A rare case of pacemaker mediated tachycardia caused by intrinsic conduction search function of a dual chamber pacemaker.

Pacemaker-mediated tachycardia (PMT) is a well-described cause of tachyarrhythmia in patients with dual chamber pacemakers (Barold, 1991 [1]). PMT is usually caused by common triggers including premature ventricular or atrial complexes (Alasti et al., 2018 [2]). However, PMT can also be triggered by other uncommon mechanisms. Intrinsic conduction search function is a feature available in some dual chamber permanent pacemakers that periodically looks for intrinsic conduction by gradually prolonging the preprogrammed AV delay in an attempt to minimize ventricular pacing (Calvi et al., 2017; Pakarinen and Toivonen, 2013 [3,4]). Here, we report a rare case of PMT triggered by intrinsic conduction search function.

Narrow QRS Tachycardia in a Patient with Tachycardiomyopathy: What Is the Mechanism?

A 50-year-old female presented with incessant palpitation of 2 weeks duration. She was hemodynamically stable and there was no evidence of heart failure. A transthoracic echocardiogram showed mild left ventricular (LV) dysfunction with LV ejection fraction of 45%. Electrocardiogram (12 lead and rhythm strip) was taken during the palpitation. What is the mechanism?

Colchicine to Prevent Atrial Fibrillation Recurrence After Catheter Ablation: A Randomized, Placebo-Controlled Trial.

BACKGROUND: Inflammation may promote atrial fibrillation (AF) recurrence after catheter ablation. This study aimed to evaluate a short-term anti-inflammatory treatment with colchicine following ablation of AF. METHODS: Patients scheduled for ablation were randomized to receive colchicine 0.6 mg twice daily or placebo for 10 days. The first dose of the study drug was administered within 4 hours before ablation. Atrial arrhythmia recurrence was defined as AF, atrial flutter, or atrial tachycardia >30 s on two 14-day Holters performed immediately and at 3 months following ablation. RESULTS: The modified intention-to-treat population included 199 patients (median age, 61 years; 22% female; 70% first procedure) who underwent radiofrequency (79%) or cryoballoon ablation (21%) of AF. Antiarrhythmic drugs were prescribed at discharge in 149 (75%) patients. Colchicine did not prevent atrial arrhythmia recurrence at 2 weeks (31% versus 32%; hazard ratio [HR], 0.98 [95% CI, 0.59-1.61]; P=0.92) or at 3 months following ablation (14% versus 15%; HR, 0.95 [95% CI, 0.45-2.02]; P=0.89). Postablation chest pain consistent with pericarditis was reduced with colchicine (4% versus 15%; HR, 0.26 [95% CI, 0.09-0.77]; P=0.02) and colchicine increased diarrhea (26% versus 7%; HR, 4.74 [95% CI, 1.95-11.53]; P<0.001). During a median follow-up of 1.3 years, colchicine did not reduce a composite of emergency department visit, cardiovascular hospitalization, cardioversion, or repeat ablation (29 versus 25 per 100 patient-years; HR, 1.18 [95% CI, 0.69-1.99]; P=0.55). CONCLUSIONS: Colchicine administered for 10 days following catheter ablation did not reduce atrial arrhythmia recurrence or AF-associated clinical events, but did reduce postablation chest pain and increase diarrhea.

Inappropriate Implantable Cardioverter-Defibrillation Detection of Ventricular Fibrillation Induced by Transcutaneous Electrical Nerve Stimulation.

We describe 2 cases of electromagnetic interference (EMI) with a transcutaneous electrical nerve stimulation (TENS) device in patients with implantable cardioverter-defibrillators (ICDs). Both patients were using DR-HO'S® pain therapy system for chronic back pain (VGH Solutions Inc., Markham, ON, Canada). In both cases, EMI was inappropriately labeled as ventricular fibrillation. In the first case, the noise detected was of a short duration and did not fulfill the discriminator criteria to deliver ICD therapy. In the second case, inappropriate anti-tachycardia pacing and shocks resulting from EMI were delivered. Both patients were advised not to use TENS devices at home. Increased awareness of EMI resulting in inappropriate ICD therapies using these devices is needed.

Catheter Ablation of Hemodynamically Unstable Ventricular Tachycardia in a Patient with Dextro - Transposition of the Great Arteries and Mustard's Repair.

INTRODUCTION: A patient with D-TGA and surgical repair (Mustard's procedure) presented with appropriate ICD shocks due to monomorphic ventricular tachycardia, refractory to antiarrhythmic medications. METHODS AND RESULTS: The patient underwent an electrophysiological study and catheter ablation for the VT. Substrate and pace mapping techniques, with the help of an electroanatomical mapping system, was used to localize and ablate the tachycardia successfully. CONCLUSIONS: In patients with D-TGA and Mustard's repair, scar tissue resulting from VSD repair can act as a substrate for recurrent VT. Catheter ablation of VT is useful in management of VT that occurs despite antiarrhythmic therapy and/or when it is unstable.

Outcomes and Safety of Fluoroless Catheter Ablation for Atrial Fibrillation.

BACKGROUND: Intracardiac echocardiography and 3D mapping systems allow catheter ablation for atrial fibrillation (AF) to be conducted without fluoroscopy; however, the safety and effectiveness of fluoroless AF ablation are not well defined. METHODS: We examined consecutive radiofrequency AF catheter ablations at a large academic teaching hospital from November 2017 to July 2019. Outcomes for fluoroscopy-guided (N = 176) and fluoroless (N = 147) ablations were compared. Cases were designated as fluoroless at the outset of the procedure. RESULTS: Mean age was 59.5 ± 10 years, 66.9% were male, 71.8% had paroxysmal AF, and the mean CHA2DS2-VASc score was 1.7 ± 1.4. There were no differences in patient baseline characteristics. In the fluoroless group, minimal fluoroscopy was used in 17 patients (median, 3 seconds; interquartile range, 1.2-4.8). Mean procedure time, fluoroscopy time, and radiation dose (± standard deviation) were greater in the fluoroscopy group compared with the fluoroless group (194 ± 56 vs 176 ± 46 minutes, P = 0.0021; 10.7 ± 6.6 vs 0.008 ± 0.03 minutes, P < 0.0001; 2759.2 ± 1911 vs 5.4 ± 24 µGy m2, P < 0.0001). In multivariable linear regression models, fluoroless AF ablation was independently associated with reduced procedure times (ß = -16.5 minutes, P = 0.01). Acute procedural success (95.5% vs 98.6%, P = 0.1), complication rates (4.5% vs 2.0%, P = 0.24), and 1-year AF recurrence rates (28.7% vs 27.1%, log-rank P = 0.69) were similar between fluoroscopy and fluoroless groups. Excluding the 17 patients receiving fluoroscopy in the fluoroless group did not impact our results (P = 0.013). After exclusion of redo cases, fluoroless AF ablation was no longer associated with reduced procedure times (ß = -11.4 minutes, P = 0.106). CONCLUSIONS: Fluoroless radiofrequency AF ablation had similar effectiveness and safety compared with conventional fluoroscopy-guided AF ablation.

CONTEXTE: L'échocardiographie intracardiaque et les systèmes de cartographie 3D permettent l'ablation par cathéter de la fibrillation auriculaire (FA) sans fluoroscopie; l'innocuité et l'efficacité d'une telle approche ne sont toutefois pas bien connues. MÉTHODOLOGIE: Nous avons examiné les résultats d'ablations par cathéter de la FA par radiofréquences menées de façon consécutive dans un hôpital universitaire d'envergure entre novembre 2017 et juillet 2019. Les résultats des ablations par fluoroscopie (n = 176) et des ablations sans fluoroscopie (n = 147) ont été comparés. Les cas étaient désignés comme n'ayant pas utilisé la fluoroscopie à la fin de l'intervention, le cas échéant. RÉSULTATS: L'âge moyen était de 59,5 ± 10 ans, 66,9 % des patients étaient des hommes, 71,8 % étaient atteints de FA paroxystique, et le score CHA2DS2-VASc moyen était de 1,7 ± 1,4. Il n'y avait pas de différences entre les caractéristiques des patients au départ. Dans le groupe ayant subi une ablation sans fluoroscopie, une fluoroscopie minimale a été utilisée chez 17 patients (médiane : 3 secondes; intervalle interquartile : 1,2-4,8). La durée moyenne de l'intervention, la durée de la fluoroscopie, et la dose de rayonnements (± écart type) ont été plus élevées dans le groupe avec fluoroscopie que dans le groupe sans fluoroscopie (194 ± 56 vs 176 ± 46 minutes, p = 0,0021; 10,7 ± 6,6 vs 0,008 ± 0,03 minute, p < 0,0001; 2759,2 ± 1911 vs 5,4 ± 24 µGy m2, p < 0,0001). Dans des modèles de régression linéaire multivariables, l'ablation de la FA sans fluoroscopie a été associée de façon indépendante à des interventions de plus courte durée (ß = −16,5 minutes, p = 0,01). Le succès immédiat de l'intervention (95,5 % vs 98,6 %, p = 0,1), le taux de complications (4,5 % vs 2,0 %, p = 0,24), et le taux de récidive de la FA après 1 an (28,7 % vs 27,1 %, p (test du log-rank = 0,69) ont été comparables dans les groupes avec et sans fluoroscopie. L'exclusion des 17 patients chez qui la fluoroscopie avait été utilisée dans le groupe sans fluoroscopie n'a pas modifié ces résultats (p = 0,013). Après l'exclusion des cas où l'intervention était une reprise, l'ablation de la FA sans fluoroscopie n'était plus associée à une réduction des durées d'intervention (ß = −11,4 minutes, p = 0,106). CONCLUSIONS: L'ablation de la FA par radiofréquences sans fluoroscopie est associée à une efficacité et à une innocuité comparables à celles de l'ablation de la FA classique guidée par fluoroscopie.

[Real time intracardiac electrograms for the diagnosis of pacemaker malfunction]. / Electrogramas intracardíacos en tiempo real en el diagnóstico de fallas de marcapasos.

Chronic ventricular lead dislodgement is an infrequent complication of pacemaker implantation. Occasionally, the dislodged lead may sense and capture a chamber in which the lead was not originally positioned. Intracardiac real time electrograms and channel markers are useful tools for the diagnosis of pacemaker malfunction. We present the case of a patient with a ventricular lead dislodgement into the atrium. The ventricular lead was able to sense and capture the atrium. Initial diagnosis was performed based on the deductive analysis of intracardiac real time electrograms and channel markers and confirmed by chest X-ray.

Tricuspid valve regurgitation following temporary or permanent endocardial lead insertion, and the impact of cardiac resynchronization therapy.

BACKGROUND: While some studies indicate that permanent pacemaker implantation is associated with development of tricuspid regurgitation (TR), other studies indicate no association.Little is known about the impact of temporary lead insertion during ablation procedures, or whether therapy (CRT) prevents TR post-device implantation. HYPOTHESIS: We hypothesized that permanent, but nottemporary endocardial leads, are associated with development of TR, and that CRT would prevent (physiologic) TR. METHODS: We performed a retrospective study of consecutive patients who underwent first device or radiofrequency catheter ablation over a 12-month period at a single, tertiary academic center who underwent pre- and post-procedure echocardiography. RESULTS: In the 89 patients in the device group, the degree of TR significantly increased ≥ 1 grade post-permanent lead implantation: 9 had less TR, 46 were unchanged, and 34 had more TR(p=0.005). TR increased in the 62 patients who underwent device implantation without CRT (p=0.005), but did not increase in the 27 patients with CRT (p=0.47). In the 66 patients in the ablation group, there was no significant change in TR post-ablation: 8 had less TR, 48 were unchanged, and 10 had more TR (p=0.31). CONCLUSION: Permanent endocardial lead implantation was associated with an increase in TR; however, patients who underwent device implantation with CRT did not have an increase in TR.Temporary lead insertion during ablation was not associated with changes in the degree of TR. A large, prospective study is needed to accurately define the incidence and exact mechanisms of permanent endocardial lead-related TR.

Pacemaker-detected atrial fibrillation in patients with pacemakers: prevalence, predictors, and current use of oral anticoagulation.

BACKGROUND: Dual-chamber pacemakers frequently document atrial fibrillation (AF) in patients without symptoms. Pacemaker-detected AF is associated with a 2.5-fold increased risk of stroke, although it is not established whether oral anticoagulation reduces this risk. This study sought to determine the prevalence and predictors of pacemaker-detected AF and to document current oral anticoagulant use. METHODS: A retrospective analysis included all patients from a single academic hospital who had pacemakers capable of documenting AF. Blinded evaluation of all echocardiograms conducted within 6 months of implantation was performed. RESULTS: Of 445 patients, pacemaker-detected AF was present in 246 (55.3%), who were older (74.3 ± 13.7 years vs 71.7 ± 14.4, P = 0.046), more likely to have a history of clinical AF (29.7% vs 19.1%, P = 0.01), and had a larger left atrial volume index (34.4 ± 11.8 mL/m(2) vs 30.0 ± 9.9 mL/m(2), P = 0.019) than the patients without pacemaker-detected AF. Among patients without a clinical history of AF, left atrial volume index was higher among those with pacemaker-detected AF (33.7 ± 11.3 mL/m(2) vs 29.0 ± 10.1 mL/m(2), P = 0.034). Anticoagulants were used in 35.3% of patients with pacemaker-detected AF, compared with 21.6% of patients without (P < 0.05). In patients with pacemaker-detected AF, anticoagulants were used more frequently among patients who also had clinical AF (58.9%) compared with those without (23.7%, P < 0.001). CONCLUSIONS: Pacemaker-detected AF occurs in 50% of pacemaker patients and is treated with anticoagulants in less than 25% of patients who do not have a history of clinical AF. Clinical trials are needed to determine the role of anticoagulation in this population.

Relevance of electrical remodeling in human atrial fibrillation: results of the Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial mechanisms of atrial fibrillation study.

BACKGROUND: In animal models of atrial fibrillation (AF), changes in atrial electrophysiological properties are associated with the development of AF. Their relevance to human AF is unclear. METHODS AND RESULTS: The Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial enrolled 2580 patients receiving a dual-chamber pacemaker, who were older than the age of 65 and had a history of hypertension, but no history of AF. Serial noninvasive electrophysiological testing was performed over 2 years in a subgroup of 485 patients. There were no differences in the clinical characteristics between patients with and those without device-detected atrial tachyarrhythmias during the first year. Patients with atrial tachyarrhythmias had longer paced (153±29 versus 145±28 ms; P=0.046) and sensed (128±46 versus 118±25 ms; P=0.06) P-wave durations and were more likely to have AF induced during electrophysiological testing (23.5% versus 13.6%; P=0.03). They had similar corrected sinus node recovery times at 90 bpm (388±554 versus 376 ± 466 ms; P=0.86), atrial effective refractory periods at 90 bpm (250±32 versus 248±36 ms; P=0.70), and rate-adaptive shortening of the atrial effective refractory periods (14±13 versus 12±14 ms; P=0.11). There were no significant differences in the change in electrophysiological properties over 2 years between patients with and those without atrial tachyarrhythmias. CONCLUSIONS: Prolonged P-wave duration, but not differences in atrial effective refractory periods, was associated with the development of atrial tachyarrhythmias in pacemaker patients.

Positive predictive value of device-detected atrial high-rate episodes at different rates and durations: an analysis from ASSERT.

BACKGROUND: Pacemakers can automatically identify and catalog atrial high-rate episodes (AHREs). While most AHREs represent true atrial tachyarrhythmia/atrial fibrillation (AT/AF), a review of stored electrograms suggests that a substantial proportion do not. As AHREs may lead to the initiation of oral anticoagulation, it is crucial to understand the relationship between AHREs and true AT/AF. OBJECTIVE: To compare the positive predictive value of AHREs for electrogram-confirmed AT/AF for various atrial rates and episode durations. METHODS: By using data from 2580 patients who participated in the ASymptomatic atrial fibrillation and Stroke Evaluation in pacemaker patients and the AF Reduction atrial pacing Trial, all AHREs >6 minutes and >190 beats/min with available electrograms were reviewed to determine whether they represented true AT/AF. The positive predictive value of these AHREs was assessed for episode durations of 6 minutes, 30 minutes, 6 hours, and 24 hours at atrial rates of 190 and 250 beats/min. RESULTS: Of 5769 AHREs >6 minutes and >190 beats/min, 82.7% were true AT/AF and 17.3% were false positives (predominantly due to repetitive non-re-entrant ventriculoatrial synchrony). False positives dropped to 6.8%, 3.3%, and 1.8% when the threshold duration was increased to 30 minutes, 6 hours, and 24 hours, respectively. Increasing the threshold heart rate to 250 beats/min added little to the positive predictive value when longer threshold durations were used. CONCLUSIONS: By using a cutoff of >6 minutes and >190 beats/min, the rate of false-positive AHREs is 17.3%, making physician review of electrograms essential. For AHREs lasting >6 hours, the rate of false positives is 3.3%, making physician review less crucial.

Hypertrophic cardiomyopathy and tachyarrhythmias detected by a pacemaker.

A 56-year-old man came to the Pacemaker Clinic for his regular pacemaker control. He had experienced a syncopal episode in the previous week. He had a previous diagnosis of non-obstructive hypertrophic cardiomyopathy. Due to a previous syncope and documented 2:1 infrahisian block, a dual-chamber permanent pacemaker had been implanted a few years before. The device was interrogated, showing several ventricular high rate episodes. A careful analysis of the stored intracardiac electrograms showed ventricular tachycardia (VT) with 2:1 ventriculoatrial conduction. The following presentation discusses the alternative diagnosis and clinical management in an unusual diagnosis of VT in the presence of non-obstructive hypertrophic cardiomyopathy.

An unusual mechanism causing inappropriate implantable cardioverter defibrillator shocks: transient reduction in R-wave amplitude.

Inappropriate shocks delivered by the implantable cardioverter defibrillator (ICD) are an increasingly recognized complication. The most frequent cause is related to supraventricular rhythms associated with fast conduction to the ventricles that are incorrectly detected as ventricular tachycardia leading to inappropriate antitachycardia pacing and/or shocks. Oversensing is a frequent cause of inappropriate shocks usually due to increased amplitude of the T-wave secondary to ischaemia or electrolyte disorders that lead to T-wave double counting. We describe an unusual case of T-wave double counting during sinus rhythm caused by transient reduction in R-wave amplitude with no changes in T-wave amplitude resulting in inappropriate shocks.

Cardiomiopatia hipertrófica e taquiarritmias detectadas por marcapasso / Hypertrophic cardiomyopathy and tachyarrhythmias detected by a pacemaker / Cardiomiopatía hipertrófica y taquiarritmias detectadas por marcapaso

Um homem de 56 anos veio à Clínica de Marcapasso para verificação de rotina de seu marcapasso. Ele havia apresentado um episódio de síncope na semana anterior. O paciente tinha um diagnostico prévio de cardiomiopatia hipertrófica (CMH) não-obstrutiva crônica. Devido a um episódio prévio de síncope e bloqueio infrahisiano 2:1 documentado, um marcapasso permanente de dupla câmara havia sido implantado alguns anos antes. O dispositivo foi verificado, mostrando vários episódios de altas freqüências ventriculares. Uma análise cuidadosa dos eletrogramas intracardíacos armazenados no dispositivo mostrou taquicardia ventricular (TV) com condução ventrículo-atrial 2:1. A seguinte exposição discute o diagnóstico alternativo e o manejo clínico em um diagnóstico não-usual de TV na presença de cardiomiopatia hipertrófica não-obstrutiva.

A 56-year-old man came to the Pacemaker Clinic for his regular pacemaker control. He had experienced a syncopal episode in the previous week. He had a previous diagnosis of non-obstructive hypertrophic cardiomyopathy. Due to a previous syncope and documented 2:1 infrahisian block, a dual-chamber permanent pacemaker had been implanted a few years before. The device was interrogated, showing several ventricular high rate episodes. A careful analysis of the stored intracardiac electrograms showed ventricular tachycardia (VT) with 2:1 ventriculoatrial conduction. The following presentation discusses the alternative diagnosis and clinical management in an unusual diagnosis of VT in the presence of non-obstructive hypertrophic cardiomyopathy.

Un varón de 56 anos vino a la Clínica de Marcapaso para verificación rutinaria de su marcapaso. Él había presentado un episodio de síncopa la semana anterior. El paciente tenía un diagnostico previo de cardiomiopatía hipertrófica (CMH) no obstructiva crónica. Un marcapaso permanente de doble cámara había sido implantado algunos años antes, en virtud de un episodio previo de síncopa y bloqueo infrahisiano documentado 2:1. Se verificó el dispositivo, que presentó varios episodios de altas frecuencias ventriculares. Un análisis cuidadoso de los electrogramas intracardiacos almacenados en el dispositivo reveló taquicardia ventricular (TV) con conducción ventrículo-atrial 2:1. La presente exposición discute el diagnóstico alternativo y el manejo clínico en un diagnóstico no usual de TV en la presencia de cardiomiopatía hipertrófica no obstructiva.

Electrogramas intracardíacos en tiempo real en el diagnóstico de fallas de marcapasos / Real time intracardiac electrograms for the diagnosis of pacemaker malfunction

El desplazamiento crónico del catéter ventricular es una complicación infrecuente del implante de marcapasos. Es infrecuente que un catéter desplazado sense y capture en una cámara donde no fue implantado originalmente. Se presenta el caso de un paciente con marcapasos doble cámara en el que el catéter ventricular se desplazó hacia la aurícula derecha. El catéter desplazado permite sensar y capturar la aurícula. El diagnóstico inicial se realizó mediante el análisis deductivo conjunto de los electrogramas en tiempo real y los eventos en los canales de registro ("marker channel"). La radiografía de tórax confirmó el diagnóstico presuntivo.

Chronic ventricular lead dislodgement is an infrequent complication of pacemaker implantation. Occasionally, the dislodged lead may sense and capture a chamber in which the lead was not originally positioned. Intracardiac real time electrograms and channel markers are useful tools for the diagnosis of pacemaker malfunction. We present the case of a patient with a ventricular lead dislodgement into the atrium. The ventricular lead was able to sense and capture the atrium. Initial diagnosis was performed based on the deductive analysis of intracardiac real time electrograms and channel markers and confirmed by chest X-ray.