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What happened in 1901?

Einthoven built first 3 lead EKG machine.


What happened between 1934-1938?

Wilson invented the precordial (chest) leads.


What happened in 1942?

Goldberg invents augmented unipolar leads.


What happened in 1954?

AHA standardized 12-lead EKG as we know it now.


How much time does each box on EKG graph paper represent?

0.04 s or 40 ms.


How much time do 5 EKG boxes represent?

0.2 s or 200 ms.


How does conductance occur?

Depolarization begins in the SA node in the right atrium and sends electrical current through both the right atrium and over to the left atrium (via Bachman's bundle), causing atrial contraction. This current then passes to the AV node, which slows the current to allow the ventricles to fill completely with blood. The current continues down the bundle of his to the left and right bundle branches, which travel down the septum together until they reach the apex of the heart where they continue to left and right sides respectively as finer fibers called purkinje fibers. These depolarize the myocytes of the ventricles simultaneously for ventricular contraction.


Does the EKG tell you anything about mechanical activity?

NO. You have to feel for pulses for mechanical activity.


To what does the cardiac electrical activity lead?

pressure changes that lead to blood flow.


Do the SA node, AV node, bundle of His, purkinje fibers, and ventricles all have different APs?

YES. The EKG summates these. Thus each region of the heart has specific electrical properties.


By controlling Na+ channels, what can we manipulate?

heart rate


By controlling Ca+ channels, what can we manipulate?



Do cardiac myocytes have a lot of mitochondria?

YES, because they require a lot of ATP.


Can you have electrical events uncoupled from mechanical events?

YES. Aka a normal EKG with no cardiac mechanical activity :(


What does the EKG tell us?

ionic fluxes, atrial/ventricular electrical activity, the intervals tell us about appropriate actions over time


How long should the PR interval be?

5 boxes (0.2 s) or less.


How long should the QRS interval be?

no more than 3 boxes (0.12 s).


What if the QRS interval is longer than it should be?

there is an interventricular conduction delay (>3boxes or 0.12 s). possibly due to ischemia or infarction.


Should the ST segment be isoelectric?

YES, in line with the PR interval.


How long should the T wave be?

5 boxes (0.2 s).


How many views of the myocardium does the EKG show us?



What do the EKG electrodes that are placed on the patient pick up?

mV changes with respect to time


What are the 12 leads on an EKG?

I, II, III, avR, avL, avF, V1, V2, V3, V4, V5, V6


What is Einthoven's triangle?

consists of 3 leads forming a triangle from the patient's shoulders to their left foot.


In what direction does lead I go?

from right shoulder (-) to left shoulder (+). These 2 charges are a dipole, and the electrodes receive + or - charges and interpret it as coming either toward or away from it.


When a lead is looking at electrical impulses, what type of deflection does a wave of DEpolarization moving TOWARD a POSITIVE electrode cause?

positive deflection (up)


When a lead is looking at electrical impulses, what type of deflection does a wave of DEpolarization moving AWAY from a POSITIVE electrode cause?

negative deflection (down)


When a lead is looking at electrical impulses, what type of deflection does a wave of REpolarization moving TOWARD a POSITIVE electrode cause?

negative deflection (down)


When a lead is looking at electrical impulses, what type of deflection does a wave of REpolarization moving AWAY from a POSITIVE electrode cause?

positive deflection (up)


How do we interpret EKG waveforms?

by looking at the polarity and amplitude of the leads.


What is avR?

augmented lead right


What is the placement of lead I?

right arm to left arm


What is the placement of lead II?

right arm to left foot


What is the placement of lead III?

left arm to left foot


What are the augmented voltage leads?

avR, avL, avF


What are the precordial (chest) leads?

V1 (right 4th intercostal space), V2 (left 4th intercostal space), V3 (5th rib between 2 and 4), V4 (5th intercostal space at midclavicular line), V5 (between 4 and 6), V6 (midaxillary line, lateral to V4 and V5).


What is the color and placement of the EKG electrodes?

white (right shoulder), black (left shoulder), green (right lower extremity), red (left lower extremity), and precordial leads (V1-6) are brown.


What should the paper speed be on the EKG machine?

25 mm/s.


What exactly comprises a "lead"?

a + and - electrode, and the two electrodes put together (dipole) constitute the lead.


Into what do the 12 leads feed?

into a transducer that produces the squiggly lines with respect to time on the EKG paper.


What is a biphasic signal?

a polarized wave that is perpendicular from a positive electrode (isoelectric).


What does a large dominant Q wave indicate?

that we have an infarction somewhere.


How can we determine HR from an EKG?

Use R to R peaks by finding one that aligns closely with a bolded line and count bolded lines until the next R peak, where each bolded line from the first is (300, 150, 100, 75, 60, 50).


Does the amplitude on the EKG increase with left ventricular hypertrophy?



During what phase do the coronary arteries receive blood flow?

during diastole.


What happens if there is too much Ca++?

It will crunch the PQRST together.


What happens if there is low Ca++?

It will spread the PQRST.


What all can we interpret from the EKG?

rate, rhythm, axis, hypertrophy, ischemia, MI, hyper- or hypokalemia, hyper- or hypocalcemia, atrioventricular blocks, atrioventricular conduction delays, 2nd and 3rd degree bundle blocks, right and left bundle blocks


What are the 2 types of irregularity?

regular irregularity and irregular irregularity.


What is superventricular tachycardia?

tachycardia (>100 BPM) above the ventricles (aka the atria).


How do you determine axis from EKG?

look for upright or downward deflections in each lead.


What is Wenkebach?

PR interval gets longer and longer and then drops (disappears).


What should the ST segment be?

isoelectric with the PR interval.


What could happen if the QT interval gets longer?

it could create a dysrhythmia because during the relative refractory period of repolarization, another beat could be produced.


How do you know if the QT interval is prolonged?

if the QT interval is longer than half the distance from R to R. :(


Of what are "U" waves indicative?



What is the intrinsic rate of the SA node?

60-100 bpm


What is the intrinsic rate of the AV node?

40-60 bpm


What is the intrinsic rate of the ventricular muscle?

20-40 bpm


What exactly the augmented leads (aVR, aVL, aVF)?

Not physical electrodes, but rather mathematical formulations [ex. aVR= (- lead I + lead II)/2]


How do you determine if the axis is normal?

if it's + (upward) deflection in lead I and + (upward) in aVF it's normal (0-90 degrees).


How long is an EKG?

10 sec


How would you determine a left axis deviation (0 to -30)?

+ (upward) deflection in lead I, - (downward) in aVF, and + (upward) in Lead II.


How would you determine a right axis deviation (>100)?

if it's - (downward) deflection in lead I and + (upward) in aVF.


What does isoelectric mean?

the QRS has the same amount of positivity as negativity.


How do you use the isoelectric lead to figure out axis?

Whatever lead the QRS has the same amount of positivity as negativity, will tell you the axis for which "perpendicular angle" would be to that lead (ex. lead I= +90 degrees or lead II= -30 degrees).


What happens during the QT interval?

depolarization and repolarization of the ventricles.


What are the NORMAL ranges for corrected QT (QTc) intervals?

1-15 years= 0.44 s, Men=


What are the PROLONGED ranges for corrected QT (QTc) intervals?

1-15 years= >0.46 s, Men= >0.45 s, Women= >0.47 s


How do we use the EKG to look at left ventricular hypertrophy (LVH)? "Cornell Criteria"

Men= S wave in V3 + R wave in aVL > 24 mm
Women= S wave in V3 + R wave in aVL >20 mm


What are some EKG clues to right ventricular hypertrophy (RVH)?

Right axis deviation (>90 degrees), tall R waves in V1 and V2 (because these leads look at the right ventricle). Right atrial enlargement is also indicative.


What is indicative of left atrial enlargement?

P wave duration >0.12 s (>3 boxes) in Lead II, and terminal P negativity in V1 (end of P wave is wide and deep).


What is indicative of right atrial enlargement?

Very tall P waves in lead II.


What is the definition of sinus rhythm?

upright P waves in lead II.


Are biphasic (isoelectric) P waves in V1 normal?



What 4 questions must you ask yourself regarding rhythm analysis?

1. What is the heart rate?
2. Is the Rhythm regular or irregular?
3. Are there P waves?
4. Is the QRS normal or prolonged (> 3 boxes)?


What is a premature atrial complex (PAC)?

rhythm coming before it should in the atria (looks like a second P wave).


What is a premature junctional complex (PJC)?

rhythm coming before it should in the AV node (no P wave). Don't see these often.


What is the most common arrhythmia in the elderly?

atrial fibrillation (AFIB)


What is AFIB?

Disorganized atrial depolarization (irregularly irregular) with no visible P waves. There is presence of small, irregular fibrillatory oscillations in the atria.


Will ventricular rate be fast or slow in AFIB?

could be both.


What should you think if the ventricular rhythm is regular in AFIB?

high grade AV block (junctional escape rhythm) or Digoxin toxicity.


What is the clinical significance of AFIB?

It causes decreased blood flow in atrium, leading to thrombus (in left atrial appendage), embolic stroke, or ischemic event.


What is atrial flutter (AFLUTTER)?

The more organized cousin of AFIB (has same stroke risk). It has a rapid, regular, atrial rhythm (200-400 bpm), with sawtooth-like oscillations.


Is a typical AFLUTTER clockwise or counterclockwise?

counterclockwise hoop of electrical energy around the right atrium


What heart rate is classically AFLUTTER?

150 because even though it's 300, every other gets through.


How do you know if you're looking at atrial tachycardia (ATACH)?

inverted P wave in lead II that is fast


What is multifocal atrial tachycardia (MAT)?

Rate > 100 bmp wtih 3 morphologically distinct P waves. Commonly seen in people with COPD.


What is AV node reentrant tachycardia (AVNRT)?

unlike AFLUTTER, you can't see the P waves, will be fast, narrow QRS complex, regular, and people feel lousy.


What is Wolf-Parkinson-White syndrome?

the electrical signal has another way to get from the atria to the ventricles (due to a piece of remnant embryonic tissue).


What are the two paths of the AV node?

fast pathway (has long refractory period) and Slow pathway (has Short refractory period). aka there is an inverse relationship


Why can't the electrical signal (depolarization) go back up the AV node?

because it travels down the fast pathway first, but the slow pathway descension blocks it as it attempts to go back up.


What happens to AV node conduction in AVNRT?

A PAC can encounter a refractory fast pathway, pushing it down the slow pathway. By the time the impulse travels back up the fast pathway, it is now fully repolarized, and can make it back up. :(


What is first degree heart block?

PR interval is > 0.2 ms (greater than 5 boxes). Not terribly concerning. If QRS is narrow, then AV node block.


What are the 2 types of second degree heart block?

Mobitz Type I (Wenckebach)= progressive lengthening of PR interval until P wave is not conducted along with no QRS. Then it resets. Atrial rate is regular. R to R also shortens.
Mobitz Type II= PR interval is fixed (doesn't change) for 2 cycles followed by dropped QRS.


What is third degree heart block?

No communication between atria and ventricles. Aka nothing is making it from the top chamber to the bottom one. Perfusing rhythm is maintained by a junctional or ventricular escape rhythm.


Can Wenckeback (second degree heart block) occur normally during sleep?



Is second degree Mobitz Type II heart block indicative for a pacemaker?



In heart block, what does a wider QRS indicate?

the lower in the heart it is (AV node or bundle of his or below bundle of his bifurcation).


Do you usually have sinus rhythm with third degree heart block?

YES because the sinus node (SA node) is firing normally. It just can't send the signal to the ventricles. So you will see two independent rates for atria and ventricles.


What are the two parts to the left bundle branch?

left anterior fascicle and left posterior fascicle.


Does the right bundle branch also have two parts?

NO, just one.


What happens in a right bundle branch block (RBBB)?

The left side of the heart depolarizes first, followed by a secondary R wave (R’) in the right precordial leads (V1-2). Looks like "rabbit ears." Also a wide, slurred S wave in the lateral leads.


Can you still diagnose MI with RBBB?



What patients in particular is RBBB seen?

COPD patients or those with a PE. Can also be seen in normal patients.


What is a trick to find a RBBB?

turn the EKG clockwise 90 degrees and if V1 is pointing to the right, you have a RBBB.


Does the same criteria apply for LBBB?

YES. QRS is wider than 3 boxes and the normal direction of septal depolarization is reversed (becomes right to left), as the impulse spreads first to the RV via the right bundle branch and then to the LV via the septum. You will see tall R waves "rabbit ears" in the lateral leads (V5-6) and deep S waves in the right precordial leads (V1-2). QRS in V1-2 will also be away from it (downward deflection).


Does LBBB usually lead to left or right axis deviation?

left axis deviation


What is a Left anterior fascicular block (LAFB)?

QRS less than 0.12 s (120 ms)
qR pattern (small q, tall R) in leads I and aVL
left axis deviation