Diltiazem Should Be Avoided in Patients with Congestive Heart Failure
Diltiazem is contraindicated in patients with heart failure with reduced ejection fraction (HFrEF) and should be discontinued unless absolutely necessary due to its negative inotropic effects that can worsen heart failure outcomes. 1, 2
Guideline-Based Contraindication
The European Society of Cardiology explicitly classifies diltiazem among "treatments that may cause harm in patients with symptomatic heart failure with reduced ejection fraction," with a Class III recommendation (harm). 2 The guidelines state that calcium-channel blockers should be discontinued unless absolutely necessary, and diltiazem and verapamil are potentially harmful because of their negative inotropic effect. 1
The American Heart Association similarly recommends that nondihydropyridine calcium channel blockers (including diltiazem and verapamil) should be avoided in patients with HF and hypertension (Class III: Harm). 1
FDA Warning on Congestive Heart Failure
The FDA drug label for diltiazem explicitly warns: "Although diltiazem has a negative inotropic effect in isolated animal tissue preparations, hemodynamic studies in humans with normal ventricular function have not shown a reduction in cardiac index nor consistent negative effects on contractility. Experience with the use of diltiazem hydrochloride alone or in combination with beta-blockers in patients with impaired ventricular function is very limited. Caution should be exercised when using the drug in such patients." 3
Evidence of Harm in Heart Failure Patients
Long-term Outcomes
- Patients with reduced ejection fraction (<0.40) taking diltiazem after myocardial infarction had significantly higher rates of late-onset congestive heart failure (21% vs 12% on placebo, p=0.004). 4
- The diltiazem-associated increase in CHF was progressively greater with increasingly severe decrements in baseline ejection fraction. 4
Acute Management Concerns
- In emergency department patients with HFrEF and atrial fibrillation, diltiazem resulted in a significantly higher incidence of worsening heart failure symptoms compared to metoprolol (33% vs 15%, p=0.019). 5
- Worsening symptoms included increased oxygen requirements within 4 hours or need for inotropic support within 48 hours. 5
Preferred Alternatives for Rate Control
Beta-blockers are the preferred agents for rate control in heart failure patients with atrial fibrillation. 2 The ESC guidelines recommend:
- First-line: Beta-blockers (evidence-based agents like carvedilol, bisoprolol, or metoprolol succinate) 2
- Second-line: Digoxin (can be used alone or in combination with beta-blockers) 2
- For rhythm control in severe HF: Amiodarone 2
Clinical Pitfalls to Avoid
When Diltiazem Might Be Considered (Rare Exception)
In hypertrophic cardiomyopathy (HCM) patients who do not tolerate verapamil or in whom verapamil is contraindicated, diltiazem may be considered (Class IIb). 1 However, this is a distinct condition from systolic heart failure.
Critical Monitoring if Diltiazem Cannot Be Avoided
If diltiazem must be used in the acute setting for rapid rate control:
- Monitor closely for hypotension (systolic BP <90 mmHg) 5
- Watch for bradycardia (HR <60 bpm) 1
- Assess for increased oxygen requirements within 4 hours 5
- Evaluate need for inotropic support within 48 hours 5
- Avoid combination with beta-blockers due to additive negative effects on cardiac conduction 3
Management of Bradycardia or Hypotension
If heart rate falls below 50 bpm with worsening symptoms:
- Review and discontinue other heart rate-slowing drugs (digoxin, amiodarone, diltiazem, verapamil) 1
- Arrange ECG to exclude heart block 1
- Seek specialist advice 1
For symptomatic hypotension with dizziness or confusion:
- Reconsider need for calcium-channel blockers and other vasodilators and reduce/stop if possible 1