Researchers have linked low blood calcium levels to an increased risk of sudden cardiac arrest.
Lead investigator Dr. Sumeet S. Chugh, of the Cedars-Sinai Heart Institute in Los Angeles, CA, and colleagues believe that their findings may pave the way for much-needed new diagnostic and treatment strategies for sudden cardiac arrest (SCA).
The researchers recently reported their findings in the journal Mayo Clinic Proceedings.
SCA is when the heart suddenly stops beating. This is due to a malfunction in the heart's electrical activity, which causes an irregular heartbeat, or arrhythmia.
According to the American Heart Association (AHA), around 350,000 out-of-hospital SCAs occur in the U.S. every year, and almost 90 percent of people who experience SCA die as a result.
While coronary heart disease is considered the primary cause of SCA, Dr. Chugh and colleagues note that around half of women and around 70 percent of men who die from SCA have no clinical history of heart disease.
Such statistics highlight the desperate need for ways to identify people who are at increased risk of SCA, as well to find new treatments for the condition. Could the new research from Dr. Chugh and colleagues help to meet this need?
Calcium and SCA risk
The researchers gathered data from the Oregon Sudden Unexpected Death Study. They identified 267 people who experienced SCA between 2002 and 2015, alongside 445 healthy controls.
The blood calcium levels of each subject were measured as part of the study. For SCA patients, these measurements were taken in the 90 days before their cardiac arrest.
Calcium is an essential mineral present in an abundance of foods, primarily dairy products such as milk and cheese.
The team then divided the patients into groups based on their blood calcium levels and looked at whether or not these levels might be associated with the risk of SCA.
The results revealed that the risk of SCA was increased by 2.3-fold for participants who had the lowest blood calcium levels (under 8.95 milligrams per deciliter) compared with those who had the highest blood calcium levels (9.55 milligrams per deciliter).
These results remained after accounting for a number of possible confounding factors, including cardiovascular risk factors, medication use, and demographics.
"This is the first report to show that low serum calcium levels measured close in time to the index event are independently associated with an increased risk of SCA in the general population," says Dr. Hon-Chi Lee, of the Department of Cardiovascular Medicine at the Mayo Clinic in Rochester, MN, in an editorial linked to the study.
Findings may lead to better patient care
The team notes that participants who experienced SCA were more likely to have diabetes, chronic obstructive pulmonary disease, and chronic kidney disease than the controls, and there was a higher percentage of African American subjects in the SCA group.
Dr. Chugh and team say that their findings should be interpreted with caution, and that the link between blood calcium levels and SCA risk should be investigated in future research.
"Overall," concludes Dr. Chugh, "it seems that further study is required to elucidate the mechanisms underlying the adverse associations with lower calcium levels and to determine whether controlling calcium levels improves the prognosis in the general population or in high-risk patients."
However, they believe that their results indicate that low blood calcium levels could be a risk factor for SCA.
"Our study showed that lower serum calcium levels, even within the normal range of values, may increase risk for sudden cardiac death."
First author Dr. Hirad Yarmohammadi, Cedars-Sinai Heart Institute
"Although our findings may not be ready for routine clinical use in patients at this time, they are a step toward the goal of improving patient care by better prediction of risk," Dr. Yarmohammadi adds.