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Low serum magnesium level predicts major adverse cardiac events after coronary artery bypass graft surgery
John V Booth1, Barbara Phillips-Bute, Charles B McCants
1Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA. Booth006@mc.duke.edu
Insights
Low serum magnesium levels after coronary artery bypass graft surgery (CABG) significantly increase the risk of major adverse cardiac events, including death and myocardial infarction. Monitoring and potentially supplementing magnesium may improve patient outcomes post-CABG.
Area of Science:
- Cardiology
- Cardiovascular Surgery
- Clinical Biochemistry
Background:
- Coronary artery bypass graft surgery (CABG) mortality remains high despite surgical advancements, potentially due to an aging patient population.
- Magnesium plays a crucial role in vascular tone, reperfusion injury, and thrombosis.
- The study investigated the link between serum magnesium levels and adverse cardiac events following CABG.
Purpose of the Study:
- To determine the association between postoperative serum magnesium levels and major adverse cardiac events (MACE) in patients undergoing primary CABG.
- To assess the impact of low magnesium levels on event-free survival after CABG.
- To identify potential therapeutic targets for improving outcomes in CABG patients.
Main Methods:
- Prospective recruitment of 957 patients undergoing primary CABG into the Duke Cardiovascular database.
- Daily measurement of serum magnesium levels for the first 8 days post-surgery.
- Definition of low magnesium as <1.8 mmol/L, and adverse events as Q-wave infarction or death at 1 year.
- Utilized Kaplan-Meier survival analysis and Cox proportional hazards models.
Main Results:
- Patients with low serum magnesium (<1.8 mmol/L) experienced adverse events at a rate of 12.3%, versus 9.2% in the normal magnesium group.
- Low magnesium levels were associated with a 2-fold increased risk of death or myocardial infarction at 1 year (Hazard Ratio 2.0).
- The relationship between low magnesium and adverse events was independent of known preoperative and intraoperative risk factors.
Conclusions:
- A significant association exists between low postoperative serum magnesium levels and a doubled incidence of Q-wave infarction and all-cause mortality up to 1 year after CABG.
- This finding highlights the importance of magnesium status in cardiovascular surgery outcomes.
- The results support the need for a randomized controlled trial to evaluate magnesium therapy in CABG patients.
Background:
Despite improved myocardial protection strategies and enhanced surgical techniques, mortality after coronary artery bypass graft surgery (CABG) remains essentially unchanged. This may be because of the increasing age of patients who undergo primary CABG. Magnesium is an important regulator of vascular tone, reperfusion injury, and thrombosis. Therefore, we decided to investigate the relationship between serum magnesium levels and major adverse cardiac events (MACE) after CABG.
Methods:
A total of 957 patients undergoing primary CABG were prospectively recruited into the Duke Cardiovascular database and had daily serum magnesium levels measured. Low magnesium was defined as <1.8 mmol/L(-1) at any point during the first 8 days after surgery. Adverse events were defined as Q-wave infarction or death measured 1 year after surgery. A Kaplan-Meier survival analysis was performed, followed by a Cox proportional hazards model, to account for other known predictors of adverse events.
Results:
In the low magnesium group, 12.3% of patients had adverse events, compared with 9.2% of patients in the normal magnesium group. A serum magnesium level <1.8 mmol/L(-1) decreased the event-free survival rate (2-fold increased risk of death or myocardial infarction at 1 year; hazard ratio 2.0, 95% CI 1.19-3.37).
Conclusions:
We demonstrated a robust relationship between low serum magnesium levels after CABG and a 2-fold increased incidence of Q-wave infarction and all-cause mortality rate as long as 1 year after surgery. This relationship is independent of known preoperative and intraoperative predictors of adverse outcomes. This study provides a rationale for a randomized controlled trial of magnesium therapy during CABG.
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