Patterns of inflammatory activation associated with precipitants of acute coronary syndromes: a case-crossover study

Triggering of cardiovascular disease by infection type: The Atherosclerosis Risk in Communities study (ARIC)

INTRODUCTION

Acute infections are known triggers of cardiovascular disease (CVD) but how this association varies across infection types is unknown. We hypothesized while acute infections increase CVD risk, the strength of this association varies across infection types.

METHOD

Acute coronary heart disease (CHD) and ischemic stroke cases were identified in the Atherosclerosis Risk in Communities Study (ARIC). ICD-9 codes from Medicare claims were used to identify cellulitis, pneumonia, urinary tract infections (UTI), and bloodstream infections. A case-crossover design and conditional logistic regression were used to compare infection types among acute CHD and stroke cases 14, 30, 42, and 90 days before the event with two corresponding control periods (1 and 2 years prior).

RESULTS

Of the 1312 acute CHD cases, 116 had a UTI, 102 had pneumonia, 43 had cellulitis, and 28 had a bloodstream infection 90 days before the CHD event. Pneumonia (OR = 25.53 (9.21,70.78)), UTI (OR = 3.32 (1.93, 5.71)), bloodstream infections (OR = 5.93 (2.07, 17.00)), and cellulitis (OR = 2.58 (1.09, 6.13)) were associated with higher acute CHD risk within 14 days of infection. Of the 727 ischemic stroke cases, 12 had cellulitis, 27 had pneumonia, 56 had a UTI, and 5 had a bloodstream infection within 90 days of the stroke. Pneumonia (OR = 5.59 (1.77, 17.67)) and UTI (OR = 3.16 (1.68, 5.94)) were associated with higher stroke risk within 14 days of infection.

CONCLUSIONS

Patients with pneumonia, UTI, or bloodstream infection appear to be at a 2.5 to 25.5 fold elevated CVD risk following infection. Preventive therapies during this high-risk period should be considered.

Inpatient and Outpatient Infection as a Trigger of Cardiovascular Disease: The ARIC Study

Background

Acute infections are known cardiovascular disease (CVD) triggers, but little is known regarding how CVD risk varies following inpatient versus outpatient infections. We hypothesized that in‐ and outpatient infections are associated with CVD risk and that the association is stronger for inpatient infections.

Methods and Results

Coronary heart disease (CHD) and ischemic stroke cases were identified and adjudicated in the ARIC (Atherosclerosis Risk in Communities Study). Hospital discharge diagnosis codes and Medicare claims data were used to identify infections diagnosed in in‐ and outpatient settings. A case‐crossover design and conditional logistic regression were used to compare in‐ and outpatient infections among CHD and ischemic stroke cases (14, 30, 42, and 90 days before the event) with corresponding control periods 1 and 2 years previously. A total of 1312 incident CHD cases and 727 incident stroke cases were analyzed. Inpatient infections (14‐day odds ratio [OR]=12.83 [5.74, 28.68], 30‐day OR=8.39 [4.92, 14.31], 42‐day OR=6.24 [4.02, 9.67], and 90‐day OR=4.48 [3.18, 6.33]) and outpatient infections (14‐day OR=3.29 [2.50, 4.32], 30‐day OR=2.69 [2.14, 3.37], 42‐day OR=2.45 [1.97, 3.05], and 90‐day OR=1.99 [1.64, 2.42]) were more common in all CHD case periods compared with control periods and inpatient infection was a stronger CHD trigger for all time periods (P<0.05). Inpatient infection was also a stronger stroke trigger with the difference borderline statistically significant (P<0.10) for the 42‐ and 90‐day time periods.

Conclusions

In‐ and outpatient infections are associated with CVD risk. Patients with an inpatient infection may be at particularly elevated CVD risk and should be considered potential candidates for CVD prophylaxis.

See Editorial by https://doi.org/10.1161/JAHA.118.011175

Acute and Subacute Triggers of Cardiovascular Events

Inability to predict short-term cardiovascular (CV) events and take immediate preemptive actions has long been the Achilles heel of cardiology. However, certain triggers of these events have come to light. Although these triggers are nonspecific and are part of normal life, studying their temporal relationship with the onset of CV events provides an opportunity to alert high-risk atherosclerotic patients who may be most vulnerable to such triggers, the "vulnerable patient". Herein, we review the literature and shed light on the epidemiology and underlying pathophysiology of different triggers. We describe that certain adrenergic triggers can precipitate a CV event within minutes or hours; whereas triggers that elicit an immune or inflammatory response such as infections may tip an asymptomatic "vulnerable patient" to become symptomatic days and weeks later. In conclusion, healthcare providers should counsel high-risk CV patients (e.g., in secondary prevention clinics or those with coronary artery Calcium >75th percentile) on the topic, advise them to avoid such triggers, take protective measures once exposed, and seek emergency care immediately after becoming symptomatic after such triggers. Furthermore, clinical trials targeting triggers (prevention or intervention) are needed.

Triggering of acute myocardial infarction by respiratory infection

BACKGROUND

Respiratory infection has been associated with an increased short-term risk of myocardial infarction (MI). However, previous studies have predominantly been conducted without angiographic confirmation of MI. The possibility can therefore not be excluded that raised troponin levels or electrocardiogram abnormalities that may be seen with respiratory infections are due to non-ischaemic causes.

AIMS

To investigate the association between respiratory infection and angiographically confirmed MI.

METHODS

Interviews were conducted within 4 days of hospitalisation in 578 patients with angiographically confirmed MI, to assess for recent exposure to respiratory infection symptoms and the usual annual frequency of these symptoms. Using case-crossover methodology, exposure to respiratory infection prior to the onset of MI was compared against the usual frequency of exposure in the past year.

RESULTS

Symptoms of respiratory infection were reported by 100 (17%) and 123 (21%) within 7 and 35 days, respectively, prior to MI. The relative risk (RR) for MI occurring within 1-7 days after respiratory infection symptoms was 17.0 (95% confidence interval (CI) 13.2-21.8), and declined with subsequent time periods. In a subgroup analysis, the RR tended to be lower in groups taking regular cardiac medications. For those who reported milder, upper respiratory tract infection symptoms, the RR for the 1-7-day time period was 13.5 (95% CI 10.2-17.7).

CONCLUSION

These findings confirm that respiratory infection can trigger MI. Further study is indicated to identify treatment strategies to decrease this risk, particularly in individuals who may have increased susceptibility.

C-reactive protein and lung diseases

C-reactive protein (CRP), a member of the pentraxin family of plasma proteins, is one of the most distinctive acute phase reactants. In response to inflammation, cell damage or tissue injury, plasma level of CRP rapidly and dramatically increases up to 1000-fold, a phenomenon that has been used for years to monitor infections and many destructive/inflammatory conditions. The magnitude of CRP increase usually correlates with the severity of injury or inflammation and reflects an important physiological role of this interesting but still under-investigated protein. It is now generally accepted that CRP is involved in host defense and inflammation. However, the exact function of this protein in health and disease remains unclear. Many studies have demonstrated that in different pathophysiological conditions CRP might be involved in the regulation of lung function and may participate in the pathogenesis of various pulmonary disorders. The fluctuation of CRP concentrations in both alveolar fluid and serum associated with different pulmonary diseases suggests its important role in lung biology. Discussion of the still controversial functions of CRP in lung physiology and diseases is the main focus of this review.