Tachycardia | Definition | Features

Welcome to our Tachycardia Reference Page. This page provides a summary definition followed by introductions to our practice drills, quizzes, lessons and interactive guides.


Tachycardia is a rapid, above normal, heart rate when the subject is at rest. A resting heart rate that exceeds one hundred beats per minute can be classified as tachycardia.


Tachycardias can be classified by their origin (atria or ventricles). Ventricular tachycardia originates in the ventricles and includes the follow abnormalities:

  • Ventricular fibrillation is a rapid and chaotic cardiac rhythm. The ventricles quiver rather than pump, which diminished blood pressure and flow. Ventricular fibrillation demands immediate emergency medical attention.
  • Long QT syndrome is an abnormal EKG pattern that reflects disorder of the heart's electrical signals resulting in fast and chaotic heartbeats. During exercise or stress, long QT syndrome can cause dangerous arrhythmias.
  • Premature ventricular contractions are abnormal (and extra) heartbeats that originate in the ventricles. This abnormality is also called PVC or Premature Ventricular Complex. It is fairly common abnormality.

Supraventricular tachycardias originate above the ventricles. They include:

  • Atrial flutter, a rapid heart beat, but not as chaotic as atrial fibrillation.
  • Supraventricular tachycardia, originating above the ventricles, it can last for seconds to hours. Several types of supraventricular tachycardia can be diagnosed.
  • Atrial fibrillation, which is a chaotic, fast heart rhythm. Fairly common. Risk of developing atrial fibrillation increases with age.
  • Wolff-Parkinson-White syndrome, which occurs when a second electrical pathway between atria and ventricles bypasses the atrioventricular node.

Diagnosis - Overview

Several types of tests may be employed to diagnose tachycardia: electrocardiograms, holter monitors, event monitors, stress tests, echocardiograms, electrophysiology studies, head-up-tilt-table tests and cardiac catheterization. On this website you will find provide tools for heart sounds and electrocardiograms.


If you wish to practice taking pulse rate, use our blood pressure case studies.

Heart Sounds

Using the play button on the torso, you can listen to tachycardia. For more information, lessons and quizzes for heart sounds, visit our page: Heart Sounds

torso with stethoscope chestpiece


EKG tracings also can reveal tachycardia. The rhythm strip below show several types of tachycardia:

ekg tracing of tachycardia

Additional Tachycardia EKGs

Junctional Tachycardia

ekg tracing of junctional tachycardia
Rhythm Regular
Rate Fast (100-180 bpm)
P Wave Present before, during (hidden) or after QRS, if visible it is inverted
PR Interval Absent or short
QRS Normal (0.06-0.10 sec)

Supraventricular Tachycardia

ekg tracing of supraventricular tachycardia
Rhythm Regular
Rate Fast (150-250 bpm)
P Wave Merged with T wave
PR Interval Normal (0.12 sec)
QRS Normal (.10 sec)
Notes PR interval can be difficult to measure

Ventricular Tachycardia

ekg tracing of ventricular tachycardia
Rhythm Regular
Rate Fast (100-250 bpm)
P Wave Absent
PR Interval Not measurable
QRS Wide (>0.10 sec), bizarre appearance

Multifocal Atrial Tachycardia

ekg tracing of multifocal atrial tachycardia
Rhythm Irregular
Rate Fast (> 100 bpm)
P Wave Often changing shape and size from beat to beat (at least three differing forms)
PR Interval Variable
QRS Normal (0.06-0.10 sec)
Notes T wave is often distorted Also review wandering atrial pacemaker lesson

Sinus Tachycardia

ekg tracing of sinus tachycardia
Rhythm Regular
Rate Fast (> 100 bpm)
P Wave Normal, may merge with T wave at very fast rates
PR Interval Normal (0.12-0.20 sec)
QRS Normal (0.06-0.10 sec)
Notes QT interval shortens with increasing heart rate

EKG Training - Introduction

A good starting point for learning EKG interpretation is our EKG Basics training course. The course provides training on the key features of an EKG tracing. These features include observing P-wave forms, measurement of EKG intervals and segments, assessment of rhythm, calculating heart rate, and the evaluation of other relevant wave segments. The arrhythmia practice drills allow students to build skills interactively.

EKG Basics

EKG Practice Drills

The heart arrhythmia practice drills provide a test EKG tracing and users are asked to identify the type of arrhythmia. Many of these drills include tachycardia EKG tracings. Each answer is immediately evaluated and the correct classification of the EKG tracing is provided, along with a detailed explanation. A directory of arrhythmias is also provided.

Arrhythmia Practice Drills

ECG Quiz

The quiz is structured like a classroom exam. The quiz present twenty EKGs. Users answer each question and at the end of the quiz, a fully graded report is provided. This graded report provides scoring as well as the correct answer to each question. Top scores and mean scores are also provided. This quiz draws its questions from a library of over 300 EKGs, allowing users to take the quiz multiple times.

ECG Quiz

ECG Monitor Challenge (beta version)

Try the beta version of our ECG monitor challenge. This quiz uses a simulated patient monitor with moving waveform instead of a paper tracing. As with the quiz described above, twenty questions are presented, then a graded report is available.

ECG Monitor Challenge

External References


Authors and Contributors

  • Dr. Jon Keroes
  • David Lieberman
  • Tom O'Brien
  • Dr. Barbara Erikson