A generalized description of Wenckebach behavior with analysis of determinants of ventricular cycle-length variation during ambulatory electrocardiography

Reappraisal of the traditional Wenckebach phenomenon with a modified ladder diagram

Understanding of the traditional Wenckebach phenomenon is enhanced by using a modified ladder diagram where AV conduction in any cycle is represented by a slanted line in the AV bar together with similar AV conduction lines of all the preceding cycles. The diagram facilitates calculation of the duration of RR intervals (equal to the basic PP or sinus interval minus the PR or AV increment applied to this particular cycle) and the duration of the pause (equal to 2 × PP or sinus interval minus the sum of all the increments applied to the AV delay). The modified Wenckebach diagram should help students understand the mysterious clustering of QRS complexes or "paradoxical" increase of the ventricular rate that occurs during a Wenckebach sequence.

Woldemar Mobitz and His 1924 Classification of Second-Degree Atrioventricular Block

Woldemar Mobitz, an early 20th century German internist, analyzed arrhythmias by graphing the relationship of changing atrial rates and premature beats to AV conduction. Through an astute mathematical approach, he was able to classify second-degree atrioventricular block into 2 types, subsequently referred to as Mobitz type I (Wenckebach) and Mobitz type II (Hay). Type I AV block was most often due to digitalis and was reversible. There were no associated pathological findings. Type II AV block frequently progressed to complete AV block and was associated with seizures, death, and pathological findings.

Luigi Luciani and the earliest graphic demonstration of Wenckebach periodicity

Using an isolated frog heart preparation with ligatures around the atria, Luigi Luciani, an Italian physiologist working in 1873 in Carl Ludwig's famous laboratory in Leipzig, was the first to demonstrate cardiac group beating, which he named periodic rhythm. He attributed this to increased resistance to impulse propagation between the atria and the ventricle. Karel F. Wenckebach, in his 1899 landmark report of group beating in a patient in which he also used pulse tracings, credited Luciani with this discovery. Wenckebach referred to the phenomena as "Luciani periods." With the advent of electrocardiography in the early 20th century, this form of group beating became known as Wenckebach periodicity and then as Mobitz type I atrioventricular block. We reanalyzed Luciani's original paper and pulse tracings, and we show that periodic rhythm does indeed meet the criteria of second-degree atrioventricular block as established by Wenckebach. We also reviewed the career of Luciani, who was an important investigator, outstanding teacher and mentor, and distinguished leader of 19th-century physiology. We conclude that Wenckebach still deserves to have his name eponymously attached to this type of atrioventricular block because he was the first to unravel the complicated relationship between atrial and ventricular conduction.