Bundle branch blocks by Dr Sujith Chadala
- 1. Intraventricular Conduction Blocks Dr. Sujith Chadala (MD)(Gen. Medicine) Upgraded Dept. Of Medicine Osmania General Hospital
- 2. Intraventricular conduction blocks • Right Bundle Branch Block (RBBB) • Left Bundle Branch Block (LBBB) • Incomplete Blocks • Non-specific Intraventricular Conduction Delay • Left Anterior Fasicular Block (LAFB) • Left Posterior Fasicular Block (LPFB)
- 4. Right Bundle Branch Block (RBBB) • Impulses travel through myocardium of left ventricle to right ventricle and depolarise right ventricle. • Conduction through myocardium is slower than that of Bundle of His , QRS complex is seen to be widened.
- 5. Blockage in the Right Bundle Branch (red), left ventricle is excited in time (purple), while excitation of right ventricle takes detour via left bundle branch (blue arrows).
- 6. Criteria of RBBB • QRS duration ≥ 120ms. • Wide S wave in I ,aVL, V5 &V6 • rSR’ pattern or notched R wave in V1. • Appropriate discordance: the ST segments and T waves always go in the opposite direction to the main vector of the QRS complex.
- 7. Wide S wave in lead I
- 8. Typical rSR’ pattern (‘M’-shaped QRS) in V1
- 9. Causes • Normal variant in 0.2% of adults (prevalence increases with age). • CAD Acute anterior MI (occlusion of proximal LAD). • Chronic Corpulmonale. • Acute pulmonary embolism. • Congenital heart disease e.g. Atrial Septal Defect. • Brugada syndrome.
- 10. Clinical significance • Concordant T wave with Bundle Branch Block may suggest ischemia or infarction. • RBBB in the setting of an acute MI worsens the prognosis , indicates proximal Left Anterior Descending artery occlusion ( infarction of Interventricular septum ). • Both LBBB and qRBBB signify large area of infarction ,hence associated with high risk.
- 11. Evolved extensive anterior wall MI QR waves in V1-4 (qRBBB of lead V1) with loss of normal S waves J point and convex upwards ST elevation V2-6,I,aVL Reciprocal ST depression in II,III & aVF
- 12. Brugada Syndrome • Genetic disease characterized by abnormal ECG and increased risk of sudden death by ventricular fibrillation. • RBBB with persistent ST elevation in right precordial leads.
- 13. Type – 1 Coved ST segment J point elevation >2mm descending ST segment negative T wave
- 14. Type 2 Saddle back pattern J point elevation >2mm ST elevation >1mm positive/biphasic T wave
- 15. Type 3 Either coved or saddle pattern J elevation <2mm ST elevation <1mm
- 16. Left Bundle Branch Block (LBBB) • Activation of left ventricle is delayed and contract later than right ventricle. • QRS duration ≥ 120ms • Broad R wave in I , aVL , V5 &V6 • Prominent QS wave in V1 • Absence of q waves in I and V6
- 17. • Wide spread secondary abnormalities should also be present : • Leads I, aVL usually display downsloping ST depression leading into an inverted T wave. • Leads V1-3 usually display deep S wave , with upsloping ST elevation leading into upright and prominent T wave.
- 18. Broad R wave in I,aVL Prominent QS waves in V1 Absence of q waves in I &V6 Downsloping ST depression with T inversion in I,aVL Upsloping STelevation with upright T wave in V1-3
- 19. Causes • CAD Acute AWMI (new onset LBBB) • Dilated Cardiomyopathy • Aortic stenosis • Long-standing hypertension
- 20. Clinical significance • New onset LBBB is an indication for thrombolytic therapy. • LBBB in the setting of an acute MI worsens the prognosis. • Presence of LBBB cannot be used to diagnose LVH or infarct because LBBB itself results in wide QRS complex and changes in ST-T segment consistent with injury/ischemia.
- 21. Diagnosis of MI in the presence of LBBB Sgarbossa criteria : • ST segment elevation of ≥1mm in concordant with QRS complex in any lead (score 5) • ST depression ≥ 1mm in leads V1-V3 (score 3) • ST segment elevation ≥5mm and discordant with QRS complex (score 2) Score ≥3 indicates Acute Myocardial Infarction.
- 22. ST segment elevation of ≥1mm in concordant with QRS complex in any lead
- 23. ST depression ≥ 1mm in leads V1-V3
- 24. ST segment elevation ≥5mm and discordant with QRS complex
- 25. Incomplete Blocks • Intraventricular conduction abnormalities in which conduction is slowed in bundle, but not completely blocked. • Generally manifests as similar morphology to complete right or left bundle branch block but with QRS duration100 – 120ms. • Compared to complete blocks , etiologies are the same , but clinical significance is reduced.
- 26. Nonspecific Intraventricular Conduction delay • Occurs when QRS duration is prolonged >120ms,but criteria for neither RBBB nor LBBB is met. • It is a marker of non-specific cardiac pathology.
- 27. Left Anterior Fasicular Block (LAFB) • Duration of QRS complex < 120msec • Left axis deviation (> -30 degrees) • qR morphology in Lead I, aVL • rS morphology in Leads II, III, aVF • Prolonged R wave peak time in aVL >45 ms
- 28. Left axis deviation qR morphology in I , aVL rS morphology in II , III , aVF
- 29. Prolonged R-wave peak time (the time from onset of the QRS to the peak of the R wave) in aVL > 45 ms
- 30. LAFB - significance • May be normal variant. • Occurs in Hypertensive heart disease, Cardiomyopathy. • May be seen in acute MI (LAD territory). • LAFB can’t be diagnosed if old Inferior Wall MI evident on ECG (Q-waves in II, III, and aVF ;extreme LAD). LAFB is more common than LPFB
- 31. Left Posterior Fasicular Block • The duration of the QRS complex is normal (<120msec) • Right axis deviation. • rS complexes in Leads I, aVL. • Prominent Q wave in leads II, III, and aVF.
- 32. Right axis deviation rS complexes in Leads I, aVL Prominent Q wave in leads II, III, and aVF Prominent Q waves in II , III , aVF
- 33. Prolonged R-wave peak time (the time from onset of the QRS to the peak of the R wave) in aVF > 45 ms
- 34. LPHB – significance • LPHB may mimic old IWMI due to Q waves in II, III, aVF. • Broad nature & dual blood supply of posterior bundle makes isolated LPFB rare.
- 36. Bifascicular block • Two of three fasicles of His / Purkinje system are blocked. • Most commonly RBBB + either LAFB OR LPFB. Etiologies: • CAD (most common) • Hypertension • Aortic stenosis • Congenital heart diseases
- 37. Trifasicular Block • Presence of conducting disease in all three fasicles. • Has three features • Prolongation of PR interval ( First degree AV block ). • RBBB. • Either LAFB/LPFB.
- 38. Thank you