ΔΙΑΤΑΡΑΧΕΣ ΕΝΔΟΚΟΙΛΙΑΚΗΣ ΑΓΩΓΙΜΟΤΗΤΑΣ ΔΗΜΗΤΡΙΟΣ Δ. ΜΑΝΩΛΑΤΟΣ Β ΚΑΡΔΙΟΛΟΓΙΚΗ ΚΛΙΝΙΚΗ ΕΡΓΑΣΤΗΡΙΟ ΗΛΕΚΤΡΟΦΥΣΙΟΛΟΓΙΑΣ Γ.Ν.Α. «ΕΥΑΓΓΕΛΙΣΜΟΣ»
Intraventricular conduction delay and Blocks Right Bundle Branch Block (RBBB) Left Bundle Branch Block (LBBB) Incomplete Blocks Nonspecific Intraventricular Conduction Delay (IVCD) Left anterior fascicular Block (LAFB) Left posterior fascicular Block (LPFB) Multifascicular Blocks Rate-Dependent Blocks
RBBB
Complete RBBB QRS duration 120msec rsr, rsr or rsr pattern in leads V1,V2 S wave in leads I,V6 40msec Normal R-wave peak time in leads V5,V6 but >50msec in V1
Causes Normal variant CAD (anterior MI) Pulmonary embolism Right ventricular dysfunction Congenital heart disease (eg ASD) Brugada syndrome
Clinical Significance In patients with no cardiac disease, RBBB is not associated with an increase of cardiac morbidity or mortality In the setting of cardiac disease (e.g CAD) the coexistence of RBBB worsens the prognosis
Anterior MI and RBBB
LBBB
Complete LBBB QRS duration 120msec Broad, notched or slurred R waves in leads I, avl, V5, V6 Small or absent initial r waves in leads V1,V2 followed by deep S waves Absent septal q waves in leads I, V5, V6 Prolonged R-wave peak time > 60msec in leads V5,V6 Stricter criteria for complete LBBB (Strauss) QRS duration 140 msec (men) and 130 msec (women) and mid-qrs notching or slurring in 2 contiguous leads (I, avl, V5, or V6)
LBBB
Causes CAD (new onset LBBB) Dilated Cardiomyopathy Aortic Stenosis Long-standing Arterial Hypertension Painful LBBB
Clinical Significance Is associated with higher risk of cardiovascular mortality and morbidity in persons with or without overt heart disease The asynchronous and prolonged ventricular contraction results in hemodynamic changes, structural remodeling, functional mitral valve dysfunction and the cardiac efficiency is reduced.
LBBB and STEMI
Nonspecific IVCD Wide QRS(>130 ms) but without typical features of LBBB or RBBB The presence of a nonspecific block is a poor prognostic factor in patients with or without heart disease and is associated with an increased risk of death
LAFB QRS duration < 120msec Frontal plane mean QRS axis between -45 and -90 degrees qr pattern in lead avl and rs patterns in leads II, III, and avf R-wave peak time 45 msec in leads avl
LAFB
LPFB QRS duration < 120msec Frontal plane mean QRS axis between +90 and +180 degrees rs pattern in leads I, avl with qr pattern in leads III, avf Exclusion of other factors causing right axis deviation (e.g lateral MI) Delayed intrinsicoid deflection in avf
LPFB
Multifascicular Blocks Conduction delay or block in more than one of the structural components of conduction system Bifascicular Block: - RBBB + LAFB (the most common) - RBBB + LAPB Trifascicular Block: - Delay in the RBB plus delay either in LBB or both LAF and LPF (Alternate RBBB and LBBB)
RBBB + LAFB RBBB plus left axis deviation beyond -45 degrees
RBBB + LAPB RBBB and mean QRS axis deviation to the right of 120 degrees
Alternate RBBB and LBBB
Rate-Dependent Blocks Acceleration(tachycardia)-dependent block Deceleration(bradycardia)-dependent block Ashman phenomen
Acceleration-dependent block It is manifest as either RBBB or LBBB, which occurs when the heart rate exceeds a critical value. At the cellular level, this aberration is the result of encroachment of the impulse on the relative refractory period (sometime during phase 3 of the action potential) of the preceding impulse, which results in slower conduction
Deceleration-dependent block Deceleration (bradycardia)-dependent block or conduction delay: It occurs when the heart rate falls below a critical level. It is thought to be due to abnormal phase 4 depolarization of cells so that activation occurs at reduced resting potentials. Deceleration-dependent block is less common than acceleration-dependent block and usually occurs in the setting of a significant conduction system disease
Ashman phenomenon The duration of the refractory period of the ventricular myocardium is a function primarily of the immediately preceding cycle length(s). If the preceding cycle length is long, the refractory period of the subsequent QRS complex is long and may conduct with BBB aberrancy (Ashman phenomenon) as part of a long cycle short cycle sequence, often when there is an abrupt prolongation of the immediately preceding cycle. The RBBB aberrancy is more common than LBBB aberrancy because the refractory period of the right bundle is usually longer than that of the left bundle at slower heart rates
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