F - Physiological Basis of the ECG - Ballam Flashcards
Inferior leads
II, III, aVF
Septal leads
V1, V2
Anterior leads
V2, V3, V4
Lateral leads
I, aVF, V4, V5, V6
P wave
Inverted in aVR
Upright in 1,2,V4-6,aVF
What can alter QRS?
If not originated from or near AV node
Blockage of bundle
Cardiac ischemia or infarct
Hypertrophy - thick wall, dilated ventricle
QT interval is dependent on
Phase 2 plateaus of myocytes - calcium
What is the best representation of isoelectric point on ECG?
ST segment
Ischemia
Ischemic region will remain depolarized during phase 4
Electrode facing ischemic region will register a negative voltage during phase 4
Leads to an elevated ST segment
T wave
Dependent on normal depolarization sequence which is usually last to depolarize is first to repolarize
Supraventricular arrhythmia
Ventricular depolarization originating above ventricles
Triggers AP through the AV bundle (HIS) - QRS looks normal
Can be faster or slower than normal
Symptomatic Bradyarrhythmia
Sick sinus syndrome
SA nodal bradyarrhythmia
Can be normal in athletes, elderly, sleep
Due to SA nodal ischemia, cardiomyopathy, Beta and calcium blockers, hypothyroidism, hyperactive vagal input
Characterized by slower than normal phase 4 depolarization of SA node
Tachyarrhythmia
Sinus - originates in SA node Supraventricular - originates in atria or AV node -normal QRS Ventricular - originates in ventricular -wide or abnormal shaped QRS
Different types of tachyarrhythmia
Sinus tach
Atrial flutter
Atrial fibrillation
Paroxysmal SVT
