<Ul> <Li> Mobitz I is characterized by a reversible block of the AV node . When the AV node is severely blocked, it fails to conduct an impulse . Mobitz I is a progressive failure . Some patients are asymptomatic; those who have symptoms respond to treatment effectively . There is low risk of the AV block leading to heart attack . Mobitz II is characterized by a failure of the His - Purkinje cells resulting in the lack of a supra ventricular impulse . These cardiac His - Purkinje cells are responsible for the rapid propagation in the heart . Mobitz II is caused by a sudden and unexpected failure of the His - Purkinje cells . The risks and possible effects of Mobitz II are much more severe than Mobitz I in that it can lead to severe heart attack . </Li> </Ul> <Li> Mobitz I is characterized by a reversible block of the AV node . When the AV node is severely blocked, it fails to conduct an impulse . Mobitz I is a progressive failure . Some patients are asymptomatic; those who have symptoms respond to treatment effectively . There is low risk of the AV block leading to heart attack . Mobitz II is characterized by a failure of the His - Purkinje cells resulting in the lack of a supra ventricular impulse . These cardiac His - Purkinje cells are responsible for the rapid propagation in the heart . Mobitz II is caused by a sudden and unexpected failure of the His - Purkinje cells . The risks and possible effects of Mobitz II are much more severe than Mobitz I in that it can lead to severe heart attack . </Li> <Li> Third - degree atrioventricular block - No association between P waves and QRS complexes . The heart's electrical signals are slowed to a complete halt . This means that none of the signals reach either the upper or lower chambers causing a complete blockage of the ventricles and can result in cardiac arrest . Third - degree atrioventricular block is the most severe of the types of heart ventricle blockages . Persons suffering from symptoms of third - degree heart block need emergency treatment including but not limited to a pacemaker . </Li> <P> In order to differentiate between the different degrees of the atrioventricular block (AV block), the First - Degree AV block occurs when an electrocardiogram (ECG) reads a PR interval that is more than 200 msec . This degree is typically asymptomatic and is only found through an ECG reading . Second - Degree AV block, although typically asymptomatic, has early signs that can be detected or are noticeable such as irregular heartbeat or a syncope . A Third - Degree AV block, has noticeable symptoms that present itself as more urgent such as: dizziness, fatigue, chest pain, pre syncope, or syncope . </P>

If there is a complete block between the sa node and the av node
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