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Mortality across the spectrum of hemoglobin level in patients undergoing surgical coronary revascularization
Amirmohammad Khalaji1,2,3,4, Ali Ajam1,2, Ali Sheikhy1,2,3,4
1Tehran Heart Center, Cardiovascular Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
Insights
Preoperative hemoglobin levels, both high and low, are linked to increased in-hospital mortality in nonanemic patients undergoing coronary artery bypass grafting (CABG). These risks differ between men and women.
Area of Science:
- Cardiology
- Hematology
Background:
- Preoperative hemoglobin (Hb) level is a known predictor of mortality after coronary artery bypass grafting (CABG).
- Existing research has not fully clarified the specific risks associated with varying Hb levels and potential sex-based differences in outcomes.
Purpose of the Study:
- To investigate the sex-specific association between preoperative hemoglobin levels and mortality outcomes in nonanemic patients undergoing CABG.
- To determine if the relationship between Hb levels and mortality is linear or non-linear.
Main Methods:
- A registry-based, serial cross-sectional study included 13,557 nonanemic patients who underwent CABG.
- Restricted Cubic Splines in Cox models were used to analyze sex-specific correlations between Hb levels and in-hospital, 6-month, and 1-year mortality.
- Outcomes were adjusted for potential confounders.
Main Results:
- A U-shaped correlation was observed between Hb level and in-hospital mortality.
- Significantly lower Hb levels were found in deceased patients, who also had higher rates of diabetes, hypertension, and lower ejection fraction.
- Optimal Hb cut-offs for reduced mortality risk differed between males (≥15.62 and ≤13.25 g/dL) and females (≥14.92 and ≤13.4 g/dL).
Conclusions:
- The association between preoperative Hb level and in-hospital mortality is non-linear and sex-dependent in nonanemic CABG patients.
- Both low and high preoperative Hb levels are associated with increased mortality risk.
Background:
Preoperative hemoglobin (Hb) level is a predictor of in-hospital and midterm mortality in patients undergoing coronary artery bypass grafting surgery (CABG). However, the debate about the different hazards across Hb levels and sex differences in outcome occurrence is still on the table.
Methods:
This is a registry-based serial cross-sectional study at Tehran Heart Center. Nonanemic patients who underwent CABG with complete follow-up data were included. The Restricted Cubic Splines (RCS) in the Cox model was used to calculate the sex-specific correlation between in-hospital, 6-month, and 1-year mortalities and normal Hb levels using odds ratio for the in-hospital and hazard ratios for 6-month and 1-year mortality, adjusted for all possible confounders.
Results:
From 2005 to 2016, a total of 13,557 patients were included, of which 134 had in-hospital mortality as our primary outcome. Preoperative Hb levels were significantly lower in the deceased. Moreover, dead patients had significantly higher rates of diabetes and hypertension, while lower ejection fraction. Cut-offs for reference Hb level were higher for males compared with females. The correlation between Hb level and in-hospital mortality was nearly U-shaped. Quantitatively, Hb of ≥15.62 and ≤13.25 g/dL for men and that of ≥14.92 and ≤13.4 g/dL for women tended to be associated with higher in-hospital mortality.
Conclusions:
The association between preoperative Hb level and in-hospital mortality differs in men and women and does not follow a linear correlation among nonanemic patients. Both low and high numbers in the Hb level spectrum are at greater risk.
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