Flashcards in EKG Deck (58):
Where is the SA node ?
wall of RA below entrance of SVC
Where is the AV node ?
inferiorly in the right atrium above the tricuspid valve
edge of coronary sinus
What are ventricular rhythms? What is the rate (normally, accelerated, tachycardia)? What is the change seen on EKG?
if conduction starts in Purkinje cells (ventricles)
20-40bpm - ventricular escape rhythm
>40 - accelerated ventricular rhythm
>100 - ventricular tachycardia
P waves absent (no atrial rate)
PR interval absent
Current flowing towards the positive/negative electrode will cause an upward/downward deflection.
Current flowing towards the positive electrode will cause an upward deflection. Current flowing towards the negative electrode will cause a downward deflection.
Describe the placement of the precordial leads.
V1 - 4th ICS, 2cm to the right of the sternum
V2 - 4th ICS, 2 cm to the left of the sternum
V3 - midway between V2 and V4
V4 - 5th ICS, midclavicular line
V5 - 5th ICS, left anterior axillary line
V6 - 5th ICS, left midaxillary line
Why does the epicardium repolarize first? (earlier than the endocardium)
shorter refractory period
Which electrode is used for grounding and can be placed anywhere?
"right leg" electrode
Where is the positive lead in aVR and what view of the heart does it give you?
view of heart from right arm
Where is the positive lead in aVF and what view of the heart does it give you?
view of heart from foot
Where is the positive lead in aVL and what view of the heart does it give you?
view of heart from left arm
Describe lead placement for bipolar leads.
Lead I connects right arm to left arm*
Lead II connects right arm to left leg*
Lead III connects Left arm to left leg*
True or False: The more parallel the electrical force is to the lead, the greater the magnitude of the deflection.
An electrical force directed perpendicular to an electrocardiographic lead registers what kind of activity?
None ! A flat line on the recording
What view of the heat do each of the precordial leads measure.
V1 and V2 - right side of heart
V3 - septum and apex
V4-V6 - left heart
How do the R waves and S wave change as you move from V1 through to V6?
R waves get taller
S waves get less deep
What is the first part of the ventricle to be excited? What happens to the direction of electrical current as depolarization proceeds throughout the heart?
left side of interventricular septum
depolarization proceeds from there to right ventricle --> apex --> lateral walls
direction of electrical current swings left
What does the PR interval measure? What is normal duration for PR interval? What could cause a longer PR interval?
atrial depolarization + conduction through V node
greater than 0.20 s - first degree AV block
What does QRS complex measure? What is the normal duration for the QRS complex?
less than 0.10 seconds
What does the QT interval measure? What is the normal length of QT interval?
duration of which the ventricles stay depolarized + time it takes for ventricles to repolarize
= 0.44 s
What does the P wave represent?
early part of P wave - RA activation
late part of P wave - LA activation
In what lead are P wave upright? inverted?
upright in I, II and V1
inverted in aVR
Each small horizontal box on the ECG represents ___ s and each vertical box on the ECG represents ___ mV
0.04 s (5 small squares = 0.2 seconds)
0.1 mV (5 small squares = 0.5 mV)
How is the QT interval affected by heart rate? How do we correct for this when measuring the QT interval?
the faster the heart beats, the faster the ventricles repolarize so the shorter the QT interval
QTc = QT/square root of RR interval
A prolonged QT could lead to a type of ventricular tachycardia called? What are some causes of long QT?
Torsades de Pointes
drugs, lyte abnormalities, CNS disease, post-MI, CHD
Whats normal axis ? What is left axis deviation and right axis deviation? How can we check for this on ECG?
between -30 degrees and +90 degrees
below -30 degrees --> left axis deviation
greater than +90 degrees --> right axis deviation
if QRS complex is mostly upright in Lead I and Lead II, then the axis is normal
if it is + in Lead I and - in Lead II, left axis deviation
if it is - in lead I and + in Lead II, right axis deviation
What axis deviation would you expect with an infarct of the right ventricular wall? What axis deviation would you expect with right ventricular hypertrophy?
infarct in right wall --> left axis deviation
RVH --> right axis deviation
When are Q waves pathologic? What do pathologic Q waves indicate?
if they are wider, deeper, and present in V1-V3
usually indicative of myocardial infarction
Describe ECG changes in STEMI
ST elevation (injury)
pathologic Q waves (infarction)
T wave inversion (ischemia)
True or False: Tachyarrythmias are not uncommon after myocardial ischemia or myocardial infarction.
What are ECG changes seen with accessory pathway?
What is a U wave? What electrolyte disturbance is it associated with?
late phases of repolarization of ventricles (repolarization of Purkinje fibres)
associated with hypokalemia
What parts of the ECG represent absolute and relative refractory periods?
ST segement and first part of T wave is absolute refractory period
latter part of T wave is relative refractory period
What is "R on T' phenomenon and when does it occur?
when a PVC arises during the relative refractory period (falls on T wave)
it is extremely dangerous and may lead to ventricular arrhythmias
Which leads are inferior and what coronary artery do they give information about?
II, III, aVF
Which leads are anterior and what coronary arterie(s) do they give information about?
V1 & V2 - LAD
V3 & v4 - RCA
Which leads are lateral and what coronary artery do they give information about?
I, aVL, V5, V6
What are EKG findings in SVT?
P waves may be notched or flattened (if present)
may be hidden in previous T wave or QRS complex
PR interval <0.20 seconds
QRS complexes narrow
What are EKG findings in AF?
irregularly irregular rhythm
no PR interval
QRS complexes narrow
What are EKG findings in AFL?
atrial rate: 250-350 bpm
rhythm regular if ratio of atrial beats conducted is constant, otherwise rhythm is irregular if the ratio is variable
P waves appear "saw toothed" and there are more P waves than QRS complexes
PR interval <0.12 seconds
What do PVCs look like on EKG? What is bigeminy, trigeminy, couplet and V tach? What does it mean to say they are monomorphic vs polymorphic?
irregular rhythm, NO atrial depolarization
bigeminy - every second beat is a PVC
trigeminy - every third beat is a PVC
couplet - two PVCs occuring together
V tach - three or more PVCs together
unifocal: each PVC looks the same, comes from the same ectopic focus
multifocal: each PVC looks difference, coming from multiple ectopic foci
What are EKG findings in AT? What is different about paroxysmal AT?
rhythm usually regular unless there is more than one irritable foci in the atrium - then irregular
P wave usually hidden in the T wave of the preceding complex
if P waves present they are not normal configuration (can be flattened or notched)
normal PR interval
narrow QRS complex
paroxysmal: P waves not discernible, PR interval not measurable, usually preceded by frequent PACs
What do PJCs look like on EKG?
P waves not seen buried in QRS complex
or P wave inverted and may occur before or after QRS complex
if P wave is before QRS, PR interval is <0.12 seconds
narrow complex QRS
What are examples of partial conduction blocks? Or complete heart block?
partial blocks: first degree AV block, second degree AV block type I (Mobitz I or Wenckebach), second degree AV block type II (Mobitz II)
complete block: third degree heart block
What is seen on EKG with the different types of heart block?
long PR interval: first degree
second degree Type 1 (Wenkebach) - PR intervals get progressively longer then drop
second degree Type 2 (Mobitz II) - PR is constant, but some P waves are not conducted
third degree - atria and ventricles are contracting at their own rate - no relationship between P waves and QRS - ventricular rate is ~1/2 of atrial rate
What are some reasons that may explain lower voltages on EKG?
What are some reasons why there may be more P waves than QRS complexes?
AV block type II or III
What are some reasons there may be more QRS complexes than P waves?
ST elevation usually indicates ___ while ST depression indicates ___
ST elevation --> STEMI (if in a few leads, concave down, "tombstone") or pericarditis (if diffuse, concave up, "smiling")
ST depression --> ischemia/infarction, strain
What does an 'm' shaped P wave represent?
In what electrolyte disturbance would you see peaked T waves?
Describe changes you would see with RBBB and LBBB.
LBBB - changes in V4-V6
RBBB - changes in V1
What ECG findings would occur in RVH?
R wave > S wave in V1
In what condition would you see electrical alterans (height of QRS keeps changing)?
What happens in AVNRT/AVRT when you give adenosine (EKG)?
adenosine blocks AV node
tachycardia terminated with adenosine means tachycardia is dependent on AV Node
What ST changes would you expect in a NSTEMI?
True or False: ST elevation during acute STEMI is associated with simultaneous ST depression in the electrically opposite leads
What is a junctional rhythm? What are the changes seen on EKG? What is accelerated junctional rhythm/tachy/brady?
when impulses arrive from Bundle of His + AV node (junction)
abnormal P waves: inverted, before during or after QRS or may not be present at all, PR interval 60bpm - accelerated junctional rhythm
>100bpm - junctional tachycardia
<40bpm - junctional bradycardia