Stephanie Sutton RN, CNRN CARDIAC REVIEW Stephanie Sutton RN, CNRN January 2014

Cardiac Conduction http://www.youtube.com/watch?v=v3b-YhZmQu8

Measurements Baseline – Isoelectric line Wave above baseline (+) Wave below baseline (-) Cardiac cycle = a single heartbeat Consists of P, Q, R, S, T & Baseline Measured from beginning of one P wave to the beginning of the next P wave

P Waves Normal = well rounded and 2 small boxes or less in height Abnormal Peaked – enlargement of right atria Notched – enlargement of left atria Negative or absent – electrical conduction initiated from AV junction Bisphasic or diphasic – enlargement of both atria – only seen with a 12 lead

PR Interval Measured from beginning of P wave to the beginning of next deflection on baseline Normal 0.12 to 0.20 seconds (3-5 small graph squares) Abnormal PRI – disturbance in the electrical conduction pathway

QRS Complex Normal <0.12 second (3 small boxes) >0.12 indicates a disturbance in the electrical conduction pathway

ST Segment Portion from end of the S wave to beginning of T wave May be flat, elevated, or depressed Only used diagnostically in 12-lead EKG

T Wave May be above or below the isoelectric line T wave > half the height of QRS complex = elevated or peaked – may indicate ischemia of cardiac muscle Depressed or Inverted T wave follows an upright QRS complex, but is below the isoelectric line – usually indicative of previous cardiac ischemia Flat T wave, or bisphasic/diphasic (seen both above and below isoelectric line) could indicate ischemia or changes in K+ levels

P to P Intervals R to R Intervals Length of time from one P wave to the next P wave R to R interval Length of time from the peak of one R wave to the peak of the next R wave Measurements of these intervals are used to determine if the rhythm of a strip is regular or irregular

QT Interval Measured from the beginning of the QRS complex to the end of the T wave Normal = less than ½ the R to R interval of that complex and the R wave of the following complex Prolonged = greater than ½ the R to R interval of that complex and the R wave of the following complex OR > 0.44 second Usually indicates a problem with the electrical conduction pathway of the heart

Normal Sinus Rhythm 60-100 bpm

Sinus Bradycardia slower than 60 bpm May be normal in athletes, or during sleep Common causes: vomiting, drugs – digitalis, morphine, sedatives s/s poor cardiac output – pale, cool, clammy skin; cyanosis; dyspnea; confusion or disorientation; dizziness; weakness or faintness; sudden decrease in BP; shortness of breath; n/v; decreased urine output; chest pain; unresponsiveness, increased ICP May be normal in athletes, or during sleep Common causes: vomiting, drugs – digitalis, morphine, sedatives s/s poor cardiac output – pale, cool, clammy skin; cyanosis; dyspnea; confusion or disorientation; dizziness; weakness or faintness; sudden decrease in BP; shortness of breath; n/v; decreased urine output; chest pain; unresponsiveness, increased ICP

Sinus Tachycardia 101-150 bpm As rate of tachycardia increases, P waves frequently hidden in preceding T wave Causes – pain, fever, anemia, dehydration, hemorrhage, exercise, fear, sudden excitement, anxiety, effects of drugs (atropine, nicotine, caffeine, street drugs) Causes – pain, fever, anemia, dehydration, hemorrhage, exercise, fear, sudden excitement, anxiety, effects of drugs (atropine, nicotine, caffeine, street drugs)

Sinus Arrhythmia SA node initiates all the electrical impulses, but at irregular intervals P to P and R to R intervals change with respirations, especially in children and elderly Rate usually 60-100 bpm

Heart Blocks http://www.youtube.com/watch?v=3NgiiMHUrfQ

Practice #1 2nd degree type 1 – Wenkebach

Practice #2 1st degree

Practice #3 Complete heart block

Practice #4 2nd degree mobitz 2

Bundle Branch Block Commonly occurs with CAD Wide or notched QRS

PAC’s contraction occurs before expected Irregular rhythm May precede PSVT, a fib, a flutter

PVC’s Uniform or multiform Usually followed by a compensatory pause Patient’s may feel “skipped beat” Irregular rhythm

Supraventricular Tachycardia Rate 150-250 bpm P waves can be buried in T waves Cannot measure PR interval QRS usually normal r/t caffeine, nicotine, stress, anxiety s/s angina, hypotension, light-headed, palpitations, anxiety r/t caffeine, nicotine, stress, anxiety s/s angina, hypotension, light-headed, palpitations, anxiety

Atrial Fibrillation Atrial rate >= 350 bpm, ventricular rate varies Rapid, erratic electrical discharge from multiple atrial ectopic foci No organized atrial depolarization Absent P waves No PR interval Normal QRS Rapid, erratic electrical discharge from multiple atrial ectopic foci No organized atrial depolarization

Atrial Flutter Atrial rate 250-350 bpm, ventricular rate varies Flutter waves, saw toothed appearance; may be buried in QRS PR interval varies May have widened QRS

Junctional Arrythmias Atria & SA node not functioning properly Junctional escape rhythm Rate 40-60 bpm P waves absent, inverted, buried, or retrograde PR interval short, none, retrograde

Ventricular Tachycardia Both: rate 100-250 bpm May be perfusing or non perfusing Monomorphic QRS uniform Polymorphic QRS varies

Torsades de Pointes French for “twisting of points” Polymorphic VT with long QT intervals Causes: drugs that prolong QT interval and electrolyte abnormalities may convert to VF or asystole

Ventricular Fibrillation Chaotic electrical activity – no ventricular depolarization or contraction No pulse or cardiac output – requires rapid intervention! Coarse Fine

Pulseless Electrical Activity Monitor shows electrical rhythm, but no pulse present May be sinus, atrial, junctional, or ventricular Causes: trauma, tension pneumothorax, thrombosis, cardiac tamponade, toxins, hypovolemia, hypoxia, hypoglycemia, hypothermia, acidosis, hypo or hyperkalemia

Asystole No electrical activity in ventricles

Pacemakers Atrial Ventricular A/V Spike preceeds P wave Spike followed by QRS A/V

Practice #1 Polymorphic V tach

Practice #2 junctional

Practice #3 What kind of pacing? V paced

Practice #4 Atrial tachycardia

Practice #5 2nd degree type 1 – Wenkebach

Practice #6 Bundle branch block

Practice #7 Sinus brady