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Determine the following:

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

Rhythm: _______________________________________


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 seconds


QRS complex: 0.04 to 0.06 seconds


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


* 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 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 seconds)


QRS complex: Normal (0.10 seconds or less)