New York, Apr 15 (IANS): Breathing heavy wildfire smoke could be harmful to your heart, say researchers, adding that exposure to heavy smoke during recent California wildfires raised the risk of out-of-hospital cardiac arrests up to 70 per cent.

Cardiac arrest occurs when the heart abruptly stops beating properly and can no longer pump blood to vital organs throughout the body. While often referred to interchangeably, cardiac arrest is not the same as a heart attack.

The natural cycle of large-scale wildfires is accelerating and exposing both rural and urban communities to wildfire smoke, according to the study published in the JAHA: Journal of the American Heart Association.

"In recent decades, we experienced a significant increase in large-scale wildfires, therefore, more people are being exposed to wildfire smoke. In order to respond properly, it is important for us to understand the health impacts of wildfire smoke exposure," said study author Ana G.Rappold from the US Environmental Protection Agency's Centre.

For the findings, researchers examined cardiac arrests during 14 wildfire-affected counties in California between 2015 and 2017, using the information submitted to a health registry established by the Centre for Disease Control and Prevention (CDC) and the Cardiac Arrest Registry to Enhance Survival (CARES).

Smoke density exposure was rated as light, medium or heavy according to mapping data from the National Oceanic and Atmospheric Association.

The analysis found that the risk of out-of-hospital cardiac arrests increased among both men and women and in people age 35 and older exposed to heavy smoke.

The cardiac arrest risk also increased in communities with lower socioeconomic status (20 per cent or more people living below the poverty line) with both medium and heavy smoke exposure.

According to the researchers, particulate matter from smoke that is inhaled can penetrate deeply into the lungs, and very small particles may cross into the bloodstream. These particles can create an inflammatory reaction in the lungs and throughout the body.

The body's defence system may react to activate the fight-or-flight system, increasing heart rate, constricting blood vessels and increasing blood pressure.

"These changes can lead to disturbances in the heart's normal rhythm, blockages in blood vessels and other effects creating conditions that could lead to cardiac arrest," Rappold said.

"While other studies have found that older adults are more affected, we also observed elevated effects among middle-aged adults (aged 35-64)," concluded Rappold.