Heart Blocks

What is the treatment for a 3rd degree heart block?

Pacemaker -External -Temporary (transvenous) -Permanent

What are three signs/symptoms in which heart blocks may be suspected?

-Abnormally low heart rate -Syncope -Hypotension

What are common causes of bundle branch blocks?

-Degeneration of conduction fibers due to age, HTN, etc -Insufficient blood flow -Focal diseases, such as lyme disease and aortic stenosis

What are the various causes of a 1st degree heart block?

-Enhanced Vagal Tone (athletes) -Myocarditis -Beta blockers, CCB, Digoxin -Electrolyte Disturbances -Myocardial Infarctions

What is the ECG criteria for a LBBB?

-Wide QRS Complex -ST depression -Tall, broad R waves (but, biphasic R wave in V1 means that this is not a LBBB, but a RBBB). -Or inverted T waves -All in leads I, aVL, V5, and V6

What are the significant EKG findings of a RBBB?

-Wide QRS complexes -Notched R wave (R-R') in Lead V1 (and/or V2) in which second R wave is usually larger than the first, but not always -Downward Sloping S wave in Lead I (and V6 according to sources)

Rate: 75 bpm Rhythm: Regular P waves: Present and upright PR: 0.28, fixed QRS ratio: 1:1 QRS: NL

1st degree heart block Only change: PR interval >0.20 seconds

Rate: 75 bpm Rhythm: Irregular P: Present and upright PR Interval: Lengthens with each subsequent beat, then QRS complex drops, and PR interval is reset and lengthens again QRS ratio: 5:4 QRS: NL

2nd Degree AV Block Type 1 (Wenckebach, Mobitz I) -Progressive lengthening of PR interval represents decrease in conduction at the AV node until it fails (dropped QRS) and then recovers. Usually transient can occur during: -Acute MI -During Sleep -Parasympathetic stimulation medications -Doesn't require treatment, unless bradycardia develops/

Rate: 55 bpm Rhythm: Regularly Irregular (fixed block ratio) P waves: Present and upright PR interval: Fixed and NL QRS Ratio: 4:3 QRS: NL

2nd Degree AV Block Type II (Mobitz II) -Presence of normal P waves with normal PR intervals, followed by 1 or more lonely P waves, and then normal P:QRS complexes follows. -Dropped QRS may or may not follow a certain pattern (NNDNNDNND) or (NNDNNNDDN) -Often serious because the heart is not conducting properly= decrease in cardiac output. -Can lead to a complete/3rd degree block!

Atrial Rate: 90 bpm Ventricular Rate: 40 bpm Rhythm: Regular P waves: Present and upright PR interval: Variations QRS ratio: Variations QRS: Wide

3rd Degree AV Block (Ventricular Escape) -Ventricular Rate is 20-40 bpm -There is no connection between the ventricles and atria. Both conduct at their own pace. -Lethal arrhythmia, usually from complication from infarction

What is the conduction deficit in a 1st degree heart block?

Delay in the AV node -Leads to prolonged PR interval > .20 seconds -Not often symptomatic and not likely to progress to more serious heart blocks.

3rd Degree Heart Block in which the QRS complexes are narrow

Junctional Escape 3rd Degree AV Block Rate is between 40-60 bpm

Out of the two types of bundle branch blocks, which is the most concerning?

Left Bundle Branch Block -This is because it supplies the L ventricle. -R bundle branch blocks are usually asymptomatic and not as concerning

If a patient presents with acute chest pain and SOB and has a LBBB, what should be suspected until proven otherwise?

MI of the Left Anterior Descending Artery

What is the morphology of an R wave in a R bundle branch block?

Notched or two R waves R and R' -Caused by asynchrony of ventricular contraction. Is also what leads to wide QRS complex

What is the size of a QRS in which a bundle branch block would be suspected?

Usually wide QRS without tachycardia or bradycardia -But, there can be SVT with BBB, which looks like ventricular tachycardia