Intra-Atrial Dyssynchrony Using Cardiac Magnetic Resonance to Quantify Tissue Remodeling in Patients with Atrial Fibrillation / Dessincronia Intra-atrial à Ressonância Magnética Cardíaca para Quantificação da Remodelação Tecidual em Pacientes com Fibrilação Atrial

Abstract Background: Recent studies suggest that left atrial (LA) late gadolinium enhancement (LGE) can quantify the underlying tissue remodeling that harbors atrial fibrillation (AF). However, quantification of LA-LGE requires labor-intensive magnetic resonance imaging acquisition and postprocessing at experienced centers. LA intra-atrial dyssynchrony assessment is an emerging imaging technique that predicts AF recurrence after catheter ablation. We hypothesized that 1) LA intra-atrial dyssynchrony is associated with LA-LGE in patients with AF and 2) LA intra-atrial dyssynchrony is greater in patients with persistent AF than in those with paroxysmal AF. Method: We conducted a cross-sectional study comparing LA intra-atrial dyssynchrony and LA-LGE in 146 patients with a history of AF (60.0 ± 10.0 years, 30.1% nonparoxysmal AF) who underwent pre-AF ablation cardiac magnetic resonance (CMR) in sinus rhythm. Using tissue-tracking CMR, we measured the LA longitudinal strain in two- and four-chamber views. We defined intra-atrial dyssynchrony as the standard deviation (SD) of the time to peak longitudinal strain (SD-TPS, in %) and the SD of the time to the peak pre-atrial contraction strain corrected by the cycle length (SD-TPSpreA, in %). We used the image intensity ratio (IIR) to quantify LA-LGE. Results: Intra-atrial dyssynchrony analysis took 5 ± 9 minutes per case. Multivariable analysis showed that LA intra-atrial dyssynchrony was independently associated with LA-LGE. In addition, LA intra-atrial dyssynchrony was significantly greater in patients with persistent AF than those with paroxysmal AF. In contrast, there was no significant difference in LA-LGE between patients with persistent and paroxysmal AF. LA intra-atrial dyssynchrony showed excellent reproducibility and its analysis was less time-consuming (5 ± 9 minutes) than the LA-LGE (60 ± 20 minutes). Conclusion: LA Intra-atrial dyssynchrony is a quick and reproducible index that is independently associated with LA-LGE to reflect the underlying tissue remodeling.

Resumo Fundamento: Estudos recentes sugerem que o realce tardio com gadolínio (RTG) no átrio esquerdo (AE) pode quantificar a remodelação tecidual subjacente que abriga a fibrilação atrial (FA). No entanto, a quantificação do RTG-AE requer um trabalho intenso de aquisição por ressonância magnética e pós-processamento em centros experientes. A avaliação da dessincronia intra-atrial no AE é uma técnica de imagem emergente que prediz a recorrência da FA após ablação por cateter. Nós levantamos as hipóteses de que 1) a dessincronia intra-atrial está associada ao RTG-AE em pacientes com FA e 2) a dessincronia intra-atrial é maior em pacientes com FA persistente do que naqueles com FA paroxística. Método: Realizamos um estudo transversal comparando a dessincronia intra-atrial no AE e o RTG-AE em 146 pacientes com história de FA (60,0 ± 10,0 anos, 30,1% com FA não paroxística) submetidos à ressonância magnética cardíaca (RMC) durante ritmo sinusal antes da ablação da FA. Com utilização de RMC com tissue tracking, medimos o strain longitudinal do AE em cortes de duas e quatro câmaras. Definimos a dessincronia intra-atrial como o desvio padrão (DP) do tempo até o pico do strain longitudinal (DP-TPS, em %) e o DP do tempo até o pico do strain antes da contração atrial corrigido pela duração do ciclo (DP-TPSpreA, em %). Utilizamos a razão da intensidade da imagem (RIM) para quantificar o RTG-AE. Resultados: A análise da dessincronia intra-atrial levou 9 ± 5 minutos por caso. A análise multivariada mostrou que a dessincronia intra-atrial no AE esteve independentemente associada ao RTG-AE. Além disso, a dessincronia intra-atrial no AE foi significativamente maior em pacientes com FA persistente do que naqueles com FA paroxística. Por outro lado, não houve diferença significativa no RTG-AE entre pacientes com FA persistente e paroxística. A dessincronia intra-atrial no AE mostrou excelente reprodutibilidade e sua análise foi menos demorada (5 ± 9 minutos) do que o RTG-AE (60 ± 20 minutos). Conclusão: A dessincronia intra-atrial no AE é um índice rápido, reprodutível e independentemente associado ao RTG-AE para indicar remodelação tecidual subjacente. (Arq Bras Cardiol. 2019; 112(4):441-450)

Increased beat-to-beat QT variability in patients with congestive cardiac failure.

BACKGROUND: QT interval on the surface electrocardiogram reflects the time for repolarization of myocardium. Prolongation of rate-corrected QT interval, QTc is strongly associated with sudden cardiac death. Recent studies using novel techniques on beat-to-beat QT interval variability have shown that an increase in QT interval variability is associated with increased sympathetic activity and is a predictor of sudden cardiac death. We studied QT variability in patients with congestive cardiac failure, as it is associated with an increase in cardiac sympathetic activity and also sudden death. METHODS AND RESULTS: We compared beat-to-beat heart rate and QT interval data in 2 3 patients with congestive cardiac failure and 19 age-matched normal controls. The electrocardiographic data were acquired in lead II configuration at a sampling rate of 1000 Hz. Heart rate variability was found to be significantly lower while QT variability measures were significantly higher in patients compared to controls. QTvi (a common log ratio of QT variability normalized for mean QT interval squared divided by heart rate variability normalized for mean heart rate squared) was also significantly higher in patients compared to controls. Clinical improvement in some of these patients is associated with a decrease in QTvi, due mainly to an increase in cardiac vagal function. CONCLUSIONS: Our results suggest a decrease in cardiac vagal and an increase in cardiac sympathetic functions in patients with congestive cardiac failure. QTvi may prove to be a useful surrogate end point to evaluate treatment effect in these patients.