Julian W.E. Jarman

Clinical experience of entirely subcutaneous implantable cardioverter–defibrillators in children and adults: cause for caution

AIMS This paper describes our clinical experience of using an entirely subcutaneous implantable cardioverter-defibrillator (S-ICD) in children and adults. Maintaining lead integrity and long-term vascular access are critical challenges of ICD therapy, especially in younger patients. The S-ICD has considerable theoretical advantages in selected patients without pacing indications, particularly children and young adults. Although sensing in an S-ICD may be influenced by age, pathology, and posture, there are currently few published data on clinical sensing performance outside the setting of intra-operative testing or in younger patients. METHODS AND RESULTS Patients were selected by a multi-disciplinary team on clinical grounds for S-ICD implantation from a broad population at risk of sudden arrhythmic death. Sixteen patients underwent implantation [median age 20 years (range 10-48 years)]. Twelve had primary electrical disease and four had congenital structural heart disease. There were no operative complications, and ventricular fibrillation (VF) induction testing was successful in all cases. During median follow-up of 9 months (range 3-15 months), three children required re-operation. Eighteen clinical shocks were delivered in six patients. Ten shocks in four patients were inappropriate due to T-wave over-sensing. Within the eight shocks for ventricular arrhythmia, three were delivered for VF, among which two had delays in detection with time to therapy of 24 and 27 s. CONCLUSION The S-ICD is an important new option for some patients. However, these data give cause for caution in light of the limited published data regarding clinical sensing capabilities, particularly among younger patients.

United Kingdom national experience of entirely subcutaneous implantable cardioverter-defibrillator technology: important lessons to learn

AIMS The aim of this study was to describe the early phase United Kingdom (UK) clinical experience with a novel entirely subcutaneous implantable cardioverter-defibrillator (S-ICD). METHODS AND RESULTS A questionnaire was sent to all UK hospitals implanting S-ICDs. Nineteen of 25 (76%) hospitals responded with the details of 111 implanted patients [median 5/hospital (range 1-18)]. Mean duration of follow-up was 12.7 ± 7.1 months. Median patient age was 33 years (range 10-87 years). Underlying pathology was primary electrical disease in 43%, congenital heart disease 12%, hypertrophic cardiomyopathy 20%, ischaemic cardiomyopathy 14%, idiopathic dilated cardiomyopathy 5%, and other cardiomyopathies 7% patients. Nineteen (17%) patients required 20 re-operations, including permanent device explantation in 10 (9%). Twenty-four appropriate shocks were delivered in 13 (12%) patients, including 10 for ventricular fibrillation. One patient suffered arrhythmic death, but there were no failures to detect or terminate ventricular arrhythmias above the programmed detection rate. Fifty-one inappropriate shocks were delivered in 17 (15%) patients. Forty-one (80%) were for T-wave over-sensing and 1 (2%) for atrial flutter-wave over-sensing. The 11 patients who received inappropriate shocks due to T-wave over-sensing were significantly younger than patients who did not (24 ± 10 vs. 37 ± 19 years; P = 0.02). CONCLUSION The S-ICD is an important innovation in ICD technology. However, these data indicate that adverse event rates are significant during early clinical adoption. Important lessons in patient selection, implant technique, and device programming can be learnt from this experience.

Outcomes of defibrillator therapy in catecholaminergic polymorphic ventricular tachycardia

BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome characterized by adrenergically induced ventricular arrhythmias in patients with structurally normal hearts. Initiating triggered arrhythmias, such as bidirectional ventricular tachycardia, often degenerate into reentrant arrhythmias, such as ventricular fibrillation (VF). OBJECTIVE To determine whether the effectiveness of implantable cardioverter-defibrillator (ICD) shocks is dependent on rhythm type. METHODS It is a retrospective study of patients with CPVT who had undergone ICD implantation. Thirteen patients received ICDs (median age 15 years; range 9-43 years): 7 of 13 (54%) for cardiac arrest and 6 of 13 (46%) for syncope despite drug therapy. The median follow-up duration was 4.0 years (range 1.7-19.9 years). Nineteen reinterventions occurred, excluding generator replacements. Ten patients received 96 shocks (median 4 shocks; range 1-30 shocks). Eighty-seven shock electrograms were reviewed. Sixty-three (72%) shocks were appropriate, and 24 (28%) were inappropriate (T-wave oversensing 7 [29%], supraventricular arrhythmia 16 [67%], after self-terminating VF 1 [4%]). RESULTS Among appropriate shocks, 20 (32%) were effective in terminating sustained arrhythmia and 43 (68%) were ineffective. Shocks delivered to triggered arrhythmias nearly always failed (1 of 40 [3%] effective), while shocks delivered to VF were usually successful (19 of 23 [83%] effective; P < .001). Four patients received 17 appropriate antitachycardia pacing therapies for ventricular tachycardia: only 2 (12%) were effective. No patient died. CONCLUSIONS The effectiveness of ICD shock therapy in CPVT depends on the mechanism of the rhythm treated. Shocks delivered to initiating triggered arrhythmias nearly always fail, whereas those for subsequent VF are usually effective. ICD programming in these patients is exceptionally challenging.

Spatiotemporal Behavior of High Dominant Frequency During Paroxysmal and Persistent Atrial Fibrillation in the Human Left Atrium

Background— Sites of high dominant frequency (DFpeak) are thought to indicate the location of drivers of atrial fibrillation (AF), but characterization of their spatiotemporal distribution and stability, critical to their relevance as targets for catheter ablation, requires simultaneous global mapping of the left atrium. Methods and Results— Noncontact electrograms recorded simultaneously from 256 left atrial sites during spontaneous AF were analyzed. After subtraction of the ventricular component, fast Fourier transform identified the DF at each site. Focal areas of DFpeak were defined as those having a DF >20% above all neighboring sites. Twenty-four patients with spontaneous AF (11 paroxysmal and 13 persistent) were studied. In paroxysmal AF, sites of DFpeak (mean DF, 11.6±2.9 Hz) were observed in 100% of patients (present during 65% of the mapping period). In contrast, DFpeak was detected in only 31% of patients with persistent AF (P<0.001) and for only 5% of the mapping period (P<0.001). In both groups, locations of DFpeak varied widely in both consecutive and separated segments of AF (&kgr; coefficient range, -0.07–0.22). Activation sequences around sites of DFpeak did not demonstrate centrifugal activation that would be expected from focal drivers. Conclusions— Focal areas of high DF are more frequent in paroxysmal than persistent AF, are spatiotemporally unstable, are not the source of centrifugal activation, and are not, therefore, indicative of fixed drivers of AF. In the absence of spatiotemporal stability, the success of ablation at sites of DFpeak cannot be explained by elimination of fixed drivers.

Relationship between contact force sensing technology and medium-term outcome of atrial fibrillation ablation: a multicenter study of 600 patients.

Contact force sensing (CFS) technology improves acute pulmonary vein isolation durability; however, its impact on the clinical outcome of ablating atrial fibrillation (AF) is unknown.

Left Atrial Appendage Electrical Isolation and Concomitant Device Occlusion to Treat Persistent Atrial Fibrillation: A First-in-Human Safety, Feasibility, and Efficacy Study.

Background—Left atrial appendage (LAA) electric isolation is reported to improve persistent atrial fibrillation (AF) ablation outcomes. However, loss of LAA mechanical function may increase thromboembolic risk. Concomitant LAA electric isolation and occlusion as part of conventional AF ablation has never been tested in humans. We therefore evaluated the feasibility, safety, and efficacy of LAA electric isolation and occlusion in patients undergoing long-standing persistent AF ablation. Methods and Results—Patients with long-standing persistent AF (age, 68±7 years; left atrium diameter, 46±3 mm; and AF duration, 25±15 months) underwent AF ablation, LAA electric isolation, and occlusion. Outcomes were compared with a balanced (1:2 ratio) control group who had AF ablation alone. Among 22 patients who underwent ablation, LAA electric isolation was possible in 20. Intraprocedural LAA reconnection occurred in 17 of 20 (85%) patients, predominantly at anterior and superior locations. All were reisolated. LAA occlusion was successful in all 20 patients. There were no major periprocedural complications. Imaging at 45 days and 9 months confirmed satisfactory device position and excluded pericardial effusion. One of twenty (5%) patients had a gap of ≥5 mm requiring anticoagulation. Nineteen of twenty (95%) patients stopped warfarin at 3 months. Without antiarrhythmic drugs, freedom from AF at 12 months after a single procedure was significantly higher in the study group (19/20, 95%) than in the control group (25/40, 63%), P=0.036. Freedom from atrial arrhythmias was demonstrated in 12 of 20 (60%) and 18 of 20 (90%) patients after 1 and ⩽2 procedures (mean, 1.3), respectively. Conclusions—Persistent AF ablation, LAA electric isolation, and mechanical occlusion can be performed concomitantly. This technique may improve the success of persistent AF ablation while obviating the need for chronic anticoagulation. Clinical Trial Registration—URL: https://clinicaltrials.gov. Unique identifier: NCT02028130.

Predicting atrial fibrillation ablation outcome: The CAAP-AF score.

BACKGROUND Patients with a variety of clinical presentations undergo atrial fibrillation (AF) ablation. Long-term ablation success rates can vary considerably. OBJECTIVE The purpose of this study was to develop a clinical scoring system to predict long-term freedom from AF after ablation. METHODS We retrospectively derived the scoring system on a development cohort (DC) of 1125 patients undergoing AF ablation and tested it prospectively in a test cohort (TC) of 937 patients undergoing AF ablation. RESULTS The demographics of the DC patients were as follows: age 62.3 ± 10.3 years, male sex 801 (71.2%), left atrial size 4.30 ± 0.69 cm, paroxysmal AF 348 (30.9%), number of drugs failed 1.3 ± 1.1, hypertension 525 (46.7%), diabetes 100 (8.9%), prior stroke/transient ischemic attack 78 (6.9%), prior cardioversion 528 (46.9%), and CHADS2 score 0.87 ± 0.97. Multivariate analysis showed 6 independent variables predicting freedom from AF after final ablation: coronary artery disease (P = .021), atrial diameter (P = .0003), age (P = .004), persistent or long-standing AF (P < .0001), number of antiarrhythmic drugs failed (P < .0001), and female sex (P = .0001). We created a scoring system (CAAP-AF) using these 6 variables, with scores ranging from 0 to 13 points. The 2-year AF-free rates by CAAP-AF scores were as follows: 0 = 100%, 1 = 95.7%, 2 = 96.3%, 3 = 83.1%, 4 = 85.5%, 5 = 79.9%, 6 = 76.1%, 7 = 63.4%, 8 = 51.1%, 9 = 53.6%, and ≥10 = 29.1%. Ablation success decreased as CAAP-AF scores increased (P < .0001). The CAAP-AF score also predicted freedom from AF in the TC. The 2-year Kaplan-Meier AF-free rates by CAAP-AF scores were as follows: 0 = 100%, 1 = 87.0%, 2 = 89.0%, 3 = 91.6%, 4 = 90.5%, 5 = 84.4%, 6 = 70.1%, 7 = 71.0%, 8 = 60.7%, 9 = 68.9%, and ≥10 = 51.3%. As CAAP-AF scores increased, 2-year freedom from AF in the TC decreased (P < .0001). CONCLUSION An easily determined clinical scoring system was derived retrospectively and applied prospectively. The CAAP-AF score predicted freedom from AF after ablation in both a DC and a TC of patients undergoing AF ablation. The CAAP-AF score provides a realistic AF ablation outcome expectation for individual patients.

Biatrial linear ablation in sustained nonpermanent AF: Results of the substrate modification with ablation and antiarrhythmic drugs in nonpermanent atrial fibrillation (SMAN-PAF) trial

BACKGROUND More advanced atrial fibrillation (AF) is associated with lower success rates after pulmonary vein isolation (PVI), and the optimal ablation strategy is uncertain. OBJECTIVES To assess the impact of additional linear ablation (lines) compared to PVI alone. METHODS In this multicenter randomized controlled trial, 122 patients (mean age 61.9 ± 10.5 years; left atrial diameter 43 ± 6 mm) with persistent AF (PeAF) or sustained (>12 hours) paroxysmal AF (SusPAF) with risk factors for atrial substrate were included and followed up for 12 months. Patients were randomized to PVI-only or PVI + lines (left atrial roof line, mitral isthmus line, and tricuspid isthmus line) group. Holter monitoring was performed at 3, 6, and 12 months and according to symptoms. The primary outcome was atrial tachyarrhythmia recurrence lasting ≥30 seconds. RESULTS Baseline characteristics were comparable between groups; 61% had PeAF and 39% SusPAF. Successful PVI was achieved for 98% of pulmonary veins, and bidirectional block was obtained in 90% of lines. The primary end point occurred in 38% of the PVI + lines group and 32% of the PVI-only group (P = .50), which was consistent in both PeAF (36% vs 28%; P = .45) and SusPAF (42% vs 39%; P = .86). Compared with the PVI-only group, the PVI + lines group had higher procedure duration (209 ± 52 minutes vs 172 ± 44 minutes; P < .001), ablation time (4352 ± 1084 seconds vs 2503 ± 1061 seconds; P < .001), and radiation exposure (Dose-area product 3992 ± 6496 Gy·cm(2) vs 2106 ± 1679 Gy·cm(2); P = .03). Quality of life (disease-specific Atrial Fibrillation Effect on Quality of Life questionnaire and mental component scale of the Short Form 36 Health Survey) improved significantly during the study but did not differ between groups. CONCLUSION Adding lines to wide antral PVI in substrate-based AF requires significantly more ablation, increases procedure duration and radiation dose, but provides no additional clinical benefit.

Outcomes and costs of left atrial appendage closure from randomized controlled trial and real-world experience relative to oral anticoagulation

AIMS The aim of this study was to analyse randomized controlled study and real-world outcomes of patients with non-valvular atrial fibrillation (NVAF) undergoing left atrial appendage closure (LAAC) with the Watchman device and to compare costs with available antithrombotic therapies. METHODS AND RESULTS Registry data of LAAC from two centres were prospectively collected from 110 patients with NVAF at risk of stroke, suitable and unsuitable for long-term anticoagulation (age 71.3 ± 9.2 years, CHADS2 2.8 ± 1.2, CHA2DS2-VASc 4.5 ± 1.6, and HAS-BLED 3.8 ± 1.1). Outcomes from PROTECT AF and registry study LAAC were compared with warfarin, dabigatran, rivaroxaban, apixaban, aspirin, and no treatment using a network meta-analysis. Costs were estimated over a 10-year horizon. Uncertainty was assessed using sensitivity analyses. The procedural success rate was 92% (103/112). Follow-up was 24.1 ± 4.6 months, during which annual rates of stroke, major bleeding, and all-cause mortality were 0.9% (2/223 patient-years), 0.9% (2/223 patient-years), and 1.8% (4/223 patient-years), respectively. Anticoagulant therapy was successfully stopped in 91.2% (93/102) of implanted patients by 12 months. Registry study LAAC stroke and major bleeding rates were significantly lower than PROTECT AF results: mean absolute difference of stroke, 0.89% (P = 0.02) and major bleeding, 5.48% (P < 0.001). Left atrial appendage closure achieved cost parity between 4.9 years vs. dabigatran 110 mg and 8.4 years vs. warfarin. At 10 years, LAAC was cost-saving against all therapies (range £1162-£7194). CONCLUSION Left atrial appendage closure in NVAF in a real-world setting may result in lower stroke and major bleeding rates than reported in LAAC clinical trials. Left atrial appendage closure in both settings achieves cost parity in a relatively short period of time and may offer substantial savings compared with current therapies. Savings are most pronounced among higher risk patients and those unsuitable for anticoagulation.

Organizational Index Mapping to Identify Focal Sources During Persistent Atrial Fibrillation

Localized rotors have been implicated in the mechanism of persistent atrial fibrillation (AF). Although regions of highest dominant frequency (DF) on spectral analysis of the left atrium (LA) have been said to identify rotors, other mechanisms such as wavefront collisions will sporadically also generate an inconsistent distribution of high DF. We hypothesized that if drivers of AF were present, their distinctive spectral characteristics would result more from their temporal stability than their high frequency.