Submitted by Dr A Röschl on Mon, 12/11/2023 - 01:07
Why is this a high-grade AV block? If at least 3 P-waves are not conduced and there is normal AV conduction before and after, this can be considered a high-grade AV block. In this Holter strip, P1, P2 and all P-waves from P6 onwards are conducted, albeit with a prolonged PR interval (first-degree AV block). P3, P4, P5 are not conducted. A junctional escape beat is seen before P5. P5 can also not be conducted because the specific conduction system is still refractory at this time due to the junctional escape beat.
Submitted by Dr A Röschl on Mon, 12/11/2023 - 00:43
Atrial flutter and atrial fibrillation are two different cardiac arrhythmias, but occur frequently side by side in the same patient. Here is an example of how atrial flutter degenerataes into atrial fibrillation. The initially ordered atrial activity (left in the picture) with 2 flutter waves/1 QRS complex changes into irregular atrial activity (right in the picture) and the RR intervals become completely irregular.
Submitted by Dr A Röschl on Thu, 08/10/2023 - 01:07
Here we see the EKG of a 15-year-old girl. The rhythm is irregular, with the heart rate fluctuating between approximately 60 and 90 beats per minute. All P waves are identical, and the PR interval is always constant. Therefore, a sinus arrhythmia is present. In this case, it is a respiratory sinus arrhythmia, which is commonly found in younger individuals. The heart rate increases reflexively during inspiration and decreases during exspiration. This physiological sinus arrhythmia is usually no longer present in older individuals.
Submitted by Dr A Röschl on Wed, 08/02/2023 - 02:35
We are observing EKG strip 1 in a Holter EKG recording; what can be said about it? There is a sinus rhythm with a normal PQ interval. After 3 sinus beats, a 2:1 AV block develops. When 2:1 AV block occurs, we should not refer to this as Wenckebach (Mobitz I) or Mobitz II, but rather as a high-grade AV block (other forms include: 3:1, 4:1, 5:1, etc.). The 2:1 block can be intranodally localized and behave benignly like a Wenckebach block typically does. However, it could also be infranodally localized with a potentially serious prognosis.
This two-lead rhythm strip shows a normal sinus rhythm at about 63 bpm. The P waves are regular. After the sixth P-QRS, there is a non-conducted P wave. The normal rhythm then resumes. The two most common reasons for a non-conducted P wave in the midst of a normal sinus rhythm are 1) non-conducted PAC, and 2) Wenckebach conduction. The first is easy to rule out. The non-conducted P wave is not premature, so it is not a PAC. The second one is a little harder when we only have a short strip to look at. We are conditioned to look for progressively-prolonging PR intervals until a QRS is "dropped". In this case, the progression is in very tiny increments that are hard to see unless you zoom in and measure. But they ARE progressively prolonging. An easy hack: measure the last PRI before the dropped beat and the first one after the pause. You will see that the cycle ends on a longer PRI (about .28 seconds) and the new cycle starts up with a PR interval of about .20 seconds. Fortunately, this conduction ratio will have very little effect on the patient's heart rate.
This strip shows a supraventricular tachycardia, rate 196 bpm, after adenosine was administered to the patient. The PSVT breaks, and an irregular rhythm composed of sinus beats and premature atrial contractions ensues. This is common after medical cardioversion. The patient later settled into a normal sinus rhythm. The abrupt change from a fast, regular rhythm to a slower, irregular rhythm is evidence that the tachycardia was due to a reentrant circuit, and not sinus tachycardia.
This is a good strip to demonstrate the change in the appearance of a T wave when a premature P wave occurs on the preceding T wave. The PACs found the atria ready to depolarize and produced a P wave that landed on top of the preceding T wave, making it appear taller than the others. The PACs also reset the sinus node, causing a slight delay before the next sinus discharge. The PACs occurred while the ventricles were still refractory, so no QRS complexes followed.
This rhythm strip was obtained from a man who was suffering an acute inferior wall M.I. There are ST elevation and hyperacute T waves. The rhythm is SINUS ARRHYTHMIA WITH SECOND-DEGREE AV BLOCK, TYPE II. There is also first-degree AV block.
There are more P waves than QRS complexes, with a 3:2 ratio. The atrial rate varies between 55 -68 beats per minute. The sinus rate speeds slightly after the dropped QRS in each group. The ventricular rate is about 40 bpm, with grouped beating. (Regularly irregular.)
The PR intervals are steady at 226 ms (slightly prolonged).
Multifocal atrial tachycardia is diagosed when an irregular atrial rhythym is over 100 beats per minute. It is caused by multiple competing atrial pacemaker sites. There need to be at least three different P wave morphologies to diagnose MAT. The PR intervals may vary also. It is nearly always seen in very sick patients, often with chronic obstructive pulmonary disease and/or respiratory failure.
