Unusual atrial pacing induced by type II far-field p-wave sensing in a patient with complete atrioventricular block.

An 88-year-old Japanese woman underwent DDD pacemaker (MicroPort KORA 250 DR, V lead: VEGA R52) implantation for complete atrioventricular block. A 12-lead electrocardiogram for a routine examination showed atrial pacing within the intrinsic P wave, followed by inhibition of ventricular pacing. Pacemaker interrogation revealed no abnormalities in the basic parameters; however, ventricular pacing was inhibited by far-field sensing of intrinsic atrial waves before atrial events; type II far-field P-wave sensing. As a result, unusual atrial pacing occurred due to the pause suppression algorithm, which is the one of the functions that prevent atrial fibrillation development.

Spatiotemporal incremental change of radiofrequency catheter ablation-associated pulmonary vein calcifications.

We presented a detailed time course of RFCA-associated PV calcification process. Because RFCA-associated PV calcification may progress over time even with a single ablation, long-term caution should be paid in cases of especially extensive ablation and/or patients with stiff LA syndrome.

Belt-type electrocardiograph for diagnosing palpitation occurring only during high-intensity exercise in athletes.

Belt-type ambulatory electrocardiograph (EV-201) is an arrhythmia diagnostic device that can record an electrocardiogram (ECG) for a maximum of 2 weeks. Here, we report the novel utility of EV-201 in detecting arrhythmias in two professional athletes. Treadmill exercise test and Holter ECG failed to detect arrhythmia because of insufficient exercise, electrocardiogram noise. However, by wearing EV-201 only during a marathon run, supraventricular tachycardia onset and termination were successfully detected. Throughout, both athletes were diagnosed with fast-slow atrioventricular nodal re-entrant tachycardia. Therefore, EV-201 enables long-term belt-type recording, thereby being useful in detecting tachyarrhythmias that occur infrequently and during strenuous exercises. Learning objective: Diagnosis of arrhythmias during high-intensity exercise in athletes by conventional electrocardiography is sometimes difficult due to inducibility and frequency of arrythmias or motion artifacts. The primary finding of this report is that EV-201 is useful in diagnosing such arrhythmias. The secondary finding is that fast-slow atrioventricular nodal re-entrant tachycardia is a common occurrence in arrhythmias among athletes.

"Carryover phenomenon" in subcutaneous implantable cardioverter-defibrillator: Residual energy caused early shock to subsequent ventricular tachycardia.

We reported a case of early S-ICD shock due to the carryover of previously charged energy. Depending on the interval with the preceding event, an early shock may occur for the subsequent event. Especially, in cases where non-sustained VTs occur frequently, the indication for S-ICD surgery should be considered carefully.

Relationship between Effective Refractory Period and Inducibility of Atrial Fibrillation from the Superior Vena Cava after Pulmonary Vein Isolation.

In terms of the pulmonary vein (PV), atrial fibrillation (AF) patients have a shorter effective refractory period (ERP) than those without AF and a large dispersion of the ERP. Although the frequency of AF from the superior vena cava (SVC) was the highest among non-PV foci, the characteristics of the ERP in the SVC (SVC-ERP) were unclear. The purpose of this study was to elucidate the relationship between SVC-ERP and the inducibility of AF after PV isolation (PVI).Consecutive 28 patients who underwent PVI were included. After successful PVI, the SVC-ERP was measured at three positions in SVC. Rapid electrical stimuli were delivered at the shortest SVC-ERP to induce AF. Patients in whom AF was induced were assigned to the SVC-induced group (SIG), and the remaining patients were the non-SVC-induced group (non-SIG). The size of the SVC sleeve was evaluated via three-dimensional electroanatomic mapping.The SIG had a significantly shorter average SVC-ERP (236.0 ± 25.2 versus 294.8 ± 36.8 ms, P < 0.001), whereas SVC-ERP dispersion was not significantly different (30.0 ± 25.4 versus 33.3 ± 20.1 ms, P = 0.56). Although the longer SVC diameter was significantly longer in the SIG (27.4 ± 4.3 versus 22.9 ± 4.6 mm, P = 0.03), the SVC-ERP was significantly associated with pacing inducibility of AF after adjustment for the longer SVC diameter (odds ratio: 0.96 [1 ms increments], P = 0.01).The SIG had a shorter SVC-ERP, whereas the dispersion was not significantly different between the two groups. The SVC-ERP can be one of the mechanisms of arrhythmogenicity for AF originating from the SVC.

Relationship between device displacement distance toward the caudal side during standing and pocket position laterality.

BACKGROUND: The displacement of cardiac implantable electronic devices (CIEDs) toward the caudal side during standing after CIED implantation could cause lead dislodgement. This study investigated the relationship between supine pocket position and standing CIEDs' displacement distance after the implantation. METHODS: After CIED surgeries performed at 2 hospitals between 2012 and 2020, 134 patients underwent postoperative chest x-rays in the supine and standing positions during hospitalization. To measure the displacement distance of CIEDs from the supine to the standing position, we identified the first thoracic vertebrae (Th1) in the supine position using the first rib as an index, drew a horizontal line at the lower edge of the Th1, and calculated the distance from that point to the upper edge of the CIED. The difference between measures for the two positions was compared. At the position of the pocket in the thorax in the supine position, the ratio of the distance between the thorax and the device is defined as the device thorax ratio (DTR). We examined the relationship between DTR and CIED displacement distance. RESULTS: In this study, we included 134 patients (53% men; median age, 79 years, body mass index, 22.3 ± 3.4; pacemaker 93%, left implantation 96%). We found that the more lateral the position of the CIED pocket, the more the CIED fell when standing (confidence interval = 0.34-0.60, P < .001). CONCLUSIONS: The farther the CIED was implanted outside the thorax in the supine position, the more significantly the CIED was displaced in the standing position.

Accessory pathway ablation during atrial fibrillation in Ebstein anomaly.

An 84-year-old woman with type B Wolff-Parkinson-White (WPW) with Ebstein anomaly was admitted with heart failure. She had rapid wide QRS tachycardia due to accessory pathway (AP) conduction associated with atrial fibrillation (AF). Since transesophageal echocardiography before catheter ablation showed a left atrial thrombus, ablation was performed using a 3D mapping system under AF. After marking the functional tricuspid anulus with intra-cardiac echocardiography, 3D intra-cardiac electrogram visualization (ripple map) during AF enabled clear identification of location of the AP. After ablation, there was no complication of cerebral infarction, and the heart failure improved.

Large discrepancy in optimal atrioventricular delay between sensed and paced atrial events in a pacemaker patient.

A 74-year-old man experienced complete atrioventricular (AV) block 2 days after catheter ablation for right atrial (RA) macroreentrant tachycardia. We performed DDD pacemaker implantation with atrial septal pacing because other sites of pacing threshold were not acceptable. The maximum left ventricular outflow tract velocity time integral was 15.8 cm with sensed AV delay (40 ms) and 15.0 cm with paced AV delay (220 ms); however, this exceeded the pacemaker's maximum difference of 100 ms. We herein report the case of a large discrepancy in optimal AV delay intervals between sensed and paced atrial events, requiring consideration of proper pacemaker settings.

Heart failure caused by iatrogenic atrial septal defect after cryoballoon ablation for atrial fibrillation.

An 83-year-old man with no structural heart disease underwent pulmonary vein isolation (PVI) for symptomatic paroxysmal atrial fibrillation (AF). The PVI was successfully performed by cryoballoon ablation with a single transseptal puncture. A 12Fr deflectable sheath and an 8.5Fr long sheath crossed the interatrial septum via the same puncture site. Five months after PVI, the patient was readmitted because of heart failure and recurrence of AF. The echocardiogram showed a large (10.7 × 5.8 mm) iatrogenic atrial septal defect (IASD) at the previous puncture site. Both right-to-left and left-to-right shunts were observed during systole and diastole, respectively. Despite the initiation of optimal medical therapy for heart failure, symptoms were not completely controlled and IASD remained 11 months after PVI. Eventually, he received multiple additional PVI for recurrence of AF and percutaneous transcatheter closure (13 mm disc for 10.9 × 8.9 mm- IASD), then heart failure was controlled with the improvement of the right atrial and ventricular size. Although the induction of heart failure by IASD after PVI is rare, it should be noted as one of the causes, especially after cryoballoon ablation with simultaneous mapping catheter insertion via a single transseptal puncture. .

Incidence of out-of-hospital cardiac arrests and survival rates after 1 month among the Japanese working population: a cohort study.

OBJECTIVES: The prevention and improvement of the prognosis of out-of-hospital cardiac arrests (OHCAs) are important issues especially with respect to their social and economic significance in working populations. The age distribution of the working population in Japan is expected to change continually due to its ageing society and extension of retirement; however, few reports have examined the long-term condition of OHCA in the working population, defined by age. The aim of this study was to determine the incidence of OHCAs and the survival rates after 1 month, among the Japanese working population, defined by age, considering the changing age distribution. DESIGN AND SETTING: We analysed the All-Japan Utstein registry, a prospective, nationwide, population-based, observational registry (2005-2016). PARTICIPANTS: From the registry, 212 961 patients with OHCA from the Japanese working population (defined aged 20-69 years), with only cardiogenic aetiology participated in this study. These patients were further divided into four groups according to the type of citizen bystander (family, friends, work-colleagues and passers-by). PRIMARY AND SECONDARY OUTCOME MEASURES: The main outcomes were 1-month survival with favourable neurological outcomes. RESULTS: The incidence of OHCAs, in any age group, was almost constant during the 12-year period. The work-colleagues had the best prognosis despite having significantly longer times to initial defibrillations compared with the passers-by (13 vs 12 min, respectively, p<0.001) that was associated independently with 1-month survival with favourable neurological outcomes (adjusted OR: 0.94 (1 min increments), p<0.001). CONCLUSIONS: In the 12-year period, the incidence of OHCAs in any age group remained almost constant, whereas the prognosis improved each year. Reducing the time to initial defibrillation may further improve the prognosis of OHCAs with a work-colleague bystander.

Adenosine revives catheter-induced mechanical blocks in radiofrequency ablation.

Adenosine can hyperpolarize the atrial action potential, which helps rapidly re-establish the membrane potential in ablated sites and unmask "dormant conduction." It has been reported that pharmacological agents, including adenosine, were unable to revive traumatized tissues. We present the first case of the catheter-induced mechanical block ("bump" phenomenon) that was unmasked with adenosine administration in the working myocardium of the superior vena cava. This result may be because, unlike before, we could determine the force of contact between the tip of the ablation catheter and the myocardial tissue. This case suggests the clinical usefulness of adenosine for unmasking bumped sites.

RR interval variability in the evaluation of ventricular tachycardia and effects of implantable cardioverter defibrillator therapy.

BACKGROUND: An implantable cardioverter defibrillator (ICD) is the most reliable therapeutic device for preventing sudden cardiac death in patients with sustained ventricular tachycardia (VT). Regarding its effectiveness, targeted VT is defined based on the tachyarrhythmia cycle length. However, variations in RR interval variability of VTs may occur. Few studies have reported on VT characteristics and effects of ICD therapy according to the RR interval variability. We aimed to identify the clinical characteristics of VTs and ICD therapy effects according to the RR interval variability. METHODS: We analyzed 821 VT episodes in 69 patients with ICDs or cardiac resynchronization therapy defibrillators. VTs were classified as irregular when the difference between two successive beats was >20 ms in at least one of 10 RR intervals; otherwise, they were classified as regular. We evaluated successful termination using anti-tachycardia pacing (ATP)/shock therapy, spontaneous termination, and acceleration between regular and irregular VTs. The RR interval variability reproducibility rates were evaluated. RESULTS: Regular VT was significantly more successfully terminated than irregular VT by ATP. No significant difference was found in shock therapy or VT acceleration between the regular and irregular VTs. Spontaneous termination occurred significantly more often in irregular than in regular VT cases. The reproducibility rates of RR interval variability in each episode and in all episodes were 89% and 73%, respectively. CONCLUSIONS: ATP therapy showed greater effectiveness for regular than for irregular VT. Spontaneous termination was more common in irregular than in regular VT. RR interval variability of VTs seems to be reproducible.

Importance of the length of the myocardial sleeve in the superior vena cava in patients with atrial fibrillation.

BACKGROUND: Pulmonary vein (PV) antrum isolation (PVAI) has proven to be a useful strategy for radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF) worldwide. However, non-PV foci, especially from the superior vena cava (SVC), play an important role in initiating and maintaining AF. METHODS: In all, 427 consecutive patients with non-valvular AF who were admitted to our hospitals to undergo RFCA of AF using an EnSite™ system were evaluated. The length from the top of the sinus node to the top of the myocardial sleeve of SVC (L-SVC), longer and shorter diameter of SVC of 1 cm above of junction of right atrium and SVC, and local activation time (LAT) of SVC were measured. Then, the SVC firing was evaluated by an intravenous administration of isoproterenol and adenosine triphosphate. RESULTS: L-SVC, longer and shorter diameter of SVC, and LAT of SVC were significantly longer in the SVC firing group than non-SVC firing group (P < .05). Moreover, in accordance with the L-SVC, the frequency of the SVC firing significantly increased (P < .001). A univariate analysis and multivariate statistical analysis revealed that L-SVC longer than 37.0 mm (odds ratio 6.39) and longer diameter of SVC (odds ratio 6.78) were independent risk factors for SVC firing in patients with AF who underwent RFCA of AF. CONCLUSIONS: In view of these findings, L-SVC longer than 37.0 mm longer diameter SVC longer than 17.0 mm may be one of the important predictors of SVC firing in patients with AF.