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Basic Arrhythmia Interpretation REVIEW

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The following information is provided to assist physicians, nurses, paramedics, telemetry technicians and other health care professionals to review the knowledge and skills essential for identification of basic arrhythmias. This text can be used as a reference for arrhythmia review for those who are already knowledgeable in basic arrhythmia interpretation.

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Introduction Conduction System The electrical impulse is spread throughout the cardiac muscle (tissue) resulting in contraction and relaxation. There are several terms that are used in describing the electrical impulse as it travels through the heart creating the contraction (systole) and relaxation (diastole) phases of the cardiac cycle. The electrical conduction system normally arises in the SA node and travels throughout the atria to the AV Junction, through the Bundle of His, then the Bundle Branches and culminating in the Purkinje Fibers

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ECG monitorin~can aid in the detection of myocardial ischemia, infarction, chamber enlargement, hypoxia, dysrhythmias, and conduction problems, as well as in the evaluation of the effects of electrolytes and drugs on the heart. Another indication for ECG monitoring occurs when monitored patients are being transported from one department to another. A portable ECG monitor - defibrillator is used in this monitoring scenario.

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Treat the patient,

NOT the monitor!

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Single-lead Monitoring • •

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There are two basic types of single-lead monitoring systems that are used in continuous ECG monitoring. The first system includes a bedside monitor, patient cables, lead wires and electrodes. It also includes a central station that contains a computerized data bank. This type is referred to as a hardwire monitoring system and requires direct cable wiring from the bedside monitor to the central monitor. The second system is the telemetry system and it uses radio signals to transmit information from the patient to the central station. The lead system used may be a three-lead or five-lead system. o The lead placement for the three-lead, single channel monitoring system requires that one of the leads is positive, one is negative and the third is a ground. o A five-lead system places the electrodes in five exact locations and can be used to monitor in a single or multiple channel system.

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In the Hardwire monitoring system, a lead selector is used to select the best ECG waveform for monitoring . The Telemetry or wireless monitoring system requires placement of the positive and negative electrode in the exact position that the lead is recorded. For example, Lead II is recorded from the right arm electrode (-) to the left leg electrode (+) and the resulting waveform that is recorded is a positive deflection.

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Lead Definitions An ECG lead consists of two electrodes of opposite polarity attached to a monitor, positive and negative, bipolar lead. It also consists of unipolar leads (V leads) which are positive. (The negative is infinity and in the equipment). Each view is slightly different and can assist in analyzing the health of the electrical activity in the heart.

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STEPS TO ANYL YZING A RHYTHM STRIP There are five basic steps to follow in analyzing a rhythm strip. You should follow each step in sequence for every rhythm strip.

Step #1:

Determine the Regularity

(Rhythm) ofthe R-Waves

Start at the left side of the strip and using calipers or an index card; mark the top of two consecutive R waves (go R to R). Continue this measured distance across the strip/R to R) using the 2 marks you placed on the index card from the 1st R to R as your guide or using the set distance of your calipers. If the distance varies from R to R less than 0.12 seconds (3 small squares), the rhythm is considered REGULAR. lfthe distance varies by more than 0.12 seconds between R to R, it is considered irregular.

The distances between the R waves are determined:

Step #2: Calculate the Heart Rate This measurement will always refer to the ventricular rate unless the atrial and ventricular rates differ, in which case both will be given. The ventricular rate is usually determined by looking at a 6-second rhythm strip. The top of the ECG paper is marked at 3-second intervals (two intervals equal 6 seconds). Several methods can be used to calculate the heart rate. These methods differ according to the regularity or irregularity of the rhythm.

Rapid Rate Calculation: The Six Second Method This method is fast and simple and can be used to calculate regular and irregular rhythms. • Obtain a 6-second rhythm strip • Count the number of R waves within that 6-seconds and multiply by 10 o (6 seconds x 10 = 60 seconds) Example: IF there are 12 R-waves within the 6-seconds (12 x 10= 120 bpm) ,... .,/

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Precise Rate Calculation: •

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Sequence Method - 300-150-100 Method

Find a QRS that falls on a heavy black line of the EKG paper. Begin counting starting with the next heavy black line to the right of the starting point (where QRS is on the heavy black line). The first line to the right of the QRS is named 300, the next heavy line is -ISO-and the next is 100- continue with 75-60-50. Find the heavy black line on which the next R wave peaks or is nearest. The number assigned to this line is the estimated heart rate.

Step #3: Identify and Examine the P-wave • All discussion of waveforms will be in Lead II The P wave is the first wave and it should be upright, smoothly rounded and represents atrial depolarization. During the P wave, the electrical impulse originates in the SA node and travels through the inter-atrial conduction pathways and includes most of the AV node. The P wave occurs during ventricular diastole.

PWave There should be one "P" wave for each QRS. Normal P waves appear rounded, small and positive in Lead II. "P" waves should appear nearly identical. This indicates the impulse originated in the SA node "normal sinus rhythm". If they are abnormal or absent it is an indication that the impulse originated outside the SA node.

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Step #4: Measure the PR Interval Measure this interval from the beginning of the P wave (as it leaves the baseline) to the beginning of the QRS complex. The duration of the PR interval is between 0.12-0.20 seconds. (3 small boxes to 5 small boxes) When this interval is prolonged more than 0.20, which is one big box (heavy line to heavy line), it indicates a delay of conduction from the atria to the ventricles. The PR interval represents the time an electrical impulse travels from the SA node through the atria, the AV node, the bundle of His, the bundle branches and the purkinje fibers. II

Step #5: Measure the QRS Complex Measure from the beginning of the QRS complex as it leaves the baseline until the end of the QRS when the ST segment begins. Count the number of squares in this measurement and multiply by 0.04 (time indicated by one small square). For example-If you measure a QRS to be 3 small squares from beginning to end, and then multiply 3 x 0.04 = 0.12 seconds. Normal duration for a QRS complex is 0.06 to 0.10 seconds. If the QRS width is 0.12 (3 small boxes) or greater, it indicates a delay in the conduction through the ventricles .

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Remember: The following steps must be done to successfully determine an arrhythmia: 1. Determine the Regularity Is the rate regular? 2. Calculate the Rate What is the rate? 3. Identify and Examine the P waves Is there one P wave for each QRS, are all P waves identical 4. Measure the PR interval Is the PR interval 0.20 second or less 5. Me25!!!'e the QRS complex Is the QRS width < D.l2 seconds

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Sinus Rhythm Sinus Rhythms are a class of rhythms that originate in the SA node. Sinus rhythms generally travel through the entire conduction system without inhibition. The inherent rate of the sinus node is 60-100 beats per minute. The sinus node is often referred to as the "Physiological Pacemaker" of the heart. It is characterized by a: • • • •

Normal P-wave PR interval between 0.12 and 0.20 seconds QRS width between 0.04 to 0.12 seconds Each QRS complex is preceded by a P-wave.

In reality, nothing or no one is "normal". Every patient has a unique EeG pattern. Nevertheless, scientists like to have a baseline for everything. In a perfect world, we would all have a Normal Sinus Rhythm.

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Sinus Bradycardia Sinus bradycardia meets the same ECG criteria as sinus rhythm, except the rate is below 60 beats pel' minute. Brady - means slow.

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When t symptoms occur, regardless of heart rate, it is said to be symptomatic. Mild Sinus Bradycardia (RR 50 -59) Often produces no symptoms. Bradycardia lwithout symptoms is called asymptomatic. Marked Sinus Bradycardia (RR 35 - 50) Clinical symptoms may occur.

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Cardiac Symptoms: Hypotension and reduced cardiac output, congestive heart !failure, shock predisposes the patient to potentially lethal arrhythmias. I

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/Neuro Symptoms: Decreased perfusion to the brain causes lightheadedness, [dizziness and syncope. ..---------------IN~-;;-ri~us -;igns & sympi~.;;~Ob;;rve the patient! [Ser-ious signs & symptoms present: Note the following sequence: . Atropine 0.5 - 1 mg NP Transcutaneous pacing, if available Dopamine 5 to 20 mcg/kg per min (N) Epinephrine 2 - 10 mg/min (N) . www.americanheart.org

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., May be caused by an increase or decrease in sympathetic tone, disease of the SA node, hypothyroidism (Myxedema), hypothermia, or hypoxia. ., May be caused due to drugs, such as, digitalis, propranolol, diltiazem or verapmil. ., Is commonly seen in association with an acute inferior wall MI. ., May be associated with stimulation of the vagal nerve, e.g., vomiting, vasovagal syncope and carotid sinus stimulation . ., Is commonly seen during periods of sleep. May fall up to 20 beats/min . ., Is common in athletes and is often referred to as an "athletic heart syndrome". These are true athletes and not your "weekend warriors." ________ . .

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[Key Points: r;--At;~Pinei-;-

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[make the heart rate slower. Atropine in Children: dose should be given by weight.

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Evaluate Patient Is patient stable or unstable? (serious signs and symptoms?) Are serious signs and symptoms due to tachycardia? -------'L------Unstable'------,

Unstable patient: serious signs or symptoms Establish rapid heart rate as cause of serious signs and symptoms Rate related signs and symptoms OCCurat many rates, seldom 48 Hrs. (Must anticoagulate first)

May cardiovert:

1. Bad Heart (Must anticoagulate first)

in "bad hearts"

Avoid multiple medications when possible. Flecainide, Propafenone, use in the United States.

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