What does PAT (Paroxysmal Atrial Tachycardia) stand for in cardiology?

What Does PAT Stand for in Cardiology?

PAT stands for Paroxysmal Atrial Tachycardia, which is a clinical syndrome characterized by the presence of a regular and rapid tachycardia with abrupt onset and termination. 1

Definition and Classification

PAT is now considered part of the broader category of Paroxysmal Supraventricular Tachycardia (PSVT), which includes:

• Atrioventricular nodal reentrant tachycardia (AVNRT)
• Atrioventricular reentrant tachycardia (AVRT)
• Less frequently, focal atrial tachycardia (AT)

According to current guidelines, PSVT represents a subset of supraventricular tachycardias (SVT) that have the characteristic features of abrupt onset and termination 1.

Clinical Characteristics

• Heart Rate: Typically 150-250 beats per minute 2
• Rhythm: Regular
• QRS Complex: Usually narrow
• P Wave: Often hidden within the QRS complex
• Symptoms: Palpitations (86%), chest discomfort (47%), dyspnea (38%), dizziness, and occasionally syncope 3
• Demographics: Affects 168-332 per 100,000 individuals, with approximately 67.5% being female 3

Mechanism

PAT is primarily caused by reentry mechanisms, where electrical impulses circulate continuously through a defined circuit. The two main mechanisms include:

1. AV Nodal Reentry (AVNRT): Most common form, involving two conducting pathways within the AV nodal and perinodal atrial tissue 2
2. AV Reciprocating Tachycardia (AVRT): Involves an accessory pathway that bypasses the AV node 2

Diagnostic Features

The diagnosis of PAT/PSVT is made by:

• 12-lead ECG during an arrhythmic event
• Ambulatory monitoring
• Characteristic features include abrupt onset and termination
• Regular rhythm with narrow QRS complexes (unless aberrant conduction is present)

Management

Acute Management

1. For hemodynamically unstable patients: Immediate synchronized cardioversion 4
2. For stable patients:
   • Vagal maneuvers (43% effective) - modified Valsalva maneuver is preferred 3
   • Intravenous adenosine (91% effective) as first-line pharmacological therapy 3
   • Alternative medications: non-dihydropyridine calcium channel blockers or beta-blockers 4

Long-term Management

1. Catheter ablation: Recommended as first-line therapy for recurrent episodes with success rates of 94.3-98.5% 3
2. Pharmacotherapy options:
   • Beta-blockers
   • Non-dihydropyridine calcium channel blockers
   • Antiarrhythmic agents

Important Considerations

• PAT with second-degree AV block may occur spontaneously even in structurally normal hearts 5
• PAT episodes can interfere with response to cardiac resynchronization therapy in heart failure patients 6
• Untreated PSVT can lead to tachycardia-mediated cardiomyopathy in approximately 1% of cases 3
• The occurrence of PAT episodes follows a Poisson process (exponential probability distribution), meaning the time intervals between attacks are uncorrelated 7

Evolution of Terminology

It's worth noting that the term PAT has evolved over time. In current practice and guidelines, the term PSVT is more commonly used to describe the clinical syndrome previously known as PAT. Modern electrophysiological classification is more specific about the underlying mechanisms rather than using the broader term PAT.