Spatial characterization of the tachycardia circuit of atrioventricular nodal re-entrant tachycardia.

AIMS: The exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) remains elusive. To assess the location and dimensions of the AVNRT circuit. METHODS AND RESULTS: Both typical and atypical AVNRT were induced at electrophysiology study of 14 patients. We calculated the activation time of the fast and slow pathways, and consequently, the length of the slow pathway, by assuming an average conduction velocity of 0.04 mm/ms in the nodal area. The distance between the compact atrioventricular node and the slow pathway ablating electrode was measured on three-dimensionally reconstructed fluoroscopic images obtained in diastole and systole. We also measured the length of the histologically discrete right inferior nodal extension in 31 human hearts. The length of the slow pathway was calculated to be 10.8 ± 1.3 mm (range 8.2-12.8 mm). The distance from the node to the ablating electrode was measured in five patients 17.0 ± 1.6 mm (range 14.9-19.2 mm) and was consistently longer than the estimated length of the slow pathway (P < 0.001). The length of the right nodal inferior extension in histologic specimens was 8.1 ± 2.3 mm (range 5.3-13.7 mm). There were no statistically significant differences between these values and the calculated slow pathway lengths. CONCLUSION: Successful ablation affects the tachycardia circuit without necessarily abolishing slow conduction, probably by interrupting the circuit at the septal isthmus.

Ventricular ectopy from the non-coronary cusp: Pathophysiological and anatomical considerations.

Non-coronary cusp (NCC) is a rare site for ventricular arrhythmias because it does not come into direct contact with the ventricular myocardium. Instead, the NCC comes in contact with the membranous septum near the His region. We describe a case of a young man with a ventricular ectopy who was successfully ablated in the NCC. In our case the much greater prematurity in the NCC than in the His region suggests that the arrhythmic site of origin is not in the peri-His area but most likely a myocardial extension adjoining the aortic root.

Electrophysiology testing for risk stratification of patients with ischaemic cardiomyopathy: a call for action.

Current guidelines recommendations, based on the results of primary sudden cardiac death prevention trials, use the left ventricular ejection fraction (LVEF) as a sole criterion for the indication of implantable cardioverter defibrillator therapy for primary prevention purposes. In this article, we review the sensitivity and specificity of LVEF for predicting arrhythmic vs. non-arrhythmic cardiac death and examine existing evidence on the use of electrophysiology testing for risk stratification of ischaemic patients with reduced left ventricular function.

Catheter Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia.

BACKGROUND: Because of its low prevalence, data on atypical atrioventricular nodal reentrant tachycardia (AVNRT) are scarce, and the optimal ablation method has not been established. Our study aimed at assessing the efficacy and safety of conventional slow pathway ablation, as applied for typical cases, in atypical AVNRT. METHODS: We studied 2079 patients with AVNRT subjected to slow pathway ablation. In 113 patients, mean age 48.5±18.1 years, 68 female, atypical AVNRT or coexistent atypical and typical AVNRT without other concomitant arrhythmia was diagnosed. Ablation data and outcomes were compared with a group of age- and sex-matched control patients with typical AVNRT. RESULTS: Fluoroscopy and radiofrequency current delivery times were not different in the atypical and typical groups, 20.3±12.2 versus 20.8±12.9 minutes (P=0.730) and 5.9±5.0 versus 5.5±4.5 minutes (P=0.650), respectively. Slow pathway ablation was accomplished from the right septum in 110 patients, and from the left septum in 3 patients, in the atypical group. There was no need for additional ablation lesions at other anatomic sites, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia were 5.6% in the atypical (6/108 patients) and 1.8% in the typical (2/111 patients) groups in the next 3 months following ablation (P=0.167). CONCLUSIONS: Conventional ablation at the anatomic area of the slow pathway is the therapy of choice for symptomatic AVNRT, regardless of whether the typical or atypical form is present.

Catheter ablation vs. antiarrhythmic drug therapy in patients with symptomatic atrioventricular nodal re-entrant tachycardia: a randomized, controlled trial.

AIMS: To conduct a randomized trial in order to guide the optimum therapy of symptomatic atrioventricular nodal re-entrant tachycardia (AVNRT). METHODS AND RESULTS: Patients with at least one symptomatic episode of tachycardia per month and an electrophysiologic diagnosis of AVNRT were randomly assigned to catheter ablation or chronic antiarrhythmic drug (AAD) therapy with bisoprolol (5 mg od) and/or diltiazem (120-300 mg od). All patients were properly educated to treat subsequent tachycardia episodes with autonomic manoeuvres or a 'pill in the pocket' approach. The primary endpoint of the study was hospital admission for persistent tachycardia cardioversion, during a follow-up period of 5 years. Sixty-one patients were included in the study. In the ablation group, 1 patient was lost to follow-up, and 29 were free of arrhythmia or conduction disturbances at a 5-year follow-up. In the AAD group, three patients were lost to follow-up. Of the remainder, 10 patients (35.7%) continued with initial therapy, 11 patients (39.2%) remained on diltiazem alone, and 7 patients (25%) interrupted their therapy within the first 3 months following randomization, and subsequently developed an episode requiring cardioversion. During a follow-up of 5 years, 21 patients in the AAD group required hospital admission for cardioversion. Survival free from the study endpoint was significantly higher in the ablation group compared with the AAD group (log-rank test, P < 0.001). CONCLUSIONS: Catheter ablation is the therapy of choice for symptomatic AVNRT. Antiarrhythmic drug therapy is ineffective and not well tolerated.

Different Prognostic Significance of Cardiac Troponin at Presentation and Peak Cardiac Troponin in Patients with Non-ST Segment Elevation Myocardial Infarction.

OBJECTIVES: Non-ST elevation myocardial infarction (NSTEMI) is one of the most common manifestations of acute coronary syndromes (ACS). We evaluated the prognostic role of cardiac troponin I (cTnI) at presentation and peak cardiac troponin I in patients with NSTEMI. METHODS: We consecutively enrolled 215 subjects presenting with NSTEMI. Subjects were followed up for 1 year. cTnI at presentation and the peak value of cTnI were measured. The primary end point was defined as cardiovascular death, readmission to hospital with heart failure and new ACS. RESULTS: The subjects who presented the primary end point (49 subjects) had significantly increased values of peak cTnI compared to subjects free of cardiovascular events [7.19 (2.97-21.32) vs. 4.09 (1.18-11.85) ng/l; p = 0.002]. Nevertheless, cTnI at presentation did not differ between subjects who presented the primary end point and those free of events (p = 0.39). Multivariate Cox regression analysis after adjustment for confounders revealed by the univariate analysis showed that for an increase in peak cTnI from 1 to 10 ng/l, there is a 60% anticipated increase in the relative risk to present the primary end point (p = 0.04). CONCLUSION: These findings documented the different prognostic significance of cTnI at presentation and peak cTnI in patients presenting with NSTEMI, and highlighted the importance of monitoring the levels of cTnI in this high-risk population.

Apical vs. non-apical right ventricular pacing in cardiac resynchronization therapy: a meta-analysis.

AIMS: Cardiac resynchronization therapy (CRT) has been shown to improve outcomes in patients with heart failure. The optimal site of right ventricular (RV) stimulation in CRT has not been established. We aimed to conduct a meta-analysis of randomized-controlled trials and observational studies comparing the mid- and long-term effects of RV apical (RVA) and non-apical (RVNA) pacing on CRT outcomes. METHODS: We systematically searched the Cochrane library, EMBASE, and MEDLINE databases for studies evaluating RVA vs. RVNA pacing in CRT with regards to left ventricular end-systolic volume (LVESV) reduction, functional status improvement (defined as ≥1 New York Heart Association class improvement), and the clinical outcome of mortality or cardiovascular hospitalization. Effect estimates [standardized mean difference (SMD) and odds ratio (OR) with 95% confidence intervals (CI)] were pooled using random-effect models. RESULTS: Twelve studies comprising 2670 patients (1655 with an apical and 1015 with a non-apical RV lead position) were included. In meta-analyses, LVESV reduction and functional status improvement were similar in patients with RVA and RVNA pacing (SMD 0.13, 95% CI: -0.24 to 0.50, P = 0.48; OR 1.08, 95% CI: 0.81 to 1.45, P = 0.60, respectively). Data regarding mortality and hospitalizations could not be pooled due to a small number of relevant studies with significant heterogeneity. CONCLUSION: Our meta-analysis suggests that in CRT patients the effects of RVA or RVNA pacing on LV remodelling and functional status are similar. Mortality and morbidity outcomes with different RV lead positions should be further assessed in randomized clinical trials.

Relationship between brain natriuretic peptides and recurrence of atrial fibrillation after successful direct current cardioversion: a meta-analysis.

BACKGROUND: Atrial fibrillation (AF) recurrence is common after successful direct current cardioversion (DCCV), with a 40% rate of recurrence within the first month. Several studies have investigated the potential association between brain natriuretic peptide (BNP) or N-terminal (NT)-proBNP levels before DCCV and the risk of AF recurrence, but results have been inconsistent. We, therefore, conducted a systematic review and meta-analysis of all available data to determine whether sinus rhythm (SR) maintenance after successful DCCV may be determined by preprocedural BNP and NT-proBNP levels. METHODS: We systematically searched Scopus, the Cochrane library, EMBASE, and MEDLINE databases to identify publications evaluating BNP or NT-proBNP levels in relation to post-DCCV AF recurrence, indexed from inception to September 2013. Among the initial 1,067 citations, 18 studies fulfilled the specified criteria. The difference in BNP and NT-proBNP concentrations in the AF recurrence and the SR-maintaining group was estimated by the standardized mean difference and the estimates of the pooled outcomes were evaluated using random-effects models. RESULTS: Baseline BNP levels in the AF recurrence group were significantly higher compared to BNP levels in the SR-maintaining group (standardized mean difference [SMD] -1.51, confidence interval [CI] [-2.53, -0.48], P = 0.004). Similar results were observed for NT-proBNP levels, which were significantly higher in the AF recurrence group compared with the SR-maintaining group (SMD -0.63, CI [-1.13, -0.14], P = 0.01). CONCLUSIONS: Our analysis suggests that low preprocedural BNP/NT-proBNP levels are associated with SR maintenance. The use of BNP or NT-proBNP for prediction of long-term response to DCCV appears to be useful and should be further evaluated.

Ticagrelor potentiates cardioprotection by remote ischemic preconditioning: the ticagrelor in remote ischemic preconditioning (TRIP) randomized clinical trial.

OBJECTIVE: Remote ischemic preconditioning (RIPC) reduces periprocedural myocardial injury (PMI) after percutaneous coronary intervention (PCI) through various pathways, including an adenosine-triggered pathway. Ticagrelor inhibits adenosine uptake, thus may potentiate the effects of RIPC. This randomized trial tested the hypothesis that ticagrelor potentiates the effect of RIPC and reduces PMI, assessed by post-procedural troponin release. METHODS: Patients undergoing PCI for non-ST elevation acute coronary syndromes were 1:1 randomized to ticagrelor (TG-Group) or clopidogrel (CL-Group). Within each treatment, patients were 1:1 randomized to a RIPC (RIPC-Group) or a control group (CTRL-Group). The primary endpoint was the difference between post- and pre-procedural troponin at 24 h following PCI, termed deltaTnI. RESULTS: During a 12-month period, 138 patients were included in the study (34 in the CL-CTRL group, 34 in the TG-CTRL group, 35 in the CL-RIPC group, and 35 in the TG-CTRL group). There was a significant difference in deltaTnI between the study groups [ TG-RIPC:0.04 (0-0.16), CL-CTRL:0.10 (0.03-0.43), CLRIPC:0.11 (0.03-0.89), and TG-CTRL:0.24 (0.06-0.47); p = 0.007]. Eight patients (22.9%) in the TG-RIPC group developed type 4a myocardial infarction (MI), compared to 14 (40%) in the CL-RIPC group, 13 (38.2%) in the CL-CTRL group, and 19 (55.9%) in the TG-CTRL group (p = 0.048). A significant interaction between antiplatelet group allocation and RIPC on deltaTnI was observed [F (1,134) = 7.509; p = 0.007]. In multivariate analysis, the interaction between RIPC and ticagrelor treatment was independently associated with a lower incidence of Type 4a MI. CONCLUSION: Our results demonstrate an interaction between ticagrelor and RIPC, which may potentiate the cardioprotective effects of RIPC during PCI by reducing PMI.

Ping-pong guide catheter technique for facilitating antegrade crossing of a chronic total occlusion.

A 60-year-old man was referred for percutaneous coronary intervention of a proximal left circumflex (Cx) chronic total occlusion (CTO) with distal filling via epicardial collaterals from the left anterior descending (LAD) artery.

Box Lesion Isolation of the Left Atrial Posterior Wall with Radiofrequency Ablation Restricted in Predetermined Lines for the Treatment of Persistent Atrial Fibrillation: The Prognostic Role of Acute Interventional Outcome and Trigger Identification.

The left atrial posterior wall (PW) is known to be a critical substrate for the initiation and perpetuation of atrial fibrillation (AF) and has been explored as a target for catheter ablation, particularly in persistent AF (PerAF). In this retrospective study, we investigate the clinical outcome of patients with PerAF who underwent PW isolation (PWI) restricted in predetermined lines in addition to pulmonary vein isolation (PVI). One hundred consecutive patients (64 ± 9.1 years, 66% male, 20% with previous PVI ablation) underwent PWI in a box lesion setting for PerAF lasting >3 months (34% long-standing PerAF). PW triggers were defined as either foci from the PW that repeatedly induced AF or as isolated AF or atrial tachycardia (AT) within the PW. After a mean follow-up period of 25.6 ± 6.7 months, 61% of the patients remained in sinus rhythm after the last procedure. In 79 patients, the PW was successfully isolated, while, in 21 patients, complete isolation was not possible due to failure in completion of the roof line (n = 16), the floor line (n = 7), or both (n = 2). Patients with incomplete isolation had similar AF/AT recurrence rates compared to those with complete PWI. In 12 patients, PW triggers were identified, and PWI in these patients was shown to have a significantly better prognosis in terms of sinus rhythm maintenance (P = .031). Failure of complete PWI does not predispose a patient to an inferior outcome nor is it responsible for iatrogenic ATs. The presence of AF triggers within the PW leads to a particularly favorable result after box lesion isolation.

A simplified differential pacing technique for the evaluation of bidirectional cavo-tricuspid isthmus block during ablation of typical atrial flutter.

PURPOSE: Bidirectional block of the cavo-tricuspid isthmus (CTI) is an established endpoint of CTI-dependent atrial flutter (AFl) ablation. Differential pacing has been used to evaluate the CTI block. The purpose of this study is to describe a modified differential pacing technique to evaluate the CTI block. METHODS: Sixty-two patients underwent radiofrequency (RF) ablation of CTI-dependent AFl. The acute endpoints were non-inducibility of the AFl, and verification of the bidirectional CTI block by our methodology. Pacing was performed in the CS with an ablation catheter positioned immediately lateral to the CTI ablation line, and then 1-2 cm more laterally. The stimulus-to-ablation catheter atrial electrogram intervals were measured at these sites (StimCS-Abl1 and StimCS-Abl2, respectively). Pacing with the ablation catheter also was performed at these 2 sites, and the stimulus-to-CS electrogram intervals (StimABL1-CS and StimABL2-CS) were measured. The criteria for the bidirectional block were StimCS-Abl1 > StimCS-Abl2, and StimABL1-CS > StimABL2-CS. Clinical efficacy was defined as freedom from recurrent AFl during follow-up. RESULTS: Following 12.2 ± 3.7 min of RF delivery across the CTI, intervals were StimCS-Abl1 = 181.2 ± 22.7 ms and StimABL1-CS = 181.0 ± 23.6 ms, and StimCS-Abl2 = 152.2 ± 26.5 ms and StimABL2-CS = 151.2 ± 22.7 (P < 0.001). Atrial flutter was rendered not inducible in all patients, and no procedural complications were encountered. During the next 15.9 ± 0.7 months, two patients were lost to follow-up, and among the 62 other patients, one (1.7%) had flutter recurrence. CONCLUSIONS: The bidirectional CTI block can be assessed quickly and easily using only the ablation and CS catheters for differential pacing.

Spot drug-eluting stenting for long coronary stenoses: long-term results of a randomized clinical study.

BACKGROUND: Preliminary results of a randomized trial have suggested that total lesion coverage with drug-eluting stents (DES) is not necessary in the presence of diffuse disease of nonuniform severity. In the present study, we report long-term results of this trial. METHODS: Consecutive, consenting patients with a long (>20 mm) coronary lesion of nonuniform severity and indication for percutaneous coronary intervention were randomized to full stent coverage of the atherosclerotic lesion with multiple, overlapping (full DES group, n = 90) or spot stenting of the hemodynamically significant parts of the lesion only (defined as diameter stenosis > 50%) (spot DES group, n = 89). RESULTS: At a follow-up of 2-7 years, 30 patients with full DES (33.3%) and 12 patients (13.5%) with spot DES had a major adverse cardiac event (MACE) (P = 0.015). Cox proportional hazard model showed that the risk for MACE was almost 65% lower among patients who were subjected to spot DES compared to those who underwent full DES (HR = 0.35, 95% CI = 0.18-0.68, P = 0.002). This association remained significant even after controlling for age, sex, and lesion length, and the type of stent used (HR = 0.41, 95% CI = 0.20-0.81, P = 0.011). CONCLUSIONS: In the presence of diffuse disease of nonuniform severity, selective stenting of only the significantly stenosed parts of the lesion confers better long-term results compared to total lesion coverage with DES.

The Electrophysiology of Atrial Fibrillation: From Basic Mechanisms to Catheter Ablation.

The electrophysiology of atrial fibrillation (AF) has always been a deep mystery in understanding this complex arrhythmia. The pathophysiological mechanisms of AF are complex and often remain unclear despite extensive research. Therefore, the implementation of basic science knowledge to clinical practice is challenging. After more than 20 years, pulmonary vein isolation (PVI) remains the cornerstone ablation strategy for maintaining the sinus rhythm (SR). However, there is no doubt that, in many cases, especially in persistent and long-standing persistent AF, PVI is not enough, and eventually, the restoration of SR occurs after additional intervention in the rest of the atrial myocardium. Substrate mapping is a modern challenge as it can reveal focal sources or rotational activities that may be responsible for maintaining AF. Whether these areas are actually the cause of the AF maintenance is unknown. If this really happens, then the targeted ablation may be the solution; otherwise, more rough techniques such as atrial compartmentalization may prove to be more effective. In this article, we attempt a broad review of the known pathophysiological mechanisms of AF, and we present the recent efforts of advanced technology initially to reveal the electrical impulse during AF and then to intervene effectively with ablation.

Anatomic and Flow Characteristics of Left Anterior Descending Coronary Artery Angiographic Stenoses Predisposing to Myocardial Infarction.

The impact of the anatomic characteristics of coronary stenoses on the development of future coronary thrombosis has been controversial. This study aimed at identifying the anatomic and flow characteristics of left anterior descending (LAD) coronary artery stenoses that predispose to myocardial infarction, by examining angiograms obtained before the index event. We identified 90 patients with anterior ST-elevation myocardial infarction (STEMI) for whom coronary angiograms and their reconstruction in the three-dimensional space were available at 6 to 12 months before the STEMI, and at the revascularization procedure. The majority of culprit lesions responsible for STEMI occurred between 20 and 40 mm from the LAD ostium, whereas the majority of stable lesions not associated with STEMI were found in distances >60 mm (p < 0.001). Culprit lesions were significantly more stenosed (diameter stenosis 68.6 ± 14.2% vs 44.0 ± 10.4%, p < 0.001), and significantly longer than stable ones (15.3 ± 5.4 mm vs 9.2 ± 2.5 mm, p < 0.001). Bifurcations at culprit lesions were significantly more frequent (88.8%) compared with stable lesions (34.4%, p < 0.001). Computational fluid dynamics simulations demonstrated that hemodynamic conditions in the vicinity of culprit lesions promote coronary thrombosis due to flow recirculation. A multiple logistic regression model with diameter stenosis, lesion length, distance from the LAD ostium, distance from bifurcation, and lesion symmetry, showed excellent accuracy in predicting the development of a culprit lesion (AUC: 0.993 [95% CI: 0.969 to 1.000], p < 0.0001). In conclusion, specific anatomic and hemodynamic characteristics of LAD stenoses identified on coronary angiograms may assist risk stratification of patients by predicting sites of future myocardial infarction.

Incidence, electrophysiological characteristics, and long-term follow-up of perimitral atrial flutter in patients with previously confirmed mitral isthmus block.

INTRODUCTION: After mitral isthmus (ΜΙ) catheter ablation, perimitral atrial flutter (PMF) circuits can be maintained due to the preservation of residual myocardial connections, even if conventional pacing criteria for complete MI block are apparently met (MI pseudo-block). We aimed to study the incidence, the electrophysiological characteristics, and the long-term outcome of these patients. METHODS: Seventy-two consecutive patients (mean age 62.4 ± 10.2, 62.5% male) underwent MI ablation, either as part of an atrial fibrillation (AF) ablation strategy (n = 35), or to treat clinical reentrant atrial tachycardia (AT) (n = 32), or to treat AT that occurred during ablation for AF (n = 5). Ιn all patients, the electrophysiological characteristics of PMF circuits were studied by high-density mapping. RESULTS: Mitral isthmus block was successfully achieved in 69/72 patients (95.6%). Five patients developed PMF after confirming MI block. In these patients, high-density mapping during the PMF showed a breakthrough in MI with extremely low impulse conduction velocity (CV). In contrast, in usual PMF circuits that occurred after AF ablation, the lowest CV of the reentrant circuit was of significantly higher value (0.07 ± 0.02 m/s vs 0.25 ± 0.07 m/s, respectively; P < .001). Patients presented with clinical AT had better prognosis in maintaining sinus rhythm after MI ablation compared with patients presented with AF. CONCLUSION: Perimitral atrial flutter with MI pseudo-block may be present after MI ablation and has specific electrophysiological features characterized by remarkably slow CV in the MI. Thus, even after MI block is achieved, a more detailed mapping in the boundaries of the ablation line or reinduction attempts may be needed to exclude residual conduction.

Inhibition of the renin-angiotensin system for prevention of atrial fibrillation.

Atrial fibrillation (AF) is a source of considerable morbidity and mortality. There has been compelling evidence supporting the role of renin-angiotensin system (RAS) in the genesis and perpetuation of AF through atrial remodeling, and experimental studies have validated the utilization of RAS inhibition for AF prevention. This article reviews clinical trials on the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) for the prevention of AF. Results have been variable, depending on the clinical background of treated patients. ACEIs and ARBs appear beneficial for primary prevention of AF in patients with heart failure, whereas they are not equally effective in hypertensive patients with normal left ventricular function. Furthermore, the use of ACEIs or ARBs for secondary prevention of AF has been found beneficial only after electrical cardioversion. Additional data are needed to establish the potential clinical role of renin-angiotensin inhibition for prevention of AF.

Distal Radial Access for Percutaneous Endovascular Repair of a Radial Artery Pseudoaneurysm.

Percutaneous pseudoaneurysm repair through the ipsilateral ulnar artery is an alternative to surgical repair; however, distal radial access, as described in this case, may offer increased safety.