Written by Jesse McLaren; Peer Reviewed and edited by Anton Helman. August 2020
情况1：70yo胸痛。HR 140，BP 150，RR20，饱和98％。老那么新的心电图：
案例2: 70yo with syncope. AVSS. Old then new ECG:
案例3：75yo胸痛一个小时。HR 90，BP 85/50。老那么新的心电图：
案例4: 40yo prior CABG with 2hr chest pain. AVSS. Old then new ECG:
案例7：65yo具有恒定的胸痛一天。边缘性心动过速与正常BP / SATS。事先没有心电图
当右束支被阻断，隔膜去极化（左到右），随后由左心室的去极化迅速经由左束支，然后右心室去极化缓慢。So QRS is prolonged >120ms (incomplete RBBB if <120ms), right-sided precordial leads have RsR’ in V1 (R from septal depolarization, S from LV depolarization, and R’ from delayed RV depolarization), and left-side precordial leads have RS wave (with rapid R from LV depolarization, and slurred S from slower RV depolarization). Axis should be normal in RBBB, and an abnormal axis could be the clue to a concomitant left anterior fascicular block (left axis, qR in I/aVL and rS in II/III/aVF) or left posterior fascicular block (right axis, rS in I/aVL, qR in III/aVF), or another reason for altered axis.
As with other causes of abnormal depolarization, RBBB causes repolarization abnormalities that can mask or mimic ischemic changes (especially in right-sided precordial leads that have RSR’), but the concept of appropriate discordance can help. As a review summarized: “The major, terminal portion of the QRS complex and the initial portion of the ST segment/T wave are discordant, meaning that they are located on opposite sides of the isoelectric baseline. Thus, in the right to mid precordial leads, the largely positive QRS complex will be associated with ST-segment depression and an inverted T wave. A ‘violation’ of this concept will manifest as ST-segment elevation, which is concordant with the major, terminal portion of the QRS complex; the T-wave findings are often variable with either continued inversion or disappearance (lost within the greater ST segment itself). Anterior wall STEMI is therefore usually quite obvious if the clinician is comfortable with the appropriate appearance of the ST segment in RBBB.” But sometimes ECG changes can be subtle or non-existent. As with the guideline for PCI in patients with refractory ischemia, the 2017 European Society of Cardiology advises, “Patients with MI and right bundle branch block (RBBB) have a poor prognosis.这可能是难以检测患者胸痛和右束支阻滞透缺血。Therefore, a primary PCI strategy (emergent coronary angiography and PCI if indicated) should be considered when persistent ischaemic symptoms occur in the presence of RBBB.”
Old RBBB+LAFB, new rapid atrial fibrillation and rate-related ST changes. Cath lab activated based on mild inferior ST elevation, but ST changes resolved with rate control. Mild troponin elevation from non-occlusive MI.
有那些d LAFB and new RBBB which was misinterpreted as showing anterior ST elevation, but this is within the prolonged depolarization of RBBB
有那些d RBBB/LPFB with new ST elevation and pseudonormalized T waves in I/aVL, with reciprocal inferior ST depression. Cath lab activated: occlusion of graft to diagonal artery.
First degree heart block and RBBB/LAFB unknown age. V2 has RBBB depolarization changes and should have discordant ST depression but instead there is mild concordant ST elevation.
Incomplete RBBB and LAFB age indeterminate. V3-4 have ST depression and T wave inversion (and V3 has no RSR’ so this is not simply discordant changes), and there is inferior ST depression and T wave inversion (reciprocal to the electrocardiographically silent lateral wall). 15 lead ECG:
Only minimal ST elevation in V8, but 12 lead shows后闭塞MI直到证明并非如此。导管室激活：闭塞的回旋钝缘支。出院诊断“NSTEMI”。正火ST / T上放电ECG：
右束支阻滞is a high risk feature in occlusion MI, especially if new and accompanied by LAFB. If a patient has ischemic symptoms and RBBB, compare with prior to see if this is new, and look for associated fascicular blocks and ST changes