What is electrophysiology?

What is Electrophysiology?

Electrophysiology is an invasive diagnostic and therapeutic subspecialty of cardiology that uses intracardiac electrode catheters to record electrical signals, stimulate cardiac tissue, and evaluate the heart's electrical properties—including automaticity, conduction, and refractoriness—to diagnose and treat cardiac arrhythmias. 1

Core Procedural Components

Electrophysiological studies (EPS) involve the placement of multiple electrode catheters through intravenous or intra-arterial access into specific cardiac chambers (atria, ventricles, coronary sinus, or occasionally pulmonary artery/aorta) to record intracardiac electrical signals and deliver programmed electrical stimulation at various rates and patterns. 1

The procedure evaluates three fundamental electrical properties:

• Automaticity: Assessment of pacemaker cell function and abnormal spontaneous depolarization 2
• Conduction: Measurement of electrical impulse propagation through cardiac tissue 1
• Refractoriness: Evaluation of tissue recovery time after depolarization 1

Primary Clinical Applications

Diagnostic Functions

EPS serves as the gold standard for diagnosing most tachyarrhythmias when ECG diagnosis remains uncertain. 1 The American College of Cardiology/American Heart Association guidelines establish that electrophysiological data provide definitive diagnosis by:

• Initiating and terminating tachycardias to confirm arrhythmia mechanisms 1
• Mapping activation sequences during arrhythmias to identify arrhythmogenic substrates 1, 3
• Evaluating bradyarrhythmias (sinus node dysfunction, AV block, intraventricular conduction delay) when standard ECG recordings are nondiagnostic 1
• Assessing unexplained syncope in patients with structural heart disease, where arrhythmias are more likely causative 1

Therapeutic Applications

The advent of radiofrequency catheter ablation has transformed electrophysiology from purely diagnostic to definitively therapeutic. 1 The ACC/AHA guidelines designate catheter ablation as a primary treatment option for:

• Paroxysmal supraventricular tachycardias and preexcitation syndromes (high success, low complication rates) 1
• Monomorphic ventricular tachycardia in structurally normal hearts 1
• Selected atrial tachyarrhythmias (atrial tachycardia, atrial flutter, atrial fibrillation—though with more selective use due to limited long-term efficacy data) 1

Specific Clinical Indications

Class I Indications (Definite Benefit)

The ACC/AHA Task Force establishes that EPS provides information "useful and important for patient treatment" in: 1

• Cardiac arrest survivors without acute Q-wave MI or occurring >48 hours post-MI 1
• Symptomatic patients with suspected sinus node dysfunction when causal relationship between arrhythmia and symptoms remains unestablished 1
• Patients with unexplained palpitations preceding syncope when ECG recordings fail to document the cause 1
• Evaluation for implantable cardioverter-defibrillators in ventricular tachyarrhythmia patients 1

Class II Indications (Uncertain Benefit)

EPS is frequently performed but with divided expert opinion regarding benefit for: 1

• Cardiac arrest survivors caused by bradyarrhythmia 1
• Patients with clinically significant palpitations of suspected cardiac origin when symptoms are sporadic and cannot be documented 1

Class III Indications (No Benefit)

EPS is not warranted in: 1

• Cardiac arrest during acute MI phase (<48 hours) 1
• Palpitations documented due to extracardiac causes (e.g., hyperthyroidism) 1
• Cardiac arrest from clearly reversible causes (severe aortic stenosis, noninvasively defined long QT syndrome) 1

Procedural Considerations and Safety

EPS carries finite risk of major and minor complications, routinely involves purposeful induction of serious arrhythmias, and consumes healthcare resources. 1 The ACC recommends absolute contraindications include: 3

• Unstable angina
• Bacteremia/septicemia
• Acute decompensated heart failure (not arrhythmia-caused)
• Major bleeding disorders
• Lower extremity venous thrombosis

Fluoroscopy has traditionally been the primary imaging modality, but electroanatomic 3D mapping and intracardiac echocardiography can reduce radiation exposure following the ALARA (as low as reasonably achievable) principle. 3

Diagnostic Yield and Prognostic Value

In patients with structural heart disease (particularly prior MI), EPS has high diagnostic yield for identifying arrhythmogenic substrates. 1 Conversely, in patients without structural heart disease and normal ECG, diagnostic yield is relatively low. 1

Sustained monomorphic ventricular tachycardia can be initiated in >90% of patients with prior MI and sustained VT history, though induction rates are lower in cardiac arrest survivors and those with nonsustained VT. 1

Patients with no abnormalities during EPS have low incidence of sudden death during follow-up, suggesting prognostic value of negative testing. 1

Evolution and Current Practice

Cardiac electrophysiology became a cardiology subspecialty in the mid-1990s due to rapid equipment development allowing percutaneous study and cure of arrhythmias. 4 The field has evolved from purely diagnostic evaluation of bradyarrhythmias and tachyarrhythmias to include therapeutic interventions, with recent focus on ablative treatment of atrial fibrillation and management of inherited arrhythmias through genetic understanding. 4

Most procedures are performed electively with same-day discharge for uncomplicated cases, with monitoring for bleeding, vascular complications, and arrhythmia recurrence. 3

Critical Pitfalls

Inadequate mapping leads to unsuccessful ablation or recurrence, and failure to recognize anatomical variations increases procedural risk. 3 The ACC emphasizes that studies must be performed by appropriately trained personnel in adequately equipped laboratories, with complete studies tailored to the patient's clinical state and specific arrhythmia. 1