The electrocardiograms in this Atlas supplement those illustrated in Chaps. 232 and 233. The interpretations emphasize findings of specific teaching value.
All of the figures are adapted from cases in ECG Wave-Maven, Copyright 2003, Beth Israel Deaconess Medical Center, http://ecg.bidmc.harvard.edu.
The abbreviations used in this chapter are as follows:
AVRT—atrioventricular reentrant tachycardia
LBBB—left bundle branch block
LVH—left ventricular hypertrophy
RBBB—right bundle branch block
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 (non-sinus) 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.
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.
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 A-V 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.