Splitting the P-Wave: Improved Evaluation of Left Atrial Substrate Modification after Pulmonary Vein Isolation of Paroxysmal Atrial Fibrillation

Atrial substrate modification after pulmonary vein isolation (PVI) of paroxysmal atrial fibrillation (pAF) can be assessed non-invasively by analyzing P-wave duration in the electrocardiogram (ECG). However, whether right (RA) and left atrium (LA) contribute equally to this phenomenon remains unknown. The present study splits fundamental P-wave features to investigate the different RA and LA contributions to P-wave duration. Recordings of 29 pAF patients undergoing first-ever PVI were acquired before and after PVI. P-wave features were calculated: P-wave duration (PWD), duration of the first (PWDon-peak) and second (PWDpeak-off) P-wave halves, estimating RA and LA conduction, respectively. P-wave onset (PWon-R) or offset (PWoff-R) to R-peak interval, measuring combined atrial/atrioventricular and single atrioventricular conduction, respectively. Heart-rate fluctuation was corrected by scaling. Pre- and post-PVI results were compared with Mann–Whitney U-test. PWD was correlated with the remaining features. Only PWD (non-scaling: Δ=−9.84%, p=0.0085, scaling: Δ=−17.96%, p=0.0442) and PWDpeak-off (non-scaling: Δ=−22.03%, p=0.0250, scaling: Δ=−27.77%, p=0.0268) were decreased. Correlation of all features with PWD was significant before/after PVI (p<0.0001), showing the highest value between PWD and PWon-R (ρmax=0.855). PWD correlated more with PWDon-peak (ρ= 0.540–0.805) than PWDpeak-off (ρ= 0.419–0.710). PWD shortening after PVI of pAF stems mainly from the second half of the P-wave. Therefore, noninvasive estimation of LA conduction time is critical for the study of atrial substrate modification after PVI and should be addressed by splitting the P-wave in order to achieve improved estimations.

Case Report: A Rare Complication Following Catheter Ablation of Scar-Related Ventricular Tachycardia

Background: The substrate for ventricular tachycardia (VT) in patients with structural heart disease is usually complex and often requires extensive ablation. As a result, the incidence of major procedure-related complications has been reported to be higher when compared to patients without structural heart disease. In this study, we present a rare complication after extensive substrate modification of scar-related VT.Case: A 65-year-old man with ischemic cardiomyopathy was referred to the electrophysiology laboratory for radiofrequency ablation of VT following repetitive implantable cardioverter defibrillator shocks within a short period. As with hemodynamic intolerance of induced VT, an approach involving extensive endocardial substrate modification to reduce the arrhythmogenicity of the scars was adopted. After the procedure, the heart function of the patient deteriorated significantly. The postprocedural ECG showed a bizarre, extremely wide surface QRS complex (360 ms), termed as homologous ventricular separation. The pronounced dyssynchrony of the ventricle was corrected by an upgrade to cardiac resynchronization therapy with defibrillation (CRT-D). As a result, the symptoms of the patient improved significantly. The width of the intrinsic QRS complex was not recovered during an 18-month follow-up.Conclusion: Homologous ventricular separation is a rare arrhythmia, manifested as two separated QRS waves. This case report demonstrates, for the first time, that homologous ventricular separation may occur after extensive substrate modification of scar-related VT. CRT-D can correct the dyssynchronous ventricle caused by homologous ventricular separation.

Preparation of Zinc Oxide Nanomaterial and Research and Development of Antibacterial Property

Children using environmentally unfriendly furniture are more likely to suffer from allergic rhinitis, respiratory infections, and leukemia. The green design of children’s furniture must consider anti-formaldehyde, deodorant, antibacterial, and antiviral factors. This paper prepares a zinc oxide (ZnO) nanomaterial for children’s furniture, and researches and develops the antibacterial property of the nanomaterial. The main contents include the synthesis method and preparation process, material morphology and structure characterization, and antibacterial performance testing. The practical substrate modification of the material was realized by pre-depositing polydopamine particles. In this way, the ZnO nanomaterial could apply to a wider range of children’s furniture, become more durable, and realize efficient multi-mechanism synergistic sterilization. Experimental results show that the prepared material has a good antibacterial property.

Safety of high power and short duration ablation (70 watts over 5–7 seconds) in patients with persistent atrial fibrillation undergoing pulmonary vein isolation and additional substrate modification

Background In paroxysmal atrial fibrillation (AF), pulmonary vein isolation using HPSD has shown a promising success rate compared to ablation using conventional power settings, as well as a significant reduction in procedural and ablation time. In persistent atrial fibrillation, left atrial substrate modification seems to be a promising additional ablation approach besides pulmonary vein isolation (PVI). However, results after additional substrate ablation are not consistently positive, which may be related to non-transmural lesions and tissue oedema. An extended time of the procedure may also influence safety. Recent publications showed that HPSD ablation provides more sufficient lesions due to acute cell necrosis instead of cell oedema. Purpose The aim of this study is to evaluate the safety of HPSD ablation in patients undergoing ablation of persistent atrial fibrillation with PVI and additional substrate modification. Methods We studied and compared n=300 patients from our register undergoing the first ablation of persistent atrial fibrillation with HPSD settings (n=150) between May 2018 and January 2019 and standard settings (n=150) between July 2017 and January 2018. Patients were followed up for three months to report procedure-related adverse events. In all patients, a modified stepwise approach using PVI followed by electrogram-guided substrate modification and linear-ablation, if necessary, was performed. A HPSD ablation was performed with 70 watts with a maximum duration of 5–7 seconds. Catheter irrigation was set to 20 ml/min using the Flexability™ ablation catheter and the Ampere™ generator. The patients were compared with a historical cohort that underwent PVI using a conventional power protocol with 30–40 watts over 20–40 seconds, using the same ablation catheter. A transthoracic echocardiogram was performed in all patients after the ablation-procedure and on the following day. Duplex sonography or clinical control were performed to assess groin complications. Results Baseline characteristics and procedural data are shown in table 1. No significant difference in the complication rates in both groups was observed by a significant procedure-time reduction in HPSD-Group (2:13h vs 2:31h p&lt;0,001) and overall low risk of the procedure. No deaths, thromboembolic complications or atrioesophageal fistula were registered. Complication rates with statistical relevancy are shown in table 2. Conclusion Complex ablation using PVI and additional substrate modification in persistent atrial fibrillation using HPSD seems to be equally as safe regarding procedure-related outcomes as standard power settings ablation and can significantly reduce the time of the overall procedure. FUNDunding Acknowledgement Type of funding sources: None.

Electrophysiological predictors of ventricular tachycardia recurrence in patients with structural heart disease after combined endo-epicardial substrate catheter ablation

Background Although there is a tremendous improvement in mapping and ablation techniques over the last decades, the recurrence rate of ventricular tachycardia (VT) in patients with structural heart diseases following endo-epicardial catheter ablation remains high. Purpose To determine predictors of VT recurrence in patients with structural heart disease after combined endo-epicardial radiofrequency (RF) VT ablation. Methods This prospective single-center study included 39 patients (34 men and 5 women, mean age 49.6±16.0 years), who underwent endo-epicardial mapping and ablation of the VT substrate. Etiology of structural heart diseases included: previous myocardial infarction (n=15); non-ischemic cardiomyopathy (n=24: 15 – arrhythmogenic right ventricular cardiomyopathy (ARVC), 6 – myocarditis, 3 – unspecified). First-line epicardial access was performed in 16 patients, as a second approach – in 23 subjects. We evaluated total ventricular myocardial areas, epi- and endocardial areas with bipolar low voltage (&lt;1.5mV), scar area (bipolar &lt;0.5mV), and unipolar low voltage (&lt;5.0mV) and transient (&lt;8.0mV) areas; areas of late potential registration were evaluated. Ratios of transient, low amplite and late-potential areas were calculated for endo- and epicardial surfaces, bipolar and unipolar maps. The following procedural electrophysiology characteristics were considered: inducibility of clinical VT, the number and morphology of induced VT, QRS width on sinus rhythm and VT, tachycardia cycle length, pseudo-delta wave extant and width, internal activation time, intrisicoud deflection time, and RS length. Clinical data such as echocardiography parameters, comorbidity and antiarrhythmic drug therapy were also taken into account. VT recurrences were documented using ICD/CRT-D interrogation, event ECG monitoring. Follow-up included mandatory visits at 6 and 12 months and unscheduled visits. Results Epicardial late potentials were registered in 69% of cases before ablation. Epicardial RF applications were delivered in 67% of patients; while only endocardial RF applications (including cases with intended epicardial substrate modification by endocardial ablation) were present in 28% cases. Non-inducibility of any VT plus abatement of local abnormal electrical activity was achieved in 32 (82%) of cases. The ratio epi/endo bipolar areas &lt;0.5mV was much higher in patients with vs without VT recurrence at 6 months (4.3 (IQR: 2.5; 8.2) vs 0.75 (IQR:0.4; 1.6), P=0.001). A strong negative correlation was found between the induced VT cycle length and the ratio epi/endo bipolar areas &lt;0.5mV: the shorter induced VT cycle length -the larger the area of the epicardial low voltage area (r=−0,52). Conclusion Regardless of epicardial substrate modification, patients with a larger epicardial low voltage area are more likely to have VT recurrence at 6 months after index ablation. A shorter induced VT cycle length is associated with a larger epicardial low-voltage area. FUNDunding Acknowledgement Type of funding sources: None.

Substrate Modification in Catheter Treatment of Atrial Fibrillation

According to modern concepts, atrial fibrillation (AF) occurs when there are triggers affecting the prepared substrate (atrial myocardium) in the presence of modulating factors that contribute to the occurrence of arrhythmia. Catheter treatment of AF has been most successfully developed in the field of affecting triggers (since late 1990s, the most successful was a technique of isolation of pulmonary veins which are the main source of trigger impulses in AF). Over the past two decades, various techniques have also been proposed for influencing the fibrous substrate. The aim. To analyze the most advanced techniques for influencing the fibrous substrate during catheter treatment of AF. Materials and methods. We analyzed the experience of leading electrophysiological centers in this field. Discussion. Modern studies contain various electrophysiological criteria of fibrous myocardium. However, the signal amplitude less than 0.5 mV is considered borderline between healthy and damaged tissues by most authors. The task of the catheter action on the myocardium is to separate the fibrously altered tissue and intact tissue. This can be achieved by isolating the area of fibrosis or by transforming it into a scar tissue incapable of arrhythmogenesis. It should be noted that both methods are associated with the same frequency of the absence of AF paroxysms, which can be regarded as confirmation of the advisability of influencing the substrate. The most important is that exposure of the substrate can significantly reduce the recurrence rate of AF compared to that when the ablation procedure is limited to isolation of the pulmonary veins. Conclusions. Modern methods of influencing the areas of fibrosis in the atria can significantly improve the results of catheter treatment of AF.

The role of brain natriuretic peptide in atrial fibrillation: a substudy of the Substrate Modification with Aggressive Blood Pressure Control for Atrial Fibrillation (SMAC-AF) trial

Background Catheter ablation is an established therapy for atrial fibrillation but is limited by recurrence; efforts have been made to identify biomarkers that predict recurrence. We investigated the effect of baseline NT-proBNP on AF recurrence following catheter ablation in patients randomized to aggressive (< 120/80 mmHg) or standard blood pressure management (< 140/90 mmHg) in the Substrate Modification with Aggressive Blood Pressure Control trial (SMAC-AF). Methods The SMAC-AF study included 173 patients resistant or intolerant to at least one class I or III antiarrhythmic drug. We studied the effect of baseline NT-proBNP on the primary outcome of AF recurrence > 3 months post-ablation. Results Of the 173 patients, 88 were randomized to the aggressive cohort, and 85 into the standard group. The primary outcome occurred in 61.4% of those in the aggressive arm, versus 61.2% in the standard arm. In the aggressive group, logNT-proBNP predicted recurrence (HR 1.28, p = 0.04, adjusted HR 1.43, p = 0.03), while in the standard cohort, it did not (HR 0.94, p = 0.62, adjusted HR 0.83, p = 0.22). NT-proBNP ≥ 280 pg/mL also predicted occurrence in the aggressive (HR 1.98, p = 0.02) but not the standard cohort (HR 1.00, p = 1.00). Conclusion We conclude that pre-ablation NT-proBNP may be useful in predicting recurrence in hypertensive patients and identifying patients who benefit from aggressive blood control and upstream therapies. Trial registration: NCT00438113, registered February 21, 2007.