Dr.ahmed Taha Hussein M.Sc. Cardiology Zagzig university
Those who suffer from frequent and strong faints without any manifest cause die suddenly“ Hippocrates (460 - 375 BC) Micheal Bernhard Valentini (1713)
Low density Tadpole shaped 2 X 5 Na channels mm High density lies beneath the RA L-type Ca endocardium at the channel apex of the triangle of Koch. blood supply to the AVN predominantly comes from a branch of the right coronary artery in 85% to 90% of patients and from the circumflex artery in 10% to 15%
connects with the distal part of the compact AVN, perforates the central fibrous body, and penetrates the membranous septum, along the crest of the left side of the interventricular septum, for 1 to 2 cm and then divides into the right and left bundle branches. dual blood supply from branches LAD , PDA .
The main function is to delay conduction of impulse propagated from atrium to ventricle allowing diastolic time enough for ventricular filling and atrial contraction. limit the number of impulses conducted from the atria to the ventricles. -ve dromotropic response: activating IK(Ach,Ado) +ve dromotropic response : activating L-type Ca channels
AV conduction is represented on the surface ECG by PR PR interval(120- interval 200 ms). PR= (ARA –Ahiss) +(A-H) .
can be defined as transient or permanent delay or interruption in the transmission of an impulse from the atria to the ventricles caused by an anatomical or functional impairment in the conduction system.
LEV’S DISEASE LENEGRE’S DISEASE Fibrocalcification of Primary scelerosing cardiac cytoskeleton disease of the MAC , Aortic Scleorsis conductive system. In involvement of the cytoskeleton
For diagnostic and prognostic value …. AV-block is divided into nodal block Infranodal block . Diagnosis achieved by : ECG ( PR interval , P-R wave relation , QRS duration) Autonomic modulation exercise testing . EP Study .
Incomplete AV block includes a. first-degree AV block b. second degree AV block c. advanced AV block Complete AV block,also known as third degree AV block
Proximal to, in, or distal to the His bundle in the atrium or AV node All degrees of AV block may be intermittent or persistent
PR interval is prolonged 0.21- 0.40 seconds, but no R-R interval change.
First-degree atrioventricular block caused by intranodalconduction delay
First-degree atrioventricular block secondary to His-Purkinjesystem (HPS) disease
First-degree atrioventricular block caused by intraatrialconduction delay
There is intermittent failure of the supraventricular impulse to be conducted to the ventricles Some of the P waves are not followed by a QRS complex.The conduction ratio (P/QRS ratio) may be set at 2:1,3:1,3:2,4:3,and so forth
Type I also is called Wenckebach phenomenon or Mobitz type I and represents the more common type Type II is also called Mobitz type II
typical periodicity Progressive lengthening of the PR interval until a P wave is blocked 2.Progressive shortening of the RR interval until a P wave is blocked 3.RR interval containing the blocked P wave is shorter than the sum of two PP intervals
Infra-Hisian second-degree Wenckebach trioventricular (AV) block. Atrialpacing in a patient with a normal prolonged atrial–His bundle interval(AH) but prolonged His bundle–ventricular interval (HV) and rightbundle branch block (RBBB)
ECG findings 1.Intermittent blocked P waves 2.PR intervals may be normal or prolonged,but they remain constant 3.When the AV conduction ratio is 2:1,it is often impossible to determine whether the second-degree AV block is type I or II 4. A long rhythm strip may help
When the AV conduction ratio is 3:1 or higher,the rhythm is called advanced AV blocked A comparison of the PR intervals of the occasional captured complexes may provide a clue If the PR interval varies and its duration is inversely related to the interval between the P wave and its preceding R wave (RP), type I block is likely A constant PR interval in all captured complexes suggests type II block
There is complete failure of the supraventricular impulses to reach the ventricles The atrial and ventricular activities are independent of each other. Ventriculophasic Sinus Arrhythmia : intermittent differences in the P-P intervals based on their relationship to the QRS complex.
In patients with sinus rhythm and complete AV block, the PP and RR intervals are regular, but the P waves bear no constant relation to the QRS complexes
Sinus rhythm with normal atrioventricular (AV) conduction. Frequentpremature atrial complexes (PACs; A′) are observed in a bigeminal pattern
HB ectopy that fail to conduct to both Atria and ventricle . Appear like type 2 AV block . ECG clues : (1) abrupt, unexplained prolongation of the PR interval . (2) the presence of apparent Mobitz type II block in the presence of a normal QRS (3) the presence of types 1 and 2 AV block in the same tracing (4) the presence of manifest junctional extrasystoles elsewhere in the tracing.
Atrial tachycardia with subsidiary escape focus from AV junction or ventricle . Accelerated idioventricular rhythm . Vtach.
Echo beat : can manifest as “group beating” and be misdiagnosed as Wenckebach block. ECG clues: PR interval , P-wave morphology. Atrial tachyarrhythmia with variable AV conduction .
Pacing is the mainstay of treatment for symptomatic AV block . Identifying transient or reversible causes for AV conduction disturbances is the first step in management. Withdrawal of any offending drugs, correction of any electrolyte abnormalities, or treatment of any infectious processes should be considered prior to permanent pacing therapy.