12 Lead ECG interpretation Flashcards
Name the Limb leads
I, II, III, AVR, AVL and AVF
Name the chest leads
V1, V2, V3, V4, V5
Which lead uses the left foot?
AVF lead uses the left foot as the positive electrode and combines the left and right arm electrodes into a negative charge
what are the inferior leads?
Lead II, III and AVF
What are the lateral leads?
Lead I and AVL
What is a bundle branch block?
caused by a block in the pulse in either left or right bundle branches. Causes a widened QRS of at least 0.12 seconds or more.
Characteristic of RBBB
Produces the R and R prime in the right chest leads (V1 or V2) R prime represents the delayed depolarization of the blocked ventricle Look for the bunny ears
Characteristic of LBBB
check for R and R prime in the left chest leads (v5 and V6) LBBB is caused by a delay in the depolarization of the left bundle
what is axis?
refers to the direction of the movement of depolarization which spreads throughout the heart to stimulate the myocardium to contract.
What is a mean QRS vector?
mean QRS vector is the sum of the smaller vectors of ventricular depolarization . since the left ventricle is thicker and stronger, then the mean QRS vector deflects toward the left ventricle. Points down and towards the left which means general direction of ventricular depolarization
Lead one for axis deviation
Split in right and left half.
Right half is negative
left half is positive.
if the qrs is positive in lead 1, then the QRS is pointing positively in the left direction. If QRS is negative, then there is right axis deviation
Lead AVF for axis deviation
Split in lower and upper half.
upper half = negative
Lower half = positive
if QRS is positive, then the mean QRS vector is pointing downward
if the QRS is negative then it is axis deviation
Lead II for axis deviation
Divides the circle at an angle.
Lower left = positive
Upper right = negative
if the mean QRS is positive, then the mean QRS vector points down to the left (normal)
if the QRS is negative, then the mean QRS vector points up to the right (right axis deviation)
What is hypertrophy?
increased thickness of muscle
hypertrophy of a chamber of the heart means that the muscular wall of that chamber has dilated and thickened beyond normal thickness
usually causes some degree of dilation and therefore may increase the volume that the chamber can hold
What is atrial enlargement?
Atria is enlarged. P wave is diphasic( both positive and negative deflections)
Right atrial enlargement - the biphasic wave is larger
left atrial enlargement - the terminal portion of the biphasic wave is larger
What is left ventricular hypertrophy?
When LVH is present, causes great QRS deflections in the chest lead. with LVH there is more depolarization going down and to the left the heart, causing very deep S wave in V1 and a large R wave in V5
What is right ventricular hypertrophy?
Large R wave in V1. Since the wall of the right ventricle is thick, there is more depolarization or positive pull towards V1 than normal
what is an infarction?
the myocardium’s blood supply is provided exclusively by the coronary arteries. Plaque buildup in the lining of the arteries can cause part of that lining to rupture, exposing the plaque to the blood within the coronary artery. That causes the formation of a clot (thrombus) leading to immediate tissue necrosis of that part of the myocardium
Where is the infarcted tissue primarily?
Primarily in the left ventricle.
What is the myocardial infarction triad?
Ischemia -reduced blood flow
Injury - recent or acute
infarction -necrosis or dead tissue
what is ischemia?
Characterized by inverted T waves, cardiac ischemia can cause angina (chest pain). T wave inversion in leads v2 -v6 is considered pathological
what is injury?
indicates the acuteness of an infarct
ST segment depression can occur under certain conditions (angina, stress, digitalis)
ST segment elevation detonates injury. ST elevation alone can indicate infarction, the ST segment may only be elevated slightly
what is an infarction?
Q waves indicate necrosis . Q wave is 1 mm wide or 1/3 oft the entire QRS amplitude.
Q wave + ST segment elevation = acute MI
what is an anterior infarction?
caused by an occlusion of the anterior descending branch of the left coronary artery.
Q waves in leads V1, V2, V3, V4 signify an anterior infarction
