John Hay and the earliest description of type II second-degree atrioventricular block

Abstract

I t is universally acknowledged that in 1899, Wenckebach first described type I second-degree atrioventricular (AV) block in humans.1 The centennial of this clinical landmark was recently publicized.2 Although Wenckebach called this process “Luciani periods” after the Italian physiologist who observed this phenomenon in the frog heart in 1872, this pattern is now widely known as the Wenckebach phenomenon or periodicity.3 A number of workers have attributed the discovery of both types I and II second-degree AV block solely to Wenckebach.4–6 As a result, types I and II second-degree AV block is sometimes incorrectly designated as Wenckebach type I and type II block.7 Others have claimed that type II block was described independently by Wenckebach and Hay both in 1906.8–13 There are also rare, unfounded claims by compatriots of John Hay that it was he who discovered both types I and II second-degree AV block.14 It was actually John Hay who discovered the form of second-degree AV block currently known as type II block15 (Figure 1). Information about John Hay can be found in the recent article by Upshaw and Silverman.16 Hay’s original contribution was cited by Thomas Lewis in his 1925 book17 and by Schamroth in his 1971 book.18 Yet, Burch in his monograph on the history of electrocardiography merely stated that “incomplete heart block was studied extensively in man by MacKenzie, Wenckebach and Hay, by means of the polygraph.” without citing Hay’s work nor his 1906 article.19 Katz and Pick of the famed Chicago School of Electrocardiography did not mention Hay’s contribution to the understanding of second-degreeAV block in their classic 1956 book.20 In fact, the Chicago electrocardiographers indicated in other publications that Wenckebach and Hay described type II seconddegree AV block independently.12 In 1906 John Hay from Liverpool, England, published a case report in the Lancet describing a new form of second-degree AV block distinct from that previously reported by Wenckebach.15 Hay documented his findings without the benefit of the electrocardiograph, which was introduced clinically years later. Hay analyzed simultaneous tracings from the radial (arterial) and jugular (venous) pulses in a 65year-old patient with lightheadedness. The recordings in Figures 2 and 3 were described as showing a-c intervals (as a measure of AV conduction corresponding to the PR interval of the electrocardiogram) essentially normal and constant in duration regardless of the number of missing ventricular beats. Figure 2 clearly shows what is now considered type II seconddegree AV block with constant a-c intervals before and after a single-blocked atrial impulse (“a” wave not followed by “c” deflection) in a sequence of at least 4:3 AV block. Hay correctly emphasized that no similar case had been recorded in the literature and dismissed the type of AV block described by Wenckebach because the a-c interval failed to vary. The purist will argue that Figure 2 cannot be interpreted as type II second-degree AV block because there are no PR intervals and the behavior of the a-c intervals cannot be determined accurately. However, the diagnosis of type II block can be made with certainty by looking at the heart rate in the arterial recording on top of Figure 2. Note that the duration of the pause between the fourth and fifth arterial beats is exactly double that of the cycle before the block (between the third and fourth arterial beats). This indicates that AV conduction before and after the blocked impulse was constant. This constitutes the hallmark of type II block when there are at least 2 consecutively conducted P waves and only a single nonconducted impulse. A vagal effect on the AV node can be ruled out because the cycle before the block (between the third and From the Broward General Hospital, Fort Lauderdale, Florida; and the University of Bonn, Bonn, Germany. Dr. Barold’s address is: 6237 NW 21st Court, Boca Raton, Florida 33496. E-mail: ssbarold@aol.com. Manuscript received November 24, 2000; revised manuscript received and accepted January17, 2001. FIGURE 1. John Hay 1873 to 1959. (Courtesy of Arthur Hollman MD., London England).