Double sequential external defibrillation (DSED) can be used in ventricular fibrillation (VF) which remains refractory to conventional ACLS protocols. It involves utilizing two defibrillators to rapidly deliver two shocks in succession to increase energy sent to the myocardium with multiple vectors at a lower shock impedance. This technique has also…
The absolute and relative refractory periods refer to the intervals during which the cardiac cells are either entirely or partially unresponsive to further stimulation, respectively. The refractory periods are crucial in regulating the timing and rhythm of the heart’s contractions. Suppose a stimulus causes the transmembrane potential (TMP) to reach…
In order for the heart muscle to actually contract, the physiological process of excitation-contraction coupling must occur via an action potential propagated through the myocardium. Normally, these muscle cells have a resting transmembrane potential (TMP) around -90 mV (more negative intracellularly than extracellularly). This gradient is created and changed by…
With the number of patients receiving permanent pacemakers (PPMs) and implantable cardioverter-defibrillators (ICDs) increasing each year, we’ll see more of these devices in our respective clinical settings. With this post, I’ll try to simplify pacemaker nomenclature and discuss some of the considerations surrounding magnets and device settings.