Doctors have long known that patients who are hospitalized with pneumonia have a higher risk of a heart attack while they’re in the hospital. Most patients who have a heart attack after being hospitalized for pneumonia do so after following a disease progression marked by such warning signs as inflammatory response syndrome and multiple organ failure. Some patients, however, deteriorate more quickly.
And some patients don’t develop cardiovascular disease for weeks, months, or years after their release from the hospital, according to the results of a new study published in JAMA, the Journal of the American Medical Association. In fact, you’re more likely to develop cardiovascular disease up to 10 years after being hospitalized with pneumonia. Researchers at the University of Texas believe that the bacteria that cause pneumonia also penetrate the heart muscle, weakening it and leaving it weakened even after antibiotics have successfully treated the disease.
Pneumonia Raises Heart Disease Risk
For the JAMA study, researchers examined the health records of 3,813 people with no history of heart disease and no heart disease risk factors other than having had pneumonia. The researchers obtained these records from a pair of community health studies performed in the United States. Participants of one of the studies were 65 years old or older while participants of the other were 45 to 64 years old. 1,271 of the study participants had had pneumonia, while 2,542 had not — that group formed the control.
For the purposes of the study, the researchers looked at heart disease rates over a 10-year period. They found that those who had been treated for pneumonia had the highest risk of heart disease, and that their risk was greatest within the first year after being treated for pneumonia. Among the 65-or-older group, pneumonia patients were four times more likely to be diagnosed with heart disease within the first month of being infected with pneumonia. By year 10, members of the 65-and-older group were about twice as likely as similarly-aged members of the control group to develop heart disease. Among the 65-and-older group, pneumonia compounded the risk of heart disease from other known risk factors, like smoking or high blood pressure.
For members of the 45-to-64 group, the risk of heart disease from pneumonia was slightly lower. The researchers found that members of this group demonstrated a higher risk of heart disease in the first two years following pneumonia diagnosis, and were 2.4 times more likely to be diagnosed with heart disease in the first three months after pneumonia infection. After the first two years, however, the younger group’s risk of heart disease dropped back down to nearly normal. The results of this study suggest that pneumonia itself is a risk factor for heart disease and cardiac arrest, and that patients who have had pneumonia might benefit from the use of heart attack preventatives like Plavix. For those who haven’t yet had pneumonia, flu and pneumonia vaccines may prevent both pneumonia and heart disease.
How Pneumonia Damages the Heart
The results of a 2014 study published by researchers with the University of Texas suggest that Streptococcus pneumoniae, the bacteria responsible for the majority of bacterial pneumonia infections, also damages the heart by destroying heart muscle tissue. Upon examining the blood of mice infected with S. pneumoniae, the researchers discovered high levels of the protein complex troponin, which indicates injury to the heart muscle. When the researchers measured the mice’s heart function using EKGs, they found the animals’ hearts to be functioning abnormally. Examination of the heart muscles themselves revealed that the muscles were riddled with microlesions, microscopic wounds that marked where the S. pneumoniae bacteria had invaded the heart muscle and multiplied within it. The researchers also realized that tissue surrounding these injured areas was also dying.
The researchers believe that the toxin pneumolysin, released by the S. pneumoniae bacteria, killed the mice’s heart muscle cells. When the researchers examined the hearts of humans and rhesus macaques that had died from bacterial pneumonia after receiving antibiotic treatment, they discovered similar muscular injuries – but this time, they didn’t find any evidence of S. pneumoniae infection within the lesions. The researchers surmised that the antibiotic treatment had killed off the bacteria infecting the heart muscles of the humans and monkeys.
Their speculation was proved correct when they administered antibiotic treatment to mice infected with pneumonia and found that in these animals, too, the heart muscle lesions were present after treatment, but lacked any trace of bacterial infection. The researchers believe that ampicillin, a potent antibiotic used to treat bacterial pneumonia, may contribute to heart injury in patients with pneumonia because of the way it breaks down bacterial cell walls, causing them to release even more pneumolysin toxin into the heart cells. They believe that using an alternative antibiotic to treat pneumonia may help prevent damage to the heart muscle.
Bacterial pneumonia is a serious lung infection that has been known to cause cardiovascular disease and cardiac arrest. Now, researchers know that’s because the bacteria that cause pneumonia can spread to the heart muscle, weakening it. The effects of pneumonia infection on the heart can last for years, especially in older patients. If you haven’t had your flu vaccine or pneumonia vaccine, you may want to consider getting it, especially if you’re over 65. Vaccination is the best way to prevent pneumonia and pneumonia-related heart disease.