ECG Interpretation Flashcards
P wave
Atrial depolarization
PR interval
Time for atrial depolarization and condition form the SA node to the AV node
What is normal duration for the PR interval?
0.12 to 0.20 seconds
QRS complex
Ventricular depolarization and atrial repolarization
Normal QRS duration?
0.06 to 0.10 seconds
QT interval
Time for both ventricular depolarization and repolarization.
Normal QT duration
Ranges for 0.20 to 0.40 seconds; depending on HR
ST segment
Isoelectric period following QRS when the ventricles are depolarized
T wave
Ventricular repolarization
Normal sinus rhythm
Atrial depolarization begins in the SA node and spreads normally throughout the electrical conduction system
HR b/t 60 and 100 BPM
Sinus Bradycardia
Sinus rhythm with a HR <60 bpm (in adults)
Sinus tachycardia
Sinus rhythm with a HR > 100 bpm (in adults)
Sinus arrhythmia
A sinus rhythm, but with quickening and slowing of impulse formation in the SA node resulting in a slight beat-to-beat variation of the rate
Sinus arrest
A sinus rhythm, except with intermittent failure of either SA node impulse formation or AV node condition that results in the occasion complete absence of P or QRS waves
Premature atrial contractions (PAC)
- occur when an ectopic focus in the atrium intimates an impulse before the SA node
- The p wave is premature with abnormal configuration
Atrial flutter
- ectopic, very rapid atrial tachycardia
- rate of 250-350 bpm; ventricular rate dependent upon AV node conduction
- Saw-tooth shaped P waves (also known as atrial flutter waves) are characteristic
A therapist is trying to determine the HR of a normal heart rhythm using a 6 second strip. How would he/she determine the HR?
Therapist should count the number of intervals b/t QRS complexes in 6-second strip and multiply by 10
A therapist is trying to determine the HR of a irregular heart rhythm using a 6 second strip. How would he/she determine the HR?
Therapist should use the longest strip available (up to 1 minute) to assess HR
What are premature ventricular contractions (PVCs)?
Premature beat arising from the ventricle
How do PVCs look on a ECG strip?
- No p wave
2. A bizarre and wide QRS complex followed by long compensatory pause
When are PVCs considered a Red Flag?
> 6 PVCs per minute occurring in pairs, or sequential runs, multifocal, very earl PVC (R on T phenomena)
What is a bigeminy PVC?
Normal sinus impulse followed by a PVC
What is a trigeminy PVC?
A normal sinus impulse followed by two PVCs.
What are some causes of PVC?
- Anxiety
- Caffeine
- Stress
- Smoking
- All forms of Heart disease
What is ventricular tachycardia (V-tach)?
A run of 3+ PVCs occurring sequentially; very rapid rate (150-200 bpm)
May occur paroxysmally (abrupt onset)
What does V-tach look like on a ECG stripe?
- No p waves
2. QRS waves are wide and aberrant in appearance
What is nonsustained v-tach (NSVT)?
3+ consecutive beats in duration, terminating spontaneously in <30seconds
What is sustained V-tach?
VT >30 second durations and/or requiring termination due to hemodynamic compromise in <30 seconds
> 30 seconds = life threatening !
If a therapist is assessing a patient and realizes their patient has had VT for more than 30 seconds, what should the therapist proceed to do.
Initiate emergency services
True or False: Patients experiencing VT may be unable to keep appropriate BP, therefore they may experience hypotension
True
True or False: VT may degenerate into Vfib causing cardiac arrest
True
What are common causes of VT?
- MI
- Cardiomyopathy
- Valvular disease
What is Ventricular fibrillation (Vfib)?
Chaotic activity of vetricle originating from multiple foci
Unable to determine rate
What does Vfib look like on ECG?
bizarre, erratic activity without QRS complexes
No effective Cardiac output (CO)
How quickly can clinic death occur if a patient is experiencing Vfib?
Clinical death occurs within 4-6 minutes
True or False: A pulseless, emergency situation requiring immediate medical attention: CPR typically required!
TRUE!! VFIB IS A SERIOUS EMERGENCY
What are common causes of VFib?
- Any heart disease
- MI
- Cocaine use
What is Ventricular Asystole?
Ventricular standstill; straight line on ECG
T or F: Ventricular Asystole requires CPR and medications to stimulate cardiac activity
True
What are common causes of Ventricle Asystole?
- Acute MI
- Ventricular rupture
- Cocaine use
- Lightening Strike
- Electrical shock
What is Atrial fibrillation?
P waves area abnormal (variable in shape) or not identifiable
Depolarizes between 350-600 times/minute
What are common symptoms of Afib?
- Palpitations
- Fatigue
- Dyspnea
- Lightheadedness
- Syncope
- Chest pain
True or false: With afib, stagnation of blood may predispose to thrombi in the atria
True
What is atrial flutter?
Very rapid atrial tachycardia
(250-350 bpm)
Ventricular rate depends on AV node conduction
What does Atrial flutter look like on ECG?
Saw-tooth shaped P waves (also known as flutter waves)
What are some symptoms of Atrial flutter?
- Palpitations
- Lightheadedness
- Aging due to rapid rate
Stagnation of blood in atria may predispose to thrombin in the atria
List the type of Atrioventricular Conduction blocks.
- 1st degree heart block
- 2nd degree heart block
- 3rd degree heart block
In a 1st degree heart block, the PR interval is _________ than ____ seconds, but relatively constant from beat to beat
Longer than 0.2 seconds
Why may a 1st degree heart block occur?
For many reasons including medications that suppress AV conduction
2nd degree heart block is a ____ conduction disturbance in which impulses between the atria and vertices fail intermittently
AV conduction
Name the two types of 2nd degree heart block
Mobitz I Block
Mobitz II block
Describe 2nd degree heart block: Mobitz I
Progressive prolongation of PR interval until one impulse is not conducted (generally benign)
Describe 2nd degree heart block: Mobitz II
Consecutive PR intervals are the same and normal followed by non conduction of 1+ impulses
True of false: 2nd degree heart block may progress to 3rd degree heart block
True
True or false: If HR is slow, CO will decrease with the blocked impulse during mobitz II heart block
True
Which is more serious: Mobitz I or Mobitz II
Mobitz II
describe a 3rd degree AV block.
All impulses are blocked at the AV node and more are transmitted to the ventricles
Atrial rate > ventricle rate
True or False: A third degree AV block is a medical emergency and will require pacemaker and medication
True
what medication is given for a patient with third degree HR block?
Atropine
True or false: if the ventricular rate is too slow, the cardiac output drops and the patient may faint
True
Hypothermia affects heart rhythm in what way?
Elevates ST segment; slows rhythm
how does digitalis affect the heart rate rhythm?
A. Depresses ST segment
B. flattens T wave (or inverts)
C.QRS lengthens
How do beta blockers (propanol) affect HR and its rhythm?
Decreases HR
Blunts HR response with exercise
How do nitrates (nitroglycerin) affect HR?
increase HR
How do antiarrhythmic agents affect heart rhythm ?
May prolong QRS and QT intervals
What is ST segment depression typically indicative of? What else may cause this?
Typically indicative of MI.
May also be caused by digitalis toxicity and hypokalemia
ST segment elevation (STEMI) is the earliest sign of what?
Transmural infarction (large MI—usually affects entire ventricular wall)
Produces pathological Q waves hrs/days later—QMI = Transmural
What is a characteristic marker of infarction and signifies the loss of (+) electrical voltages due to necrosis?
Q wave —usually longer than 0.04 msec and larger than 1/3 amplitude of the R wave (STEMI)
When does a T wave inversion typically occur?
Usually occurs hours or days after an MI as the result of a delay in depolarization produced by injury
ST segments not seen on a ECG are termed NSTEMI, this involves what portion of the heart?
Involves endocardium (known as nontransmural or subendocardial MI)
Does not acause acute injury to myocardial tissue
