Can I start a Cardizem (Diltiazem) drip in a patient with an unknown ejection fraction?

Using Diltiazem Drip in Patients with Unknown Ejection Fraction

Diltiazem drip can be used in patients with unknown ejection fraction, but caution is warranted as it may worsen hemodynamics in patients with significantly reduced ejection fraction (<40%).

Considerations Based on Cardiac Function

When Diltiazem is Appropriate:

• Diltiazem is reasonable for ongoing management in patients with symptomatic focal atrial tachycardia 1
• Diltiazem can be used in patients with preserved ejection fraction (≥50%) and heart failure symptoms without left ventricular outflow tract obstruction (LVOTO) 1
• Diltiazem is particularly useful for rate control in atrial fibrillation/flutter 2

When Diltiazem Should Be Avoided:

• Diltiazem should not be used in patients with known reduced ejection fraction (<50%) as it has negative inotropic effects that can worsen heart failure 1
• Particular caution is needed in patients with clinical evidence of hypotension associated with hypoperfusion 1

Decision Algorithm for Diltiazem Use with Unknown EF

1. Assess for contraindications:

   • Signs of cardiogenic shock or hypoperfusion
   • Clinical evidence of severe heart failure
   • Known severe left ventricular dysfunction

2. Evaluate clinical context:

   • If treating supraventricular tachycardia or atrial fibrillation/flutter without signs of severe heart failure, diltiazem may be appropriate
   • If patient has signs suggesting reduced EF (S3 gallop, elevated JVP, pulmonary edema), consider alternative agents

3. Administration approach if proceeding:

   • Start with lower initial bolus dose (0.15-0.25 mg/kg) 3
   • Monitor closely for hypotension and worsening heart failure symptoms
   • Consider starting at lower infusion rate (5 mg/h) rather than standard 10 mg/h 3
   • Have vasopressors readily available

Monitoring During Diltiazem Administration

• Continuous cardiac monitoring
• Frequent blood pressure checks (every 5-15 minutes initially)
• Close observation for signs of worsening heart failure:
  • Increased respiratory distress
  • Worsening oxygen saturation
  • Decreased urine output
  • Increasing pulmonary rales

Alternative Approaches

If there is high clinical suspicion for reduced ejection fraction:

• Consider obtaining a bedside echocardiogram before starting diltiazem if patient is stable enough
• Consider alternative agents like amiodarone for rate control in suspected reduced EF
• Beta-blockers may be preferable in some cases, though they also have negative inotropic effects

Important Caveats

• The negative inotropic effects of diltiazem can precipitate heart failure in patients with borderline cardiac function
• Combination with beta-blockers increases risk of atrioventricular block 2
• Diltiazem shows dose-dependent, non-linear pharmacokinetics; infusion duration exceeding 24 hours and rates exceeding 15 mg/h are not recommended 3

In emergency situations requiring immediate rate control when EF is unknown, using diltiazem with careful monitoring is reasonable, but obtaining information about cardiac function as soon as possible is essential for ongoing management decisions.