Etymology: Willem Einthoven, Dutch physiologist, scientist, and Nobel laureate, 1860-1927; L, forma, pattern
a mathematical expression relating the voltages measured by electrocardiographic leads. The formula states that the sum of the voltages from lead I plus those from lead III minus those from lead II equals zero (I + III - II |m= 0). This formula is based on the principle that the sum of the voltages in any closed path equals zero. Because the positive and negative electrodes of lead II are reversed, the voltage from lead II is subtracted instead of added to the voltages from leads I and III. See also Einthoven's triangle.