This chapter will actually be a continuation of the previous one. Why did we elect to separate out two aspects of the same topic? We split them up because, even though they are both variations on a theme, they are different in many respects, especially in recognition. In particular, they are very lead dependent and the P waves are sometimes unrecognizable in lead II. Focal atrial tachycardias (focal ATs) with blocks are also often misdiagnosed as atrial flutters or other supraventricular tachycardias, and these arrhythmias have totally different treatment strategies. Correctly identifying a focal AT with block may save your patient’s life by making you think of the various precipitating factors that cause it to develop.
Traditionally, focal AT with block was known as paroxysmal atrial tachycardia with block. This terminology is still very much in use today by many clinicians. Why has the term stuck where other nomenclature has changed? We feel that it’s because the term PAT with block rolls off the tongue a bit smoother than focal AT with block. Get used to hearing it both ways and understand that it refers to the same clinical entity. However, whenever you hear either term, think about the possibility that the patient is digoxin toxic. This is a classic arrhythmia that is almost exclusively found in this patient population. For this reason, it is critical for every clinician, beginner or advanced, to recognize it.
In this chapter, we will not discuss the criteria for a focal AT. If you would like to review these criteria, refer to the previous chapter. In this chapter, we will concentrate on the block and on arrhythmia recognition.