On first looking into auriculo-ventricular asynchrony.

Walter Gaskell's demonstration in 1882 that it was possible to block the passage of contraction from auricle to ventricle in the frog heart by means of a clamp spurred Joseph Erlanger (1906) to prevent, by similar means, impulse conduction through the bundle of (Wilhelm) His jun. (1893) in the mammalian heart. With a miniaturized polygraph to record the jugular and arterial pulsation, James Mackenzie (1902) displayed various grades of heart block in the human heart. His results were confirmed by Thomas Lewis using Willem Einthoven's (1903) ECG in 1911. But without instrumental help, Robert Spittal (1804-1852) recounted a case of reversible auriculo-ventricular block in 1830.