AV dissociation: no relationship between P waves and QRS complexes.≥ 2 consecutive impulses from the atria are not conducted to the ventricles.Permanent pacemaker placement for most patients.Management of reversible underlying conditions (e.g., inferior MI, cardiotoxic drug overdose, thyrotoxicosis).Hospital admission for temporary pacing.High risk of progression to a higher degree heart block or sudden cardiac arrest.Progressive lengthening of the PR interval until a beat is dropped, i.e., a normal P wave is not followed by a QRS complex.Consider an elective pacemaker for select patients.Asymptomatic patients require no treatment and can be followed-up as outpatients.Low risk of progression to a higher degree heart block or sudden cardiac arrest.Every P wave is followed by a normal QRS complex.Asymptomatic patients with first-degree and Mobitz type I blocks usually only require observation, whereas higher-degree blocks necessitate permanent pacemaker insertion. Depending on the heart rate, symptoms can be severe and include heart failure or syncope. AV blocks may be asymptomatic or cause symptoms of bradycardia. ![]() The complete absence of conduction results in a ventricular escape rhythm, whose rate depends on the level at which the escape rhythm is generated. A third-degree AV block, also known as complete heart block, involves the total interruption of the electrical impulse between the atria and ventricles. In second-degree high-grade AV block, two or more consecutive P waves do not generate a ventricular response. A 2:1 AV block has a regular pattern in which every second atrial impulse is not conducted to the ventricles. Mobitz type II blocks generate dropped QRS complexes at regular intervals (e.g., 3:2, 4:3, or 5:4), often leading to bradycardia. In Mobitz type I blocks, a progressive prolongation of the PR interval culminates in a nonconducted P wave (“dropped beat”). Second-degree AV blocks are further divided into four subtypes: Mobitz type I (also called Wenckebach), Mobitz type II, 2:1 AV block, and high-grade AV block. First-degree blocks are identifiable on ECG by a prolonged PR interval. There are three degrees of AV block, categorized according to the extent of the delay or interruption. If you aren't familiar with ECG interpretation, you find the Life in the Fastlane ECG Library helpful.īest wishes in learning ECG interpretation.Atrioventricular block (AV block) is characterized by an interrupted or delayed conduction between the atria and the ventricles. QT/QTc interval: Some centers will have you measure, and correct for rate, the QT interval. QRS complex: 0.06 - 0.1 seconds, although you will find some variation to these values. P wave: Are P waves present? Is each P wave followed by a QRS complex? Regularity: Is the rhythm regular? If irregular, Is there a pattern to the irregularity? Rate: What is the rate? Less than 60 or greater than 100? If an ectopic pacemaker site, is the rate less than or greater than the intrinsic rate for the pacemaker. When I analyze an ECG rhythm strip I use the following mnemonic: RRPPQQS. You need to learn the criteria for each of the rhythms you will be responsible to identify, and then apply those criteria, using a consistent, systematic approach, to each strip you are evaluating. ![]() ![]() This isn't something you can learn by trying to memorize what a particular rhythm looks like. Learning ECG interpretation is like learning heart or lung sounds. In the 3rd degree heart block, none of the P waves are conducted, and while there really isn't a true PR interval, the pseudo PR interval will vary from beat to beat. In theĢnd degree type 2 heart block (Mobitz II) you will find a consistent PR interval for the P waves that conduct, although the ratio of conducted-to-blocked impulses can vary. However, if you run a 12 - 15 second strip, this makes it much easier. These two can be difficult to differentiate, especially if you are looking at a short strip.
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