Contraindications for Diltiazem
Diltiazem is absolutely contraindicated in patients with sick sinus syndrome (without a pacemaker), second- or third-degree AV block (without a pacemaker), systolic blood pressure <90 mmHg, acute myocardial infarction with pulmonary congestion, and systolic left ventricular dysfunction with heart failure. 1
Absolute Contraindications
The FDA label explicitly lists the following as absolute contraindications 1:
- Sick sinus syndrome (except with functioning ventricular pacemaker) 1
- Second- or third-degree AV block (except with functioning ventricular pacemaker) 1, 2
- Systolic hypotension (<90 mmHg) 1
- Acute myocardial infarction with pulmonary congestion documented by x-ray 1
- Known hypersensitivity to diltiazem 1
Critical Clinical Contraindications from Guidelines
Heart Failure and Left Ventricular Dysfunction
Diltiazem must be avoided in patients with systolic LV dysfunction and congestive heart failure. 3 The ACC/AHA guidelines explicitly state this as a Class III (Harm) recommendation with Level A evidence in the setting of STEMI 3. The American Heart Association reinforces that diltiazem should be avoided in patients with heart failure and pre-existing systolic dysfunction 4.
However, there is an important distinction: diltiazem is acceptable in heart failure with preserved ejection fraction (HFpEF) as an alternative to beta-blockers 4.
Conduction System Disease
First-degree AV block with PR interval >0.24 seconds is a contraindication for diltiazem and other non-dihydropyridine calcium channel blockers 2. This is particularly important because diltiazem can precipitate complete heart block even in patients with only first-degree block 5, 6.
High-Risk Situations Requiring Extreme Caution
Combination with Beta-Blockers
The combination of diltiazem with beta-blockers significantly increases the risk of severe bradycardia, sinus arrest, and AV block. 5, 6 This combination should not be used in patients with 2:
In one case series, 7 of 9 patients who developed sinus arrest or severe bradycardia requiring hospitalization were on combination therapy with diltiazem and beta-blockers 6.
Renal Impairment
Elderly patients with chronic renal failure are at markedly increased risk for diltiazem toxicity, particularly sinus arrest and severe bradycardia. 7, 8 In one series, all 10 patients who developed persistent sinus arrest on diltiazem had chronic renal failure with mean creatinine clearance of 25 ml/min 7. Diltiazem and its metabolites are partially excreted renally, leading to accumulation in renal dysfunction 8.
Acute Coronary Syndromes
Diltiazem should not be used routinely in acute STEMI or NSTEMI. 3 It may only be considered in highly selected circumstances 3:
- When beta-blockers are contraindicated (e.g., severe bronchospasm) 3
- For ongoing ischemia or rapid atrial fibrillation/flutter control 3
- Only in the absence of CHF, LV dysfunction, or AV block 3
The AHA/ACC guidelines note that nondihydropyridine calcium channel blockers showed detrimental effects on mortality in patients with LV dysfunction in ACS trials 3.
Additional Relative Contraindications
- Cardiogenic shock - diltiazem should be avoided 9
- WPW syndrome with atrial fibrillation/flutter - use with extreme caution 9
- Combination with ivabradine - risk of severe bradycardia 2
- Volume depletion - increased risk of profound hypotension 2
- Age >70 years with heart rate >110 bpm and systolic BP <120 mmHg - increased risk of shock 2
Common Clinical Pitfalls
The most dangerous pitfall is using diltiazem in patients with unrecognized systolic dysfunction or combining it with beta-blockers without careful monitoring 5, 6. Even patients with "uncomplicated hypertension" can develop severe conduction disturbances when diltiazem is combined with beta-blockers 5.
Always check baseline ECG for PR interval, assess LV function, verify renal function, and review all concurrent medications before initiating diltiazem. 5, 7, 8