ECG Interpretation Flashcards
What are the two ways to measure heart rate with an ECG?
- Divide 60 by the time measured between waves of the same type.
- Count the number of large boxes (corresponding to 0.2 sec) between waves. 1 box = 300 beats/min, 2 boxes = 150, 3 = 100, 4 = 75, 5 = 60, 6 = 50.
In analyzing rhythm on an ECG, what are three things to determine?
- Where is the pacemaker?
- What is the conduction path from the pacemaker to the final ventricular cell that depolarizes?
- Is the pacemaker functioning regularly and at the correct speed?
What is the term used for a heart that has a normal rate and rhythm?
Normal sinus rhythm
What is the normal range for the frontal plane mean axis of ventricular depolarization?
Between -30 and +90 degrees
What is an arrhythmia?
Any change from normal sinus rhythm
What is sinus tachycardia and what may cause it?
Increased HR (over 100 bpm) due to sympathetic stimulation or exercise.
What is sinus arrhythmia?
Normal subtle change in HR with each respiratory cycle. Inspiration accelerates the heart rate. Expiration slows it due to an increase in vagal tone.
A major cause of arrhythmias is __________ abnormalities.
conduction
What is Wolff-Parkinson-White Syndrome? What change is seen on an ECG?
An example of abnormal anatomy in which there is an accessory conduction pathway from the atria called the Bundle of Kent that bypasses the AV node, allowing depolarization to arrive at the ventricles faster than normal. On ECG the QRS complex is biphasic. (Delta wave)
What is a first degree AV block? What change in seen on ECG?
A slowing of the conduction through the AV node. ECG shows a longer P-R interval.
What is a second degree AV block? How many types are there? Name them.
An intermittent block in which tissue conducts some impulses but not others. Two types: Mobitz Type I and Mobitz Type II.
What is a Mobitz Type I block and what is seen on ECG?
A gradual lengthening of the P-R interval from one cycle to the next until the AV node fails to conduct and a ventricular depolarization is skipped. Typically, every 3rd or 4th beat is skipped.
What is a Mobitz Type II block and what is seen on ECG?
No change in P-R interval, but every nth beat is skipped. For example, if every 2nd beat was skipped it would be called a 2:1 block.
What is a Bundle Branch Block and what effect is seen on ECG?
A block of either the right or left bundle branches causes the impulse to spread through the myocardium via cell-cell gap junctions (slower), so the side that is blocked depolarizes more slowly and the QRS complex is lengthened.
What is a Third Degree AV block? What is seen on ECG?
A complete AV block in which no impulses travel through the affected area, causing the atria and ventricles to beat under the influence of their own pacemakers (called AV dissociation). ECG shows regularly spaced P waves but irregularly spaced QRS and T waves that have a low frequency (due to 20 beat/min Purkinje fiber pacing). P waves have no association with QRS and T waves.
