Ischemia and reperfusion-induced arrhythmias: role of hyperoxic preconditioning.
BACKGROUND
Hyperoxic preconditioning is known to protect the heart against necrosis and contractile dysfunction, but protection against arrhythmias has not been well characterized.


OBJECTIVE
The authors hypothesized that pre-exposure to normobaric hyperoxia (H) reduces ischemia and reperfusion-induced arrhythmias in isolated rat hearts.


METHODS
Following 60 and 180 min of hyperoxia treatment, rat hearts were isolated immediately (H60 and H180) or 24 h afterward (H60/24 and H180/24), and subjected to 30 min of regional ischemia followed by 120 min of reperfusion. Occurrence, number, and duration of arrhythmias were analyzed during ischemia and reperfusion. In addition, cardiac infarct size was also assessed.


RESULTS
Sixty and 180 min of breathing hyperoxic gas induced significant protection against severe ischemia and reperfusion-induced arrhythmias. Total number of premature ventricular beats was markedly attenuated by hyperoxia pre-exposure, especially in H60 and H180 groups. Duration of ventricular tachycardia and ventricular fibrillation was also affected by hyperoxia. Hyperoxia reduced the number of ventricular tachycardia episodes in ischemia and reperfusion phase. Accordingly, severity of arrhythmias (arrhythmia score) and infarct size were lower in hyperoxia-treated groups. The effects were more pronounced using hyperoxia immediately before harvesting the heart.


CONCLUSIONS
These results indicate that hyperoxic preconditioning attenuates ventricular ischemia and reperfusion-induced arrhythmias in isolated rat hearts, decreases cardiac infarct size, and improves postischemic heart function. The effects seem to depend on the time course after hyperoxia treatment.
Pourkhalili
Khalil
K
Department of Physiology, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Hajizadeh
Sohrab
S
Tiraihi
Taki
T
Akbari
Zahra
Z
Esmailidehaj
Mansour
M
Bigdeli
Mohammad Reza
MR
Khoshbaten
Ali
A
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control*; D003326:Coronary Circulation / Q000502:physiology; D004195:Disease Models, Animal; D004562:Electrocardiography; D018496:Hyperoxia / Q000150:complications / Q000503:physiopathology*; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D017725:Ventricular Pressure / Q000502:physiology