278e: Atlas of Cardiac Arrhythmias

Respiratory sinus arrhythmia, a physiologic finding in a healthy young adult. The rate of the sinus pacemaker is relatively slow at the beginning of the strip during expiration, then accelerates during inspiration and slows again with expiration. Changes are due to cardiac vagal tone modulation with breathing.

Sinus tachycardia (110/min) with first-degree AV “block” (conduction delay) with PR interval = 0.28 s. The P wave is visible after the ST-T wave in V₁−V₃ and superimposed on the T wave in other leads. Atrial (nonsinus) tachycardias may produce a similar pattern, but the rate is usually faster.

Sinus rhythm (P wave rate about 60/min) with 2:1 AV (second-degree) block causing marked bradycardia (ventricular rate of about 30/min). LVH is also present, along with left atrial abnormality.

Sinus rhythm (P wave rate about 60/min) with 2:1 (second-degree) AV block yielding a ventricular (pulse) rate of about 30/min. Left atrial abnormality. RBBB with left anterior fascicular block. Possible inferior MI.

Marked junctional bradycardia (25 beats/min). Rate is regular with a flat baseline between narrow QRS complexes, without evident P waves. Patient was on atenolol, with possible underlying sick sinus syndrome. The serum potassium was slightly elevated at 5.5 mEq/L.

Sinus rhythm at a rate of 64/min (P wave rate) with third-degree (complete) AV block yielding an effective heart (pulse) rate of 40/min. The slow, narrow QRS complexes indicate an AV junctional escape pacemaker. Left atrial abnormality.

Sinus rhythm at a rate of 90/min with advanced second-degree AV block and possible transient complete heart block with Lyme carditis.

Multifocal atrial tachycardia with varying P-wave morphologies and P-P intervals; right atrial overload with peaked P waves in II, III, and ...