What is the diagnosis for a patient with chest heaviness, tachycardia, and saw tooth P-waves on ECG (electrocardiogram) with a regular heart rhythm?

Diagnosis: Atrial Flutter with 2:1 AV Block

The diagnosis is atrial flutter, specifically typical atrial flutter with 2:1 atrioventricular block, which explains the saw-tooth P-waves (flutter waves) combined with a regular ventricular rhythm and tachycardia.

ECG Characteristics That Confirm This Diagnosis

The combination of findings described is pathognomonic for atrial flutter with fixed AV conduction:

• Saw-tooth pattern (flutter waves) is the hallmark ECG finding of typical atrial flutter, particularly visible in leads II, III, aVF, and V1 1, 2
• Regular heart rhythm occurs when atrial flutter presents with fixed AV block (commonly 2:1), distinguishing it from atrial fibrillation which has an irregular ventricular response 1, 2
• Elevated heart rate of 120-160 bpm (most characteristically about 150 bpm) results from 2:1 AV block when the atrial rate is 240-320 bpm 1

Why This Is NOT Atrial Fibrillation

This is a critical distinction that clinicians must recognize:

• Atrial fibrillation is characterized by completely irregular ventricular response when AV conduction is intact 1, 2
• The presence of a regular rhythm excludes typical atrial fibrillation unless there is concurrent complete AV block or junctional rhythm 1
• AF shows fibrillatory waves that vary in amplitude, shape, and timing—not the organized saw-tooth pattern 1

Clinical Implications for This Older Male

The chest pain and heaviness require urgent attention:

• Hemodynamic instability from atrial flutter warrants immediate direct-current cardioversion 1
• The regular rhythm at approximately 150 bpm suggests 2:1 conduction, meaning the atrial rate is approximately 300 bpm 1
• In older patients, this rapid ventricular rate can cause myocardial ischemia even without underlying coronary disease, explaining the chest symptoms 1

Common Diagnostic Pitfall

Misdiagnosis can occur when atrial activity is prominent on ECG in multiple leads—atrial fibrillation may be mistakenly diagnosed as atrial flutter, but the key differentiator is the regular versus irregular ventricular response 1, 2. In this case, the regular rhythm and saw-tooth pattern definitively indicate atrial flutter.

Electrophysiological Mechanism

• Atrial flutter involves a single macro-reentrant circuit, most commonly around the tricuspid annulus in the right atrium 2
• The circuit typically conducts in a counter-clockwise direction, producing inverted flutter waves in leads II, III, and aVF with upright waves in V1 1
• This organized reentry creates the characteristic saw-tooth pattern without an isoelectric baseline between deflections 1

Relationship to Atrial Fibrillation

Clinicians should be aware that these arrhythmias frequently coexist:

• Atrial flutter may arise during antiarrhythmic treatment for AF 1, 2
• The ECG pattern can fluctuate between atrial flutter and AF in the same patient 1
• 80% of patients who undergo ablation of typical atrial flutter will develop AF within 5 years 2