Ibtisam Al Hoqani

EM – R2

31/8/2010

Outline:

• Basic ECG • What is WCT• Mechanisms of WCT• Diagnostic criteria • Management• Take home message

The Normal Conduction System

what is this rhythm?

Normal Intervals• PR

– 0.20 sec (less than one large box)

• QRS– 0.08 – 0.10 sec (1-2

small boxes)

• QT– 450 ms in men, 460 ms

in women– Based on sex / heart

rate– Half the R-R interval

with normal HR

Differential Diagnosis of Tachycardia

TachycardiaNarrow ComplexWide Complex

RegularST

SVT

Atrial flutter

ST with aberrancyVT

Irregular A-fib

A-flutter with variable conduction

MAT

A-fib with aberrancy

A-fib with WPW

PVT

What is this rhythm?

What is WCT?

It is refers to dysrhythmias with rate greater than 100 beats/min associated with QRS complex duration of more than 0.12 sec

It is divided to:

=Regular

=Irregular

Causes of WCT:

Irregular WCT: – Afib with BBB or IVCD (pre-existent

or rate related)– Afib with anterograde conduction

over accessory pathway in WPW– Polymorphic VT ex: Torsades de

pointes or due to Digitalis intoxication

– Other causes of an irregular rhythm (A flutter with variable conduction, MAT etc) with BBB, WPW, IVCD

Causes of WCT:

Regular rhythm:• Ventricular driven rhythm:

– VT : worst case scenario• Supraventricular rhythm with aberrant

conduction:– SVT with BBB– SVT with accessory pathway Ex:

WPW

How to distinguish SVT from VT

• Focus History

• Physical examination

• ECG tracing

• Using specific Criteria :

Wellens criteria

Brugada criteria

VTSVT with aberrancy

HistoryAge>50

Hx of MI, CHD, CABG, ASHD

Mitral valve prolapse

Previous Hx of VT

Mitral valve prolapse (WPW)

Previous Hx of SVT

Physical examination

Cannon A wave

Variation in arterial pulse

Variation in S1

Absence of variability

ECGFusion beats

AV dissociation

QRS >0.14

Extreme LAD

No response to vagal maneuvers

Preceding P waves with QRS

QRS <0.14

Normal axis

Slow or terminate with vagal maneuvers

Management of WCT

Any new onset symptomatic WCT is VT until proven

otherwise

Management of WCT

• If the patient is hemodynamically unstable, the first-choice therapy for ventricular tachycardia (VT) is synchronized direct-current (DC) cardioversion with 50 – 100 J

• If the patient is suffering from monomorphic VT and has a preserved heart function, the first-line treatment is lidocaine. Alternatives include either amiodarone or procainamide.

• If the patient has polymorphic VT with a normal baseline QT interval, AHA guidelines state that the first steps are to treat ischemia and correct any electrolyte imbalance.

• If cardiac function is impaired, use amiodarone or lidocaine, followed by synchronized DC cardioversion

• If the patient has polymorphic VT with a prolonged baseline QT interval, ACLS guidelines state that any electrolyte imbalance should be corrected. Following this, any one of these treatments can be administered: magnesium sulfate, overdrive pacing, or lidocaine

• Long-term treatment of sustained ventricular arrhythmias includes placement of an implantable cardioverter-defibrillator (ICD) and possible adjunctive therapy with amiodarone or sotalol in certain subsets of patients. Patients should be under the care of a cardiologist or electrophysiologist

Take home message• Any new onset symptomatic WCT

is VT until proven otherwise• About 80% of all WCT are

ventricular tachycardia• In patients with known structural

heart disease almost all WCT are ventricular tachycardia