Left ventricular concentric remodeling is highly common among veterans previously deployed to Southwest Asia Theater of Military Operations and associated with impaired exercise performance

Abstract

Background: Environmental factors, such as exposure to airborne hazards, contribute to cardiac remodeling through a variety of mechanisms including direct cardiotoxicity. Left ventricular concentric remodeling (LVCR) is a pathological process of adaptive myocardial change that may represent a precursor state for systolic and diastolic dysfunction and left ventricular hypertrophy. Given that potentially cardiotoxic airborne hazards, such as those produced by open burn pits, have been found to occur in excess in active military combat zones, deployed veterans may be at increased risk for adverse cardiac remodeling, but this has not been thoroughly investigated. Methods: 139 veterans of Southwest Asia Theater of Military Operations underwent transthoracic echocardiography, cardiopulmonary exercise testing (CPET), and health questionnaires. Two-dimensional echocardiography was used to quantify relative wall thickness (RWT) to classify left ventricular (LV) geometry as normal, concentric/eccentric hypertrophy, or LVCR. Observed rates of LVCR were compared to those reported in the Framingham Heart Study, and CPET results were compared between those with and without LVCR. We examined the association between RWT and select CPET outcomes via an adjusted multivariate regression model. Results: The prevalence of LVCR in the veteran sample (30.2%) was elevated compared to the Framingham Heart Study cohort (6-16%). Demographics and risk factors were similar between veterans with LVCR and normal geometry; however, veterans with LVCR had reduced exercise capacity (VO2, 23.7 vs 26.2 ml/kg/min, p<0.05), more inefficient exercise ventilation (VE/V?CO2 nadir: 26.8 vs 25.2, p<0.05), and increased heart rate (HR) reserve (24.7 vs 17.4, p<0.05). RWT was independently associated only with peak HR attained and HR reserve. Conclusions: In our sample of deployed veterans without significant risk factors, the observed rates of LVCR are 2- to 5-fold greater than those reported in a historical civilian cohort. Further, veterans with LVCR also had impaired exercise performance relative to those with normal LV geometry despite otherwise appearing similar. These findings underscore the importance of cardiovascular assessments as part of a dyspnea evaluation for deployed veterans with airborne hazards exposure and raise concerns about their long-term cardiovascular health.