Week 3 - Advanced EKG Flashcards
3 key factors that determine left ventricular myocardial oxygen demands
HR, strength of contraction, systolic pressure developed in the main pumping chamber
What does a subendocardial infarct look like and what EKG changes would be present?
Inner part of LV, ST depression
What part of the heart does the RCA supply blood to?
Inferior/RV
What part of the heart does the left circumflex supply?
Lateral wall of the left ventricle
What part of the heart does the LAD supply?
Ventricular septum and a large part of the ventricular free wall
The acute phase of a STEMI is marked by the appearance of ST segment _________ and tall __________ T waves
Elevation, peaked
What are reciprocal ST depressions?
ST depressions in leads directed 180 degrees from those showing ST elevations.
What is the evolving phase characterized by in a STEMI?
Deep T wave inversions.
What part of the heart does an anterior infarct effect?
Anterior or lateral wall of the ventricle
Why does ST elevation occur in serve ischemia?
Alters the balance of electrical charges across the myocardial cell membranes.
What are the earliest signs of an infarct?
ST elevations (and reciprocal ST depressions). Generally seen within mins of blood flow occlusion
If a patient complains of persistent chest pain, and the EKG you have just drawn doesn’t show any indications of an MI, what should you do next?
Obtain EKGs in 5-10 minute intervals
A Q wave in any lead indicates that the electrical voltages are directed ________ from that particular lead
away
Why do Q waves, in the appropriate context, signify an MI?
They signify the loss of positive electrical currents, which is caused by the dead heart muscles.
What is a key feature in anterior wall Q wave infarcts?
The loss of the normal R wave progression. Anterior infarcts disrupt this process by causing pathologic Q waves in (V1-V5 or V6) one or more of the precordial leads.
In what direction is the ventricular septum depolarized?
right <— left
Anteroseptal infarct is characterized by?
ST elevation/pathologic Q waves in leads V1-V4
Loss of R waves in V1-V3. (Generally suggests the LAD is occluded)
In a high lateral infarct, what leads would you suspect to show pathologic Q waves?
Leads I and aVL
You may see tall R waves and ST depressions in leads V1-V2, suggesting
Posterior infarct.
(Generally leads V7-V9 are added on the patients back to visualize this area more clearly. You would see pathological q waves in these back leads, reciprocal to the tall r waves in leads V1-V2)
Inferior infarcts generally have ________ ventricular involvement
right
What may persistent ST segment elevations months - years after an MI indicate?
Ventricular aneurysm
Difference between septal q waves and pathologic Q waves
Septal q waves are narrow and of low amplitude (less than .04 seconds in duration)
Pathologic Q waves are longer than .04 secs in lead I, all inferior leads, or leads V3-V6
Non-infarction Q waves may be present in which two diseases?
Hypertrophic cardiomyopathy and dilated cardiomyopathy
What 3 things can come from a ventricular aneurysm?
May lead to chronic HF, can cause ventricular arrhythmias, and may serve as a substrate for clot formation.
In what BBB does the diagnosis of an MI become far more complicated?
LBBB (These blocks already present with features resembling an MI)
Most STEMI events are due to
Ruptured or eroded atherosclerotic plaque leading to ischemia and infarction.
In many cases, ST segment _________ is shown more frequently in myocardial ischemia (with or without infarction)
Depression
________ is a common symptom in coronary artery disease
Angina
3 things that can initiate angina
Physical exertion, emotional stressors, or exposure to cold
Many, but not all, EKG patterns of patients experiencing acute angina show _____ ______________
ST depression
Many patients experiencing transmural (epicardial) injury show ST segment ___________
Elevation
ST depression is classified as
Horizontal or downward ST depressions of at least 1mm in amplitude, lasting .08 seconds or more
The major EKG changes with non-Q wave infarctions are
ST depressions and/or T wave inversions
Prinzmetal’s variant angina is associated with ST __________
elevations
Why is angina harmful to the heart?
Spasms and constriction of the coronary arteries can cause non-infarct ischemia leading to eventual MI
Sometimes, ST elevation can be a benign variant caused by
Early repolarization –> These elevations DO NOT change and do not show reciprocal ST depression
Wellen’s syndrome is classified by
Deep T wave inversions, with minimal to no ST elevations.
Caused by a tight stenosis (blockade) in the LAD
T wave inversions in only the right chest leads or only the left chest leads may indicate?
Right leads –> RV overload
Left leads –> LV overload
3 examples of Mechanical/structural complications of the heart
HF, cardiogenic shock, LV aneurysm …
Electrical complications of the heart include
Any type of arrhythmia or block
Most effective method to achieve coronary reperfusion
Acute percutaneous coronary interventions via angioplasty/stenting. More efficacious than thrombolysis therapy.
Most common arrhythmia indicating coronary reperfusion
Accelerated idioventricular (AIVR)
Axis deviation for positive leads I, II, and aVF
NAD
Axis deviation for positive lead I, negative lead II
LAD
Axis deviation for positive lead aVF, negative lead I
RAD
Axis deviation for negative leads I and aVF
Extreme axis deviation
Which diseases would you see left axis deviation?
LAFB, LBB, LVH, V-pacing, inferior wall MI, WPW
In which individuals can LAD be a normal variant?
Obese patients
What do you expect to show on an EKG with a patient with a LBBB?
Terminal R waves in lateral leads (usually broad) –> V5, V6
Which ever way the R or S wave is, T wave is opposite.
Incomplete vs complete LBBB?
Complete –> QRS longer than .12
Incomplete –> QRS in between .10-.12, all other indications of LBBB
What do you expect to show on an EKG with a patient with a RBBB?
Terminal R waves in right leads (usually broad) –> V1, V2
Which ever way the R or S wave is, T wave is opposite.
What are the two hemiblocks?
LAFB –> Most common, left axis deviation
LPFB –> Rare, right axis deviation
What happens when you have a LAFB with a RBBB?
WIDE QRS. Only the Left Posterior branch is functioning! Grab a pacemaker!
Normal QTc
350-440 msec
Inferior RCA infarction involves the __________ __________
Nodal cells (SA node) Get pacer
Variants among patients
85-90% RCA
15-10% LCx
Reciprocal changes can be ____________ of an MI
confirmation
STEMI criteria
New _______ __________ at the J point (QRS endpoint) in two contiguous leads of > ________ mV in all leads except V2-V3
ST elevation, 0.1
STEMI criteria
For leads V2-V3: Greater or equal to ________ mV in men _______ or older
0.2 mV, 40
STEMI criteria
For leads V2-V3: Greater or equal to ________ mV in men or greater or equal to ________ mV in women younger than __________
0.25 mV, 0.15 mV, 40
ST depression is considered significant when ____ - ____ mm from the QRS
2-3 mm or 0.2 - 0.3 mV
The normal T wave is usually in the _______ _________ as the QRS
same direction
A normal ECG shows an upright t wave in leads ____, _____, and _____ - _____
I, II, V3 - V6
A normal ECG shows an inverted T wave in lead ______
aVR
The QT interval is dependent upon _______ ________
heart rate
What is Bazett’s formula?
Allows you to find QTc
QT / square root of (R - R interval)
What is the average direction of ventricular activation in the frontal plane referring to?
QRS axis determination
What 2 things can QRS axis determination tell us?
Changes in sequence of ventricular activation and myocardial damage
What degrees does a normal axis pathway fall into?
-30 to 90
What individuals can have RAD and it be considered a normal variant?
Marfans, tall, thin and small framed individuals
Which diseases will you see RAD in?
LPFB, lateral/anterior MI, RVH, PE, COPD, WPW, atrophy of LV
You will see poor R wave progression in V1-V3 in which block?
LBBB
Hemiblocks usually have normal QRS intervals, when would these complexes be more wide? (longer than 0.12 secs)
If there is a coexisting RBBB
LAD and branches supply blood to?
Anterior and anterolateral walls of the LV, and anterior 2/3 of the septum.
What does it mean if a patient is showing more and more leads experiencing ST elevation and pathologic Q waves?
The bigger the infarct and the poorer the prognosis
How would you define a pathologic Q waves?
Greater than .04 seconds and 25% or more of the amplitude of the R wave
