ekg basics - המרכז הרפואי הלל...
TRANSCRIPT
OutlineOutline
1.1. Review of the conduction systemReview of the conduction system
2.2. EKG waveforms and intervalsEKG waveforms and intervals
3.3. EKG leadsEKG leads
Determining heart rateDetermining heart rate4.4. Determining heart rateDetermining heart rate
5.5. Determining QRS axisDetermining QRS axis
What is an EKG?What is an EKG?
The electrocardiogram (EKG) is a The electrocardiogram (EKG) is a
representation of the electrical events of the representation of the electrical events of the
cardiac cycle.cardiac cycle.
Each event has a distinctive waveform, the Each event has a distinctive waveform, the
study of which can lead to greater insight study of which can lead to greater insight
into a patient’s cardiac pathophysiology.into a patient’s cardiac pathophysiology.
What types of pathology can we What types of pathology can we
identify and study from EKGs?identify and study from EKGs?
ArrhythmiasArrhythmias
Myocardial ischemia and infarctionMyocardial ischemia and infarction
PericarditisPericarditisPericarditisPericarditis
Chamber hypertrophyChamber hypertrophy
Electrolyte disturbances (i.e. Electrolyte disturbances (i.e. hyperkalemia, hypokalemia)hyperkalemia, hypokalemia)
Drug toxicity (i.e. digoxin and drugs which Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)prolong the QT interval)
EKG LeadsEKG Leads
Leads are electrodes which measure the Leads are electrodes which measure the
difference in electrical potential between difference in electrical potential between
either:either:
11. . Two different points on the body (bipolar leads)Two different points on the body (bipolar leads)
22. . One point on the body and a virtual reference point One point on the body and a virtual reference point
with zero electrical potential, located in the center of with zero electrical potential, located in the center of
the heart (unipolar leads)the heart (unipolar leads)
EKG LeadsEKG Leads
The standard EKG has The standard EKG has 12 12 leads:leads: 3 Standard Limb Leads
3 Augmented Limb Leads
6 Precordial Leads
The axis of a particular lead represents the viewpoint from The axis of a particular lead represents the viewpoint from
which it looks at the heart.which it looks at the heart.
Summary of LeadsSummary of Leads
Limb LeadsLimb Leads Precordial LeadsPrecordial Leads
BipolarBipolar I, II, IIII, II, III --((standard limb leads)standard limb leads)
UnipolarUnipolar aVR, aVL, aVF aVR, aVL, aVF ((augmented limb leads)augmented limb leads)
VV11--VV66
Determining the Heart RateDetermining the Heart Rate
Rule of Rule of 300300
10 10 Second RuleSecond Rule
Rule of Rule of 300300
Take the number of “big boxes” between Take the number of “big boxes” between
neighboring QRS complexes, and divide this neighboring QRS complexes, and divide this
into into 300300. The result will be approximately . The result will be approximately
equal to the rateequal to the rateequal to the rateequal to the rate
Although fast,Although fast, this method only works for this method only works for
regular rhythms.regular rhythms.
The Rule of The Rule of 300300
It may be easiest to memorize the following table:It may be easiest to memorize the following table:
# # of big of big
boxesboxes
RateRate
11 30030011 300300
22 150150
33 100100
44 7575
55 6060
66 5050
10 10 Second RuleSecond Rule
As most EKGs record As most EKGs record 10 10 seconds of rhythm per seconds of rhythm per
page, one can simply count the number of beats page, one can simply count the number of beats
present on the EKG and multiply by present on the EKG and multiply by 6 6 to get the to get the
number of beats per number of beats per 60 60 seconds.seconds.number of beats per number of beats per 60 60 seconds.seconds.
This method works well for irregular rhythms.This method works well for irregular rhythms.
What is the heart rate?What is the heart rate?
33 x 6 = 198 bpm
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/
The QRS AxisThe QRS Axis
The QRS axis represents the net overall The QRS axis represents the net overall
direction of the heart’s electrical activity.direction of the heart’s electrical activity.
Abnormalities of axis can hint at:Abnormalities of axis can hint at:
Ventricular enlargementVentricular enlargement
Conduction blocks (i.e. hemiblocks)Conduction blocks (i.e. hemiblocks)
The QRS AxisThe QRS Axis
By near-consensus, the
normal QRS axis is defined
as ranging from -30° to +90°.
-30° to -90° is referred to as a
left axis deviation (LAD)
+90° to +180° is referred to as
a right axis deviation (RAD)
Determining the AxisDetermining the Axis
The Quadrant ApproachThe Quadrant Approach
The Equiphasic ApproachThe Equiphasic ApproachThe Equiphasic ApproachThe Equiphasic Approach
The Quadrant ApproachThe Quadrant Approach
11. . Examine the QRS complex in leads I and aVF to determine Examine the QRS complex in leads I and aVF to determine
if they are predominantly positive or predominantly if they are predominantly positive or predominantly
negative. The combination should place the axis into one negative. The combination should place the axis into one
of the of the 4 4 quadrants below.quadrants below.
The Quadrant ApproachThe Quadrant Approach
22. . In the event that LAD is present, examine lead II to In the event that LAD is present, examine lead II to determine if this deviation is pathologic. If the QRS in II is determine if this deviation is pathologic. If the QRS in II is predominantly positive, the LAD is nonpredominantly positive, the LAD is non--pathologic (in other pathologic (in other words, the axis is normal). If it is predominantly negative, it words, the axis is normal). If it is predominantly negative, it is pathologic. is pathologic.
Quadrant Approach: Example Quadrant Approach: Example 11
Negative in I, positive in aVF � RAD
The Alan E. Lindsay
ECG Learning Center
http://medstat.med.utah.
edu/kw/ecg/
Quadrant Approach: Example Quadrant Approach: Example 22
Positive in I, negative in aVF ���� Predominantly positive in II ����
Normal Axis (non-pathologic LAD)
The Alan E. Lindsay
ECG Learning Center
http://medstat.med.utah.
edu/kw/ecg/
The Equiphasic ApproachThe Equiphasic Approach
11. . Determine which lead contains the most equiphasic QRS Determine which lead contains the most equiphasic QRS complex. The fact that the QRS complex in this lead is complex. The fact that the QRS complex in this lead is equally positive and negative indicates that the net equally positive and negative indicates that the net electrical vector (i.e. overall QRS axis) is perpendicular electrical vector (i.e. overall QRS axis) is perpendicular to the axis of this particular lead.to the axis of this particular lead.
22. . Examine the QRS complex in whichever lead lies Examine the QRS complex in whichever lead lies 9090°°away from the lead identified in step away from the lead identified in step 11. If the QRS . If the QRS complex in this second lead is predominantly positive, complex in this second lead is predominantly positive, than the axis of this lead is approximately the same as than the axis of this lead is approximately the same as the net QRS axis. If the QRS complex is predominantly the net QRS axis. If the QRS complex is predominantly negative, than the net QRS axis lies negative, than the net QRS axis lies 180180°° from the axis from the axis of this lead.of this lead.
Equiphasic Approach: Example Equiphasic Approach: Example 11
Equiphasic in aVF ���� Predominantly positive in I ���� QRS axis ≈ 0°
The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/