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The electro cardiographic patterns of type I and type II second-degree atrioventricular (AV) block during sinus rhythm describe the behaviour of the PR intervals (in sinus rhythm) in sequences (with at least two consecutive conducted PR intervals) where a single P wave fails to conduct to the ventricles.1 Unfortunately, the diagnosis of Mobitz type II second-degree AV block continues to be an important clinical problem because the standard definitions of second-degree AV block are often misinterpreted.1 The literature is replete with cases of type I second-degree AV block labelled as type II block, and similar errors have crept into the sports literature with claims that narrow QRS type II AV block can also occur in otherwise healthy young athletes2,–,7 and less commonly after exercise in the form of vasovagal syncope (table 1).8 These reports of type II block in athletes provided either no ECG or misdiagnosed ones. Furthermore, when stated, the definitions of type II block were inappropriate. The occurrence of type II block in young athletes is counterintuitive because it would imply serious disease of the His–Purkinje system and an absolute indication for a permanent pacemaker regardless of symptoms.1 We were unable to find a single case of precisely documented type II block in young athletes. Yet, many review articles continue to list type II block as one of the manifestations of the athlete's heart.9,–,12 Accurate diagnosis of type II block in athletes is critical and will affect treatment recommendations. Based on these considerations, there is a need for reviewing the pitfalls surrounding the diagnosis of type II block with emphasis on how errors can be avoided by strict adherence to definitions.
Type I second-degree atrioventricular block
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