What is the management of patients with ventricular ectopics (premature ventricular contractions) post Coronary Artery Bypass Grafting (CABG)?

Management of Ventricular Ectopics Post-CABG

Lidocaine is the drug of choice for managing ventricular ectopics following CABG surgery, particularly when they are frequent (>6/min), closely coupled, multiform, or occur in short bursts of three or more in succession. 1

Assessment of Ventricular Ectopics

Ventricular ectopics (premature ventricular contractions) are common after CABG surgery. They require treatment when they present as:

• Frequent (>6/min)
• Closely coupled (R on T phenomenon)
• Multiform in configuration
• Occurring in short bursts of three or more in succession 1

Simple ventricular ectopics are common after CABG and generally do not affect prognosis, but sustained ventricular tachycardia/fibrillation occurs infrequently (<2% of patients) and carries a high mortality rate 2.

Management Algorithm

First-Line Treatment

1. Lidocaine administration:

   • Initial IV bolus: 1 mg/kg (not exceeding 100 mg)
   • Additional bolus injections: 0.5 mg/kg every 8-10 minutes if necessary (maximum total: 4 mg/kg)
   • Maintenance infusion: 20-50 μg/kg/min (1.4-3.5 mg/min in a 70 kg patient) 1
   • Patients requiring more than one bolus dose may need higher maintenance doses (40-50 μg/kg/min) 1

2. Continuous ECG monitoring:

   • Should be performed for at least 48 hours in all patients after CABG 1
   • Monitor for heart rate, rhythm, QRS morphology, and ST segments for evidence of ischemia or abnormal conduction

Second-Line Treatment (for refractory cases)

If ventricular ectopics persist despite lidocaine therapy:

1. Amiodarone:

   • Particularly effective for suppressing recurrent VF or hemodynamically unstable VT 3
   • Loading dose: 300 mg over 2 hours followed by 1200 mg/day 3
   • Has been shown to reduce episodes of VT by 85% compared to baseline 3

2. Procainamide:

   • Reserved for documented ventricular arrhythmias that are life-threatening 4
   • Should be used with caution due to potential for serious hematological disorders 4

Management of Precipitating Factors

1. Optimize hemodynamics:

   • Target appropriate heart rate, diastolic or mean arterial pressure, and right/left ventricular end-diastolic pressure 1
   • These measures reduce the risk of perioperative myocardial ischemia and infarction

2. Correct electrolyte abnormalities:

   • Particularly hypokalemia and hypomagnesemia 1
   • Avoid acute preoperative repletion in asymptomatic individuals as risks may outweigh benefits

3. Address myocardial ischemia:

   • Evaluate for incomplete revascularization or graft failure
   • Consider placement of a pulmonary artery catheter in patients with acute hemodynamic instability 1

Special Considerations

1. Sustained ventricular arrhythmias:

   • For ventricular tachycardia or fibrillation resistant to defibrillation, lidocaine is recommended 1
   • Electrical cardioversion should be used for sustained ventricular arrhythmias causing hemodynamic compromise 1

2. Monitoring requirements:

   • Basic perioperative monitoring includes heart rate, blood pressure, peripheral oxygen saturation, and body temperature 1
   • Consider specialized cardiac monitoring in high-risk patients

3. Dosage adjustments:

   • Lidocaine elimination is almost exclusively by the liver
   • Half-life averages 1-2 hours in normal subjects, >4 hours in patients with uncomplicated MI, >20 hours in patients with cardiac failure
   • Lower clearances in patients over 65 years of age (about 100 mL/h/kg vs 150 mL/h/kg in younger patients) 3

Pitfalls and Caveats

1. Avoid prophylactic treatment of asymptomatic ventricular ectopics unless they meet the criteria mentioned above (frequent, closely coupled, multiform, or in bursts)

2. Monitor for lidocaine toxicity, especially in elderly patients and those with liver dysfunction or heart failure

3. Recognize that ventricular arrhythmias may be a sign of underlying issues such as myocardial ischemia, electrolyte disturbances, or hypoxemia

4. Be cautious with antiarrhythmic drugs as they have not been shown to enhance survival in patients with ventricular arrhythmias 4

5. Avoid NSAIDs including COX-2 inhibitors for pain management in post-CABG patients due to associated renal dysfunction and thromboembolic risk 1, 5

By following this structured approach to managing ventricular ectopics post-CABG, clinicians can effectively reduce the risk of progression to more serious arrhythmias while minimizing adverse effects of treatment.