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Angiotensin converting enzyme inhibitors and magnesium conservation in patients with congestive cardiac failure
R N Stevenson1, C Keywood, A A Amadi
1Cardiac Department, Whittington Hospital, London.
Insights
Angiotensin converting enzyme inhibitors significantly reduce magnesium loss in patients with congestive cardiac failure taking diuretics. This magnesium conserving action may be linked to their effect on glomerular filtration rate.
Area of Science:
- Cardiology
- Pharmacology
- Nephrology
Background:
- Diuretics are commonly prescribed for congestive cardiac failure (CCF).
- Diuretic therapy can lead to increased magnesium excretion, potentially causing hypomagnesemia.
- The impact of angiotensin converting enzyme (ACE) inhibitors on diuretic-induced magnesium loss in CCF is not well understood.
Purpose of the Study:
- To determine if ACE inhibitors reduce magnesium excretion in patients with CCF who are receiving diuretic treatment.
- To explore the relationship between ACE inhibitors, magnesium balance, and renal function in this patient population.
Main Methods:
- A cohort analytic study was conducted at a London district general hospital.
- Thirty-four patients with chronic CCF were divided into two groups: 19 on diuretics alone and 15 on diuretics plus an ACE inhibitor (enalapril or captopril).
- Urine magnesium and creatinine clearance were measured over 24 hours after an intravenous magnesium sulphate loading dose.
Main Results:
- Patients receiving ACE inhibitors (group 2) showed significantly lower 24-hour urine magnesium excretion compared to those on diuretics alone (group 1).
- Creatinine clearance was also significantly lower in group 2 and correlated with magnesium excretion, a relationship not observed in group 1.
- No significant difference in the fractional clearance of magnesium was found between the two groups.
Conclusions:
- ACE inhibitors possess a significant magnesium-conserving effect in patients with CCF on diuretics.
- This effect is potentially mediated through the influence of ACE inhibitors on glomerular filtration rate.
Objective:
To investigate whether angiotensin converting enzyme inhibitors reduce diuretic induced magnesium excretion in patients in congestive cardiac failure.
Design:
Cohort analytic study.
Setting:
A London district general hospital.
Subjects:
Thirty four patients with chronic congestive cardiac failure caused by ischaemic heart disease or cardiomyopathy selected consecutively from inpatients under the care of two consultant cardiologists. Nineteen patients (group 1) on diuretics alone were compared with 15 patients (group 2) taking diuretics plus either enalapril or captopril. All drug regimens were stable for at least three months before the study. Patients with impaired renal function (plasma creatinine greater than 120 mumol/l) were excluded.
Interventions:
An intravenous loading dose of magnesium sulphate was given to minimise the variability in baseline magnesium state.
Main Outcome Measure:
Total urine magnesium excretion and creatinine clearance in 24 hour urine collections.
Results:
Plasma magnesium was similar in the two groups. However, 24 hour urine magnesium excretion was significantly lower in group 2 than in group 1. Furthermore, creatinine clearance was also significantly lower in group 2 and correlated strongly with magnesium excretion. There was no such relation in group 1. There was no difference in fractional clearance of magnesium between groups.
Conclusion:
Angiotensin converting enzyme inhibitors have an important magnesium conserving action, possibly via their effect on glomerular filtration rate.