What are the contraindications to diltiazem (calcium channel blocker)?

Contraindications to Diltiazem

Diltiazem is absolutely contraindicated in patients with sick sinus syndrome, second or third-degree AV block without a functioning ventricular pacemaker, hypotension (systolic BP <90 mmHg), hypersensitivity to the drug, and acute myocardial infarction with pulmonary congestion documented by x-ray on admission. 1

Cardiovascular Contraindications

Conduction System Disorders

• Sick sinus syndrome (without a functioning ventricular pacemaker) 1
• Second or third-degree AV block (without a functioning ventricular pacemaker) 1
• Pre-excitation syndromes (e.g., Wolff-Parkinson-White syndrome) 2, 3
  • Diltiazem can facilitate antegrade conduction through accessory pathways during atrial fibrillation, potentially causing dangerous acceleration of ventricular rate

Cardiac Function Disorders

• Decompensated heart failure 3
• Severe left ventricular dysfunction 3
• Cardiogenic shock 3
• Hypotension (systolic BP <90 mmHg) 1
• Acute myocardial infarction with pulmonary congestion 1

Special Precautions and Relative Contraindications

Concomitant Medications

• Caution with beta-blockers: Combination significantly increases risk of:
  • Bradycardia
  • Heart block
  • Hypotension 4
  • Worsening heart failure 3

Cardiac Conditions Requiring Careful Monitoring

• First-degree AV block (requires careful monitoring) 3
• Bradycardia (heart rate <60 bpm)
• Left ventricular dysfunction (LVEF <40%) 2
  • Non-dihydropyridine calcium channel blockers like diltiazem can have negative inotropic effects 2

Specific Clinical Scenarios Where Diltiazem is Contraindicated

Atrial Fibrillation in Special Populations

• Atrial fibrillation with WPW syndrome 2
  • Intravenous administration of non-dihydropyridine calcium channel antagonists is specifically contraindicated in this population 2

Acute Coronary Syndromes

• In NSTE-ACS patients with:
  • Clinically significant LV dysfunction
  • Increased risk for cardiogenic shock
  • PR interval >0.24 seconds
  • Second or third-degree heart block without pacemaker 2

Heart Failure

• Diltiazem is contraindicated in heart failure due to systolic dysfunction 2
• Particularly contraindicated when used in addition to beta-blockade in heart failure patients 2

Monitoring Recommendations When Using Diltiazem

When diltiazem is used in patients without absolute contraindications but with potential risk factors:

• Monitor for bradycardia, hypotension, and signs of worsening heart failure 3
• Continuous cardiac monitoring for patients receiving IV diltiazem 3
• Monitor blood pressure, heart rate, and AV conduction on ECG when combined with beta-blockers 4
• Avoid fluid boluses to counteract diltiazem-induced hypotension, especially in patients with heart failure 3

Alternative Agents When Diltiazem is Contraindicated

• For rate control in atrial fibrillation with LV dysfunction: beta-blockers or digoxin 2
• For hypertension with LV dysfunction: ACE inhibitors, ARBs, or dihydropyridine calcium channel blockers 2
• For angina with LV dysfunction: nitrates and beta-blockers 2

Understanding these contraindications is essential for safe prescribing of diltiazem across various clinical scenarios.