Zika also may have serious effects on the heart, new research shows in the first study to report cardiovascular complications related to this virus, according to data being presented at the American College of Cardiology’s 66th Annual Scientific Session.

In a study at the Institute of Tropical Medicine in Caracas, Venezuela, of nine adult patients with Zika and no previous history of cardiovascular disease, all but one developed a heart rhythm problem and two–thirds had evidence of heart failure.

“We know that other mosquito–borne diseases, such as dengue fever and chikungunya virus, can affect the heart, so we thought we might see the same with Zika. But we were surprised by the severity, even in this small number of patients,” says Karina Gonzalez Carta, MD, cardiologist and research fellow at Mayo Clinic and the study’s lead author.

The patients (six were female, and mean age was 47) were seen at the Department of Tropical Medicine in Venezuela within two weeks of having Zika–type symptoms. They reported symptoms of heart problems, most commonly palpitations followed by shortness of breath and fatigue. Only one patient had any previous cardiovascular problems (high blood pressure), and tests confirmed that all of the patients had active Zika infection. Patients underwent an initial electrocardiogram (EKG), a test that shows the electrical activity of the heart, and in eight of the patients, the EKG suggested heartbeat rate or rhythm concerns. These findings prompted a full cardiovascular workup using an echocardiogram, (24–hour) Holter monitor and a cardiac MRI study.

Serious arrhythmias were detected in eight patients: three cases of atrial fibrillation, two cases of nonsustained atrial tachycardia and two cases of ventricular arrhythmias. Heart failure was present in six cases. Of these, five patients had heart failure with low ejection fraction, when the heart muscle doesn't pump blood as well as it should, and one had heart failure with preserved ejection fraction, when the heart becomes stiff and cannot relax or fill properly.

The patients have been followed since July 2016, and none of their cardiac issues have resolved, but symptoms have improved following treatment for heart failure or atrial fibrillation, Dr. Carta says.

“Following this research, we want patients who are suffering from Zika symptoms also to be aware of the cardiac symptoms because they might not connect the two,” Dr. Carta says. “The same is true for physicians because they might be focused on the Zika symptoms but not thinking about cardiac concerns.”

Dr. Carta will present the study, “Myocarditis, Heart Failure and Arrhythmias in Patients With Zika.”