What Is It?
The patient is a 76-year-old woman with history of arterial hypertension treated with angiotensin-converting enzyme inhibitors and calcium antagonists. She complained about palpitations, usually of short duration, more frequently during the night. The 12-lead ECG is shown in Figure 1. What is the electrocardiographic diagnosis?
Please turn the page to read the diagnosis.
Response to ECG Challenge
This 12-lead ECG shows sinus rhythm with first-degree atrioventricular block (PR=250 milliseconds) and with low-voltage R-wave complexes in leads I, aVL, and V6 without q waves that may be explained by partial left bundle-branch block. The presence of a small r wave in lead V1 may be caused by depolarization of the right ventricular wall. The echocardiogram confirmed normal left ventricular wall thickness.
The major abnormality of this 12-lead ECG is the P wave. Calipers and magnification of the ECG are needed to assess the duration and voltage of the P wave properly. The duration of the P wave is very long (185 milliseconds) and in the inferior leads (II, III, and aVF) depicts biphasic (±) morphology. These changes represent the current definition criteria of advanced interatrial block (A-IAB).1 The duration of the P wave must be measured in the frontal plane leads from the earliest detection of the P wave in any lead (onset) to the last one (offset) (Figure 1).
Figure 2 depicts the atrial activation in normal circumstances (Figure 2A) and in the case of partial block (Figure 2B) and A-IAB (Figure 2C).1 In the last, the stimulus is completely blocked in the Bachmann region, and activation of the left atrium (LA) occurs retrogradely through a zone located close to the coronary sinus. This explains the final negative component of the P wave in the inferior leads.
Atrial fibrosis is considered the anatomic substrate of A-IAB, which does not necessarily mean that the LA is enlarged. In fact, in this case, the LA measured by echocardiogram was only 37 mm, and the P-terminal force in lead V1 is normal (Morris index <40 mm·ms), which corresponds to a normal LA size. However, both processes (A-IAB and LA enlargement) can often be associated.
An ECG pattern, to be considered a true block, has to meet the following 3 criteria1,2: It must be experimentally reproducible; it must be transient; and it must be present in the absence of chamber enlargement or ischemia, as happens in this case.
It is currently accepted2 that patients with A-IAB, especially elderly patients with P-wave duration >140 milliseconds, can develop atrial fibrillation (AF) and atrial flutter in a short-term follow-up. In this case, Holter monitoring presents frequent runs of AF. One of them was captured in a 12-lead ECG (Figure 3). The association of a-IAB and AF has been called Bayés syndrome.2,3
Recent studies showed that A-IAB was associated with AF/atrial flutter and even with stroke in many different clinical scenarios, including a large cohort of the general population.2 The association with stroke, without documented AF, could open the door to the hypothesis of early anticoagulation. More definitive answers in this regard will be provided by prospective registries and ongoing randomized trials involving this population.
In summary, we presented a case that shows that careful evaluation of the surface P wave may result in valuable clinical information to predict the risk of AF and stroke.
Circulation is available at http://circ.ahajournals.org.
- © 2018 American Heart Association, Inc.
- Bayés de Luna A,
- Platonov P,
- García-Cosio F,
- Cygankiewicz I,
- Pastore C,
- Baranowski R,
- Bayés-Genís A,
- Guindo J,
- Viñolas X,
- García-Niebla J,
- Barbosa R,
- Stern S,
- Spodick D
- Baranchuk A
- Bacharova L,
- Wagner GS