Non-Invasive Identification of Left Ventricular Hypertrophy (LVH)/ Cardiomegaly in US Firefighters

Background: Cardiovascular disease (CVD) causes 45% of firefighters’ on-duty deaths, but the risk of these events is limited to susceptible individuals. Left ventricular hypertrophy (LVH)/cardiomegaly increases arrhythmia, myocardial infarction, stroke and death risks, and is a condition which renders firefighters susceptible to CVD events. Autopsies demonstrate LVH/cardiomegaly in most firefighter CVD fatalities. If recognized beforehand, however, effective treatments are available. In this work we i) describe the state of the art knowledge on the definition of cardiac enlargement across imaging modalities, normalization techniques (indices) and reference ranges; ii) estimate the current prevalence of cardiac enlargement among the US firefighters; and iii) identify the significant predictors of LV mass (LVM). Methods: We conducted a literature review to compare measurements for heart size and mass by cardiac MRI (CMR), Echocardiograms (ECHO) and autopsies in healthy and diseased hearts in the general population (Chapter 1). We selected 400 participants by an enriched randomization sampling strategy from a population of active firefighters. All participants received a screening ECHO, followed by CMR. Prevalence estimates for LVH were derived among the active firefighters based on ECHO and CMR. Separate estimates were made by examining autopsies of other firefighters who suffered a noncardiac on-duty fatality (Chapter 2). Risk factors were evaluated as predictors for LVM normalized for height (Chapter 3). Results: The findings from Chapter 1 demonstrated a wide variance in LVH definitions and reference ranges; ECHO remains the most widely used diagnostic tool; and few direct comparisons exist between imaging and autopsies studies at this time. Chapter 2 showed a wide range of prevalence estimates of cardiac enlargement and body mass index (BMI) to be a major driver of heart weight. Chapter 3 identified BMI as the most significant and only consistent independent predictor of LVM indices. Conclusions: Standardization of cardiac enlargement definitions is needed. However, BMI drives LVM, heart weight and LV wall thickness. Therefore, reducing obesity will decrease the prevalence of LVH/cardiac enlargement in the fire service, which should in turn reduce CVD events.