Sinus Rhythms Chapter 13

Normal Sinus Rhythm Autonomic Nervous System Sympathetic nerves Parasympathetic nerves (vagus nerve) Autonomic Nervous System Sympathetic nerves Parasympathetic nerves (vagus nerve)

Sympathetic Stimulation Increase in HR Palpitations pounding normal, premature beats, or ectopic (non- sinus) beats, Increase in HR Palpitations pounding normal, premature beats, or ectopic (non- sinus) beats,

Tachycardia HR exceeding 100 beats/min Increase SNS and/or decrease in PNS Elderly individuals rarely show HR greater than bpm HR above this range usually indicate non-sinus tachycardia (e.g. atrial fibrillation or a paroxysmal supraventricular tachycardia) HR exceeding 100 beats/min Increase SNS and/or decrease in PNS Elderly individuals rarely show HR greater than bpm HR above this range usually indicate non-sinus tachycardia (e.g. atrial fibrillation or a paroxysmal supraventricular tachycardia)

Sinus Tachycardia P Wave - Visible before each QRS complex P-R Interval - Normal QRS Duration - Normal Rhythm - Regular Rate - More than 100 beats per minute P Wave - Visible before each QRS complex P-R Interval - Normal QRS Duration - Normal Rhythm - Regular Rate - More than 100 beats per minute

Tachycardia Each QRS complex is preceded by a P wave With a very fast rate, the P wave may merge with the preceding T wave Each QRS complex is preceded by a P wave With a very fast rate, the P wave may merge with the preceding T wave

Tachycardia Anxiety, exertion, pain, Drugs: increase SNS or decrease vagal tone Fever Congestive heart failure Pulmonary embolism Acute MI Hyperthyrodism Pheochromocytoma Blood loss Alcohol intoxication Anxiety, exertion, pain, Drugs: increase SNS or decrease vagal tone Fever Congestive heart failure Pulmonary embolism Acute MI Hyperthyrodism Pheochromocytoma Blood loss Alcohol intoxication

Sinus Bradycardia Heart rate less than 60 bpm

Sinus Bradycardia P Wave - Visible before each QRS complex P-R Interval - Normal QRS Duration - Normal Rhythm - Regular Rate - less than 60 beats per minute Usually benign and often caused by patients on beta blockers P Wave - Visible before each QRS complex P-R Interval - Normal QRS Duration - Normal Rhythm - Regular Rate - less than 60 beats per minute Usually benign and often caused by patients on beta blockers

Sinus Bradycardia Normal variant Drugs: decrease SNS or increase vagal tone Hypothyroidism Hyperkalemia Sick sinus syndrome (Fig 13-5) Sleep apnea Carotid sinus hypersensitivity syndrome Vasovagal reactions Normal variant Drugs: decrease SNS or increase vagal tone Hypothyroidism Hyperkalemia Sick sinus syndrome (Fig 13-5) Sleep apnea Carotid sinus hypersensitivity syndrome Vasovagal reactions

Sinus Bradycardia Symptoms Moderate sinus bradycardia produces no symptoms If HR is very slow, lightheadedness and syncope Symptoms Moderate sinus bradycardia produces no symptoms If HR is very slow, lightheadedness and syncope

Sinus Arrhythmia Beat to beat variation in HR Younger, healthy individuals Common cause: respiration Respiratory sinus arrhythmia Beat to beat variation in HR Younger, healthy individuals Common cause: respiration Respiratory sinus arrhythmia

Sinus Pauses/Sinus Arrest SA fails to stimulate the atria Sinus pause or sinus arrest (Fig. 13-5) SA fails to stimulate the atria Sinus pause or sinus arrest (Fig. 13-5)

Escape Beats Escape beat (Fig. 13-6) Atria, AV node or ventricles Escape beat (Fig. 13-6) Atria, AV node or ventricles

Sinus Pauses/Sinus Arrest Causes of sinus pause or arrest hypoxemia Ischemia or MI Hyperkalemia Drug toxicity Vagal hyperreactivity Sick sinus syndrome (Fig 13-5) Causes of sinus pause or arrest hypoxemia Ischemia or MI Hyperkalemia Drug toxicity Vagal hyperreactivity Sick sinus syndrome (Fig 13-5)