Influence of Atrial Function and Mechanical Synchrony on LV Hemodynamic Status in Heart Failure Patients on Resynchronization Therapy

Short-term safety and feasibility of a practical approach to combined atrial and ventricular physiological pacing: An initial single-center experience

Background

Traditional right atrial appendage (RAA) pacing accentuates conduction disturbances as opposed to Bachmann bundle pacing (BBP).

Objective

The purpose of this study was to evaluate the feasibility, efficacy, and safety of routine anatomically guided high right atrial septal (HRAS) pacing with activation of Bachmann bundle combined with routine left bundle branch area pacing (LBBAP).

Methods

This retrospective single-center study included 96 consecutive patients who underwent 1 of 2 strategies: physiological pacing (PP) (n = 32) with HRAS and LBBAP leads and conventional pacing (CP) (n = 64) with traditional RAA and right ventricular apical leads. Baseline characteristics, sensing, pacing thresholds, and impedances were recorded at implantation and follow-up.

Results

The PP and CP cohorts were of similar age (74.2 ± 13.8 years vs 73.9 ± 9.9 years) and sex (28.1% vs 40.6% female). There were no differences in procedural time (95.0 ± 31.4 minutes vs 86.5 ± 33.3 minutes; P = .19) or fluoroscopy time (12.1 ± 4.5 minutes vs 12.3 ± 13.5 minutes; P = .89) between cohorts. After excluding patients who received >2 leads, these parameters became significantly shorter in the CP cohort. The PP cohort exhibited higher atrial pacing thresholds (1.5 ± 1.1 mV vs 0.8 ± 0.3 mV; P <.001) and lower p waves (1.8 ± 0.8 mV vs 3.8 ± 2.3 mV; P <.001) at implantation and at follow-up. In the PP cohort, 72% of implants met criteria for BBP; of the ventricular leads, 94% demonstrated evidence of LBBAP. One lead-related complication occurred in each cohort.

Conclusion

Routine placement of leads in the HRAS is a feasible and safe alternative to standard RAA pacing, allowing for BBP in 72% of patients. HRAS pacing can be combined with LBBAP as a routine strategy.

Effect of pacing site on P wave parameters: Within-patient comparison of right atrial appendage and Bachmann's bundle

BACKGROUND

Conventional right atrial appendage pacing (RAAp) is associated with adverse clinical outcomes mediated in part by electromechanical atrial delays. Bachmann's bundle pacing (BBp) offers more physiologic atrial activation; however, detailed analysis of pacing site on paced P wave parameters is lacking.

METHODS

Intraprocedural electrocardiograms of 21 consecutive patients undergoing atrial lead implantation were retrospectively analyzed and within-patient comparisons of 7 P wave parameters (P wave duration, P wave voltage, P wave area, PR interval, PR segment, PTFV1 and P wave axis) during sinus rhythm, RAAp and BBp performed.

RESULTS

The median basal P wave duration was prolonged at 134.5 ms (Q1,Q3: 120.5, 150.5) and similarly prolonged during RAAp at 144.0 ms (127.0, 176.0) but was significantly reduced with BBp at 98.0 ms (93.0, 116.0; p = 0.005 and p < 0.001, respectively). The median basal P wave voltage in lead II was normal at 0.11 mV (0.08, 0.15) but significantly reduced during RAAp at 0.08 mV (0.04, 0.11) and greatest during BBp at 0.16 mV (0.09, 0.19; p < 0.001 and p = 0.003, respectively). The median basal PR interval was top normal at 185.0 ms (163.0, 213.0) and similarly prolonged during RAAp at 204.0 ms (166.5, 221.0) but was significantly shortened during BBp at 163.0 ms (142.0, 208.0; p = 0.03 and p = 0.001, respectively).

CONCLUSIONS

BBp has favorable effects on the paced P wave parameters including marked shortening in P wave duration, increase in P wave voltage in lead II and increase in PR segment which may offer significant hemodynamic advantages over conventional RAAp.

Alternative atrial pacing site to improve cardiac function: focus on Bachmann's bundle pacing

Pacing from the right atrial appendage (RAA) prolongs the P wave duration and can induce interatrial and especially left-sided atrio-ventricular dyssynchrony. Pacing from Bachmann's bundle closely reproduces normal physiology and has the potential to avoid the electromechanical dysfunction associated with conventional RAA pacing. Interatrial conduction delay is associated with an increased risk of stroke, heart failure, and death. In addition to a reduction in atrial fibrillation, Bachmann's bundle pacing has emerging applications as a hemodynamic pacing modality. This review outlines the pathophysiology of atrial conduction disturbances and their potential remedies and provides the reader with a practical guide to implementing Bachmann's bundle pacing with an emphasis on the recapitulation of normal electrical and mechanical function.

Atrial Pacing Affects Left Atrial Morphological and Functional Parameters Early after Pacemaker Implantation

Background and Objectives: Chronic atrial stimulation might impair left atrial (LA) function. We aimed to assess the impact of atrial pacing burden on LA volumetric and functional parameters after implantation of a dual-chamber pacemaker. Materials and Methods: The prospective study included 121 subjects with sinus node disease (SND) or atrioventricular block (AVB) that received a dual-chamber pacemaker. After device implantation, the subjects were divided into three groups: (1) SND with a lower rate (LR) set to 60 bpm and rate response enabled; (2) AVB with an LR set to 60 bpm and no rate response; and (3) AVB with an LR set to 40 bpm and no rate response. Subjects were followed at one and three months. Two subsets of patients with high and low atrial pacing burdens accompanied by low ventricular pacing percentage were analyzed. LA function was evaluated with volumetric and strain parameters from transthoracic echocardiography. Results: The high atrial low ventricular pacing group consisted of 38 subjects, and the low atrial low ventricular group consisted of 22 subjects. When looking at the change in volumetric parameters, we observed a tendency for volumes to increase in both groups; however, only minimal LA volume reached statistical significance at three months in the high atrial pacing group. A trend towards the lowering of an active emptying fraction at one month (p = 0.076) became significant at three months (p = 0.043), and was also only observed in the same group. Moreover, a decrease in the tendency to reach statistical significance at three months for reservoir and contractile strain parameters and stiffness index was only observed in the high atrial pacing group. Meanwhile, in the low atrial pacing burden group, all parameters remained significantly unchanged. Conclusions: The burden of right atrial pacing in patients with preserved left ventricular function negatively influences functional and morphologic LA parameters. Moreover, negative effects take place soon after pacemaker implantation and appear to be sustained.

Assessment of right atrial dyssynchrony by 2D speckle-tracking in healthy young men following high altitude exposure at 4100 m

Background

High altitude exposure induces overload of right-sided heart and may further predispose to supraventricular arrhythmia. It has been reported that atrial mechanical dyssynchrony is associated with atrial arrhythmia. Whether high altitude exposure causes higher right atrial (RA) dyssynchrony is still unknown. The aim of study was to investigate the effect of high altitude exposure on right atrial mechanical synchrony.

Methods

In this study, 98 healthy young men underwent clinical examination and echocardiography at sea level (400 m) and high altitude (4100 m) after an ascent within 7 days. RA dyssynchrony was defined as inhomogeneous timing to peak strain and strain rate using 2D speckle-tracking echocardiography.

Results

Following high altitude exposure, standard deviation of the time to peak strain (SD-TPS) [36.2 (24.5, 48.6) ms vs. 21.7 (12.9, 32.1) ms, p<0.001] and SD-TPS as percentage of R–R’ interval (4.6 ± 2.1% vs. 2.5 ± 1.8%, p<0.001) significantly increased. Additionally, subjects with higher SD-TPS (%) at high altitude presented decreased right ventricular global longitudinal strain and RA active emptying fraction, but increased RA minimal volume index, which were not observed in lower group. Multivariable analysis showed that mean pulmonary arterial pressure and tricuspid E/A were independently associated with SD-TPS (%) at high altitude.

Conclusion

Our data for the first time demonstrated that high altitude exposure causes RA dyssynchrony in healthy young men, which may be secondary to increased pulmonary arterial pressure. In addition, subjects with higher RA dyssynchrony presented worse RA contractile function and right ventricular performance.

Methodological Gaps in Left Atrial Function Assessment by 2D Speckle Tracking Echocardiography

The assessment of left atrial (LA) function is used in various cardiovascular diseases. LA plays a complementary role in cardiac performance by modulating left ventricular (LV) function. Transthoracic two-dimensional (2D) phasic volumes and Doppler echocardiography can measure LA function non-invasively. However, evaluation of LA deformation derived from 2D speckle tracking echocardiography (STE) is a new feasible and promising approach for assessment of LA mechanics. These parameters are able to detect subclinical LA dysfunction in different pathological condition. Normal ranges for LA deformation and cut-off values to diagnose LA dysfunction with different diseases have been reported, but data are still conflicting, probably because of some methodological and technical issues. This review highlights the importance of an unique standardized technique to assess the LA phasic functions by STE, and discusses recent studies on the most important clinical applications of this technique.

Effect of Cardiac Resynchronization Therapy on Left Atrial Size and Function as Expressed by Speckle Tracking 2-Dimensional Strain

Changes in left atrial (LA) strain in patients treated with cardiac resynchronization therapy (CRT) remain not entirely explored. We prospectively evaluated long-term changes in LA size and function and their relation with left ventricular (LV) reverse remodeling and noninvasive hemodynamic variables in patients treated with CRT by 2-dimensional speckle tracking echocardiography. Thirty patients (62 ± 11 years, 63% men) underwent 2-dimensional speckle tracking echocardiography before implant and after 12 months. LA area, global and regional LA strains, LV ejection fraction (LVEF) and longitudinal strain, mitral regurgitation (MR), and diastolic variables were evaluated. At 12 months, CRT responders (60%) exhibited an increase in LA strain (11.4 ± 6.5% vs 16.5 ± 7.9%, p <0.001) and a reduction in LA area (p = 0.002), which were associated with an improvement in MR, E/E' ratio, LVEF, and LV longitudinal strain. In nonresponders, a worsening in LA strain (11.4 ± 6.8% vs 8.7 ± 4.6%, p = 0.017) and LA area (p = 0.002) occurred in parallel with an increase in E/E', whereas LVEF and LV longitudinal strain were unchanged. In conclusion, over long-term follow-up, LA size and strain improved in CRT responders, while worsening in nonresponders. Changes in LV function, filling pressures, and MR seem to be related to LA reverse remodeling, giving a feedback loop.