The increased heart rate also leads to increased work and oxygen demand by the heart, which can lead to rate related ischemia. Differential diagnosis
An electrocardiogram (ECG) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on the QRS complex. Equal or less than 0.1s for narrow complex. Presented order of most to least common, they are:
Narrow complex
Sinus tachycardia, which originates from the sino-atrial (SA) node, near the base of the superior vena cava
Atrial fibrillation
Atrial flutter
AV nodal reentrant tachycardia
Accessory pathway mediated tachycardia
Atrial tachycardia
Multifocal atrial tachycardia
Cardiac Tamponade
Junctional tachycardia (rare in adults)
Wide complex
Ventricular tachycardia, any tachycardia that originates in the ventricles
Any narrow complex tachycardia combined with a problem with the conduction system of the heart, often termed "supraventricular tachycardia with aberrancy"
A narrow complex tachycardia with an accessory conduction pathway, often termed "supraventricular tachycardia with pre-excitation" (e.g. Wolff–Parkinson–White syndrome)
Pacemaker-tracked or pacemaker-mediated tachycardiaTachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and wide refer to the width of the QRS complex on the ECG. Narrow complex tachycardias tend to originate in the atria, while wide complex tachycardias tend to originate in the ventricles. Tachycardias can be further classified as either regular or irregular. Sinus
The body has several feedback mechanisms to maintain adequate blood flow and blood pressure. If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex tachycardia.
Terminology
The word tachycardia came to English from New Latin as a neoclassical compound built  from the combining forms tachy- + -cardia, which are from the Greek ταχύς tachys, "quick, rapid" and καρδία, kardia, "heart". As a matter both of usage choices in the medical literature and of idiom in natural language, the words tachycardia and tachyarrhythmia are usually used interchangeably, or loosely enough that precise differentiation is not explicit. Some careful writers have tried to maintain a logical differentiation between them, which is reflected in major medical dictionaries and major general dictionaries. The distinction is that tachycardia be reserved for the rapid heart rate itself, regardless of cause, physiologic or pathologic (that is, from healthy response to exercise or from cardiac arrhythmia), and that tachyarrhythmia be reserved for the pathologic form (that is, an arrhythmia of the rapid rate type). This is why five of the previously referenced dictionaries do not enter cross-references indicating synonymy between their entries for the two words (as they do elsewhere whenever synonymy is meant), and it is why one of them explicitly specifies that the two words not be confused. But the prescription will probably never be successfully imposed on general usage, not only because much of the existing medical literature ignores it even when the words stand alone but also because the terms for specific types of arrhythmia (standard collocations of adjectives and noun) are deeply established idiomatically with the tachycardia version as the more commonly used version.