Cardio Fun Facts Flashcards
things I just need to memorize
A consistent upright P wave in lead II tells you what?
Activation of the atria is right to left and superior to inferior (aka normal)
What does a P wave amplitude > 2.5 mm represent?
Right atrial enlargement
What does wide, biphasic P waves in V1 or wide, notched P waves in II and III correlate with?
LA enlargement or LA pressure overload
What is the PR interval? What does it measure?
Starts at the beginning of the p wave and ends at the beginning of the QRS
It measures the time the electrical stimulus takes to travel from the atria to the ventricles
Also called the AV interval
What is a normal PR interval?
< 200 ms (aka one big box)
What does a prolonged PR interval suggest?
Delay in the AV node (primary AV block according to Boards) or the His-purkinje system
What two major structures decide the PR interval?
AV node and His-purkinje system
What does QRS represent?
Time and direction of ventricular deplarizaion
What is a normal QRS range?
< 100 msec
What is considered a mild QRS delay?
100 - 120 msec
What is considered an abnormal QRS delay? What is this most often called?
> 120 msec
Bundle branch block
What does the T wave represent?
Ventricular repolarization
What does the ST interval give us insight into?
Ischemia and injury
What is the QT interval?
Measured from the start of the QRS to the end of the T wave
Reflects both depolarization and repolarization time
What QT interval is normal for men?
< 450 msec
What QT interval is normal for women?
< 470 msec
What QT interval range is considered “significantly prolonged”?
Over 500 msec
Why does QT have to be corrected?
Because its rate dependent
What is the formula for QTc?
QTc = QT interval in msec / square root of the R to R interval in seconds
Note: At 60 bpm the QT interval = QTc
What will QTc do to HR lower than 60? Greater than 60?
Lower than 60: correct shorter
Greater than 60: correct longer
The axis on a 12 lead ECG refers to what?
QRS axis since the ventricles overwhelmingly dictate the summed vector due to their mass
What leads are used to determine axis?
Only the limb leads (because its done in the frontal plane)
What is considered normal axis?
-30 to +110 or so, varies by author and lecturer
What are the important leads for determining the QRS axis?
I, II, and aVF
What do leads I, II, and aVF show in left axis deviation?
I (+)
II, aVF (-)
What do leads I, II, and aVF show in right axis deviation?
I (-)
II, aVF (+)
What do leads I, II, and aVF show in extreme axis deviation?
I, II, aVF (-)
Changes in the direction of the QRS axis can suggest what?
Myocardial thickening, myocardial enlargement, delay in conduction
How is hypertrophy measured?
QRS amplitude
Prominent voltage for R wave in lead v1 suggests what?
right ventricular hypertrophy
Prominent voltage (large R or S waves) in the precordial leads suggests what?
Left ventricular hypertrophy
Prominent voltage for R wave in the aVL lead suggest what?
left ventricular hypertrophy
What is the “strain pattern”?
Repolarization abnormality often seen with left ventricular hypoertrophy
What is the Cornell criteria for LVH voltage?
Voltage of S wave in V3 (negative direction) + voltage of R wave in aVL (positive direction) added together
What is LVH in men according to Cornell criteria? In women?
Men: > 24 mm (2.4 mV)
Women: > 20 mm (2.0 mV)
Higher QRS amplitude or voltage combined with changes in the QRS axis suggest what?
thickening or enlargement of the myocardium
How can you identify a left atrial abnormality on an EKG?
P wave duration > 120 msec in lead II
P wave notching
Bi-phasic/Negative p wave in V1 at least one small box wide and deep (1mm )
How can you identify a right atrial abnormality on an EKG?
P wave amplitude in lead II > 2.5 mm
What QRS duration is indicative of a left or right bundle branch block?
Prolonged > 120 msec (incomplete is 100 to 120)
How can you identify a left bundle branch block on an ECG (three things)?
- rS or QS complex (no R wave) in the right precordial leads V1 and V2
- Secondary ST and T wave changes opposite in direction to the major QRS deflection (look for T wave inversion in I, V5, V6 with ST elevation and upright T wave in V1 and V2)
- Broad, monophasic R waves in leads I, V5, and V6
Left bundle branch block is seen in what pathologies?
LVH, MI, organic heart disease, congenital heart disease, degenerative conduction system
Rarely seen in a normal heart
How can you identify a right bundle branch block on an ECG (three things)?
- Secondary R wave (R1) in V1 and V2. R’ is usually taller
- Prominent slurred S waves in leads I, aVL, V5, and V6
- Secondary ST and T wave changes may or may not be seen in V1 and V2
Do we ever seen right bundle branch block in normal hearts?
Yes, juveniles often have incomplete RBBB on ECG
Right bundle branch block is seen in what pathologies?
Hypertensive heart disease, cardiomyopathy, degenerative disease of the conduction system, Cor pulmonale, etc
If QRS morphology does not resemble either a typical RBBB or LBBB what do we call this?
Non-specific intraventricular conduction delay (QRS > 100 msec)
What is the most common intraventricular conduction delay?
Left anterior fascicular block
How can you identify a left anterior fascicular block on an ECG?
QRS delay of 90 to 110 msec; left axis deviation (between -45 and -90 degrees); S wave > R wave in II, III, aVF
How can you differentiate a left anterior fascicular block from a posterior block?
Posterior has a right axis deviation whereas an anterior has a left axis deviation
What is a bifascicular block?
RBBB plus fascicular block + either left or right axis deviation
** Must exclude other causes for axis deviation
What is ventricular pre-excitation?
An electrical connection between the atrium and ventricle that allows an electrical impulse to bypass the AV node
These connections are called accessory pathways & can exist anywhere along the septum and the tricuspid and mitral valve annuli
Ventricular pre-excitation is part of what syndrome?
WPW (Wolff, Parkinson, White) Syndrome
** Must have palpitations along with pre-excitation to be WPW, otherwise its just WPW pattern
What direction does conduction travel in ventricular pre-excitation?
Both directions
Atrium to ventricle = antegrade
Ventricle to atria = retrograde
When conduction is present in antegrade what do we see on ECG?
Delta wave (slurred upstroke of the QRS) and a shortened PR interval
What is “orthodromic AV reentrant tachycardia”?
Narrow SVT complex
90% of WPW patients will have this
What are the three ECG findings for WPW syndrome?
- Short PR interval < 120 msec
- Delta wave (every beat is a fusion beat)
- Prolonged QRS
What is a delta wave?
Seen in pre-excitation; it’s a short PR interval due to conduction through an accessory pathway reaching the ventricle faster than through the AV node. This produces a fused ventricular activation and a short PR interval (< 120msec)
90% of accessory pathway mediated tachycardia use what pathway?
Orthodromic (antegrade)
10% are antidromic (retrograde)
Why are accessory pathways bad?
They conduct rapidly and with short refractory periods (unlike the AV node)
The impulses can induce ventricular fibrillation
What is a 1st degree AV block?
PR interval > 200 msec, P waves are consistently before each QRS
Can happen at any HR
What is a Mobitz I (Wenkebach) AV block?
Second degree AV block
Progressive PR prolongation with eventual non-conduction (dropped beat)
Subtle shortening in each R to R interval
What are the two types of second degree AV block?
Mobitz I (Wenkebach) and Mobitz II
What is a Mobitz II AV block?
2nd degree block
PR interval is stable with intermittent non-conducted (dropped) beats
Which 2nd degree AV block is worse?
Mobitz II
Higher risk of developing complete AV block
What does it mean when we see no QRS complexes on the ECG?
3rd degree heart block
Note: will still see p waves because SA node is firing
What is complete (3rd degree) heart block?
P waves and QRS complexes are happening but there is zero relationship between the two. Just firing on their own
What is advanced heart block?
SOME relationship between P waves and QRS complexes - aka every once in awhile a P wave conducts to a QRS complex but mostly its just all over the place like complete heart block
What is an escape rhythm?
A subsidiary pacemaker that arises from the ventricular septum or ventricle itself during complete AV block
What is a junctional escape rhythm?
Narrow QRS (<120 msec) and a HR 40 - 60 bpm
What is a ventricular escape rhythm?
Wide QRS (> 120msec) and a HR of 20 - 40 bpm)
What is bradycardia with no visible P waves?
Sinus arrest (or sick sinus syndrome)
What is a premature atrial complex (PACs)?
Atrial beats arriving earlier than the expected next sinus beat (looks a little abnormal on ECG)
Typically associated with narrow QRS
What is a premature ventricular complex (PVCs)?
Ventricular beats arriving earlier than the expected R to R interval
no preceding P wave
wide complex
How does supraventricular tachycardia (SVT) appear on ECG?
Narrow and fast with no p-wave
What condition presents with irregular, narrow QRS tachycardia?
Atrial fibrillation
No p waves!!
What conditions present with regular narrow QRS tachycardia?
AVNRT, AVRT/WPW Syndrome, atrial tachycardia, atrial flutter, sinus tachycardia
If you see a “saw tooth” pattern on ECG what should you suspect?
atrial flutter
How does ventricular tachycardia appear on ECG?
Wide QRS, no P wave
Two types of ventricular tachycardia?
- Monomorphic ventricular tachycardia (focal, QRS stays the same)
- Polymorphic VT (ischemia or Torsades de Pointe)
What causes Torsades de Pointe?
Congenital Long QT Syndrome, certain drugs (antibiotics, anti-psychotics, anti-depressants, anti-arrhythmic), and bradycardia-induced long QT
Mutations in what two things cause congenital long QT syndrome?
potassium and sodium channels
What causes Torsades de Pointe?
An abnormality in ventricular repolarization
How does ventricular fibrillation appear on ECG?
Wide, very fast, low amplitude, irregular ventricular rhythm
Causes sudden death unless defibrillated
Three causes of ventricular fibrillation?
- Idiopathic
- Ischemia (acute MI)
- Cardiomyopathy (“a sick heart”)
What is cardiac ischemia?
Diminished blood supply to a certain territory of myocardium
How does cardiac ischemia manifest on an ECG?
Repolarization abnormalities (T wave inversion, ST segment depression)
What leads typically correspond to the right coronary artery?
II, III, and aVF
What leads typically correspond to the left circumflex artery?
I and aVL
What leads typically correspond to the LAD?
V1, V2, V3
What leads typically correspond to the left circumflex artery and LAD?
V4, V5, V6
What amount of ST segment depression is considered significant for ischemia?
More than 1mm (1 small box) in at least 2 contiguous leads
What is myocardial injury?
Absent blood supply to a territory of myocardium
How does myocardial injury manifest on ECG?
Changes in repolarization (ST segment elevation)
What amount of ST segment elevation is considered significant for myocardial injury?
Greater than 1mm (1 small box) of elevation in at least 2 contiguous leads
What finding on ECG tells you the chronicity of a myocardial infarction?
Q waves
If you see this on an ECG then you know an MI event is within 1 to 2 hours old
ST elevation without Q waves
If you see this on an ECG then you know an MI event is within several hours old
Q waves associated with ST elevation
If you see this on an ECG then you know an MI event is at least half a day old (even years old!)
Q waves without ST changes
Q waves are considered representative of infarction if they are at least what height and width?
1 small box deep and one small box wide in at least 2 contiguous leads
