CHICAGO – Pneumonia caused by bacterial infections poses a much greater threat to the heart than pneumonia caused by viral infections, suggests a new study.
Patients in the study diagnosed with bacterial pneumonia had a higher risk of myocardial infarction, stroke or death, compared to patients diagnosed with viral pneumonia, researchers found.
The results were presented today (November 11) at the American Heart Association's annual meeting of Scientific Sessions. The study has not yet been published in a peer-reviewed journal. [27 Devastating Infectious Diseases]
Both bacteria and viruses can cause pneumonia, an infection characterized by inflammation of the lung sac.
In the study, researchers looked at data from 2007 to 2014 in about 4,800 patients at a Utah hospital that had been diagnosed with pneumonia and in hospitals. About 80 percent of patients had been diagnosed with bacterial pneumonia. The researchers then looked at data about those patients during the 90 days after diagnosis, and noted those patients who received heart attack, stroke, heart failure or death. (The researchers tracked the patients for 90 days, as previous research has shown that the risk of these complications increases over 90 days after a diagnosis of pneumonia.)
The researchers found that 34 percent of patients with bacterial pneumonia had a major cardiovascular complication within the 90-day window, compared to 26 percent of patients diagnosed with viral pulmonary inflammation.
So, why can the bacterial version pose a greater threat to the heart? This difference is most likely because bacterial pneumonia causes more inflammation of the arteries – a risk factor for heart disease – than viral pneumonia, says senior author Dr. Joseph Brent Muhlestein, a cardiologist at the Intermountain Heart Institute in Utah.
Bacteria and viruses infect the body in different ways, told Muhlestein for Live Science: Viruses end up in cells and cause damage, while the bacteria are outside the cells and release toxins into the blood. The latter mechanism causes more inflammation in the blood, which can cause damage to the joint in the arteries.
In addition, bacterial pneumonia often causes higher fever, higher levels of inflammatory markers in the blood and high white blood cells, Muhlestein said. (High white blood cells suggest that the body is fighting for an infection.) However, the symptoms of viral and bacterial pneumonia are not all that different – and it is mostly time for doctors that the infection is bacterial and begins to treat the patient with antibiotics, he added.
Nevertheless, Muhlestein noted that he was surprised by the results. Previous research has shown that people with underlying health conditions receiving influenza are much less likely to have a myocardial infarction in the following year compared to those who do not get influenza. "So in my mind, I thought, yes, it may be the viral infections [such as the] influenza [are] worse for cardiac complications than bacterial infections – but that's not what we found. "
In any case, "if you are sick, you should go to the doctor," he said. In fact, the study found that "people who had viral pneumonia still had cardiac complications – just not as many" as people with bacterial pneumonia.
Muhlestein said he also recommends that physicians prescribe antibiotics to patients who are old and have underlying health problems, even if they think the infection is viral. This is because these individuals have a weaker immune system and can easily develop a bacterial infection that can develop into pneumonia, he said.
Originally published it Live Science.