SVT, NHỊP NHANH TRÊN THÁT, 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.ĐỊNH NGHĨA NHỊP NHANH TRÊN THÁT, PHÂN LOẠI NHỊP NHANH TRÊN THÁT, CƠ CHẾT, HÌNH ẢNH ECG, NGUYÊN NHÂN, XỬ TRÍ NHỊP NHANH TRÊN THÁT

Supraventricular Tachycardia (SVT)

❂ 1 /250-1000 children

• More common in males younger than 4 months of

age

• Predisposing factors: fever, infection, drug exposures

❂ Etiologies

• 50% idiopathic

• 23% associated with congenital heart disease (CHD)

– VSD, Ebstein’s anomaly, L-TGA, cardiomyopathy

– Postoperative: TGA, ASD, AVSD, Fontan

• 22% Wolfe-Parkinson-White Syndrome (WPW)

❂ EKG

• Narrow complex

• Similar morphology to QRS in sinus rhythm

• Wide complex (SVT with aberrancy)

• P wave obscured or buried in T wave

• Short PR interval with delta wave suggests WPW

❂ Younger children <4 mos

• Rate 230-320 beats per minutes (BPM)

• Can present with congestive heart failure (CHF)

❂ Older child

• Rate 150-250 BPM

• More likely to be WPW, concealed pathway, CHD

SVT Mechanisms

❂ Age dependent

❂ Reentry tachycardia

• Accessory pathway 90%

– WPW with preexcitation with ante grade conduction

• Concealed pathway (unidirectional) with only

retrograde VA conduction

❂ Atrial ectopic tachycardia

• Atrial flutter/fibrillation

❂ AV node re-entry tachycardia (AVNRT)

• More common in older children

❂ Junctional ectopic tachycardia

• Commonly seen in the postoperative periods

90% Narrow QRS tachycardia

P waves not visible, abnormal axis

SVT Mechanisms

Reentry Tachycardia Accessory Pathway

ORT, ART, AVNRT, PJRT WPW, URAP, Dual AVN

Orthodromic Reciprocating Tachycardia

AP with rapid conduction, longer ERP

AV node with slow conduction, shorter ERP

Rate related BBB

Retrograde P may not be visible

Variable rates occurs with dual AVN

Wolff-Parkinson-White

Syndrome

Atrial Flutter

Rate 280-450 BPM (Infants may have more than 500 BPM) Typical saw-tooth F waves

Atrial Flutter/Fibrillation

Mechanism

Reentry SVT

❂ Paroxysmal (sudden onset/termination)

❂ Two pathways: AVN and accessory pathway

❂ Accessory pathway: functional/anatomic

❂ Associated cardiac defects: Ebstein’s anomaly, L-TGA (congenitally corrected TGA), single ventricle, WPW syndrome, hypertrophic

cardiomyopathy

❂ Young infant

• Irritability, lethargy, dyspnea, vomiting, mottling, cyanosis, CHF, hepatomegaly

❂ Older child

• Palpitation, dizziness, exercise

intolerance

• Throbbing neck pain from distended

neck vein

• Abdominal pain, nausea, vomiting

• Syncope from hypotension

❂ Present as infants

❂ Present >5 yrs of age

❂ WPW

Acute Treatment-Stable

Patients

❂ Vagal stimulation

❂ Ice to face (diving reflex)

❂ Adenosine: fast acting, short duration

❂ Mechanism: block AV and sinus nodes

❂ Side effects: bronchospasm

❂ Not effective vs atrial flutter/fib, VT,

nonreciprocating atrial tachycardia

Acute Treatment

❂ IV beta blockers

function depression, hypoglycemia)

❂ Digoxin

CHF

❂ Refractory case

Acute Treatment-Unstable

❂ Cardioversion: 1-2 Joules/kg

Chronic Treatment

❂ Sotalol, flecanide

• Oral beta-blocker or radio frequency ablation

❂ Digoxin maintenance 3-6 months

❂ Radiofrequency Ablation in cardiac catheterization lab

• Indications

– Syncope, resuscitation from cardiac arrest, ventricular

dysfunction

– Not respond to medications or unacceptable side effects – Patient choice

• Success rates

– Accessory pathway 90%

– AVNRT 96%

– Ectopic atrial tachycardia 88%

– Atrial flutter 76%

❂ Pediatric Cardiovascular Medicine

❂ Cardiac Arrhythmia in Children and Young Adults with Congenital Heart Disease