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Sinus Rhythms. Chapter 13. Normal Sinus Rhythm. Autonomic Nervous System Sympathetic nerves Parasympathetic nerves (vagus nerve). Sympathetic Stimulation. Increase in HR Palpitations pounding normal, premature beats, or ectopic (non-sinus) beats,. Tachycardia.
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Sinus Rhythms • Chapter 13
Normal Sinus Rhythm • Autonomic Nervous System • Sympathetic nerves • Parasympathetic nerves (vagus nerve)
Sympathetic Stimulation • 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 140-150 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
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
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
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
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
Sinus Bradycardia • 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
Sinus Pauses/Sinus Arrest • 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
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)