We analyzed the impact of SBP on ACS patients’ improvement in the ED and evaluated its correlation with different subgroups of patients. The results showed that SBP=120-140 mmHg was an independent predictor for the decreased likelihood of improvement of ACS patients from the ED; SBP >140 mmHg, the use of ticagrelor, NSTEMI, and UA were significantly correlated with increased likelihood of ACS patients’ improvement in the ED. The AUC of the predictive efficacy of SBP, combined with ticagrelor, NSTEMI, and UA for the ACS patients’ improvement was 0.814 (95% CI: 0.795-0.833; P<0.001). To analyze the impact of SBP on improvement of different types of ACS population, we conducted a subgroup analysis. The results showed that the subgroups of males, females, DBP <80 mmHg, cTnI ≤0.1, treated with clopidogrel, treated with ticagrelor, treated with and without statins, UA, and SBP ˃140 mmHg were significantly associated with the improvement of ACS patients in the ED. In subgroup analysis, SBP=120-140 mmHg was an independent predictor of ED improvement in ACS patients who did not receive statins.
Most previous studies focused on analyzing the impact of SBP on the risk of death in ACS patients. A retrospective clinical study found that lower SBP was independently associated with the mortality risk of patients with non-ST-elevation ACS15. Patients with SBP <110 mmHg had a significantly increased risk of 7-day and 1-year mortality and major adverse cardiovascular events, while patients with high SBP >140 mmHg presented with a lower risk of mortality and MACE16. Compared with the lowest blood pressure classification, patients in the highest blood pressure category (SBP was categorized as ≤120 mmHg, 121–140 mmHg, 141–160 mmHg, and ≥160 mmHg. DBP was categorized as < 60 mmHg, 61–80 mmHg, 81–85 mmHg, and >86 mmHg) have a relative 70% lower mortality risk17. A prospective clinical study in Korea found that STEMI patients with normal SBP (≥100 mmHg and ≤139 mmHg) have a higher risk of in-hospital mortality compared with higher SBP (≥140 mmHg)18. Several clinical studies have evaluated the impact of blood pressure on clinical outcomes in patients with ACS other than death. A retrospective cohort study found that, compared with those with normal blood pressure, those with elevated blood pressure during ED visits were associated with an increased risk of hospitalization due to heart failure19. Lower blood pressure in ACS patients was significantly associated with an increased risk of hospitalization for cardiovascular events20. As far as we know, there is still a lack of research about the impact of SBP on ACS patients’ improvement in the ED. This study aims to fill the gap in literature about the impact of SBP on ACS patients’ improvement in the ED.
First, we analyzed the correlation between SBP and ACS patients’ improvement in the ED and found that SBP=120-140 mmHg was an independent predictor of decreased chance of improvement in ED. In contrast, SBP>140 mmHg was significantly associated with an increased chance of improvement of ACS patients. Patients with higher blood pressure upon admission to the ED were more likely to be improved. It is possible that for this result may include: for patients with impaired coronary perfusion, lowering blood pressure may reduce blood flow to target organs20. Hypotension may be associated with underlying chronic disease-related symptoms and increased morbidity and mortality. In addition, hypotension is a marker of cardiogenic shock and is associated with an increased risk of cardiovascular events20. Patients with higher blood pressure may be more likely to be attended sooner by clinicians. Clinicians may then take some interventions to lower blood pressure, making it easier for these patients to be improved in the ED.
The Study of Platelet Inhibition and Patient Outcomes (PLATO) found that ticagrelor treatment for 12 months can significantly reduce the risk of myocardial infarction, stroke, and cardiovascular death in ACS patients21. Moreover, ticagrelor can effectively prevent new ischemic events and mortality in ACS patients, regardless of the presence of heart failure22. This is consistent with our research results. Our study also found that NSTEMI is an independent predictor of ACS patients’ improvement in the ED. To the best of our knowledge, the clinical characteristics of STEMI patients are different from those of NSTEMI. Compared with STEMI, NSTEMI has better short-term outcomes23-25. Compared with STEMI and NSTEMI patients, UA patients have lower short-term mortality risk26,27. Therefore, NSTEMI and UA patients may have better treatment outcomes and were therefore more likely to be improved in the ED and transferred to general ward. This was consistent with the results of this study, which showed that NSTEMI was an independent predictor of ACS patients’ improvement in the ED.
The study also found that the AUC of SBP, combined with several other related variables for ACS patients’ improvement in the ED was 0.814, the sensitivity was 0.801, and the specificity was 0.738. SBP, combined with other variables for the diagnosis of ACS patients, risk stratification and prediction of mortality risk has been confirmed by several studies11,28-30. However, it is the first time that SBP was analyzed in combination with other related variables that predict ACS patients’ improvement in the ED.
Subgroup analysis found that the subgroups of males, females, DBP <80 mmHg, cTnI ≤0.1, use of clopidogrel, use of ticagrelor, use/non-use of statins, UA, and SBP ˃140 mmHg were significantly associated with the improvement of ACS patients in the ED. In the subgroup that was not treated with statins, SBP=120-140 mmHg was also an independent predictor of an increased chance of improvement in the ED. The results of these subgroup analyses suggest that for ACS patients with different risks, SBP has different effects on patients’ improvement in the ED.
The study had several limitations. First, this was a retrospective study; hence, the results need to be verified by a prospective clinical trial. Second, our study was a single-center study; therefore, the research results need to be further verified by multi-center clinical studies. Third, there was also a lack of clinical biochemical variables in the study, which could be further addressed in future research.
In conclusion, SBP=120-140 mmHg was an independent predictor for the decreased likelihood of improvement of ACS patients from the ED; SBP >140 mmHg, the use of ticagrelor and NSTEMI were significantly correlated with increased likelihood of ACS patients’ improvement in the ED and transfer to general ward. SBP >140 mmHg was an independent predictor of improvement in most subgroups.