Paroxysmal atrial fibrillation with high vs. low arrhythmia burden: atrial remodelling and ablation outcome

AIMS

The relation between atrial tachyarrhythmia (ATA) burden in paroxysmal atrial fibrillation (AF), atrial remodelling, and efficacy of catheter ablation (CA) is unknown. We investigated whether high vs. low-burden paroxysmal AF patients have distinct clinical characteristics or electro-mechanical properties of the left atrium (LA) and whether burden impacts outcome of CA.

METHODS AND RESULTS

Atrial tachyarrhythmia burden, defined as the percentage of time spent in ATA, was assessed by insertable cardiac monitors in 105 patients before and after CA. Clinical characteristics and electro-mechanical properties of LA were compared between patients with high vs. low ATA burden. Catheter ablation efficacy was assessed by reduction in ATA burden and 1-year freedom from any ATA. Median ATA burden was 2.7% (highest tertile 9.3%). Clinical characteristics and electrical properties of LA (refractoriness, conduction velocity, low voltage) did not differ between high (≥9.3%) vs. low ATA burden (<9.3%) patients. High ATA burden patients had larger LA diameter (46.5 ± 6 vs. 42.5 ± 6mm, P < 0.01), volume (93.8 ± 22 vs. 80.4 ± 21mL, P = 0.01), and lower LA reservoir and contractile strain (19.7 ± 6 vs. 24.7 ± 6%, P < 0.01; 10.3 ± 3 vs. 12.8 ± 4%, P = 0.01). Catheter ablation reduced ATA burden by 100% (100-100) in both groups (P = 1.0). Freedom from ATA after CA was equally high (83% vs. 89%, P = 0.38).

CONCLUSION

Paroxysmal AF patients with high ATA burden have altered LA mechanical properties, reflected by larger size and impaired function. Despite mechanical remodelling of the atria, they are excellent responders to CA. Most likely the lack of fibrosis and/or advanced electrical remodelling explain why pulmonary veins remain the dominant trigger for AF in this patient cohort.

Left and Right Ventricle Leads Switch as a Solution for TWave Oversensing - How a Good Idea Turned Out Bad

A 50-year-old male with a CRT defibrillator received inappropriate ICD shocks due to T-wave oversensing. Decreasing the sensitivity to avoid T wave oversensing was not an option due to a suboptimal R-wave sensing amplitude. We decided to re-plug the LV lead in the RV port and the RV lead in the LV port. This however led to intermittent phrenic nerve stimulation due to mandatory bipolar (tip-ring) or unipolar (tip-can) pacing on the LV-lead from the RV port. Re-intervention was necessary with the implantation of an additional pacing/sensing RV lead. A software programmable choice to switch sensing and tachycardia detection from RV to LV lead could be a valuable feature in future CRT devices.

The midgestational rabbit as a model for the creation of membrane defects after needle fetoscopy

OBJECTIVES

The aim of the study was to determine whether the pregnant rabbit at mid gestation could be used as a suitable in vivo model for the study of membrane defects after invasive procedures.

STUDY DESIGN

Pregnant rabbits at gestational ages of 22 and 18 days (term is 32 days' gestation) underwent needle insertion with different instrument diameters (1.1 mm, 1.35 mm, 2.0 mm, and 2.7 mm). Two different insertion techniques were evaluated, blind amniotic puncture and puncture through surgically exposed amnion. Membrane integrity, presence of amniotic fluid, and fetal lung/body weight ratio were evaluated at 31 days' gestation.

RESULTS

Among rabbits operated on at 22 days' gestation the amniotic integrity restoration at 31 days' gestation ranged from 46% to 76% in the different diameter and access technique groups, as compared with 98% in untreated sacs (P <.05 for all groups). Fetuses from sacs with persisting membrane defects had oligohydramnios and significantly lower fetal lung/body weight ratios. Survival rates among fetuses operated on at 18 days' gestation were so poor that appropriate statistical analysis was not possible in this group.

CONCLUSIONS

The rabbit at mid gestation can be used as a model to reproduce permanent membrane defects after fetoscopy, reproducing oligohydramnios and pulmonary hypoplasia. This may provide a suitable in vivo model for the study of iatrogenic membrane defects.