Factors associated with acute myocardial infarction in older patients after hospitalization with community-acquired pneumonia: a cross-sectional study

The growing proportion of older adults provides a compelling reason for an increased focus on public health problems of older people. Community-acquired pneumonia (CAP) and acute myocardial infarction cardiovascular (AMI) are two major public health issues in older patients. It is estimated that incidence of CAP patients≥65 years old was 140 cases per 10,000 persons per year and 105 cases per 10,000 for hospitalized [1]. The mortality rate for CAP has been decreasing after the introduction of antibiotics, even so, high mortality still in the older patients. Mortality in geriatric patients with CAP may be 25% higher than in the general population [2, 3]. The incidence and mortality risk in CAP are linked to increasing age and the presence of age-related comorbidities and complications. Thus, there is a clear need to recognize the life-threatening complications among geriatric patients with CAP.

A link between acute infections and the development of cardiovascular complications has been proposed [4‐9]. Pneumonia contributes to the acute worsening of pre-existing cardiac conditions and can trigger new cardiac events. Moreover, a higher likelihood of a poorer outcome in a patient with CAP complicated by an acute cardiovascular event [10]. Cardiovascular complications represent a heavy burden on the course and outcomes of patients admitted to hospital with CAP. Recent clinical observations suggest that acute cardiovascular complications are more frequent in high-risk CAP patients. The older adults are at high risk of CAP. An increase in pneumonia hospital admissions and potentially deaths mainly due to the ageing population [11], a population that is also at the highest risk for cardiovascular diseases. Cardiovascular complications after pneumonia including new or worsening heart failure, new or worsening arrhythmias and AMI. Hitherto, reports of cardiovascular complications after CAP were mostly focus on heart failure, few about AMI, which is a life-threatening complication. In particularly, systematically studied of geriatric patients are unavailable to date.

Despite AMI after CAP in geriatric patients is a worthy concern, little is known regarding the clinical characteristics of the older adults. Therefore, our study aimed to determine the prevalence, characteristics compared with younger patients, impact on clinical outcomes and risk factors of AMI during hospitalization for CAP in geriatric patients.

In this study, we found that 159 (3.1%) older patients experienced AMI during hospitalization for CAP. The incidence of AMI during CAP hospitalization in older patients was 3.1% in our study. Hitherto, systematically studied of AMI during CAP hospitalization in geriatric population are unavailable to date. The incidence of acute coronary syndromes (ACS) in previous studies of adult CAP inpatients has varied widely, the frequency in the range between 0.7 and 11% [8, 9, 14‐16]. One meta-analysis suggested the pooled ACS event rates after CAP was 4.5% [17]. A few studies reported only on myocardial infarction. A 3.1% incidence of myocardial infarction was mentioned in a study of cardiac complications in CAP inpatients reported by Vicente et al. [18] Perry et al. [5] reported a 1.5% 90-day incidence of myocardial infarction following hospital admission for pneumonia, which has the largest number of cases in previous studies about cardiovascular events after pneumonia with 50,119 patients. Compared with earlier published data, we demonstrate that AMI occurred during hospitalization in a limited but significant proportion of older adults hospitalized due to CAP.

This study is the first to investigate the characteristics of older patients who experiencing AMI during CAP hospitalization. We faces the day-to-day challenges of aging. Hence, in a further analysis, patients≥65 years were compared with those patients< 65 years experiencing AMI during CAP hospitalization in our study. AMI is more prevalent in geriatric patients with CAP than in the general population, the incidence of AMI during hospitalization in older patients (3.1%) was nearly almost triple versus non-older patients (1.0%) in our study. We noted that higher proportion patients suffer from respiratory failure in older patients. Symptoms in the older patients were more of a dyspnea, unlike chest pain in the younger patients. Usually, chest pain is considered as a typical symptom of AMI, however, symptoms in the older patients were not always typical. Since the clinical presentation of AMI in the older patients may be atypical, clinicians should suspect AMI in older patients presenting symptoms such as dyspnea. The older patients experiencing AMI had more history of hypertension, and younger patients had more diabetes and hyperlipidemia. In laboratory findings, BUN≥7 mmol/L and serum sodium < 130 mmol/L were more frequently present in the older patients. Identify the characteristics of the older patients is beneficial to clinical diagnosis, evaluation and individual-based treatment.

Another important aspect of our study was the identification of risk factors associated with the occurrence of AMI during CAP hospitalization in geriatric patients. Risk factors of ACS after CAP were reported only in three previous studies, possible risk factors included older age, congestive heart failure or previous myocardial infarction, female sex, severe sepsis, chronic obstructive pulmonary disease, chronic kidney or liver disease [9, 19, 20]. Through logistic regression analysis in our study, we demonstrated that preexisting coronary artery disease, diabetes, respiratory failure and BUN were significantly correlated with the occurrence of AMI. It is interesting to note that the both traditional and non-traditional cardiovascular risk factors were probably associated with the occurrence of AMI. An increased serum BUN levels suggested acute kidney injury, which is common during pneumonia. Renal insufficiency and diabetes are acknowledged risk factors for myocardial infarction [21, 22]. BUN is one indicator of the severity of pneumonia. More important however, is our finding that respiratory failure was an important factor associated with the occurrence of AMI. Respiratory failure indicates more severe disease status, hypoxia, and more severe inflammation, that suggests a role for the body’s inflammatory and hypoxia in the mechanisms accounting for cardiovascular complications in patients with CAP.

According to new clinical classification of myocardial infarction [23], most AMI during CAP hospitalization in geriatric patients may be classified as type 2. This type AMI secondary to ischaemia due to either increased oxygen demand or decreased supply. The actual mechanisms by which pneumonia triggers myocardial ischaemia have not yet been fully evaluated. Acute pneumonia can induce inflammatory changes in atherosclerotic plaques, demand ischemia, endothelial dysfunction, and procoagulant changes in blood [4, 6]. Accumulating evidence on the mechanisms of ACS after acute infections suggests that inflammatory activity is thought to play a key role in the pathogenesis of coronary events. Acute infections induce substantial inflammatory reactions, they can potentially contribute to the development of ACS [24‐26]. Pneumonia contributes to the acute worsening of pre-existing cardiac conditions and can trigger new cardiac events. In pneumonia, a generalized inflammatory response is usually fully activated by the time patients present to hospital [27]. Previous studies suggests that systemic inflammatory response may cause inflammation in coronary arteries and their pre-existing atherosclerotic lesions [28]. Infections can induce pro inflammatory changes in the cellular composition of the atherosclerotic lesions and make them more vulnerable to cause coronary [28, 29]. Acute infections can also cause acute dysfunction and/or physical disruption of the endothelium [30, 31].

The study has some limitations. The first is the retrospective design of the study which resulted in some variables cannot be extracted from the electronic medical records. Data of peripheral arteriosclerosis evaluation were incomplete in respiratory ward and some patients in respiratory wards did not have BNP results at the time of admission, these were not available for our analyses. Since the D-Dimer detection was done in the respiratory ward by a analyzer used only in the respiratory department, the data was not recorded in the electronic medical records management system of our hospital. Meanwhile, partly of patients didn’t have a CURB-65 or PSI score, which are most commonly scales for assessment the severity of CAP, nevertheless, the variables in both scales were included in the study. Secondly, in our real-world study, treatment regimens were relatively individual, and few patients underwent coronary angiography which is why it was not easy to analyze the relationship between specific treatment regimens and clinical outcomes. Future research will be required to determine if specific measures such as Aspirin or drugs lowering systemic inflammation could prevented cardiovascular complications in CAP inpatients. Thirdly, this study was conducted in a single hospital serving an urban area. It would be interesting to extend these observations in a larger sample and multicenter.

The incidence of AMI during CAP hospitalization in geriatric patients is notable and have an impact on in-hospital mortality. Particular attention should be paid to older patients with respiratory failure, preexisting coronary artery disease, diabetes, with high BUN level and impaired consciousness. Our study may represent useful information for planning of clinical strategies aimed at preventing AMI and decreasing mortality rate in geriatric patients hospitalization for CAP.