Remaining challenges in catheter ablation of accessory pathways: rare entity of coronary sinus diverticulum-associated pathways.

INTRODUCTION: A limited number of case reports of coronary sinus (CS) diverticula complicating catheter ablation have been published. METHODS AND RESULTS: We retrospectively analysed 2245 patients who underwent ablation of an accessory pathway (AP) at our institution between 1/11/1993 and 31/10/2016. Eight patients (0.36%) were found to have a CS diverticulum in venography. APs showed a mean antegrade conduction time of 276 ± 23 ms (range 220-310 ms) and a mean retrograde conduction of 301 ± 45 ms (230-350 ms). Four patients had 1 (n = 2), 2 (n = 1), or 3 (n = 1) previously failed ablation attempts. Pathways could not be ablated with a conventional 4 mm tip catheter in 7 of 8 cases. In seven patients, ablation was successful, in two using an 8-mm ablation catheter, in two using cryoablation, and in the remaining three with an irrigated tip ablation catheter. After failed femoral approach, one 9-year-old female was successfully ablated via the right jugular vein. In one 75-year-old female, ablation was not successful. During a mean follow-up of 8.9 ± 6.4 years, all patients remained free of recurrences. CONCLUSION: In inferoseptal pathways, especially with previous failed ablation attempts, venographies of the CS should be performed. After successful ablation long-term prognosis is excellent.

Comparing learning curves of two established "single-shot" devices for ablation of atrial fibrillation.

PURPOSE: We compared the contour of learning curves of two "single-shot" devices used for pulmonary vein isolation (PVI) for safety and procedural data. METHODS: We performed a retrospective analysis comparing the first 60 PVI performed at our center using a pulmonary vein ablation catheter (PVAC) array (39 male, mean age 57 years, 42 paroxysmal AF) to the first 60 first PVI using the Cryoballoon (44 male, mean age 59 years, 22 paroxysmal AF). Both groups were further divided into tertiles, where T1 regroups the first 20 ablations, T2 the following 20, and T3 the last 20 ablations. RESULTS: The mean total procedure time was reduced by 24 min between T1 and T3 for the PVAC and 15 min for the Cryoballoon (p = 0.01). Fluoroscopy increased by 5 min, total ablation time was reduced by 7 min for PVAC (p = 0.02), and both times decreased respectively by 7 and 1 min for the Cryoballoon (p = ns). In the PVAC group, a mean rate of 0.16 (T1: n = 5; T2: n = 2; T3: n = 3) complications was observed while a rate of 0.16 (T1: n = 2; T2: n = 3; T3: n = 4) occurred in the CRYO group (p = ns). Severe complications defined as stroke, pericardial tamponade with need of pericardiocentesis and phrenic nerve palsy occurred in n = 4 in both groups (6.6%). CONCLUSIONS: With either of the systems, no significant differences in the effect of the learning curve on the occurrence of adverse events were observed. However, the PVAC array seemed to have a steeper learning curve for procedure, as well as fluoroscopy time.

Safety profile of multielectrode-phased radiofrequency pulmonary vein ablation catheter and irrigated radiofrequency catheter.

BACKGROUND: Silent cerebral lesions with the multielectrode-phased radiofrequency (RF) pulmonary vein ablation catheter (PVAC(®)) have recently been investigated. However, comparative data on safety in relation to irrigated RF ablation are missing. METHODS AND RESULTS: One hundred and fifty consecutive patients (58 ± 12 years, 56 female) underwent first pulmonary vein isolation (PVI) for atrial fibrillation (61% paroxysmal) using PVAC(®) (PVAC). Procedure data as well as in-hospital complications were compared with 300 matched patients who underwent PVI using irrigated RF (iRF). Procedure duration (148 ± 63 vs. 208 ± 70 min; P < 0.001), RF duration (24 ± 10 vs. 49 ± 25 min; P < 0.001), and fluoroscopy time (21 ± 10 vs. 35 ± 13 min; P < 0.001) were significantly shorter using PVAC. Major complication rates [major bleeding, transitoric ischaemic attack (TIA), and pericardial tamponade] were not significantly different between groups (PVAC, n = 3; 2% vs. iRF n = 17; 6%). Overall complication rate, including minor events, was similar in both groups [n = 21 (14%) vs. n = 48 (16%)]. Most of these were bleeding complications due to vascular access [n = 8 (5.3%) vs. n = 22 (7.3%)], which required surgical intervention in five patients [n = 1 (0.7%) vs. n = 4 (1.3%)]. Pericardial effusion [n = 4 (2.7%) vs. n = 19 (6.3%); pericardial tamponade requiring drainage n = 0 vs. n = 6] occurred more frequently using iRF. Two patients in each group developed a TIA (1.3% vs. 0.6%). Of note, four of five thromboembolic events in the PVAC group (two TIAs and three transient ST elevations during ablation) occurred when all 10 electrodes were used for ablation. CONCLUSION: Pulmonary vein isolation using PVAC as a 'one-shot-system' has a comparable complication rate but a different risk profile. Pericardial effusion and tamponade occurred more frequently using iRF, whereas thromboembolic events were more prevalent using PVAC. Occurrence of clinically relevant thromboembolic events might be reduced by avoidance of electrode 1 and 10 interaction and uninterrupted anticoagulation, whereas contact force sensing for iRF might minimize pericardial effusion.

Idiopathic ventricular outflow tract arrhythmias from the great cardiac vein: challenges and risks of catheter ablation.

INTRODUCTION: Catheter ablation for idiopathic ventricular arrhythmia is well established but epicardial origin, proximity to coronary arteries, and limited accessibility may complicate ablation from the venous system in particular from the great cardiac vein (GCV). METHODS: Between April 2009 and October 2010 14 patients (56 ± 15 years; 9 male) out of a total group of 117 patients with idiopathic outflow tract tachycardias were included undergoing ablation for idiopathic VT or premature ventricular contractions (PVC) originating from GCV. All patients in whom the PVC arose from the GCV were subject to the study. In these patients angiography of the left coronary system was performed with the ablation catheter at the site of earliest activation. RESULTS: Successful ablation was performed in 6/14 (43%) and long-term success was achieved in 5/14 (36%) patients. In 4/14 patients (28.6%) ablation was not performed. In another 4 patients (26.7%), ablation did not abolish the PVC/VT. In the majority, the anatomical proximity to the left coronary system prohibited effective RF application. In 3 patients RF application resulted in a coronary spasm with complete regression as revealed in repeat coronary angiography. CONCLUSION: A relevant proportion idiopathic VT/PVC can safely be ablated from the GCV without significant permanent coronary artery stenosis after RF application. Our data furthermore demonstrate that damage to the coronary artery system is likely to be transient.

[Class I antiarrhythmic drugs: mechanisms, contraindications, and current indications]. / Klasse-I-Antiarrhythmika: Wirkmechanismen, Kontraindikationen und aktuelle Indikationen.

Class I antiarrhythmic drugs are sodium channel inhibitors that act by slowing myocardial conduction and, thus, interrupting or preventing reentrant arrhythmia. Due to proarrhythmic effects and the risk of ventricular tachyarrhythmia, class I antiarrhythmics should not be administered in patients with structural heart disease. Nevertheless, there remains a broad spectrum of arrhythmias--among the most common being atrial fibrillation--that can successfully be treated with class I antiarrhythmic drugs. This review gives an overview on the classification, antiarrhythmic mechanisms, indications, side effects, and application modes of class I antiarrhythmic drugs.

[The ICD as primary prevention. Rare indications]. / ICD-Therapie zur Primärprävention. Seltene Indikationen.

The most frequent cause of sudden cardiac death (SCD) is underlying coronary artery disease. Healthy appearing young individuals are affected in a minority of cases. These individuals are usually diagnosed with electrical or genetically determined structural heart disease. Arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, long and short QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and early repolarization syndrome are generally considered rare underlying causes of SCD in these young patients. Affected patients typically present with syncope or cardiac arrest. Occasionally, disease is diagnosed during family screening. Risk stratification is difficult in this patient population. Risk of sudden death has to be weighed individually against risks associated with an implantable cardioverter defibrillator (ICD) in these young patients.

In-situ SEM indentation studies of the deformation mechanisms in TiN, CrN and TiN/CrN.

In this study, the microstructure and the deformation mechanisms of TiN, CrN and multilayer TiN/CrN thin films on silicon substrates were investigated. Cross-sectional lamellas of nanoindents were prepared by focused ion beam milling to observe by transmission electron microscopy the microstructure of the as-deposited and deformed materials. TiN film exhibits nanocrystalline columns, whereas CrN shows large grains. The TiN/CrN multilayer presents microstructural features typical for both materials. A film hardness of 16.9GPa for CrN, 15.8GPa for TiN and 16.6GPa for TiN/CrN was found by the nanoindentation. Reduced modulus recorded for TiN and CrN reference coatings were 221.54 and 171.1GPa, respectively, and 218.6GPa for the multilayer coating. The deformation mechanisms were observed via in-situ scanning electron microscope nanoindentation. The TiN thin film showed short radial cracks, whereas CrN deformed through pile-up and densification of the material. For TiN/CrN multilayer pile-up and cracks were found. Transmission electron microscopy observations indicated that TiN deforms through grain boundary sliding and CrN via densification and material flow. The deformation mechanism observed in TiN/CrN multilayer was found to be a mixture of both modes.

Verapamil prevents torsade de pointes by reduction of transmural dispersion of repolarization and suppression of early afterdepolarizations in an intact heart model of LQT3.

BACKGROUND: In long QT syndrome (LQTS), prolongation of the QT-interval is associated with sudden cardiac death resulting from potentially life-threatening polymorphic tachycardia of the torsade de pointes (TdP) type. Experimental as well as clinical reports support the hypothesis that calcium channel blockers such as verapamil may be an appropriate therapeutic approach in LQTS. We investigated the electrophysiologic mechanism by which verapamil suppresses TdP, in a recently developed intact heart model of LQT3. METHODS AND RESULTS: In 8 Langendorff-perfused rabbit hearts, veratridine (0.1 microM), an inhibitor of sodium channel inactivation, led to a marked increase in QT-interval and simultaneously recorded monophasic ventricular action potentials (MAPs) (p < 0.05) thereby mimicking LQT3. In bradycardic (AV-blocked) hearts, simultaneous recording of up to eight epi- and endocardial MAPs demonstrated a significant increase in total dispersion of repolarization (56%, p < 0.05) and reverse frequency-dependence. After lowering potassium concentration, veratridine reproducibly led to early afterdepolarizations (EADs) and TdP in 6 of 8 (75%) hearts. Additional infusion of verapamil (0.75 microM) suppressed EADs and consecutively TdP in all hearts. Verapamil significantly shortened endocardial but not epicardial MAPs which resulted in significant reduction of ventricular transmural dispersion of repolarization. CONCLUSIONS: Verapamil is highly effective in preventing TdP via shortening of endocardial MAPs, reduction of left ventricular transmural dispersion of repolarization and suppression of EADs in an intact heart model of LQT3. These data suggest a possible therapeutic role of verapamil in the treatment of LQT3 patients.

Atrioventricular nodal re-entrant tachycardia in a patient with Ebstein anomaly.

The first case of successful slow pathway modulation is reported in a patient with Ebstein anomaly and recurrent atrioventricular nodal re-entrant tachycardia. Typical signals were recorded during electrophysiological study at the slow pathway region between the His bundle and the coronary sinus where ablation was performed successfully. Thus, slow pathway modulation seems to be a safe procedure even in selected patients with Ebstein anomaly.

Differentiation of atypical atrioventricular node re-entrant tachycardia from orthodromic reciprocating tachycardia using a septal accessory pathway by the response to ventricular pacing.

OBJECTIVES: The purpose of this study was to determine whether the response to ventricular pacing during tachycardia is useful for differentiating atypical atrioventricular node re-entrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a septal accessory pathway. BACKGROUND: Although it is usually possible to differentiate atypical AVNRT from ORT using a septal accessory pathway, a definitive diagnosis is occasionally elusive. METHODS: In 30 patients with atypical AVNRT and 44 patients with ORT using a septal accessory pathway, the right ventricle was paced at a cycle length 10 to 40 ms shorter than the tachycardia cycle length (TCL). The ventriculo-atrial (VA) interval and TCL were measured just before pacing. The interval between the last pacing stimulus and the last entrained atrial depolarization (stimulus-atrial [S-A] interval) and the post-pacing interval (PPI) at the right ventricular apex were measured on cessation of ventricular pacing. RESULTS: All 30 patients with atypical AVNRT and none of the 44 patients with ORT using a septal accessory pathway had an S-A-VA interval >85 ms and PPI-TCL >115 ms. CONCLUSIONS: The S-A-VA interval and PPI-TCL are useful in distinguishing atypical AVNRT from ORT using a septal accessory pathway.

Double potentials along the ablation line as a guide to radiofrequency ablation of typical atrial flutter.

OBJECTIVES: The purpose of this study was to determine the characteristics of double potentials (DPs) that are helpful in guiding ablation within the cavo-tricuspid isthmus. BACKGROUND: Double potentials have been considered a reliable criterion of cavo-tricuspid isthmus block in patients undergoing radiofrequency ablation of typical atrial flutter (AFL). However, the minimal degree of separation of the two components of DPs needed to indicate complete block has not been well defined. METHODS: Radiofrequency ablation was performed in 30 patients with isthmus-dependent AFL. Bipolar electrograms were recorded along the ablation line during proximal coronary sinus pacing at sites at which radiofrequency ablation resulted in incomplete or complete isthmus block. RESULTS: Double potentials were observed at 42% of recording sites when there was incomplete isthmus block, compared with 100% of recording sites when the block was complete. The mean intervals separating the two components of DPs were 65 +/- 21 ms and 135 +/- 30 ms during incomplete and complete block, respectively (p < 0.001). An interval separating the two components of DPs (DP(1-2) interval) <90 ms was always associated with a local gap, whereas a DP(1-2) interval > or =110 ms was always associated with local block. When the DP(1-2) interval was between 90 and 110 ms, an isoelectric segment within the DP and a negative polarity in the second component of the DP were helpful in indicating local isthmus block. A DP(1-2) interval > or =90 ms with a maximal variation of 15 ms along the entire ablation line was an indicator of complete block in the cavo-tricuspid isthmus. CONCLUSIONS: Detailed analysis of DPs is helpful in identifying gaps in the ablation line and in distinguishing complete from incomplete isthmus block in patients undergoing radiofrequency ablation of typical AFL.

Incidence and clinical significance of inducible atrial tachycardia in patients with atrioventricular nodal reentrant tachycardia.

INTRODUCTION: The purpose of this prospective study was to determine the prevalence and clinical significance of inducible atrial tachycardia in patients undergoing slow pathway ablation for AV nodal reentrant tachycardia who did not have clinically documented episodes of atrial tachycardia. METHODS AND RESULTS: Twenty-seven (15%) of 176 consecutive patients who underwent slow pathway ablation for AV nodal reentrant tachycardia were found to have inducible atrial tachycardia with a mean cycle length of 351+/-95 msec. The atrial tachycardia was sustained in 7 (26%) of 27 patients and was isoproterenol dependent in 20 patients (74%). The atrial tachycardia was not ablated or treated with medications, and the patients were followed for 9.7+/-5.8 months. Six (22%) of the 27 patients experienced recurrent palpitations during follow-up. In one patient each, the palpitations were found to be due to sustained atrial tachycardia, nonsustained atrial tachycardia, recurrence of AV nodal reentrant tachycardia, paroxysmal atrial fibrillation, sinus tachycardia, and frequent atrial premature depolarizations. Thus, only 2 (7%) of 27 patients with inducible atrial tachycardia later developed symptoms attributable to atrial tachycardia. CONCLUSION: Atrial tachycardia may be induced by atrial pacing in 15% of patients with AV nodal reentrant tachycardia. Because the vast majority of patients do not experience symptomatic atrial tachycardia during follow-up, treatment for atrial tachycardia should be deferred and limited to the occasional patient who later develops symptomatic atrial tachycardia.

Electrogram polarity and cavotricuspid isthmus block during ablation of typical atrial flutter.

INTRODUCTION: The atrial activation sequence around the tricuspid annulus has been used to assess whether complete block has been achieved across the cavotricuspid isthmus during radiofrequency ablation of typical atrial flutter. However, sometimes the atrial activation sequence does not clearly establish the presence or absence of complete block. The purpose of this study was to determine whether a change in the polarity of atrial electrograms recorded near the ablation line is an accurate indicator of complete isthmus block. METHODS AND RESULTS: Radiofrequency ablation was performed in 34 men and 10 women (age 60 +/- 13 years [mean +/- SD]) with isthmus-dependent, counterclockwise atrial flutter. Electrograms were recorded around the tricuspid annulus using a duodecapolar halo catheter. Electrograms recorded from two distal electrode pairs (E1 and E2) positioned just anterior to the ablation line were analyzed during atrial flutter and during coronary sinus pacing, before and after ablation. Complete isthmus block was verified by the presence of widely split double electrograms along the entire ablation line. Complete bidirectional isthmus block was achieved in 39 (89%) of 44 patients. Before ablation, the initial polarity of E1 and E2 was predominantly negative during atrial flutter and predominantly positive during coronary sinus pacing. During incomplete isthmus block, the electrogram polarity became reversed either only at E2, or at neither E1 nor E2. In every patient, the polarity of E1 and E2 became negative during coronary sinus pacing only after complete isthmus block was achieved. In 4 patients (10%), the atrial activation sequence recorded with the halo catheter was consistent with complete isthmus block, but the presence of incomplete block was accurately detected by inspection of the polarity of E1 and E2. CONCLUSION: Reversal of polarity in bipolar electrograms recorded just anterior to the line of isthmus block during coronary sinus pacing after ablation of atrial flutter is a simple, quick, and accurate indicator of complete isthmus block.

Prevalence of central venous occlusion in patients with chronic defibrillator leads.

BACKGROUND: Many patients with previously implanted ventricular defibrillators are candidates for an upgrade to a device capable of atrial-ventricular sequential or multisite pacing. The prevalence of venous occlusion after placement of transvenous defibrillator leads is unknown. The purpose of this study was to determine the prevalence of central venous occlusion in asymptomatic patients with chronic transvenous defibrillator leads. METHODS: Thirty consecutive patients with a transvenous defibrillator lead underwent bilateral contrast venography of the cephalic, axillary, subclavian, and brachiocephalic veins as well as the superior vena cava before an elective defibrillator battery replacement. The mean time between transvenous defibrillator lead implantation and venography was 45 +/- 21 months. Sixteen patients had more than 1 lead in the same subclavian vein. No patient had clinical signs of venous occlusion. RESULTS: One (3%) patient had a complete occlusion of the subclavian vein, 1 (3%) patient had a 90% subclavian vein stenosis, 2 (7%) patients had a 75% to 89% subclavian stenosis, 11 (37%) patients had a 50% to 74% subclavian stenosis, and 15 (50%) patients had no subclavian stenosis. CONCLUSIONS: The low prevalence of subclavian vein occlusion or severe stenosis among defibrillator recipients found in this study suggests that the placement of additional transvenous leads in a patient who already has a ventricular defibrillator is feasible in a high percentage of patients (93%).

Role of transisthmus conduction intervals in predicting bidirectional block after ablation of typical atrial flutter.

INTRODUCTION: Complete bidirectional cavotricuspid isthmus block is the endpoint for ablation of typical atrial flutter. The purpose of this study was to determine whether the extent of prolongation of the transisthmus interval after ablation predicts complete bidirectional block. METHODS AND RESULTS: Fifty-seven consecutive patients underwent 60 ablation procedures for isthmus-dependent atrial flutter. The clockwise and counterclockwise transisthmus intervals were determined before and after ablation during pacing from the low lateral right atrium and the coronary sinus. Bidirectional block was achieved with ablation in 55 (96%) of 57 patients. The transisthmus intervals before ablation and after complete transisthmus block were 100.3 +/- 21.1 msec and 195.8 +/- 30.1 msec, respectively, in the clockwise direction (P < 0.0001), and 98.2 +/- 24.7 msec and 185.7 +/- 33.9 msec, respectively, in the counterclockwise direction (P < 0.0001). An increase in the transisthmus interval by > or = 50% in both directions after ablation predicted complete bidirectional block with 100% sensitivity and 80% specificity. The positive and negative predictive values were 89% and 100%, respectively. The diagnostic accuracy of a > or = 50% prolongation in the transisthmus interval was 92%. CONCLUSION: Prolongation of the transisthmus interval by > or = 50% in the clockwise and counterclockwise directions is associated with a high degree of diagnostic accuracy and an excellent negative predictive value in determining complete bidirectional transisthmus block. This may be a useful and simple adjunctive criterion for assessment of complete transisthmus conduction block.

Complete atrioventricular block after valvular heart surgery and the timing of pacemaker implantation.

The natural history of patients who developed complete atrioventricular block after valvular heart surgery was investigated to determine the optimal timing for pacemaker implantation. Patients who developed complete atrioventricular block within 24 hours after operation, which then persisted for > 48 hours, were unlikely to recover; such patients could potentially undergo earlier pacemaker implantation if otherwise ready for discharge.

Effects of digoxin on acute, atrial fibrillation-induced changes in atrial refractoriness.

BACKGROUND: Atrial fibrillation (AF) shortens the atrial effective refractory period (ERP) and predisposes to further episodes of AF. The acute changes in atrial refractoriness may be related to tachycardia-induced intracellular calcium overload. The purpose of this study was to determine whether digoxin, which increases intracellular calcium, potentiates the acute effects of AF on atrial refractoriness in humans. METHODS AND RESULTS: In 38 healthy adults, atrial ERP was measured at basic drive cycle lengths (BDCLs) of 350 and 500 ms after autonomic blockade. Nineteen patients had been treated with digoxin for 2 weeks. After a several-minute episode of AF, atrial ERP was measured serially at alternating BDCLs. Compared with pre-AF ERPs, the first post-AF ERPs were significantly shorter in both the digoxin and the control groups (P:<0.001). The post-AF ERP at a BDCL of 350 ms shortened to a greater degree in the digoxin group (37+/-16 ms) than in the control group (20+/-13 ms, P:<0.001); similar changes occurred at a BDCL of 500 ms. During post-AF determinations of the atrial ERP, secondary AF episodes occurred significantly more often in the digoxin group (32% versus 16%; P:<0. 04). CONCLUSIONS: After a brief episode of AF, digoxin augments the shortening that occurs in atrial refractoriness and predisposes to the reinduction of AF. These effects occur in the setting of autonomic blockade and therefore are more likely to be due to the effects of digoxin on intracellular calcium than to its vagotonic effects.

Cost analysis of transthoracic cardioversion of atrial fibrillation with and without ibutilide pretreatment.

BACKGROUND: Ibutilide may result in chemical cardioversion of atrial fibrillation and facilitates transthoracic cardioversion by lowering the defibrillation energy requirement. Whether routine pretreatment with ibutilide increases or decreases the cost of cardioversion is unknown. The purpose of this study was to compare the cost of outpatient transthoracic cardioversion of atrial fibrillation with and without ibutilide pretreatment. METHODS: Using a model based on published literature and hospital accounting information, a hypothetical group of 100 patients with atrial fibrillation and a left ventricular ejection fraction >0.30 underwent 2 strategies of outpatient cardioversion: transthoracic cardioversion with and without routine pretreatment with 1 mg ibutilide, and with and without involvement of an anesthesiologist for sedation. If transthoracic cardioversion was unsuccessful in patients who did not receive ibutilide, transthoracic cardioversion was repeated after administration of ibutilide. RESULTS: If an anesthesiologist was involved, transthoracic cardioversion with ibutilide was associated with incremental cost-savings as the efficacy of ibutilide alone in restoring sinus rhythm increased above the critical values of 20%, 27%, and 35% when the efficacy of transthoracic cardioversion alone was 60%, 80%, and 100%, respectively. In the absence of an anesthesiologist, routine pretreatment with ibutilide increased the cost of cardioversion at all success rates of transthoracic cardioversion. CONCLUSIONS: In the presence of an anesthesiologist, whether or not routine pretreatment with ibutilide lowers the mean cost of cardioversion is determined by the success rates of chemical cardioversion with ibutilide and transthoracic cardioversion. In the absence of an anesthesiologist, ibutilide pretreatment increases the cost of cardioversion.