Left atrial scarring and conduction velocity dynamics: Rate dependent conduction slowing predicts sites of localized reentrant atrial tachycardias.

BACKGROUND: Low voltage zones (LVZs) are associated with conduction velocity (CV) slowing. Rate-dependent CV slowing may play a role in reentry mechanisms. METHODS: Patients undergoing catheter ablation for AT were enrolled. Aim was to assess the relationship between rate-dependent CV slowing and sites of localized reentrant atrial tachycardias (AT). On a bipolar voltage map regions were defined as non-LVZs [≥0.5 mV], LVZs [0.2-0.5 mV] and very-LVZs [<0.2 mV]. Unipolar electrograms were recorded with a 64-pole basket catheter during uninterrupted atrial pacing at four pacing intervals (PIs) during sinus rhythm. CVs were measured between pole pairs along the wavefront path. Sites of rate-dependent CV slowing were defined as exhibiting a reduction in CV between PI = 600 ms and 250 ms of ≥20% more than the mean CV reduction seen between these PIs for that voltage zone. Rate-dependent CV slowing sites were correlated to sites of localized reentrant ATs as confirmed with conventional mapping, entrainment and response to ablation. RESULTS: Eighteen patients were included (63 ±â€¯10 years). Mean CV at 600 ms was 1.53 ±â€¯0.19 m/s in non-LVZs, 1.14 ±â€¯0.15 m/s in LVZs, and 0.73 ±â€¯0.13 m/s in very-LVZs respectively (p < 0.001). Rate-dependent CV slowing sites were predominantly in LVZs [0.2-0.5 mV] (74.4 ±â€¯10.3%; p < 0.001). Localized reentrant ATs were mapped to these sites in 81.8% of cases (sensitivity 81.8%, 95% CI 48.2-97.9% and specificity 83.9%, 95% CI 81.8-86.0%). Macro-reentrant or focal ATs were not mapped to sites of rate-dependent CV slowing. CONCLUSIONS: Rate-dependent CV slowing sites are predominantly confined to LVZs [0.2-0.5 mV] and the resultant CV heterogeneity may promote reentry mechanisms. These may represent a novel adjunctive target for AT ablation.

Validation of a novel mapping system and utility for mapping complex atrial tachycardias.

INTRODUCTION: This study sought to validate a novel wavefront mapping system utilizing whole-chamber basket catheters (CARTOFINDER, Biosense Webster). The system was validated in terms of (1) mapping atrial-paced beats and (2) mapping complex wavefront patterns in atrial tachycardia (AT). METHODS AND RESULTS: Patients undergoing catheter ablation for AT and persistent AF were included. A 64-pole-basket catheter was used to acquire unipolar signals that were processed by CARTOFINDER mapping system to generate dynamic wavefront propagation maps. The left atrium was paced from four sites to demonstrate focal activation. ATs were mapped with the mechanism confirmed by conventional mapping, entrainment, and response to ablation. Twenty-two patients were included in the study (16 with AT and 6 with AF initially who terminated to AT during ablation). In total, 172 maps were created with the mapping system. It correctly identified atrial-pacing sites in all paced maps. It accurately mapped 9 focal/microreentrant and 18 macroreentrant ATs both in the left and right atrium. A third and fourth observer independently identified the sites of atrial pacing and the AT mechanism from the CARTOFINDER maps, while being blinded to the conventional activation maps. CONCLUSIONS: This novel mapping system was effectively validated by mapping focal activation patterns from atrial-paced beats. The system was also effective in mapping complex wavefront patterns in a range of ATs in patients with scarred atria. The system may therefore be of practical use in the mapping and ablation of AT and could have potential for mapping wavefront activations in AF.

A propensity matched case-control study comparing efficacy, safety and costs of the subcutaneous vs. transvenous implantable cardioverter defibrillator.

BACKGROUND: Subcutaneous implantable cardioverter defibrillators (S-ICD) have become more widely available. However, comparisons with conventional transvenous ICDs (TV-ICD) are scarce. METHODS: We conducted a propensity matched case-control study including all patients that underwent S-ICD implantation over a five-year period in a single tertiary centre. Controls consisted of all TV-ICD implant patients over a contemporary time period excluding those with pacing indication, biventricular pacemakers and those with sustained monomorphic ventricular tachycardia requiring anti-tachycardia pacing. Data was collected on device-related complications and mortality rates. A cost efficacy analysis was performed. RESULTS: Sixty-nine S-ICD cases were propensity matched to 69 TV-ICD controls. During a mean follow-up of 31±19 (S-ICD) and 32±21months (TV-ICD; p=0.88) there was a higher rate of device-related complications in the TV-ICD group predominantly accounted for by lead failures (n=20, 29% vs. n=6, 9%; p=0.004). The total mean cost for each group, including the complication-related costs was £9967±4511 ($13,639±6173) and £12,601±1786 ($17,243±2444) in the TV-ICD and S-ICD groups respectively (p=0.0001). Even though more expensive S-ICD was associated with a relative risk reduction of device-related complication of 70% with a HR of 0.30 (95%CI 0.12-0.76; p=0.01) compared to TV-ICDs. CONCLUSIONS: TV-ICDs are associated with increased device-related complication rates compared to a propensity matched S-ICD group during a similar follow-up period. Despite the existing significant difference in unit cost of the S-ICD, overall S-ICD costs may be mitigated versus TV-ICDs over a longer follow-up period.

Outcomes after cryoablation vs. radiofrequency in patients with paroxysmal atrial fibrillation: impact of pulmonary veins anatomy.

AIMS: Pulmonary vein isolation is the mainstay of treatment in catheter ablation of paroxysmal atrial fibrillation (AF). Cryoballoon ablation has been introduced more recently than radiofrequency ablation, the standard technique in most centres. Pulmonary veins frequently display anatomical variants, which may compromise the results of cryoballoon ablation. We aimed to evaluate the mid-term outcomes of cryoballoon ablation in an unselected population with paroxysmal AF from an anatomical viewpoint. METHODS AND RESULTS: Consecutive patients with paroxysmal AF who underwent a first procedure of cryoballoon ablation or radiofrequency were enrolled in this single-centre study. All patients underwent systematic standardized follow-up. Comparisons between radiofrequency and cryoballoon ablation (Arctic Front™ or Arctic Front Advance™) were performed regarding safety and efficacy endpoints, according to pulmonary vein (PV) anatomical variants. A total of 687 patients were enrolled (376 radiofrequency and 311 cryoballoon ablation). Baseline characteristics and distribution of PV anatomical variants were generally similar in the groups. After a mean follow-up of 14 ± 8 months, there was no difference in the incidence of relapse (17.0% cryoballoon ablation vs. 14.1% radiofrequency, P = 0.25). We observed no interaction of PV anatomical variants on mid-term procedural success. CONCLUSION: Our findings suggest that mid-term outcomes of cryoballoon ablation for paroxysmal AF ablation are similar to those of radiofrequency, regardless of PV anatomy. The presence of anatomical variants of PVs should not discourage the referral of patients with paroxysmal AF for cryoballoon ablation.

Manchester triage in acute pulmonary embolism: can it unmask the grand impersonator?

BACKGROUND: Acute pulmonary embolism (PE) is associated with high mortality risk. Early diagnosis is difficult because of non-specific clinical presentation and delay in imaging confirmation. Manchester Triage (MT) prioritises patients on the basis of illness severity and potentially recognises those with higher mortality risk. No studies of the role and impact of MT on rapid PE diagnosis and in-hospital mortality (IHM) have been carried out. OBJECTIVE: To assess the appropriateness of MT in this set of patients presenting acutely to the emergency department (ED), and to determine whether it assists in a rapid diagnosis, acts as a protective triage tool and affects short-term mortality. METHODS: Single-centre retrospective study of 176 consecutive patients with PE, assessed by MT in the ED between January 2006 and October 2010 (mean age 70.5±15.7 years, 38.6% men). The primary outcome measure was all-cause IHM. RESULTS: IHM was seen in 30 (17%) patients. More than half of the patients with PE (54%) were classified as target time for first medical observation (MOb) ≤10 min. 73.3% of IHM occurred in this group (p=0.020) with several increased markers of illness severity. MOb ≤10 min was not associated with faster PE imaging confirmation. The average door-to-diagnosis time (PEDx) was 26.8±36.8 h and PEDx >17.0 h was associated with higher IHM (p=0.017). On multivariate analysis, thrombolysis and MOb ≤10 min were included in an IHM predictor model. CONCLUSION: MT has high sensitivity in identifying patients with PE at risk. Those patients assigned as MOb ≤10 min have increased markers of illness severity and higher IHM. MT acts as a protective system in this challenging set and should be used as a patient's first assessment, aiding the emergency medical team to recognise those in need of urgent assessment and treatment.