Second degree AV block
Second degree AV block
Classification & external resources
| ICD-10 |
I44.1 |
| ICD-9 |
426.12, 426.13 |
| DiseasesDB |
10477 |
| eMedicine |
emerg/234 |
Second degree AV block is a disease of the electrical conduction system of the heart. It refers to a conduction block between the atria and ventricles.
The presence of second degree AV block is diagnosed when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction.
Types
There are two distinct types of second degree AV block, called Type 1 and Type 2. The distinction is made between them because type 1 second degree heart block is considered a more benign entity than type 2 second degree heart block.
Type 1 (Mobitz I/Wenckebach)
Type 1 Second degree AV block, also known as Mobitz I or Wenckebach periodicity, is almost always a disease of the AV node.
Mobitz I heart block is characterized by progressive prolongation of the PR interval on the electrocardiogram (EKG) 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.
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.
Type 2 (Mobitz II)
Type 2 Second degree AV block, also known as Mobitz II is almost always a disease of the distal conduction system (His-Purkinje System). Although the terms infranodal block or infrahisian block are often applied to this disorder, they are not synonymous with it. Infranodal block and infrahisian block are terms which refer to the anatomic location of the block, whereas Mobitz II refers to an electrocardiographic pattern associated with block at these levels.
Mobitz II heart block is characterized on a surface ECG by intermittently nonconducted P waves not preceded by PR prolongation and not followed by PR shortening. The medical significance of this type of AV block is that it may progress rapidly to complete heart block, in which no escape rhythm may emerge. In this case, the person may experience a Stokes-Adams attack, cardiac arrest, or Sudden Cardiac Death. The definitive treatment for this form of AV Block is an implanted pacemaker.
Symptoms
Most people with Wenckebach (Type I Mobitz) do not show symptoms. However, those that do usually display one or more of the following:
- Light-headedness
- Dizziness
- Syncope (Fainting)
See also
External links
- synd/2824 at Who Named It
- http://www.youtube.com/watch?v=GVxJJ2DBPiQ - AV Block Parody Video by the University of Alberta
- Emergency Cardiovascular Medicine - eMedicine article on 2nd Degree Heart Block
|
Circulatory system pathology (I, 390-459) |
| Hypertension |
Hypertensive heart disease - Hypertensive nephropathy - Secondary hypertension (Renovascular hypertension) |
| Ischaemic heart disease |
Angina pectoris (Prinzmetal's angina) - Myocardial infarction - Dressler's syndrome |
| Pulmonary circulation |
Pulmonary embolism - Cor pulmonale |
| Pericardium |
Pericarditis - Pericardial effusion - Cardiac tamponade |
| Endocardium/heart valves |
Endocarditis - mitral valves (regurgitation, prolapse, stenosis) - aortic valves (stenosis, insufficiency) - pulmonary valves (stenosis, insufficiency) - tricuspid valves (stenosis, insufficiency) |
| Myocardium |
Myocarditis - Cardiomyopathy (Dilated cardiomyopathy, Hypertrophic cardiomyopathy, Loeffler endocarditis, Restrictive cardiomyopathy) - Arrhythmogenic right ventricular dysplasia |
Electrical conduction system
of the heart |
Heart block: AV block (First degree, Second degree, Third degree) - Bundle branch block (Left, Right) - Bifascicular block - Trifascicular block
Pre-excitation syndrome (Wolff-Parkinson-White, Lown-Ganong-Levine) - Long QT syndrome - Adams-Stokes syndrome - Cardiac arrest - Sudden cardiac death
Arrhythmia: Paroxysmal tachycardia (Supraventricular, AV nodal reentrant, Ventricular) - Atrial flutter - Atrial fibrillation - Ventricular fibrillation - Premature contraction (Atrial, Ventricular) - Ectopic pacemaker - Sick sinus syndrome |
| Other heart conditions |
Heart failure - Cardiovascular disease - Cardiomegaly - Ventricular hypertrophy (Left, Right) |
| Cerebrovascular diseases |
Intracranial hemorrhage/cerebral hemorrhage: Extra-axial hemorrhage (Epidural hemorrhage, Subdural hemorrhage, Subarachnoid hemorrhage)
Intra-axial hematoma (Intraventricular hemorrhages, Intraparenchymal hemorrhage) - Anterior spinal artery syndrome - Binswanger's disease - Moyamoya disease |
Arteries, arterioles
and capillaries |
Atherosclerosis (Renal artery stenosis) - Aortic dissection/Aortic aneurysm (Abdominal aortic aneurysm) - Aneurysm - Raynaud's phenomenon/Raynaud's disease - Buerger's disease - Vasculitis/Arteritis (Aortitis) - Intermittent claudication - Arteriovenous fistula - Hereditary hemorrhagic telangiectasia - Spider angioma |
Veins, lymphatic vessels
and lymph nodes |
Thrombosis/Phlebitis/Thrombophlebitis (Deep vein thrombosis, May-Thurner syndrome, Portal vein thrombosis, Venous thrombosis, Budd-Chiari syndrome, Renal vein thrombosis, Paget-Schroetter disease) - Varicose veins / Portacaval anastomosis (Hemorrhoid, Esophageal varices, Varicocele, Gastric varices, Caput medusae) - Superior vena cava syndrome - Lymph (Lymphadenitis, Lymphedema, Lymphangitis) |
| Other |
Hypotension (Orthostatic hypotension) |
| See also congenital (Q20-Q28, 745-747) |
|
Top