Vicente Corrales-Medina and colleagues report estimates of the risk of cardiac complications among patients with community-acquired pneumonia from a systematic review and meta-analysis.
Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality. CAP can trigger acute cardiac events. We sought to determine the incidence of major cardiac complications in CAP patients to characterize the magnitude of this problem.
Methods and Findings
Two investigators searched MEDLINE, Scopus, and EMBASE for observational studies of immunocompetent adults with clinical and radiological evidence of CAP that reported any of the following: overall cardiac complications, incident heart failure, acute coronary syndromes (ACS), or incident cardiac arrhythmias occurring within 30 days of CAP diagnosis. At a minimum, studies had to establish enrolment procedures and inclusion and exclusion criteria, enrol their patients sequentially, and report the incidence of cardiac complications as a function of their entire cohorts. Studies with focus on nosocomial or health care–associated pneumonia were not included. Review of 2,176 citations yielded 25 articles that met eligibility and minimum quality criteria. Seventeen articles (68%) reported cohorts of CAP inpatients. In this group, the pooled incidence rates for overall cardiac complications (six cohorts, 2,119 patients), incident heart failure (eights cohorts, 4,215 patients), acute coronary syndromes (six cohorts, 2,657 patients), and incident cardiac arrhythmias (six cohorts, 2,596 patients), were 17.7% (confidence interval [CI] 13.9–22.2), 14.1% (9.3–20.6), 5.3% (3.2–8.6), and 4.7% (2.4–8.9), respectively. One article reported cardiac complications in CAP outpatients, four in low-risk (not severely ill) inpatients, and three in high-risk inpatients. The incidences for all outcomes except overall cardiac complications were lower in the two former groups and higher in the latter. One additional study reported on CAP outpatients and low-risk inpatients without discriminating between these groups. Twelve studies (48%) asserted the evaluation of cardiac complications in their methods but only six (24%) provided a definition for them. Only three studies, all examining ACS, carried out risk factor analysis for these events. No study analyzed the association between cardiac complications and other medical complications or their impact on other CAP outcomes.
Major cardiac complications occur in a substantial proportion of patients with CAP. Physicians and patients need to appreciate the significance of this association for timely recognition and management of these events. Strategies aimed at preventing pneumonia (i.e., influenza and pneumococcal vaccination) in high-risk populations need to be optimized. Further research is needed to understand the mechanisms underlying this association, measure the impact of cardiac complications on other CAP outcomes, identify those patients with CAP at high risk of developing cardiac complications, and design strategies to prevent their occurrence in this population.
Please see later in the article for the Editors' Summary
Community-acquired pneumonia (CAP), that is, pneumonia infections contracted outside of hospital or health care settings, is a common condition and can be fatal, particularly to older people. For example, every year, an estimated 5–6 million people contract this form of pneumonia in the US, leading to 1.1 million people being admitted to hospitals and causing 60,000 deaths—the most frequent cause of infectious disease-related mortality. In the US for example, more than half of older patients who present to the hospital with CAP have preexisting chronic cardiac conditions—an important fact given that acute infections, such as CAP, can affect the cardiovascular system in various ways and precipitate acute cardiac events, such as heart failure, heart attacks, and cardiac arrhythmias.
Why Was This Study Done?
Although it is bio-medically plausible that a considerable proportion of patients with CAP have cardiac complications, systematic data on the scale of this potential problem are lacking—a concerning omission given the important implications for health policy-making and direct patient care. Therefore, in this study, the researchers conducted a systematic review to examine the published literature on cardiac complications in patients with CAP in order to characterize the nature and significance of this association, and to identify areas that require further research and investigation.
What Did the Researchers Do and Find?
The researchers searched MEDLINE, Scopus, and EMBASE for all relevant articles published in English, French, or Spanish languages until June 2010. The researchers used strict criteria to select appropriate articles (such as radiographic evidence of CAP) and only selected studies that had outcomes of the incidence of cardiac complications, such as incident (new or worsening) heart failure, acute coronary syndromes (acute myocardial infarction or unstable angina), and incident cardiac arrhythmias within 30 days of diagnosis of CAP.
Using these methods, the researchers identified 2,176 articles for review and selected 25 eligible papers for their analysis. Seventeen articles (68%) reported cohorts of CAP inpatients. In this group, the pooled incidence rates of overall cardiac complications (six cohorts, 2,119 patients), incident heart failure (eight cohorts, 4,215 patients), acute coronary syndromes (six cohorts, 2,657 patients), and incident cardiac arrhythmias (six cohorts, 2,596 patients), were 17.7%, 14.1%, 5.3%, and 4.7% respectively. Only three studies, (all of acute coronary syndromes) did risk factor analysis for these events. Possible risk factors identified included older age, preexisting congestive heart failure, severity of pneumonia, and the use of insulin by glucose sliding scales in hospitalized patients. No study analyzed the association between cardiac complications and other medical complications (such as acute renal failure, respiratory failure, shock, etc.) or their impact on other outcomes, such as death, in patients with CAP.
What Do These Findings Mean?
Although limited to a mostly descriptive analysis, these findings clearly show that major cardiac complications occur in a significant proportion of patients with CAP, especially in those admitted to hospital. These findings have important clinical and public health implications. Clinicians should be more aware of the significance of the association between CAP and cardiac complications to better inform, treat, and manage patients. Physicians and health officials need to increase efforts to optimize the rates of influenza and pneumococcal vaccination among older people and those with chronic cardiac conditions to reduce the incidence of CAP in these high-risk populations. There needs to be more consideration given to the potential impact of cardiac complications on mortality and costs associated with CAP. Finally, these findings highlight the need for prospective, well-designed, and adequately powered studies of cardiac complications in patients with CAP. More research attention should be given to this important area in order to improve the outcomes for patients with CAP and to decrease the consequent burden on health care systems through recognition of risk, prevention, and intervention on acute cardiac complications.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001048.
Information can be found on Wikipedia on community-acquired pneumonia (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The US Centers for Disease Control provide patient information on community-acquired pneumonia
The American Heart Association provides information on heart failure, acute coronary syndromes, and arrhythmias