This population-based study retrospectively investigated 13658 patients admitted to the ICU with GERD. A nomogram model was developed and validated to gauge the risk of CA. The nomogram contained 9 variables: age, WBC, hemoglobin, MCH, MCV, sodium, bicarbonate, creatinine and chloride. It demonstrated good clinical utility. The ROC analysis of the training cohort had an AUC of 0.7500 and that of the test cohort was 0.7297, suggesting that our model is predictive.
There are large prospective cohort studies showing that all gastrointestinal diseases increase the incidence of cardiovascular disease to a greater or lesser extent, with the relevance of GERD and CA being of particular interest [23, 24]. It has therefore been suggested that GERD may be an independent risk factor for cardiovascular disease [25]. Pathophysiological mechanisms that have been widely investigated for the link between GERD and CA include inflammation, autonomic function and fibrinolysis [26–28].
Age is a known risk factor for CA [29]. Older people are significantly more likely to develop or progress with CA than younger people [29, 30]. Age is also a risk factor for GERD [31, 32]. The likelihood of GERD patients developing CA gradually increases with age, a result consistent with our model. Previous studies have shown that inflammation is a key feature of atherosclerosis and its clinical manifestations, and white blood cell count is an indicator of inflammation [26]. It is common sense that the higher the white blood cell count, the greater the severity of CA [33–36]. But this is not the case with our nomogram results. The risk score is high when the white blood cell count is within a certain range. Follow-up studies on the relationship between different segments of the white blood cell count and the risk of CA are worthwhile. Our model shows that as hemoglobin rises, the likelihood of CA in GERD patients increases. However, previous studies have focused more on glycated hemoglobin and cardiovascular disease and have not looked at the relationship between hemoglobin and CA [37]. The reasons for this phenomenon need to be investigated further. Only a few studies have examined cardiovascular disease in relation to general haematological indices. The conclusions of the few remaining studies are often contradictory. Some studies conclude that higher MCH and MCV are associated with a higher risk of cardiovascular disease [38]. Others have concluded that lower MCV is associated with a higher risk of cardiovascular disease, whereas MCH is not associated with cardiovascular disease [39]. Our study concluded that higher MCH and lower MCV were positively associated with a higher incidence of CA. Elevated blood pressure due to high salt diet and high serum sodium level is a risk factor for coronary artery disease [40]. A number of studies based on this have also concluded that a higher serum sodium level is associated with a higher cardiovascular risk [41]. Other studies have demonstrated a negative correlation between blood sodium levels and the incidence of cardiovascular events [42, 43]. From our nomogram, we can see that our results support the conclusion of a negative correlation. However, the exact reason for the negative correlation remains to be explored. There are also conflicting conclusions about the relationship between bicarbonate and cardiovascular risk. There are studies suggesting that higher bicarbonate or lower bicarbonate is associated with higher cardiovascular risk [44, 45]. However, none of these trials had a large enough sample size to be convincing. Our study concluded that the odds of CA in patients with GERD increased with higher bicarbonate levels. In our study, the association between creatinine and CA was not as strong as other factors. A slight increase in creatinine may cause an increase in the incidence of CA. This result is in line with the results of the existing papers [46]. Researches on the relationship between blood chloride and cardiovascular risk are particularly scarce. The existing studies contradict our finding of higher cardiovascular risk accompanied with higher blood chloride [47]. This may be a new direction for research.
Clinicians need to evaluate patients with GERD before deciding on treatment plans. The identification of predictive factors and risk assessment is crucial to prevent the occurrence of CA. A nomogram is a total score based on the values of multiple predictor variables for an individual. Our nomogram includes nine variables that are readily available in regular clinical practice and can be assessed easily. Patients with GERD can also evaluate their situation using our nomogram.
Our study has some limitations. Firstly, all of our data came from the MIMIC-IV database. Incomplete records and possible data errors may have reduced the accuracy of our model. Secondly, this was a single-center retrospective study; only internal validation was performed, so external validation is needed to confirm the reliability of the results. Thirdly, blood lipids were not included in the study due to the lack of corresponding records in the MIMIC-IV database. Blood lipids are important risk factors for cardiovascular diseases [48], so further research on them is necessary. Fourthly, the types and severity of GERD were not considered in this study, which did not determine the risk of developing CA for each severity level of GERD. In addition, all types of CA were lumped together. Finally, our nomogram may predict the possibility of CA in patients with GERD, but cannot answer whether intervention was prompt.