NHA EKG Technician (CET) — All Questions

Where is the V1 electrode placed for a 12-lead EKG?

• a.Fifth intercostal space, right sternal border
• b.Fourth intercostal space, right sternal border✓
• c.Fifth intercostal space, left midclavicular line
• d.Fourth intercostal space, left sternal border

V1 sits in the fourth intercostal space at the right sternal border, and it is located by walking down from the sternal angle to the second rib, then counting the second, third, and fourth spaces. The fourth space at the left sternal border is V2. The fifth space at the left midclavicular line is V4, and there is no standard chest lead at the fifth space on the right sternal border.

A technician has correctly placed V1. Where does the V2 electrode go?

• a.Fifth intercostal space, left anterior axillary line
• b.Fourth intercostal space, left sternal border✓
• c.Directly below V1 in the fifth intercostal space
• d.Midway between V1 and V4

V2 is placed in the fourth intercostal space at the left sternal border, directly across the sternum from V1. The electrode placed midway between V2 and V4 is V3, and V3 is always positioned after V4 is located. The fifth space at the left anterior axillary line is V5.

Which chest electrode is placed in the fifth intercostal space at the left midclavicular line?

• a.V4✓
• b.V3
• c.V5
• d.V6

V4 is placed in the fifth intercostal space at the left midclavicular line, and it is located before V3 because V3 is defined as the midpoint between V2 and V4. V5 goes at the left anterior axillary line and V6 at the left midaxillary line, both level with V4 rather than following the rib spaces.

After placing V1, V2, and V4, where should the technician place V3?

• a.Midway between V2 and V4 on a straight line✓
• b.At the left anterior axillary line level with V4
• c.Directly below V2 in the fifth intercostal space
• d.Midway between V1 and V2 at the same level

V3 sits on a straight line halfway between V2 and V4, which is exactly why V4 is placed before V3 rather than in numerical order. Halfway between V1 and V2 would land on the sternum, over bone rather than over the heart. Dropping straight down from V2 ignores the diagonal that the chest wall follows as it curves toward the axilla, and the left anterior axillary line at the level of V4 is the position for V5.

A technician is placing V5 on a 12-lead EKG. Which description is correct?

• a.Fifth intercostal space, left midaxillary line
• b.Fourth intercostal space, left anterior axillary line
• c.Left anterior axillary line, on the same horizontal level as V4✓
• d.Sixth intercostal space, left anterior axillary line

V5 is placed at the left anterior axillary line on the same horizontal plane as V4 rather than by counting rib spaces, because the chest wall curves and the horizontal alignment keeps V4, V5, and V6 comparable. The midaxillary line at that level is V6. Counting to the sixth space or the fourth space would place the electrode too low or too high.

Where is the V6 electrode placed?

• a.Right midaxillary line, level with V4
• b.Left midaxillary line, level with V4 and V5✓
• c.Posterior axillary line, level with V4
• d.Left midclavicular line, sixth space

V6 is placed at the left midaxillary line on the same horizontal plane as V4 and V5, completing the left lateral view of the heart. The posterior axillary line is one space further back and is used for the additional posterior lead V7, not for V6. The right midaxillary line looks at the heart from the wrong side of the chest, and dropping to the sixth space at the midclavicular line abandons the horizontal plane that V4, V5, and V6 share.

Where should the limb electrodes be placed for a standard 12-lead EKG?

• a.On fleshy, non-muscular areas of the arms and lower legs, positioned symmetrically✓
• b.On the bony prominences of the wrists and ankles for the best signal
• c.On the upper chest and abdomen for all four limb leads
• d.Anywhere convenient, since limb lead position does not affect the tracing

Limb electrodes belong on flat, fleshy areas of the arms and lower legs, placed symmetrically on the right and left, because bone conducts poorly and muscle bellies generate tremor artifact. Torso placement is acceptable only for continuous monitoring or when a limb is missing, and it must be documented because it alters the tracing. Limb position does affect amplitude and axis, so it is never arbitrary.

A 12-lead tracing shows an inverted P wave, inverted QRS, and inverted T wave in lead I, while the chest leads look normal. What is the most likely cause?

• a.The left arm and left leg electrodes are reversed
• b.The V1 and V2 chest electrodes are reversed
• c.The right arm and left arm electrodes are reversed✓
• d.The right leg ground electrode is loose

Reversing the right and left arm electrodes flips the polarity of lead I, producing a globally negative complex in that lead while the chest leads, which do not depend on arm placement, remain normal. Swapping the left arm and left leg electrodes is the closest competitor and does disturb the frontal-plane leads, but it exchanges leads I and II and inverts lead III, so lead I still records an upright complex. Reversing V1 and V2 distorts only those two chest leads, and a loose right leg ground electrode produces baseline wander or noise rather than inversion.

A tracing shows a uniform, thick, fuzzy baseline with small spikes occurring exactly 60 times per second across all leads. What is the most likely cause?

• a.AC interference from nearby powered equipment✓
• b.Deep respiration moving the chest wall electrodes
• c.Electrodes that have dried out and lost contact
• d.A resting tremor of the patient's hands

Sixty-cycle interference is alternating current picked up from nearby electrical devices, cords, or fluorescent lights, and it produces a perfectly regular fuzzy band at exactly 60 hertz in every affected lead. The giveaway is the word exactly: no physiologic source repeats at a fixed 60 per second. A resting tremor produces irregular jagged spikes at a slower and varying rate, deep respiration causes a slow rolling baseline rather than fine spikes, and dried electrodes produce erratic noise or a flat trace confined to the leads they belong to.

An anxious, cold patient produces a tracing with irregular jagged spikes that obscure the small waveforms. What artifact is this and what is the best first correction?

• a.AC interference; move the patient cable away from power cords
• b.Wandering baseline; coach the patient to breathe slowly
• c.Somatic tremor; warm the patient and support the limbs✓
• d.Loose electrode; reapply the chest electrodes

Somatic tremor is muscle-movement artifact from shivering, tension, or involuntary motion, and the first correction is to warm the patient, support the arms and legs on the bed, and coach the patient to relax. Wandering baseline is a slow rolling drift rather than jagged spikes. AC interference is a uniform 60-cycle band that does not vary with how tense the patient is, and a loose electrode disturbs only the leads that electrode contributes to rather than the whole tracing.

A tracing shows the baseline slowly drifting up and down in a wave pattern that matches the patient's breathing. What should the technician check first?

• a.Whether the standardization pulse is set to 20 mm/mV
• b.Whether the patient is holding a deep breath during the whole run
• c.Whether the electrodes are loose, dried out, or over lotion✓
• d.Whether the arm and leg electrodes are reversed

A wandering baseline is usually caused by poor electrode contact from loose tabs, dried gel, body lotion, oils, or sweat, so the first check is the skin and the electrodes themselves. Respiration genuinely contributes to the drift, which is what makes breath-holding tempting, but it treats a symptom, cannot be sustained through a full 12-lead, and leaves the bad contact in place. Paper speed and standardization change the size or spacing of the complexes without causing drift, and lead reversal changes polarity rather than making the baseline roll.

What does the standardization mark on an EKG tracing indicate when it is 10 mm tall?

• a.Each large box on the paper represents 10 milliseconds
• b.The patient's voltage is ten times the normal range
• c.The paper is running at 10 mm per second
• d.One millivolt produces a 10 millimeter deflection✓

Standard calibration is 10 mm per millivolt, printed as a rectangular standardization mark two large boxes tall at the start of the tracing, so amplitudes can be compared between machines and over time. Paper speed is a separate setting, and the standard is 25 mm/sec rather than 10. The mark says nothing about the patient's own voltage, and each large box represents 0.20 second, not 10 milliseconds.

At the standard paper speed, how much time does one small box represent, and what is that speed?

• a.0.04 second at 50 mm/sec
• b.0.20 second at 25 mm/sec
• c.0.04 second at 25 mm/sec✓
• d.0.10 second at 25 mm/sec

Standard EKG paper runs at 25 millimeters per second, so each 1 mm small box equals 0.04 second and each 5 mm large box equals 0.20 second. The 0.20 second value belongs to the large box, not the small one. A speed of 50 mm/sec is a special setting used to spread out very fast rhythms, and 0.10 second does not correspond to any standard box.

How much time and voltage does one large box on standard EKG paper represent?

• a.0.50 second and 5 millimeters of height
• b.0.20 second and 5 millimeters of height✓
• c.0.04 second and 1 millimeter of height
• d.0.10 second and 10 millimeters of height

A large box is five small boxes across and five tall, so it represents 0.20 second horizontally and 5 millimeters, or 0.5 millivolt, vertically at standard calibration. The 0.04 second and 1 millimeter values describe a small box. The 0.10 and 0.50 second values do not match standard paper, where five large boxes equal one second.

A patient has a hairy chest and oily skin. What is the correct skin preparation before applying chest electrodes?

• a.Wipe with a povidone-iodine swab and apply the electrodes wet
• b.Shave the whole chest with a razor and apply lotion afterward
• c.Clip hair at each site, cleanse with alcohol, dry, then abrade lightly✓
• d.Apply the electrodes over the hair and press them down firmly

Good skin prep means clipping excess hair only at the electrode sites, cleansing with alcohol to remove oils, allowing the skin to dry completely, and lightly abrading with dry gauze to lower skin resistance. Applying electrodes over hair or onto wet skin gives poor contact and a wandering baseline. Lotion insulates the skin rather than helping it conduct, and shaving the whole chest with a razor is unnecessary and risks nicks that break the skin barrier.

A technician is setting up 5-lead telemetry monitoring. Which placement follows the standard color convention?

• a.White on the right shoulder, black on the left shoulder, green on the right lower torso, red on the left lower torso, brown on the chest✓
• b.White on the right shoulder, black on the left shoulder, red on the right lower torso, green on the left lower torso, brown on the mid-chest
• c.White on the left shoulder, black on the right shoulder, red on the left torso, green on the right torso, brown on the chest
• d.White on the right shoulder, black on the left shoulder, green on the left torso, red on the right torso, brown on the chest

The standard five-electrode convention is white on the right upper chest, black on the left upper chest, green on the right lower chest or abdomen, red on the left lower chest or abdomen, and brown as the chest electrode, remembered as white on the right, smoke over fire on the left, and clouds over grass on the right. The near-miss answer keeps the shoulders correct but swaps red and green, which reverses the lower half of the frontal plane and can invert lead II. Swapping white and black reverses lead I, and any placement that puts the wrong color on the wrong side changes the vectors the monitor computes.

How many electrodes are applied for standard 3-lead cardiac monitoring, and what do they produce?

• a.Five electrodes producing leads I, II, and III
• b.Three electrodes producing leads V1 through V3
• c.Three electrodes producing all 12 leads
• d.Three electrodes producing leads I, II, and III✓

Three-lead monitoring uses three electrodes, usually right arm, left arm, and left leg positions, and generates the three bipolar limb leads I, II, and III, with lead II most often selected because it shows P waves well. Twelve leads require ten electrodes. Five-lead systems add a ground and a chest lead, and V1 through V3 are precordial leads that a 3-lead setup cannot produce.

The QRS complexes on a 12-lead tracing are so tall that they run off the paper and overlap the lead above. What is the appropriate action?

• a.Switch to half standardization, 5 mm/mV, and mark the tracing✓
• b.Reduce the gain until the complexes match the previous tracing
• c.Increase the paper speed to 50 mm/sec and reprint the whole tracing
• d.Move the chest electrodes down one intercostal space

When complexes are too tall to fit, the machine is switched to half standardization, so 1 millivolt produces a 5 millimeter deflection, and the change is marked on the tracing so the physician can interpret amplitudes correctly. Reducing the gain by eye until the tracing resembles an earlier one is the tempting wrong answer: it changes amplitude by an undocumented amount, which destroys any comparison between the two studies. Increasing paper speed widens the complexes without lowering their height, and moving electrodes falsifies the anatomic view.

A patient's heart rate is so fast that the complexes are crowded together and hard to measure. Which machine adjustment can help, and what must the technician remember?

• a.Set the standardization to 20 mm/mV, since amplitude changes fix crowding
• b.Reduce the paper speed to 10 mm/sec, which doubles each interval
• c.Reduce the paper speed to 12.5 mm/sec, which spreads the complexes
• d.Increase the paper speed to 50 mm/sec, making each small box 0.02 second✓

Doubling the paper speed to 50 mm/sec spreads the complexes apart for easier measurement, but each small box then represents 0.02 second instead of 0.04 second, so the change must be documented or every interval will be misread as twice its true value. Slower speeds compress the tracing further, which is the opposite of what is needed, and no reduction in speed spreads complexes apart. Standardization changes amplitude, not timing, so it does nothing about complexes that are too close together.

What is the standard patient position for obtaining a resting 12-lead EKG?

• a.Sitting up with the arms folded on the chest
• b.Supine with arms at the sides and legs uncrossed✓
• c.Standing with the arms extended forward
• d.Left lateral with the knees drawn up

The standard resting EKG is taken with the patient supine, arms relaxed at the sides, legs flat and uncrossed, so muscle tension and limb contact do not distort the tracing. Folded arms and crossed legs create somatic tremor and can bridge electrodes electrically. Standing or lying on the side shifts the heart within the chest and changes waveform amplitude and axis, so any deviation from supine has to be documented on the tracing.

A patient with severe shortness of breath cannot tolerate lying flat for a 12-lead EKG. What should the technician do?

• a.Have the patient sit on the edge of the bed and hold the electrodes
• b.Postpone the test and document that the patient cannot lie flat
• c.Raise the head of the bed, obtain the tracing, and document the position✓
• d.Lay the patient flat quickly and finish before symptoms worsen

Patient comfort and safety come first, so the head of the bed is raised to a tolerable semi-Fowler position, the tracing is obtained, and the non-standard position is recorded on the tracing because it can alter waveform amplitude and axis. A documented semi-Fowler tracing is still diagnostically useful, which is why postponing the study is the wrong trade: it delays care for a test that could have been done. Forcing a dyspneic patient flat risks harm, and holding electrodes by hand introduces motion artifact and unreliable contact.

A physician orders right-sided chest leads on a patient with a suspected right ventricular infarction. Which electrode position corresponds to V4R?

• a.Fifth intercostal space, left midaxillary line
• b.Second intercostal space, right sternal border
• c.Fourth intercostal space, left sternal border
• d.Fifth intercostal space, right midclavicular line✓

Right-sided leads mirror the standard positions across the chest, so V4R sits in the fifth intercostal space at the right midclavicular line and is the single most useful lead for right ventricular infarction. The fourth space at the left sternal border is standard V2. The left midaxillary position is V6, and the second space at the right sternal border is not a chest electrode site.

A patient has a right below-the-knee amputation. How should the technician place the limb electrodes?

• a.Place both leg electrodes on the intact left leg, a few inches apart
• b.Place both leg electrodes symmetrically on the lower torso✓
• c.Move the right leg electrode to the right arm, above the elbow
• d.Omit the right leg electrode and record a nine-lead tracing

When a limb is missing, the electrode is moved to the nearest torso location on that side and the opposite limb electrode is moved to match, keeping the frontal-plane leads symmetric, and the modification is documented for the interpreting physician. Placing both leg electrodes on the remaining leg leaves them asymmetric with respect to the trunk and distorts the frontal plane. Moving a leg electrode onto an arm collapses Einthoven's triangle, and omitting the right leg electrode removes the reference the machine needs to produce a tracing at all.

When performing a 12-lead EKG on a female patient with large breast tissue, where should the V4 and V5 electrodes be placed?

• a.On the back, directly opposite the usual positions
• b.Above the breast to avoid contact with the tissue
• c.On top of the breast tissue at approximately the correct level
• d.Under the breast, on the chest wall at the correct landmarks✓

Chest electrodes are placed beneath the breast on the chest wall at the true anatomic landmarks, because breast tissue between the electrode and the heart attenuates voltage and distorts amplitude. Placing electrodes on top of the breast is the common shortcut and is exactly what causes falsely low voltage in the lateral leads. Moving them above the breast abandons the fifth intercostal space, and back placement is reserved for the special posterior leads. The patient's privacy is protected with draping throughout.

On a 12-lead tracing, leads I, II, and aVR are clean, but lead III alone shows an erratic, noisy trace. What is the most likely cause?

• a.The patient is having a myocardial infarction affecting only the inferior wall
• b.A single electrode or lead wire connection is loose or dried out✓
• c.Alternating current interference from the room lighting
• d.The paper speed is incorrect

Artifact confined to one lead points to a problem with a specific electrode or lead wire, since each limb lead uses a different combination of electrodes; the fix is to reapply that electrode and reseat the wire. A true infarction produces recognizable ST or Q wave changes across a group of leads rather than random noise. Paper speed errors and AC interference affect the entire tracing, not one lead.

A technician opens a package of disposable electrodes and finds the conductive gel is dry and crusted. What should be done?

• a.Discard the package and open fresh, unexpired electrodes✓
• b.Moisten the gel with alcohol to soften it
• c.Moisten the electrodes with tap water and use them
• d.Use them anyway and increase the gain to compensate

Dried electrodes cannot conduct properly and cause wandering baseline and unreliable amplitudes, so they are discarded and replaced with fresh electrodes from a sealed, unexpired package. Water and alcohol are not substitutes for conductive gel; alcohol in particular raises resistance once it dries. Increasing the gain amplifies the artifact along with the signal and leaves the contact problem untouched.

A tracing shows steady 60-cycle interference. Which troubleshooting sequence is most appropriate?

• a.Apply fresh electrodes and ask the patient to breathe deeply
• b.Increase the paper speed and print the tracing a second time
• c.Unplug nearby equipment and move cables off power cords✓
• d.Switch to half standardization and print the tracing again

Sixty-cycle interference comes from surrounding alternating current, so the corrections are environmental: turn off or unplug nearby devices, separate the patient cable from power cords, verify a good ground electrode, and keep the patient from touching bed rails or other metal. Paper speed and standardization changes alter how the tracing is displayed without removing the noise. Fresh electrodes fix contact problems, and deep breathing worsens baseline wander rather than removing interference.

Before beginning a shift, a technician inspects the EKG machine. Which finding requires the machine be removed from service?

• a.Electrode tabs stored in a sealed, unexpired package
• b.A standardization mark measuring exactly 10 millimeters
• c.A paper roll that is about half full
• d.A frayed patient cable with exposed wire✓

A frayed cable with exposed conductor is an electrical hazard and a source of artifact, so the machine is tagged and removed from service until repaired. A half-full paper roll is simply replaced or monitored. A 10 millimeter standardization mark is the correct calibration, and sealed unexpired electrodes are exactly what should be stocked.

Leads I, II, and III are described as bipolar limb leads. What does the term bipolar describe about these three leads?

• a.Each records the difference in voltage between two limb electrodes, one acting as positive and one as negative✓
• b.Each records voltage at one positive electrode and compares it with a calculated zero reference point
• c.Each displays two separate waveforms at the same time, one taken from the arms and one from the legs
• d.Each can be recorded with either polarity, so the complexes may be printed upright or inverted

A bipolar lead has a true positive and a true negative electrode: lead I is left arm minus right arm, lead II is left leg minus right arm, and lead III is left leg minus left arm. The description of one positive electrode measured against a calculated zero reference belongs to the augmented leads aVR, aVL, and aVF, which are unipolar. No lead prints two waveforms at once, and polarity is fixed by the definition of the lead rather than chosen at the machine. The right leg electrode is a neutral reference and forms no part of any of the three bipolar leads.

On a normal 12-lead tracing, the P wave, QRS complex, and T wave are all negative in lead aVR. What accounts for this?

• a.Its positive electrode sits at the right shoulder, facing away from the path of depolarization✓
• b.The right arm electrode is the negative pole in leads I and II, so everything at aVR prints inverted
• c.The augmented leads are printed at reduced sensitivity, which pushes their deflections below the baseline
• d.It is the one lead that records repolarization only, and repolarization runs opposite to depolarization

The overall wave of depolarization in a normal heart travels down and to the left, toward the left leg and the left lower chest. The positive electrode of aVR sits at the right shoulder, so that wave moves away from it and writes negative deflections in every part of the complex. The right arm does serve as the negative pole in leads I and II, but that has no bearing on aVR, where the right arm carries the positive pole. Inversion in aVR alone is expected on a correctly recorded tracing, the augmented leads are printed at the same 10 mm/mV calibration as every other lead, and no lead records repolarization by itself.

A physician asks a technician which leads on the 12-lead tracing look at the inferior surface of the heart. Which answer is correct?

• a.Leads I and aVL, whose positive electrodes sit on the left arm side of the frontal plane
• b.Leads V1 and V2, whose positive electrodes sit on either side of the sternum
• c.Leads II, III, and aVF, whose positive electrodes all point downward toward the left leg and foot✓
• d.Leads V5 and V6, whose positive electrodes sit low on the left side of the chest wall

The inferior surface of the heart rests on the diaphragm, and the three leads whose positive poles point down toward the left leg record it: leads II, III, and aVF. Leads I and aVL point toward the left shoulder and record the high lateral wall, which is a frontal-plane group as well and is the most common wrong choice here. The pair beside the sternum records the septum, and the two low left chest leads record the low lateral wall. Grouping leads by the surface they face is what lets a technician describe where a change appears without interpreting it.

A tracing shows ST segment changes in leads I and aVL while V5 and V6 look unchanged. Which region do leads I and aVL view?

• a.The anterior wall of the left ventricle, the same region recorded by V3 and V4
• b.The high lateral wall, which lies above the region recorded by V5 and V6✓
• c.The inferior wall, the same region recorded by leads II, III, and aVF
• d.The septum between the ventricles, recorded also by V1 and V2

Leads I and aVL are frontal-plane leads whose positive poles face the left shoulder, so they record the high lateral portion of the left ventricle. The low lateral wall is recorded by V5 and V6, which is why changes can appear in the two limb leads while those chest leads stay normal. The anterior wall belongs to V3 and V4, the inferior wall to II, III, and aVF, and the septum to V1 and V2. A technician reports which leads show the change and leaves the interpretation to the physician.

A patient scheduled for a routine 12-lead EKG has documented dextrocardia. What is the correct way to record the tracing?

• a.Record the standard 12-lead with no change and let the interpreting physician allow for the reversed anatomy
• b.Report to your supervisor that a 12-lead cannot be recorded on a patient whose heart lies on the right
• c.Mirror the chest electrodes onto the right chest and reverse the two arm electrodes✓
• d.Leave the chest electrodes in the usual places and move only the limb electrodes to the right side of the body

With the heart lying on the right, the standard positions face away from the chambers, so the chest electrodes are mirrored across to the right chest and the arm electrodes are reversed to match the reversed anatomy. The tracing has to be clearly labeled as a dextrocardia recording, because an unlabeled mirrored tracing looks like arm lead reversal to whoever reads it. Recording an unmodified 12-lead produces a tracing that imitates limb lead reversal with poor R wave progression, which is exactly the confusion the modified placement avoids. Dextrocardia does not prevent a technician from obtaining a usable tracing, so escalating instead of recording delays the study for no reason.

A student asks a technician to explain the difference between an electrode and a lead. Which explanation is correct?

• a.An electrode is the wire running from the machine, and a lead is the adhesive patch stuck to the skin
• b.An electrode is the sensor on the skin, and a lead is the view of the heart made by comparing electrodes✓
• c.The two terms mean the same thing, since each electrode applied to the patient prints one lead
• d.An electrode picks up rhythm only, and a lead picks up both the rhythm and the size of the chambers

An electrode is the physical sensor stuck to the skin; a lead is the electrical view the machine builds by comparing electrodes. That is why ten electrodes, four on the limbs and six on the chest, yield twelve leads. Treating the words as interchangeable is the most common error, but it cannot be right, since ten sensors would then produce only ten views. The cable running from the machine is the patient cable or lead wire, which is a third thing entirely.

A technician arrives to record a 12-lead two days after chest surgery and finds a sterile dressing covering the V3 and V4 sites. What should the technician do?

• a.Take the dressing down, apply the electrodes on the marked sites, and tape the dressing back afterward
• b.Apply V3 and V4 on top of the dressing and press firmly so the gel makes contact through the gauze
• c.Leave V3 and V4 off, record the other ten leads, and write the reason for the omission on the printout
• d.Notify the nurse or your supervisor before the dressing is disturbed and follow the direction given✓

Taking down a surgical dressing is a sterile procedure outside the technician's scope, so the person responsible for the wound decides whether it comes off and when. Pressing an electrode onto gauze gives no skin contact, and the resulting flat or noisy trace is worse than no trace. Omitting two chest leads without asking anyone leaves an incomplete study that will have to be repeated, and the omission itself may be read as poor R wave progression. Reporting first and then recording under direction is the sequence that protects both the wound and the tracing.

A monitor technician at the central telemetry station sees new ST segment elevation in the monitoring lead of a patient who has just reported chest pressure to the nurse. What is the appropriate action?

• a.Save the strip and pass the change along to the nurse at the end of the shift
• b.Report the change to the nurse or your supervisor at once so a diagnostic 12-lead can be obtained✓
• c.Chart that the patient is having an anterior infarction and file the strip in the record
• d.Switch the display to a different lead and watch for several minutes to see whether the change resolves

At a central station the technician can see the signal but cannot see, touch, or assess the patient, so the fastest useful thing the technician can do is put the information in the hands of the people at the bedside. A monitoring lead can show that something has changed, but only a 12-lead recorded with standard placement can be used to work up an infarction, and chest pressure with a new ST change is time-critical. Reporting it at once so the ordered 12-lead is done is inside the technician's scope; recording a diagnosis such as anterior infarction in the chart is not. Saving the strip and passing the change along at the end of the shift is proper documentation delivered far too late, and hunting for a lead that looks better delays the study and can leave the change out of the record. Print and save the strip that shows the change so the report is backed by the tracing.

Which landmark does a technician use to start counting intercostal spaces before placing the chest electrodes?

• a.The sternal angle, where the second rib meets the sternum; the space just below it is the second intercostal space✓
• b.The notch at the top of the sternum, where the space lying just below the notch is the first intercostal space
• c.The lower tip of the sternum, counting upward from the space above the xiphoid process to the fourth space
• d.The lower border of the left clavicle, since the space directly beneath the clavicle is the second intercostal space

The sternal angle, also called the angle of Louis, is the ridge where the manubrium meets the body of the sternum, and the second rib joins the sternum there. Sliding the finger off that rib lands in the second intercostal space, and counting down two more spaces reaches the fourth, where V1 and V2 go. Starting at the suprasternal notch is the common error, because the first rib lies under the clavicle and cannot be palpated reliably, so the count starts one space off and shifts every chest electrode. Counting up from the xiphoid crosses the costal margin and is no more accurate; the space under the clavicle is the first, not the second.

In the standard order for applying chest electrodes, V4 is placed before V3. What is the reason for that order?

• a.V3 sits midway between V2 and V4, so V4 has to be in place first✓
• b.V4 gives the tallest complexes, so placing it first lets the machine set its gain
• c.V4 marks the horizontal line that V1 and V2 are then measured down from
• d.Placing V4 first keeps the technician from counting down the intercostal spaces twice

V3 has no landmark of its own: it is defined as the midpoint of a line between V2 at the fourth intercostal space at the left sternal border and V4 at the fifth intercostal space at the left midclavicular line. Until V4 is on the chest there is no second point to measure from, so a V3 placed first is a guess. Saving a second count of the intercostal spaces is a genuine convenience of this order, but convenience is not what makes the order necessary. Gain is set by the calibration signal at 10 mm/mV, and V1 and V2 are found by counting ribs rather than by measuring down from V4.

A technician places V1 and V2 in the second intercostal space instead of the fourth. What effect does this have on the tracing?

• a.Little effect on the tracing, as long as both electrodes are moved together by the same number of spaces
• b.The P waves there can invert and the tracing can imitate an anterior infarction✓
• c.The R wave voltage in those leads rises enough to suggest left ventricular hypertrophy
• d.The complexes in those leads shift below the baseline and the measured QT interval shortens

Electrodes set one or two spaces too high sit closer to the atria and farther from the ventricular mass, so the P waves in V1 and V2 can become negative and the R waves lose height. That loss of R wave height imitates an anteroseptal infarction, and an rSr pattern may appear as well, which is why superior misplacement is one of the errors most likely to change what a physician reads. Moving both electrodes together does not cancel the error, since the whole chest view is displaced toward the base of the heart. Misplacement of this kind lowers rather than raises R wave voltage in those leads and does not shorten the QT interval.

V6 is placed at the left midaxillary line. Which description identifies that landmark?

• a.The vertical line running down the front of the chest through the front fold of the armpit
• b.The vertical line running down the back of the chest through the lower tip of the scapula
• c.The vertical line dropped from the middle of the collarbone down through the nipple line
• d.The vertical line dropped from the top of the armpit, midway between its front and back folds✓

The midaxillary line falls from the apex of the axilla and lies midway between the anterior and posterior axillary folds, which places V6 on the side of the chest at the same horizontal level as V4 and V5. The line through the anterior fold is the anterior axillary line and belongs to V5, which is why that choice is the tempting one. The line through the middle of the clavicle is the midclavicular line, used for V4. The line at the tip of the scapula is a posterior landmark and is not used for any of the six standard chest leads.

A physician orders posterior leads on a patient with a suspected posterior infarction. Where does the V8 electrode go?

• a.At the left midscapular line, on the same horizontal level as V6✓
• b.At the left posterior axillary line, level with V4 and one space below V6
• c.Just to the left of the spine, one intercostal space above the level of V6
• d.Over the lower tip of the left scapula, two intercostal spaces below V6

The three posterior leads sit on one horizontal line continuing around from V6: V7 at the left posterior axillary line, V8 at the left midscapular line, and V9 at the left border of the spine. Because they stay level with V6, none of them is placed a space above or below it, which rules out the two answers that move up or down an interspace. The posterior axillary line is where V7 goes, not V8, and that is the closest wrong answer. The electrode near the spine is V9.

Under a common hospital protocol, a 15-lead EKG is ordered when right ventricular or posterior involvement is suspected. Which leads are added to the standard 12?

• a.V7, V8, and V9, spaced across the left side of the patient's back
• b.V3R, V4R, and V5R, spaced across the right side of the patient's chest
• c.V4R, V5R, and V6R, recorded in place of V4, V5, and V6 on the left
• d.V4R on the right chest, plus V8 and V9 on the left side of the back✓

The usual 15-lead protocol keeps all twelve standard leads and adds three: V4R to look at the right ventricle and V8 and V9 to look at the posterior wall, which is why one right-sided and two posterior leads appear together. Adding only the three posterior leads, or only the right-sided ones, gives a 15-lead count on paper but leaves one of the two suspected regions unexamined. Replacing V4, V5, and V6 would still be twelve leads, and it would discard the lateral views. Protocols vary between facilities, so the technician follows the order and labels every added lead on the tracing.

A monitor is set up to display the modified chest lead MCL1. Where does the positive electrode belong?

• a.At the fifth intercostal space at the left midclavicular line
• b.At the fourth intercostal space, right sternal border✓
• c.Below the left clavicle, close to the point of the left shoulder
• d.At the fifth intercostal space at the left midaxillary line

MCL1 imitates the view of V1, so its positive electrode goes where V1 goes, at the fourth intercostal space at the right sternal border, with the negative electrode near the left shoulder. That right-sided view separates right from left ventricular ectopy and shows atrial activity well, which is why monitors are often left in it. The fifth space at the left midclavicular line is the V4 position, and a positive electrode at the left midaxillary line makes MCL6, not MCL1. The spot below the left clavicle is where the negative electrode of MCL1 belongs.

Telemetry monitoring electrodes are applied to the torso rather than to the arms and legs. What is the main reason for this?

• a.Skin over the torso conducts the signal better than the skin covering the arms and the legs does
• b.Monitor cables are too short to reach the four limbs from a telemetry box carried at the waist
• c.The torso lies closer to the heart, so the complexes recorded there are tall enough to alarm on
• d.Limb electrodes pick up arm and leg movement, and torso placement keeps the rhythm readable as the patient moves✓

A monitored patient walks, eats, and turns in bed for hours, and electrodes on moving limbs fill the tracing with muscle artifact that buries the rhythm. Torso positions sit over bone and quieter tissue, so the complexes stay readable while the patient moves. Skin resistance is lowered by preparation rather than by the body part chosen, and cable length is a convenience rather than the reason. Torso placement is not chosen to make the complexes taller either; it shifts the recorded amplitudes enough that a monitoring tracing cannot stand in for a diagnostic 12-lead.

Why is a single continuous monitoring lead not used to rule in a myocardial infarction?

• a.The monitor runs the tracing at a slower paper speed, so ST segments cannot be measured on it
• b.The monitor filters the P wave out of the display, leaving only the QRS complex to review
• c.Torso electrode positions record voltages far too small for any measurement to be made
• d.One lead gives a single view of the heart and is meant for watching rhythm✓

Locating an infarction depends on seeing which region shows the change, and that takes the twelve views of a standard 12-lead; one monitoring lead offers a single angle and is intended to follow rhythm. The torso positions used for monitoring also shift the amplitudes, so the tracing is not comparable with a diagnostic recording, although the voltages are perfectly measurable. Monitors run at the same 25 mm/sec paper speed as an EKG machine and display the P wave, so neither of those explanations holds. A change seen on the monitor is reported and then a 12-lead is recorded.

In Einthoven's triangle, which two electrodes form lead II and what polarity does each carry?

• a.The right arm is the negative pole and the left leg is the positive pole✓
• b.The left arm serves as the negative pole and the left leg as the positive
• c.The right arm is negative and the left arm positive, with the leg as ground
• d.The left leg is the negative pole and the right arm the positive, giving tall waves

Einthoven's triangle is drawn between the right arm, the left arm, and the left leg, and lead II runs from the right arm as negative to the left leg as positive. That axis lies closest to the normal direction of depolarization, which is why lead II shows the most upright P waves and is the usual rhythm lead. The combination of left arm negative with left leg positive is lead III, and right arm negative with left arm positive is lead I, so both are real leads and neither is lead II. Reversing the poles of lead II would invert the complexes rather than enlarge them.

What does the word augmented describe in the augmented voltage leads aVR, aVL, and aVF?

• a.The machine doubles the paper speed for these three leads, so their complexes are printed wider
• b.Two extra electrodes are added to the limbs to raise the voltage that these leads can record
• c.These three leads are recorded at 20 mm/mV, which is twice the standard calibration setting
• d.The signal at a single positive electrode is small, so the machine increases it by about half✓

Each augmented lead compares one positive limb electrode with a reference made from the other two limb electrodes, and the resulting signal is small, so the machine boosts it roughly 50 percent to produce a readable complex. No extra electrodes are involved; the same four limb electrodes serve the three bipolar leads and the three augmented leads. The whole tracing is printed at one paper speed of 25 mm/sec and one calibration of 10 mm/mV, and the standardization mark at the start of the strip shows that the augmented leads share it. Changing the calibration would alter every lead, not only these three.

A woman in her third trimester of pregnancy becomes lightheaded and pale when she lies flat for a 12-lead EKG. Under a typical facility policy, what should the technician do?

• a.Seat her fully upright in a chair and record the tracing with the chest electrodes left in place
• b.Tilt her slightly onto her left side and record with the electrodes in their standard positions✓
• c.Keep her flat and work quickly, since a tracing recorded in any other position cannot be read
• d.Turn her onto her right side so that the weight of the uterus is carried away from the heart

Late in pregnancy the uterus can press on the inferior vena cava when the patient lies flat, reducing the blood returning to the heart and causing lightheadedness and pallor. Tilting the patient toward her left side moves the uterus off the vena cava, and a small wedge under the right hip achieves it while the electrodes stay on their anatomical landmarks. A right-sided tilt leaves the vena cava, which lies to the right of the spine, still compressed. Sitting fully upright changes the position of the heart within the chest, so any position other than the standard one is noted on the tracing for the physician who reads it.

On a finished tracing the R wave grows from V1 to V2, is clearly smaller in V3 than in V2, and then grows again in V4 and V5. What is the most likely cause?

• a.An old anterior infarction that has taken the R wave out of the middle chest leads
• b.The whole chest set applied one intercostal space lower than the correct positions
• c.Rotation of the heart within the chest, which flattens the middle chest leads
• d.The V2 and V3 electrodes were interchanged when the chest was set up✓

R wave height should build steadily from V1 through V5, and a single lead that steps backward and then recovers points to two neighboring electrodes swapped rather than to disease, since no infarction affects one lead and spares the leads on both sides of it. An old anterior infarction is the answer worth weighing, but it flattens a run of leads instead of producing one isolated dip. Placing the whole chest set a space low shifts all six leads together and does not break the sequence. Rotation likewise shifts the transition point smoothly rather than reversing it for one lead.

A completed 12-lead shows abnormal Q waves in V1, V2, V3, and V4. Which surfaces of the heart do those four leads view?

• a.The inferior surface of the heart, viewed from below by way of the left leg
• b.The lateral wall together with part of the inferior surface
• c.The posterior wall, which faces the spine behind the heart
• d.The septum together with the anterior wall of the left ventricle✓

V1 and V2 sit over the septum and V3 and V4 sit over the anterior wall, so a change running through all four is described as septal and anterior. The inferior surface is recorded by leads II, III, and aVF, and the lateral wall by leads I and aVL with V5 and V6. The posterior wall faces away from every standard chest electrode, which is why leads V7 through V9 exist. Naming the region the leads cover is reporting, not interpretation, and it is what the technician can say about a tracing.