Diltiazem Should Generally 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 and increase mortality. 1, 2
Guideline-Based Contraindications
The evidence against diltiazem use in heart failure is clear and consistent:
The European Society of Cardiology issues a Class III recommendation (harm) against calcium channel blockers including diltiazem in symptomatic HFrEF patients, explicitly stating these agents should be discontinued unless absolutely necessary 1, 2
The American Heart Association similarly recommends against nondihydropyridine calcium channel blockers (including diltiazem) in heart failure patients with hypertension, also with a Class III (harm) recommendation 2
The FDA drug label warns that while diltiazem has negative inotropic effects in isolated tissue preparations, experience using diltiazem in patients with impaired ventricular function is very limited and caution should be exercised 3
Clinical Evidence of Harm
The concern about diltiazem in heart failure is not theoretical:
In the Multicenter Diltiazem Postinfarction Trial, patients with baseline ejection fraction <40% who received diltiazem had significantly higher rates of late-onset congestive heart failure (21% vs 12% on placebo, p=0.004), with progressively greater harm at lower ejection fractions 4
A 2022 retrospective study found that HFrEF patients with atrial fibrillation treated with IV diltiazem had significantly higher rates of worsening heart failure symptoms compared to metoprolol (33% vs 15%, p=0.019), defined as increased oxygen requirements within 4 hours or need for inotropic support within 48 hours 5
A 2024 study demonstrated that among hospitalized patients, those with reduced EF (<50%) who received diltiazem had a 17% incidence of worsening heart failure within 24 hours, compared to only 4.8% in those with preserved EF (p=0.005) 6
Preferred Alternatives for Rate Control
When rate control is needed in heart failure patients:
Beta-blockers are the preferred first-line agents for rate control in heart failure patients with atrial fibrillation, as they reduce mortality and morbidity while providing rate control 1, 2
Evidence-based beta-blockers include carvedilol, bisoprolol, or metoprolol succinate, which have proven mortality benefits in HFrEF 2
Digoxin can be used as an adjunct to beta-blockers or alone when beta-blockers are contraindicated, particularly in patients with volume overload 1
IV amiodarone plus digoxin is preferred over diltiazem in hemodynamically unstable patients 1
Limited Exception: Heart Failure with Preserved Ejection Fraction (HFpEF)
There is one narrow clinical scenario where diltiazem may be considered:
Diltiazem may be used only in confirmed HFpEF (preserved EF ≥50%) where echocardiography has documented normal systolic function and the patient is hemodynamically stable 1, 2
In HFpEF, calcium channel blockers can be employed for blood pressure control, though they do not reduce HF-specific morbidity or mortality 2
Even in HFpEF, nondihydropyridine calcium channel blockers may be more effective when combined with digoxin rather than used alone 7
Critical Safety Warnings
Several important pitfalls must be avoided:
Never combine diltiazem with beta-blockers in any heart failure patient, as this increases the risk of bradycardia and heart block through additive negative effects on cardiac conduction 1, 2
When managing bradycardia in heart failure patients on beta-blockers, review and discontinue other heart rate-slowing drugs including diltiazem 7
If diltiazem must be used acutely for rapid rate control before EF is known, monitor closely for hypotension, bradycardia, increased oxygen requirements, and need for inotropic support 1
Treating congestion and optimizing hemodynamics takes precedence over rate control in acute CHF 1
Contradictory Evidence Requiring Context
One older study from 1984 showed short-term hemodynamic benefits of diltiazem in severe heart failure, with improved cardiac index and reduced pulmonary wedge pressure 8. However, this study:
- Only evaluated acute hemodynamic effects over 24 hours, not clinical outcomes
- Observed transient junctional arrhythmias in 3 of 8 patients with IV diltiazem
- Predates the large-scale trials demonstrating harm with longer-term use 4
- Is superseded by current guideline recommendations against diltiazem in HFrEF 1, 2
The weight of evidence, including contemporary guidelines and outcome studies, clearly supports avoiding diltiazem in heart failure patients with reduced ejection fraction.