ABSTRACT
Centrifuge high +Gz training has been reported to provoke cardiac arrhythmias in ostensibly healthy individuals, and ECG monitoring of aircrew undergoing such training is recommended for their safety. However, there are few reports about ECG responses during actual high +Gz flight. Therefore, we start this study to determine the ECG responses during actual high +Gzz flight of F-5. In our study, twenty-four pilots, ages 25-37 and one Flight Surgeon were monitored by Holter ECG monitor for four hours, which included periods before, during, and after either a high +Gz or low +Gz flight in a F-5, Actual flight times ranged from 28-78 minutes. Sixteen(16) pilots were monitored in both high +Gz (>5Gz) and low +Gz (<3Gz) flight, the flight surgeon and seven(7) pilots were monitored only in high +Gz flight, one pilot was monitored only in low +Gz flight. Heart rate(HR) and cardiac rhythm were evaluated during a total of 41 flights. During the high +Gz flight, there was one episode of visual black out and dyspnea, three episodes of gray out, and one episode of fatigue. During the low +Gz flight, there were two episodes of coughing. The frequency of occurrence of Ventricular Ectopic Beats (VEs) (Premature Ventricular Contractions (PVCs), especially in-flight VEs(PVCs), was significantly higher in pilots who hart symptoms during the flight as compared to pilots who had no symptoms in one pilot, we recorded 16 VEs (PVCs) over the four houris wlth 10 VEs occurring during the flight. Another pilot experienced 254 Supraventricular ectopic beats (SVEs)(Premature Atrial Contractions (PVCs) or Premature Junctional Contractions (PVCs)) with a total of 87 SVEs recorded during the flight. In high +Gz flight, there were, overall, twelve (12) cases of VEs and fifteen (15) cases of SVEs. In low +Gz flight, there were four (4) cases of VEs anti ten (10) cases of SVEs. In addition, We correlated the HR 30 minutes before flight (range of 52-117 bpm) with maximum in-flight HR (range of 92-178 bpm). We found that the maximum HR during the flight was lower with increased pilot's experience (i.e., age and total flight time). There was no significant difference noted in HR and cardiac arrhythmias when comparing high +Gz and low +Gz flight. During the high +Gz flight, stress may cause symptoms with minor cardiac arrhythmias. Further studies shou1d be done to better correlate the exact relationship and timing between onset of +Gz forces, arrhythmias, and occurrence of adverse clinical symptoms.