Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:

Sinus Tachycardia:

Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute. The ECG shows normal P waves preceding each QRS complex, with a normal PR interval. The condition arises from the sinus node firing more rapidly due to various stimuli such as fever, exercise, or stress.

Premature Atrial Contraction (PAC):

PACs are early beats originating from an ectopic focus in the atria. The ECG typically shows early P waves that differ in shape from the sinus P waves and may be hidden in the preceding T wave. The heart rate varies based on the frequency of PACs, and the rhythm is generally irregular.

Atrial Flutter:

This condition involves a single reentrant circuit in the atria, causing rapid, regular atrial contractions with a rate of 200-350 beats per minute. The ECG shows a characteristic sawtooth pattern known as flutter waves. The ventricular rate depends on the degree of AV block and can vary.

Atrial Fibrillation (AF):

AF is marked by chaotic electrical activity in the atria, leading to an irregular heartbeat. The ECG shows no distinct P waves, only fibrillatory waves, with an atrial rate ranging from 350 to 600 beats per minute. Depending on the condition, the ventricular response can be controlled or rapid.

Paroxysmal Supraventricular Tachycardia (PSVT):

PSVT is characterized by sudden episodes of rapid heart rate due to reentrant circuits or abnormal electrical pathways above the ventricles. The ECG typically shows a regular, narrow QRS complex tachycardia with a rate of 150-250 beats per minute. P waves may be hidden or occur shortly after the QRS complex.

Ventricular Tachycardia (VT):

VT involves a rapid heart rate of 150-250 beats per minute originating from the ventricles. The ECG shows wide and distorted QRS complexes, and the rhythm may be regular or irregular. It can be monomorphic (consistent QRS shape) or polymorphic (variable QRS shapes).

Ventricular Fibrillation (VF):

VF is a life-threatening condition where the ventricles quiver ineffectively due to chaotic electrical activity. The ECG displays irregular, disorganized waveforms of varying amplitude and shape. This condition requires immediate medical intervention.