NHA EKG Technician (CET) Practice Test

样题与解析

以下是本题库中的部分真题与完整解析。完整题库请用上方的刷题工具。

1. 1. Rhythm Interpretation

   A technician measures the distance from the beginning of the P wave to the beginning of the QRS complex on a strip and counts four small boxes. What is the PR interval, and is it normal?

   • a.0.04 second, which is shorter than normal
   • b.0.16 second, which is normal
   • c.0.08 second, which is normal
   • d.0.40 second, which is longer than normal

   答案: b

   解析: Each small box equals 0.04 second at the standard paper speed of 25 mm/sec, so four small boxes equal 0.16 second. The normal PR interval is 0.12 to 0.20 second, so 0.16 second falls in range. The 0.04 and 0.08 answers miscount the boxes, and 0.40 second would require ten small boxes and would indicate a first-degree AV block.

2. 2. Rhythm Interpretation

   A strip shows a normal sinus beat followed by a wide bizarre beat, then another sinus beat followed by another wide bizarre beat, repeating throughout the strip. What is this pattern called?

   • a.Ventricular bigeminy
   • b.Ventricular tachycardia
   • c.Ventricular trigeminy
   • d.A couplet

   答案: a

   解析: Bigeminy means every other beat is a premature ventricular contraction, alternating one normal beat and one PVC. Trigeminy is a PVC every third beat. A couplet is two PVCs in a row, and three or more consecutive PVCs at a rate above 100 constitute ventricular tachycardia.

3. 3. EKG Acquisition

   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

   答案: a

   解析: 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.

4. 4. Safety & Professionalism

   What is appropriate routine maintenance for EKG equipment between patients?

   • a.Clean the machine only when it looks visibly soiled or sticky
   • b.Wipe the machine and cables with an approved disinfectant
   • c.Wrap the lead wires tightly around the machine to save space
   • d.Submerge the entire patient cable in a disinfectant solution

   答案: b

   解析: Between patients the machine surfaces, cables, and any reusable components are wiped with a facility-approved disinfectant, the wires are inspected for cracks and gently uncoiled, and supplies are restocked so the unit is ready for the next study. Immersing a patient cable ruins the connectors and creates an electrical hazard. Wrapping wires tightly breaks the internal conductors and causes artifact, and waiting for visible soil ignores contamination that cannot be seen.

5. 5. Rhythm Interpretation

   During tracheal suctioning a monitored patient's rate falls from 74 to 46 beats per minute. Upright P waves still precede every narrow QRS with a PR interval of 0.16 second, and the rate returns to 74 once suctioning stops. What best explains the slowing?

   • a.A junctional escape rhythm took over during suctioning
   • b.Vagal stimulation slowed the rate of the sinus node
   • c.The sinus node stopped and an atrial focus took over
   • d.A second-degree block dropped every other beat

   答案: b

   解析: Suctioning, vomiting, gagging, and bearing down all stimulate the vagus nerve, which slows the sinus node and produces a transient sinus bradycardia that resolves when the stimulus ends. The P waves stayed upright with a normal PR interval, so the sinus node is still the pacemaker, which rules out a junctional escape rhythm and an ectopic atrial focus; both would change the shape of the P wave or its timing relative to the QRS. A second-degree block dropping alternate beats would leave P waves standing alone with no QRS after them, and none are described. The technician documents the episode and the intervention that provoked it.

6. 6. Rhythm Interpretation

   A six-second strip recorded in one lead contains five premature wide beats, and those beats have two clearly different shapes. What does the difference in shape indicate?

   • a.The premature beats are unifocal and come from a single site
   • b.The premature beats are fusion beats formed in the AV junction
   • c.The premature beats are multifocal and come from separate sites
   • d.The premature beats are supraventricular beats conducted aberrantly

   答案: c

   解析: Premature ventricular complexes that arise from different ventricular sites depolarize the ventricles along different paths, so their QRS shapes differ within the same lead; identical shapes in one lead describe unifocal ectopy. Multifocal ectopy is reported promptly because it points to more widespread ventricular irritability. A fusion beat is a single hybrid complex created when a supraventricular impulse and a ventricular impulse activate the ventricles at the same time, not a set of beats with two repeating shapes. Supraventricular beats conducted aberrantly are preceded by a premature P wave, which these beats lack.

7. 7. EKG Acquisition

   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

   答案: b

   解析: 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.

8. 8. EKG Acquisition

   A patient arrives for a 12-lead EKG wearing a long metal necklace that lies across the chest and metal-framed eyeglasses, and has a stainless steel hip prosthesis. Which is most likely to disturb the tracing?

   • a.The necklace, if it touches an electrode or a lead wire
   • b.The hip prosthesis, since metal in the body conducts
   • c.The eyeglass frames, since metal picks up room noise
   • d.The prosthesis and necklace equally, both being metal

   答案: a

   解析: Metal lying on the skin can bridge across an electrode or drag against a lead wire as the patient breathes and moves, so a necklace draped over the chest is moved aside or removed before the chest electrodes go on. An implanted prosthesis is enclosed in tissue with no connection to the surface or to the cable, and it does not disturb the surface recording. Eyeglass frames sit far from every electrode and from the cable and have no path into the tracing. What matters is not whether metal is present but whether it can contact the recording circuit.

9. 9. Safety & Professionalism

   After a busy morning a technician realizes that a tracing she recorded an hour ago was saved under a different patient's name, and the record has already gone to the reading physician. What should the technician do?

   • a.Report the error to the supervisor at once
   • b.Wait and see whether the physician catches it
   • c.Correct the name in the system and say nothing
   • d.Note it on both charts at the end of the shift

   答案: a

   解析: A tracing filed under the wrong name puts one patient's data in front of a physician who will act on it for someone else, which is both a misidentification event and a disclosure, so it is escalated immediately rather than handled quietly. Prompt reporting lets the department pull the record from the reading queue before an interpretation is signed. Waiting for the physician to notice leaves a wrong result in an active chart. Fixing the name without telling anyone hides an event the facility has to track and may leave the mistaken interpretation in place, and holding the correction until the end of the shift gives the error hours to travel.

10. 10. Anatomy & Physiology

    A premature ventricular beat lands on the downslope of the preceding T wave. Why is that timing dangerous?

    • a.The ventricles have fully recovered, so the beat lands with extra force
    • b.Recovery is uneven, so the beat can trigger fibrillation
    • c.The T wave is where the atria repolarize, so atrial filling is lost
    • d.The AV node is refractory then, so the beat cannot reach the ventricles

    答案: b

    解析: The downslope of the T wave is the relative refractory period, when some ventricular cells have recovered and others have not, and a stimulus arriving into that patchwork can start a chaotic reentrant rhythm such as ventricular tachycardia or ventricular fibrillation. This is the R on T phenomenon, and it is a finding a technician reports promptly rather than interprets. Full recovery of the ventricles happens later, after the T wave has ended, so the idea of a merely forceful beat misses the hazard. Atrial repolarization is buried inside the QRS complex, not in the T wave, and a ventricular beat by definition arises below the AV node and does reach the ventricles.