Abstract 3494: Short Duration Hypertension is Associated with the Development of Substrate for Atrial Fibrillation
Hypertension is frequently complicated by the development of atrial fibrillation (AF). However, the mechanisms of this link are poorly understood. Whether short duration hypertension results in atrial substrate alteration predisposing to AF is not known. Sixteen Merino Cross sheep (54±11kg) were studied. Ten had induced hypertension for 7±4 weeks via the “one-kidney, one-clip” model while six were controls. MRI and invasive blood pressure measurements were used to assess functional changes. Open-chest electrophysiological study was performed using a custom made 128-electrode epicardial plaque applied to both right (RA) & left atria (LA) including the Bachmann’s Bundle to determine: effective refractory periods (ERP) and conduction velocity (CV) at four pacing cycle lengths across six sites. Tissue specimens were harvested for structural analysis. The hypertensive group demonstrated the following compared to controls: higher BP (176/119 vs 95/62 mmHg; P<0.0001); enlarged LA (42 vs 29 ml; P<0.05); reduced LA ejection fraction (25 vs 31%; P<0.05); preserved LVEF (42 vs 44%; P=NS); longer P-wave duration; higher mean ERP; slower CV; increased absolute range of conduction phase delay (P5–95); higher conduction heterogeneity index (CHI, P5–95/P50); greater AF inducibility and increased AF durations. Picrosirius red staining of atrial tissues revealed increased interstitial fibrosis (p<0.05) with evidence of inflammatory cell infiltrates but without significant atrial myocyte hypertrophy. Short duration hypertension is associated with significant atrial remodeling characterized by atrial enlargement, inflammatory cell infiltrates, interstitial fibrosis, slowed/heterogeneous conduction, increased ERP and greater propensity for AF. These findings highlight the importance of early aggressive therapy for hypertension if the development of the arrhythmogenic substrates is to be prevented.