Seasonal influence on sleep apnoea recorded daily by pacemakers.

PURPOSE: Obstructive sleep apnoea (OSA) and cardiac conduction disorders are pathologies with a rising prevalence due to increased life expectancy. Upper airway patency is affected by environmental factors that may be associated with seasonal periods. The ability to record the degree of nocturnal apnoea on a daily basis may provide a more accurate picture of seasonal variability. METHODS: This study used an observational, cross-sectional design recruiting consecutive patients with Sorin/Livanova/Microport® pacemakers. The study assessed the seasonal influence on the daily degree of nocturnal apnoea over a minimum period of 180 days. The respiratory events were recorded using a pacemaker-integrated detection algorithm based on transthoracic impedance variation. A generalised linear repeated measure mixed model was used to study the seasonal effect. RESULTS: A sample of 101 subjects with a mean of 227 valid nights was compiled. Summer was associated with higher RDI (respiratory disturbance index) values and winter with lower values. The mean daily RDI ratio in summer was 1.099 times higher than in winter. CONCLUSIONS: Slight seasonal influences on the degree of nocturnal apnoea were detected through the daily observation of an unselected sample of pacemaker wearers. The degree of apnoea is higher in warmer months and lower in colder months.

Distinct spectral dynamics of implanted cardiac defibrillator signals in spontaneous termination of polymorphic ventricular tachycardia and fibrillation in patients with electrical and structural diseases.

AIMS: To determine the spectral dynamics of early spontaneous polymorphic ventricular tachycardia and ventricular fibrillation (PVT/VF) in humans. METHODS AND RESULTS: Fifty-eight self-terminated and 173 shock-terminated episodes of spontaneously initiated PVT/VF recorded by Medtronic implanted cardiac defibrillators (ICDs) in 87 patients with various cardiac pathologies were analyzed by short fast Fourier transform of shifting segments to determine the dynamics of dominant frequency (DF) and regularity index (RI). The progression in the intensity of DF and RI accumulations further quantified the time course of spectral characteristics of the episodes. Episodes of self-terminated PVT/VF lasted 8.6 s [95% confidence interval (CI): 8.1-9.1] and shock-terminated lasted 13.9 s (13.6-14.3) (P < 0.001). Recordings from patients with primarily electrical pathologies displayed higher DF and RI values than those from patients with primarily structural pathologies (P < 0.05) independently of ventricular function or antiarrhythmic drug therapy. Regardless of the underlying pathology, the average DF and RI intensities were lower in self-terminated than shock-terminated episodes [DF: 3.67 (4.04-4.58) vs. 4.32 (3.46-3.93) Hz, P < 0.001; RI: 0.53 (0.48-0.56) vs. 0.63 (0.60-0.65), P < 0.001]. In a multivariate analysis controlled by the type of pathology and clinical variables, regularity remained an independent predictor of self-termination [hazard ratio: 0.954 (0.928-0.980)]. Receiver operating characteristic (ROC) curve analysis of DF and RI intensities demonstrated increased predictability for self-termination in time with 95% CI above the 0.5 cut-off limit at about t = 8.6 s and t = 6.95 s, respectively. CONCLUSION: Consistent with the notion that fast organized sources maintain PVT/VF in humans, reduction of frequency and regularity correlates with early self-termination. Our findings might help generate ICD methods aiming to reduce inappropriate shock deliveries.

Complete interatrial block in a left-atrial dependent atrioventricular node.

INTRODUCTION: A middle-age woman underwent an electrophysiologic study due to recurrent atypical atrial flutter. METHODS AND RESULT: Radiofrequency ablation of cavotricuspid isthmus and anterior mitral line was performed. During energy delivery on the anterior left atrial wall, interatrial dissociation and complete block of the sinus impulse to the atrioventricular (AV) node was observed. AV node activation became dependent on a subsidiary left atrial rhythm. CONCLUSION: Anatomical location of intra and inter-atrial connections must be taken into account when performing extensive ablation procedures, specially in cases with prior cardiac surgeries.

Wolff Parkinson white pattern in Danon disease: When preexcitation is not what it seems.

Danondisease is a rare genetic disorder with an X-linked dominant inheritance affecting both skeletal and cardiac muscle. Its characteristic cardiac phenotype consists on a severe, non-obstructive and concentric hypertrophic cardiomyopathy (HCM) usually associated with a Wolff-Parkinson-White (WPW) type preexcitation pattern. Whether this corresponds to the presence of an AV or another type of accessory pathways, such as fasciculoventricular pathways (FVP) remains controversial in the literature. However, we describe the case of a teenager with Danon disease and preexcitation who develops a first degree AV block without any change in his QRS morphology, fact that favors the hypothesis of the presence of a FVP. This finding has important clinical implications in the management and prognosis of these complex patients. The absence of an AV accessory pathway decreases their risk of potential SCD in the context of a fast atrial arrhythmia and their chances of having a reentrant AV tachycardia.

Multiple ICD shocks in a patient with dilated cardiomyopathy: What is the mechanism?

We present the case of a 45-year-old male patient with dilated cardiomyopathy who suffers from multiple implantable cardioverter defibrillator (ICD) shocks. The analysis of the ICD tracing and the electrophysiological study allows to conclude that bundle branch re-entrant tachycardia is the most likely diagnosis, even in absence of conduction abnormalities in his basal electrocardiography.

Super-response to cardiac resynchronization therapy may predict late phrenic nerve stimulation.

Aims: Changes in the anatomical relationship between left phrenic nerve and coronary veins may occur due to the reverse remodelling observed in super-responders to cardiac resynchronization therapy (CRT) and might be the underlying mechanism in patients developing late-onset phrenic nerve stimulation (PNS) without evidence of lead dislodgement (LD). In this study, we sought to evaluate the role of super-response (SR) to CRT as a potential predictor of late-onset PNS. Methods and results: Consecutive patients implanted with a left ventricular (LV) lead in a single centre were retrospectively analysed. Phrenic nerve stimulation was classified as 'early' when it occurred within 3 months of implantation and 'late' for occurrences thereafter. 'Late' PNS was considered related to LD (LD-PNS) when LV threshold differed by > 1 V or impedance >250 Ω from baseline values or in case of radiological displacement. Cases not meeting the former criteria were classified as 'non-LD-PNS'. Super-response was defined as a decrease ≥30% of the left ventricluar end-systolic volume at 1-year echocardiography. At 32 ± 7 months follow-up, PNS occurred in 20 of 139 patients. Late non-LD-PNS incidence was significantly higher in the SR group (8/61; 13.1%) when compared with the non-SR (1/78; 1.3%) (P = 0.010). Super-response remained the only predictor of non-LD-PNS at multivariate analysis (odds ratio: 11.62, 95% confidence interval 1.41-95.68, P = 0.023). Conclusion: Incidence of late non-LD-PNS is higher among SR to CRT, suggesting a potential role of the changes in the anatomical relationship between left phrenic nerve and coronary veins.

Entrapment of "PV-Tracker" guidewire in the pulmonary veins during atrial fibrillation ablation with PVAC Gold.

We report the entrapment of Pulmonary Vein Ablation Catheter (Medtronic, Minneapolis, MN, USA) and its guidewire within the right pulmonary veins in two patients. The catheters could be retrieved without complications but they were disabled in both cases. This nondescribed incident should be recognized by PVAC users since it may be a source of potential severe complications during pulmonary vein isolation procedures.

Phrenic paralysis during cardiac electronic device implantation: incidence, causes and clinical course.

AIMS: Phrenic paralysis is a known complication of central venous catheterization, but it is not listed as a complication related to cardiac implantable electronic device (CIED) implants. The aim of this study is to describe the incidence, causes, clinical picture, and management of phrenic paralysis occurring in this scenario. METHODS AND RESULTS: We retrospectively analysed data from our CIED implantation database and identified those patients who suffered phrenic paralysis during the implantation procedure. Four of 891 patients (subclavian puncture in 626) developed phrenic paralysis during pacemaker or defibrillator implant procedures. Severe respiratory failure needing ventilatory support occurred in two, being the phrenic paralysis transient in all of the cases. CONCLUSIONS: Transient phrenic paralysis may occur during CIED implantation probably related to the infiltration of local anaesthesia in the subclavian area. Mechanism, prevention, and management are discussed.

Incidence of arrhythmias in a large cohort of patients with current implantable cardioverter-defibrillators in Spain: results from the UMBRELLA Registry.

AIMS: The benefit of implantable cardioverter-defibrillators (ICDs) in patients at risk of sudden death has been established in randomized clinical trials (RCTs) using the ICD models available at the time. However, observational large-scale data on the incidence of arrhythmias in up-to-date ICDs implanted according to the current guidelines are scarce. The aim was to assess the incidence of arrhythmias in a large, current ICD population based on a blinded peer review of the detected episodes. METHODS AND RESULTS: UMBRELLA is a multicentre, observational registry of ICD patients followed by remote monitoring. Stored episodes were classified by a blinded committee of experts. Subgroup analyses were based on clinical profiles established by previous pivotal RCTs of ICDs. Of 1514 enrolled patients, 605 (39.9%) patients had 5951 episodes after 26 ± 17 months follow-up, being 3353 of them (56.3%) sustained ventricular arrhythmias (SVA), and 13.2% of SVA were self-terminated. Appropriate and inappropriate shocks occurred in 11.6 and 5% of patients, respectively. The 3 years cumulative incidence of SVA was 25% (95% CI: 21-28%) in primary prevention patients and 41% (95% CI: 36-47%) in secondary prevention patients (P < 0.001). Male gender, secondary prevention, and atrial fibrillation as basal rhythm were significantly related to a higher incidence of SVA. CONCLUSION: This real-world analysis suggests that modern ICD patients have a low rate of appropriate and inappropriate shocks. The risk of SVA in secondary prevention patients is less than what has been reported in RCTs.

Etiology and Programming Effects on Shock Efficacy in ICD Recipients.

BACKGROUND: We sought to assess the efficacy of high-energy shocks to restore rhythm and predictors of success in patients with sustained ventricular arrhythmias and implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: Data from 162 patients included in the UMBRELLA study that experienced one or more episodes of ventricular tachycardia (VT) for which ICD shocks of at least 30 Joules were delivered (appropriate high-energy shocks) were analyzed. In total, 456 ventricular arrhythmia episodes were registered. Forty four episodes (9.6%) from 39 patients (24%) had at least one ineffective high-energy shock delivered. Hypertrophic cardiomyopathy was more frequent among patients with unsuccessful shocks (10.3% vs 2.4%). Patients with ineffective shocks had higher proportion of sustained monomorphic ventricular arrhythmias (86.4%; the other 13.6% were sustained polymorphic and ventricular fibrillation [VF]) compared with patients with all their shocks effective (62.9%, P = 0.02). No statistical differences were found between groups in time from detection to the high-energy shock delivery, in tachycardia cycle length, or in antitachycardia pacing, but patients with ineffective high-energy shocks had higher proportion of previously ineffective low-energy shock (9.1% vs 0.5%, P = 0.01). CONCLUSION: We found a substantial rate of ineffective high-energy shocks for the treatment of VT or VF in patients with ICD. High-energy shock efficacy seems to be reduced by hypertrophic cardiomyopathy and by the administration of previous low-energy shocks.

Atrial Rate-Responsive Pacing and Incidence of Sustained Atrial Arrhythmias in Patients with Implantable Cardioverter Defibrillators.

BACKGROUND: Atrial rate-responsive pacing (RRP) has proved to be safe in pacemaker recipients with chronotropic incompetence. Although RRP is available in all current implantable cardioverter defibrillators (ICDs), the outcomes of this pacing mode in ICD patients are unknown. The aim is to evaluate the relationship between atrial RRP and atrial arrhythmias in ICD recipients. METHODS: Dual-chamber and triple-chamber ICD patients were included in this multicenter cohort study. Patients with permanent atrial fibrillation (AF) or VVI pacing mode were excluded. The number and duration of atrial tachycardia (AT)/AF episodes were assessed. RESULTS: Data from 415 patients and 80,707 AT/AF episodes (median duration: 0.4 hours) were collected after a 21.3 ± 14.1-month follow-up. Atrial RRP was programmed in 90 (21.7%) patients and was associated with a higher atrial pacing percentage in the overall study population (51.2 ± 33.8% vs 18.4 ± 25.7%, P < 0.001) and to a higher ventricular pacing percentage among dual-chamber devices (22.3 ± 37.6% vs 9.3 ± 25%, P < 0.001). Independent factors associated with sustained AT/AF episodes (>23 hours) were previous AF (odds ratio [OR]: 7.98; 95% confidence interval [CI]: 4.11-15.47; P < 0.001) and atrial RRP (OR: 3.58; 95% CI: 1.82-7.03; P < 0.001). RRP was related to a lower sustained AT/AF episodes-free survival both in patients with a history of AF (43% vs 70%, P = 0.035) and without a history of AF (82% vs 97%, P = 0.004) at 2 years. CONCLUSIONS: Atrial RRP in ICD patients was related to a higher incidence of sustained atrial arrhythmias. This pacing mode may have an atrial proarrhythmic effect on ICD patients, especially among those with a history of AF.

Shock Reduction With Multiple Bursts of Antitachycardia Pacing Therapies to Treat Fast Ventricular Tachyarrhythmias in Patients With Implantable Cardioverter Defibrillators: A Multicenter Study.

INTRODUCTION: An empirical sequence of burst antitachycardia pacing (ATP) is effective in terminating fast ventricular tachycardias (FVT) in patients with implantable cardioverter-defibrillators (ICDs). We aimed to determine whether multiple ATP bursts for termination of FVT results in shock reduction compared to a single ATP burst. METHODS AND RESULTS: We analyzed data from the Umbrella trial, a multicenter prospective observational study of ICD patients followed by the CareLink Monitoring System. We compared the safety and effectiveness of a single ATP burst (Group 1) with a strategy of successive ATP sequences (Group 2) for termination of FVT episodes (cycle lengths 250-320 milliseconds) before shock therapy. Over a mean follow-up of 35 months, a total of 650 FVT episodes were detected in 154 patients (mean cycle length: 299 ± 18 milliseconds). Effectiveness of the first burst ATP in Group 1 was 73% and shocks were required in 27% of episodes. Effectiveness of the first burst ATP in Group 2 was 77%, and this increased to 91% with the third or successive ATP bursts. Shocks were required in 9% of episodes in group 2, representing a 67% reduction in the need of high-energy shocks. Median duration of FVT episodes and mortality in both groups were similar. Multivariate analysis indicated that programming multiple ATP bursts (OR 3.4, 95%CI 1.7-6.8, P = 0.001) was an independent predictor of ATP effectiveness. CONCLUSION: This study provides first evidence that a strategy of multiple burst ATP sequences for termination of FVT episodes leads to a clinically meaningful reduction in the need for shocks.

Cavo-tricuspid isthmus radiofrequency ablation using a novel remote navigation catheter system in patients with typical atrial flutter.

AIMS: A new remote catheter system (AMIGO™ Remote Catheter System) compatible with conventional ablation catheters is now commercially available but no data about its performance in clinical use during ablation have been reported. This study evaluates the feasibility, efficacy, and safety of cavo-tricuspid isthmus (CTI) ablation with this system in patients with typical atrial flutter (AFl). METHODS AND RESULTS: Sixty patients with typical AFl underwent CTI ablation using the new remote catheter navigation system with 8 mm tip or irrigated catheters in three centres following each centre's routine practice. The endpoint was stable bidirectional CTI block. CTI ablation was successful in 98% of patients. Ablation was completed manually in one patient. The overall procedure, fluoroscopy, and radiofrequency times (median ± standard deviation, range) were 123 ± 42 (50-250), 24 ± 13 (3-82), and 10 ± 8 (1.17-43.3) min, respectively. Three patients had vascular complications not requiring surgical intervention. There were no complications related to the remote catheter manipulation system. CONCLUSION: Cavo-tricuspid isthmus ablation for typical AFl can be safely and effectively performed with the AMIGO™. The learning curve seems to be short even for physicians with limited ablation experience.

Ivabradine for controlling heart rate in permanent atrial fibrillation: A translational clinical trial.

BACKGROUND: Pharmacological options for rate control in atrial fibrillation are scarce. Ivabradine was postulated to reduce the ventricular rate in this setting. OBJECTIVES: The objectives of this study were to evaluate the mechanism of inhibition of atrioventricular conduction produced by ivabradine and to determine its efficacy and safety in atrial fibrillation. METHODS: The effects of ivabradine on atrioventricular node and ventricular cells were studied by in vitro whole-cell patch-clamp experiments and mathematical simulation of human action potentials. In parallel, a multicenter, randomized, open-label, phase III clinical trial compared ivabradine with digoxin for uncontrolled permanent atrial fibrillation despite ß-blocker or calcium channel blocker treatment. RESULTS: Ivabradine 1 µM inhibited "funny" current and rapidly activating delayed rectifier potassium channel current by 28.9% and 22.8%, respectively (P < .05). The sodium channel current and L-type calcium channel current were reduced only at 10 µM. Ivabradine slowed the firing frequency of a modeled human atrioventricular node action potential by 10.6% and induced a minimal prolongation of ventricular action potential. Thirty-five (51.5%) patients were randomized to ivabradine and 33 (49.5%) to digoxin. The mean daytime heart rate decreased by 11.6 beats/min (-11.5%) in the ivabradine arm (P = .02) vs 19.6 (-20.6%) in the digoxin arm (P < .001), although the noninferiority margin of efficacy was not met (Z = -1.95; P = .97). The primary safety end point occurred in 3 patients (8.6%) on ivabradine and in 8 (24.2%) on digoxin (P = .10). CONCLUSION: Ivabradine produced a moderate rate reduction in patients with permanent atrial fibrillation. The inhibition of funny current in the atrioventricular node seems to be the main mechanism responsible for this reduction. Compared with digoxin, ivabradine was less effective, was better tolerated, and had a similar rate of serious adverse events.