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Background. Wearable cardioverter-defibrillators (WCD, LifeVest, ZOLL) can protect from sudden cardiac death bridging a vulnerable period until a decision on implantable cardioverter-defibrillator (ICD) implantation can be reached. WCD is commonly used for 3 months or less. It is unknown, which patients use WCD longer and which patients are most likely to benefit from it. Hypothesis. Extended use of WCD is reasonable in selected cases based on underlying heart disease and overall patient risk profile. Methods. We conducted a systematic and comprehensive research of all published clinical studies on PubMed reporting on the use of the WCD. Only original articles reporting on wear times and time to appropriate shocks were included in our analysis. Results. The search resulted in 127 publications. 14 parameters were reported necessary for inclusion in our analysis. Median wear times ranged from 16 to 394 days. The median wear time was especially long for patients suffering from nonischemic cardiomyopathy (NICM) (range: 50–71 days) and specifically peripartum cardiomyopathy (PPCM) (120 days) and for heart transplant candidates. There was a large variation of appropriate shocks according to indication for WCD use. In contrast to NICM in general, the number of appropriate shocks was particularly high in patients with PPCM (0 in 254 patients and 5 in 49 patients, respectively). The median and maximal time periods to the first appropriate shock were longest in patients with PPCM (median time to the first appropriate shock: 68 days). Conclusions. Prolonged use of WCD is not uncommon in available literature. Patients suffering from NICM and specifically PPCM seem most likely to have longer therapy duration with WCD with success. Careful patient selection for prolonged use may decrease the need for ICD implantation in the future; however, prospective data are needed to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

The wearable cardioverter-defibrillator has been available for over a decade and now is frequently prescribed for patients deemed at high arrhythmic risk in whom the underlying pathology is potentially reversible or who are awaiting an implantable cardioverter-defibrillator. The use of the wearable cardioverter-defibrillator is included in the new 2015 ESC guidelines for the management of ventricular arrhythmias and prevention of sudden cardiac death. The present review provides insight into the current technology and an overview of this approach. [ABSTRACT FROM AUTHOR]

REEK, S., et al.: Noncontact Mapping of Ventricular Tachycardia in a Closed-Chest Animal Model of Chronic Myocardial Infarction. Treatment of ventricular tachyarrhythmias in the setting of chronic myocardial infarction requires accurate characterization of the arrhythmia substrate. New mapping technologies have been developed that facilitate identification and ablation of critical areas even in rapid, hemodynamically unstable ventricular tachycardia. A noncontact mapping system was used to analyze induced ventricular tachycardia in a closed-chest sheep model of chronic myocardial infarction. Twelve sheep were studied 96 ± 10 days after experimental myocardial infarction. During programmed stimulation, 15 different ventricular tachycardias were induced in nine animals. Induced ventricular tachycardia had a mean cycle length of 190 ± 30 ms. In 12 ventricular tachycardias, earliest endocardial activity was recorded from virtual electrodes, preceding the surface QRS onset by 30 ± 7 ms. Noncontact mapping identified diastolic activity in ten ventricular tachycardias. Diastolic potentials were recorded over a variable zone, spanning more than 30 mm. Timing of diastolic potentials varied from early to late diastole and could be traced back to the endocardial exit site. Entrainment with overdrive pacing was attempted in nine ventricular tachycardias, with concealed entrainment observed in seven. Abnormal endocardium in the area of chronic myocardial infarction identified by unipolar peak voltage mapping was confirmed by magnetic resonance imaging. These data suggest that induced ventricular tachycardia in the late phase of myocardial infarction in the sheep model is due to macroreentry involving the infarct borderzone. The combination of this animal model with noncontact mapping technology will allow testing of new strategies to cure and prevent ventricular tachycardia in the setting of chronic myocardial infarction. (PACE 2003; 26:2253–2263) [ABSTRACT FROM AUTHOR]

The Wearable Cardioverter Defibrillator (WCD) automatically detects and treats ventricular tachyarrhythmias without the need for assistance from a bystander, while at the same time allowing the patient to ambulate freely. It represents an alternative to emergency medical services for outpatient populations with a temporary risk of sudden cardiac death. While the original devices used a monophasic truncated exponential waveform for cardioversion/defibrillation shocks, a new, biphasic shock was developed for the next device generation. In 12 patients undergoing electrophysiological testing for ventricular tachyarrhythmias, termination of electrically induced ventricular fibrillation (VF) was attempted via the WCD. In 22 episodes, induced VF was promptly terminated by the first 70 J (n = 12) or 100 J (n = 10) biphasic shocks. Time between arrhythmia initiation and shock delivery was 22 ± 6 seconds (70 J) and 21 ± 6 seconds (100 J) (P = NS). The measured transthoracic impedance was 71 ± 5 Ω (64–79 Ω) for the 70 J shock and 64 ± 8 Ω (47–72 Ω) for the 100 J shock. The present study demonstrates that a single low energy biphasic shock delivered by the WCD, reliably terminates electrically induced VF (100% of episodes). The results of this study suggest that there is an acceptable safety margin to the maximum output of the device (150 J). Despite our promising data, we recommend that programming all shocks for maximum energy output should be done when using the WCD in ambulatory patients. (PACE 2003; 26:2016–2022) [ABSTRACT FROM AUTHOR]

: ObjectivesWe sought to evaluate the efficacy and safety of pulmonary vein (PV) isolation using transvenous cryoablation for the treatment of atrial fibrillation (AF).: BackgroundAlthough electrical isolation of PVs with radiofrequency energy for the treatment of AF is feasible, it is associated with a significant risk of PV stenosis. Cryoablation is a new alternative therapy allowing ablation of tissue while preserving its underlying architecture.: MethodsIn 52 patients with paroxysmal (n = 45) or persistent (n = 7) AF, PV isolation using the CryoCor cryoablation system (CyroCor Inc., San Diego, California) with a 10F deflectable transvenous catheter was performed as guided by ostial PV potentials. Cryoablation was applied twice at each targeted site (2.5 to 5 min/application). Computed tomography (CT) of the thorax was performed at baseline and at 3 and 12 months to evaluate for PV stenosis.: ResultsAll targeted PVs were completely isolated in 49 (94%) of 52 of patients. Of 152 PVs targeted, 147 (97%) were successfully isolated (mean 3.0 PVs isolated per patient). After a mean period of 12.4 ± 5.5 months of follow-up, 37 (71%) of 52 patients had no recurrence of AF or were clinically improved, including 29 patients (56%) who had no recurrence of AF with (n = 11) or without the use of anti-arrhythmic drugs. At 3 and 12 months, the CT scan showed no evidence of PV stenosis associated with cryoablation in any patients.: ConclusionsTransvenous catheter cryoablation is an effective method to create PV electrical isolation for the treatment of AF. A clinically satisfactory result can be achieved in 71% of patients with AF, without the risk of PV stenosis. [Copyright &y& Elsevier]

RINALDI, C.A., et al. : A Randomized Prospective Study of Single Coil Versus Dual Coil Defibrillation in Patients with Ventricular Arrhythmias Undergoing Implantable Cardioverter Defibrillator Therapy. --> ICD implantation is standard therapy for malignant ventricular arrhythmias. The advantage of dual and single coil defibrillator leads in the successful conversion of arrhythmias is unclear. This study compared the effectiveness of dual versus single coil defibrillation leads. The study was a prospective, multicenter, randomized study comparing a dual with a single coil defibrillation system as part of an ICD using an active pectoral electrode. Seventy‐six patients (64 men, 12 women; age61 ± 11 years) were implanted with a dual (group 1, n = 38) or single coil lead system (group 2,n = 38). The patients represented a typical ICD cohort: 60% presented with ischemic cardiomyopathy as their primary cardiac disease, the mean left ventricular ejection fraction was0.406 ± 0.158. The primary tachyarrhythmia was monomorphic ventricular tachyarrhythmia in 52.6% patients and ventricular fibrillation in 38.4%. There was no significant difference in terms of P and R wave amplitudes, pacing thresholds, and lead impedance at implantation and follow‐up in the two groups. There was similarly no difference in terms of defibrillation thresholds (DFT) at implantation. Patients in group 1 had an average DFT of10.2 ± 5.2 Jcompared to10.3 ± 4.1 Jin Group 2, P = NS. This study demonstrates no significant advantage of a dual coil lead system over a single coil system in terms of lead values and defibrillation thresholds. This may have important bearing on the choice of lead systems when implanting ICDs. (PACE 2003; 26:1684–1690) [ABSTRACT FROM AUTHOR]

Objectives To evaluate the long-term outcome with an implantable atrial defibrillator (IAD) in patients with recurrent atrial fibrillation (AF).Background Maintenance of sinus rhythm using repeated internal cardioversion shocks has been shown to be effective and safe in short-term studies but long term follow-up is unknown.Methods Since 1995, 136 patients (30 women) with symptomatic, drug-refractory atrial fibrillation were implanted with an IAD (METRIX, InControl). This analysis was performed after a median of 40 (range 7–66) months after implantation.Results In 26 patients, the programmed mode was not documented during last follow-up, four patients had died. Of the remaining 106 patients (mean age 58±10, range 34 – 79 years), 39 were actively delivering therapy with the device, in 14 patients the device was used to monitor the arrhythmia but no shocks were delivered, and in 53 patients it was turned off or explanted. Increases in defibrillation thresholds (n=7), patient intolerance of multiple cardioversion shocks (n=15), and significant bradycardia requiring dual-chamber pacing (n=12) were the main reasons for discontinuation of therapy in addition to battery depletion (n=19). After explantation, efforts to maintain sinus rhythm were continued in 17 patients whereas rate control was attempted in 36 patients.Conclusions A strategy of maintaining sinus rhythm long-term with an IAD is feasible in a proportion of patients. However, patient selection is critical, and technical improvements (i.e. higher shock energies, dual-chamber pacing and additional preventive and anti-tachycardia pacing algorithms) are required to increase the number of patients having long term benefit, and frequent arrhythmia recurrences and patient intolerance to repeated cardioversion shocks remain a major limitation. [ABSTRACT FROM PUBLISHER]

Introduction: Radiofrequency (RF) catheter ablation currently is used for treatment of cardiac arrhythmias. Although the success rate is high for almost all supraventricular tachycardias (SVT), this technique has some drawbacks, especially when pulmonary veins (PV) are targeted for treatment of atrial fibrillation (AF). Additionally, new techniques for isolation of the PVs have the drawback that they can be used only for PV isolation and not for routine treatment of other SVTs. The aim of this study was to report on the safety and efficacy of a new cryoablation system for treatment of all SVTs. Methods and Results: Forty-nine patients with SVT (38 men; age 48 years, range 23-76) were enrolled in the study. Five patients were withdrawn from the study before they underwent cryoablation. The remaining 44 patients were treated with cryoablation (22 AF, 15 atrial flutter, 3 accessory pathway, 2 AV nodal reentrant tachycardia, 1 AV junction ablation for permanent AF, 1 atrial tachycardia). Cryoablation was performed with the CryoCor™ cryoablation system, which uses a precooling system and N2O as a refrigerant. The number of freezes applied varied according to the index arrhythmia treated. Successful isolation of PVs was performed in 20 of (96%) 21 AF patients and 53 of 55 veins. The overall acute success was 98% (43/44). Fifty-three PVs were isolated (2.5/patient). The success rate was 100% (23/23) for right-sided procedures. The average and nadir temperatures reached in right-sided and left-sided procedures were -77°C and -80°C and -75°C and -78°C, respectively. No acute PV stenosis was seen. Conclusion: This novel cryoablation system appears to be safe and can successfully treat different types of SVTs, including AF. Isolation of PVs is possible without producing stenosis. Despite the high blood flow in the right atrial isthmus and PVs, bidirectional conduction block can be achieved. [ABSTRACT FROM AUTHOR]

Previous studies have shown that platelets are activated during atrial fibrillation (AF). However, prophylactic therapy with aspirin is not associated with a reduction of thromboembolic complications in patients with AF. Stimulation of plotelet thrombin and ADP receptors causes a release of P-selectin, which is not affected by aspirin. The purpose of this study was to assess the influence olAF on platelet P-selectin expression. Blood samples from 30 patients were studied ex vivo. Nineteen patients had chronic AF ( > 3 months), 11 patients were in sinus rhythm (SR). P-selectin expression was determined by flow cytometry (antibody binding capacity [BC]) at baseline and after platelet stimulation with adenosine diphosphate (ADP) and thrombin receptor activating peptide (TRAP). To determine the effect of heart rate and atrial pressure (RAP), measurements were repeated after 10 minutes of ventricular pacing (120 beats/min) in patients with SR. P-selectin expression was increased in patients with AF at baseline (AF: 1329 ± 81 BC vs SR: 968 ± 108 BC; P < 0.05) and after stimulation with ADP (AF: 1445 ± 101 BC vs SR: 1061 ± 109 BC; P < 0.05] and TRAP (AF: 13783 ± 2442 BC vs SR: 5977 ± 800 BC; P < 0.05). RAP (2.0 ± 0.5 vs 6.0 -± 0.8 mmHg; p < 0.01) and atrial rate (75 ± 5 vs 114 ± 5 beats/min; P < 0.001) increased during ventricular pacing. However, P-selectin levels remained stable. AF was accompanied by increased P-selectin expression. In contrast, increased ventricular rate and elevated atrial pressure alone had no effect on platelet ac- tivity. Further studies are needed to determine if platelet ADP receptor inhibitors offer a therapeutic benefit in patients with AF. [ABSTRACT FROM AUTHOR]

Dual AV node physiology often persists after successful slow pathway (SP) ablation, and the mechanism of tachycardia elimination is unresolved. Therefore, AV node conduction curves were analyzed following successful ablation (4 ± 1 energy applications) in 85 consecutive patients (58 women, age 50 ± 2 years) with typical AVNRT. Twenty-seven patients (32%) had complete elimination (group 1) whereas 58 (68%) patients had persistence (group 2) of dual AV node physiology. A significant increase in the AV node Wenckebach cycle length (WB-CL) was observed in both groups (310 ± 9 to 351 ±15 ms in group 1, and 325 ± 8 to 369 ± 9 ms in group 2.P < 0.05). A decrease in the fast pathway (FP) ERP (339 ± 15 to 279 ± 12 ms) and an increase in the maximum FP AH interval (141 ± 5 to 171 ±7) were observed only in group 1 (P < 0.05). In group 2, no change in the SP FRP (267 ± 7 to 280 ± 10 ms) was observed, and the change in the maximum SP-AH following ablation showed a significant inverse relation to the maximum SP-AH at baseline in group 2. In conclusion, (1) an increase in the WB-CL is observed independent of the persistence or elimination of dual physiology after successful ablation; (2) when dual physiology is eliminated, significant changes in the FP ERP and the maximum FP-AH occur; (3) when dual physiology persists, FP physiology and the SP FRP remain unchanged, and a significant inverse relation between the change in the maximum SP-AH following ablation and the maximum baseline SP-AH is observed. [ABSTRACT FROM AUTHOR]

Background: The wearable cardioverter defibrillator (WCD) uses surface electrodes to detect arrhythmia before initiating a treatment sequence. However, it is also prone to inappropriate detection due to artefacts. Objective: The aim of this study is to assess the alarm burden in patients and its impact on clinical outcomes. Methods: Patients from the nationwide Swiss WCD Registry were included. Clinical characteristics and data were obtained from the WCDs. Arrhythmia recordings ≥30 s in length were analysed and categorized as VT/VF, atrial fibrillation (AF), supraventricular tachycardia (SVT) or artefact. Results: A total of 10653 device alarms were documented in 324 of 456 patients (71.1%) over a mean WCD wear-time of 2.0 ± 1.6 months. Episode duration was 30 s or more in 2996 alarms (28.2%). One hundred and eleven (3.7%) were VT/VF episodes. The remaining recordings were inappropriate detections (2736 (91%) due to artefacts; 117 (3.7%) AF; 48 (1.6%) SVT). Two-hundred and seven patients (45%) had three or more alarms per month. Obesity was significantly associated with three or more alarms per month (p = 0.01, 27.7% vs. 15.9%). High alarm burden was not associated with a lower average daily wear time (20.8 h vs. 20.7 h, p = 0.785) or a decreased implantable cardioverter defibrillator implantation rate after stopping WCD use (48% vs. 47.3%, p = 0.156). Conclusions: In patients using WCDs, alarms emitted by the device and impending inappropriate shocks were frequent and most commonly caused by artefacts. A high alarm burden was associated with obesity but did not lead to a decreased adherence. [ABSTRACT FROM AUTHOR]

The Swiss Ablation Registry provides a national database for electrophysiologic studies and catheter ablations. We analyzed the database to provide an in-depth look at changing trends over the last 20 years. During the study period a total of 78622 catheter ablations (age 61.0 ± 1.2 years; 63.7% male) were performed in 29 centers. The number of ablations increased by approximately ten-fold in 20 years. Ablation for atrial fibrillation (AF) was the main driver behind this increase, with more than hundred-fold (39.7% of all ablations in 2019). Atrioventricular-nodal-reentrant-tachycardia (AVNRT) and accessory pathways, being the main indications for ablation in 2000 (44.1%/25.1%, respectively), made up of only a small proportion (15.2%/3.5%,) respectively in 2019. Fluoroscopy, ablation, and procedure durations were reduced for all ablations over time. The highest repeat ablations were performed for ventricular tachycardia and AF (24.4%/24.3%). The majority of ablations (63.0%) are currently performed in private hospitals and non-university public hospitals whereas university hospitals had dominated (82.4%) at the turn of the century. A pronounced increase in the number of catheter ablations in Switzerland was accompanied by a marked decrease in fluoroscopy, ablation, and procedure durations. We observed a shift toward more complex procedures in older patients with comorbidities. [ABSTRACT FROM AUTHOR]

The two goals of this study were (1) to develop a closed-chest animal model of monomorphic ventricular tachycardia; and (2) to investigate the effect of dual site pacing on inducibility of ventricular tachycardia. In the first part of the study, 10 of 14 sheep underwent successful induction of myocardial infarction by temporary balloon occlusion of the left anterior descending coronary artery. After a follow-up period of 21-43 days, sustained monomorphic ventricular tachycardia could be induced during programmed electrical stimulation using a "clinical" stimulation protocol in 8 of the 10 sheep. The number of ventricular tachycardia episodes per animal varied between 5 and 70. Ventricular fibrillation was never induced during programmed electrical stimulation. Ventricular tachycardia episodes lasted from 30 seconds up to 15 minutes and were terminated by antitachycardia pacing or DC cardioversion. In the second part of the study, the effect of dual site stimulation on ventricular tachycardia inducibility was investigated. High current stimuli from an area within the infarcted zone were given with the Si programmed stimulation protocol. This dual site stimulation showed no effect on ventricular tachycardia induction during programmed electrical stimulation. This animal model shows a high induction rate of sustained monomorphic ventricular tachycardia in the chronic phase of myocardial infarction. The high incidence of ventricular tachycardia inducibility provides a reliable tool to study new techniques for the prevention of ventricular tachyarrhythmias. [ABSTRACT FROM AUTHOR]

Ventricular tachyarrhythmias are the most common cause for sudden cardiac death. The success of catheter ablation for supraventricular tachycardias led to the supposition that ablation could also be used in the treatment of ventricular tachycardias. Despite the promising results in bundle branch reentry and some forms of idiopathic ventricular tachycardia, the success rate in patients with coronary artery disease is still low. There is hope that new approaches to reliably localize the critical region of the tachycardia and new ablation techniques to create larger areas of injury may lead to a wider application of ablation therapy in the treatment of ventricular tachycardia. Survivors of cardiac arrest typically have more rapid and unstable arrhythmias than patients with sustained ventricular tachycardia, and these rapid arrhythmias frequently degenerate into ventricular fibrillation. The instability of the arrhythmia makes it impossible to localize the arrhythmia origin with current mapping techniques. Experimental and clinical data, however, suggest that these arrhythmias also frequently start from a localized area of electrical activation. With developments in mapping techniques and energy delivery, catheter ablation may soon become a feasible therapeutic approach in some patients with unstable arrhythmias. The article discusses the prerequisites for this approach and suggests the patients who may be appropriate candidates for this technique. [ABSTRACT FROM AUTHOR]

The article discusses a case of cardiac arrest with ventricular fibrillation. Preliminary examination involving electrocardiogram telemetry monitoring has shown no relevant irregularities of the heart except the occurrence of polymorphic ventricular tachycardia. The data showed that before the attack there was a gradual movement in the terminal QRS complex and ST segment. The patient recovered after applying implantable cardioverter defibrillator placement.

The findings of our initial study demonstrate for the first time the ability to terminate induced VT/VF reliably (100% of all episodes) by a single, monophasic 230-J shock delivered by the Wearable Cardioverter-Defibrillator (WCD). Although limited by sample size, our data suggest the WCD could be used as a feasible bridge to definitive implantation of an implantable cardioverter-defibrillator in patients in whom risk stratification for sudden death is not completed. [ABSTRACT FROM AUTHOR]