How Does Pneumonia Increase the Risk of Heart Disease and Stroke?

Pneumonia is an infection that causes inflammation throughout the body. It may have implications in the form of increased risk from loose plaque breaking off from the walls of blood vessels as a complication and may lead to heart attack or stroke. The relationship between pneumonia and cardiovascular disease is bi-directional: pneumonia increases one's risk of heart disease, while having a history of heart disease can raise the risk of developing pneumonia. Despite its long history of having been considered the domain of lung infections, pneumonia significantly alters the cardiovascular system at every level of severity. Pneumonia also disproportionately affects those populations most likely to be at risk for cardiopulmonary events as well. Recent studies have shown that nearly one quarter of adults admitted to the hospital with pneumonia experience a major acute cardiac event during their hospitalization, resulting in a 60% increase in short-term mortality. These results highlight the potential for enhancing patient outcomes as the care of cardiac complications of pneumonia is improved.

Both pneumonia and cardiovascular disease are among the leading causes of morbidity and mortality throughout the world. Community-acquired pneumonia affects more than 5 million adults, resulting in over 1.1 million hospitalizations and over 60,000 deaths each year in the U.S. Cardiovascular disease affects more than 30 million adults annually in the U.S., leading to 5 million hospitalizations and over 300,000 deaths each year. Similarly, Europe faces comparable burdens of disease. Most of these patients experience both pneumonia and cardiovascular diseases together; for instance, more than half of older adults who are hospitalized with pneumonia also have chronic heart disease-a trend that will only increase with the growing age of the population.

Mechanisms Connecting Pneumonia and Cardiovascular HealthOur current understanding of the cardiovascular response to infections, such as pneumonia, essentially stems from studies on critically ill patients with septic shock. It is characterized by failure of peripheral blood vessels to constrict despite having adequate levels of catecholamines and activation of the renin-angiotensin-aldosterone system. The myocardium also exhibits dysfunction, particularly left ventricular dysfunction, with some degree of myocardial damage that could manifest as a myocardial infarction or cardiogenic shock.

Vulnerability of the Patients with Pre-existing Heart ConditionsPatients with pre-existing heart conditions are at higher risk of having poor prognostic results due to CVD following a diagnosis of pneumonia. Severe pneumonia, regardless of it being caused by a virus or bacteria within hospitalized patients, comorbid heart disease would appear to be a more important factor in mortality than risk factors alone - particularly in patients less than 70 years of age. There likely is more of cardiac complication and myocardial injury with pre-existing CVD. Decomposition of previously existing heart conditions occurs rapidly. Proper management of existing CVD may improve the condition of their pneumonia-related conditions. Identification and intervention of possible arrhythmias and myocardial injury are also important in the cases of those whose heart conditions are already existing.

How Pneumonia Causes Inflammation that Leads to Cardiovascular ImpactPneumonia could potentially be a contributing cause to myocardial dysfunction through several mechanisms, namely, by circulating inflammatory mediators such as cytokines and endotoxins or through direct infection of heart muscle cells by the organisms causing pneumonia and thereby leading to non-ischemic myocardial injury. Acute myocardial ischemia can occasionally present and lead to myocardial infarction, heart failure, or arrhythmias.

Preventive Measures for Individuals with Heart DiseaseVaccination may decrease the incidence of pneumonia complicated by heart disease in patients with heart disease, especially through the flu and pneumococcal vaccines, which patients should be encouraged to receive, especially elderly patients or patients with chronic heart conditions. Because over half of cardiac complications are identified within 24 hours of the onset of pneumonia, it is imperative that healthcare providers carefully evaluate for cardiovascular complications when patients first present with pneumonia. This encompasses examination of established cardiovascular disease and searching for markers of cardiac injury.

Dr Haresh Shah, Consultant Pulmonologist, Bhailal Amin General Hospital, Vadodara