Author + information
Ventricular premature beats (VPBs) may give important clues for cardiac arrhythmias that can cause hazardous results in aviation by incapacitating the pilot particularly in acute phases of flight (takeoff and landing). Some changes can happen in heart rate variability (HRV) during flight. HRV, representing the beat-to-beat variation in cardiac cycle, is thought to reflect autonomic modulation of the sinus node, namely parasympathetic and sympathetic modulations, and sympathovagal interaction. We compared the HRV parameters of pilots with VPBs detected on ECG to figure out whether there is an association between the flight stresses and autonomic functions of the heart.
43 male pilot (age ranging from 25 to 42) who applied to Turkish Aeromedical Research and and Training Center for their routine examinations and have VPBs detected on surface ECG and because of this underwent 24-hour Holter monitoring were included in this study. All data was retrospectively analyzed and any pilot with cardiovascular disease accompanied was excluded. After obtaining their medical history, all aviators underwent a complete physical examination, chest X-ray, ECG, transthoracic echocardiography (TTE), 24-hour Holter monitoring, CBC and biochemical blood tests. The pilots were divided into 2 groups according to the frequency of VPBs detected on 24-hour Holter monitoring: Group 1: Pilots with rare VPBs, Group 2: Pilots with frequent VPBs. Data was recorded and analyzed automatically by the software of the Holter device. Statistical analyses were done by using SPSS-15 software.
There were no differences in terms of their age, minimum and maximum heart rates, supraventricular extrasystoles but the average heart rate which was found to be lower in group 2. SDNN Indeks, RMSSD and PNN50 parameters were significantly higher in Grup-2. Data of both groups are shown in Table-1.
Exposure to both acceleration forces (G) and anti-G protective maneuvers cause changes in cardiac preload and afterload. Although the heart beats harder and faster to copy with these changes by sympathovagal interaction, chronic +Gz exposure has no effect on cardiac dimensions and structure. But it may have some effects on the SA node and electrical conduction system of the heart. We found lower heart rates, higher SDNN Indeks, RMSSD and PNN50 parameters suggestive of higher risk for incapacitation tendency were found in pilots with frequent VPBs compared to the other group.
|SDNN 24 hour (ms)||153.62±29.75||158.56±35.59||0.778|
|SDANN index (ms)||145.14±40.15||145.63±34.30||0.792|
|SDNN index (ms)||60.76±9.73||69.09±15.69||0.028|
|Min SPH (ms2)||1400.85±852.25||1908.68±1150.16||0.091|
|Max SPH (ms2)||9017.29±4589.98||10554.05±5849.72||0.252|
HR = heart rate, VE = ventricular extrasystole, SDNN = standard deviations of all NN intervals, SDANN = the standard deviation of the average NN intervals calculated over 5 minutes periods, RMSSD = the square root of the mean of the sum of the squares of differences between adjacent NN intervals, PNN50 = the number of pairs of adjacent NN intervals differing by more than 50 ms divided by the total number of all NN intervals, SP24h = 24 hour spectral power, SVE = supraventricular extrasystole, VLF = very low frequency range power (0.003-0.04 Hz), LF = low frequency range power (0.04-0.15 Hz), HF = high frequency range power (0.15-0.40 Hz)