Breast Cancer and Atrial Fibrillation

By Kayla MatthewsReviewed by Dr. Mary Cooke, Ph.D.

Atrial fibrillation (AFib) is a common heart rhythm problem whereby the heart's two upper chambers, the atria, squeeze out of sync and often rapidly.

Image Credit: Lightspring/Shutterstock.com

This causes the heart's walls to quiver. Numerous factors, such as age, high blood pressure, overactive thyroid, and viral infections can put people at a higher risk for developing atrial fibrillation.

Sometimes doctors are unable to identify the cause. However, research suggests that people diagnosed with breast cancer may be at a higher risk for developing AFib than other groups of patients. Here are some things to know about the possible link between breast cancer and atrial fibrillation.

Chemotherapy Treatments Make AFib More Likely

One of the necessities following a breast cancer diagnosis is for the patient and treatment team to come up with a plan for tackling the disease in ways that are as safe and effective as possible. Discussing the possible ramifications of a type of treatment with patients beforehand is essential. Then, they can determine whether the treatment is worth the risks it brings.

A 2019 cohort study of 68,113 women diagnosed with early-stage breast cancer and 204,440 age-matched controls without cancer found that people in the first group developed atrial fibrillation at a higher rate than the people who did not have cancer.

Interestingly, though, the likelihood was only higher in the first year following the diagnosis and periods later than five years after it, but not in the intervening years. Furthermore, the researchers found a connection between chemotherapy treatments and AFib.

They also looked to see if chemotherapy treatments with anthracyclines or trastuzumab (both of which are cardiotoxic agents) elevated the atrial fibrillation risk. However, the results showed that such exposures did not make AFib more likely to happen.

The researchers clarified that the relative rate of AFib was higher in patients with Stage III breast cancer. However, when looking at the results for all breast cancer patients in the study, they found that the increase in AFib incidences was small, particularly after taking competing risks into account. These results suggest that physicians should inform their patients of this risk to prepare them for the possibility of facing it.

A Patient's Age Could Impact the Likelihood of AFib Onset Timeframes

Millions of women in the U.S. are receiving treatment for breast cancer now or have in the past. People understandably wonder which factors make them more or less at risk for this kind of cancer so they can do everything possible to stay healthy. Health professionals know that most breast cancer cases occur in women who are 50 or over, meaning age is a factor.

A 2019 Danish study showed that age may also be a factor concerning breast cancer and atrial fibrillation. They observed that AFib was more likely to happen in patients with breast cancer than those without it due to the systemic inflammation caused by the disease, as well as treatment side effects.

Age also played a role in the long-term incidence of atrial fibrillation. The researchers used national registries to find 74,155 people who received breast cancer diagnoses from 1998 to 2015, plus 222,465 people from the general population who did not have breast cancer.

The results were similar to the previous study mentioned here, whereby the risk of AFib was elevated during certain periods. In patients who were older than 60, atrial fibrillation was more likely to occur from six months to three years after their diagnoses. However, patients who were younger than 60 were only more likely to experience AFib within six months of being diagnosed.

These findings highlight the importance of explaining to patients that their age may impact the side effects of breast cancer that they experience, specifically related to AFib in this case. Physicians may want to inform people of the side effects of AFib, which include heartbeat irregularities such as "flip-flopping" feelings in the chest, a racing pulse, a reduced ability to exercise and shortness of breath.

The AFib Connection Spans Beyond Breast Cancer

Researchers have determined that the increased risk of atrial fibrillation and cancer is not restricted to the breast. A meta-analysis published in 2019 examined five studies and 5,889,234 subjects.

It found that patients diagnosed with solid cancers — as opposed to cancers affecting the blood, like leukemia — were more likely to experience AFib than cancer-free patients.

It also concluded that the risk was highest within the first 90 days of diagnosis. This analysis examined the incidences of atrial fibrillation in patients with colorectal cancer as well as cancers of the breast, prostate, and lung.

After examining the pooled data from all of the chosen studies, the results showed that breast cancer patients were nearly twice as likely to experience atrial fibrillation than those without the disease.

Then, for all kinds of cancers about this study, the risk of atrial fibrillation ceased to be significant after a year from the point of diagnosis. The results of this study contradict some of the other findings in the research mentioned here.

Thus, physicians may consider discussing the side effects of AFib with all breast cancer patients regardless of age or when the diagnosis happened.

Reasons to Show an Interest in Oncocardiology

Oncocardiology is an emerging clinical medicine field that looks for links between cancer and cardiovascular problems.

The evidence here showing the link between breast cancer and atrial fibrillation gives medical professionals a reason to stay informed about developments in that field, as well as monitor their patients for cardiovascular issues during their cancer treatments and any follow-up appointments once remission occurs.

Further Reading

• All Cancer Content
• What is Cancer?
• What Causes Cancer?
• Cancer Glossary
• Transforming Cancer Care through Genomic Testing