“The first is an ECG, single lead, called a rhythm strip, which shows a common and generally benign arrhythmia called second degree heart block, Mobitz Type I, also called Wenckebach. The interval between the P wave (atrial contraction) and the QRS (ventricular contraction) progressively increases till a QRS is dropped. The second is a three-lead ECG showing an acute inferior myocardial infarction, aka a heart attack.”
Carl writes: When you stop to reflect on electrocardiograms, it is remarkable that we can peer within the heart simply by picking up tiny changes in voltage on the skin. The fact that muscles such as the heart use electricity to drive their contractions was inconceivable in the 1600s. Natural philosophers believed muscles might be inflated by “animal spirits,” but the idea that the same power in a lightning bolt was at work in our hearts every second of our lives would have seemed absurd. Jan Swammerdam, a Dutch anatomist, tried to persuade his contemporaries in the 1660s that animal spirits did not drive the heart–he showed that a severed muscle twitched if he touched its nerve endings with the blade of a scalpel–but it would take well over a century for scientists to accept that our lives depend on a rhythm of sparks.