ECG and Dysrhythmias Flashcards
What is the P wave?
atrial depolarization (contraction)
What is the PR interval?
the time it takes from the start of atrial depolarization for an impulse to travel through the atrial tissue, AV node, bundle of His, bundle branches, and purkinje fibers (just before ventricular depolarization)
How long is the PR interval?
0.12-0.20 seconds or 3-5 small blocks
What is the QRS complex?
ventricular depolarization
How long is the QRS complex?
0.04-0.10 seconds or 1-2.5 small blocks
What is the ST segment?
early ventricular repolarization
How much ST segment displacement is significant?
elevation/depression by 1 mm or one small block up and down
What is the QT interval?
the total time for ventricular depolarization and repolarization
How long is the QT interval?
0.30-0.44 seconds or 7.5-11 small blocks
Causes of sinus bradycardia
vagal stimulation, valsalva (bearing down), carotid massage, vomiting, medications (BB, CCB, Digoxin)
Treatment of sinus bradycardia
atropine (only treat if pt is symptomatic), IV fluids, O2
Causes of sinus tachycardia
stress and dehydration
Pathophysiology of sinus tachycardia
increased CO & BP, increased myocardial O2 demand, decreased coronary artery perfusion time, decreased diastolic filling time
Treatment of sinus tachycardia
Treat the cause (doesn’t always require treatment bc stress can cause it), valsalva, carotid massage, medications (BB, CCB, Digoxin)
Atrial tissue becomes irritable and fires an impulse before the next sinus impulse is due
Premature atrial contraction
Rapid stimulation of atrial tissue
Rate: 150-250 bpm
Clinical Manifestations: palpitations, chest pain, SOB, anxiety, hypotension
Supraventricular Tachycardia (SVT)