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Dmitriy Kireyev, Vipul Gupta, Mikhail V Arkhipov, Ashish Bhatia, Joseph A Paris and William E Boden
American Heart Hospital Journal Volume 9 No.1

The differentiation of wide QRS complex tachycardias presents a challenging diagnostic dilemma to many physicians despite multiple published algorithms and approaches.¹ The differential diagnosis includes supraventricular tachycardia conducting over accessory pathways, supraventricular tachycardia with aberrant conduction, antidromic atrio-ventricular reentrant tachycardia, supraventricular tachycardia with QRS complex widening secondary to medication or electrolyte abnormalities, ventricular tachycardia (VT) or electrocardiographic artifacts. The correct diagnosis is essential since it has significant prognostic and treatment implications. In this article we will discuss the factors which support the diagnosis of VT as well as some algorithms useful in the evaluation of regular, wide QRS complex tachycardias.

Appearance
It is a somewhat common misconception that patients with ventricular tachycardias are almost always hemodynamically unstable.² The patient's blood pressure cannot be used as a reliable sign for the differentiation of the origin of an arrhythmia. In a small study by Garratt et al. clinically detectable variation of the first heart sound and examination of the jugular venous pressure were noted to be useful for the diagnosis of a ventricular origin of the arrhythmia.³

Substrate
The assessment of a patient's history may support the increased probability of an arrhythmia originating in the ventricle. A wide QRS complex tachycardia in a patient older than 35 years is more likely to be VT.⁴ A known history of coronary artery disease, previous myocardial infarction or cardiomyopathy makes VT a probable diagnosis. A history of ischemic heart disease or congestive heart failure is 90 % predictive of a ventricular origin of an arrhythmia.⁴ Patients with hypertrophic obstructive cardiomyopathy are prone to have VT.⁵ A known history of arrhythmogenic right ventricular dysplasia or cathecolaminergic polymorphic VT should also point towards a ventricular origin of the tachycardia.

Tetralogy of Fallot is a common cyanotic congenital lesion.⁶ Patients with both unrepaired and repaired conditions are at risk of having VT.^7,8 Patients with a history of Duchenne muscular dystrophy, Becker muscular dystrophy, myotonic dystrophy, Friedreich's ataxia, and Emery-Dreifuss muscular dystrophy are at increased risk of developing cardiomyopathies.⁹ Thus a diagnosis of VT should be considered in these patients presenting with wide complex tachycardias. A history of both short and long QT syndromes makes a ventricular origin of the tachycardia likely as well.^10-12 However, patients with a short QT syndrome and the Brugada syndrome are more likely to present with ventricular fibrillation rather than VT. Infiltrative diseases of the heart such as cardiac amyloidosis or sarcoidosis may also predispose patients to ventricular arrhythmias.^13,14

Interestingly enough, VT is also common in patients with Chagas' disease.¹⁵

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1. State University of New York at Buffalo; 2. Ural Medical Academy, Ekaterinburg, Russia; 3. Buffalo Electrophysiology, LLC; 4. Buffalo General Hospital, Buffalo
2. Correspondence: Dmitriy Kireyev, Cambridge Health Alliance, Whidden Memorial Hospital, Department of Cardiology, 103 Garland Street, Whidden, MA 02149. E: dkireyev@cha.harvard.edu