 21 +/- 6 months, 49 patients (66%) had stable sinus rhythm with continuation of the previous antiarrhythmic drug therapy, 13 patients (18%) were considered improved, and 12 (16%) received no benefit (unsuccessful procedure). After ablation, quality of life was significantly improved, reaching the levels of the general Italian population. Ejection fraction and the extent of the low-voltage area were found by multivariate analysis to be independent predictors of AF recurrence. CONCLUSION: The results of the present study suggest that this ablative approach in combination with antiarrhythmic drugs is safe and effective in treating AF, leading to a marked increase in quality of life in patients with refractory AF.

Risk stratification for arrhythmic events in patients with idiopathic dilated cardiomyopathy: a review of the literature and current perspectives.

The prognosis for patients with idiopathic dilated cardiomyopathy (DCM) has markedly improved during the last decade, mainly because of advancements in therapeutic strategies. However, sudden death still accounts for a significant part of the total mortality in patients with moderate disease. Recent primary prophylactic trials failed to demonstrate any benefit of cardioverter-defibrillator implantation in an unselected group of idiopathic DCM patients and thus the identification of the subgroup of patients at high arrhythmic risk is crucial. Although different risk stratification methods have been evaluated in risk assessment, the reported clinical value differs in studies, mainly because of differences in either methodology and/or patient selection. The present review focuses on arrhythmic events in idiopathic DCM and on the value of noninvasive methods and electrophysiological study in the risk stratification of this group of patients.

Electropharmacological effects of antiarrhythmic drugs on atrial fibrillation termination. Part I: Molecular and ionic fundamentals of antiarrhythmic drug actions.

In the last few years many studies have been performed with the aim of gaining a better understanding of the pathophysiological nature of atrial fibrillation. These recent observations provide new insights into the initiation and perpetuation of atrial fibrillation, underlying the importance of the pulmonary veins as major sources of atrial triggers and introducing new concepts such as the atrial electrical remodeling and the spatial heterogeneity of the electrophysiological characteristics of this arrhythmia. The increasing knowledge about the cardiac ion channel structure and function and about the electrophysiological actions of the antiarrhythmic drugs may contribute to a better comprehension of the mechanisms of the pharmacological termination of the arrhythmia. In part I of the review we try to give a unified vision of the old models and new concepts about the molecular and ionic fundamentals of antiarrhythmic drug actions.

Electropharmacological effects of antiarrhythmic drugs on atrial fibrillation termination. Part II: New insights into the electrophysiological mechanisms of atrial fibrillation termination.

Antiarrhythmic drugs have been largely used to convert atrial fibrillation to sinus rhythm. Classes Ia, Ic and III antiarrhythmic agents are all known to be effective. Nevertheless, the electrophysiological properties of such agents even of the same class are very different. The mechanisms of the pharmacological termination of atrial fibrillation is an interesting issue that has not been so extensively studied yet. In this review we try to summarize the principal concepts about the electrophysiological substrate of atrial fibrillation and to give a unified and modern overview of the issue of the mechanisms of the pharmacological termination of the arrhythmia.

Atrial flutter: arrhythmia circuit and basis for radiofrequency catheter ablation.

The term atrial flutter was introduced 90 years ago for an arrhythmia with a unique electrocardiographic pattern. The development of endocardial mapping techniques in the last decade allowed the detailed characterization of the tachycardia circuit and the identification of the cavotricuspid isthmus as its critical part. This review stresses the position of atrial flutter in the new classification of atrial tachycardias and focuses on its unique electrophysiological characteristics and different variants described in humans. Transcatheter radiofrequency ablation across the cavotricuspid isthmus constitutes a feasible and safe therapy, which prevents flutter recurrences during the long-term follow-up. This paper describes the different techniques that validate bidirectional isthmus block, which is an important endpoint for successful ablation.

Transesophageal low-energy cardioversion of atrial fibrillation without fluoroscopy outside the electrophysiology laboratory.

BACKGROUND: Low-energy internal cardioversion (LEIC) is a safe and effective procedure for the restoration of sinus rhythm in patients with atrial fibrillation refractory to external cardioversion. However, the procedure needs fluoroscopy and the use of the electrophysiology laboratory, even when the esophageal approach is utilized. The aim of this study was to assess the efficacy, safety and tolerability of a new simplified procedure of esophageal LEIC performed without fluoroscopy, outside the electrophysiology laboratory. METHODS: Thirty consecutive patients (23 males, 7 females) with persistent atrial fibrillation were submitted to LEIC using a step-up protocol (by steps of 50 V, starting from 200 V). Twenty (66%) were resistant to external cardioversion. A large surface area lead (cathode) was positioned within the esophagus, 45 cm from the nasal orifice. A second large surface area lead (anode) was positioned in the right atrium via the right internal jugular vein without fluoroscopic control. Synchronization of delivery of the shock with the QRS was achieved by means of two cutaneous electrodes positioned on the thoracic wall. RESULTS: Sinus rhythm was restored in 28 patients (93%) with a mean delivered energy of 15.2 +/- 7.5 J (range 5-27 J) and a mean impedance of 48.3 +/- 5.6 Ohm. No complication occurred during and after the procedure that was well tolerated under sedation. CONCLUSIONS: This new technique of performing esophageal LEIC is effective and seems to be safe and well tolerated. In this way internal cardioversion can be performed without fluoroscopy, outside the electrophysiology laboratory.

Atrioventricular nodal reentrant tachycardia: anatomical and electrophysiological considerations.

Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common regular narrow QRS tachycardias. Although the principal understanding of the physiology of dual atrioventricular conduction as a substrate for the reentry mechanism in AVNRT has not changed during the last 25 years, there is still some uncertainty with regard to the exact circuit delineation. At least four forms of AVNRT have been described and several possible circuits have been proposed. Although the refinement of our knowledge about AVNRT seems to be purely academic since further insight will probably not increase the success rate of treatment by radiofrequency catheter ablation, AVNRT continues to puzzle both clinical and basic electrophysiologists. The authors summarize our present knowledge about AVNRT and stress the unique features of the atrioventricular junction anatomy and the current opinions on the reentrant impulse propagation.

Relations between monophasic action potential duration and refractoriness after cardioversion of persistent atrial fibrillation: results in wash-out and amiodarone-treated patients.

BACKGROUND: The relation between repolarization and refractoriness has been clinically evaluated both in the atrium and ventricle. However, this relation has not been carefully investigated in the atria of patients with persistent atrial fibrillation after cardioversion. METHODS: We determined the refractoriness and monophasic action potential duration at 90% of repolarization (MAP90), at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites after internal cardioversion of persistent atrial fibrillation in 27 patients. RESULTS: The effective refractory periods (ERPs) were longer in amiodarone-treated patients (group 1) than in wash-out patients (group 2) (211.3 +/- 26.4 vs 199.1 +/- 24.3 ms, p < 0.002) as well as the MAP90 (243.6 +/- 36.8 vs 223.1 +/- 29.2 ms, p < 0.001). Linear regression analysis showed a direct relation between the MAP90 and ERP changes induced by different pacing cycle lengths (r = 0.77 and r = 0.92 in the amiodarone and wash-out patients, respectively). The ERP/MAP90 ratio was similar at all pacing cycle lengths in both wash-out and amiodarone groups and was always < 1. The mean ERP and MAP90 were shorter in the lateral right atrial sites than in the atrial roof and septum in both group 1 and group 2 patients (p < 0.001). CONCLUSIONS: A linear correlation was found between ERP and MAP90 in response to changes in pacing cycle lengths. Postrepolarization refractoriness was not observed after cardioversion of persistent atrial fibrillation. Pretreatment with oral amiodarone does not affect these electrophysiological features or the dispersion of ERP and MAP90 in the right atrium after sinus rhythm restoration.

Intracardiac echocardiography: from electroanatomic correlation to clinical application in interventional electrophysiology.

Intracardiac echocardiography (ICE), using an ultrasound transducer at the tip of a percutaneously placed catheter, has recently been introduced for the visualization of the intracardiac anatomy and in order to reduce the fluoroscopy time. This review focuses predominantly on the current use of ICE in interventional electrophysiology. ICE has been shown to facilitate the targeting of specific anatomic landmarks, such as the crista terminalis, the Eustachian ridge, the tricuspid annulus, the coronary sinus ostium, and the pulmonary veins that cannot be adequately visualized at fluoroscopy. Direct imaging of these sites can be advantageous in that it facilitates the accurate guidance of the ablative procedure and shortens the fluoroscopy time. ICE has been demonstrated to be useful in the positioning and stabilization of the imaging ablation catheter, the evaluation of the lesion size and continuity and in the immediate identification of complications. Furthermore, in the last few years there has been a revival in the use of transseptal catheterization due to a larger development of radiofrequency catheter ablation in the left atrium. ICE, providing excellent views of the fossa ovalis and of the transseptal apparatus, can be safely used to prevent life-threatening complications following inadvertent puncture of anatomic structures such as the lateral wall of the left atrium or the aortic root. Moreover, ICE appears to be very useful in combining true anatomical features with electrical activation in an attempt to construct realistic electrical-anatomical maps. Finally, the three-dimensional tomographic reconstruction of intracardiac images and the phased array ICE catheter with Doppler capabilities seem to be promising tools both for the guidance of ablation procedures as well as in leading experimental studies.