Arrhythmias observed during high-G training: proposed training safety criterion.

INTRODUCTION: Most arrhythmias during centrifuge training are physiological responses to high +Gz stress. However, potentially dangerous arrhythmias occasionally occur during centrifuge training. We reviewed all arrhythmias recorded during the Japan Air Self-Defense Force (JASDF) centrifuge training from April 2001 to March 2003, and developed a criterion for suspending G-training based on observed arrhythmias.
METHOD: There were 195 male fighter pilots who received high-G centrifuge training monitored with electrocardiographs (ECGs). We evaluated types and occurrences of all arrhythmias during high-G training over a 24-mo period.
RESULTS: Sinus arrhythmia (48.7%), single premature atrial contraction (32.3%), and single (58.5%) or paired (9.7%) premature ventricular contraction were commonly occurring arrhythmias during high-G training. We considered these arrhythmias as variant physiological responses to high-G training (category 1). In addition, we observed ventricular tachycardia (2.6%), paroxysmal supraventricular tachycardia (1.5%), and paroxysmal atrial fibrillation (0.5%). Further investigation of these trainees revealed a significant proportion with cardiac anomalies. As a result, the JASDF currently categorizes these arrhythmias as indicators to suspend G-training and initiate cardiac workup (category 3). Other arrhythmias, such as non-sustained ventricular tachycardia (VT) or Morbitz type I atrioventricular (AV) block, were considered borderline anomalies; whether training was allowed to continue depended on the decision of the physicians monitoring the training (category 2).
CONCLUSION: Routine ECG monitoring during centrifuge training is recommended to catch the pathology underlying dangerous arrhythmias for flight safety. Our proposed criterion for stopping the centrifuge is intended to differentiate between serious arrhythmias and arrhythmias of physiologic response.