Essentials of CardioPulmonary PT Ch 9: ECG's Flashcards
Four elements specifically assessed on a 12-lead ECG
1) Heart Rate
2) Heart Rhythm
3) Hypertrophy
4) Infarction
Assessment of Heart Rate (in BPM) via ECG: 3 methods
1) Six second tracing:
- —-The number of QRS complexes on the 6 second tracing is multiplied by 10.
2) R wave measurement:
- —-a) identify a specific R wave on heavy black line
- —-b) for each heavy black line that follows this R wave, count 300, 150, 100, 75, 60, 50. Where the next R wave falls on this counting is the HR
3) Counting (large) boxes:
- —-a) Count the number of large boxes (5mm or .20sec) between the first and next QRS complex
- —-b) # of large boxes is divided into 300 for HR
- Counting small boxes:
- —-a) count # of small boxes between QRS complexes and divide into 1500.
Wave of atrial depolarization is recorded as…
The P wave
The isoelectric line between the P wave and the QRS is…
the delay of the electrical impulse from the atria caused by the AV node
Single lead monitoring is limited to…
detection of rate and rhythm disturbances; it cannot detect ischemia due to the inability to calibrate radiotelemetry
Single lead monitoring may display artifacts caused by…
1) muscle tremors or movement
2) Loose electrodes
3) Sixty cycle electrical interference
- All P waves are upright, normal in appearance, and identical in configuration; a P wave exists before every QRS complex
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR interval is regular (or, if irregular, the distance between the shortest and longest intervals is less than 0.12s)
- The heart rate is between 60 to 100 BPM
Normal Sinus Rhythm
- All P waves are upright, normal in appearance, and identical in configuration; a P wave exists before every QRS complex
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR interval is regular throughout
- The heart rate is less than 60 BPM
Sinus Bradycardia
- All P waves are upright, normal in appearance, and identical in configuration; a P wave exists before every QRS complex
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR interval is regular throughout
- The heart rate is greater than 100 BPM
Sinus Tachycardia
- All P waves are upright, normal in appearance, and identical in configuration; a P wave exists before every QRS complex
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR interval varies throughout
- The heart rate is between 40 to 100 BPM
Sinus Arrhythmia
Signs/symptoms:
_____ rate increases with inspiration, and decreasing with respiration (Respiratory type)
_____ rate not affected by respiratory cycle
Sinus Arrhythmia: Signs/symptoms/causes of:
- Respiratory: found in young, or elderly at rest and disappears with activity
- Non-respiratory arrhythmia may occur with:
- –infection
- –medication administration (toxicity associated with)
- —-digoxin or morphine
Sinus Arrhythmia tx:
- Respiratory type is benign; no tx
- Non-respiratory: Evaluate for and treat underlying cause
An irregularity in rhythm in which the impulse is initiated by the SA node but with a phasic quickening or slowing of impulse formation usually caused by an alternation in vagal stimulation.
Sinus Arrhythmia
- All P waves are upright, normal in appearance, and identical in configuration; a P wave exists before every QRS complex
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR interval is regular for the underlying rhythm, but occasional pauses are noted
- The heart rate is usually between 40 to 100 BPM
Sinus Pause or Block
When the SA node fails to initiate an impulse, usually for only one cycle
Sinus Pause or Block
Causes of Sinus Pause or Block :
- Sudden increase in Parasympathetic activity
- organic disease of the SA node (sick sinus)
- an infection
- rheumatic disease
- severe infarction or ischemia to the SA node
- Digoxin toxicity
Sinus Pause or Block symptoms
- If the pause or block is prolonged, or occurs frequently…
- > cardiac output is compromised and patient may experience dizziness or syncope
- All P waves are present but vary in configuration; each P wave may look different
- The PR interval is between 0.12s and 0.20s
- The QRS complexes are identical
- The QRS duration is between 0.06s and 0.10s
- The RR intervals vary
- The heart rate is usually less than 100 BPM
Wandering Atrial Pacemaker
The cause of “Wandering Atrial Pacemaker” is usually…
…an irritable focus.
…caused by ischemia or injury to the SA node
…congestive heart failure
…increase in vagal firing
“Wandering Atrial Pacemaker” symptoms…
…usually this arrhythmia does not cause symptoms
Types of Atrial arrhythmias
- Premature atrial complexes
- Atrial tachycardia
- Paroxysmal atrial tachycardia
- Atrial fibrillation
Types of Junctional Arrhythmias (3)
- Premature Junctional or Nodal Complexes
- Junctional or Nodal Rhythm
- Nodal (Junctional) Tachycardia
Heart Blocks (types)
First Degree
Second degree AV block, Type 1
Second Degree AV Block, Type 2
Third Degree AV Block
Ventricular Arrhythmias
- Premature Ventricular Complexes
- Ventricular Tachycardia
- Ventricular Tachycardia: Torsade de Pointes
- Ventricular Fibrillation
Four cell types of the myocardium:
1) Working or Mechanical myocytes
- —-respond to electrical stimulation to contract and pump blood
2) nodal myocytes
- —- highest rhythymicity; slow impulse conduction
3) transitional myocytes
- —- transmit impulses twice as fast as as nodal cells
4) Purkinje cells
- —- low rate of rhythmicity, but high conductivity
Depolarization of the myocardial cell membrane allows the influx of ________ and efflux of _________ ions.
sodium (known as fast channel) ; potassium (known as slow channel)
_____ __________ __________ is present if the depth of the S wave in V1 plus the height of the R wave in V5 is greater than 35mm.
Left ventricular hypertrophy
The cardiac muscle has (3) properties:
1) automaticity
- —- able to discharge electrical stimulus w/o stimulation from a nerve
2) rhythmicity
- —- the regularity with which pace-making activity occurs
3) conductivity
- —-ability to spread impulses to adjoining cells rapidly
Inflammation of the pericardial sac
Acute Pericarditis
The pain of acute pericarditis is usually aggravated by or relieved by…
…respiration and change of position.
ECG findings in acute pericarditis include:
- ST segment elevation
- PR interval depression
- late T-wave inversion
- atrial arrhthmias
Defined as an ectopic focus in either atria that initiates an impulse before the next impulse is initiated by the SA node:
Premature atrial complex
Defined as: An erratic quivering of the ventricular muscle resulting in no cardiac output.
- As in
Ventricular fibrillation
Defined as: An erratic quivering of the ventricular muscle resulting in no cardiac output.
Ventricular fibrillation
The sympathetic and parasympathetic systems discharge what neurotransmitters:
Sympathetic = NE
Parasympathetic = ACh
Increased sympathetic activity:
- increases HR
- increases conduction velocity throughout the AV node
- increases contractility of the heart muscle
- increases irritability of the heart
- Automaticity may also increase
Parasympathetic activity:
- Increased
- Decreased
Increased:
- slows HR
slows conduction through AV node
Decreased:
- increases HR, conduction through the AV node, and irritability of the heart
P wave:
atrial depolarization
PR interval:
depolarization wave reaches AV node and slight pause occurs
QRS complex:
- Depolarization wave reaches Purkinje fibers
- ventricular depolarization
Slight pause following QRS:
- ST segment; initiation of ventricular depolarization
T wave:
- Ventricular depolarization complete
- strictly an electrical event that records the return pf potassium inward and sodium outward; no contraction is occurring
A single lead tracing (rhythm strip) records (3):
- HR
- Heart rhythm
- presence of arrhythmias
Where S wave ends and T wave begins:
…is the beginning of diastole (end of systole)
Sinus bradycardia occurs in:
- endurance trained athletes (normal)
- individuals on beta blocker meds
- when decrease in automaticity of SA node or increased vagal stimulation
- —-such as suctioning or vomiting
- TBI with ICP
- brain tumors
- Second or Third degree heart block
Sinus tachycardia differs from NSR?
- In rate only…it is greater than 100bpm
The pace-making activity in this condition shifts from focus to focus, resulting in a rhythm that is very irregular and without a consistent pattern. Some impulses may arise from AV node:
Wandering atrial pacemaker
Three or more premature atrial complexes in a row:
- HR is usually greater than 100bpm and may be 200bpm
Atrial tachycardia
Sudden onset of atrial tachycardia or repetitive firing from an atrial focus. The underlying rhythm is usually NSR, followed by episodic burst of atrial tachycardia that eventually returns to NSR.
Paroxysmal Atrial Tachycardia
Paroxysmal Atrial Tachycardia:
“All of a sudden my heart was racing away!”
—Initial tx are to try counghing or breath holding with Valsalva
Rapid succession of atrial depolarization caused by an ectopic focus in the atria that depolarizes at a rate of 250 to 350 per minute.
Atrial flutter
Erratic quivering of atrial muscle caused by multiple ectopic foci in the atria that emit electical impulses constantly.
None of these impulses actually depolarize the atria, so no true P waves.
Atrial fibrillation
Occurs when AV node takes over as pacemaker of the heart:
Junctional or nodal rhythm
- absence of P waves before QRS, but retrograde P wave may be identified
- ventricular rate between 40-60bpm
Accelerated rate of discharge when AV tissue is acting as pacemaker
Junctional (Nodal) tachycardia
- absence of P waves , but retrograde P wave may be identified
- Rate usually greater than 100bpm
PVC’s occur…
…when an ectopic focus occurs from somewhere in one of the ventricles
PVC’s appear on a ECG…
…as wide and bizarre looking QRS without a P wave followed by a compensatory pause.
—–this is because of the slow conduction of impulses by ventricular muscle itself
A series of three or more PVC’s in a row defines:
Ventricular tachycardia
- P waves absent
- wide and bizarre QRS complexes
- Ventricular rate between 100 and 250bpm
- precursor to ventricular fibrillation
Unique configuration of ventricular tachycardia associated with QT interval greater than .5 sec.
Ventricular Tachycardia: Torsade de Pointes
- twisting around iso-electric line
- characteristically occurs at a rapid rate and terminates spontaneously
