Chapter 4 Flashcards
Is this NSR? If not, what is it?
First-degree AV block. Note the prolonged PR interval.
Is this NSR? If not, what is it?
Mobitz type I second-degree AV block (Wenckebach block). The PR intervals become progressively longer until one QRS complex is dropped.
Is this NSR? If not, what is it?
Mobitz type II second-degree AV block. On this EKG, each third P wave is not followed by a QRS complex (dropped beat).
Compare the following two, what types of block are they?
(A) Wenckebach block, with progressive lengthening of the PR interval. (B) Mobitz type II block, in which the PR interval is constant.
Is this NSR? If not, what is it?
Mobitz type II
What are some possible sites for 3rd degree block?
Is this NSR? If not, what is it?
Third-degree AV block. The P waves appear at regular intervals, as do the QRS complexes, but they have nothing to do with one another. The QRS complexes are wide, implying a ventricular origin.
Compare the following two, what are they?
(A) The third beat is a PVC, occurring before the next anticipated normal beat. (B) The third ventricular complex occurs late, after a prolonged pause. This is a ventricular escape beat.
Is this NSR? If not, what is it?
Right bundle branch block. The QRS complex in lead V1 shows the classic wide RSR′configuration. Note, too, the S waves in V5 and V6.
Is this NSR? If not, what is it?
Left bundle branch block.
In bundle branch block, the repolarization sequence is affected. Take an observation of the following ECG.
ST segment depression and T wave inversion in lead V6 in a patient with left bundle branch block. Just like repolarization abnormalities that occur with ventricular hypertrophy
What’s “critical rate”?
In some individuals, bundle branch block only appears above a certain rate, called the critical rate.
An example of critical rate (lead V2). As the heart accelerates, the pattern of right bundle branch block appears.
Criteria for Right bundle branch block
- QRS>0.12 sec
- RSR’ in V1 and V2 (rabbit ears) with ST depression and T inversion
- Reciprocal changes in V5, V6, I and aVL
Criteria for Left bundle branch block
- QRS>0.12 sec
- Broad or notched R wave with prolonged upstroke in V5, V6, I, and aVL, with ST depression and T inversion
- Reciprocal changes in V1 and V2
- Left axis deviation may be present
What type of block is this?
Left anterior hemiblock. Current flow down the left anterior fascicle is blocked; hence, all the current must pass down the posterior fascicle. The resultant axis is redirected upward and leftward (left axis deviation).
What type of block is this?
Left posterior hemiblock. Current flow down the left posterior fascicle is blocked; hence, all the current must pass down the right anterior fascicle. The resultant axis is redirected downward and rightward (right axis deviation).
Is hemiblock present in the following ECG? If so, what type is it?
Left axis deviation greater than –30° indicates the presence of left anterior hemiblock.
Identify this block
Right bundle branch block with left anterior hemiblock. Wide QRS, rabbit ears in V1 and V2, and left axis deviation
Identify the following ECG
Incomplete right bundle branch block; the QRS complex is not widened, but note the classic rabbit ears configuration in V1.
Identify the following ECG
a. 1st degree AV block (PR>0.20sec);
b. Right bundle branch block (Wide QRS with rabbit ears in V1-V4)
c. left anterior hemiblock (left axis deviation)
FYI, an example of pacemaker ECG
EKG from a patient with a ventricular pacemaker.
FYI, an example of pacemaker ECG
EKG from a patient with an atrial pacemaker.
FYI, an example of pacemaker ECG
EKG from a patient with a sequential pacemaker.
Identify this ECG
1st degree AV block, and the rabbit ears of right bundle branch block
Bonus question! What do you see here?
Pacemaker failed to capturethe heart, the pacemaker spikes have no relation to either P nor QRS
