Diltiazem Should Be Avoided in Patients with Low Ejection Fraction
Diltiazem (Cardizem) is contraindicated or should be avoided in patients with heart failure with reduced ejection fraction (HFrEF) due to its negative inotropic effects, which increase the risk of clinical deterioration, worsening heart failure, and acute kidney injury. 1, 2
Why Diltiazem is Problematic in Low EF
Guideline Recommendations Against Use
The European Society of Cardiology explicitly recommends avoiding diltiazem or verapamil in HFrEF as they increase the risk of worsening heart failure and hospitalization. 2
The 2011 ACC/AHA/HRS guidelines state that nondihydropyridine calcium channel antagonists (diltiazem and verapamil) "should be used cautiously or avoided in patients with HF due to systolic dysfunction." 1
The 2024 ESC guidelines for chronic coronary syndromes note that "CCBs require caution in patients with heart failure with reduced ejection fraction (HFrEF)." 1
Mechanism of Harm
The FDA drug label warns that "diltiazem has a negative inotropic effect in isolated animal tissue preparations" and states "caution should be exercised when using the drug in such patients" with impaired ventricular function. 3
Diltiazem's negative inotropic effects can precipitate hemodynamic decompensation in patients with already compromised cardiac function. 3
Evidence of Clinical Harm
Recent High-Quality Evidence (2024)
A 2024 multi-hospital study found that patients with EF ≤40% who received diltiazem despite a clinical decision support alert had significantly higher rates of clinical deterioration (33% vs 21%, P=0.044), including increased need for inotropes/vasopressors and ICU transfer. 4
A 2024 emergency department study showed that among patients with reduced EF (<50%), worsening heart failure occurred in 17% of admitted patients who received IV diltiazem, compared to 4.8% with preserved EF (P=0.005). 5
Additional Supporting Evidence
A 2022 study comparing diltiazem to metoprolol in HFrEF patients with atrial fibrillation found diltiazem had a significantly higher incidence of worsening heart failure symptoms (33% vs 15%, P=0.019), defined as increased oxygen requirements within 4 hours or need for inotropic support within 48 hours. 6
A 2018 retrospective study found significantly higher rates of acute kidney injury within 48 hours in low EF patients receiving diltiazem (10% vs 3.6%, P=0.002). 7
What to Use Instead
For Rate Control in Atrial Fibrillation with Low EF
Beta-blockers (carvedilol, metoprolol succinate, or bisoprolol) are the preferred agents for rate control in HFrEF patients with atrial fibrillation, achieving rate control endpoints in 70% of patients. 1, 2
Digoxin can be used in patients with HFrEF and low ejection fraction, particularly when combined with beta-blockers, though it is less effective as monotherapy. 1
Amiodarone can be useful for rate control when other measures are unsuccessful or contraindicated, though it has multiple side effects and drug interactions. 1
For Angina in Low EF Patients
Beta-blockers remain first-line for angina control in HFrEF patients. 1, 2
Long-acting nitrates, ranolazine, or trimetazidine are reasonable alternatives when beta-blockers are contraindicated or poorly tolerated. 1
Ivabradine can be added for patients in sinus rhythm with heart rate ≥70 bpm despite maximally tolerated beta-blocker therapy. 1, 2
Critical Caveats
When Diltiazem Might Be Considered (Rare Exceptions)
The only scenario where diltiazem showed potential benefit in severe heart failure was a small 1984 study (8 patients, mean EF 26%) showing improved hemodynamics with careful IV infusion, but this was accompanied by transient junctional arrhythmias in 3 of 8 patients and requires extreme caution. 8
This historical data is vastly outweighed by modern evidence showing harm and should not guide routine practice. 5, 4, 6
Common Pitfalls to Avoid
Do not use diltiazem for acute rate control in the emergency department for patients with known or suspected low EF, even if it seems convenient or familiar. 5, 4, 6
Do not assume that brief exposure to diltiazem is safe—clinical deterioration can occur within hours of administration. 5, 6
Do not combine diltiazem with beta-blockers in any patient, as this creates additive effects on cardiac conduction and increases risk of heart block. 3
Monitor for acute kidney injury if diltiazem was inadvertently given to a low EF patient, as this complication occurs more frequently in this population. 7