Basic ECG Interpretation Challenge Test Questions With Complete Solutions

What are the 6 parts of the cardiac conduction cycle? correct answer: -SA node -Internodal pathways -AV node -Bundle of His -R and L bundle branches -Purkinje fibers What is the SA node? correct answer: -Small cluster of cells located in the upper R atrium *-Pacemaker of the heart* What are internodal pathways? correct answer: Impulses sent by the SA node that travel through the atrial muscle fibers via the intra-atrial pathways Allows for simultaneous depolarization and contraction of the atria Where is the AV node located? correct answer: Lower portion of the R atria What is the inherent rate of the SA node? correct answer: 60-100 bpm What does the AV node do? correct answer: -Receives impulse from the SA node -Delays conduction to allow for the atria to contract, then conducts to the ventricle Where is the Bundle of His? correct answer: -Upper part of the intraventricular septum -Connects AV node with bundle branches What is the Bundle of His? correct answer: AV node and Bundle of His are known as the Junctional area What is the inherent rate of the Bundle of His? correct answer: 40-60 bpm What is the back up for the SA node? correct answer: AV junction Where are the R and L bundle branches? correct answer: Arise from the bundle of His and travel down the R and L side of the septum What are purkinje fibers? correct answer: Smaller branches of the bundle branches that spread throughout the myocardium and terminate there What is the inherent rate of purkinje fibers? correct answer: 20-40 bpm What is the final back up pacemaker for the SA node and AV junction? correct answer: Purkinje fibers What is automaticity? correct answer: Ability to act as an impulse, initiating electrical activity and spontaneous depolarization *Most important difference between cardiac and skeletal muscle cells* What is excitability? correct answer: Ability to respond to a stimulation and initiate an impulse What is conductivity? correct answer: Ability to transmit an impulse that has been initiated and passes along cell membranes What is contractility? correct answer: Ability of a muscle fiber to shorten in response to a stimulus What is refractoriness? correct answer: Inability of a muscle fiber to respond to a stimulus during an interval following contraction What is the absolute refractory period? correct answer: Time interval, when no matter how strong the stimulus, a cardiac cell cannot be depolarized. How do you measure the absolute refractory period? correct answer: Beginning of the QRS to the middle of the T wave What is the relative refractory period? correct answer: Time interval, when given only a stronger than normal stimulus, a cardiac cell may depolarize Why is the relative refractory period known as a vulnerable period? correct answer: Because of risk of R on T phenomena How do you measure the relative refractory period? correct answer: Middle of T wave to end of T wave What information is provided by ECGs? correct answer: -Conduction disturbances -Cardiac muscle mass -Ischemia, injury, or infarction *Doesn't include info on mechanical contraction (pumping action)* What are the 2 leads most frequently used for cardiac monitoring? correct answer: Lead II and V1 Why is lead II preferred for rhythm interpretation? correct answer: Because the waveforms are all upright ECG boxes: correct answer: What does the P wave represent? correct answer: Atrial depolarization What does the PR interval represent? correct answer: Time it takes for the impulse to pass from SA node through atrial depolarization How do you measure the PR interval? correct answer: Measure from beginning of P wave to the beginning of Q wave What is the normal length for a PR interval? correct answer: 0.12-0.20 seconds What does the QRS complex represent? correct answer: Ventricular depolarization How do you measure the QRS complex? correct answer: From the beginning of the Q wave to the end of the S wave What is the normal duration of a QRS complex? correct answer: 0.06-0.10 seconds What does the T wave represent? correct answer: Ventricular repolarization What does the QT interval represent? correct answer: Total period of time required for depolarization and repolarization of the ventricles What is the normal time interval for QT interval? correct answer: 0.40 seconds or less What are some factors that lengthen the QT interval? correct answer: -Drug toxicity (amiodarone, abx, CNS drugs, chemo drugs) -Electrolyte imbalances (hypokalemia, hypomagnesemia, hypocalcemia) -Cocaine use T or F: A prolonged QT interval can lead to lethal dysrhythmias? correct answer: True What does the ST segment represent? correct answer: Time interval between completion of depolarization (J point) and the beginning of the repolarization of the ventricles Where does the ST segment rest? correct answer: On the isoelectric line T or F: Elevation/depression of the ST segment is an indication of an abnormality and is usually associated with myocardial injury/ischemia? correct answer: True What is ST elevation? correct answer: *Injury* identified by ST segment elevating above isoelectric line What is ST depression? correct answer: *Ischemia* identified by ST segment dropping below isoelectric line Sinus rhythms: correct answer: *Inherent rate: 60-100 bpm* P waves: 1:1 and all look the same (1 P wave for 1 QRS) PR interval: normal (at least 0.12 seconds) QRS duration: normal *Tx: none; gold standard rhythm* Sinus bradycardia: correct answer: -1 P wave for each QRS complex -PR interval is at least 0.12 seconds *-Rate: <60 bpm* *-Tx: usually none, but atropine or pacing IF symptomatic* Sinus tachycardia: correct answer: -1 P wave for each QRS complex -PR interval at least 0.12 seconds *-Rate: 101-150 bpm* *-Tx: tx cause (fever, pain, anxiety, etc)* Sinus arrhythmia: correct answer: -1 P wave for each QRS complex -PR interval: normal *-Rhythm is irregular or off a "smidge" (R-R)* -Rate increases during inspiration and decreases during expiration -May have sinus brady/tachy arrhythmia, depending on rate -Usually an underlying pulmonary dx is present *-Tx: none* Sinus arrest/pause: correct answer: -Stimulus originates in SA node, however, there are periods when SA node doesn't fire which causes periods of asystole and can cause syncope depending on duration *-Tx: evaluate underlying cause; if symptomatic, give atropine or pace* Sinus rhythm with IVCD: correct answer: IntraVentricular Conduction Defect -Abnormally wide QRS (>0.12 seconds) caused by damage in normal conduction system through ventricles which causes a delay in the time spent during ventricular depolarization *-Tx: continue to monitor (chronic)* *Look at packet for picture* Atrial flutter: correct answer: *A-flutter (saw-tooth appearance)* -Atrial rate: 151-250 bpm -P waves: flutter waves -PR interval: UTD -QRS: normal -R-R usually regular *-Tx: CCB, BB, and anticoagulants* Atrial fibrillation: correct answer: *A-fib* -Atrial rate: UTD -P waves: fibrillatory -PR interval: UTD -QRS: normal *-Irregular R-R* *-Tx: CCB, BB, anticoagulants* Sinus rhythm with junctional escape beat: correct answer: *Compensatory or protective mechanism* when SA node slows down, stops firing or becomes blocked *-Beat that comes LATE during sinus rhythms, has no P wave, and a normal QRS* *-Tx: tx underlying cause of slowed rhythm* Junctional rhythm: correct answer: -R-R is regular *-Rate: 40-60 bpm* *-No sinus P waves (may be absent, inverted [upside down], or behind QRS complex)* *-Tx: identify underlying cause; pace if symptomatic* *Look at packet for picture* Accelerated junctional rhythm: correct answer: -R-R is regular *-Rate: 61-100 bpm* *-No sinus P waves (may be absent, inverted [upside down], or behind QRS complex)* -QRS: normal *Tx: assess for underlying cause, continue to monitor* *Look at packet for picture* Junctional tachycardia: correct answer: -R-R is regular *-Rate: 101-150 bpm* *-No sinus P waves (may be absent, inverted [upside down], or behind QRS complex)* -QRS: normal *-Tx: evaluate underlying cause* *Look at packet for picture* Supraventricular tachycardia (SVT): correct answer: -Catch all for any tachycardia rhythm with a *rate over 151 bpm* that *occurs above the ventricles* -May see this used when unable to distinguish between sinus tach and junctional tach because P waves are UTD *-Tx: vagal, adenosine, synchronized cardioversion (tx pt based on S/S and hemodynamic stability)* Idioventricular rhythm (IVR): *Lethal rhythm* correct answer: -R-R is regular *-Rate: 20-40 bpm* -QRS: wide, bizzare (0.12 secs or wider) -NO P-waves *-Tx: pacing* Accelerated idioventricular rhythm (AIVR): correct answer: -Regular R-R -Rate: 41-100 -QRS: wide, bizarre (0.12 secs +) -NO P-waves *-Tx: closely monitor, watch for S/S of slowing rhythm* Ventricular tachycardia (v-tach): *Lethal rhythm* correct answer: -QRS: wide, bizarre (>0.12 secs) -Rate: >101 bpm -Regular R-R -No P-waves *-Tx: if there's a pulse, synchronized cardioversion; if pulseless, CPR and defib* Torsades de pointes: *Lethal rhythm* correct answer: -QRS: wide, bizarre (>0.12 secs) -Irregular R-R -No P-waves *-Complex twists around isoelectric line (looks like a tornado), and is a multidirectional form of v-tach* *-Tx: activate RRT for expert consultation* Ventricular fibrillation (v-fib): *Lethal rhythm* correct answer: -Rapid, irregular, and chaotic rhythm -No organized depolarization of the ventricles = no CO = no pulse *-Tx: CPR and defib* Asystole: *Lethal rhythm* correct answer: -Total absence of ventricular electrical activity -No CO *-Tx: CPR* Agonal: *Lethal rhythm* correct answer: -Slow, irregular R-R -QRS: wide, bizarre (>0.12 secs) -Referred to as a dying heart *-Tx: CPR* Pulseless electrical activity (PEA): *Lethal rhythm* correct answer: -Clinical situation, rather than specific cardiac dysrhythmia -Exists when organized electrical activity other than v-tach is present, and pt has no pulse *-Can only be identified by assessing pt for no pulse, not just interpreting rhythm strip* *-Tx: CPR* *Look at picture in packet* Sinus rhythm with premature ventricular complex (PVC): correct answer: -Ectopic impulse originating in the ventricle that occurs early -QRS: wide, bizarre, (>0.12 secs) -PVCs may all look the same within one strip, or differently -Compensatory pause after, generally *-Tx: asymptomatic --> none, symptomatic --> identify and tx underlying cause* Sinus rhythm with 1st degree heart block: correct answer: -Atrial and ventricular rhythm is regular -P-waves are 1:1 -PR interval: constant, >0.20 seconds -Not a true block, it's a conduction delay -QRS: normal -MUST identify underlying rhythm -Tx: identify underlying cause and continue to monitor Second-degree heart block, type I (Wenckebach): correct answer: -Atrial rhythm: regular -Ventricular rhythm: irregular -P-waves occur more than QRS's (extra p-wave without QRS following) -PR interval: progressively lengthens until dropped QRS Tx: identify underlying cause; if pt is brady then tx w atropine and/or pacing *Longer, longer, longer, drop. Now you have wenckebach* Second-degree heart block, type II (mobitz II): correct answer: -Atrial: regular -Ventricular: regular/irregular -P-waves occur more than QRS (may be 2+ p waves for each QRS) -PR interval is the same for conducted beats -QRS: normal or wide *-Tx: pacing* Third degree heart block (complete AV block): correct answer: -Atrial: regular -Ventricular: regular -P waves occur more than QRS -PR interval: variable, no relationship -Occurs when AV junction is completely blocked and the SA node beats independently from the ventricles -Inherent rate of SA node and ventricles will kick in -QRS: varies *-Tx: pacing* Questions for heart blocks: correct answer: Are the PR intervals the same throughout the entire rhythm? -Yes = mobitz II -No, ask question 2 Are the R-R waves regular throughout the entire rhythm? -Yes = CHB -No, ask question 3 Are PR intervals changing and RR waves irregular? -Yes = wenckebach What is a pace/fire? correct answer: Artificial pacemaker emits an electrical impulse What is a pacing spike? correct answer: Small vertical line recorded on the ECG tracing when artificial pacemaker emits an electrical impulse What is the pacing rate? correct answer: -Programmed rate at which the pacemaker will pace the heart in absence of intrinsic cardiac activity at the set rate of the pacemaker -Program rate is the distance between two consecutive pacemaker spikes What is capture? correct answer: -Indicated that the heart has responded to a pacing stimulus -Reflected on ECG as a waveform behind pacemaker spike -Waveform is determined by where the pacemaker is placed (A, V, or AV) What is sense? correct answer: Ability of the pacemaker to detect or "see" the heart's naturally occurring beats Atrial paced (A-paced): correct answer: -Waveform immediately following the pacemaker spike is a P-wave indicating that the pacemaker impulse originated in the atria -Each pacemaker spike followed by a p-wave and QRS complex, no intrinsic beats = pacemaker is functioning appropriately -Tx: continue to monitor Ventricular paced (V-paced): correct answer: -Waveform immediately following pacemaker spike is a wide QRS complex, indicating that the pacemaker impulse originated in the ventricles -Each pacemaker spike is followed by a QRS complex, no intrinsic beats = pacemaker is functioning appropriately -Tx: continue to monitor *Look at packet for picture* Atrial ventricular paced (AV-paced): correct answer: -2 pacemaker spikes: one before P wave and one before QRS -Indicates pacemaker fires in both atria and ventricle -Each pacemaker spike followed by expected complex, no intrinsic beats = pacemaker functioning appropriately -Tx: continue to monitor Paced with failure to capture: correct answer: -Pacemaker malfunction -Pacemaker delivers pacing stimulus at the appropriate timing intervals but the expected QRS doesn't follow spike -Tx: increase output Paced with oversensing: correct answer: -Pacemaker inappropriately inhibited firing because it detects electrical signals other than the intended R wave -Sensing can only be evaluated if intrinsic activity is present -Strip often looks like something is missing or rhythm might be slow Tx: decrease sensitivity *Look at packet for picture* Paced with undersensing: correct answer: -Pacemaker fails to see intrinsic activity and fires overtop of naturally occurring beats -Strip often looks crowded with too much activity -Tx: increase sensitivity *See packet for picture*