ATRIOVENTRICULAR BLOCK , BLOCK NHĨ THẤT ĐỘ 3 ,Đ H Y DƯỢC TP HCM

Bài giảng dành cho sinh viên y khoa, bác sĩ đa khoa, sau đại học. ĐH Y Dược TP Hồ Chí Minh. Description Causes Significance Diagnosis Management

COMPLETE (THIRD DEGREE) ATRIOVENTRICULAR BLOCK

Bộ môn Nhi – ĐH Y Dược TP HCM

TS BS Vũ Minh Phúc

1 Description

2 Causes

3 Significance

4 Diagnosis

5 Management

1 DESCRIPTION

• Complete Heart Block (CHB) :

atrial and ventricular activities are entirely independent of each other

• CHB may occur at :

– A-V node

– His bundle

– both bundle branches

– atria-supranodal site

1 DESCRIPTION

• ECG manifestations

– atrioventricular (P : Q) dissociation

– supraventricular rhythm (P waves):

• P waves are regular (regular P-P interval)

• P rate = normal heart rate for the patient’s age

– ventricular rhythm (QRS complex)

• normal QRS (idionodal rhythm) abnormal (idioventricular rhythm)

• ventricular rate (QRS rate) < atrial rate (P rate)

• regular or irregular rhythm

1 DESCRIPTION

• ECG manifestations

2 CAUSES

• Congenital type

– without structure heart defect

– with congenital heart disease (CHD) : corrected TGA – maternal disease:

SLE, Sjogren’s disease, connective tissue disease

• Acquired type

– cardiac surgery

– myocarditis (virus, bacteria, ARF, Lyme’s disease) – overdoses of certain drugs (beta blockers, calcium blockers, digitalis, antiarrhythmic agents, …), toxins – cardiac tumor

– cardiomyopathies

– myocardial infarction

3 SIGNIFICANCE

• Congestive heart failure (CHF)

– in congenital CHB with CHD : CHF early occur in infancy – in acquired CHB : myocarditis, intoxication

• Syncopal attacks (Adam-Stokes attacks)

– occur with HR < 40-45 bpm

– sudden onset of acquired CHB

• Asymptomatic child, normal growth and

development , only cardiomegaly on CXR

for 5-10 years in congenital CHB without CHD

3 SIGNIFICANCE

• Key points in examination

– Carefully take the history

– Vital signs (BP, concious level, hypothermia) – Evidence of congestive heart failure

– Evidence of hemodynamic compromise

4 DIAGNOSIS

• Positive diagnosis based on ECG

• Differential diagnosis : A-V dissociation without CHB

(atrial rate < ventricular rate)

• Determine causes based on:

– history

– clinical picture

– specific test, cardiac imaging

 Congenital CHB: normal QRS; ventricular rate is faster (50-80 bpm), response to varying physiologic conditions

 Acquired CHB: abnormal QRS; ventricular rate is low (40-50 bpm) and is relatively fixed

5 MANAGEMENT

• Congenital type

– asymptomatic CHB, acceptable HR, narrow QRS complex, normal ventricular function

NO TREATMENT

• Symptomatic CHB (dizziness, lightheadness, …)

• CHF

• Infants have

– ventricular rate < 50-55 bpm – ventricular rate < 70 bpm associated with CHD

• Wide QRS, complex ventricular ectopy, ventricular dysfunction

5 MANAGEMENT

• Acquired type

– drugs are given during preparation for temporary pacemaker if patients have CHF or hemodynamic compromise

– temporary transvenous ventricular pacing (VVI)

temporary transcutaneous pacing

– permanent pacemaker if CHB does not disappear