Left Atrial Size and Function in a Canine Model of Chronic Atrial Fibrillation and Heart Failure

Abstract

BackgroundOur aim was to assess how atrial fibrillation (AF) induction, chronicity, and RR interval irregularity affect left atrial (LA) function and size in the setting of underlying heart failure (HF), and to determine whether AF effects can be mitigated by vagal nerve stimulation (VNS).MethodsHF was induced by 4-weeks of rapid ventricular pacing in 24 dogs. Subsequently, AF was induced and maintained by atrial pacing at 600 bpm. Dogs were randomized into control (n = 9) and VNS (n = 15) groups. In the VNS group, atrioventricular node fat pad stimulation (310 μs, 20 Hz, 3–7 mA) was delivered continuously for 6 months. LA volume and LA strain data were calculated from bi-weekly echocardiograms.ResultsRR intervals decreased with HF in both groups (p = 0.001), and decreased further during AF in control group (p = 0.014), with a non-significant increase in the VNS group during AF. LA size increased with HF (p<0.0001), with no additional increase during AF. LA strain decreased with HF (p = 0.025) and further decreased after induction of AF (p = 0.0001). LA strain decreased less (p = 0.001) in the VNS than in the control group. Beat-by-beat analysis showed a curvilinear increase of LA strain with longer preceding RR interval, (r = 0.45, p <0.0001) with LA strain 1.1% higher (p = 0.02) in the VNS-treated animals, independent of preceding RR interval duration. The curvilinear relationship between ratio of preceding and pre-preceding RR intervals, and subsequent LA strain was weaker, (r = 0.28, p = 0.001). However, VNS-treated animals again had higher LA strain (by 2.2%, p = 0.002) independently of the ratio of preceding and pre-preceding RR intervals.ConclusionsIn the underlying presence of pacing-induced HF, AF decreased LA strain, with little impact on LA size. LA strain depends on the preceding RR interval duration.

Comprehensive assessment of left atrial and ventricular remodeling in paroxysmal atrial fibrillation by the cardiovascular magnetic resonance myocardial extracellular volume fraction and feature tracking strain

“…Our study revealed that CMR-FT LA strain could identify subtle LA booster pump dysfunction undetectable by conventional active LAEF. Our study found no correlation between the LA strain/strain rate and heart rate, as a conflicting result to a previous study reported by Goldberg et al in which a curvilinear increase in the LA strain with a longer RR interval ( r = 0.45, P < 0.0001) was found 32 . In our cohort, 90 out of 106 PAF patients (84%) took antiarrhythmic drugs with negative inotropic effects and more than half of them (56%) were prescribed beta-blockers.…”

“…Consequently, the high proportion of negative inotropic medicine (mainly betablockers) use with various types and doses may have resulted in a loss of the entire correlation between the LA strain and heart rate in this study. Additionally, the correlation between the LA strain and heart rate was established in normal conditions in the previous studies 32 , 34 . The difference in the LA between normal and PAF patients (LA functional and anatomical remodeling) may lead to conflicting results.…”

Prognostic value of echocardiographic indices of left atrial morphology and function in dogs with myxomatous mitral valve disease

“…In our study, STE‐derived PALS, PACS, and CSI were all univariate predictors of survival. Left atrial strain recently has been studied to validate the technique in clinically healthy dogs and to evaluate strain changes in dogs under experimental conditions, or in dogs with naturally occurring MMVD . With progression of disease, STE‐derived variables tend to decrease as a consequence of progressive impairment in LA contraction and relaxation .…”

A Review on Atrial Fibrillation (Computer Simulation and Clinical Perspectives)

“…As a result, there are different approaches to its computer simulation that are validated with real data. Apart from human cellular models, sheep [36][37][38][39][40][41][42], canine [43][44][45][46][47], frog [48], rabbit [49], and mice [50] models have also been discussed in the literature.…”