Presentation on theme: "Basic Overview ECG Rhythm Interpretation. Objectives To recognize the normal rhythm of the heart - “Normal Sinus Rhythm.” To recognize the most common."— Presentation transcript:
Basic Overview ECG Rhythm Interpretation
Objectives To recognize the normal rhythm of the heart - “Normal Sinus Rhythm.” To recognize the most common rhythm disturbances. To identify emergency interventions for life threatening arrhythmias
I. Impulse Conduction & the ECG Sinoatrial node AV node Bundle of His Bundle Branches Purkinje fibers
Reminder-the EKG only reflects the heart’s electrical activity-not its contraction 1. The “PQRST”- Reminder-the EKG only reflects the heart’s electrical activity-not its contraction P wave - Atrial depolarization T wave - Ventricular repolarization QRS - Ventricular depolarization
2. The PR Interval Atrial depolarization + delay in AV junction (AV node/Bundle of His) (delay allows time for the atria to contract before the ventricles contract) normal time 0.12 to 0.20 sec.
3. Pacemakers of the Heart SA Node - Dominant pacemaker with an intrinsic rate of beats/minute. AV Node - Back-up pacemaker with an intrinsic rate of beats/minute. Ventricular cells - Back-up pacemaker with an intrinsic rate of beats/minute.
4. The ECG Paper Horizontally One small box s One large box s Vertically One large box mV
4. The ECG Paper (cont) Every 3 seconds (15 large boxes) is marked by a vertical line (hash mark). This helps when calculating the heart rate. You need a 6 second strip to calculate heart rate (30 large boxes) 3 sec
4. The ECG Paper (cont) Count the number of P waves in a 6 second strip (30 large boxes) and multiply by 10 to determine atrial rate (9 x 10 = 90) Atrial rate = 90 beats/min Count the number of QRS complexes in a 6 second strip (30 large boxes) and multiply by 10 to determine ventricular rate (9 x 10 =90) Ventricular rate + 90 beats/min 3 sec
II.Normal Sinus Rhythm (NSR) Normal Rhythm of Heart--etiology Etiology: the electrical impulse is formed in the SA node and conducted normally. This is the normal rhythm of the heart; other rhythms that do not conduct via the typical pathway are called arrhythmias.
II.Normal Sinus Rhythm (NSR) Characteristics Rate – 60 to 100 Regularity – rhythm is regular P waves – one P wave preceding each QRS PR interval – normal between 0.12 and 0.20 seconds and constant in length QRS – all look the same QRS duration – equal to or less than 0.12 seconds and constant in width QT interval – equal to or less than 0.44 seconds and constant in length
III.SA Node Problems defined The SA Node can: fire too slow fire too fast Sinus Bradycardia Sinus Tachycardia
A. Sinus Bradycardia Rate less than 60 beats per minute--etiology Etiology: SA node is depolarizing slower than normal, impulse is conducted normally (i.e. normal PR and QRS interval). Significance: Lower rate may cause decrease in cardiac output
A. Sinus Bradycardia -- C haracteristics Rate: less than 60 beats per minute Regularity: rhythm is regular P wave: normal; one precedes each QRS PR interval: normal between 0.12 and 0.20 seconds QRS: normal, equal to or less than 0.12 seconds QT: normal or may be prolonged
A. Sinus Bradycardia Signs and Symptoms due to Sinus Bradycardia May have no symptoms at all May have signs of decreased cardiac output - hypotension, cool clammy skin, - shortness of breath, chest pain or pressure - light headed, dizziness or blurred vision - syncope
A. Sinus Bradycardia Treatment for Sinus Bradycardia Treat only if symptomatic - IV atropine - IV dopamine - Transcutaneous pacemaker
B. Sinus Tachycardia--etiology Rate greater than 100 beats per minute but less than 150 beats per minute Etiology: SA node is depolarizing faster than normal, impulse is conducted normally. Significance: increased workload of the heart Remember: sinus tachycardia is a response to physical or psychological stress, (hypoxia, pain, hypovolemia).
B. Sinus Tachycardia -characteristics Rate greater than 100 beats per minute but less than 150 beats per minute Rate: 100 beats per minute but less than 150 beats per minute. Regularity: rhythm is regular P wave: normal, one precedes each QRS PR interval: normal between 0.12 and 0.20 seconds QRS: normal, equal to or less than 0.12 seconds QT: normal
B. Sinus Tachycardia Signs and Symptoms May have no symptoms at all May have signs of decreased cardiac output - hypotension, syncope and blurred vision - chest pain and/or palpitations - may report a sense of nervousness or anxiety
B. Sinus Tachycardia Treatment Look for the cause (ie. pain, anxiety, fever, hemorrhage) and treat the cause. If tachycardia leads to cardiac ischemia treatment may include medications to slow the heart rate Beta blockers or Calcium channel blockers
III. Atrial Arrhythmias Single or Multiple irritable areas can depolarize and “take over” from the SA node. Atrial tissue
A. Atrial Fibrillation etiology Etiology: Atrial impulses are formed in a totally unpredictable fashion-there are no p waves. Significance: The atria do not contract in a coordinated way therefore, the cardiac output is decreased. The atria do not empty fully, so there is a risk of atrial clots The AV node allows some of the impulses to pass through at variable intervals (so rhythm is irregularly irregular). Rates can get dangerously high
A. Atrial Fibrillation characteristics Rate: Atrial rate: not measurable exceeds 400 beats per minute. Ventricular rate: 30 to 220 beats per minute Regularity: grossly irregular P waves: absent; erratic baseline PR interval: not measurable QRS: normal QT: not measurable
A. Atrial Fibrillation Signs and symptoms Patients with chronic atrial fibrillation may be asymptomatic New onset atrial fibrillation patients may have symptoms related to decreased cardiac output (loss of atrial contraction and fast ventricular rate) hypotension, cool clammy skin, shortness of breath, chest pressure or pain, dizziness, blurred vision or syncope
A. Atrial Fibrillation treatment If treatment is required: Beta Blocker, Calcium Channel blockers will decrease rate IV Amiodarone may decrease rate and convert rhythm (NOT IV bolus!) Synchronized Cardioversion will convert the rhythm
B. Atrial Flutter Deviation from NSR No P waves. Instead flutter waves (note “sawtooth” pattern) are formed at a rate of per minute Only some impulses conduct through the AV node Significance & treatment -as in Atrial Fibrillation
C.Supra Ventricular Tachycardia (SVT) Atrial Tachycardia Deviation from NSR Heart rate: speeds up to greater than 150 beats per minute Rhythm: regular, with normal QRS complexes. Significance: Greatly increased myocardial oxygen demand Could become life threatening
C. SVT – Signs and symptoms Patient may be asymptomatic May have signs of decreased cardiac output: Hypotension, cool clammy skin, shortness of breath, chest pain or pressure, dizziness, blurred vision or syncope
C. SVT Treatment Treatment: 1.Adenosine followed by Beta Blocker or Calcium Channel Blocker 2.Synchronized Cardioversion in emergency
IV. Ventricular Cell Problems Ventricular cells can: fire occasionally from 1 or more irritable area fire continuously from multiple irritable areas fire continuously from a single irritable area Premature Ventricular Contractions (PVCs) Ventricular Fibrillation Ventricular Tachycardia (VT)
IV. Ventricular beats When an impulse originates in a ventricle: conduction through the ventricles will be abnormal QRS will be wide (greater than 0.12 seconds) and bizarre. Multi-focal PVCs
IV. Ventricular Conduction Normal Signal moves rapidly through the ventricles Abnormal Signal moves slowly through the ventricles result is a wide QRS
A. PVCs--characteristics Deviation from NSR Early beats originate in the ventricles resulting in wide (greater than 0.12 sec.) and bizarre QRS complexes. When there is more than one premature beat, and the beats look alike, they are called “unifocal”. When there is more than one premature beat, and the beats look different, they are called “multifocal”.
A. PVCs etiology Etiology: Ventricular irritability can be caused by hypoxia, electrolyte imbalances. Significance: Early beats from the ventricle do not deliver full cardiac output; if untreated may lead to VT/VF.
B. Ventricular Tachycardia Deviation from NSR: Impulse is originating in the ventricles (no P waves, wide QRS, rate greater than 100). Significance: greatly reduced cardiac output- -Life threatening arrhythmia!! Treatment: IV Lidocaine or IV Amiodarone (NOT IV bolus)
C. Ventricular Fibrillation Etiology: Hundreds of ventricular cells are excitable and depolarizing randomly Significance: no cardiac output; no pulse Death producing arrhythmia Death producing arrhythmia Treatment: CODE BLUE 1. Defibrillation 2. IV Epinephrine 3. IV Amiodarone
V. Heart Blocks (Bradycardia) Etiology: weakness, fatigue or damage to the AV node Significance: Bradycardia may result in decreased cardiac output Treatment (same as for bradycardia): IV Atropine IV Dopamine Transcutaneous Pacing
A. 1st Degree AV Block Etiology: Prolonged conduction delay in the AV node or Bundle of His. PR interval: greater than 0.20 seconds and is constant
B. 2nd Degree AV Block, Type I Etiology: Each successive atrial impulse encounters a longer and longer delay in the AV node until one impulse (usually the 3rd or 4th) fails to make it through the AV node. P waves: More than QRSs P-R interval: gets progressively longer
C. 2nd Degree AV Block, Type II Etiology: Conduction is all or nothing (no prolongation of PR interval); typically block occurs in the Bundle of His. More P waves than QRSs PR interval does not vary in length
D. 3rd Degree AV Block Etiology: There is complete block of conduction in the AV node; atria and ventricles form impulses independently of each other. More P: waves than QRSs QRS to QRS (ventricular rate) is regular P to P (atrial rate) is regular—faster than ventricular rate
3rd Degree AV Block Characteristics 40 bpm Rate? Regularity? regular no relation to QRS wide (greater than 0.12 s) P waves? PR interval? none QRS duration?
Summary RhythmRate (beats per minute) RegularityCommentsTreatment Sinus60-100RegularNormal rhythm of heartNone Sinus BradycardiaLess than 60RegularSlow rhythm-can cause symptoms of decreased cardiac output If symptomatic: atropine 0.5 mg IV push Sinus Tachycardia100 – 150RegularFast rhythm-caused by fever, pain, dehydration Treat the cause Suprventricular Tachycardia (SVT) Greater than 150RegularFast-can cause symptoms of decreased cardiac output Adenosine, -blockers, Diltiazem (Cardizem), Cardioversion if unstable Atrial Fibrillation IrregularNo p-waves, PR not measurable -blockers, Diltiazem (Cardizem) Atrial Flutter Regular or Irregular No p-waves, flutter waves— sawtooth pattern -blockers, Diltiazem (Cardizem) Premature Ventricular Contractions Varies—can be normal IrregularEarly beats, wide, bizarreAmiodarone Ventricular Tachycardia RegularWide, regular, fast; no p-wavesAmiodarone—if pulse Defibrillation—if pulseless Ventricular Fibrillation Rapid,ChaoticNo pattern; Can lead to deathDefibrillation!
End of Reading Summary—Heart Blocks Name of Block# p-waves compared to # QRS complexes PR intervalQRS complexes Treatment First degree# p-waves = # QRS complexes PR interval longer than 0.20; constant All presentAtropine, if slow Second degree type I More p-waves than QRS complexes PR interval gets longer and longer QRS dropped periodically Atropine, if slow Second degree type II More p-waves than QRS complexes PR interval is constant QRS dropped periodically Transcutaneous pacing Third degree Complete block More p-waves than QRS complexes No PR interval; P to P constant QRS to QRS constant Transcutaneous pacing