EKGs Flashcards
Systematic Reading
- Rate
- Rhythm
- Axis
- Intervals
- Bundle branch block
- Enlargement and hypertrophy
- Ischemic changes
In normal sinus rhythm, what is defined as tachycardia and bradycardia, respectively?
Tachycardia: >100 bpm
Bradycardia: <60 bpm
What is the rate of paper of the EKG recording?
25 mV/s
Length/seconds of one small box? One big box?
Small box: 1 mm = 0.04 seconds
Large box: 5 mm = 0.2 seconds
3 ways to calculate the HR?
- 60/R-R interval
- If R-R interval is 1 big box -> 300 bpm, 2 big boxes -> 150 bpm, 3 big boxes -> 100 bpm, 4 big boxes -> 75 bpm, 5 big boxes -> 60 bpm
3 Count the # of RR intervals on the EKG (normally 10 seconds long), multiply by 6
Which of the previous 3 methods of calculating the HR is more effective when the rhythm is irregular?
Number of RR intervals x 6
Broad categories of rhythm?
- Regular: constant RR interval, may be brady or tachy
- Basically regular: PVCs, PACs, escape ectopic beats
- Regularly irregular: RR interval variable but with a pattern
- Irregularly irregular: RR interval variable with no pattern
Shortcut to define a normal axis (0 to +90 degrees)?
QRS complex upright (positive) in I and aVF
Shortcut to define a left axis deviation (0 to -90 degrees)? What is the exception?
QRS complex upright in I and downward (negative) in aVF
IF II is upward -> normal axis
Shortcut to define a right axis deviation?
QRS complex downward (negative) in I and upward (positive) in aVF
Shortcut to define an indeterminate axis?
QRS predominantly downward in both leads I and aVF
Define normal PR interval.
Measured from beginning of P to beginning of QRS
Normal: 0.12-0.20 seconds
What syndrome is associated with a short PR interval and what causes it?
Wolff-Parkinson-White syndrome; accessory pathway (Kent bundle) connects the R atrium to the R ventricle or the L atrium to the L ventricle, and this permits early activation of the ventricles (delta wave) and a short PR interval
Define types of prolonged PR intervals
- First degree AV block (constant but prolonged PR)
- Second degree AV block (PR interval may be normal or prolonged, but some P waves do not conduct)
2a. Type I (Wenckebach): increasing PR until non-conducted P wave occurs
2b. Type II (Mobitz): fixed PR intervals plus non-conducted P waves - AV dissociation (some PRs prolonged, but P and QRS are dissociate -> both march out, but are not related)
Define normal, intermediate, and abnormal QRS intervals.
Normal: 0.08-0.1 seconds
Intermediate (incomplete BBB): 0.10-0.12 seconds
Abnormal (BBB): >0.12 seconds
What causes prolongation of QRS complex electrically? Examples of etiologies?
Delayed conduction through the ventricles, leading to prolongation; BBBs, drug toxicity, electrolyte imbalance
Define normal and abnormal QT intervals.
Measured from beginning of QRS to end of T wave
Normal: HR dependent, so must correct (QTc) = QT/(square root of RR in seconds)
Upper limit for QTc = 0.44 seconds
Diagnostic criteria for long QT syndrome?
QTc 0.47+ seconds for males and 0.48+ seconds for females in the absence of other causes of increased QT
Why does prolonged QT matter?
Increased vulnerability to malignant ventricular arrhythmias, syncope, and sudden death. Prototypical arrhythmic is Torsade-de-pointes (polymorphic ventricular tachycardia with varying QRS morphology and amplitude around isoelectric baseline)
EKG findings of LBBB?
- If complete, QRS of 0.12+ seconds
- Terminal forces (i.e., 2nd half of QRS) are oriented leftward and posteriorly (because L ventricle depolarized after R ventricle)
- Terminal S waves (VI)
- Terminal R waves (I, aVL, V6) -> broad, monophasic
- Poor R progression from V1 to V3
- Expect ST-T waves oriented opposite to the direction of the terminal QRS forces
Diagnostic criteria for LBBB?
- QRS duration of 120+ ms
- Dominant S wave in V1
- Broad monophasic R waves in lateral leads (I, aVL, V5-V6)
- Absence of Q waves in lateral leads (I, V5-V6; small Q waves permitted in aVL)
- Prolonged R wave peak time >60 ms in L precordial leads (V5-6)
Associated features of LBBB (not diagnostic criteria)?
- Appropriate discordance - ST segments and T waves always go in opposite direction to the main vector of the QRS complex
- Poor R wave progression in the chest leads
- Left axis deviation
EKG features of RBBB?
- If complete, QRS of 0.12+ seconds
- Terminal forces (2nd half of QRS) are oriented rightward and anteriorly because R ventricle is depolarizing after the L
- Terminal R’ wave in lead V1 (usually see rSR’ complex)
- Terminal S waves in I, aVL, V6 indicating late rightward forces
- Terminal R wave in lead aVR indicating late rightward forces
The frontal plane QRS axis in RBBB should be in the normal range (-30 to +90 degrees). If left axis deviation is present, think about ___. If right axis deviation is present, think about ___.
L anterior fascicular block; L posterior fascicular block in addition to RBBB
Diagnostic criteria of RBBB?
- Broad QRS >120 ms
- RSR’ pattern in V1-V3 (M shaped)
- Wide, slurred S wave in lateral leads (I, aVL, V5-V6)
Associated features of RBBB (not diagnostic criteria)?
ST depression and T wave inversion in R precordial leads (V1-3)
Describe normal activation of the left ventricle.
Proceeds down the L bundle branch, which consists of 3 fascicles:
- L anterior
- L posterior
- Septal
Define left anterior fascicular block.
Characterized by L axis deviation
- Widened QRS but <0.12
- Q wave in 1 and aVF
- Predominantly negative QRS in inferior leads (often deep S waves)
Define left posterior fascicular block.
Characterized by R axis deviation
- Widened QRS but <0.12
- Small R wave and deep S wave in I and aVF
- Large R wave in inferior leads
What is a bifascicular block?
2 fascicles blocked, so conduction to ventricles occurs through the remaining fascicle
RBBB + either LAFB or LPFB
EKG usually shows RBBB + L axis deviation OR R axis deviation
Right atrial enlargement on EKG?
P wave amplitude >2.5 mm in II and/or >1.5 mm in V1 -> not very specific or sensitive
Better criteria derived from the QRS complex:
- QR, Qr, qR, or qRs morphology in lead V1 (in the absence of coronary heart disease)
- QRS voltage in V1 <5 mm and V2/V1 voltage ratio is >6 (90% specific, 50% sensitive)
Left atrial enlargement on EKG?
P wave duration 0.12+ in frontal plane (usually lead II)
- Notched P wave in limb leads with inter-peak duration 0.04+ seconds
- Terminal P negativity in lead V1 duration >0.04 s, depth >1 mm
Bi-atrial enlargement on EKG?
Features of both RAE and LAE in same EKG
P wave in lead II >2.5 mm tall and >0.12 seconds in duration
Initial positive component of P wave in V1 >1.5 mm tall and prominent P-terminal
Left Ventricular Hypertrophy voltage criteria on EKG (limb leads)?
R wave in lead I + S wave in lead III >25 mm
R wave in aVL > 11 mm
R wave in aVF >20 mm
S wave in aVR > 14 mm
Left Ventricular Hypertrophy voltage criteria on EKG (precordial leads)?
R wave in V4, V5, or V6 >26 mm
Largest R wave + largest S wave in precordial leads > 45 mm
S wave depth in V1 + tallest R wave height in V5-V6 >35 mm (most common)
Left Ventricular Hypertrophy non-voltage criteria on EKG?
Increased R wave peak time >50 ms in leads V5 or V6
ST segment depression and T wave inversion in L-sided leads aka LV strain pattern
Common additional findings in LVH?
Left axis deviation
Left atrial enlargement
ST elevation in the R precordial leads V1-V3 (discordant to the deep S waves)
RVH diagnostic criteria?
- Right axis deviation of +110 or more
- Dominant R wave in V1 (>7 mm tall or R/S ratio >1)
- Dominant S wave in V5 or V6 (>7 mm deep or R/S ratio <1
- QRS duration <120 ms
RVH supporting criteria?
R atrial enlargement
R ventricular strain = ST depression/T wave inversion in the R precordial (V1-4) and inferior (II, III, aVF) leads
S1, S2, S3 pattern (far right axis deviation with dominant S waves in leads I, II, III)
Deep S waves in the lateral leads (I, aVL, V5-V6)
Other abnormalities caused by RVH?
RBBB (complete or incomplete)
2 common and 2 uncommon ischemic patterns?
- ST depression
- T wave flattening or inversion
- Hyperactive T waves
- U wave inversion
Which morphology of ST depression is non-specific for myocardial ischemia?
Upsloping ST depression
Which morphologies of ST depression are more indicative of myocardial ischemia?
Horizontal or down-sloping ST depression 0.5+ mm at the J point in 2+ contiguous leads
If 1+ mm -> more specific, worse prognosis
If 2+ mm in 3+ leads -> high probability of NSTEMI, significant mortality
Patterns of T-wave inversion associated with ischemia?
- At least 1 mm deep
- Present in 2+ continuous leads that have dominant R waves (R/S ratio >1)
- Dynamic (not present on old ECG or changing over time)
What is Wellens’ syndrome?
Pattern of inverted or biphasic T waves in V2-V4 in patients presenting with ischemic chest pain that is highly specific for critical stenosis of the Left anterior descending artery
Patients may be pain free by the time the EKG is taken and may have normal or minimally elevated cardiac enzymes. However, they are at extremely high risk for extensive anterior wall MI within the next 2-3 weeks.
Which location of infarction carries the worst prognosis and why?
Anterior, due to larger infarct size
Cause of anterior STEMI?
Occlusion of the left anterior descending artery
How to recognize an anterior STEMI?
ST elevation with Q wave formation in precordial leads IV1-6) +/- the high lateral leads I and aVL)
Reciprocal ST depression in inferior leads (mainly III and aVF)
Cause of inferior MI?
80% LAD
18% dominant Left circumflex artery
Up to 40% of patients with an inferior STEMI will have concomitant ___.
R ventricular infarction
Up to 20% of patients with an inferior STEMI will develop significant bradycardia - why?
2nd or 3rd degree AV block
How to recognize an inferior STEMI?
ST elevation in II, III, aVF
Progressive development of Q waves in II, III, and aVF
Reciprocal ST depression in aVL +/- I
Rx hypotension in R ventricular infarct?
Fluid loading
NITRATES CONTRAINDICATED
How to spot a RV infarction?
First step - suspect in all patients with inferior STEMI -> suggested by ST elevation in V1, ST elevation in lead III>II
ST elevation in V1 + ST depression in V2 is highly specific
Isolated posterior MI is less common, usually occurring with what infarctions?
Inferior or lateral
How to recognize posterior infarction?
Horizontal ST depression
Tall, broad R waves (>30 ms)
Upright T waves
Dominant R wave (R/S ratio >1) in V2
Define sinus arrhythmia
Slight variation, all beats have p waves followed by QRS, same PR interval
Define atrial fibrillation.
Irregularly irregular (no P waves)
Define SVT.
Regular tachycardic rate with narrow QRS complex
Define multifocal atrial tachycardia.
Irregularly irregular, P waves with different morphologies
Define VTach
Regular, tachycardic, wide complex
