Electrocardiogram

Chapter 3


Electrocardiogram





1. What are the most commonly used criteria to diagnose left ventricular hypertrophy (LVH)?



2. What are the most commonly used criteria to diagnose right ventricular hypertrophy (RVH)?



3. What criteria are used to diagnose left atrial enlargement (LAE)?



4. What electrocardiogram (ECG) finding suggests right atrial enlargement (RAE)?



5. What is the normal rate of a junctional rhythm?


    The normal rate is 40 to 60 beats/min. Rates of 61 to 100 beats/min are referred to as accelerated junctional rhythm, and rates of >100 beats/min or higher are referred to as junctional tachycardia.


6. How can one distinguish a junctional escape rhythm from a ventricular escape rhythm in a patient with complete heart block?


    Junctional escape rhythms usually occur at a rate of 40 to 60 beats/min and will usually be narrow complex (unless the patient has a baseline bundle branch block), whereas ventricular escape rhythms will usually occur at a rate of 30 to 40 beats/min and will be wide complex.


7. Describe the three types of heart block.



image First-degree heart block: The PR interval is a fixed duration of more than 0.20 seconds.


image Second-degree heart block: In Mobitz type I (Wenckebach) block, the PR interval increases until a P wave is nonconducted (Fig. 3-2). The cycle then resets and starts again. Mobitz type I second-degree heart block is sometimes due to increased vagal tone and is usually a relatively benign finding. In Mobitz type II block, the PR interval is fixed and occasional P waves are nonconducted. Mobitz type II second-degree heart block usually indicates structural disease in the atrioventricular (AV) node or His-Purkinje system and is an indication for pacemaker implantation.



image Third-degree heart block: All P waves are nonconducted, and there is either a junctional or ventricular escape rhythm. To call a rhythm third-degree or complete heart block, the atrial rate (as evidenced by the P waves) should be faster than the ventricular escape rate (the QRS complexes). Third-degree heart block is almost always an indication for a permanent pacemaker.


8. What are the causes of ST segment elevation?



image Acute myocardial infarction (MI) due to thrombotic occlusion of a coronary artery


image Prinzmetal angina (variant angina), in which there is vasospasm of a coronary artery


image Cocaine-induced MI, in which there is vasospasm of a coronary artery, with or without additional thrombotic occlusion


image Pericarditis, in which there is usually diffuse ST segment elevation


image Left ventricular aneurysm


image Left bundle branch block (LBBB)


image Left ventricular hypertrophy with repolarization abnormalities

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Jun 5, 2016 | Posted by in CARDIOLOGY | Comments Off on Electrocardiogram

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