In a new study, researchers found that continuous indoor exposure to second-hand tobacco smoke triggers changes in the heart’s electrical activity, known as cardiac alternans.
It can predict cardiac arrhythmia and sudden cardiac death.
The new study is from UC Davis Health researchers.
The authors believe the study suggests that second-hand smoke exposure alters cells that regulate how the heart beats.
Their work also expands overall knowledge of the effects of tobacco smoke on cardiac function in nonsmokers, something that receives more limited attention in research.
As tobacco use continues to decrease, research on its effects among nonusers also is declining.
Smoking is still a leading cause of preventable illness in the U.S., and bystanders are still exposed to smoking in cars, homes, casinos and when they travel to places with fewer tobacco-smoke protections.
It’s important to continually define the health effects of those unintended exposures.
Unlike previous research, the study is the first to examine cellular changes in heart tissue in response to ambient tobacco smoke.
Another distinction is that it focused on a heart condition other than coronary artery disease (CAD), or plaque buildup and vessel hardening associated with lifestyle and age.
The link between second-hand tobacco smoke and CAD is well established, however, there is little-to-no research on how it influences cellular changes associated with arrhythmia, which may affect individuals with or without CAD.
The study was conducted on mice.
Mice were exposed to secondhand tobacco smoke in a chamber specifically designed to test the health effects associated with inhaled toxins.
The smoke levels were set to be similar to those found in public areas where smokers are present.
Following four, eight and 12 weeks of exposure for six hours a day, five days a week, the animals’ hearts were tested using high-speed imaging and electrocardiograms for changes in electrical activity.
To test susceptibility to arrhythmias, hearts were paced at fast heart rates. They also were tested for levels of calcium, which regulates heart contraction and contributes to abnormal rhythms. The results were compared to the hearts of mice exposed only to filtered air.
The researchers found that hearts from mice exposed to filtered air responded normally, but the hearts from mice exposed to secondhand smoke could not tolerate fast rates, especially at 12 weeks of exposure.
They also found that calcium levels in these hearts did not respond quickly enough, causing beat-to-beat instability, or cardiac alternans.
The high incidence of cardiac alternans is particularly concerning because patients with this condition are at significantly higher risk for arrhythmias and sudden cardiac death.
A better understanding of this underlying pathology and determining whether these changes are reversible if exposure stops are important areas for future study.
The lead author is Crystal Ripplinger, associate professor of pharmacology at UC Davis Health.
The study is published in the journal Environmental Health Perspectives.
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Source: Environmental Health Perspectives.