title: Comparison of nifedipine and metoprolol on collateral coronary blood flow in a swine model of chronic coronary obstruction and acute ischaemia during isoflurane anaesthesia.
abstract: OBJECTIVE
  This study compared the effects of nifedipine and metoprolol on collateral-dependent myocardial blood flow in a swine model of chronic coronary obstruction and acute ischaemia during isoflurane anaesthesia.
  
  
  METHODS
  Collateral coronary circulation was induced in 15 three-week-old piglets by banding of the proximal left anterior descending coronary artery (LAD). After 8-10 wk, the distal LAD was ligated and the open-chest pigs were randomized to receive infusions of either saline, nifedipine (5 micrograms.kg-1.min-1) or metoprolol (10 micrograms.kg-1.min-1) for 30 min during isoflurane anaesthesia (2%). Transient ischaemia was induced by 30 sec occlusion of the left circumflex artery. Arterial blood pressures, heart rate and regional myocardial blood flow (radiolabelled microspheres technique) were measured at the end of drug infusion (baseline) and one minute after transient ischaemia.
  
  
  RESULTS
  No differences in the blood flow to the collateral-dependent (CD) myocardium or haemodynamic variables were observed at baseline among the three groups. Following transient ischaemia, in the nifedipine but not in the metoprolol group, blood flow to the CD myocardium was reduced by 28 +/- 24% in the epicardium (P < 0.05) and 56 +/- 20% in the endocardium (P < 0.01), resulting from intercoronary and transmural steal. This was associated with a moderate increase (10%, P < 0.05) in the heart rate in the nifedipine group.
  
  
  CONCLUSIONS
  In a swine model of chronic coronary obstruction and acute ischaemia during isoflurane anaesthesia, the collateral coronary blood flow was maintained in the presence of metoprolol, but reduced in the presence of nifedipine following transient ischaemia due to intercoronary and transmural steal.
authors.affiliation: Department of Anaesthesia, University of Toronto, Ontario, Canada.
authors.forename: D C
authors.initials: DC
authors.lastname: Cheng
authors.forename: M T
authors.initials: MT
authors.lastname: Jiang
authors.forename: B
authors.initials: B
authors.lastname: Asokumar
authors.forename: P
authors.initials: P
authors.lastname: Boylen
authors.forename: A
authors.initials: A
authors.lastname: Sandler
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002908:Chronic Disease; D003097:Collateral Circulation / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects*; D003327:Coronary Disease / Q000503:physiopathology*; D004347:Drug Interactions; D007530:Isoflurane / Q000494:pharmacology*; D008790:Metoprolol / Q000494:pharmacology*; D017202:Myocardial Ischemia / Q000503:physiopathology*; D009543:Nifedipine / Q000494:pharmacology*; D013552:Swine
chemical_list: D000319:Adrenergic beta-Antagonists; D018685:Anesthetics, Inhalation; D002121:Calcium Channel Blockers; D007530:Isoflurane; D008790:Metoprolol; D009543:Nifedipine