The Role of ECG in Triaging for Cardiac Electrophysiology Procedures

ECG can be used to triage patients who require urgent or emergent cardiac electrophysiology procedures when they present to the emergency department with signs of an arrhythmia or the need for an adjustment to a cardiovascular implantable electronic device (CIED) like a pacemaker or a change in QT due to a drug to control arrhythmia.

Guidance issued in 2020 by the Heart Rhythm Society, the American College of Cardiology, and the American Heart Association (HRS/ACC/AHA) notes that more than 40% of cardiology encounters are related to arrhythmia.¹ This finding highlights the importance of ECG and the need for electrophysiologists on the care team.

Defining Urgent and Emergent Procedures

According to the HRS/ACC/AHA authors, procedures are deemed urgent or emergent if they have a major impact on reducing risks of clinical decompensation, hospitalization, or death. Procedures that fit this definition include cardioversion for highly symptomatic atrial arrhythmias or drug refractory rapid ventricular rates, as well as transesophageal echocardiography prior to an urgent cardioversion. Catheter ablation is also urgent in the following scenarios:

• Ventricular tachycardia (VT) ablation for an electrical storm unresponsive to medical therapy in a patient with hemodynamic compromise
• Afib, atrial flutter, or atrioventricular nodal ablation if the arrhythmias are hemodynamically significant, severely symptomatic, and unresponsive to antiarrhythmic drugs, rate control, and cardioversion
• Wolff-Parkinson-White (WPW) syndrome or preexcited Afib with syncope or cardiac arrest

Several CIED-related situations are also considered urgent or emergent:

• Lead revision driven by malfunction in an ICD or pacemaker-dependent patient who is receiving inappropriate therapy
• Generator change in a pacemaker-dependent patient with an elective replacement indicator or at the end of the device's life, or for a device with minimal battery remaining
• Implantation of a secondary prevention ICD
• Implantation of a pacemaker for symptomatic complete heart block, Mobitz II or high-grade atrioventricular block, or severely symptomatic sinus node dysfunction with long pauses
• Lead/device extraction for infection, including endocarditis, bacteremia, or pocket infection
• Cardiac resynchronization therapy for severe refractory heart failure

Similar guidance from the Latin American Heart Rhythm Society lists additional procedures considered emergent or semi-urgent, such as catheter ablation for incessant VT refractory to drugs, recurrent VT leading to multiple hospitalizations or ICD shocks, and paroxysmal Afib/atrial flutter or recurrent supraventricular tachycardia requiring frequent hospitalizations.²

How ECG Can Help

A collection of patient scenarios in the Journal of Emergencies, Trauma, and Shock identified several instances when emergency catheter ablation would be warranted in critically ill patients. These include WPW syndrome with a risk of sudden cardiac death, incessant VT related to ischemic cardiomyopathic shock, electrical storm in an ICD patient, and idiopathic VF.³

One case in particular highlights the key role of ECG in the triage of cardiac electrophysiology procedures. In that case, a 31-year-old woman developed syncope and stopped breathing. After her husband resuscitated her, she was taken to the emergency department, where she was diagnosed with ventricular fibrillation (VF). Defibrillation restored normal rhythm.

After 3 days of intensive care, a 12-lead ECG revealed preexcitation syndrome "with a suspected accessory pathway at the inferoseptal aspect," the authors report. The patient was taken to another center for catheter ablation of the accessory pathway, which was successful. She did not have an ICD implanted at that point because there was no family history of cardiac arrest, normal echocardiographic findings, and no abnormalities on a 12-lead ECG performed after ablation.

In another case series published in EP Europace, urgent radiofrequency catheter ablation was performed in patients with acute decompensated heart failure after sustained ventricular tachyarrhythmias were detected by 12-lead surface ECG.4 The procedure completely suppressed sustained VT/VF in 80% of patients, and acute heart failure was resolved in 93% of patients.