Holter monitor-Imaging with start (red arrow) and end (blue arrow) of a SV-tachycardia with a pulse frequency of about 128/min. A 12-lead ECG showing paroxysmal<unk>  at about 180 beats per minute. Subtypes of<unk>  can often be distinguished by their electrocardiogram (ECG) characteristics Most have a narrow QRS complex, although, occasionally, electrical conduction abnormalities may produce a wide QRS complex that may mimic ventricular tachycardia (VT). In the clinical setting, the distinction between narrow and wide complex tachycardia<unk>  vs. ventricular) is fundamental since they are treated differently. In addition, ventricular tachycardia can quickly degenerate into ventricular fibrillation and death and merits different consideration. In the less common situation in which a wide-complex tachycardia may actually be<unk> , a number of algorithms have been devised to assist in distinguishing between them. In general, a history of structural heart disease markedly increases the likelihood that the tachycardia is ventricular in origin. * Sinus tachycardia is physiologic or "appropriate" when a reasonable stimulus, such as the catecholamine surge associated with fright, stress, or physical activity, provokes the tachycardia. It is identical to a normal sinus rhythm except for its faster rate (>100 beats per minute in adults). However, sinus tachycardia is considered part of the diagnoses included in<unk>  by most sources. * Sinoatrial node reentrant tachycardia (SANRT) is caused by a reentry circuit localised to the SA node, resulting in a P-wave of normal shape and size (morphology) that falls before a regular, narrow QRS complex. It cannot be distinguished electrocardiographically from sinus tachycardia unless the sudden onset is observed (or recorded on a continuous monitoring device). It may sometimes be distinguished by its prompt response to vagal maneuvers. * Ectopic (unifocal) atrial tachycardia arises from an independent focus within the atria, distinguished by a consistent P-wave of abnormal shape and/or size that falls before a narrow, regular QRS complex. It can be caused by automaticity, which means that some cardiac muscle cells, which have the primordial (primitive, inborn, inherent) ability to generate electrical impulses that are common to all cardiac muscle cells, have established themselves as a 'rhythm center' with a natural rate of electrical discharge that is faster than the normal SA node. Some atrial tachycardias, rather than being a result of increased automaticity may be a result of a micro-reentrant circuit (defined by some as less than 2 cm in longest diameter to distinguish it from macro-reentrant atrial flutter). Still other atrial tachycardias may be due to triggered activity caused by after-depolarizations. * Multifocal atrial tachycardia (MAT) is tachycardia arising from at least three ectopic foci within the atria, distinguished by P-waves of at least three different morphologies that all fall before irregular, narrow QRS complexes. This rhythm is most commonly seen in elderly people with COPD. Atrial fibrillation: Red dots show atrial fibrillation activity. * Atrial fibrillation meets the definition of<unk>  when associated with a ventricular response greater than 100 beats per minute. It is characterized as an "irregularly, irregular rhythm" both in its atrial and ventricular depolarizations and is distinguished by its fibrillatory atrial waves that, at some point in their chaos, stimulate a response from the ventricles in the form of irregular, narrow QRS complexes. * Atrial flutter, is caused by a re-entry rhythm in the atria, with a regular atrial rate often of about 300 beats per minute. On the ECG this appears as a line of "sawtooth" waves preceding the QRS complex. The AV node will not usually conduct 300 beats per minute so the P:QRS ratio is usually 2:1 or 4:1 pattern, (though rarely 3:1, and sometimes 1:1 where class IC antiarrhythmic drug are in use). Because the ratio of P to QRS is usually consistent, A-flutter is often regular in comparison to its irregular counterpart, atrial fibrillation. Atrial flutter is also not necessarily a tachycardia by definition unless the AV node permits a ventricular response greater than 100 beats per minute. * AV nodal reentrant tachycardia (AVNRT) involves a reentry circuit forming next to, or within, the AV node. The circuit most often involves two tiny pathways one faster than the other. Because the node is immediately between the atria and ventricle, the re-entry circuit often stimulates both, appearing as a backward (retrograde) conducted P-wave buried within or occurring just after the regular, narrow QRS complexes. * Atrioventricular reciprocating tachycardia (AVRT), also results from a reentry circuit, although one physically much larger than AVNRT. One portion of the circuit is usually the AV node, and the other, an abnormal accessory pathway (muscular connection) from the atria to the ventricle. Wolff-Parkinson-White syndrome (WPW) is a relatively common abnormality with an accessory pathway, the bundle of Kent crossing the AV valvular ring. * In orthodromic AVRT, atrial impulses are conducted down through the AV node and retrogradely re-enter the atrium via the accessory pathway. A distinguishing characteristic of orthodromic AVRT can therefore be an inverted P-wave (relative to a sinus P wave) that follows each of its regular, narrow QRS complexes, due to retrograde conduction. * In antidromic AVRT, atrial impulses are conducted down through the accessory pathway and re-enter the atrium retrogradely via the AV node. Because the accessory pathway initiates conduction in the ventricles outside of the bundle of His, the QRS complex in antidromic AVRT is wider than usual. A delta wave is an initial slurred deflection seen in the initial part of an otherwise narrow QRS of a patient at risk for WPW and is an indicator of the presence of an accessory pathway. These beats are a fusion between the conduction down the accessory pathway and the slightly delayed but then-dominant conduction via the AV node. Once an antidromic AVRT tachycardia is initiated, it is no longer delta waves but rather a wide complex (>120 ms) tachycardia that is seen. * Finally, junctional ectopic tachycardia (JET) is a rare tachycardia caused by increased automaticity of the AV node itself initiating frequent heartbeats. On the ECG, junctional tachycardia often presents with abnormal morphology P-waves that may fall anywhere in relation to a regular, narrow QRS complex. It is often due to drug toxicity. Classification Impulse arising in SA node, traversing atria to AV node, then entering ventricle. Rhythm originating at or above AV node constitutes<unk> . Atrial fibrillation: Irregular impulses reaching AV node, only some being transmitted. The following types of<unk> s are more precisely classified by their specific site of origin. While each belongs to the broad classification of<unk> , the specific term/diagnosis is preferred when possible: Sinoatrial origin: * Sinoatrial nodal reentrant tachycardia (SNRT) Atrial origin: * Ectopic (unifocal) atrial tachycardia (EAT) * Multifocal atrial tachycardia (MAT) * Atrial fibrillation with rapid ventricular response * Atrial flutter with rapid ventricular response :(Without rapid ventricular response, fibrillation and flutter are usually not classified as<unk>  Atrioventricular origin: * AV nodal reentrant tachycardia (AVNRT) or junctional reciprocating tachycardia (JRT) * AV reciprocating tachycardia (AVRT) – visible or concealed (including Wolff-Parkinson-White syndrome) * Permanent (or persistent) junctional reciprocating tachycardia (PJRT), a form of<unk>  that involves a slow retrograde conduction over accessory pathway - occurs predominantly in infants and children but can occasionally occur in adults * Junctional ectopic tachycardia (JET)
Supraventricular tachycardia
Tachycardia
Sinus arrhythmia
Ventricular tachycardia
Junctional tachycardia
Ectopic beat
Inappropriate sinus tachycardia
Ventricular flutter