Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. Heart rates above the resting rate may be normal (such as with exercise) or abnormal (such as with electrical problems within the heart).

Complications

Tachycardia can lead to fainting.

When the rate of blood flow becomes too rapid, or fast blood flow passes on damaged endothelium, it increases the friction within vessels resulting in turbulence and other disturbances. According to the Virchow's triad, this is one of the three conditions (along with hypercoagulability and endothelial injury/dysfunction) that can lead to thrombosis (i.e., blood clots within vessels).

Causes

Some causes of tachycardia include:

  • Adrenergic storm
  • Anaemia
  • Anxiety
  • Atrial fibrillation
  • Atrial flutter
  • Atrial tachycardia
  • Atrioventricular reentrant tachycardia
  • AV nodal reentrant tachycardia
  • Brugada syndrome
  • Circulatory shock and its various causes (obstructive shock, cardiogenic shock, hypovolemic shock, distributive shock)
  • Dehydration
  • Dysautonomia
  • Exercise
  • Fear
  • Hypoglycemia
  • Hypovolemia
  • Hyperthyroidism
  • Hyperventilation
  • Inappropriate sinus tachycardia
  • Junctional tachycardia
  • Metabolic myopathy
  • Multifocal atrial tachycardia
  • Pacemaker mediated
  • Pain
  • Panic attack
  • Pheochromocytoma
  • Sinus tachycardia
  • Sleep deprivation
  • Supraventricular tachycardia
  • Ventricular tachycardia
  • Wolff–Parkinson–White syndrome

Drug related:

  • Alcohol (ethanol) intoxication
  • Stimulants
  • Cannabis
  • Drug withdrawal
  • Tricyclic antidepressants
  • Nefopam
  • Opioids (rare)

Diagnosis

The upper threshold of a normal human resting heart rate is based on age. Cutoff values for tachycardia in different age groups are fairly well standardized; typical cutoffs are listed below:

  • 1–2 days: >159 beats per minute (bpm)
  • 3–6 days: >166 bpm
  • 1–3 weeks: >182 bpm
  • 1–2 months: >179 bpm
  • 3–5 months: >186 bpm
  • 6–11 months: >169 bpm
  • 1–2 years: >151 bpm
  • 3–4 years: >137 bpm
  • 5–7 years: >133 bpm
  • 8–11 years: >130 bpm
  • 12–15 years: >119 bpm
  • 15 years–adult: Tachycardia >100 bpm

Heart rate is considered in the context of the prevailing clinical picture. When the heart beats excessively or rapidly, the heart pumps less efficiently and provides less blood flow to the rest of the body, including the heart itself. The increased heart rate also leads to increased work and oxygen demand by the heart, which can lead to rate related ischemia.

Differential diagnosis

thumb|12 lead [[electrocardiogram showing a ventricular tachycardia (VT)]]

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 in order of most to least common, they are: Metabolic myopathies interfere with the muscle's ability to create energy. This energy shortage in muscle cells causes an inappropriate rapid heart rate in response to exercise. The heart tries to compensate for the energy shortage by increasing heart rate to maximize delivery of oxygen and other blood borne fuels to the muscle cells. As skeletal muscle relies predominantly on glycogenolysis for the first few minutes as it transitions from rest to activity, as well as throughout high-intensity aerobic activity and all anaerobic activity, individuals with GSD-V experience during exercise: sinus tachycardia, tachypnea, muscle fatigue and pain, during the aforementioned activities and time frames. The upper limit of normal rate for sinus tachycardia is thought to be 220 bpm minus age.

Inappropriate sinus tachycardia

Inappropriate sinus tachycardia (IST) is a diagnosis of exclusion, a rare but benign type of cardiac arrhythmia that may be caused by a structural abnormality in the sinus node. It can occur in seemingly healthy individuals with no history of cardiovascular disease. Other causes may include autonomic nervous system deficits, autoimmune response, or drug interactions. Although symptoms might be distressing, treatment is not generally seen by clinicians as needed.

Ventricular

Ventricular tachycardia (VT or V-tach) is a potentially life-threatening cardiac arrhythmia that originates in the ventricles. It is usually a regular, wide complex tachycardia with a rate between 120 and 250 beats per minute. A medically significant subvariant of ventricular tachycardia is called torsades de pointes (literally meaning "twisting of the points", due to its appearance on an EKG), which tends to result from a long QT interval.

Both of these rhythms normally last for only a few seconds to minutes (paroxysmal tachycardia), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation.

Supraventricular

This is a type of tachycardia that originates from above the ventricles, such as the atria. It is sometimes known as paroxysmal atrial tachycardia (PAT). Several types of supraventricular tachycardia are known to exist.

Atrial fibrillation

Atrial fibrillation is one of the most common cardiac arrhythmias. In general, it is an irregular, narrow complex rhythm. However, it may show wide QRS complexes on the ECG if a bundle branch block is present. At high rates, the QRS complex may also become wide due to the Ashman phenomenon. It may be difficult to determine the rhythm's regularity when the rate exceeds 150 beats per minute. Depending on the patient's health and other variables such as medications taken for rate control, atrial fibrillation may cause heart rates that span from 50 to 250 beats per minute (or even higher if an accessory pathway is present). However, new-onset atrial fibrillation tends to present with rates between 100 and 150 beats per minute.

AV nodal reentrant tachycardia

AV nodal reentrant tachycardia (AVNRT) is the most common reentrant tachycardia. It is a regular narrow complex tachycardia that usually responds well to the Valsalva maneuver or the drug adenosine. However, unstable patients sometimes require synchronized cardioversion. Definitive care may include catheter ablation.

AV reentrant tachycardia

AV reentrant tachycardia (AVRT) requires an accessory pathway for its maintenance. AVRT may involve orthodromic conduction (where the impulse travels down the AV node to the ventricles and back up to the atria through the accessory pathway) or antidromic conduction (which the impulse travels down the accessory pathway and back up to the atria through the AV node). Orthodromic conduction usually results in a narrow complex tachycardia, and antidromic conduction usually results in a wide complex tachycardia that often mimics ventricular tachycardia. Most antiarrhythmics are contraindicated in the emergency treatment of AVRT, because they may paradoxically increase conduction across the accessory pathway.

Junctional tachycardia

Junctional tachycardia is an automatic tachycardia originating in the AV junction. It tends to be a regular, narrow complex tachycardia and may be a sign of digitalis toxicity.

Management

The management of tachycardia depends on its type (wide complex versus narrow complex), whether or not the person is stable or unstable, and whether the instability is due to the tachycardia. But, if the cause of the tachycardia is chronic (permanent), it would return after some time, unless that cause is corrected.

Besides, the patient should avoid receiving external effects that cause or increase tachycardia.

The same measures as in unstable tachycardia can also be taken, with medications and the type of cardioversion that is appropriate for the patient's tachycardia. 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.