title: Sildenafil citrate on the inducibility of ventricular fibrillation and upper limit of vulnerability in swine.
abstract: BACKGROUND
  Sildenafil citrate at supratherapeutic levels has been reported to decrease defibrillation efficacy. However, its effects on ventricular fibrillation induction and the upper limit of vulnerability (ULV) have not been investigated. We tested the hypothesis that sildenafil citrate reduces the ventricular fibrillation threshold (VFT) and increases the ULV.
  
  
  METHODS
  Twenty-one pigs (25-30 kg) were randomly assigned into 3 groups of 7 pigs each. A solution containing 100 mg (group 100) or 50 mg (group 50) sildenafil citrate or 100 cc saline (group control) was infused intravenously in each pig. A train of 10 S1s was delivered from an RV electrode, and an S2 stimulus was delivered at the peak of the T wave of the last S1 activation to determine the VFT and ULV, before and after drug administration.
  
  
  RESULTS
  The 100 mg sildenafil citrate significantly (P<0.03) decreased VFT, accounting for approximately 36% by peak voltage and approximately 52% by total energy, and significantly (P<0.009) increased ULV, accounting for approximately 28% by peak voltage, and approximately 56% by total energy.
  
  
  CONCLUSIONS
  Supratherapeutic concentrations of sildenafil citrate significantly decreased the VFT and increased the ULV, resulting in an expansion of the VF induction window during the vulnerable period.
authors.affiliation: Cardiac Electrophysiology Unit, Department of Physiology, Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, and Biomedical Engineering Center, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Natnicha
authors.initials: N
authors.lastname: Kanlop
authors.forename: Krekwit
authors.initials: K
authors.lastname: Shinlapawittayatorn
authors.forename: Rattapong
authors.initials: R
authors.lastname: Sungnoon
authors.forename: Siriporn
authors.initials: S
authors.lastname: Chattipakorn
authors.forename: Narissara
authors.initials: N
authors.lastname: Lailerd
authors.forename: Nipon
authors.initials: N
authors.lastname: Chattipakorn
mesh_terms: D000818:Animals; D004554:Electric Countershock; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology; D011897:Random Allocation; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate