title: Sum of effects of myocardial ischemia followed by electrically induced tachycardia on myocardial function.
abstract: BACKGROUND
  The alteration of contractile function after tachyarrhythmia ceases is influenced by the type of prior ischemia (acute coronary syndrome or ischemia inherent in a coronary revascularization procedure). We aimed to analyze cardiac dysfunction in an acute experimental model of supraphysiological heart rate preceded by different durations and types of ischemia.
  
  
  METHODS
  Twenty-four pigs were included in: (S1) series of ventricular pacing; (S2, A and B) series with 10 or 20 min, respectively, of coronary occlusion previous to ventricular pacing; S3 with 20 brief, repeated ischemia/reperfusion processes prior to ventricular pacing and; (S4) control series. Overall cardiac function parameters and regional myocardial contractility at the apex and base of the left ventricle were recorded, as were oxidative stress markers (glutathione and lipid peroxide serum levels). Left ventricular pacing at 60% over baseline heart rate was performed for 2 h followed by 1 h of recovery.
  
  
  RESULTS
  High ventricular pacing rates preceded by short, repeated periods of coronary ischemia/reperfusion resulted in worse impairment of overall cardiac and regional function that continued to be altered 1 h after tachycardia ceased. There was significant reduction of stroke volume (26.9 ± 5.3 basal vs. 16 ± 6.2 ml; p<0.05), LVP; dP/dt and LAD flow (13.1 ± 1.5 basal vs. 8.4 ± 1.6 ml/min; p<0.05); the base contractility remained altered when recovering compared to baseline (base SF: 5.6 ± 2.8 vs. 2.2 ± 0.7%; p<0.05); and LPO levels were higher than less aggressive series at the end of recovery.
  
  
  CONCLUSIONS
  Ischemia and tachycardia accumulate their effects, with increased cardiac involvement depending on the type of ischemia.
authors.affiliation: Servicio de Cardiología, Hospital Dr. Peset Aleixandre, Valencia, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Díez
authors.forename: Amparo
authors.initials: A
authors.lastname: Hernandiz
authors.forename: Juan
authors.initials: J
authors.lastname: Cosín-Aguilar
authors.forename: Amparo
authors.initials: A
authors.lastname: Aguilar
authors.forename: Manuel
authors.initials: M
authors.lastname: Portolés
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D054059:Coronary Occlusion / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D055724:Electrophysiological Phenomena; D005260:Female; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D009206:Myocardium / Q000473:pathology*; D018384:Oxidative Stress; D034421:Sus scrofa; D013599:Systole / Q000502:physiology; D013610:Tachycardia / Q000150:complications / Q000473:pathology / Q000503:physiopathology*