Can Enalapril (Angiotensin-Converting Enzyme (ACE) inhibitor) be used in patients with Atrioventricular (AV) block?

Use of Enalapril in Patients with AV Block

Enalapril should be used with caution in patients with AV block, and is contraindicated in patients with high-grade AV block unless they have a permanent pacemaker due to the risk of worsening conduction abnormalities.

Mechanism and Cardiac Effects of Enalapril

• Enalapril is an angiotensin-converting enzyme (ACE) inhibitor that decreases blood pressure by lowering peripheral vascular resistance without increasing heart rate or cardiac output 1
• After oral administration, enalapril is rapidly converted by ester hydrolysis to enalaprilat, its active metabolite and potent ACE inhibitor 2
• Approximately 60% of an enalapril dose is absorbed after oral administration, with excretion primarily through the kidneys 2

Contraindications in AV Block

• ACE inhibitors including enalapril should be used with caution in patients with conduction abnormalities, particularly those with AV block 3
• The American College of Cardiology/American Heart Association guidelines specifically list "prolonged first-degree or high-grade AV block" as a contraindication to ACE inhibitor therapy unless the patient has a permanent pacemaker 3
• Caution must be used with dosing of medications that may affect cardiac conduction in patients with potential conduction abnormalities 4

Management Considerations

• In patients with AV block, medications that may worsen conduction should be avoided or used with extreme caution 3
• For patients with AV block who require ACE inhibitor therapy (such as those with heart failure or post-MI):
  • Consider permanent cardiac pacing before initiating enalapril in patients with high-grade AV block 3
  • Start with the lowest possible dose and titrate slowly with careful monitoring 3
  • Monitor ECG regularly for worsening of AV conduction 3

Alternative Medications

• In patients with AV block who require renin-angiotensin system blockade but cannot receive an ACE inhibitor, angiotensin receptor blockers (ARBs) may be considered as an alternative, though they carry similar risks regarding conduction 3
• For patients with heart failure and AV block, careful consideration should be given to the risk-benefit ratio of all medications that affect the cardiac conduction system 3

Special Considerations

• Patients with congenital heart disease and AV conduction abnormalities require particular caution with ACE inhibitors 3
• In patients with hyperdynamic left ventricular function and AV block, beta-blockers would generally be preferred over ACE inhibitors for rate control 4
• The risk of worsening AV block is particularly important in elderly patients and those with underlying structural heart disease 3

Monitoring Recommendations

• Regular ECG monitoring should be performed in patients with known AV block who are receiving enalapril 3
• Patients should be educated about symptoms of worsening AV block, including dizziness, syncope, and worsening fatigue 5
• Dose adjustments may be necessary in patients with renal impairment, as enalaprilat accumulates in patients with creatinine clearances less than 30 mL/min 2