Critical Care | 126 Questions and Answers Graded A+

P wave - Depolarization of the atria PR interval - -Normal is 0.12 to 0.2 seconds - onset of atrial depolarization until onset of ventricular polarization QRS complex - -Normal is 0.06 to 0.11 seconds -Ventricular depolarization -systole T wave - -appears after QRS complex - Ventricular repolarization -Spiked T-wave occurs with hyperkalemia U wave - - repolarization of the purkinje fibers - seen in patients with hypokalemia SA node - the pace-maker of the heart; where the impulse conduction of the heart usually starts; located in the top of the right atrium just below superior vena cava *sends impulses 60-100 BPM Normal Sinus Rhythm - Rate is 60-100/ minute Rhythm is regular P wave present PR interval: normal 0.12-0.20 QRS complex:normalInterpretation: normal sinus rhythm normal QRS: 0.06- 0.10 Sinus Bradycardia - Rate is <60/minute Rhythm is regular P wave present PR interval: normal 0.12-0.20 QRS complex:normal Interpretation: treat sinus brady with *0.5mg atropine ( if emergent)* , dopamine, epinephrine, pacer. *normal in patients when sleeping or sleeping -may occur with use of Beta blockers or calcium channel blockers, digoxin, morphine, vagal stimulation, hypothermia, hypothroidism Sinus Tachycardia - Rate is >100/min (usually below 160) Rhythm is regular P wave present PR interval: normal 0.12-0.20 QRS complex:normal 0.6-0.10 Interpretation: correct the underlying cause, adminster beta blockers or calcium channel blockers. *treat underlying cause.** - may be a normal response from a fever, exercise, anxiety, pain, dehydration. May accompany shock, LHF, hyperthyroidism, anemia, hypovolemia, PE, MI -can be caused by caffiene, nicotine, amphetemines, atropine, cocaine.Sinus Arrhythmia - Rate: increases on inspiration, decreases on expiration Rhythm: *Always has irregular rhythm* P waves?: yes PR interval: normal QRS: normal Significance: usually a normal finding and usually is *not treated