• Evaluation of tachycardia mechanism, in preparation for catheter ablation procedure.

• Evaluation of wide QRS tachycardia, where ECG interpretation does not clarify mechanism of tachycardia.

• Evaluation of sudden cardiac arrest.

• Evaluation of unexplained syncope.

• Risk stratification for risk of cardiac arrest in patients with repaired congenital heart disease.

• Evaluation of conduction system, or risk of tachycardia, particularly prior to surgery for congenital heart disease.

• Lack of vascular access.

• Cardiac catheterization laboratory; nursing and technical support staff.

• Biplane fluoroscopy.

• Electrode catheters, usually multiple, with recording equipment.

• Sedation and intravenous access as necessary.

• Cardiac defibrillator.

• Resuscitation medications.

• Vascular injury, peripheral or coronary.

• Bleeding.

• Infection.

• Pneumothorax.

• Cardiac perforation.

• Thromboembolism.

• Initiation of hemodynamically unstable arrhythmia, or conversion of one mechanism of tachycardia into another tachycardia.

• Arrhythmias may require direct current cardioversion or defibrillation.

• Radiation exposure.

• Risk of death: < 0.5%.