The Burden of Cardiac Complications in Patients with Community-Acquired Pneumonia

Strategies to Prevent Cardiac Complications During CAP

It is now well established that there is a heavy burden of long-lasting cardiac complications among patients with CAP; therefore, preventing CAP should be a priority. This can be accomplished by counseling patients to refrain from alcohol and smoking and by administering influenza (Table 2) and pneumococcal vaccines (Figure 2). Since the 7-valent protein-polysaccharide conjugate pneumococcal vaccine (PCV-7) was released for children in 2000, there have been fewer hospitalizations in the United States [27] and improved outcomes globally; for instance, fewer hospitalizations among children < 14 years of age in Uruguay [29], and decreased invasive pneumococcal disease among children < 5 years of age in Taiwan [30]. Furthermore, a decrease in invasive pneumococcal disease by 18% in persons aged > 65 years in the US and Canada decreased with the introduction of PCV-7 to children. Although this showed a beneficial indirect effect (herd immunity) in unvaccinated populations [31,32], there have been no randomized controlled trials in adults demonstrating a decrease in pneumococcal pneumonia or invasive pneumococcal disease which were vaccinated with PCV-13. The Food and Drug Administration approved PCV-13 for children in 2010 and for adults in 2012. Although it included fewer serotypes, it did include serotype 6A, which has a high pathogenicity and is not in 23-valent pneumococcal polysaccharide vaccine (PPSV-23). The criteria for vaccinating adults for pneumococcal infection were recently published [33]. A study of patients with invasive pneumococcal disease, which also determined pneumococcal serotypes, included 5 patients who had CAP as well [34]. Those patients had serotypes 6A, 7C, 14, and 23F (2 patients). The patient who had serotype 14 (higher pathogenicity) died and the other 4 lived. Serotypes 14 and 23F are in both vaccines while serotype 7C is in neither. Vaccination status was not provided in the study. At this time, there is evidence to support vaccinating patients for both S. pneumoniae and influenza virus.

Two methods used to prevent cardiac complications in general have been administration of aspirin and statins. The anticlotting properties of aspirin help to maintain blood flow in arteries narrowed by atherosclerosis. A meta-analysis of 10 randomized controlled trials found a statistically significant association between aspirin and a benefit on nonfatal myocardial infarctions/coronary events [35]. The associations were found with doses of 100 mg or less daily, and benefits were seen within 1 to 5 years. Statins have also been found to reduce all-cause mortality, cardiac-related mortality, and myocardial infarction [36]. A statin may stabilize coronary artery plaques that otherwise may rupture and cause myocardial ischemia or an infarct. But statins have also been found to be associated with a decreased risk of CAP. A comprehensive systematic review and meta-analysis found a decreased risk of CAP (OR 0.84; 95% CI, 0.74– 0.95) and decreased short-term mortality in patients with CAP (OR 0.68; 95% CI, 0.56–0.78) as a result of statin therapy [37]. The studies included any of 8 available statins. A prospective observational study found that patients who had been on a statin prior to being admitted for CAP had lower mortality, a lower incidence of complicated pneumonia and a lower C-reactive protein [38]. The lower C-reactive protein identifies decreased inflammation, which translates into improved endothelial function, modulated antioxidant effects, and a reduction in pro-inflammatory cytokines, hence its association with less severe CAP. Further study may reveal that a certain patient population should receive a statin to prevent CAP and improve outcomes. Overall, data support taking aspirin to prevent cardiac events regardless of CAP; further investigation of the benefits of statins to prevent cardiac complications in CAP patients is needed.

Clinical Applications

There are several implications of knowing the relationship between cardiac complications and CAP. First, physicians can better inform their patients about risks once they have been diagnosed with pneumonia. Second, physicians may be more likely to recognize a complication early and provide appropriate intervention. Third, physicians can risk stratify patients using the prediction score for cardiac complications in CAP patients [28]. In 1931 Master et al found that some patients with CAP also had PR interval or T-wave changes present for about 3 days, so they recommended obtaining an ECG to determine when a patient might be able to be discharged or declared “cured” [39]. Now, we are similarly recommending obtaining an ECG in CAP patients, but upon admission, in order to identify those who may get ischemic changes, arrhythmias or QTc prolongations. Pro-brain natriuretic peptide and troponins may be obtained independently of ECG results, and a cardiac echocardiogram may be reserved for those with a high risk of complications [40]. Finally, we recommend screening all patients for need for influenza and pneumococcal vaccines and administering according to the Advisory Committee on Immunization Practices of the Centers for Disease and Prevention [33].

Research Implications

The fact that cardiac complications in CAP patients is a well-defined entity with a significant degree of morbidity and mortality should prompt attentiona and resources to be directed to this area. The prediction score created specifically for this subpopulation of patients [28] can improve research by allowing adequate risk stratification to efficiently design and execute studies. Studies may be designed with fewer patients required to be enrolled while maintaining statistical power by limiting subject inclusion criteria to certain risk classes. Specific areas of future investigation should include the mechanisms of pathophysiology, which are not completely understood, and other complications, such as pulmonary edema, infectious endocarditis and pericarditis. Finally, cost has not been studied in this area or the potential savings of recognizing and preventing cardiac complications.

Summary

Cardiac complications, including arrhythmias, MI, and CHF are a significant burden among patients hospitalized for CAP. Influenza and pneumococcal vaccination should be emphasized among appropriate patients. The cardiac complication prediction score may be used to screen patients once admitted. A troponin and ECG should be obtained in all patients admitted for CAP while a cardiac echocardiogram may be reserved in higher-risk patients. Future research may be directed towards the subjects of pathophysiology other complications and cost.

Acknowledgment: We appreciate the critical review by Jessica Lynn Petrey, MSLS, Clinical Librarian, Kornhauser Health Sciences Library, University of Louisville, Louisville, KY.

Corresponding author: Dr. Forest Arnold, 501 E. Broadway, Suite 140 B, Louisville, KY 40202, f.arnold@louisville.edu

Financial disclosures: None.