PHILADELPHIA – Out-of-hospital cardiac arrests spike with daily counts of emissions-related particulate matter – a key contributor to urban smog – and particularly affect men and people older than age 75, according to results of a nationwide Japanese study presented at the American Heart Association scientific sessions.
“Short-term exposure to particulate pollutants is a potential trigger for cardiac-origin, out-of-hospital cardiac arrest [OHCA] onset in Japan,” said Sunao Kojima, MD, a professor at Kawasaki Medical School in Kurashiki, Japan.
The study used the All-Japan Utstein Registry of OHCA throughout all 47 prefectures in Japan. The analysis then applied prefecture-specific estimates of PM2.5 – particulate matter that measures 2.5 mcm in average diameter – using a time-stratified, case-crossover design. By comparison, PM2.5 is about 1/40th the diameter of human hair (approximately 100 mcm) and about 1/12th that of cedar pollen (30 mcm).
“Increased OHCAs incidence correlated with the average increase in PM2.5 concentrations over those observed 1 day before cardiac arrest,” Dr. Kojima said.
What’s noteworthy about the Utstein registry, Dr. Kojima said, is that emergency medical service personnel in Japan are not authorized to terminate resuscitation efforts, so most OHCA patients are transported to the nearest hospital and are thus counted in the registry.
From a total count of 1.4 million EMS-assessed OHCAs from 2005 through 2016, the study focused on 103,189 bystander-witnessed events from April 2011 through 2016. The analysis further divided that population into three groups: those presenting with initial ventricular fibrillation/pulseless ventricular tachycardia (20,848); those without initial VF/pulseless VT (80,110); and those with initial cardiac rhythm of unknown origin (2,231).
“The pathways linking PM2.5 exposure with OHCA remain unknown, but several mechanisms have been suspected,” Dr. Kojima said. “A major mechanism is thought to be associated with oxidative stress and systemic inflammation.”
The average daily concentration for PM2.5 was 13.9/m3 across all of Japan, Dr. Kojima said, with the highest concentrations in western Japan (16.3/m3). A 10-mcg/m3 increase in the average PM2.5 concentrations on the day of OHCA from the previous day (lag 0-1) was associated with a 1.6% increase in OHCAs (95% confidence interval, 0.1-3.1%), he said.
“Increased PM2.5 concentrations were closely associated with OHCA incidence, even when adjusted for other pollutants, such as ozone, nitrogen dioxide, sulfur dioxide, and lag 0-1,” Dr. Kojima said.
The incidence for PM2.5-related OHCA was higher for people age 75 and older and for men, during the warm season and in the central region. In the central region, the incidence increased around 6% for every 10-mcg/m3 day-to-day increase in the average PM2.5 compared to less than 1% increases in the eastern and western regions, Dr. Kojima said.
PM2.5 levels also seemed to influence outcomes depending on the origin of the OHCA, he said. Patients with VF/pulseless VT and pulseless electrical activity had better outcomes than did those with asystole. Increased PM2.5 levels were linked with lower rates of restoration of spontaneous circulation, 1-month survival, and 1-month survival with minimal neurological impairment, he said. Patients who had chest-compression-only CPR seemed to do significantly better than did those who had chest compression with rescue breathing, he said.
“There may be room for further discussion regarding the impact of performing rescue breathing in CPR and the consequent effects of short-term PM2.5 exposure on patients with cardiac origin,” he said.
Dr. Kojima has no financial relationships to disclose. The study received funding from the Japan Ministry of the Environment, Japan Society for the Promotion of Science, and Foundation for Total Health Promotion, Japan.
SOURCE: Kojima S. AHA 2019, .