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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 CONTENTS Description Causes Significance Diagnosis Management 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 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 DESCRIPTION • ECG manifestations 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 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 SIGNIFICANCE • Key points in examination – Carefully take the history – Vital signs (BP, concious level, hypothermia) – Evidence of congestive heart failure – Evidence of hemodynamic compromise 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 MANAGEMENT • Congenital type – asymptomatic CHB, acceptable HR, narrow QRS complex, normal ventricular function NO TREATMENT – PERMANENT PACEMAKER in patients with: • 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 MANAGEMENT • Acquired type – drugs are given during preparation for temporary pacemaker if patients have CHF or hemodynamic compromise • Atropin IV : 0.02 mg/kg • Isoproterenol IV : 0.1-0.5 g/kg/min • Dopamin IV > 5-20 g/kg/min • Epinephrine IV : 0.1-1 g/kg/min – temporary transvenous ventricular pacing (VVI) temporary transcutaneous pacing – permanent pacemaker if CHB does not disappear • after weeks in myocarditis, toxication • after week in CHB after cardiac surgery ... myocarditis (virus, bacteria, ARF, Lyme’s disease) – overdoses of certain drugs (beta blockers, calcium blockers, digitalis, antiarrhythmic agents, …), toxins – cardiac tumor – cardiomyopathies... – His bundle – both bundle branches – atria-supranodal site DESCRIPTION • ECG manifestations – atrioventricular (P : Q) dissociation – supraventricular rhythm (P waves): • P waves are regular...CONTENTS Description Causes Significance Diagnosis Management DESCRIPTION • Complete Heart Block (CHB) : atrial and ventricular activities are entirely independent of each other • CHB may