title: Atrial supply-demand balance in healthy adult pigs: coronary blood flow, oxygen extraction, and lactate production during acute atrial fibrillation.
abstract: OBJECTIVE
  Little is known about how atrial oxygen supply responds to increased demand, and under which conditions it falls short (supply-demand mismatch). Here, we have investigated the vasodilator response, oxygen extraction, and lactate production of the left atrium (LA) and left ventricle (LV) in response to atrial pacing and atrial fibrillation (AF).
  
  
  RESULTS
  Series A (n = 9 Dutch landrace pigs) was instrumented to measure LA and LV vascular conductance in branches of the circumflex artery. Coronary conductance reserve (CCR) was calculated as the ratio between conductance during adenosine infusion and baseline. Series B (n = 7) was instrumented with sampling catheters in LA and LV veins for determination of blood gases and lactate levels. LA CCR (1.76 ± 0.14) was significantly lower than LV CCR (3.16 ± 0.27, P = 0.002). However, basal oxygen extraction was lower in LA (27 ± 3%) than that in the LV (58 ± 6%, P = 0.0006), indicating a larger extraction reserve in the LA than that in the LV (4.68 ± 0.84 vs. 1.88 ± 0.26, P = 0.01). Atrial pacing caused an increase in LA conductance (Series A) and oxygen extraction (Series B). AF increased LA vascular conductance to 177 ± 14% at 1 min, 168 ± 14 at 5 min, and 164 ± 31% at 10 min of AF (P < 0.05 vs. baseline). Atrial oxygen extraction also increased from 26 ± 3% at baseline to 63 ± 5% (P < 0.01) at 5 min and 60 ± 11% (P < 0.01) at 10 min of AF. Arterio-venous lactate difference increased significantly (P = 0.02) during AF.
  
  
  CONCLUSIONS
  In healthy pigs, the LA has a lower CCR, but a higher extraction reserve compared with the LV. Although both reserves were recruited during AF, atrial lactate production increased significantly.
authors.affiliation: Department of Physiology, Faculty of Medicine, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: van Bragt
authors.forename: Hussein M
authors.initials: HM
authors.lastname: Nasrallah
authors.forename: Marion
authors.initials: M
authors.lastname: Kuiper
authors.forename: Joost J
authors.initials: JJ
authors.lastname: Luiken
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schotten
authors.forename: Sander
authors.initials: S
authors.lastname: Verheule
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D003326:Coronary Circulation; D019344:Lactic Acid / Q000378:metabolism*; D010100:Oxygen / Q000502:physiology*; D013552:Swine
chemical_list: D019344:Lactic Acid; D010100:Oxygen
keywords: Atrial fibrillation; Coronary blood flow; Oxygen extraction; Supply–demand ischaemia