Understanding EKG Rhythms

Objectives

• Understand rate calculation
• Understand the basics of reading a rhythm strip/EKG
• Learn to identify supraventricular and ventricular rhythms
• Learn basics of EKG/rhythm strip changes related to ischemia and infarction

Normal Waveform Review

• Segment is a part of the EKG
• Interval is a measurement in the EKG
• P-Wave signifies atrial depolarization
• Normal duration of the P-wave is specified in seconds
• PR Interval represents the time for the impulse to travel from the atria to the ventricles
• Normal duration of the PR interval is specified in seconds
• QRS Complex signifies ventricular depolarization
• Normal duration of the QRS complex is specified in seconds
• ST Segment occurs at the beginning of ventricular repolarization
• Normal ST Segment occurs at the isoelectric line
• T-Wave signifies ventricular repolarization
• Normal duration of the T-wave is specified in seconds

EKG Review

• It is a graphic representation of the electrical activity of the heart
• Time is on the X-axis, and voltage is on the Y-axis
• A 12-lead EKG is used for diagnostic purposes
• A 5-lead EKG is used for monitoring
• EKG lead placement colors
  • Green = George
  • White = Washington
  • Brown = Bridge
  • Black = smoke
  • Red = over fire

Conduction System of the Heart Review

• The heart consists of specialized cells to initiate and transmit electrical impulses
• These impulses result in the mechanical contraction of the cardiac tissue
• The conduction system includes:
  • Sinoatrial (SA) node, firing at a rate specified in bpm
  • Intra-atrial tracts, firing at a rate specified in bpm
  • Atrioventricular (AV) node, firing at a rate specified in bpm
  • The AV node is also known as AV junction foci
  • Bundle of His, firing at a rate specified in bpm
  • Right and left Bundle Branches, firing at a rate specified in bpm (ventricular rates)
  • Purkinje Fibers, firing at a rate specified in bpm
  • See this link for heart contraction with EKG waves, approximately 3 minutes, 45 seconds long: https://www.youtube.com/watch?v=RYZ4daFwMa8

EKG Rhythm Analysis

• Rate and rhythm should be assessed
  • Check for a P wave for every QRS complex and P wave regularity
  • Assess if the rhythms is regular
    • Check for equal distances between similar waves
    • Assess consistency of P waves and QRS complexes
  • Calculate the heart rate to see if it's between 60 and 100 bpm
    • Measure PR interval, QRS complex, and ST segment
• Waveforms and intervals should be measured and compared to normal values for clinical correlation
• Rhythm and conduction abnormalities, as well as presence of hypertrophy, can be indicated with EKG readings

Calculating Rates from an EKG

• Counting Boxes
  • Large boxes represent 0.2 seconds in time
    • There are 300 large boxes in a minute
  • Small boxes represent 0.04 seconds in time
    • There are 1500 small boxes in a minute
  • Five small boxes equal one large box
    • 5 x 0.04 = 0.2
• For regular rhythms, the "Countdown Method" can be used using the following figures: 300-150-100-75-60-50-43-37-33-30
• For irregular rhythms, count the number of beats in 6 seconds, and multiply by 10

Supraventricular Rhythms

• Supraventricular rhythms originate above the ventricles
• These rhythms originate in the SA Node, Atria, or AV Node

SA Node Rhythms

• Normal Sinus Rhythm
• Sinus Bradycardia
• Sinus Tachycardia
• Sinus Arrhythmia
  • Variable R to R
• Sinus Pause/Arrest
  • Named with underlying rhythm
  • Escape Beat/Escape Rhythm
  • Transient absence of sinus P wave(s)

Normal Sinus Rhythm

• Rate is between 60-100 bpm
• Equal distance between points on the waves
• R-R interval is regular
• One P for every QRS
• All P waves look the same

Sinus Bradycardia

• Heart Rate is less than 60 bpm
• Rhythm is regular
• The relationship of P wave to QRS Complex is 1:1

Sinus Bradycardia Causes

• Good conditioning, normal in athletes
• Decreased oxygenation when sleeping
• Change in consciousness
• Increased intracranial pressure/traumatic brain injury (TBI)
• Vagal stimulation
• Medication that slows down conduction
• Suctioning/gagging/vomiting
• Often seen with heart block problems

Sinus Bradycardia Treatment Implications

• Assess vital signs and symptoms of decreased cardiac output
  • Hypotension, chest pain, altered level of consciousness, dizziness, dyspnea, cool/clammy skin, pallor, nausea
• If symptomatic, call RN or MD, patient is expected to be treated medically, and/or receive pacemaker placement

Sinus Tachycardia

• At a rate greater than 100 bpm
• Rhythm is regular
• P Wave to QRS complex relationship is 1:1
• All P Waves look the same

Sinus Tachycardia Causes

• Typically benign
• Increased activity/exercise, normal response
• Hypothermia
• Hypotension
• Heart failure/insufficient cardiac output
• Anxiety
• Increased sympathetic stimulation
• Stimulants
• Increased demand for O2, such as fever, CHF, or infection

Sinus Tachycardia Treatment

• Assess vitals and signs and symptoms for decreased Cardiac Output
• Team to Assess and Treat Underlying Cause
• Medication

Sinus Arrhythmia

• All P waves are identical
• P for every QRS
• PR interval is between 0.12-0.2 sec
• QRS complexes are identical with QRS duration b/t 0.04-0.10 sec
• R-R interval varies
• HR is between 60-100 bpm but varies

Sinus Arrhythmia Signs/Symptoms/Causes

• Commonly related to respiratory cycle
  • Increase HR: inspiration
  • Decrease HR: exhalation
• Irregularity with vagal stimulation
• Common in young or elderly
• Decrease with exertion

Sinus Arrhythmia Treatment

• None normally needed

Sinus Pause/Sinus Arrest

• Named with underlying rhythm
  • Example: NSR with sinus pause OR Sinus Bradycardia with pause
  • May see Escape Beat or Rhythm
• All P waves are identical
• P for every QRS
• PR interval is b/t 0.12-0.2 sec
• QRS complexes are identical, with QRS duration b/t 0.04-0.10 sec
• R-R interval is regular, but occasional pauses noted

Sinus Pause/Arrest Signs/Symptoms/Causes

• Can be caused by a number of issues
• Increased Parasympathetic activity
• Disease of SA node (sick sinus syndrome (SSS))
• May complain of dizziness due to decreased CO

Sinus Pause/Arrest Treatment

• Need to start treatment while patient has symptoms
• Treat underlying cause
  • Decrease Digitalis toxicity
  • Decrease vagal stimulation
  • PPM placement

Atrial Arrhythmias

• Premature Atrial Contraction
• Atrial Tachycardia
• Paroxysmal Atrial Tachycardia
• Atrial Flutter
• Atrial Fibrillation

Premature Atrial Contraction (PAC)

• Has an underlying Sinus Rhythm
• Normal complexes have a P for every QRS
• An ectopic atrial focus depolarizes prematurely, ahead of the SA node
• Originates from irritable, sometimes ischemic areas
• P wave of early beat may get buried in T wave of prior complex
• P wave is often shaped abnormally
• PR interval is b/t 0.12-0.2 sec
• QRS complexes are identical with QRS duration bt 0.04-0.10 sec
• Frequently followed by a pause

Premature Atrial Contraction PAC Signs/Symptoms/Causes

• Stress
• Stimulants
• Abnormal blood levels of magnesium and/or potassium
• Underlying heart disease
• Irregularities may be palpated
• Patient may feel "palpitations"

Premature Atrial Contraction PAC Treatment

• None required unless advances to Supraventricular Tachycardia (SVT) or Afib

Arrhythmia Terms

• Isolated: Occurs as a single event
• Bigeminal/Bigeminy: Occurs every other beat
• Trigeminal/Trigeminy: Occurs every third beat
• Couplets: Occur in pairs or two in a row
• Triplet: Three in a row
• Unifocal: Originates from one focus
• Multifocal: Originates from multiple/different foci

Supraventricular Tachycardia (SVT)

• Series of rapid heartbeats that begin in or involve the atria
• It can cause the heart to beat very rapidly or erratically
• The heart may beat inefficiently, and the body may receive an inadequate blood supply
• Types SVT include:
  • Atrial Tachycardia
  • Paroxysmal Supraventricular Tachycardia (PSVT)
  • Atrial Flutter
  • Atrial Fibrillation

Atrial Tachycardia

• A type of SVT
• HR is usually greater than 100 and as high as 200 or more bpm
• P waves may or may not look the same
• P may not be present for every QRS
• PR interval <0.20 sec
• QRS are identical with QRS duration b/t 0.04-0.10 sec
• R-R intervals vary

Atrial Tachycardia Signs/Symptoms/Causes

• Same as PACs
• Hypoxemia
• Pulmonary HTN
• Altered pH
• COPD patients
• Can result in decreased CO, dizziness, fatigue, SOB

Atrial Tachycardia Treatment

• Treat the cause
• Perform autonomic/vagal maneuvers such as Valsalva
• B Blocker, Digoxin

Paroxysmal Atrial Tachycardia (PAT) or (PSVT)

• Sudden onset of atrial tachycardia
• Underlying NSR with a burst of atrial tach that eventually returns to NSR
• Abrupt start and stop
• P wave may be present or merged with T wave
• PR is hard to measure
• QRS are identical with QRS duration b/t 0.04-.010 sec
• R-R usually regular, measured >160 bpm

PAT or PSVT Signs/Symptoms/Causes

• Emotional factors
• Overexertion
• Hyperventilation
• Caffeine/Nicotine
• RHD, MVP, PE
• Digitalis toxicity
• Wolff Parkinson White Syndrome
• Dizziness, weakness, SOB
• Chest pain, fainting/vomiting
• May lead to "panic attack"

PAT or PSVT Treatment

• Determine underlying cause
• Discontinue meds
• Autonomic stimulation through Valsalva, coughing, gagging, drink an ice cold liquid
• B blockers

Atrial Flutter

• Caused by rapid firing of ectopic foci in the atria
• Rate atrial is 250-350 bpm
• Rhythm is regular
• P waves are identical because it's the same foci firing
• Relationship between P wave “saw tooth flutter waves” and QRS complex: 2,3,4 or more flutter waves for each QRS
• QRS is usually normal with QRS duration 0.04-0.12 sec
• R to R intervals vary
• May be regular or irregular
• Often when palpate pulse will feel "regularly irregular" rhythm

Atrial Flutter Signs/Symptoms/Causes

• Numerous pathologies
  • RHD, MV dz, CAD, MI, Renal dz, hypoxemia, pericarditis
  • Stress, drugs
• May lead to afib
• May feel palpitations, lightheadedness, and angina due to rapid rate

Atrial Flutter Treatment

• Assess signs and symptoms
• Call RN, NP, MD, PA
• Medical Management
• B blocker, digoxin, verapamil
• Rhythm Conversion
• Anticoagulation

Atrial Fibrillation (AF)

• Abnormal quivering or twitching of atria due to multiple ectopic atrial foci
  • Produces rapid, erratic atrial rhythm
  • Atria do NOT fully depolarize, so the AV node controls impulses which get through, thereby creating an irregular rhythm
• Rate is variable
  • Atrial is not measurable
    • Wavy baseline
    • Not replicated cycle to cycle
  • Ventricular varies depending on the number of impulses from the atria that are conducted thru the AV Node to the ventricles
• Rhythm is irregular
• Irregularly irregular pulse felt when palpated
• Ratio of P to QRS is not applicable
• Absence of discernible P waves
• QRS duration reads 0.04-0.10, and the R-R interval is irregular

Atrial Fibrillation Signs/Symptoms/Causes

• Numerous factors:
  • Age, CHF, ischemia/infarction, CM, digoxin toxicity, drug use, stress, pain, and more
  • Sometimes seen after heart surgery
• May feel palpitations, fatigue, dyspnea, lightheadedness, syncope, and chest pain

Dangers of Atrial Fibrillation

• Peripheral and pulmonary emboli
• Approximately 30% of patients can develop emboli, and need anticoagulants
• Can precipitate or aggravate CHF
• CO can decrease
• "Rapid AFib" May be heard