Category:Sinus Cardiac Rhythms

Types of Sinus Cardiac Rhythms

1. Sinus Rhythms

2. Sinus Arrhythmias

• Normal arrhythmia in dogs associated with respiration (heart rate increases with inspiration and decreases with expiration).

• The associated changes in P wave height with respiration are called a wandering pacemaker.

3. Sinus Bradycardias

• Characterised as a normal sinus rhythm with an abnormally slow heart rate

• Caused by: pathologic conditions, drug reactions, physiologic conditions: athletic animals, calm animals, sleeping animals

Treatment: Usually unnecessary unless clinical signs due to reduced cardiac output remain

• Treat the underlying condition

• Drugs used to treat sinus bradycardias: atropine, isoprenaline, glycopyrrolate

4. Sinus Tachycardia

• Characterised as a normal sinus rhythm with an abnormally fast heart rate

• Caused by: pathological conditions, drug reactions, physiologic conditions: pain, exercise, excitement

Treatment: Usually unnecessary unless clinical signs remain

• Treat the underlying condition

5. Sinus Arrest & Sinus Block

• Sinus arrest occurs when the sinoartial node fails to discharge resulting in a pause of the normal heart rhythm.

• Sinus block occurs when the sinoatrial node fails to conduct the wave of depolarisation resulting in a pause of the normal heart rhythm.

• The presence of a sinus arrest on an ECG would be characterised by an absence of P-QRS-T complexes for more than two R-R intervals.

• The presence of a sinus block on an ECG would be characterised by an absence of P-QRS-T complexes for twice the R-R interval.

Treatment:

• Treat the underlying condition

• Drugs used in the treatment of sinus arrest and sinus blocks are the following: glycopyrrolate, isoprenaline, atropine