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Determine the following:

Rhythm: _______________________________________

  
Figure. No caption a... - Click to enlarge in new windowFigure. No caption available.

Rate: _______________________________________

 

P waves: _______________________________________

 

PR interval: _______________________________________

 

QRS complex: _______________________________________

 

What's your interpretation?

(Answers on next page)

 

Name that strip: Answers

Rhythm: Regular

 

Rate: 125 beats/minute

 

P waves: Sinus

 

PR interval: 0.12 to 0.14 second

 

QRS complex: 0.04 to 0.06 second

 

Interpretation: Sinus tachycardia

 

Sinus tachycardia is a normal response of the heart to the body's demand for increased blood flow. The sinus node increases its rate in response to the needs of the body. When these needs no longer exist, the heart rate slows down.

 

Sinus tachycardia begins and ends gradually, in contrast to other tachycardias that begin and end suddenly. Sinus tachycardia may occur with any of the following:

 

* exercise or physical exertion

 

* intake of stimulants such as caffeine, nicotine, cocaine, or amphetamines

 

* drug withdrawal

 

* increase in catecholamine release resulting from anxiety, excitement, pain, or stress

 

* increased metabolic states such as hyperthermia or hyperthyroidism

 

* fever and sepsis

 

* anemia

 

* hypoxemia, hypovolemia, hypotension or shock, heart failure

 

* myocardial ischemia or acute myocardial infarction

 

* pulmonary embolism

 

* drugs that increase sympathetic tone such as I.V. epinephrine and I.V. dopamine or drugs that decrease parasympathetic tone, such as I.V. atropine.

 

 

An increased heart rate increases myocardial workload and oxygen consumption and may cause a decreased stroke volume leading to decreased cardiac output. In addition, heart rates higher than normal decrease the amount of time the heart spends in diastole, leading to a decrease in coronary artery blood flow, which occurs mostly during diastole, and myocardial perfusion.

 

Sinus tachycardia is usually a benign dysrhythmia that resolves on its own. Treatment is directed at correcting the underlying cause. Simple therapies such as treatment of pain, anxiety, fever, hypoxemia, or volume replacement may be all that is needed to resolve the dysrhythmia. Persistent sinus tachycardia may require more aggressive evaluation and treatment.

 

Sinus tachycardia: Identifying ECG features

Rhythm: Regular

 

Rate: 100 to 160 beats/minute

 

P waves: Normal in size, shape, and direction; positive in lead II; one P wave precedes each QRS complex

 

PR interval: Normal (0.12 to 0.20 second)

 

QRS complex: Normal (0.10 second or less)