Cardiopulmonary Anatomy and Physiology: Essentials of Respiratory

Cardiopulmonary Anatomy and Physiology: Essentials of Respiratory Care (6th Edition) | Test Bank ventricular HR is regular - anscount the # of large squares between two consecutive QRS complexes & then dividing 300 by the # of large squares ventricular HR irregular - anscounting the # of QRS complexes in a 6 second interval, then multiply the # by 10 Normal adult HR - ans60-100 bpm HR less than 60 bpm - ansbradycardia HR greater than 100 bpm - anstachycardia a variation of 0.12 or less is - ansa regular rhythm QRS complex that is narrow & lasts 0.10 second or less represents - anssupraventricular origin QRS complex greater than 0.10 second & the shape is distorted, - ansthen an abnormal electrical source is likely to be present within the ventricle most common cardiac dysrhythmias - anssinus mechanisms, atrial mechanisms, ventricular mechanisms, & AV conduction defects sinus bradycardia - ans"slow heart" QRS rate - less than 60 bpm sinus tachycardia - ans"fast heart" QRS rate- 100-160 bpm sinus arrhythmia - ansQRS rate - varies by more than 10% QRS rhythm - Irregular Normal in children & young adults sinus block (sinus exit block) P wave- The P waves are positive & uniform; however, an entire P-QRS-T complex is missing PR Interval- Normal except for the pause when an entire cycle is missing. The PR interval may be slightly shorter after the pause. QRS complex- Except for the missing cycle QRS rate- Rate may vary according to the number & position of missing P-QRS-T cycles - ansQRS rhythm- The rhythm may be regular or irregular according to the number & position of missing P-QRS-T SA node initiates an impulse but the electrical current through the atria is blocked. The atria and the ventricles do not depolarize or contract, resulting in no P wave or QRS complex. The next P-QRS-T complex, however, appears at the precise times it would normally appear if the sinus block had not occurred. In other words, the ECG shows that the heart has skipped a beat. sinus arrest (SA node arrest) is a sudden failure of the SA node to initiate an impulse(no P wave). It is common to see two, three, or four P-QRS-T complexes missing following a normal P-QRS-T complex. When the sinus arrest is excessively long, the AV node usually takes over & initiates a new (but slower) rhythm called an escape rate. - ansP wave- No P wave QRS complex- After a sinus arrest, however, the QRS duration may be greater than 0.12 second when the escape rhythm is initiated by the AV node. QRS rate- Normal sinus rhythm during nonsinus arrest periods QRS rhythm- QRS complexes before & after the sinus arrest are regular. The escape rate may be regular or irregular Premature Atrial Complex (PAC) results when abnormal electrical activity in the atria causes the atria to depolarize before the SA node fires QRS complex- Except for the abnormal cycle generated by the P' wave. QRS rate- varies QRS rhythm- irregular - ansP wave- P' will appear different than a normal SA node induced P wave. The P' may be hidden in the preceding T wave. P' waves hidden in the T waves often distort or increase the amplitude of the T wave. A PAC may not successfully move into the ventricles if the AV node or bundle branches are in their complete refractory period. This is called a blocked or nonconducted PAC. PR Interval- Normal or prolonged depending on the timing of PAC. P'R interval is different from the normal SA node rhythm. An electrical current that originates outside the SA node is called - ansand ectopic focus An ectopic focus in the atria results in - ansa P prime (P')