Predicting Pulmonary Infection in Acute Myocardial Infarction: Total Care of Cardiovascular and Non-Cardiovascular Outcomes

See article vol. 31: 1680-1691

Acute myocardial infarction (AMI) is a fatal disease with adverse outcomes both during hospitalization and in the remote phase, despite widespread primary percutaneous coronary intervention (PCI), mechanical support devices, medical therapy, and cardiac rehabilitation¹⁾. This indicates unmet clinical needs and residual risks in the contemporary clinical practice of post-AMI care. For this reason, cardiologists are often preoccupied with the management based mainly on the cardiovascular indices and risk factors in the acute care of AMI. However, to achieve comprehensive care in patients who experienced AMI, we also need to pay attention to their non-cardiovascular clinical aspects. In this context, a previous study revealed that the incidence of in-hospital pulmonary infection in survivors immediately after AMI substantially worsened the clinical outcomes in the remote phase²⁾, highlighting the importance of early and appropriate risk stratification. However, a reliable predictive tool for the risk of in-hospital pulmonary infection in AMI survivors is not yet well established, potentially resulting in oversight of this risk in the actual setting of AMI care.

In the current Journal of Atherosclerosis and Thrombosis issue, Kong et al. investigated the predictive impact of serum albumin-to-creatinine ratio (sACR) on pulmonary infection due to AMI during hospitalization³⁾. sACR is a relatively novel parameter that combines serum albumin with creatinine. Serum albumin (SA) is an essential indicator of nutritional status and inflammation. A recent study demonstrated that SA was an independent predictor for in-hospital pulmonary infection⁴⁾. However, the predictability of patient outcomes in the acute phase may be limited due to the factorability of the SA level influenced by the hemodynamic status, acute inflammation, and renal function⁵⁾. In contrast, serum creatinine (sCr) is a well-established renal indicator and has been reported to be helpful as a prognostic marker in cardiovascular disease and infection. The combined use of SA and sCr levels was expected to complement SA’s potential limitations. Therefore, sACR is recognized as having a higher prognostic value than SA and sCr individually in patients with AMI⁶⁾. However, studies on the association between sACR levels and pulmonary infection incidence in patients with AMI are limited.

Kong et al. investigated the relationship between sACR and in-hospital pulmonary infection in 4,507 patients with ST-segment elevation AMI undergoing PCI³⁾. The cohort was divided into three groups according to sACR tertile. The primary outcome was in-hospital pulmonary infection while the secondary outcomes were in-hospital major adverse cardiovascular events (MACE) (composite outcome including stroke, in-hospital mortality, target vessel revascularization, and recurrent myocardial infarction) and all-cause mortality during the follow-up. They found that higher tertiles of sACR were associated with lower rates of pulmonary infection (22.8%, 7.3%, and 4.7% for tertiles 1–3, respectively; P＜0.001) and in-hospital MACE (10.1%, 2.7%, and 2.1% for tertiles 1–3, respectively; P＜0.001). In this study, sACR was an independent predictor of in-hospital pulmonary infection and MACE, with the area under the curve using the receiver operating characteristic curve being 0.73 (95% CI=0.70–0.75, P＜0.001) and 0.72 (95% CI=0.69–0.76, P＜0.001), respectively. sACR was also associated with long-term mortality (hazard ratio HR=0.96, 95% CI=0.95-0.98, P＜0.001), indicating that sACR may predict both short and long-term outcomes.

Notably, this study was based on an observational analysis without other infection data, which is cited as a limitation by the authors of this study. However, their study presents the clinical significance of sACR. In general, in-hospital pulmonary infection causes prolonged hospitalization, reduced activities of daily living, and cognitive decline⁷⁾. sACR has shown the potential to stratify cases at high risk of pulmonary disease in patients with AMI. Careful follow-up might be necessary in patients at high risk of pulmonary infection identified based on sACR. Furthermore, introducing pneumonia prevention measures (e.g. oral care, rehabilitation) based on sACR may improve prognosis⁸⁾.

The patient cohorts in this study with low sACR include individuals in poor general condition, such as those having advanced age, higher New York Heart Association class, and higher mechanical support usage. Thus, careful consideration of pulmonary infection during hospitalization, particularly in such a patient population, is necessary. Prospective studies with sACR are desired to clarify the significance of the preventive method. Such studies would uncover whether sACR is a cause or a consequence of pulmonary infections as a pathophysiological association of sACR. In addition to the usefulness of risk assessment during hospitalization, this study demonstrates the effectiveness of sACR on all-cause mortality after discharge.

Similarly, sACR might help predict non-cardiovascular events (e.g., pneumonia and other infections) in the chronic phase. Previous papers have shown that reassessment of albumin and other parameters can help improve the prognostic value of long-term events in predicting long-term events⁹⁾. To achieve comprehensive care in patients, further studies on sACR reassessment and long-term events are warranted.

Conflict of Interest

The authors declare no conflicts of interest.

Funding

The Takeda Science Foundation partly supported this work.

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