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Published on: August 8, 2013
Serum magnesium and potassium in acute myocardial infarction: relationship to existing beta-blockade and infarct size
1Department of Internal Medicine, Ullevål University Hospital, Oslo, Norway.
Insights
In acute myocardial infarction (AMI), initial drops in serum magnesium and potassium are linked to beta 2-adrenergic receptor stimulation. Nonselective beta-blockers can prevent these early changes in AMI patients.
Area of Science:
- Cardiology
- Biochemistry
- Pharmacology
Background:
- Acute myocardial infarction (AMI) is a critical cardiovascular event.
- Electrolyte balance, specifically serum magnesium (s-Mg) and potassium (s-K), plays a vital role in cardiac function and response to AMI.
- Early changes in s-Mg and s-K during AMI are not fully understood.
Purpose of the Study:
- To investigate the temporal changes in serum magnesium and potassium levels in the early phase of acute myocardial infarction.
- To explore the influence of time from chest pain onset to sample collection on these electrolyte levels.
- To determine the effect of nonselective beta-blockers on these early electrolyte shifts in AMI patients.
Main Methods:
- A cohort of 314 patients with AMI was divided into three groups based on the time of initial blood sampling (0-6, 6-10, and 10-24 hours post-chest pain onset).
- Serum magnesium (s-Mg) and potassium (s-K) were measured in acute (s-Mg1, s-K1) and convalescent (s-Mg2, s-K2) samples.
- Changes in electrolytes (delta s-Mg, delta s-K) were correlated with peak creatine kinase (CKmax) levels and beta-blocker use.
Main Results:
- Serum Mg was lower in the initial sample (s-Mg1) compared to the later sample (s-Mg2) across all groups.
- Serum K was reduced in the initial sample (s-K1) only in the earliest group (0-6 hours).
- Nonselective beta-blockers attenuated the drop in s-Mg1 and completely inhibited the drop in s-K1 in the early AMI phase. Electrolyte changes correlated with CKmax levels.
Conclusions:
- The initial decrease in serum magnesium and potassium during the early phase of AMI is likely mediated by increased beta 2-adrenergic receptor stimulation.
- Nonselective beta-blockers can prevent or mitigate these early electrolyte changes in AMI patients.
- These findings highlight the role of adrenergic activity in electrolyte shifts during AMI and the potential protective effect of beta-blockade.
Abstract:
Patients (n = 314) with acute myocardial infarction (AMI) were divided into three groups according to the time elapsed from onset of chest pain to when the first sample for determination of magnesium (s-Mg1) and potassium (s-K1) was drawn (A: hours 0-6; B: hours 6-10, and C: hours 10-24). Potassium and Mg were also measured in a second sample drawn three to twelve days (mean 6.3 days) later (s-Mg2, s-K2). Whereas s-Mg1 was lower than s-Mg2 in all three groups, s-K1 was reduced only in group A. Ten patients in group A receiving nonselective beta-blockers had an attenuated drop in s-Mg1, whereas the drop in s-K1 was completely inhibited. The differences between s-Mg2 and s-Mg1 (delta s-Mg) in all groups, and between s-K2 and s-K1 (delta s-K) in group A, increased with increasing mean peak creatine kinase (CKmax) levels to approximately 1300-1800 U/L. In conclusion, these observations suggest that the initial drop in s-Mg and s-K in the early phase of AMI is due to increased stimulation of beta 2-adrenergic receptors; these changes can be prevented partly or completely by the use of nonselective beta-blockers.
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