Type 1 Second-degree AV block, also known as Mobitz I or Wenckebach periodicity, is almost always a disease of the AV node.
Wenckebach published a paper in 1906 on progressively lengthening PR intervals  that was later classified as Type I in Mobitz's 1924 paper.
Thus, both "Mobitz type I" and "Wenckebach block" refer to the same pattern and pathophysiology.

In Wenckebach's 1906 paper, his original observations were from increasing delay in contraction of the atria & ventricles that shortened after a brief pause and this was later observed on ECG after Einthoven's invention in 1901 that became the electrocardiogram (ECG).
Today, Mobitz I heart block is characterized by progressive prolongation of the PR interval on consecutive beats followed by a blocked P wave (i.e., a dropped QRS complex).
 After the dropped QRS complex, the PR interval resets and the cycle repeats.
This grouped beating was described as "Luciani periods" after Luigi Luciani's work in 1873.
The result is a lengthening of the R-R intervals as each subsequent P-wave reaches an increasingly refractory AV node until the impulse fails to conduct, which ultimately results in a blocked QRS complex.

One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the atrial rhythm has to be regular.
 If the atrial rhythm is not regular, there could be alternative explanations as to why certain P waves do not conduct to the ventricles.

This is almost always a benign condition for which no specific treatment is needed for the rhythm itself.
It can be seen in myocardial ischemia, propranolol use, digitalis use, rheumatic fever, and chronically in ischemic heart disease and other structural diseases (amyloidosis, mitral valve prolapse, aortic valve disease, and atrial septal defect).
In symptomatic cases, intravenous atropine or isoproterenol may transiently improve conduction.
Type 1 Second-degree AV block, also known as Mobitz I or Wenckebach periodicity, is almost always a disease of the AV node. Wenckebach published a paper in 1906 on progressively lengthening PR intervals  that was later classified as Type I in Mobitz's 1924 paper. Thus, both "Mobitz type I" and "Wenckebach block" refer to the same pattern and pathophysiology.
In Wenckebach's 1906 paper, his original observations were from increasing delay in contraction of the atria & ventricles that shortened after a brief pause and this was later observed on ECG after Einthoven's invention in 1901 that became the electrocardiogram (ECG). Today, Mobitz I heart block is characterized by progressive prolongation of the PR interval on consecutive beats followed by a blocked P wave (i.e., a dropped QRS complex).  After the dropped QRS complex, the PR interval resets and the cycle repeats. This grouped beating was described as "Luciani periods" after Luigi Luciani's work in 1873. The result is a lengthening of the R-R intervals as each subsequent P-wave reaches an increasingly refractory AV node until the impulse fails to conduct, which ultimately results in a blocked QRS complex.
One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the atrial rhythm has to be regular.  If the atrial rhythm is not regular, there could be alternative explanations as to why certain P waves do not conduct to the ventricles.
This is almost always a benign condition for which no specific treatment is needed for the rhythm itself. It can be seen in myocardial ischemia, propranolol use, digitalis use, rheumatic fever, and chronically in ischemic heart disease and other structural diseases (amyloidosis, mitral valve prolapse, aortic valve disease, and atrial septal defect). In symptomatic cases, intravenous atropine or isoproterenol may transiently improve conduction.
Second-degree atrioventricular block