Journal reading by Emergency Deaprtment R2 zeno

112/04/12

Topic

• From AJEM

• Right bundle-branch block in acute coronary syndrome: diagnostic and therapeutic implications for the emergency physician

• Department of Emergency Medicine, University of Virginia, Charlottesville, VA 22908, USA

Introduction

• RBBB in ACS patient is a marker of significant potential cardiovascular risk

• RBBB pattern in ACS patient identifies a subgroup with quite high short- & long-term morbidity and mortality.

Right bundle brach

• The proximal and terminal thirds of the right bundle traverse close to the endocardium and thus are the most vulnerable to stretch or traumatic injury

• These specific areas are the sites where right RBBB is most common.

Right bundle branch

• Dual blood supply– LAD: most perfusion – RCA or LCX : depending on the dominance of the

particular coronary system. • Kurisu and Colleagues :

Anterior wall STEMI with RBBB LAD or multivessel coronary disease

Right bundle branch • Injury mechanisms to RBB

– Structural • Ischemia, infarction, inflammation, cardiomyopathy, and

congenital heart disease– Functional (interventricular septal stretch)

• Cor pulmonale and pulmonary embolism– Iatrogenic: Placement right heart catheter– A rate-related BBB is a type of functional BBB, occurring at

excessive rates; in this setting, the rhythm‘s rate is so rapid that the subsequent impulse arrives before the bundle branch has fully repolarized, thus producing dysfunctional conduction and the BBB.( 如果心律太快產生的 BBB 是功能性的 BBB)

Right bundle branch

• Investigations demonstrate that age, DM, and anterior wall infarction are related to the development of RBBB.

• RBBB is marker of slowly progressive degenerative disease of the conduction system.

• The prognosis of RBBB– Related to presence, type, and severity of underlying

cardiac disease. – Isolated RBBB has an excellent prognosis– Isolated LBBB portends higher cardiac mortality rate

RBBB-ECG

• Regardless cause or location of the bundle injury, ECG all similar.

NSR with RBBB. QRS complex > 0.12 s, RsR′ complex in V1, and the RS complex in V6. The R wave < R′ wave, a highly characteristic feature of the RBBB pattern.

RBBB-ECG

• Traditional ECG criteria– QRS complex > 0.12 second – RsR QRS complex in V1′– Widened or “slurred” S wave in leads I and V6

RBBB-ECG

• QRS complex in V1: “rabbit ears” or M-shaped morphology

RBBB-ECG

• R or r ：– If >5 mm, use capital R to represent

• S or s ：– If small (1-3 mm) ： s– If large (3-6 mm) ： S

• Common QRS in V1 ：– monophasic R wave (large,entirely positive structure)– rsr′– rsR′– rSR ′– Septal MI ： qR or qrsR′ pattern.

RBBB-ECG

• Lead V6 ： RS configuration. • I, aVL, V5 ： “ slurring” of the S wave, too.• Axis in RBBB is usually normal but can be leftward or

rightward. – Concomitant block of either the anterior or posterior

fascicle of the left bundle, which by definition is a bifascicular conduction block

RBBB-ECG

• ST-segment and T-wave changes ：– Normal relationship ： QRS complex / ST-T

appropriate discordance. ST-T wave changes tend to be discordant to the primary QRS complex vector

– Terminal portion of the QRS ： located on the opposite side of the isoelectric baseline from the ST segment and initial portion of the T wave.

ACS diagnosis

• Prevalence of RBBB in the AMI ： 3~29%– Preexisting vs newly developed

• Newly was common in younger patients and women• Preexisting more likely in older individuals and in those

with significant comorbidity (DM,CAD)– Transient vs permanent.

• Moreno and colleagues ：– 10.8% of AMI cases presented with RBBB– 65% of individuals demonstrated a new-onset RBBB– 56% of these patients demonstrated a transient RBBB in

the periinfarct period

ACS diagnosis

• Kleemann and colleagues ：– AMI with RBBB ： 11.5%– STEMI ： 4.4%– NSTEMI ： 7.1%– NSTEMI-related RBBB ：

• Varied and less easily Dx by ECG. • Pivotal study ： serum marker tracing

ACS diagnosis

• LBBB ： obscures ECG Dx of AMI, RBBB does not.• In the right ~ mid precordial leads, the positive QRS will be

associated with ST depression / inverted T wave. • A “violation” of this concept ST-segment elevation• the T-wave findings are more often variable with either

continued inversion or disappearance (lost within the greater ST segment)

RBBB in ACS treatment & prognosis

• AMI presence of RBBB is associated with more complex clinical presentations, with higher rates of high-risk coronary artery obstructive patterns, cardiovascular complications, and death.

• 30-day mortality ： RBBB is powerful independent predictor – AMI with RBBB ： 14% – AMI w/o RBBB ： 2%

• More likely to experience acute CHF, hypotension, cardiogenic shock, and cardiac arrest, pacemaker placement.

• Permanent RBBB VS. transient RBBB 73% vs 37%,