Does military combat-related traumatic injury increase cardiovascular disease risk?

Abstract

Background: Cutting edge battlefield trauma care has allowed military personnel to survive complex injuries that historically would not have been possible. There is largely historical evidence suggesting that combat related traumatic injury (CRTI) is associated with an increased cardiovascular (CV) disease (CVD) risk. However, data from a contemporary military population with CRTI is lacking. Hypotheses: The main hypotheses addressed in this thesis are: 1. Military servicemen who have had suffered severe CRTI with limb amputations have increased arterial stiffness compared to those less severely injured and non-injured servicemen. 2. Combat-related traumatic amputation is associated with greater vascular inflammation and a more adverse lipid profile than that observed with less severe combat related injuries and with non-injured servicemen exposed to the same operational environment. Methods: This was a cross-sectional observational study that included the first 699 male British military personnel who took part in the ongoing ADVANCE (ArmeD SerVices TrAuma RehabilitatioN OutComE) study project. CRTI veterans with limb amputations (CRTI-A, n=105) and CRTI veterans without limb amputations (CRTI-NA, n=200) were compared with a frequency-matched healthy control population (n=394) of servicemen of similar age and operational exposure (Afghanistan 2003-14). Fasting serum lipids, glucose and Hs-CRP levels were measured using venous blood. Arterial stiffness (expressed as central [AIx] and peripheral [pAI] Augmentation Index), pulse wave velocity (PWV), brachial and central aortic blood pressure, subendocardial viability ratio (SEVR), an indirect marker of myocardial blood perfusion, were measured using the Vicorder device. Injury severity was determined using the New Injury Severity Score (NISS) and the association of injury severity score and CVD risk profile was assessed. Results: The mean age was 33.9 (± 5.40) [range 23-60] years with the time from injury or deployment to examination averaging 90.4 (± 20.99) months. The NISS were higher in the CRTI-A vs CRT-NA vs control 36.75 (± 18.01) vs 20.11 (± 17.9) vs 0; p<0.001 respectively. Resting heart rate (minute-1) was significantly higher amongst those with CRTI-A, 63.67 ( ± 12.53) vs CRTI-NA group 58.35 (± 9.41) and, healthy controls 56.39 (± 9.24); p<0.001, with no significant difference in respective HDL Cholesterol levels 1.120 (± 0.27) vs 1.249 (± 0.33) vs 1.252 (± 0.27) mmol/l; p<0.001. PWV, AIx or central blood pressure. The SEVR values, 194.0 (± 43.32) vs 201.3 (± 45.07) vs 208.5 (± 63.04); p=0.0101) respectively, were significantly lower whereas Hs-CRP, 2.60 (± 3.81)mg/l vs 1.96 (± 2.68)mg/l vs 1.44 (± 1.69)mg/l; p=0.0166 respectively and total cholesterol/HDL ratio 4.49 (±1.25) vs 4.31 (±1.82) vs 4.19 (±1.48); p=0.012, respectively, were significantly greater among the CRTI-A compared with the CRTI-NA and healthy controls. These differences were most marked with proximal bilateral amputations. Conclusion: Servicemen who have sustained severe CRTI-A have a worse CVD risk profile with evidence of greater vascular inflammation and a more adverse lipid profile than those without amputations or injury. However, there was no significant difference in arterial stiffness. These findings confirm the need for a long-term cohort study to assess whether these differences in risk profile will translate into meaningful variance in CVD outcomes.