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Transcript of EKG Interpretation
107 Rhythm Strips. Please measure waveforms and interpret rhythm before the next class. We will review your answers at the beginning of class.
Lets do the first few together! Homework Questions? Rhythm is Irregular
Rate – atrial rate can be 400 or more, or uncountable. The ventricular rate will be less than the atrial rate.
P waves – not seen. Wavy deflections are noted.
PR interval – not measurable
QRS – normal, narrow (0.10 seconds or less). Atrial Fibrillation Atrial Fibrillation Originates from an ectopic pacemaker site in the atria
Depolarizes at a rate > 400 beats/min.
Rapid impulses cause the atria to quiver
Irregular, wavy deflections are seen
Large waves are described as coarse
Small waves are described as fine. Atrial Fibrillation Atrial Fibrillation Atrial Flutter Page 95-98 Originates in an ectopic pacemaker site in the atria, depolarizing at a rate of 250-400 beats per minute.
The resulting waveform often looks “sawtooth” and are called Flutter waves or F waves. Atrial Flutter Supraventricular – general term used to describe arrhythmias that originate in sites above the bundle branches, such as the sinus node, atria and atrioventricular junction. Supraventricular Tachycardia (SVT)
AKA Atrial Tachycardia Vagal maneuvers
Calcium channel blocker (Diltiazem)
Beta blocker (Metoprolol)
Cardioversion (50 J) Atrial Tachycardia Treatment Rhythm is regular
P waves – abnormal, commonly pointed
PR interval – usually not measurable
QRS – normal (0.10 seconds or less) Atrial Tachycardia (AT)
AKA Supraventricular Tachycardia (SVT) Non-conducted PACs will have an abnormal P wave and will occur prematurely.
The ectopic atrial focus (origin of the PAC) is so early that the AV node is refractory and the impulse cannot be sent to the ventricles. Non-conducted PAC PAC Underlying rhythm is usually regular
The P wave associated with the PAC is premature and abnormal in size, shape, and direction
The P wave is often small, upright, pointed, and may even be inverted.
An abnormal p wave may be found hidden in the preceding T wave
Compensatory pause after the PAC PACs PACs Premature Atrial Contractions Early beat from ectopic site within the atria
Ectopic site discharges an impulse before the next sinus node impulse is discharged
PACs can originate from one ectopic site or multiple sites within the atria. Premature Atrial Contractions (PACs) PAC Practice Break Time! R to R interval does not resume on time.
P to P interval does not resume on time This is a 6 second strip, what is the approximate heart rate? Sinus Arrhythmia Originates in SA node, but delivers impulse irregularly.
Does not require treatment unless it is causing bradycardia with symptoms of hemodynamic compromise. Sinus Arrhythmia This is a 6 second strip, what is the rate? Sinus tachycardia begins and ends gradually.
Conditions associated with ST include:
sepsis Sinus Tachycardia Originates in the SA node (narrow QRS)
Normal response to body’s increased demand for blood flow. Sinus Tachycardia Must be administered correctly
Given too slowly or in doses of less that 0.5 mg can actually slow the heart rate further Atropine Sinus Bradycardia Treatment Basic treatment – maintain airway, oxygen, monitor ECG, establish IV access.
Cough – this can decrease vagal tone and might be tried to increase the heart rate.
Persistent SB – atropine 0.5 mg to 1.0 mg. May repeat up to maximum dose of 3 mg. Sinus Bradycardia Treatment This is a 3 second strip, what is the rate? Signs of poor cardiac output (patient is not tolerating rhythm):
Pale, cool, clammy skin, cyanosis
Confusion, disorientation, dizziness
Unresponsiveness Sinus Bradycardia Vomiting
Drugs such as: Digitalis, morphine, sedatives, calcium channel blockers, beta blockers.
MI (Reperfusion Rhythm)
Vagal Stimulation & Vasovagal reactions
Hypothyroidism, Hypothermia, and hyperkalemia
Increased Intracranial Pressure
Degenerative diseases as SSS Causes of Sinus Bradycardia Can be normal for athletes or when sleeping.
Does not require treatment unless patient shows signs of poor cardiac output. Sinus Bradycardia Rhythm is regular (follows normal conduction pathway)
Rate is 40 to 60
Upright P wave before every QRS
PR interval is normal (0.12 - 0.20 seconds)
QRS is normal (0.12 seconds or less) Sinus Bradycardia This is a 6 second strip, what is the rate? Describe basic underlying rhythm first
Then add additional information.
Sinus rhythm with premature atrial contraction Irregular Rate/Sinus Arrhythmia This is a 3 second strip. How fast is the rhythm? Sinus Rhythm Rhythm is regular
Rate of 60 to 100 beats per minute
P wave before every QRS
PR interval between 0.12 and 0.20 seconds
QRS is 0.12 seconds or less Sinus Rhythm
Normal Rhythm – requires no treatment Bundle branch block QRS is wide (greater than 0.12 seconds) Ventricular Rhythm QRS is narrow (0.10 seconds or less)
AKA: Supraventricular Atrial Rhythm Atrial vs. Ventricular Analyzing a Rhythm Strip Determine regularity (rhythm)
Calculate the rate
Examine P waves
Measure the PRI
Measure the QRS Analyzing Rhythm Strips 15 minute Break Practice makes perfect Determine regularity
Calculate the rate
Examine P waves
Measure the PRI
Measure the QRS Interpreting the Rhythm QRS Complexes
Are all QRS complexes present?
Do all QRS complexes look alike?
Is there a QRS for every P wave?
Are the R to R intervals equal?
Are all QRS complexes within normal range (less than .12 seconds)? Interpreting the Rhythm P Wave – examine each for:
Are all P waves present?
Are they all upright?
Do they all look alike?
Is there a P wave before every QRS?
Are the P to P intervals equal? Interpreting the Rhythm Irregular rhythm; R-R intervals vary by 0.32 second. Regular rhythm; R-R intervals do not vary Determine rhythm regularity If the QRS is narrow (< .12) the rhythm is atrial in origin
If the QRS is wide (> .12) the rhythm is ventricular Interpreting arrhythmias
Where is it originating from? Normal ECG Causes of prolonged QT Interval Indicates a delay in ventricular repolarization
This lengthens the refractory period (the vulnerable period of repolarization
Puts ventricles at risk for life threatening arrhythmias such as torsades de pointes ventricular tachycardia. Prolonged QT interval Represents the onset of ventricular depolarization and the end of ventricular repolarization.
Measured from the beginning of the QRS to the end of the T wave
Normal value is rate dependant and is considered to be less than half of the R-R Interval QT Interval QT Interval Represents ventricular repolarization
Normal T waves are rounded and slightly asymmetrical.
T wave always follows QRS complex (repolarization always follows depolarization) T wave ST Segment – signs of ischemia ST Segment/J point ST segment elevation – myocardial injury, coronary vasospasm, pericarditis, hyperkalemia
ST segment depression – myocardial ischemia, hypokalemia What does the ST segment tell us? Measuring the QRS Measured from the beginning of the QRS (first wave leaves baseline) to the end (when the last wave of the complex begins to level out in the ST segment).
Duration of 0.10 seconds or less
Abnormal is wide, with a duration of 0.12 seconds or more. QRS The QRS complex represents the electrical conduction from the Bundle of His throughout the ventricular myocardium (ventricular depolarization).
Largest complex of the EKG because it represents the depolarization of the largest muscles of the heart. For a wave to be a Q wave, it must be a negative (downward) deflection.
First deflection of the QRS complex followed by an R wave
For a wave to be an R wave, it must be a positive (upward) deflection. All positive deflections are R waves
For a wave to be an S wave, it must be a negative deflection & Follow an R wave QRS Consists of Q, R and S waves QRS Complex Prolonged PRI are seen in first degree AV block. PR Interval (PRI) PRI Represents the time from onset of atrial depolarization to the onset of ventricular depolarization.
Measured from the beginning of the P wave to the beginning of the QRS. PR Interval (PRI) PR interval – the time it takes for the impulse to travel through both atria and to the AV node (normal is 0.12-.20 seconds or 3-5 small squares). PR Interval An ectopic P wave arises form a site other than the SA node.
They are abnormal in size and shape
P wave may be small and pointed, inverted, or absent. Ectopic P waves Enlargement of the right atrium produces tall, peaked P waves. This is a sign of severe pulmonary disease.
Enlargement of the left atrium produces a P wave that is wide and notched. Left atrial enlargement is seen in patients with mitral or aortic valve disease, hypertension, coronary artery disease and other cardiomyopathies. Abnormal P waves P Waves P Waves Normal P waves are:
Smooth, Round & Upright
One P wave per QRS complex
0.10 second in width
Low amplitude, 2.5mm in height. P Waves P wave is the first positive (upward) deflection before the QRS complex.
Represents depolarization of both atria.
Repolarization wave is buried in the QRS P Waves P, QRS, T P wave – depolarization of both atria (repolarization buried in QRS)
PR interval – the time it takes for the impulse to travel through both atria
and to the AV node (normal is 0.12-.20 seconds or 3-5 small squares).
QRS – ventricular depolarization – impulse conducted through the
Bundle of His to the ventricular muscle.
ST segment – Repolarization of the ventricles. Rate:
1 small square = 0.04 seconds
5 small squares = 0.20 seconds
15 large squares = 3 seconds
30 large squares = 6 seconds
300 large squares = 1 minute Measuring Rhythm Strips EASI Lead Placement Tricks to remember where leads are placed:
White rhymes with right
Clouds over grass
Black = smoke
Red = fire…smoke always above the fire. 5 Lead Placement (SA) Sinoatrial node (60-100 electrical pulses per minute)
Internodal and intra-atrial pathways
(AV) Atrioventricular node (40-60 electrical impulses per minute)
Bundle of His (impulses generated below the AV node are generated at 20-40 impulses per minute)
Purkinje’s fibers (20-40 bpm)
Ventricular muscle (20-40 bpm) Electrical Conduction Pathway At the end of today’s lecture and activities, the learner will be able to:
Discuss heart physiology
Identify normal sinus rhythm (NSR)
Measure PRI, QRS, and QT interval
Identify Sinus Bradycardia, Sinus Tachycardia, SVT
Tell the difference between atrial and ventricular arrhythmias.
Lead Placement Day 1 Objectives The AV node is overwhelmed by the rapid Atrial impulses and only conducts some impulses to the ventricles.
The AV node blocks at least half of these impulses to protect the ventricles. Atrial Flutter Paroxysmal – Sudden onset
You must SEE the onset to call it Paroxysmal. Paroxysmal Atrial Tachycardia (PAT) aka Paroxysmal Supraventricular Tachycardia (PSVT) Rhythm is regular
Rate is 100 to 150
P wave before every QRS
PR is normal (0.12 to 0.20 Seconds)
QRS: Normal (0.10 seconds or less) Sinus Tachycardia Calipers work best
When calipers are not available, use a blank piece of paper and pencil. Practice Small deflection sometimes seen following the T wave
Neither its presence nor absence is considered normal
Represents late polarization of a small segment of the ventricles. U waves Abnormal T waves may be tall or low, flattened, biphasic, or inverted.
Common causes of T wave abnormalities are:
bundle branch blocks. Abnormal T waves ST Segment What is the heart rate? This is a 3 second strip. 15 large boxes. Normal Sinus Rhythm PR Interval Caused when the electrical impulse leaves the SA node and travels through abnormal tissue. This can cause the P wave to have greater amplitude and width. Abnormal P waves The black and white leads are placed on the shoulder area where the shoulder connects to the torso.
The green and red leads are placed on the lowest rib on both sides of the torso, and the brown lead is placed at the 4th intercostal space, just to the right of the sternum. Typical 5 Lead Placement Compare length of R-R intervals to determine if it is arrest or block Basic rhythm is regular with a sudden pause.
Block = SA initiated impulse, but was blocked (R-R resumes on time). Sinus Block Basic rhythm is regular with a sudden pause.
Arrest = failure of SA
(R-R does not resume on time) Sinus Arrest Sinus Arrest vs. Sinus Block PR Intervals:
Are PRIs present?
Are all PRIs equal?
Are all PRIs within the normal range of 0.12-0.20 second? Practice Questions? Hypokalemia
Liquid protein diets
Idiopathic (without known cause) Sinus Tachycardia Rate Greater than 100bpm, less than 150 bpm
P waves and T waves usually visible. This is a 6 second strip, what is the heart rate? Sinus Rhythms
Practice Rhythm Strips If SB does not resolve with Atropine a temporary pacemaker may be needed.
All medications that cause a decrease in heart rate should be reviewed and discontinued if indicated.
For chronic bradycardia, permanent pacing may be indicated.