Differential impact of short periods of rapid atrial pacing on left and right atrial mechanical function

Abstract

Current techniques to describe atrial function are limited by their load dependency and hence do not accurately reflect intrinsic mechanical properties. To assess the impact of atrial fibrillation on atrial function, combined pressure-volume relationships (PVR) measured by conductance catheters were used to evaluate the right (RA) and left (LA) atrium in 12 isoflurane-anesthetized pigs. Biatrial PVR were recorded over a wide range of volumes during transient caval occlusion at baseline sinus rhythm (SR), after onset of rapid atrial pacing (RAP), after 1 h of RAP, after conversion to SR, and after 1 h of recovery. Cardiac output decreased by 16% (P ϭ 0.008) with onset of RAP. Mean LA and RA pressures increased by 21 and 40% (P Ͻ 0.001), respectively, and remained elevated during the entire recovery period. RA reservoir function increased from 51 to 58% and significantly dropped to 43% after resumption of SR (P ϭ 0.017). Immediately after RAP, a right shift of LA end-systolic PVR-intercept for endsystolic volume required to generate an atrial end-systolic pressure of 10 mmHg (24.4 Ϯ 4.9 to 28.1 Ϯ 5.2 ml, P ϭ 0.005) indicated impaired contractility compared with baseline. Active LA emptying fraction dropped from 17.6 Ϯ 7.5 to 11.7 Ϯ 3.7% (P Ͻ 0.001), LA stroke volume and ⌬P/⌬t max/P declined by 22% (P ϭ 0.038 and 0.026, respectively), while there was only a trend to impaired RA systolic function. Stiffness quantified by the ratio of pressure to volume at end-diastole was increased immediately after RAP only in the RA (P ϭ 0.020), but end-diastolic PVR shifted rightward in both atria (P ϭ 0.011 LA, P ϭ 0.045 RA). These data suggest that even short periods of RAP have a differential impact on RA and LA function, which was sustained for 1 h after conversion to SR. arrhythmia; atrium; contractility; pressure; tachyarrhythmias ABNORMALITIES OF ATRIAL PERFORMANCE are clinically relevant and are present in many pathological conditions of the heart. Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide with an increase in our aging population (19). It results in a loss of booster pump function in the atrium, which might contribute to the significant morbidity and mortality secondary to hemodynamic compromise and tachycardiainduced cardiomyopathy in some patients. Due to this fact, most attention has been given to the impaired left atrial (LA) contractility during AF (24, 28). However, atrial diseases in which LA compliance is markedly reduced are associated with impaired LA filling while increase in diastolic stiffness resulting in increased LA pressure can maintain stroke volume in the absence of atrial booster pump function, indicating that the changes in mechanical atrial function during AF might be much more complex (5,22).Many previous studies focused on the evaluation of atrial function after the treatment of AF, including catheter ablation or surgery, and revealed a decremental effect of variable degrees of those procedures (7, 29). The Cox-Maze procedure (CMP) was introduced for the surgical tr...

The impact of 6 weeks of atrial fibrillation on left atrial and ventricular structure and function

“…Through a purse-string suture in the ascending aorta, a 5F PV conductance catheter (Millar SPR-766; Millar Instruments, Inc, Houston, Tex) was introduced and positioned along the long axis of the LV, with the tip of the catheter resting in the LVapex. 3 The pericardium was kept intact in both the control and paced animals. A second conductance catheter was inserted through a small pericardial incision into the LA through a purse-string suture at the base of the appendage.…”

“…The impact of prolonged AF on left atrial (LA) and left ventricular (LV) function has been incompletely characterized. Although there have been reports on the effect of paroxysmal atrial fibrillation (PAF) on LA and LV function by echocardiography 2 and reports on the effect of acute AF on LA and LV function by conductance catheter in an animal model, 3 there are few reports describing the influence of AF on LA and LV function and volume, and the severity of fibrosis induced by a defined period of AF.…”

Compensatory increase of left atrial external work to left ventricular dysfunction caused by afterload increase

“…LA pressure and LA volume or strain were synchronized to generate LA pressure-volume or pressure-strain loops. As previously demonstrated, the LA pressure-volume relationship typically represents a figure-of-eight pattern, with the two loops consisting of A-and V-loops (30). The A-loop represents active atrial contraction and relaxation, and the V-loop represents passive atrial reservoir filling and emptying.…”

“…The area inside of each loop represented external work. Other studies invasively measured the LA pressurevolume loops using a conductance catheter; however, it is methodologically challenging to evaluate the LA external work with this catheter (10,30).…”

Ultra‐rapid high‐density mapping system with the phase singularity technique is feasible in identifying rotors and focal sources and predicting AF termination

“…Animal studies on the effects of RAP on atrial remodeling demonstrated different impacts of pacing on right and left atrial functions with heterogeneity of sympathetic innervation predisposing to sustained AF. Weimar et al investigated the hemodynamic impact of AF on RA and LA during RAP and after restoration of sinus rhythm in an acute pig model by using combined pressure‐volume relationships and demonstrated a differential impact on RA and LA function of short periods of RAP, which was sustained for 1 hour after conversion to SR. Berenfeld et al demonstrated disorganized RA conduction after periodic high‐frequency pacing at the RA in a sheep model. In another RAP‐induced AF in dogs, Jayachandran et al, reported that RAP‐induced AF results in both autonomic and electrophysiological remodeling of the atria.…”