Heart blockECG Hour

Olivia Faye J Listanco2nd Year IM Resident

Heart Blocks: Bundle branch

INTERRUPTION IN THE ELECTRICAL CONDUCTION SYSTEM OF EITHER THE RIGHT, LEFT OR BOTH BUNDLE BRANCHES.

CAUSES A DELAY TO THE VENTRICLES. THE INTERRUPTION FORCES THE

IMPULSE TO “DETOUR” AND TAKE ANOTHER ROUTE TO THE VENTRICLES.

Right Bundle Branch Block

RBB has ONE FASCICLE

When block occurs, the depolarization in the RBB is DELAYED

Right Bundle Branch Block

Right Bundle Branch BlockQRS complex

> 0.12 seconds

S wave Wide in lead I, wide and slurred in V5 to V6

rsR” V1 and V2Secondary ST-and-T-wave changes in V1 and V2

Left Bundle Branch Block

N septal depolarisation is reversed (RL),

Iimpulse spreads first to the RV via the right bundle branch and then to the LV via the septum

Right Bundle Branch Block CriteriaQRS complex

> 0.12 seconds

R wave Broad monophasic R wave in lead 1, V5, and V6No Q waves in V5 and V6

Left Ant Hemiblock

Left Ant HemiblockAxis LAD (-30 to -90)QRS <120 secR wave qR pattern in AvL

Time to peak R in aVL >45ms

Left Post Hemiblock

Left Post HemiblockAxis RAD (+90 - +180)QRS <120 secR wave qR pattern in lead I and

aVL with qR patterns in leads III ad avFTime to peak R in aVL >45ms

Heart conduction: AV Blocks

OCCUR WHEN THERE IS A PARTIAL OR COMPLETE INTERRUPTION IN THE CARDIAC ELECTRICAL CONDUCTION SYSTEM.

CAN OCCUR ANYWHERE IN THE ATRIA BETWEEN THE SA NODE AND THE AV JUNCTION.

IN THE VENTRICLES BETWEEN THE AV JUNCTION AND PURKINJE FIBERS.

THE APPEARANCE OF THE P WAVE AND QRS COMPLEX VARIES, DEPENDING ON THE TYPE OF HEART BLOCK.

RATE AND RHYTHM MAY VARY. LOCATION OF THE BLOCK AND PATIENT

SYMPTOMS DETERMINE IF THE DYSRHYTHMIA IS

LETHAL.

Normal Sinus RhythmRhythm RegularRate 60 – 100

P wave Normal in configuration; precede each QRS

PR Normal ( 0. 12 – 0.20 seconds )

QRS Normal ( less than 0.12 seconds )

First-degree AV blockRhythm RegularRate Usually normal

P wave Sinus P wave present; one P wave to each QRS

PR Prolonged (greater than 0.20 seconds )

QRS Normal

Second -degree AV block, Mobitz IRhythm IrregularRate Usually slow but can be

normalP wave Sinus P wave present; some

not followed by QRS complexes

PR Progressively lengthensQRS Normal

Second-degree AV block, Mobitz IIRhythm

Regular usually; can be irreguler if conduction ratios vary

Rate Usually slow

P wave Two, three, or four P waves before each QRS

PR PR interval of beat with QRS is constant; PR interval may be normal or prolonged

QRS Normal if block in His bundle, wide if block involves bundle branches

Third-degree AV blockRhythm RegularRate 40 – 60 if block in His bundle;

30 – 40 if block involves bundle branchesP wave Sinus P wave present; bear no

relationship to QRS; PR Varies greatlyQRS Normal if block in His bundle; wide if

block involves bundle branches

Mobitz I

Mobitz II atrioventricular block

Atrioventricular dissociation secondary to complete heart block

High-grade atrioventricular block

AF in RVR, RBBB, LAHB

Atrial flutter with LBBB

RBBB

LBBB

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