Electrocardiogram (EKG, ECG) interpretation⎢ekginterpretation.com

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Second degree AV block, mobitz I/wenckebach

Electrical conduction system of the heart

Waves, intervals and segments of the ECG

Corrected QT interval

July 4, 2010

The QT interval varies with the heart rate: the faster the heart rate, the shorter the QT interval. To adjust for the heart rate a corrected QT interval must be calculated. Often Bazett’s formula is used [...]

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Waves, intervals and segments of the ECG

June 24, 2010

In essence the electrocardiogram is a drawing of the hearts electrical activity. The waves and segments of the ECG are therefore best understood in connection with the electrical conduction system of the heart [...]

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Bifascicular heart block

June 22, 2010

Bifascicular heart block is the combination of right bundle branch block and block of either the left anterior fascicle or the left posterior fascicle (recall the electrical conduction system of the heart). The fascicle involved will often be the left anterior fascicle as the left posterior fascicle receives dual blood supply and is more resistant to myocardial ischemia [...]

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Atrial fibrillation

June 8, 2010

Atrial fibrillation is the most common arrhythmia of the heart. It is caused by multiple re-entrant circles in the myocardium of the two upper chambers. Instead of normal coordinated contractions, the atria fibrillate at a frequency of 350-600 beats per minute. On the ECG [...]

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Left atrial enlargement (abnormality), p mitrale

June 7, 2010

The normal p wave is often seen notched, which is likely caused by slightly asynchrony between depolarization of the right and left atrium. However in left atrial enlargement the notched, or bifid, p wave is often marked, in particular in lead II and lead V1, which is where to check for atrial abnormalities [...]

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Trifascicular heart block

June 6, 2010

Trifascicular block is seen on the ECG as a combination of a fascicular block (hemiblock), right bundle branch block (RBBB) and first degree av block. This ECG pattern results (but not always) from a combination of right bundle branch block and block of the two fascicles of the left bundle branch (hence the term trifascicular), however with one of these three blocks being incomplete [...]

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Fascicular blocks (hemiblocks)

May 30, 2010

Fascicular blocks are present when one of the fascicles of the left bundle branch are blocked. When a fascicle is blocked the overall electrical vector (gray arrows) of the heart is changed. And when the vector is changed it is reflected by axis deviation in the ECG. This is the key to ECG interpretation of fascicular blocks [...]

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Beat the bundle branch blocks

April 21, 2010

Though the ECG criteria differ, identifying the two types of bundle branch block can be done using a similar approach. Here are some points to consider:

1. The duration of the QRS complex is ≥ 0.12 seconds in both types of bundle branch block [...]

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Left bundle branch block, LBBB

April 20, 2010

As outlined in the article about the electrical conduction system of the heart the left bundle branch originates from the bundle of His and split into an anterior and a posterior fascicle. The concept of left bundle branch block (LBBB) can be illustrated using [...]

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Right bundle branch block, RBBB

April 18, 2010

Right bundle branch block (RBBB) is best seen in V1 as this lead is “looking” at the right side of the heart. Recall the electrical conduction system of the heart. Now what happens with the electrical conduction if the right bundle branch is blocked [...]

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