The "qRBBB" pattern

Presence of qRBBB in the setting of acute coronary syndrome signifies proximal occlusion of left descending coronary artery with compromise of circulation in the septal arteries supplying the bundle branches. Anterior STEMi with RBBB is associated with a higher risk of death when compared with that of patients with normal conduction. 

qRBBB with LAFBInstead of the rSR pattern (seen in RBBB), there is qRBBB pattern in V1 because the initial r wave has been knocked off by anterior wall myocardial infarction. 

Due to anterior location of the right ventricle than that of the left ventricle, activation of the right ventricular free wall can neutralize the abnormal septal forces associated with an anteroseptal MI. Therefore, in most patients with an anteroseptal infarction, abnormal Q waves in right precordial leads is mostly manifest during RBBB showing the classical qRBBB pattern, due to delayed activation of the right ventricle. 

Understanding RBBB
RBBB causes delayed depolarisation of right Ventricle as depolarisation spreads across the septum (instead of the Right Bundle) taking longer than usual. This produces characteristic ECG changes described below in the diagnostic criteria. Left Ventricle depolarisation remains normal i.e normal early part of QRS complex. 

Diagnostic Criteria 

• Broad QRS > 120 ms
• RSR’ pattern in V1-3 (‘M-shaped’ QRS complex) or a broad monophonic r wave or a qR complex
• Wide, slurred S wave in the lateral leads (I, aVL, V5-6
• Delayed intrinsicoid deflection time 

RBBB (Image from LIFTL)

RBBB often shows STD and TWI in V1-3 due to secondary depolarisation abnormalities 

Causes

• Ischemic Heat Disease
• Acute Pulmonary HTN (PE)
• Chronic Pulmonary HTN (Cor Pulmonale)
• Valvular Heart Disease
• Myocarditis
• Degenerative Diseases of conduction system
• Congenital Heart Disease
• Overdose of Na Channel Blockers
• Idiopathic
• Transient and Rate Related 

RBBB should NOT have any ST Elevation. Look for the qRBBB pattern and RBBB with LAFB (Leftward Axis, qR in lead I, aVL, rS in lead III) pattern. 

qRBBB in V1-4 with STE (Image from TheECGinAcuteMI)

Take Home:

• Remember the qRBBB pattern morphology
• RBBB should never have any ST elevation 
• When in doubt, do serial ECGs and screening bedside ECHO to look for RWMA

References and Further Reading:

1. Mishra, V., Sinha, S. K., & Razi, M. (2016). Right Bundle Branch Block: A Masquerader in Acute Coronary Syndrome. North American Journal of Medical Sciences, 8(2), 121–122. http://doi.org/10.4103/1947-2714.177347
2. 2. Widimsky P, Rohác F, Stásek J, Kala P, Rokyta R, Kuzmanov B, et al. Primary angioplasty in acute myocardial infarction with right bundle branch block: Should new onset right bundle branch block be added to future guidelines as an indication for reperfusion therapy? Eur Heart J. 2012;33:86–95.
3. Ganesan S, Kannan K, Victor A, Selvan KT, Arun R, Majella JC, Kumar RS, Aravind A, Viswanathan N, District V. QRBBB in acute coronary syndrome: Does it matter in modern era? Angiographic correlation. Indian Heart Journal. 2015 Dec 1;67:S38.
4. Wong CK, Stewart RA, Gao W, French JK, Raffel C, White HD. Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: Insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial. Eur Heart J. 2006;27:21–8. 
5. http://hqmeded-ecg.blogspot.co.uk/2010/01/right-bundle-branch-block-with-subtle.html
6. http://hqmeded-ecg.blogspot.co.uk/2017/04/rbbb-with-transient-st-elevation.html
7. http://hqmeded-ecg.blogspot.co.uk/2010/11/wide-complex-tachycardia-its-really.html
8. http://hqmeded-ecg.blogspot.co.uk/2014/03/elderly-woman-in-shock-ekg-from.html
9. https://emcrit.org/wp-content/uploads/2015/03/Who-to-PCI-by-Smith-and-Weingart.pdf
10. https://lifeinthefastlane.com/ecg-library/basics/right-bundle-branch-block/

Posted by:

              

     Lakshay Chanana

     

     Speciality Doctor

     Northwick Park Hospital

     Department of Emergency Medicine

     England

     @EMDidactic