5Right Bundle Branch Block First Phase will be normalSecond Phase -NormalThird Phase -?After the left ventricle has completely depolarized, the right ventricle continues to depolarize
6Right Bundle Branch Block 188.8.131.52. r wave in V1q wave in V62. S wave in V1R wave in V63. R’ wave in V1S wave in V6
7Right Bundle Branch Block Criteria V1 or V2 = rSR’ - “M” or rabbit ear shapeV5 or V6 = qRSLarge R wavesRight chest leads: T wave inversion (“secondary changes” since they reflect a delay in depolarization not an actual change in depolarization).Complete RBBB: QRS > 0.12 sec.Incomplete RBBB: QRS = 0.10 to 0.12 sec.
10Right Bundle Branch Block Clinical SignificanceHealthy heartOrganic heart diseaseatrial septal defectpulmonary diseasevalvular lesionsdegenerative changes in conduction systemchronic coronary artery diseasepulmonary embolismafter bypass graft surgeryPermanent or transientRBBB by itself requires no treatment
11Left Bundle Branch Block RBBB affects mainly the terminal phase of depolarizationLBBB affects the early and terminal phases of depolarizationSeptum is depolarized from right to left (rather than left to right)Depolarization of the left ventricle takes longer
12Left Bundle Branch Block 1. r wave in V1R wave in V62. S wave in V1R wave in V6
13Left Bundle Branch Block Loss of septal R in V1 and septal Q in V6.Wide QRSNegative in V1Positive in V6
14Left Bundle Branch Block Criteria Wide QRS complexV1 = QS (or rS) and may have a “W” shape to it.V6 = R or notched R showing a “M” shape or rabbit earsSecondary T wave inversionSecondary if in lead with tall R wavesPrimary if in right precordial leads
24Tri-fascicular Conduction System Right bundleLeft anterior (superior) fascicleLeft posterior (inferior) fascicleFascicular block (or hemiblock) = a block in either the LAF or LPF.
25Fascicular Blocks Fascicular blocks only slightly prolongs the QRS. Fascicular blocks cause axis deviation as do infarcts and hypertrophy.Left or right axis deviation without signs of infarct or hypertrophy are fascicular blocks.
26Left Anterior Fascicular Block Limb leadsQRS less width less than 0.12 sec.QRS axis = Left axis deviation (-45° or more)if S wave in aVF is greater than R wave in lead Ismall Q wave in lead I, aVL, or V6
27Left Posterior Fascicular Block Right axis deviation (QRS axis +120° or more)S wave in lead I and a Q wave in lead III (S1Q3)Rare
28Bifascicular Block Two of the three fascicles are blocked. Most common is RBBB with left anterior fascicular block.
29SummaryThe last component of the QRS vector will be shifted in the direction of the last part of the ventricles to be depolarized.In other words, the major QRS vector shifts toward the regions of the heart that are most delayed in being stimulated.RBBB: late QRS forces point toward the right ventricle (Rabbit ears, M shape in V1)LBBB: late QRS forces point toward the left ventricle (negative in V1 and R or notched R in V6)LAFB: late QRS forces point in a leftward and superior direction (LAD with deep S wave in aVF ).
30Hypertrophy In The Presence of Bundle Branch Block RVH and RBBBRAD is typically seen; also look for RAE and its peaked P waves.RBBB with RAD indicates RVH is likely present, too.LVH and RBBusual criteria can be used but also look for LAE