High-density mapping in catheter ablation for persistent atrial fibrillation

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott Laboratories

Background

Pulmonary vein isolation (PVI) is an established treatment option for persistent atrial fibrillation (PersAF). Corresponding long-term success rates remain modest however, advancements in high-density (HD) mapping may better identify substrates. The HD grid-style mapping catheter (HD Grid) allows for simultaneous analysis of adjacent orthogonal bipolar signals that may assist in ablation strategy decisions to achieve favorable outcomes in treating PersAF.

Objective

This was a prospective, multi-center, observational study to quantify and characterize the use of a market-released HD mapping catheter in PersAF subjects.

Methods

HD Grid was used in PersAF subjects undergoing radiofrequency (RF) ablation across 25 sites to gather data regarding safety, mapping efficiency and quality, ablation strategies, and procedural outcomes.

Results

334 PersAF subjects (average age: 64.2 years; 76% male) were enrolled in this study. Types of maps generated included peak-to-peak voltage (78%; 322/413), local activation time (LAT) (11.4%; 47/413), and complex fractionated electrogram (CFE) mean (7.7%; 32/413). Median total mapping points collected and used were 8428.0 (IQR 4845.0-13366.0) and 2099.0 (IQR 1219.0-2947.0), respectively, in a median of 11.0 (IQR 7.3-16.0) minutes per map. Low voltage, scar/fibrosis, and CFE were searched for in 90.4% (302/334), 53.6% (179/334), and 15.9% (53/334) of subjects, respectively. A PVI approach was used in 93.1% of all ablation procedures and 34.1% (114/334) of subjects received PVI plus additional lesions. HD Grid identified signals of interest not identified by the ablation catheter in 80.4% (205/255) of subjects. The total procedure time was 134.3 ± 51.3 minutes with a fluoroscopy time of 14.5 ± 11.3 minutes and RF ablation time of 32.4 ± 29.6 minutes. Of the subjects in atrial fibrillation (AF) (59.6%; 199/334), AF was terminated in 80.4% (160/199). 87.4% (173/198) of subjects were free from recurrent atrial arrhythmias as detected by 48-hour Holter monitoring at 12 months. 13.8% (46/334) of subjects experienced any adverse event through 12 months including 1 death unrelated to the procedure and 1 event deemed related to HD Grid by the investigator.

Conclusion

This study demonstrated the use of the HD Grid mapping catheter to create detailed maps and to guide ablation strategies to treat PersAF while maintaining an adequate safety profile.

Simultaneous orthogonal bipole mapping compared to conventional electrode configurations and impact on ablation strategies: results from a real world observational study

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

3D mapping systems are pivotal to identify low voltage areas and to define ablation strategies. In this context, high-density multipolar mapping catheters with varying electrode configurations are used for accurate myocardial substrate definition. High density mapping using a grid shaped catheter allows for use of simultaneous analysis of adjacent orthogonal bipolar signals that may assist in more accurate substrate characterization and ablation strategy decisions.

Purpose

This was a prospective, multicenter observational study to characterize the utility of electroanatomical mapping with a high density grid-style mapping catheter (HD Grid) in subjects undergoing catheter ablation for persistent atrial fibrillation (PersAF) or ventricular tachycardia (VT) in real-world clinical settings.

Methods

Mapping was performed with the HD Grid catheter to generate high-density maps of cardiac chambers in order to assess the potential influence of the simultaneous orthogonal bipole configuration on PersAF and VT ablation strategies. Differences in substrate identification between simultaneous orthogonal bipole configuration and standard along-the-spline electrode configuration, and potential effects on ablation strategies were investigated.

Results

During the study period (January 2019 through April 2020), 367 subjects underwent catheter ablation for PersAF (N = 333, average age 64.1yr, 75% male) or VT (N = 34, average age = 64.3yr, 85.3% male).

In total, 494 maps were generated to treat patients undergoing PersAF ablation and 57 to treat patients undergoing VT ablation. Compared to standard along-the-spline configuration, mapping with the simultaneous orthogonal bipole configuration showed differences in 57.8% (178/308) of maps generated, with the greatest difference noticed in surface area of low voltage (62.9%) and location of low voltage (55.6%).

In comparisons performed live during the procedure (n = 50), simultaneous orthogonal bipole configuration assisted in identification of ablation targets in 70.0% of cases, changing the ablation strategy compared to that identified with along-the-spline configuration in 34.3%.

In comparisons performed retrospectively after the procedure (n = 258), the ablation strategy identified with simultaneous orthogonal bipole configuration differed from along-the-spline configuration in 21.7% of maps. Even compared to a higher-density electrode configuration using all-bipoles rather than along-the-spline bipoles, simultaneous orthogonal bipole configuration identified differences in 57.1% of maps.

Conclusion

The HD grid catheter combined with simultaneous orthogonal bipole configuration can define myocardial substrate more accurately compared to standard along-the-spline configuration. The difference in substrate identification has potential impact on ablation strategy. Further clinical trials are needed to elucidate the role of orthogonal bipole configuration mapping and improved ablation success rates.

Impact of high density mapping using a grid shaped catheter with orthogonal signal analysis on ventricular tachycardia ablation strategy

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

Ventricular tachycardia (VT) in patients with structural heart disease (SHD) is related to scar and slow conduction areas. Substrate-based ablation has become the gold standard treatment in patients with SHD-related refractory VT. A new high-density grid shaped catheter that allows simultaneous analysis of adjacent orthogonal bipolar signals can allow better understanding of these slow conduction areas with the potential to improve ablation results.

Purpose

This was a prospective, multicenter observational study to characterize the utility of electroanatomical mapping with a high density grid-style mapping catheter (HD Grid) in subjects undergoing catheter ablation for ventricular tachycardia (VT) in real-world clinical settings.

Methods

During the study period, patients who underwent VT ablation using the HD Grid catheter as the primary mapping catheter were included. Comparisons both during the procedure and retrospectively were performed between conventional electrode configuration maps and simultaneous orthogonal bipole electrode configuration maps. The influence of these different configurations on ablation strategy was analyzed.

Results

  During study period (January 2019 – April 2020) 57 maps were performed in 34 VT subjects (average age: 64.3yr, male: 85.3%, ischemic cardiomyopathy: 70.6%). The left ventricle was mapped in 94.1% of subjects, including left ventricular outflow tract and papillary muscles in 20.6% and 8.8% respectively, reporting minimal or no ectopic beats in 97.1% of the subjects. The total number of mapping points collected was 14172.0 ± 15174.8 in 24.3 ± 17.9 min per map.

Simultaneous orthogonal bipole mapping identified differences in 67.6% of maps compared to linear along-the-spline electrode configurations. The differences consisted mainly in the surface area (92%) and location of low voltage (40%). When compared during the procedure, simultaneous orthogonal bipole mapping was used to identify ablation strategy in 100% of cases. When compared to a standard along-the-spline configuration retrospectively, the ablation strategy identified with simultaneous orthogonal bipoles was different in 30.1% of cases.  The ablation strategy used in these subjects was mainly substrate ablation (late potentials and low voltage areas in scar regions) with an acute success rate of 97.1%.

Conclusions

The use of the HD Grid catheter with the ability to analyze orthogonal signals is feasible and has the potential to change the ablation strategy in one third of VT patients with a high acute success rate.

Clinical and immune responses of tuberculosis patients treated with low-dose IL-2 and multidrug therapy

The immune response to infection with M. tuberculosis depends on cytokine activation of effector cells. We therefore conducted a pilot study of recombinant human interleukin-2 (rhuIL-2) as an adjunct to multidrug therapy (MDT) to evaluate the safety of this approach and to determine whether IL-2 can enhance the cellular immune response in patients with pulmonary tuberculosis (TB). Patients included in this study presented with a wide range of extent and duration of infection, and were grouped into three categories for data analysis: (1) patients with newly diagnosed, acute-stage TB who were just beginning MDT; (2) patients who had received a minimum of 45 days MDT before the start of the study and who had responded to treatment; and (3) patients with multidrug-resistant (MDR) TB who had been on MDT for at least seven months without apparent beneficial clinical response. Twenty patients received 30 days of twice-daily intradermal injections of 12.5 micrograms of IL-2. Patients from all three groups showed improvement of clinical symptoms over the 30-day period of treatment with IL-2 and MDT. Results of direct smear for acid fast bacilli (AFB) demonstrated conversion to sputum-negative following IL-2 and MDT treatment in all newly diagnosed patients and in 5/7 MDR TB patients. (The size of the skin test response to purified protein derivative (PPD) of tuberculin increased during the 30-day IL-2 adjunctive therapy in newly diagnosed patients, but decreased or disappeared in the other two groups of treated patients.) Assays in vitro for phenotype distribution, natural killer (NK) cell activity, frequency of cells proliferating in response to exogenous IL-2, and antigen-induced blastogenesis demonstrated systemic responses to intradermally administered rhuIL-2. Levels of interferon-gamma (IFN-gamma) in plasma, peripheral blood mononuclear cell (PBMC) IFN-gamma mRNA and IFN-gamma mRNA in biopsy of site of skin test response to purified protein derivative (PPD) were highest in those patients with the most acute symptoms at the beginning of the study, and decreased during rhuIL-2 and MDT. IL-2 immunotherapy did not modify levels of mRNA expression for other cytokines. Patients receiving IL-2 did not experience clinical deterioration or significant side effects. These results suggest that IL-2 administration in combination with conventional MDT is safe and may potentiate the antimicrobial cellular immune response to TB.

Cellular immunity in tuberculous pleural effusions: evidence of spontaneous lymphocyte proliferation and antigen-specific accelerated responses to purified protein derivative (PPD)

The kinetics of in vitro cellular proliferation against a PPD of Mycobacterium tuberculosis or streptococcal antigen (streptokinase-streptodornase) was evaluated in pleural fluid and peripheral blood mononuclear cells (PBMC) from patients with tuberculous and non-tuberculous pleuritis. The peak proliferative response to PPD by mononuclear cells from pleural fluid occurred earlier (day 3) in 65% of patients with tuberculosis, a finding not seen in non-tuberculous effusions. Spontaneous lymphocyte proliferation of both peripheral blood lymphocytes and pleural effusion lymphocytes was frequently observed, irrespective of etiology. However, 20 of 21 tuberculous patients manifesting spontaneous lymphocyte proliferation had accelerated kinetics of proliferation to PPD, which was antigen-specific. These results suggest that spontaneous lymphocyte proliferation occurs as a response to antigen stimulation at the site of disease, and is not a non-specific response to inflammation. Furthermore, enhanced reactivity against mycobacterial antigen, manifested by accelerated kinetics of proliferation, has diagnostic potential in patients with pleural effusions.

Evidence for in vivo generation of cytotoxic T cells. PPD-stimulated lymphocytes from tuberculous pleural effusions demonstrate enhanced cytotoxicity with accelerated kinetics of induction

Mycobacterium tuberculosis is a bacterial pathogen capable of survival and replication within human macrophages. Cytotoxic T cells are thought to be important for the eradication of infected macrophages. To test this hypothesis, pleural effusion lymphocytes from patients with tuberculous pleuritis were stimulated in vitro with PPD, and proliferation and cytotoxicity were assessed by thymidine incorporation and chromium release, respectively. The level and kinetics of generation of antigen-specific cytotoxicity were measured and compared with those in autologous peripheral blood, control peripheral blood, and nontuberculous effusions. Both proliferation and cytotoxicity in tuberculous pleural effusions were augmented and accelerated in comparison to autologous or control peripheral blood. By contrast, low levels of cytotoxicity were observed in nontuberculous effusions, without evidence of accelerated kinetics. Cell subset fractionation by panning indicated that the cytotoxicity was mediated by CD4+ cells. The accelerated kinetics of induction of PPD-specific cytotoxic T cells demonstrated here suggests reactivation of in vivo generated cytotoxic T cells. These findings provide evidence that cytotoxic T cells are induced at the site of pathology in vivo and suggest that these cells play an important role in protection in vivo against infection with tuberculosis.

Compartmentalization of the cellular immune response to the recombinant 65 kDa protein of Mycobacterium bovis BCG in patients with tuberculous pleuritis

The recombinant 65 kDa mycobacterial protein of M. bovis BCG has been shown to be immunodominant in mice immunized with M. tuberculosis. Little is known about reactivity to this antigen in patients with tuberculous pleuritis. In this study therefore, pleural effusion and autologous peripheral blood lymphocytes obtained from patients with tuberculous and nontuberculous pleuritis were stimulated in-vitro with the recombinant 65 kDa antigen. Proliferation was assessed by 3[H] thymidine incorporation. In addition, pleural effusion lymphocytes were activated in vitro with the 65 kDa antigen and tested for cytotoxic activity in 15-hr chromium-release assays. Pleural effusion lymphocytes obtained from a high percentage (56%) of patients with tuberculous pleuritis showed significant proliferative responses to the 65 kDa antigen, while the response in autologous peripheral blood lymphocytes was significantly lower. By contrast, pleural effusion lymphocytes obtained from patients with nontuberculous effusions were not reactive to the 65 kDa antigen. In addition, 65 kDa stimulated pleural effusion lymphocytes obtained from patients with tuberculous effusions showed antigen-specific lysis of autologous targets pulsed with the 65 kDa antigen. These results indicate compartmentalization of the immune response to the 65 kDa antigen and, in addition, provide evidence for in vivo involvement of this antigen in the immune response to M. tuberculosis.

Bacteremia after injection of esophageal varices

Elective sclerotherapy for esophageal varices produces bacteremia in 4% to 53% of patients. The clinical importance of this phenomenon is uncertain. This study was undertaken to re-assess the incidence and clinical relevance of post-sclerotherapy bacteremia. Blood cultures were taken prior to and at 5 min and 4 h after endoscopy in 50 patients for whom sclerotherapy was planned. In the 41 patients in whom varices were injected, positive cultures were obtained 5 min after sclerotherapy in only 4 patients (10%) and all but 1 patient had other possible causes of bacteremia. After 4 h, all blood cultures were sterile. No infective complications were identified. Bacteremia appears to be an infrequent and transient event after elective sclerotherapy. Only patients with prosthetic heart valves or endocardial abnormalities require antibiotic prophylaxis.