In its classic definition, by FranÃ§ois-Louis Ganshof (1944), feudalism describes a set of reciprocal legal and military obligations among the warrior nobility revolving around the three key concepts of lords, vassals and fiefs.
The exact cause of intracardiac echogenic foci remains unclear; however, they appear to be caused by small deposits of calcium in the papillary muscle of the fetal heart.
Intracardiac ECG recordings during inappropriate sinus tachycardia. Shown are surface leads II, aVF and V1, and intracardiac recordings from the electrophysiologic diagnostic catheters positioned in the high right atrium, His-bundle region, coronary sinus and right ventricular apex.