Alternate Site Atrial Pacing in the Young: Conventional Echocardiography and Tissue Doppler Analysis of the Effects on Atrial Function and Ventricular Filling

[Bachmann bundle pacing]

In pacemaker and ICD therapy, atrial leads are usually implanted in the right atrial appendage (RAA). This is easy but associated with a risk of negative hemodynamic and electrophysiological effects. Atrial depolarization, atrial contraction, and atrioventricular conduction can be delayed and desynchronized by RAA pacing leading to atrial fibrillation, pacing-induced long first-degree AV block, right ventricular pacing and the development of heart failure. High-septal atrial pacing near Bachmann's bundle that connects the right and left atrium can prevent the negative effects of RAA pacing and synchronize atrial excitation as demonstrated by the shortening of the PQ time and P wave duration during Bachmann bundle pacing. This review presents techniques to implant atrial leads at Bachmann's bundle. Apart from fluoroscopy in left anterior oblique projection, no additional effort compared to RAA implantation is required. Clinical studies on Bachmann bundle pacing are sparse; our own results suggest beneficial effects in patients with sick sinus syndrome and paroxysmal atrial fibrillation who receive atrial pacing for ≥50% of the time. Bachmann bundle pacing represents an interesting and simple option for atrial pacing. It is desirable to make this technique known to a wider spectrum of implanters and to generate more data on its clinical potential.

Ten-Year Clinical Experience with the Lumenless, Catheter-Delivered, 4.1-Fr Diameter Pacing Lead in Patients with and without Congenital Heart

BACKGROUND

Patients with congenital heart defects (CHD) often present more challenges to pacing therapy due to anatomy than those without CHD. The lumenless, 4.1Fr diameter M3830 pacing lead (Medtronic, Inc., Minneapolis, MN, USA), approved for use in 2005, has, to date, reported to have excellent short-term (<6 years) lead performance. Unfortunately, very long-term performance is unknown, especially among CHD patients and with implants at alternate pacing (AP) sites. This study reports a 10-year clinical experience with the M3830 lead.

METHODS

Records of patients who received the M3830 lead were reviewed: patient demographics, implant techniques and locations, sensing and pacing characteristics, impedances (Imp), and any complications at implant and follow-up.

RESULTS

From 2005 to 2015, 141 patients (ages 2-50, mean 20.1 years, 57% males) received 212 leads: atrial 115; ventricle 97. CHD was present in 62% of patients. Leads were inserted at AP sites in 96% of patients. Postimplant follow-up was from 3 months to 10 years (mean 56.3 months). Comparative implant versus follow-up values (mean ± standard deviation) were available on 196 leads (92.5%), showing persistently low (<1 v @ 0.4-0.5 ms) pacing thresholds (P = 0.57). Sensing was also comparable (atrial leads, P = 0.41; ventricular leads, P = 0.9). Impedances differed (P < 0.05) but remained within the normal range. Two A leads became dislodged and one was repositioned while two other leads (1 A, 1 V) were extracted. There are no differences observed in the pacing characteristics between the CHD and non-CHD groups on follow-up.

CONCLUSIONS

The 4.1Fr lumenless pacing lead shows ease of implant regardless of CHD or AP site, excellent very long-term (10 years) stability, and performance indices with a very low rate of complications.

An AP endonuclease functions in active DNA demethylation and gene imprinting in Arabidopsis [corrected]

Active DNA demethylation in plants occurs through base excision repair, beginning with removal of methylated cytosine by the ROS1/DME subfamily of 5-methylcytosine DNA glycosylases. Active DNA demethylation in animals requires the DNA glycosylase TDG or MBD4, which functions after oxidation or deamination of 5-methylcytosine, respectively. However, little is known about the steps following DNA glycosylase action in the active DNA demethylation pathways in plants and animals. We show here that the Arabidopsis APE1L protein has apurinic/apyrimidinic endonuclease activities and functions downstream of ROS1 and DME. APE1L and ROS1 interact in vitro and co-localize in vivo. Whole genome bisulfite sequencing of ape1l mutant plants revealed widespread alterations in DNA methylation. We show that the ape1l/zdp double mutant displays embryonic lethality. Notably, the ape1l+/-zdp-/- mutant shows a maternal-effect lethality phenotype. APE1L and the DNA phosphatase ZDP are required for FWA and MEA gene imprinting in the endosperm and are important for seed development. Thus, APE1L is a new component of the active DNA demethylation pathway and, together with ZDP, regulates gene imprinting in Arabidopsis.