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THE METHODIST BASIC EKG STUDY GUIDE Basic EKG Self-Study Guide Objectives 1. Understand the basic anatomy of the heart. 2. Describe the normal physiology of cardiac conduction. 3. Identify normal EKG waveform morphology. 4. Differentiate between basic dysrhythmias. 5. Describe the physiological consequences and treatments of basic dysrhythmias. Blood Flow through the Heart During diastole, the ventricles relax, the atria contract and blood is forced through the open tricuspid and mitral valves. The aortic and pulmonic valves are closed. During systole, the atria relax and fill with blood. The mitral and tricuspid valves are closed. Ventricular pressure rises and forces open the aortic and pulmonic valves. The ventricles then contract and blood flows through the circulatory system. Cardiac Blood Supply Like the brain and all other organs, the heart needs an adequate supply of blood to survive. The coronary arteries, which lie on the surface of the heart, supply the heart muscle with blood and oxygen. The coronary ostium, an opening in the aorta that feeds blood to the coronary arteries, is located near the aortic valve. During diastole, when the left ventricle is filling with blood, the aortic valve is closed and the coronary ostium is open, enabling blood to fill the coronary arteries. The heart has veins like other parts of the body. Cardiac veins collect deoxygenated blood from the capillaries of the myocardium. The great cardiac vein, thebesian veins and other cardiac veins, along with the coronary sinus, return blood to the right atrium, where it continues through the circulation. Coronary Arteries eft Coronary Artery Sinus Node Branch Diagonal Branch of Left Anterior Descending AN Posterior Descending Artery Abnormal heart rhythms occur for several reasons. 1. The vagal stimulation of the parasympathetic nervous system can cause a decrease in the rate at the SA node and can also decrease the excitability of the AV junction fibers. This causes a slowing of the heart rate, and in severe cases, a complete blockage of the impulse through the AV junction. 2. Sympathetic stimulation also affects cardiac rhythm and conduction. It increases the rate at the SA node and increases the rate of conduction and excitability throughout the heart. It also increases the force of myocardial contraction. Subsequently, the overall workload on the heart is increased. 3. Asmall area of the heart can become more excitable than normal, which causes abnormal heart beats called ectopy. Ectopic foci are usually caused by an irritable area in the heart. This irritability can be caused by ischemia, stimulants such as nicotine and caffeine, lack of sleep or anxiety. Intrinsic rates of pacemaker cells located in three critical areas of the heart: SA node- 60 to 100 AV junction- 40-60 Purkinje fibers- 20-40 As impulses are transmitted, cardiac cells undergo cycles of depolarization and repolarization. Cardiac cells at rest are considered polarized, meaning that no electrical activity takes place. Cell membranes separate different concentrations of ions, such as sodium and potassium, and create a more negative charge inside the cell. This is called the resting potential. Once a stimulus occurs, ions cross the cell membrane and cause an action potential, or cell depolarization. When a cell is fully depolarized, it attempts to return to its resting state in a process call repolarization. Electrical charges in the cell reverse and return to normal. The cycle then repeats itself with each impulse. How to Read an EKG Strip EKG paper is a grid where time is measured along the horizontal axis. e Each small square is 1 mm in length and represents 0.04 seconds e Each larger square is 5 mm in length and represents 0.20 seconds Voltage is measured along the vertical axis. e 10mmis equal to 1mT in voltage e The diagram below illustrates the configuration of ELG graph paper and where to measure the components of the EKG wave form | eS Sr A seconds ——— ©RnGeus,com i} 05 mV P Of seconds: Normal Components of the EKG Waveform P wave e Indicates atrial depolarization, or contraction of the atrium. e Normal duration is not longer than 0.11 seconds (less than 3 small squares) e Amplitude (height) is no more than 3 mm e No notching or peaking QRS complex e Indicates ventricular depolarization, or contraction of the ventricles. e Normally between 0.06 - 0.12 seconds in duration e Amplitude is not less than 5 mm in lead II or 9 mm in V3 and V4 e Rwaves are deflected positively and the Q and S waves are negative T wave e Indicates ventricular repolarization e Not more that 5 mm in amplitude in standard leads and 10 mm in precordial leads e Rounded and asymmetrical ST segment e Indicates early ventricular repolarization e Normally not depressed more than 0.5 mm e May be elevated slightly in some leads (no more than 1 mm) PR interval e Indicates AV conduction time e Duration time is 0.12 to 0.20 seconds QT interval e Indicates repolarization time. General rule: duration is less than half the preceding R-R interval Systematic Approach to Arrhythmia Interpretation REGULARITY (ALSO CALLED Rhythm) «Is it regular? «Is it irregular? « Are there any patterns to the irregularity? « Are there any ectopic beats; if so, are they early or late? RATE + What is the exact rate? «Is the atrial rate the same as the ventricular rate? P WAVES + Are the P waves regular? + Is there one P wave for every QRS? + Is the P wave in front of the QRS or behind it? + ls the P wave normal and upright in Lead II? + Are there more P waves than QRS complexes? + Do all the P waves look alike? » Are the irregular P waves associated with ectopic beats? PR INTERVAL + Are all the PRis constant? «Is the PRI measurement within normal range? + If the PRI varies, is there a pattern to the changing Measurement? QRS COMPLEX * Are all the QRS complexes of equal duration? » What is the measurement of the QRS complex? + Is the QRS measurement within normal limits? * Do all the QRS complexes look alike? » Are the unusual QRS complexes associated with ectopic beats? Sinus Bradycardia (SB) ieee iiniiia EKG Characteristics: Rhythm: regular Rate: less than 60 beats/minute P Wave: normal size and shape QRS Complex: normal 0.06-0.12 seconds T Wave: normal Common Causes: Vagal stimulation, ischemia to the SA node, beta-blockers, digitalis toxicity, increased ICP. It can also be seen as a normal variation in athletes. Nursing Intervention: Notify the doctor. Anticipate oxygen administration, atropine or pacing for symptomatic bradycardia. Sinus Tachycardia (ST) SHER ts : ESGHTOGSIGE (EESGEEUEES + HH EKG Characteristics: Rhythm: regular Rate: Greater than 100 beats/minute P Wave: Normal or (may be buried in the T wave) QRS Complex: Normal T wave: Normal Common Causes: Exercise, infection, increased temperature, response to pain, hypovolemia, hypoxia, fever, stress, pulmonary emboli, myocardial infarction, increased circulating catecholamines and responses to stimulant drugs. Nursing Intervention: Notify the doctor if this is a new occurrence. Determine and treat the cause. The clinical significance will depend upon the underlying cause. Bigeminy and Trigeminy Bigeminy and Trigeminy 1, P¥C BIGEMINY: Definition: Bigeminy is a premature ventricular contraction that is followed by a normal QRS complex (PVC every other beat). Trigeminy is PVC followed by two normal QRS complexes in an alternating pattern (PVC every third beat). EKG Characteristics: Rhythm: Irregular Rate: Usually normal 60-100 beats/minute P-wave: may be absent with each ectopic beat (normal with the underlined rhythm) QRS Complex: Normal complex followed by a wide QRS complex. T-wave: may appear in the opposite direction of the QRS after each ectopic beat (normal with the underlined rhythm) Common Causes: Possible causes include electrolyte imbalances such as (low K+, Mg+), hypoxia, ischemia, medication toxicity, and acute infarction. Nursing Intervention: Notify the doctor if this is a new arrhythmia, administer oxygen. Determine underlying cause and treat accordingly. Treat the arrhythmia if the patient is symptomatic. Supraventricular Tachycardia (SVT) +f HIRES Definition: SVT is a rapid regular heartbeat that originates above the ventricles, it is known as supraventricular. It is caused by a rapid firing of ectopic beats. EKG Characteristics: Rhythm: regular Rate: 150-250 beats/minute P Wave: Unable to visualize P wave due to rapid rate PR Interval: none QRS Complex: normal Common Causes: Possible causes include stimulants, anxiety, atrial enlargement, medication toxicity, and hyperthyroidism. Nursing Intervention: Notify the doctor and oxygen administration. Vagal maneuvers (cough and valsalva) can be used. Cardioversion may be needed for unstable patients. Medical management includes calcium channel blockers or beta blockers. Prepare for a code if the rhythm does not convert. Atrial Flutter (A-Flutter) ; ; Te siiatts cet meena nea ana =e HE + i St snail is E Definition: A-flutter is a single atrial ectopic beat that is conducted in a repetitive pattern resulting in a series of atrial waves also know as flutter or F waves. EKG Characteristics: Rhythm: Atrial rhythm is regular. Ventricular rhythm could be regular or irregular. Rate: Atrial rate: 250-400beats/minute. Ventricular rate varies P Wave: A "saw tooth” shape or flutter waves are present. QRS Complex: Normal 0.06-0.12 seconds. T Wave: Not visible Common Causes: enlarged atria, chronic obstructive pulmonary disease, valve disease and pericarditis. Nursing Intervention: Notify MD if this is a new rhythm, oxygen. Calcium channel blockers, beta-blockers, anticoagulants, and digoxin. Cardioversion may also be used if drug treatment is not successful. IVR: Idioventricular Rhythm Definition: IVR originates from the ventricles. IVR is characterized by a wide QRS complex that is regular. It may be transient or continuous. Continuous IVR is generally a terminal event, occurring just before the patient enters an agonal rhythm, and then asystole. EKG Characteristics: Rhythm: Usually regular Rate: Atrial rate can’t be determined. Ventricular rate is regular IVR: 30-40 beats per minute Accelerated IVR: 40-60 beats per minute P waves: None QRS Complex: Wide, being greater than 0.12 seconds. T waves: abnormal (usually in a negative deflection) Common causes: It is caused by increased vagal stimulation, and heart disease. Nursing Interventions: Check vital signs, notify the doctor. Administer oxygen and atropine per hospital protocol. Possibly initiate transcutaneous pacing, and start dopamine infusion if the patient is hypotensive. Prepare for code situation. 
