BackgroundPrevious studies have found particulate matter (PM) < 2.5 μm in aerodynamic diameter (PM2.5) associated with heart disease mortality. Although rapid effects of PM2.5 exposure on the cardiovascular system have been proposed, few studies have investigated the effect of short-term exposures on out-of-hospital cardiac arrest (OHCA).ObjectivesWe aimed to determine whether short-term PM2.5 exposures increased the risk of OHCA and whether risk depended on subject characteristics or presenting heart rhythm.MethodsA case–crossover analysis determined hazard ratios (HRs) for OHCAs logged by emergency medical systems (EMS) versus hourly and daily PM2.5 exposures at the time of the OHCA and for daily and hourly periods before it.ResultsFor all OHCAs (n = 1,374), exposures on the day of the arrest or 1–3 days before arrest had no significant effect on the incidence of OHCA. For cardiac arrests witnessed by bystanders (n = 511), OHCA risk significantly increased with PM2.5 exposure during the hour of the arrest (HR for a 10-μg/m3 increase in PM2.5 exposure = 1.12; 95% confidence interval, 1.01–1.25). For the subsets of subjects who were white, 60–75 years of age, or presented with asystole, OHCA risk significantly increased with PM2.5 during the hour of the arrest (HRs for a 10-μg/m3 increase in PM2.5 = 1.18, 1.25, or 1.22, respectively; p < 0.05). HR generally decreased as the time lag between PM2.5 exposure and OHCA increased.ConclusionThe results suggest an acute effect of short-term PM2.5 exposure in precipitating OHCAs, and a need to investigate further the role of subject factors in the effects of PM on the risk of OHCA.

There is a need for replacement heart valves that can grow with children. We fabricated tubes of fibroblast-derived collagenous matrix that have been shown to regenerate and grow as a pulmonary artery replacement in lambs and implemented a design for a valved conduit consisting of three tubes sewn together. Seven lambs were implanted with tri-tube valved conduits in sequential cohorts and compared to bioprosthetic conduits. Valves implanted into the pulmonary artery of two lambs of the first cohort of four animals functioned with mild regurgitation and systolic pressure drops <10 mmHg up to 52 weeks after implantation, during which the valve diameter increased from 19 mm to a physiologically normal ~25 mm. In a second cohort, the valve design was modified to include an additional tube, creating a sleeve around the tri-tube valve to counteract faster root growth relative to the leaflets. Two valves exhibited trivial-to-mild regurgitation at 52 weeks with similar diameter increases to ~25 mm and systolic pressure drops of <5 mmHg, whereas the third valve showed similar findings until moderate regurgitation was observed at 52 weeks, correlating to hyperincrease in the valve diameter. In all explanted valves, the leaflets contained interstitial cells and an endothelium progressing from the base of the leaflets and remained thin and pliable with sparse, punctate microcalcifications. The tri-tube valves demonstrated reduced calcification and improved hemodynamic function compared to clinically used pediatric bioprosthetic valves tested in the same model. This tri-tube valved conduit has potential for long-term valve growth in children.

Firefighters are subject to extreme environments and high physical demands when performing duty-related tasks. Recently, physiological status monitors (PSM) have been embedded into a compression shirt to enable firefighters to measure, visualize, log, and transmit vital metrics such as heart rate (HR) to aid in cardiovascular risk identification and mitigation, thereby attempting to improve the health, fitness, and safety of this population. The purpose of this study was to validate HR recorded by the PSM-embedded compression shirt against a criterion standard laboratory ECG-derived HR when worn concurrently with structural firefighting personal protective equipment (PPE) during four simulated firefighting activities. Ten healthy, college-age men (mean ± SD: age: 21 ± 1 yr; body mass: 91 ± 10 kg; body mass index: 26.9 ± 3.1 kg/m(2)) completed four tasks that are routinely performed during firefighting operations: outdoor fast-paced walking (FW), treadmill walking (TW), searching/crawling (SC), and ascending/descending stairs (AD). They wore the PSM-embedded compression shirt under structural firefighting PPE. HR was recorded concurrently by the PSM-embedded compression shirt and a portable metabolic measurement system accompanied with a standard 12-lead electrocardiograph that was used to provide criterion measures of HR. For all four tasks combined there was very high correlation of PSM and ECG HR (r > 0.99; SEE 0.84 /min) with a mean difference (bias) of -0.02 /min and limits of agreement of -0.07 to 0.02 /min. For individual tasks, the correlations were also high (r-values = 0.99; SEE 0.81-0.89). The mean bias (limits of agreement) was: FW 0.03 (-0.09 to 0.14); TW 0.04 (-0.05 to 0.12); SC -0.01 (-0.12 to 0.10); AD -0.13 (-0.21 to -0.04) /min. These findings demonstrate that the PSM-embedded compression shirt provides a valid measure of HR during simulated firefighting activities when compared with a standard 12-lead ECG.

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