Predictors of Atrial Fibrillation in Patients with Embolic Stroke of Unknown Etiology and Implantable Loop Recorders-Further Insights of the TRACK AF Study on the Role of ECG and Echocardiography

Aims-Electrocardiography (ECG) and echocardiographic left atrial (LA) parameters may be helpful to assess the risk of atrial fibrillation (AF) in embolic stroke of unknown etiology (ESUS) and could therefore guide intensity of ECG monitoring. Methods-1153 consecutive patients with ischemic stroke or transient ischemic attack (TIA) were analyzed. An internal loop recorder (ILR) was implanted in 104 consecutive patients with ESUS. Multiple morphologic P-wave parameters in baseline 12-channel ECG and echocardiographic LA parameters were measured and analyzed in patients with and without ILR-detected AF. Using logistic regression, we evaluated the predictive value of several ECG parameters and LA dimensions on the occurrence of AF. Results-In 20 of 104 (19%) patients, AF was diagnosed by ILR during a mean monitoring time of 575 (IQR 470-580) days. Patients with AF were significantly older (72 (67-75) vs. 60 (52-72) years; p = 0.001) and premature atrial contractions (PAC) were more frequently observed (40% vs. 2%; p < 0.001) during baseline ECG. All morphologic P-wave parameters did not show a significant difference between groups. There was a non-significant trend towards a larger LA volume index (31 (24-36) vs. 29 (25-37) mL/m2; p = 0.09) in AF patients. Conclusions-Age and PAC are independently associated with incident AF in ESUS and could be used as markers for selecting patients that may benefit from more extensive rhythm monitoring or ILR implantation. In our consecutive cohort of patients with ESUS, neither morphological P-wave parameters nor LA size were predictive of AF.

Pregnancy in arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (AC) is a rare heart muscle disease with a genetic background and autosomal dominant mode of transmission. The clinical manifestation is characterized by ventricular arrhythmias (VA), heart failure (HF) and the risk of sudden cardiac death (SCD). Pregnancy in young female patients with AC represents a challenging condition for the life and family planning of young affected women. In addition to genetic mechanisms that influence the complex pathophysiology of AC, experimental and clinical data have confirmed the pathogenetic role of strenuous exercise and competitive sports in the early onset and rapid progression of AC symptoms and complications. Pregnancy and exercise share a number of physiological aspects of adaptation. In AC, both result in ventricular volume overload and myocardial stretch. Therefore, pregnancy has been postulated as a potential risk factor for HF, VA, SCD, and pregnancy-related obstetric complications in patients with AC. However, the available evidence on pregnancy in AC does not confirm this hypothesis. In most women with AC, pregnancies are well tolerated, uneventful, and follow a benign course. Pregnancy-related symptoms (VA, syncope, HF) and mortality, as well as obstetric complications, are uncommon in AC patients and range in the order of background populations and cohorts with AC and no pregnancy. The number of completed pregnancies is not associated with an acceleration of AC pathology or an increased risk of VA or HF during pregnancy and follow-up. Accordingly, there is no medical indication to advise against pregnancy in patients with AC. Preconditions include stability of rhythm and hemodynamics at baseline, as well as clinical follow-ups and the availability of multidisciplinary expert consultation during pregnancy and postpartum. Genetic counseling is recommended prior to pregnancy for all couples and their families affected by AC.

The precordial R-prime wave: a novel discriminator between cardiac sarcoidosis and arrhythmogenic right ventricular cardiomyopathy in patients presenting with ventricular tachycardia

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): The department of cardiology from Leiden University Medical Center receives unrestricted grants from Edwards Lifesciences, Biotronik, Medtronik, Boston Scientific and BioSense Webster. MS was supported by the Research Fellowship of the European Society of Cardiology 2017/2018.

Background Cardiac sarcoidosis (CS) with right ventricular (RV) involvement may mimic ARVC. Histopathological differences may result in disease specific RV activation patterns, detectable on the 12-lead electrocardiogram (ECG). Scar in ARVC progresses from epicardium to endocardium and may lead to delayed activation of areas with reduced voltages, translating into terminal activation delay and occasionally an (epsilon) wave with small amplitude on the ECG. On the contrary, patchy transmural RV scar in CS may lead to conduction block, and therefore late activated areas with preserved voltages, reflected as preserved R’-waves in the right precordial leads.

Purpose To determine whether the terminal activation patterns in precordial leads V1-V3 distinguish CS with RV involvement from ARVC.

Methods This is a multicenter retrospective study including patients with either 1) CS with RV involvement or 2) gene-positive ARVC referred for VT ablation. A non-ventricular paced 12-lead surface ECG prior to ablation was obtained (25mm/s and 10mm/mV). For detailed analysis, Leiden ECG Analysis and Decomposition Software (LEADS) was used. After detection of QRST complexes in the spatial velocity signal, LEADS generates a representative and low-noise averaged beat. Then, measurements per lead were performed using the measurement tool in Adobe Pro DC. Based on the hypothesis that conduction block in CS will lead to late activated areas with preserved voltages, we measured the surface area (SA) of the R’-wave in V1-V3. An R’-wave was defined as any positive deflection from baseline after an S-wave.

Results 13 CS patients with RV involvement (54 ± 8years, 62% male) and 23 ARVC patients (37 ± 15years, 78% male) were included. A R’-wave in V1-V3 was present in all CS patients, compared to 11 (48%) of ARVC patients (p = 0.002). The maximum R’-wave SA in lead V1-V3 was 3.55 (IQR:2.18-5.81) mm2 in CS vs. 0.00 (IQR:0.00-0.43) mm2 in ARVC (p &lt; 0.001; Figure A). By ROC-analysis, the maximum R’-wave SA in lead V1-V3 was an excellent discriminator (area under the curve 0.980 [95%CI: 0.945-1.000]). A cutoff of ≥1.65mm2 had a sensitivity of 85% and specificity of 96% for diagnosing CS. An algorithm was created including the presence of an R’-wave in V1-V3 and the SA of this R’-wave (Figure B). This was validated in a second cohort (18 CS and 40 ARVC) with 72% sensitivity and 88% specificity.

Conclusion Transmural RV scars in CS may cause localized conduction block, leading to late activated areas with preserved voltages, reflected as large R’-wave on the 12-lead surface ECG. An easily applicable algorithm including the surface area of the largest R’-wave in lead V1-V3 ≥1.65mm2 distinguishes CS from ARVC with good sensitivity and specificity. The QRS terminal activation in precordial leads V1-V2 may reflect disease specific scar patterns (for examples: Figure C). Abstract Figure

The precordial R' wave: A novel discriminator between cardiac sarcoidosis and arrhythmogenic right ventricular cardiomyopathy in patients presenting with ventricular tachycardia

BACKGROUND

Cardiac sarcoidosis (CS) with right ventricular (RV) involvement can mimic arrhythmogenic right ventricular cardiomyopathy (ARVC). Histopathological differences may result in disease-specific RV activation patterns detectable on the 12-lead electrocardiogram. Dominant subepicardial scar in ARVC leads to delayed activation of areas with reduced voltages, translating into terminal activation delay and occasionally (epsilon) waves with a small amplitude. Conversely, patchy transmural RV scar in CS may lead to conduction block and therefore late activated areas with preserved voltages reflected as preserved R' waves.

OBJECTIVE

The purpose of this study was to evaluate the distinct terminal activation patterns in precordial leads V₁ through V₃ as a discriminator between CS and ARVC.

METHODS

Thirteen patients with CS affecting the RV and 23 patients with gene-positive ARVC referred for ventricular tachycardia ablation were retrospectively included in a multicenter approach. A non-ventricular-paced 12-lead surface electrocardiogram was analyzed for the presence and the surface area of the R' wave (any positive deflection from baseline after an S wave) in leads V₁ through V₃.

RESULTS

An R' wave in leads V₁ through V₃ was present in all patients with CS compared to 11 (48%) patients with ARVC (P = .002). An algorithm including a PR interval of ≥220 ms, the presence of an R' wave, and the surface area of the maximum R' wave in leads V₁ through V₃ of ≥1.65 mm² had 85% sensitivity and 96% specificity for diagnosing CS, validated in a second cohort (18 CS and 40 ARVC) with 83% sensitivity and 88% specificity.

CONCLUSION

An easily applicable algorithm including PR prolongation and the surface area of the maximum R' wave in leads V₁ through V₃ of ≥1.65 mm² distinguishes CS from ARVC. This QRS terminal activation in precordial leads V₁ through V₃ may reflect disease-specific scar patterns.

Pre-procedural proton pump inhibition is associated with fewer peri-oesophageal lesions after cryoballoon pulmonary vein isolation

Pulmonary vein isolation (PVI) using cryoenergy is safe and efficient for treatment of atrial fibrillation (AF). Pre-existing upper gastrointestinal (GI) pathologies have been shown to increase the risk for AF. Therefore, this study aimed at assessing incidental pathologies of the upper GI tract in patients scheduled for PVI and to analyse the impact of patients’ characteristics on PVI safety outcome. In 71 AF patients, who participated in the MADE-PVI trial, oesophagogastroduodenoscopy and endosonography were prospectively performed directly before and the day after PVI to assess pre-existing upper GI pathologies and post-interventional occurrence of PVI-associated lesions. Subgroup analysis of the MADE-PVI trial identified clinically relevant incidental findings in 53 patients (74.6%) with age > 50 years being a significant risk factor. Pre-existing reflux oesophagitis increased risk for PVI-associated mediastinal oedema, while patients already treated with proton pump inhibitors (PPI) had significantly fewer mediastinal oedema. Our results suggest that AF patients with pre-existing reflux oesophagitis are at higher risk for PVI-associated mediastinal lesions, which is decreased in patients with constant PPI-treatment prior to PVI. Since PVI-associated mediastinal lesions are regarded as surrogate parameter for an increased risk of the fatal complication of an oesophago-atrial fistula, our findings hint at a beneficial effect of pre-interventional prophylactic PPI-treatment to reduce risk for PVI-associated complications.

German Clinical Trials Register (DRKS00016006; date of registration: 17/12/2018).

Predictors of AVNRT Recurrence After Slow Pathway Modification

Atrioventricular nodal reentry tachycardia (AVNRT) is the most common regular supraventricular tachycardia (SVT). Slow pathway modification (SPM) is the accepted first line treatment with reported success rates around 95%. Information regarding possible predictors of AVNRT recurrence is scarce.Out of 4170 consecutive patients with SPM in our department from 1993-2018, we identified 78 patients (1.9%) receiving > 1 SPM (69% female, median age 50 years) with a recurrence of AVNRT after a successful SPM. We matched these patients for age, gender and number of radiofrequency applications during first SPM with 78 patients who received one successful SPM in our center without AVNRT recurrence. Both groups were analyzed for possible predictors of a recurrence of AVNRT during long-term follow-up. The recurrence group contained a significantly lower proportion of patients with an occurrence of junctional beats during SPM (69% versus 89%, P = 0.006). Moreover, significantly more cases of previously diagnosed atrial fibrillation/tachycardia (AF/AT; 21% versus 5%, P = 0.007) and inducible AF/AT during electrophysiology study (23% versus 6%, P = 0.006) were present in the recurrence group. While more than half of patients had a recurrence within the first year, in 20% symptoms reappeared ≥ 4 years after ablation.In a small percentage of patients, AVNRT recurs after an initially successful ablation. Interestingly, these patients had significantly fewer junctional beats during ablation and a higher rate of other (inducible) arrhythmias. AVNRT recurrence spanned a considerable timeframe and should remain a differential diagnosis, even years after ablation.

Ablation of paroxysmal and persistent atrial fibrillation in the very elderly real-world data on safety and efficacy

Background

The role and technique of catheter ablation of atrial fibrillation (AF) in the elderly is unclear. While in young patients pulmonary vein isolation (PVI) has evolved as first option, in older patients decision is often made in favor of drugs as higher complication rates and less benefit are suspected. Therefore, data on PVI of paroxysmal and persistent AF in these patients is still sparse but of eminent importance.

Hypothesis

PVI is comparably safe in the very elderly with similar recurrence and complication rates.

Methods

We enrolled all patients (n = 146) aged >75 years who underwent a first PVI over a period of 10 years (2009‐2019) from our prospective single‐center ablation registry. Mean follow‐up time was 231 ± 399 days.

Results

Acute ablation success defined as complete PVI and sinus rhythm at the end of the ablation procedure was high (99%). Severe periprocedural complications occurred in 3.3% (stroke/TIA n = 2; 1.3%; pericardial effusion n = 3; 2%). In 4.6% of patients symptomatic sick‐sinus‐syndrome was unmasked after PVI resulting in pacemaker implantation. There were no deaths related to PVI. Recurrence rate of symptomatic AF was 37.3% resulting in a Re‐PVI and/or substrate ablation in 32 pts (20.9%). During follow‐up pacemaker implantation plus atrioventricular node ablation was performed in 10 pts (6.8%). There was a trend toward lower recurrence rates with single‐shot devices (cryoballoon, multielectrode phased‐radiofrequency ablation catheter) than with point‐by‐point radiofrequency while complication rates did not differ.

Conclusion

PVI for AF is a feasible treatment option also in patients >75 years with a reasonable success and safety profile. Higher success rates occurred in patients treated with a single‐shot device as compared to point‐by‐point ablation.

The ECG in sarcoidosis - a marker of cardiac involvement? Current evidence and clinical implications

Sarcoidosis is a multisystem granulomatous disease of unknown etiology characterized by noncaseating granulomas. Cardiac involvement is often limiting patients' prognosis. Cardiac sarcoidosis can manifest with variant cardiac arrhythmias, of which atrioventricular (AV)-block-related bradycardia and ventricular tachycardias are the most common. Although cardiac sarcoidosis remains a histopathological diagnosis, the significance of imaging modalities, especially cardiac magnetic resonance imaging is increasing rapidly but mainly remains reserved for patients with a high suspicion due to a previous arrhythmia or unknown cardiomyopathy. Thus, there is a need for screening in daily clinical practice so that possible characteristic electrocardiographic (ECG) findings may guide the way to detect the disease. We therefore evaluated the ECG as a potential tool for screening of cardiac sarcoidosis and present different electrophysiological manifestations of cardiac sarcoidosis based on a literature review. The ECG is a valuable tool for screening of cardiac involvement in patients with sarcoidosis. Several parameters have been shown to be associated with cardiac involvement in sarcoidosis such as higher-degree AV-block, QRS complex fragmentation and widening, as well as certain T wave abnormalities that may indicate cardiac involvement, of which the latter two are most promising and specific. However, prospective studies examining a large number of trials are desirable.

Outcome of catheter ablation in the very elderly-insights from a large matched analysis

Background

Ablation emerged as first line therapy in the treatment of various arrhythmias. Nevertheless, in older patients (pts), decision is often made pro drug treatment as more complications and less benefit are suspected.

Hypothesis

We hypothesized that different kind of ablations can be performed safely regardless of the pts age.

Methods

We enrolled all pts aged >80 years (yrs) who underwent ablation for three different arrhythmias (atrial flutter [AFL], atrioventricular nodal re‐entry tachycardia [AVNRT], ventricular tachycardia [VT]) between August 2002 and December 2018. Procedural data and outcome were compared with matched groups aged 60 to 80 years and 40 to 60 years, respectively. Periprocedural and in‐hospital complications were analyzed.

Results

The analysis included 1191 patients (397 pts per group: 63% AFL, 23% AVNRT, 14% VT) who underwent ablation. Acute success was high in all types of arrhythmias irrespective of age (>80, 60‐80, 40‐60 years: AFL 97%/98%/98%, AVNRT 97%/95%/97%, VT 82%/86%/93%). Rate of periprocedural complications were similar in all groups treated for AFL and AVNRT. For VT ablations significant differences were noted between pts > 80 or 60 to 80 years and those aged 40‐60 years (16.1%/14.3%/3.6%). Most complications were infections and groin haematoma. No strokes, iatrogenic atrioventricular blocks and deaths related to the ablation occurred.

Conclusion

Ablation appears safe in pts > 80 years. Success rates were comparable to matched younger cohorts. A significant difference was observed for VT patients.

One-Year Course of Periprocedural Anticoagulation in Atrial Fibrillation Ablation: Results of a German Nationwide Survey

INTRODUCTION

Periprocedural oral anticoagulation (OAC) strategies for atrial fibrillation (AF) ablation procedures are changing rapidly.

OBJECTIVE

To assess the management and course of periprocedural OAC for AF ablation procedures in experienced electrophysiology (EP) centers in Germany over the last 12 months.

METHODS

The data are based on an electronic questionnaire, which was sent to 35 experienced EP centers in September 2018 and then exactly 1 year later. Participants provided information on their periprocedural OAC management, the handling with dual therapy (OAC plus single antiplatelet therapy), the availability of specific antidotes, the transseptal puncture approach, and noteworthy complications.

RESULTS

Responses were received from all 35 centers and represent 10,010 AF ablation procedures annually. In 2018, the administration of vitamin K antagonist (VKA) was continued throughout the procedure at all centers (100%). In contrast, the majority of centers used minimally interrupted periprocedural non-vitamin K antagonist oral anticoagulants (NOAC) (54.3%), 13 centers (37.2%) completely interrupted NOAC, and only 3 centers (8.5%) continued NOAC throughout the procedure. At the 1-year follow-up survey, 32 centers were found to have continued their previous strategy of periprocedural OAC and 3 changed from a minimally interrupted to a continued NOAC strategy. Of note, 30 centers (85.7%) performed transseptal puncture fluoroscopically without additional cardiac imaging. In the setting of uninterrupted periprocedural OAC management, no relevant complications were noted.

CONCLUSION

Our survey shows marked heterogeneous periprocedural OAC management at experienced EP centers in Germany. Whereas continuation of VKA has already been integrated into clinical practice, the majority of centers still use a minimally interrupted NOAC strategy.

Efficacy and complications of cavo-tricuspid isthmus-dependent atrial flutter ablation in patients with and without structural heart disease: results from the German Ablation Registry

BACKGROUND

The impact of structural heart disease (SHD) on safety and efficacy of catheter ablation of cavo-tricuspid isthmus-dependent atrial flutter (AFLU) is unclear. In addition, recent data suggest a higher complication rate of AFLU ablation compared to the more complex atrial fibrillation (AF) ablation procedure.

METHODS AND RESULTS

Within our prospective multicenter registry, 3526 consecutive patients underwent AFLU ablation at 49 German electrophysiological centers from 2007 to 2010. For the present analysis, the patients were divided into a group with SHD (n = 2164 [61.4%]; median age 69 years; 78.5% male) and a group without SHD (n = 1362 [38.6%]; 65 years; 70.3% male). In our study, SHD mainly encompasses coronary artery disease (52.6%), left ventricular ejection fraction ≤ 50% (47.6%), and hypertensive heart disease (28.0%). The primary ablation success (97%) and the incidence of major (0.2%) or moderate (1.2%) complications did not differ significantly between the two groups (P = 1.0 and 0.87, respectively). Vascular access site complications (0.6%), AV block III° (0.2%), and bleeding (≥ BARC II: 0.2%) were most common. After a median 562 days of follow-up, we observed a 2.92-fold higher one-year mortality (P < 0.0001) in patients with SHD. Patients' satisfaction with the ablation therapy (72.0% satisfied) was close to the overall subjective tachyarrhythmia-free rate (70.7%).

CONCLUSIONS

The present analysis demonstrates that ablation of cavo-tricuspid isthmus dependent AFLU in patients with SHD has a comparable, excellent risk-benefit profile in our large "real-world" registry. Mortality rates expectedly are higher in patients with SHD and AFLU compared to patients without SHD. CLINICALTRIALS.GOV: NCT01197638, http://clinicaltrials.gov/ct2/show/NCT01197638.

Prospective blinded Evaluation of the smartphone-based AliveCor Kardia ECG monitor for Atrial Fibrillation detection: The PEAK-AF study

INTRODUCTION

The AliveCor Kardia ECG monitor (ACK) offers a smartphone-based one-lead ECG recording for the detection of atrial fibrillation. We compared ACK lead I recordings with the 12-lead ECG and introduce a novel parasternal lead (NPL).

METHODS

Consecutive cardiac inpatients were recruited. In all patients a 12-lead ECG, ACK lead I and NPL were obtained. Two experienced electrophysiologists were blinded and separately evaluated all ECG. We calculated sensitivity, specificity, and predictive values of the ACK ECG compared to the 12-lead ECG.

RESULTS

296 ECG from 99 patients (38 female, age 64 ± 15 years, BMI 27.8 ± 5.1 kg/m²) were analyzed. 20% of ACK lead I recordings contained a critical amount of artifact. The electrophysiologists' interpretation of the ACK recordings yielded a sensitivity of 100% and specificity of 94% for atrial fibrillation or flutter in lead I (κ = 0.90) and a sensitivity of 96% and specificity of 97% in the NPL (κ = 0.92). The ACK diagnostic algorithm displayed a significantly lower sensitivity (55-70%), specificity (60-69%), and accuracy (κ = 0.4-0.53) but a high negative predictive value (100%). Patients with atrial flutter (n = 5) and with ventricular stimulation (n = 12) had a high likelihood of being misclassified by the algorithm.

CONCLUSION

The AliveCor Kardia ECG monitor allows a highly accurate detection of atrial fibrillation by an interpreting electrophysiologist both in the standard lead I and a novel parasternal lead. The diagnostic algorithm offered by the system may be useful in screening recordings for further review. Diagnostic challenges present in atrial flutter and ventricular pacemaker stimulation.

Acute electrophysiologic effects of the polyphenols resveratrol and piceatannol in rabbit atria

The natural polyphenol resveratrol and its analogue piceatannol have various beneficial effects including antiarrhythmic properties. The aim of the present study was to examine potential electrophysiologic effects in an experimental whole-heart model of atrial fibrillation (AF). Simultaneous infusion of resveratrol (50 μmol/L) or piceatannol (10 μmol/L) in rabbit hearts resulted in an increase in atrial refractory period. Both agents induced a significant slowing of atrial conduction and of intrinsic heart rate. In both groups, a trend toward a reduction in AF and a regularization of AF was observed.

P342Time-to-isolation-guided cryoballoon pulmonary vein isolation reduces esophageal and mediastinal alterations detected by endoscopic ultrasound

Background

Pulmonary vein isolation (PVI) is recommended for treatment of symptomatic atrial fibrillation. Cryoballoon ablation is an emerging safe and efficient technique for achieving PVI. Nevertheless, structural alterations of the mediastinum and/or the oesophagus, which seem to be associated with an increased risk of the lethal complication of an atrio-oesophageal fistula, have been described.

Purpose

MADE-PVI (Mediastino-oesophageal Alterations Detected by Endosonography after PVI) aimed at evaluating safety of cryoballoon PVI in relation to two different freeze protocols. As a time-to-isolation (TTI)-guided protocol has been reported to be as effective as a conventional “two freeze protocol”, we hypothesized that a TTI-guided protocol causes less peri-atrial and -oesophageal lesions.

Methods

70 consecutive patients were scheduled for de novo cryoballoon (2nd generation) PVI employing either a conventional freeze protocol (Group A: n=35: 2x180s per vein) or a TTI-guided approach (Group B: n=35; freeze time: TTI+120s per vein or 1x180s in case TTI could not be measured). Structural oesophageal and mediastinal alterations (e.g. ulceration, oedema) were assessed by endoscopy and endosonography blinded prior and post ablation.

Results

Irrespective of used freeze protocol, ablation significantly increased atrio-oesophageal distances, including distance to left and right inferior pulmonary vein ostia as well as to the posterior wall of the left atrium (all p<0.001). In general, postinterventional mediastinal oedematous alterations were detected in 47 patients (70%) with a mean size of 14mm (± 0.9 mm), while only 10 patients (15%) revealed a large mediastinal oedema >20mm. Oesophageal thermal lesions occurred in 3 patients (4%) including 1 deep ulceration, which coincided with a large mediastinal oedema. The two freeze protocols had a distinct impact on mediastinal lesions as mean size of oedematous alterations and occurrence of large mediastinal oedema were significantly increased in Group A vs. Group B (17 mm vs. 11 mm, p<0.001; 26% vs. 6%, p=0.029). Furthermore, every oesophageal lesion was detected in patients in group A. Nonetheless, no major complication occurred in either group.

Conclusions

The present prospective study clearly demonstrates a significant impact of freeze protocol on post-interventional mediastino-oesophageal alterations. A TTI-guided protocol employing 2nd generation cryoballoon reduces mediastino-oesophageal lesions and may reduce complications.

Acknowledgement/Funding

This study was supported by Medtronic by an unrestricted grant (A 1351459).

Outcome of catheter ablation of supraventricular tachyarrhythmias in cardiac sarcoidosis

Background

Sarcoidosis is a multisystem granulomatous disease of not sufficiently understood origin. Some patients develop cardiac involvement in course of the disease which is mostly responsible for adverse outcome. In addition to complications like high degree atrioventricular (AV) block or ventricular tachyarrhythmias, there is a certain percentage of patients developing atrial tachyarrhythmias. Data is limited and the role of catheter ablation uncertain. Therefore, we studied sarcoid patients who presented with supraventricular tachyarrhythmias.

Hypothesis

Treatment and ablation of supraventricular tachycardia could be hampered by inflammation in patients with cardiac sarcoidosis.

Methods

We enrolled 37 consecutive patients with cardiac sarcoidosis who presented with atrial tachyarrhythmias and underwent an electrophysiologic study over a period of 6 years (03/2013‐04/2019). In total, 16 catheter ablations for atrial tachyarrhythmias were performed. Mean follow‐up duration was 2.5 years.

Results

Most common ablation performed was cavo‐tricuspid isthmus ablation for typical atrial flutter in seven patients (54%). Pulmonary vein isolation for treatment of atrial fibrillation (AF) was performed in five patients (38%). Two patients received slow‐pathway modulation for treatment of recurrent atrioventricular nodal reentry tachycardia (AVNRT). All but two patients with AF had no clinical recurrence during follow‐up. Two patients had recurrence of AF but still reported markedly improved european heart rhythm association (EHRA) class. Periprocedural safety was very high. There were no adverse events related to the ablation procedure. One patient died during follow‐up in the presence of electrical storm.

Conclusion

Catheter ablations of supraventricular tachycardias seem to be safe and effective in patients with cardiac sarcoidosis. Outcome is comparable to patients without inflammatory heart disease, although data from larger patient collectives are mandatory to make recommendations in this special entity.

Antiarrhythmic effect of antazoline in experimental models of acquired short- and long-QT-syndromes

Aims

Antazoline is a first-generation antihistamine with antiarrhythmic properties. This study examines potential electrophysiological effects of antazoline in short-QT-syndrome (SQTS) and long-QT-syndrome (LQTS).

Methods and results

Sixty-five rabbit hearts were Langendorff-perfused. Action potential duration at 90% of repolarization (APD90), QT-interval, spatial dispersion (DISP), and effective refractory period (ERP) were measured. The IK, ATP-opener pinacidil (1 µM, n = 14) reduced APD90 (-14 ms, P < 0.01), QT-interval (-14 ms, P < 0.01), and ERP (-11 ms, P < 0.01), thus simulating acquired SQTS. Additional infusion of 20 µM antazoline prolonged repolarization. Under baseline conditions, ventricular fibrillation (VF) was inducible in 5 of 14 hearts (10 episodes) and in 5 of 14 pinacidil-treated hearts (21 episodes, P = ns). Antazoline significantly reduced induction of VF (0 episodes, P < 0.05 each). Further 17 hearts were perfused with 100 µM sotalol and 17 hearts with 300 µM erythromycin to induce acquired LQTS2. In both groups, prolongation of APD90, QT-interval, and ERP was observed. Spatial dispersion was increased (sotalol: +26 ms, P < 0.01; erythromycin: +31 ms, P < 0.01). Additional infusion of antazoline reduced DISP (sotalol: -22 ms, P < 0.01; erythromycin: -26 ms, P < 0.01). Torsade de pointes (TdP) occurred in 6 of 17 sotalol-treated (22 episodes, P < 0.05 each) and in 8 of 17 erythromycin-treated hearts (96 episodes P < 0.05 each). Additional infusion of antazoline completely suppressed TdP in both groups (P < 0.05 each). Acquired LQTS3 was induced by veratridine (0.5 µM, n = 17) and similar results were obtained (APD90: +24 ms, P < 0.01, QT-interval: +58 ms, P < 0.01, DISP: +38 ms, P < 0.01). Torsade de pointes occurred in 10 of 17 hearts (41 episodes, P < 0.05 each). Antazoline significantly reduced TdP (2 of 17 hearts, 4 episodes, P < 0.05 each).

Conclusion

Antazoline significantly reduced induction of VF in an experimental model of acquired SQTS. In three experimental models of acquired LQTS, antazoline effectively suppressed TdP.

Time-to-isolation-guided cryoballoon ablation reduces oesophageal and mediastinal alterations detected by endoscopic ultrasound: results of the MADE-PVI trial

Aims

Cryoballoon ablation is safe and efficient for achieving pulmonary vein isolation (PVI) in atrial fibrillation. Structural oesophago-mediastinal lesions, which seem to be associated with an increased risk of the lethal complication of an atrio-oesophageal fistula, have been described. MADE-PVI (Mediastino-oesophageal Alterations Detected by Endosonography after PVI) aimed at evaluating safety of cryoballoon PVI in relation to two different freeze protocols. As time-to-isolation-(TTI)-guided protocol has been reported to be as effective as conventional ‘two freeze protocol’, we hypothesized a TTI-guided protocol causes less oesophago-mediastinal lesions.

Methods and results

Seventy consecutive patients were scheduled for cryoballoon (2nd generation) PVI employing either a conventional protocol (n = 35: 2 × 180 s per vein) or a TTI-guided approach (n = 35: TTI + 120 s per vein or 1 × 180 s in case TTI could not be measured). Oesophagogastroduodenoscopy and endoscopic ultrasound, assessing oesophago-mediastinal alterations (e.g. ulceration, oedema) were performed blinded prior and post-ablation. Post-interventional mediastinal oedematous alterations were detected in 70% with a mean diameter of 14 mm (±0.9 mm), while only 15% revealed large mediastinal oedema >20 mm. Oesophageal lesions due to PVI occurred in 5%. Freeze protocols had a distinct impact on oesophago-mediastinal alterations as mean diameter and frequency of large oedema were significantly increased in patients after conventional protocol PVI (17 mm vs. 11 mm; 26% vs. 6%). Furthermore, every oesophageal lesion was detected in patients with conventional protocol (9%). No major complication occurred in either group.

Conclusion

The present prospective study demonstrates a significant impact of freeze protocol on oesophago-mediastinal alterations. A TTI-guided protocol reduces mediastino-oesophageal lesions and may reduce short- and long-term complications of cryoballoon PVI.

Spotlight on S-ICD™ therapy: 10 years of clinical experience and innovation

Subcutaneous ICD (S-ICD™) therapy has been established in initial clinical trials and current international guideline recommendations for patients without demand for pacing, cardiac resynchronization, or antitachycardia pacing. The promising experience in ‘ideal’ S-ICD™ candidates increasingly encourages physicians to provide the benefits of S-ICD™ therapy to patients in clinical constellations beyond ‘classical’ indications of S-ICD™ therapy, which has led to a broadening of S-ICD™ indications in many centres. However, the decision for S-ICD™ implantation is still not covered by controlled randomized trials but rather relies on patient series or observational studies. Thus, this review intends to give a contemporary update on available empirical evidence data and technical advancements of S-ICD™ technology and sheds a spotlight on S-ICD™ therapy in recently discovered fields of indication beyond ideal preconditions. We discuss the eligibility for S-ICD™ therapy in Brugada syndrome as an example for an adverse and dynamic electrocardiographic pattern that challenges the S-ICD™ sensing and detection algorithms. Besides, the S-ICD™ performance and defibrillation efficacy in conditions of adverse structural remodelling as exemplified for hypertrophic cardiomyopathy is discussed. In addition, we review recent data on potential device interactions between S-ICD™ systems and other implantable cardio-active systems (e.g. pacemakers) including specific recommendations, how these could be prevented. Finally, we evaluate limitations of S-ICD™ therapy in adverse patient constitutions, like distinct obesity, and present contemporary strategies to assure proper S-ICD™ performance in these patients. Overall, the S-ICD™ performance is promising even for many patients, who may not be ‘classical’ candidates for this technology.

Additive Proarrhythmic Effect of Combined Treatment with QT-Prolonging Agents

Drug combinations may elevate the risk of proarrhythmia. The aim of the present study was to investigate whether combinations of non-cardiovascular agents induce an additive increase in the proarrhythmic risk. In 12 female rabbit hearts, a drug combination of cotrimoxazole (300 µM), ondansetron (5 µM) and domperidone (1 µM) was infused after obtaining baseline data. In another 13 hearts, a combination of cotrimoxazole (300 µM), ondansetron (5 µM) and erythromycin (300 µM) was infused. Monophasic action potentials and ECG displayed a significant QT prolongation in all groups. This was accompanied by a significant increase in action potential duration. Of note, addition of each drug resulted in a further increase in the QT interval. Furthermore, a significant elevation of spatial dispersion of repolarization was observed. Lowering of potassium concentration in bradycardic AV-blocked hearts provoked early afterdepolarizations and torsade de pointes (TDP) in both study groups. Under baseline conditions, no episodes of TDP recorded. After administration of the first agent, TDP occurred in 5 of 12 hearts (37 episodes) and 5 of 13 hearts (26 episodes), respectively. After additional infusion of the second drug, TDP were recorded in 7 of 12 hearts (55 episodes) and 8 of 13 hearts (111 episodes). After additional infusion of the third drug, TDP occurred in 11 of 12 hearts (118 episodes) and 9 of 13 hearts (88 episodes). Combined treatment with several non-cardiovascular QT-prolonging agents resulted in a remarkable occurrence of proarrhythmia. An additive and significant prolongation of cardiac repolarization combined with an increased spatial dispersion of repolarization represents the underlying electrophysiological mechanism.

Catheter ablation for ventricular tachycardia in patients with cardiac sarcoidosis: a systematic review

Aims

Cardiac sarcoidosis (CS) is associated with a poor prognosis. Important features of CS include heart failure, conduction abnormalities, and ventricular arrhythmias. Ventricular tachycardia (VT) is often refractory to antiarrhythmic drugs (AAD) and immunosuppression. Catheter ablation has emerged as a treatment option for recurrent VT. However, data on the efficacy and outcomes of VT ablation in this context are sparse.

Methods and results

A systematic search was performed on PubMed, EMBASE, and Cochrane database (from inception to September 2016) with included studies providing a minimum of information on CS patients undergoing VT ablation: age, gender, VT cycle length, CS diagnosis criteria, and baseline medications. Five studies reporting on 83 patients were identified. The mean age of patients was 50 ± 8 years, 53/30 (males/females) with a maximum of 56 patients receiving immunosuppressive therapy, mean ejection fraction was 39.1 ± 3.1% and 94% had an implantable cardioverter defibrillator in situ. The median number of VTs was 3 (2.6-4.9)/patient, mean cycle length of 360 ms (326-400 ms). Hundred percent of VTs received endocardial ablation, and 18% required epicardial ablation. The complication rates were 4.7-6.3%. Relapse occurred in 45 (54.2%) patients with an incidence of relapse 0.33 (95% confidence interval 0.108-0.551, P < 0.004). Employing a less stringent endpoint (i.e. freedom from arrhythmia or reduction of ventricular arrhythmia burden), 61 (88.4%) patients improved following ablation.

Conclusions

These data support the utilization of catheter ablation in selected CS cases resistant to medical treatment. However, data are derived from observational non-controlled case series, with low-methodological quality. Therefore, future well-designed, randomized controlled trials, or large-scale registries are required.

Distinct Occurrence of Proarrhythmic Afterdepolarizations in Atrial Versus Ventricular Cardiomyocytes: Implications for Translational Research on Atrial Arrhythmia

Background: Principal mechanisms of arrhythmia have been derived from ventricular but not atrial cardiomyocytes of animal models despite higher prevalence of atrial arrhythmia (e.g., atrial fibrillation). Due to significant ultrastructural and functional differences, a simple transfer of ventricular proneness toward arrhythmia to atrial arrhythmia is critical. The use of murine models in arrhythmia research is widespread, despite known translational limitations. We here directly compare atrial and ventricular mechanisms of arrhythmia to identify critical differences that should be considered in murine models for development of antiarrhythmic strategies for atrial arrhythmia.

Methods and Results: Isolated murine atrial and ventricular myocytes were analyzed by wide field microscopy and subjected to a proarrhythmic protocol during patch-clamp experiments. As expected, the spindle shaped atrial myocytes showed decreased cell area and membrane capacitance compared to the rectangular shaped ventricular myocytes. Though delayed afterdepolarizations (DADs) could be evoked in a similar fraction of both cell types (80% of cells each), these led significantly more often to the occurrence of spontaneous action potentials (sAPs) in ventricular myocytes. Interestingly, numerous early afterdepolarizations (EADs) were observed in the majority of ventricular myocytes, but there was no EAD in any atrial myocyte (EADs per cell; atrial myocytes: 0 ± 0; n = 25/12 animals; ventricular myocytes: 1.5 [0–43]; n = 20/12 animals; p < 0.05). At the same time, the action potential duration to 90% decay (APD₉₀) was unaltered and the APD₅₀ even increased in atrial versus ventricular myocytes. However, the depolarizing L-type Ca²⁺ current (I_Ca) and Na⁺/Ca²⁺-exchanger inward current (I_NCX) were significantly smaller in atrial versus ventricular myocytes.

Conclusion: In mice, atrial myocytes exhibit a substantially distinct occurrence of proarrhythmic afterdepolarizations compared to ventricular myocytes, since they are in a similar manner susceptible to DADs but interestingly seem to be protected against EADs and show less sAPs. Key factors in the generation of EADs like I_Ca and I_NCX were significantly reduced in atrial versus ventricular myocytes, which may offer a mechanistic explanation for the observed protection against EADs. These findings may be of relevance for current studies on atrial level in murine models to develop targeted strategies for the treatment of atrial arrhythmia.

Overexpression of the Na+ /Ca2+ exchanger influences ouabain-mediated spontaneous Ca2+ activity but not positive inotropy

Administration of digitalis in heart failure (HF) increases quality of life but does not carry a prognostic benefit. Digitalis is an indirect inhibitor of the Na⁺ /Ca²⁺ exchanger (NCX), which is overexpressed in HF. We therefore used the cardiac glycoside ouabain in Ca²⁺ imaging experiments and patch-clamp experiments in isolated ventricular myocytes from nonfailing transgenic NCX overexpressor mice (OE). In field-stimulated myocytes, ouabain (1-100 μm) increased the amplitude of the Ca²⁺ transient in OE and wild-type (WT) similarly. Ouabain-mediated spontaneous Ca²⁺ -activity was significantly more pronounced in OE compared to WT myocytes at higher concentrations (100 μm). Also, at very high concentrations (1000 μm) of ouabain, the number of cells with hypercontraction leading to cell death was higher in OE. Ouabain (10 μm) shortened the action potential duration in both genotypes. Our findings suggest that the proarrhythmic but not the inotropic effects of cardiac glycosides are enhanced by increased NCX expression. This may offer an explanation for the observed lack of prognostic benefit but increased quality of life in HF, which is accompanied by NCX upregulation.

Severe Proarrhythmic Potential of the Antiemetic Agents Ondansetron and Domperidone

The potential of ondansetron and domperidone, both clinically established antiemetic agents, to increase the QT-interval has been described in several case reports. Therefore, the aim of the present study was to investigate whether these drugs may provoke polymorphic ventricular tachycardia in a sensitive experimental model of drug-induced proarrhythmia. In 10 female rabbits, ondansetron (1, 5 and 10 µM, n = 10) or domperidone (0.5, 1 and 2 µM, n = 8) was infused after obtaining baseline data. Eight endo- and epicardial monophasic action potentials and a simultaneously recorded 12-lead ECG reproduced the clinically observed QT-prolongation (ondansetron: 1 µM:+17 ms, 5 µM:+41 ms, 10 µM:+78 ms, p < 0.01; domperidone: 0.5 µM:+57 ms, 1 µM:+79 ms, 2 µM:+99 ms, p < 0.01). This was accompanied by a significant increase in action potential duration at 90% of repolarization. Administration of both agents also increased dispersion of repolarization (ondansetron: 1 µM:+12 ms, 5 µM:+17 ms; 10 µM:+18 ms, p < 0.05; domperidone: 0.5 µM:+19 ms, 1 µM:+27 ms; 2 µM:+23 ms p < 0.05). Lowering of potassium concentration in bradycardic AV-blocked hearts provoked early afterdepolarizations (EADs) in 9 of 10 ondansetron-treated hearts and induced polymorphic ventricular tachycardia (VT) resembling torsade de pointes in 7 of 10 ondansetron-treated hearts (86 episodes). Under the influence of domperidone, EAD and polymorphic VT occurred in 7 of 8 hearts (131 episodes). In the present study, both ondansetron and domperidone demonstrated a severe proarrhythmic potential. A significant prolongation of cardiac repolarization as well as a marked increase in spatial dispersion of repolarization represents the underlying electrophysiologic mechanisms. These results imply that application of ondansetron should be handled carefully. For regular administration, ECG monitoring should be mandatory.

Ranolazine Prevents Levosimendan-Induced Atrial Fibrillation

OBJECTIVES

Levosimendan is a calcium sensitizer that is used as positive inotropic drug in acute decompensated heart failure. An increased incidence of atrial fibrillation after levosimendan-treatment was observed in clinical and experimental studies. Due to the limited range of antiarrhythmic drugs, the aim of the present study was to assess potential antiarrhythmic effects of ranolazine in levosimendan-pretreated isolated rabbit hearts.

METHODS

Twelve rabbit hearts were excised and retrogradely perfused employing the Langendorff setup. Left and right atrial catheters were used to record monophasic action potentials and to obtain cycle length-dependent atrial action potential durations (aAPD90) and effective refractory periods (aERP). After obtaining baseline data, 0.5 µmol/L levosimendan was infused. Subsequently, 10 µmol/L ranolazine was administered.

RESULTS

Infusion of levosimendan led to a reduction of aAPD90 (-9 ms, p < 0.05) and aERP (-13 ms, p < 0.05). Additional treatment with ranolazine prolonged aAPD90 (+23 ms, p < 0.01) and aERP (+30 ms, p < 0.05). Under baseline conditions, a predefined pacing protocol induced 77 episodes of atrial fibrillation. Infusion of levosimendan enhanced the vulnerability to atrial fibrillation (132 episodes, p = 0.14). Further treatment with ranolazine had a significant antiarrhythmic effect (61 episodes, p < 0.05).

CONCLUSIONS

In this study, ranolazine seems to prevent atrial fibrillation in levosimendan-pretreated hearts. Underlying mechanism is a prolongation of atrial repolarization and aERP.

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.

Antiarrhythmic effect of vernakalant in an experimental model of Long-QT-syndrome

Aims

The antiarrhythmic drug vernakalant exerts antiarrhythmic effects in atrial fibrillation. Recent experimental data suggest interactions with the late sodium current and antiarrhythmic effects in ventricular arrhythmias. We aimed at investigating whether treatment with vernakalant reduces polymorphic ventricular tachycardia (VT) in an experimental model of Long-QT-syndrome (LQTS).

Methods and results

Twenty-nine isolated rabbit hearts were assigned to two groups and treated with erythromycin (300 µM, n = 15) or veratridine (0.5 µM, n = 14) after obtaining baseline data. Thereafter, vernakalant (10 µM) was additionally infused. Infusion of erythromycin or veratridine significantly increased action potential duration (APD90) and QT interval. Erythromycin and veratridine also significantly augmented spatial dispersion of repolarization (erythromycin: +43 ms; veratridine: +55 ms, P < 0.01, respectively) and temporal dispersion of repolarization. After lowering extracellular [K+] in bradycardic hearts, 11 of 15 erythromycin-treated hearts and 4 of 14 veratridine-treated hearts showed early afterdepolarizations and subsequent polymorphic VT. Additional treatment with vernakalant resulted in a significant reduction of spatial dispersion of spatial dispersion in both groups (erythromycin: -32 ms; veratridine: -35 ms, P < 0.05 each) and a stabilization of temporal dispersion. After additional treatment with vernakalant, only 5 of 15 erythromycin-treated hearts (P = 0.07) and 1 of 14 veratridine-treated hearts (P = 0.32) presented polymorphic VT.

Conclusion

Vernakalant has antiarrhythmic effects in this experimental model of acquired LQTS. A reduction of spatial dispersion of repolarization and a stabilization of temporal dispersion in hearts showing polymorphic VT represent the major underlying electrophysiological mechanisms.

Ryanodine-receptor inhibition by dantrolene effectively suppresses ventricular arrhythmias in an ex vivo model of long-QT syndrome

AIMS

A significant antiarrhythmic potential of ryanodine receptor inhibition was reported in experimental studies. The aim of the present study was to assess potential antiarrhythmic effects of dantrolene in an experimental whole-heart model of drug-induced long-QT syndrome (LQTS).

METHODS

In 12 isolated rabbit hearts, long-QT-2-syndrome was simulated by infusion of erythromycin (300 μM). Twelve rabbit hearts were treated with veratridine (0.5 μM) to mimic long-QT-3-syndrome.

RESULTS

Monophasic action potentials and ECG showed a significant prolongation of QT-interval (+71 ms, P < 0.01) and action potential duration (APD, +43 ms, P < 0.01) after infusion of erythromycin as compared with baseline. Similar results were obtained in veratridine-treated hearts (QT-interval: +43 ms, P < 0.01; APD: +36 ms, P < 0.01). Both erythromycin (+36 ms, P < 0.05) and veratridine (+38 ms) significantly increased dispersion of repolarization. Additional infusion of dantrolene (20 μM) did not significantly alter QT-interval and APD but resulted in a significant reduction of dispersion of repolarization (erythromycin group: -33 ms, P < 0.05; veratridine group: -29 ms, P < 0.05). Lowering of potassium concentration resulted in the occurrence of early afterdepolarizations (EAD) and polymorphic ventricular tachycardia (VT) in 9 of 12 erythromycin-treated hearts (175 episodes) and 8 of 12 veratridine-treated hearts (66 episodes). Additional infusion of dantrolene significantly reduced occurrence of polymorphic VT and resulted in occurrence of EAD and polymorphic VT in 1 of 12 erythromycin-treated hearts (18 episodes) and 1 of 12 veratridine-treated hearts (3 episodes).

CONCLUSION

Inhibition of the ryanodine receptor by dantrolene significantly reduced occurrence of polymorphic VT in drug-induced LQTS. A significant reduction of spatial dispersion of repolarization represents a major antiarrhythmic mechanism. These results imply that dantrolene may represent a promising antiarrhythmic option in drug-induced LQTS.

The Effects of SEA0400 on Ca2+ Transient Amplitude and Proarrhythmia Depend on the Na+/Ca2+ Exchanger Expression Level in Murine Models

Background/Objective: The cardiac Na⁺/Ca²⁺ exchanger (NCX) has been identified as a promising target to counter arrhythmia in previous studies investigating the benefit of NCX inhibition. However, the consequences of NCX inhibition have not been investigated in the setting of altered NCX expression and function, which is essential, since major cardiac diseases (heart failure/atrial fibrillation) exhibit NCX upregulation. Thus, we here investigated the effects of the NCX inhibitor SEA0400 on the Ca²⁺ transient amplitude and on proarrhythmia in homozygous NCX overexpressor (OE) and heterozygous NCX knockout (hetKO) mice compared to corresponding wild-types (WT_OE/WT_hetKO). Methods/Results: Ca²⁺ transients of field-stimulated isolated ventricular cardiomyocytes were recorded with fluo-4-AM or indo-1-AM. SEA0400 (1 μM) significantly reduced NCX forward mode function in all mouse lines. SEA0400 (1 μM) significantly increased the amplitude of field-stimulated Ca²⁺ transients in WT_OE, WT_hetKO, and hetKO, but not in OE (% of basal; OE = 98.7 ± 5.0; WT_OE = 137.8 ± 5.2^*; WT_hetKO = 126.3 ± 6.0^*; hetKO = 140.6 ± 12.8^*; ^*p < 0.05 vs. basal). SEA0400 (1 μM) significantly reduced the number of proarrhythmic spontaneous Ca²⁺ transients (sCR) in OE, but increased it in WT_OE, WT_hetKO and hetKO (sCR per cell; basal/+SEA0400; OE = 12.5/3.7; WT_OE = 0.2/2.4; WT_hetKO = 1.3/8.8; hetKO = 0.2/5.5) and induced Ca²⁺ overload with subsequent cell death in hetKO. Conclusion: The effects of SEA0400 on Ca²⁺ transient amplitude and the occurrence of spontaneous Ca²⁺ transients as a proxy measure for inotropy and cellular proarrhythmia depend on the NCX expression level. The antiarrhythmic effect of SEA0400 in conditions of increased NCX expression promotes the therapeutic concept of NCX inhibition in heart failure/atrial fibrillation. Conversely, in conditions of reduced NCX expression, SEA0400 suppressed the NCX function below a critical level leading to adverse Ca²⁺ accumulation as reflected by an increase in Ca²⁺ transient amplitude, proarrhythmia and cell death. Thus, the remaining NCX function under inhibition may be a critical factor determining the inotropic and antiarrhythmic efficacy of SEA0400.

Ivabradine Reduces Digitalis-induced Ventricular Arrhythmias

The I_(f) channel inhibitor ivabradine is recommended for treatment of heart failure but also affects potassium currents and thereby prolongs ventricular repolarization. The aim of this study was to examine the electrophysiological effects of ivabradine on digitalis-induced ventricular arrhythmias. Thirteen rabbit hearts were isolated and Langendorff-perfused. After obtaining baseline data, the digitalis glycoside ouabain was infused (0.2 μM). Monophasic action potentials and ECG showed a significant abbreviation of QT interval (-34 ms, p < 0.05) and action potential duration (APD₉₀ ; -27 ms, p < 0.05). The shortening of ventricular repolarization was accompanied by a reduction in effective refractory period (ERP; -27 ms, p < 0.05). Thereafter, hearts were additionally treated with ivabradine (5 μM). Of note, this did not exert significant effects on QT interval (-4 ms, p = ns) or APD₉₀ (-15 ms, p = ns) but resulted in an increase in ERP (+17 ms, p < 0.05). This led to a significant increase in post-repolarization refractoriness (PRR, +32 ms, p < 0.01) as compared with sole ouabain treatment. Under baseline conditions, ventricular fibrillation (VF) was inducible by a standardized pacing protocol including programmed stimulation and burst stimulation in four of 13 hearts (31%; 15 episodes). After application of 0.2 μM ouabain, eight of 13 hearts were inducible (62%, 49 episodes). Additional infusion of 5 μM ivabradine led to a significant suppression of VF. Only four episodes could be induced in two of 13 hearts (15%). In this study, ivabradine reduced digitalis-induced ventricular arrhythmias. Ivabradine did not affect ventricular repolarization in the presence of digitalis treatment but demonstrated potent anti-arrhythmic properties based on an increase in both ERP and PRR. The study further characterizes the beneficial electrophysiological profile of ivabradine.

Effective suppression of atrial fibrillation by the antihistaminic agent antazoline: First experimental insights into a novel antiarrhythmic agent

INTRODUCTION

The antihistaminic antazoline (ANT) was reported to be highly effective and safe for rapid conversion of atrial fibrillation (AF). We therefore analyzed underlying mechanisms in an experimental whole-heart model.

METHODS AND RESULTS

Isolated and retrogradely perfused rabbit hearts underwent a standardized protocol employing atrial burst pacing-induced AF in five of 20 hearts under baseline conditions (seven episodes). Thereafter, a combination of acetylcholine and isoproterenol was employed to enhance AF occurrence. Two monophasic action potential recordings on the left- and two on the right atrial epicardium showed a decrease in atrial action potential duration (aAPD, -25 msec, P<.05) and atrial effective refractory period (aERP; -52 msec, P<.01) after infusion of acetylcholine (1 μmol/L) and isoproterenol (1 μmol/L). This led to induction of AF in 14 of 20 hearts (145 episodes). Simultaneous infusion of ANT (20 μmol/L) led to a complete suppression of AF in all inducible hearts. Treatment with ANT also led to a significant increase in aAPD (+41 msec, P<.01) and aERP (+74 msec, P<.05), leading to a marked increase in atrial postrepolarization refractoriness (aPRR, +33 msec, P<.01). Results were compared to 13 rabbits treated with flecainide. Flecainide induced a significant increase in aPRR and resulted in induction of AF in seven of 13 hearts (51 episodes) while 11 of 13 hearts were inducible with acetylcholine and isoproterenol (93 episodes).

CONCLUSION

Administration of ANT was highly effective in suppressing AF. The antiarrhythmic effect could be explained by a significant increase in postrepolarization refractoriness as a result of a more marked increase in aERP as compared with aAPD.

The Use of the Ambulatory Arterial Stiffness Index in Patients Suspected of Secondary Hypertension

The ambulatory arterial stiffness index (AASI) is a marker of arterial stiffness and is derived from ambulatory 24-h blood pressure registration. We studied whether the AASI could be used as a predictive factor for the presence of renal artery stenosis (RAS) in patients with a suspicion of secondary hypertension and as such as a diagnostic tool for RAS. We included 169 patients with difficult-to-treat hypertension. They all underwent 24-h ambulatory blood pressure monitoring registration, imaging of the renal arteries, and cardiovascular risk measurement, including smoking, history, biometrics, blood pressure, renal function, lipids, and glucose metabolism. Performing univariate and multivariate analyses, we investigated if AASI and the other cardiovascular risk factors were related to the presence of RAS. Of the 169 patients (49% women), 31% had RAS. The mean AASI was 0.44 (0.16). The presence of RAS showed no significant correlation with AASI (r = 0.14, P = 0.06). Age (r = 0.19, P = 0.01), hypercholesterolemia (r = 0.26, P = 0.001), history of CVD (r = 0.22, P = 0.004), and creatinine clearance (r = -0.34, P < 0.001) all demonstrated a correlation with RAS. Although AASI is higher in patients with RAS, AASI does not independently predict the presence of RAS in hypertensive subjects.

Low proarrhythmic potential of citalopram and escitalopram in contrast to haloperidol in an experimental whole-heart model

In several case reports proarrhythmic effects of citalopram and escitalopram have been reported. Systematic analyses on prorarrhythmic effects of these drugs are not yet available. The aim of the present study was to investigate if application of citalopram, escitalopram or haloperidol provokes polymorphic ventricular tachycardia in a sensitive model of proarrhythmia. In isolated rabbit hearts monophasic action potentials and ECG showed a significant QT-prolongation after application of citalopram (2µM: +47ms, 4µM: +56ms, P<0.05) accompanied by an increase of action potential duration (APD) but not dispersion of repolarization. Reduced potassium concentration in bradycardic AV-blocked hearts provoked early afterdepolarizations (EAD) in 2 of 12 hearts but no polymorphic ventricular tachycardia (pVT). Application of escitalopram also increased QT-interval (2µM: +3ms, 4µM: +30ms, P<0.05) and APD without effects on dispersion. 3 of 10 hearts showed EAD and pVT in 2 of 10 hearts (32 episodes). The results were compared to 12 rabbits treated with haloperidol which led to an increase in QT-interval (1µM:+62ms; 2µM:+96ms; P<0.01), APD and dispersion (1µM:+15ms, 2µM:+40ms; P<0.01) and induced EAD in all 12 and pVT in 10 of 12 hearts (152 episodes). Citalopram and escitalopram demonstrated a rather safe electrophysiologic profile despite significant QT prolongation. In contrast, haloperidol led to significant increase of dispersion of repolarization while this parameter remained stable under the influence of citalopram or escitalopram. These results imply that application of citalopram or escitalopram is not as proarrhythmic as some case reports might suggest while haloperidol is torsadogenic.

Slow pathway modification in patients presenting with only two consecutive AV nodal echo beats

BACKGROUND

Slow pathway modification (SPM) is the therapy of choice for AV-nodal reentry tachycardia (AVNRT). When AVNRT is not inducible, empirical ablation can be considered, however, the outcome in patients with two AV nodal echo beats (AVNEBs) is unknown.

METHODS

Out of a population of 3003 patients who underwent slow pathway modification at our institution between 1993 and 2013, we retrospectively included 32 patients with a history of symptomatic tachycardia, lack of paroxysmal supraventricular tachycardia (pSVT) inducibility but occurrence of two AVNEBs.

RESULTS

pSVT documentation by electrocardiography (ECG) was present in 20 patients. The procedural endpoint was inducibility of less than two AVNEBs. This was reached in 31 (97%) patients. Long-term success was assessed by a telephone questionnaire (follow-up time 63±9 months). A total 94% of the patients benefited from the procedure (59% freedom from symptoms; 34% improvement in symptoms). Among those patients in whom ECG documentation was not present, 100% benefited (58% freedom from symptoms, 42% improvement).

CONCLUSION

This is the first collective analysis of a group of patients presenting with symptoms of pSVT and inducibility of only two AVNEBs. Procedural success and clinical long-term follow-up were in the range of the reported success rates of slow pathway modification of inducible AVNRT, independent of whether ECG documentation was present. Thus, SPM is a safe and effective therapy in patients with two AVNEBs.

Intraoperative Defibrillation Testing of Subcutaneous Implantable Cardioverter-Defibrillator Systems-A Simple Issue?

Background

The results of the recently published randomized SIMPLE trial question the role of routine intraoperative defibrillation testing. However, testing is still recommended during implantation of the entirely subcutaneous implantable cardioverter‐defibrillator (S‐ICD) system. To address the question of whether defibrillation testing in S‐ICD systems is still necessary, we analyzed the data of a large, standard‐of‐care prospective single‐center S‐ICD registry.

Methods and Results

In the present study, 102 consecutive patients received an S‐ICD for primary (n=50) or secondary prevention (n=52). Defibrillation testing was performed in all except 4 patients. In 74 (75%; 95% CI 0.66–0.83) of 98 patients, ventricular fibrillation was effectively terminated by the first programmed internal shock. In 24 (25%; 95% CI 0.22–0.44) of 98 patients, the first internal shock was ineffective and further internal or external shock deliveries were required. In these patients, programming to reversed shock polarity (n=14) or repositioning of the sensing lead (n=1) or the pulse generator (n=5) led to successful defibrillation. In 4 patients, a safety margin of <10 J was not attained. Nevertheless, in these 4 patients, ventricular arrhythmias were effectively terminated with an internal 80‐J shock.

Conclusions

Although it has been shown that defibrillation testing is not necessary in transvenous ICD systems, it seems particular important for S‐ICD systems, because in nearly 25% of the cases the primary intraoperative test was not successful. In most cases, a successful defibrillation could be achieved by changing shock polarity or by optimizing the shock vector caused by the pulse generator or lead repositioning.

Suppression of Early and Late Afterdepolarizations by Heterozygous Knockout of the Na+/Ca2+ Exchanger in a Murine Model

BACKGROUND

The Na(+)/Ca(2+) exchanger (NCX) has been implied to cause arrhythmias. To date, information on the role of NCX in arrhythmogenesis derived from models with increased NCX expression, hypertrophy, and heart failure. Furthermore, the exact mechanism by which NCX exerts its potentially proarrhythmic effect, ie, by promoting early afterdepolarization (EAD) or delayed afterdepolarization (DAD) or both, is unknown.

METHODS AND RESULTS

We investigated isolated cardiomyocytes from a murine model with heterozygous knockout of NCX (hetKO) using the patch clamp and Ca(2+) imaging techniques. Action potential duration was shorter in hetKO with IKtot not being increased. The rate of spontaneous Ca(2+) release events and the rate of DADs were unaltered; however, DADs had lower amplitude in hetKO. A DAD triggered a spontaneous action potential significantly less often in hetKO when compared with wild-type. The occurrence of EADs was also drastically reduced in hetKO. ICa activity was reduced in hetKO, an effect that was abolished in the presence of the Ca(2+) buffer BAPTA.

CONCLUSIONS

Genetic suppression of NCX reduces both EADs and DADs. The following molecular mechanisms apply: (1) Although the absolute number of DADs is unaffected, an impaired translation of DADs into spontaneous action potentials results from a reduced DAD amplitude. (2) EADs are reduced in absolute number of occurrence, which is presumably a consequence of shortened action potential duration because of reduced NCX activity but also reduced ICa the latter possibly being caused by a direct modulation of Ca(2+)-dependent ICa inhibition by reduced NCX activity. This is the first study to demonstrate that genetic inhibition of NCX protects against afterdepolarizations and to investigate the underlying mechanisms.