Ventricular Arrhythmia, Idiopathic

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Ventricular tachycardia occurs with no evidence of structural heart disease

• Lack of structural heart disease is defined by normal findings on ECG, echocardiogram, and coronary angiography

GENERAL CONSIDERATIONS

• Tachycardia may be caused by triggered activity (typically left or right ventricular outflow tract tachycardia) or reentry (typically left ventricular tachycardia)

• Triggered outflow tract tachycardias are dependent on cyclic adenosine monophosphate and often respond to IV adenosine

• MRI may be abnormal and show ventricular fatty deposits or frank right ventricular dysplasia, which is a hallmark of arrhythmogenic right ventricular dysplasia (ARVD)

• The idiopathic left ventricular tachycardia is more often induced by atrial pacing and is sensitive to verapamil

• Sudden death is rare, and implantable cardioverter-defibrillator (ICD) is not always required since cure rate with ablation can be high

• Overall, the arrhythmia carries a benign prognosis

• These tachycardias are generally monomorphic

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Palpitations

• Syncope

• Presyncope

PHYSICAL EXAM FINDINGS

• Normal physical exam findings

DIFFERENTIAL DIAGNOSIS

• Intramyocardial reentrant ventricular tachycardia

• ARVD

• Mahaim tachycardia

• Tachycardia following repair of tetralogy of Fallot

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Thyroid-stimulating hormone

• Comprehensive metabolic panel

ELECTROCARDIOGRAPHY

• ECG to assess morphology of the QRS during VT

• Left bundle branch block (LBBB), inferior axis with a late R/S precordial transition suggests right ventricular outflow tract (RVOT) origin

• Right bundle branch block (RBBB), left or superior axis suggests left posterior fascicle in origin

• RBBB, right inferior axis suggests left anterior fascicle in origin

• Exercise stress test may be used to initiate tachycardia

• Signal-averaged ECG may be helpful (unremarkable in RVOT and ventricular tachycardia and abnormal in ARVD)

IMAGING STUDIES

• MRI of the heart to exclude right ventricular dysplasia and to assess for any ventricular scar (substrate for VT)

DIAGNOSTIC PROCEDURES

• Electrophysiology study to establish mechanism and determine suitability for ablation

TREATMENT

CARDIOLOGY REFERRAL

• All patients require evaluation by a cardiac electrophysiologist

HOSPITALIZATION CRITERIA

• Following syncope

MEDICATIONS

• Beta blockers, metoprolol 50 mg PO twice daily to a maximum usual dosage of 200 mg/day; or verapamil, start 180 mg/day, next dose 360 mg/day

• Class IA, IC, or III antiarrhythmic agents

• In acute conditions, in the emergency room, adenosine can be used to terminate ventricular tachycardia

THERAPEUTIC PROCEDURES

• Radiofrequency ablation in appropriate cases

SURGERY

• Generally not ...