Heart Model
Cardiovascular Physiology Concepts Richard E. Klabunde, PhD

Cardiovascular Physiology Concepts 3e textbook cover Cardiovascular Physiology Concepts, 3rd edition textbook, Published by Wolters Kluwer (2021)

CNormal and Abnormal Blood Pressure, Physiology, Pathophysiology and Treatment book cover Normal and Abnormal Blood Pressure, published by Richard E. Klabunde (2013)

Abnormal Rhythms - Definitions

General Terms:

Normal sinus rhythm – heart rhythm controlled by sinus node at 60-100 beats/min; each P wave followed by QRS and each QRS preceded by a P wave.

Bradycardia – a heart rate that is lower than normal.

Tachycardia – a heart rate that is higher than normal.

Paroxysmal – an arrhythmia that suddenly begins and ends.

Specific Arrhythmias:

Sinus bradycardia – low sinus rate <60 beats/min.

Sinus tachycardia – high sinus rate of 100-180 beats/min as occurs during exercise or other conditions that lead to increased SA nodal firing rate.

Sick sinus syndrome – a disturbance of SA nodal function that results in a markedly variable rhythm (cycles of bradycardia and tachycardia).

Atrial tachycardia – a series of 3 or more consecutive atrial premature beats occurring at a frequency >100/min; usually because of abnormal focus within the atria and paroxysmal in nature, therefore the appearance of P wave is altered in different ECG leads.  This type of rhythm includes paroxysmal atrial tachycardia (PAT).

Atrial flutter – sinus rate of 250-350 beats/min.

Atrial fibrillation – uncoordinated atrial depolarizations.

Junctional escape rhythm – SA node suppression can cause AV node-generated rhythm of 40-60 beats/min (not preceded by P wave).

AV nodal blocks –  a conduction block within the AV node (or occasionally in the bundle of His) that impairs impulse conduction from the atria to the ventricles.

Supraventricular tachycardia (SVT) – usually caused by reentry currents within the atria or between ventricles and atria producing high heart rates of 140-250; the QRS complex is usually normal width, unless there are also intraventricular conduction blocks (e.g., bundle branch block).

Ventricular premature beats (VPBs) – caused by ectopic ventricular foci; characterized by widened QRS; often referred to as a premature ventricular complex, or PVC. Note the wide and abnormally shaped QRS that is generated prematurely in the following ECG rhythm strip:
Ventricular premature beat

Ventricular tachycardia (VT) – high ventricular rate caused by aberrant ventricular automaticity (ventricular foci) or by intraventricular reentry can be sustained or nonsustained (paroxysmal). They are typically characterized by widened QRS (>0.14 sec); rates of 100 to 280 beats/min; life-threatening.

Ventricular flutter – very rapid ventricular depolarizations >250/min; sine wave appearance; leads to fibrillation.

Ventricular fibrillation – uncoordinated ventricular depolarizations; leads to death if not quickly converted to a normal rhythm or at least a rhythm compatible with life.

For information on the pharmacologic treatment of arrhythmias, go to: cvpharmacology.com/antiarrhy/antiarrhythmic.

Revised 11/01/2023

Be sure to visit our sister site, CVPharmacology.com.

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