Low serum calcium may increase risk of sudden cardiac arrest

Findings of a new study published in Mayo Clinic Proceedings have potential implications for mechanisms as well as prevention of SCA


Rochester, MN, October 5, 2017

Sudden cardiac arrest (SCA) is fatal for over 90% of patients, and more than half of men and close to 70% of women who die of SCA have no clinical history of heart disease prior to this cardiac event. It is one of the leading causes of death in the United States and kills more people than any single cancer. Many patients who suffer SCA would not be considered high risk under current guidelines. These sobering facts drive the search for simple and relatively inexpensive ways to identify individuals at higher risk for SCA. In a study in Mayo Clinic Proceedings, researchers found that individuals with lower levels of calcium in the blood, which is easily monitored, are more likely to experience SCA than those with higher calcium levels.

“Our study found that serum calcium levels were lower in individuals who had a sudden cardiac arrest than in a control group. Patients with serum calcium in the lowest quartile (<8.95 mg/dL) had twice the odds of sudden cardiac arrest compared to those in the highest quartile (>9.55 mg/dL), even after controlling for multiple patient characteristics including demographics, cardiovascular risk factors and comorbidities, and medication use,” explained lead investigator Sumeet S. Chugh, MD, Pauline and Harold Price Chair in Cardiac Electrophysiology, Cedars-Sinai Heart Institute, Los Angeles, CA.

Data from 2002 until 2015 were gathered from the Oregon Sudden Unexpected Death Study (Oregon SUDS). The goal of the Oregon SUDS is to improve understanding of who is at risk for out-of-hospital sudden cardiac arrest. This study included 267 SCA cases and 445 control subjects from the same community whose serum calcium levels were measured during routine medical care. All SCA cases had had serum calcium levels measured in the 90 days prior to their cardiac arrest. The Oregon SUDS collaborates with emergency responders and hospitals in the Portland, OR metro area to identify all cases of sudden cardiac arrest. This enabled researchers to collect comprehensive patient medical history from the time prior to their cardiac arrest.

Each patient’s total serum calcium was corrected by their serum albumin level to estimate a more physiologically relevant corrected calcium level.

Sudden cardiac arrest cases had lower corrected calcium levels than control subjects did (9.18 mg/dL vs. 9.27 mg/dL).

SCA cases had a significantly higher percentage of African Americans and patients with diabetes mellitus, chronic obstructive pulmonary disease, and chronic kidney disease compared to the control group. Cases were also more likely than controls to be on hemodialysis. In addition, diuretics, especially loop diuretics, were prescribed more for cases than for controls with no differences in the rate of utilization of beta blockers.

“Overall, 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,” commented Dr. Chugh.

First author Hirad Yarmohammadi, MD, MPH, postdoctoral fellow at Cedars-Sinai, currently training in the Cardiovascular Division, Brigham and Women’s Hospital, Boston, MA, said: “Our study showed that lower serum calcium levels, even within the normal range of values, may increase risk for sudden cardiac death. Although our findings may not be ready for routine clinical use in patients at this time, they are a step towards the goal of improving patient care by better prediction of risk.”

In an accompanying editorial, Hon-Chi Lee, MD, PhD, of the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, noted, “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.”

While these results should be interpreted with caution, Dr. Lee recommends that (1) serum calcium levels should be examined and followed longitudinally more carefully, (2) low serum calcium levels may be considered a potential risk factor for SCA in the community, and (3) more research is necessary to determine whether patients in the lowest quartile of serum calcium would benefit from higher dietary calcium intake or calcium supplementation.

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Notes for Editors
The articles are “Serum Calcium and Risk of Sudden Cardiac Arrest in the General Population,” by Hirad Yarmohammadi, MD, MPH; Audrey Uy-Evanado, MD; Kyndaron Reinier, PhD, MPH; Carmen Rusinaru, MD, PhD; Harpriya Chugh, BS; Jonathan Jui, MD, MPH; and Sumeet S. Chugh, MD (http://dx.doi.org/10.1016/j.mayocp.2017.05.028) and “Serum Calcium: A Sudden Cardiac Arrest Risk Factor,” by Hon-Chi Lee, MD, PhD (http://dx.doi.org/10.1016/j.mayocp.2017.08.014). They appear inMayo Clinic Proceedings,volume 92, issue 10 (October 2017) published by Elsevier.

An accompanying video is available at https://youtu.be/G2ghNOmZQ7I.

The study was funded in part by National Heart Lung and Blood Institute grants R01HL122492 and R01HL126938 to Dr Chugh.

Full text of these articles is available to credentialed journalists upon request. Contact Rachael Zaleski at +1 215-239-3658 or mcpmedia@elsevier.com to obtain copies. Journalists wishing to interview the authors of the study should contact Sumeet S. Chugh, MD, at +1 310-423-1206; Sumeet.Chugh@cshs.org or Sally Stewart, Associate Director of Media Relations at Cedars-Sinai at +1 310-248-6566; Sally.stewart@cshs.org. Hon-Chi Lee may be reached for comment at lee.honchi@mayo.edu.

About Mayo Clinic Proceedings
The flagship journal of Mayo Clinic and one of the premier peer-reviewed clinical journals in general medicine, Mayo Clinic Proceedings is among the most widely read and highly cited scientific publications for physicians, with a circulation of approximately 125,000. While the Journal is sponsored by Mayo Clinic, it welcomes submissions from authors worldwide, publishing articles that focus on clinical medicine and support the professional and educational needs of its readers. www.mayoclinicproceedings.org

About Mayo Clinic
Mayo Clinic is a nonprofit worldwide leader in medical care, research, and education for people from all walks of life. For more information visit www.mayoclinic.org/about and www.mayoclinic.org/news.

About Elsevier
Elsevier is a global information analytics business that helps institutions and professionals progress science, advance healthcare and improve performance for the benefit of humanity. Elsevier provides digital solutions and tools in the areas of strategic research management, R&D performance, clinical decision support, and professional education; including ScienceDirect, Scopus, SciVal, ClinicalKey and Sherpath. Elsevier publishes over 2,500 digitized journals, including The Lancet and Cell, more than 35,000 e-book titles and many iconic reference works, including Gray's Anatomy. Elsevier is part of RELX Group, a global provider of information and analytics for professionals and business customers across industries. www.elsevier.com

Rachael Zaleski
Elsevier
+1 215-239-3658
mcpmedia@elsevier.com