Ventricular arrhythmias and antioxidative medication: experimental study.
BACKGROUND
Reperfusion arrhythmias could be due to free radicals, while contraction excitation feedback is the cause of arrhythmias generated by blood pressure elevation (BPE). The aim of this study was to test the antiarrhythmic effects of an antioxidant (vitamin C [vit C], 1.5 g), an iron-binding agent (deferoxamine [Def], 1 g), and their combination in an experimental model of arrhythmia based on these 2 mechanisms.


METHODS
Thirty anaesthetised sheep were divided into 4 groups, depending on the infused agent: saline (8 sheep), combination of vit C and Def (8), Def (6), and vit C (8). Induction of ventricular arrhythmias was attempted in all animals using both ischaemia-reperfusion (phase I) and a combination of ischaemia and BPE (phase II). In all cases ischaemia was caused by ligating the left anterior descending coronary artery distally to the origin of the 1st diagonal artery, while reperfusion was achieved by releasing the ligation 45 min later. BPE was achieved by obstructing the ascending aorta or by administering intravenous metaraminol. All agents were infused intravenously for 15 min and their administration was started 30 min after the first ligation. Phases I and II lasted 50 and 20 min, respectively.


RESULTS
Ventricular tachycardia/fibrillation (VT/VF) was induced in all animals in the control group (8/8) and in the Def group (6/6). VT/VF appeared in 6/8 of the animals in the vit C group (75%) and in only 3/8 of the animals in the combination therapy group (37.5%). The difference between the combination and control groups was statistically significant (p < 0.03).


CONCLUSIONS
The intravenous administration of vit C and Def in combination protects against VT/VF induced by ischaemia-reperfusion and/or BPE. Administration of Def alone does not appear to help, while the action of vit C alone is not clear.
Intensive Care Unit, University Hospital of Ioannina, Greece. dvardakas@hotmail.com
Aggeliki
A
Karahaliou
Christos
C
Katsouras
Vasileios
V
Koulouras
Dimitrios
D
Nikas
Dimitra
D
Niokou
Georgios
G
Papadopoulos
Georgios
G
Nakos
Dimitrios
D
Sideris
Lambros
L
Michalis
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage*; D001205:Ascorbic Acid / Q000008:administration & dosage*; D003676:Deferoxamine / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects; D007262:Infusions, Intravenous; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000503:physiopathology; D012756:Sheep; D017262:Siderophores / Q000008:administration & dosage; D017180:Tachycardia, Ventricular / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D016896:Treatment Outcome
D000975:Antioxidants; D017262:Siderophores; D003676:Deferoxamine; D001205:Ascorbic Acid