Making sense of common Holter ECG findings

There are some findings on a Holter monitor recording you expect, for example atrial fibrillation or premature ventricular complexes (PVCs). How do you report on it in clear and precise language? Our expert highlights common findings and reviews terms you should use to describe them.

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When you analyze a Holter recording, there are some arrhythmias that you'll encounter commonly. Let's take a look at some of those now. The most common sustained arrhythmia we see on Holter recordings is atrial fibrillation. It's identified by its irregularly irregular character, and by the absence of any discernible repeating P wave activity. In persistent atrial fibrillation Holter monitoring can provide valuable information about ventricular rate.

For instance, when we want to assess the effectiveness of rate controlling medications such as beta blockers. Atrial fibrillation can also be paroxysmal. By convention, in accordance with published guidelines, we only label an episode as a paroxysm of atrial fibrillation on Holter monitoring if it has lasted for 30 seconds or longer. It's important to report any such episodes of AF that you see because paroxysmal atrial fibrillation is associated with an increased risk of stroke, even when it is asymptomatic.

What terminology should we use for episodes that look like AF, but that are shorter than 30 seconds? Well, there's no consensus on this. One option is to refer to such an episode as an atrial arrhythmia without P waves and with irregular ventricular response lasting less than 30 seconds. This description is a little cumbersome, but it conveys the key features of the event without applying the clinical label of atrial fibrillation.

Premature ventricular complexes or contractions abbreviated to PVCs are also sometimes called ventricular ectopic beats are another common finding on Holter recordings. They're identified as broad QRS complexes, lasting more than 120 milliseconds and their abnormal morphology which varies according to their points of origin within the ventricles. They occur prematurely, that is earlier than the next normal beat would have occurred, and are usually followed by a compensatory pause.

PVCs can be described as unifocal, when they all originate from the same location and share the same morphology. They can also be labeled multi-focal If they originate from different locations and therefore their morphology varies. You need to report any PVCs that are associated with symptoms such as palpitations. Therefore, it's important to check the patient's symptoms diary to see whether any of the PVCs correspond to events that the patient has recorded.

You also need to report the number and frequency of palpitations whether symptomatic or not, I recommend reporting the total number of PVCs during the recordings expressed that value as a percentage of the total heartbeat seen. I also report the average frequency of PVCs per hour. It's recognized that patients with very frequent PVCs such as 20,000 or more during a 24-hour Holter recording, run a risk of PVC induced cardiomyopathy.

For this reason, you always need to report on overall PVC numbers whether they're symptomatic or not. ventricular tachycardia, or regular wide complex tachycardia is another relatively common arrhythmia on Holter monitoring, particularly as a brief incidental finding. However, it can be associated with serious symptoms such as syncope, and may indicate a risk of sudden cardiac death. He must therefore always report any episodes of VT that you see whether they are symptomatic or not. We often categorize episodes of VT as sustained or non-sustained.

If an episode lasts more than 30 seconds, it's sustained less than 30 seconds is non-sustained. VT can also be described as monomorphic, when all the QRS complexes have the same shape, it can be labeled polymorphic when the shape changes from one beat to the next. The final common finding that I'd like to highlight are pauses. These can be caused by sinus arrest or sinoatrial block, in which case P waves are absent, or due to atrioventricular block, in which case you will see evidence of atrial activity but no ventricular activity.

Either way, pauses causes cessation of ventricular activity for a period of time and could often be associated with dizziness and syncope. As such, it's important to comment on the presence of any pauses that you see, and to record whether they are symptomatic and how long they lasted. It's also important to try and identify whether the pauses were due to atrioventricular block by looking for any evidence of background atrial activity. All of these factors will help to determine whether or not a pacemaker may be indicated. In summary, there are several arrhythmias that you will commonly encounter during the analysis of Holter recordings. It's important to include details of these in your reports not only because they may be the cause of the patient's symptoms but also because they can carry risks and clinical implications for the patient even when asymptomatic.