NHA EKG Technician (CET) — All Questions

A patient with a demand pacemaker programmed to 60 beats per minute is on telemetry. The strip shows long pauses with no pacing spikes at all during them, and each pause follows a burst of muscle noise on the baseline. What is the most likely explanation?

• a.Oversensing, in which noise is read as beats and output is withheld✓
• b.Failure to capture, since the paced impulses produce no complexes
• c.Failure to sense, since the generator fires without regard to the beats
• d.Battery depletion, to be reported to the supervisor as a failed device

A demand pacemaker withholds its output whenever it senses electrical activity, so when it counts muscle tremor or other electrical noise as ventricular beats it stops pacing and the rate falls below the programmed 60 beats per minute; the pauses tracking the noise bursts are the giveaway. Failure to capture shows spikes that produce no complex, yet during these pauses there are no spikes at all. Failure to sense produces the opposite picture, extra spikes competing with the patient's own beats. Battery status is determined by device interrogation rather than from a rhythm strip, and declaring a device failed is not the technician's call.

A strip shows a regular wide-complex tachycardia at 160 beats per minute. Which additional finding on that strip would most support ventricular tachycardia rather than a supraventricular rhythm conducted with aberrancy?

• a.QRS complexes that measure more than 0.12 second across the strip
• b.T waves that point in the same direction as the QRS complexes
• c.P waves marching through at an unrelated rate of 80 per minute✓
• d.An R-R interval that stays regular from the first to the last beat

Independent P waves continuing at their own slower rate through the tachycardia show AV dissociation, which strongly favors a ventricular origin; capture beats and fusion beats point the same way. A QRS wider than 0.12 second is present in both possibilities, since aberrant conduction widens the complex too, so width alone separates nothing. Regularity is likewise shared by both. T waves in wide-complex beats usually point opposite the QRS, so concordant T waves are not a feature that favors either. Whatever the strip suggests, the technician reports a wide-complex tachycardia and gets help rather than naming the mechanism.

A monitored patient's rhythm changes to a ventricular rate of 34 beats per minute with wide QRS complexes and P waves bearing no relationship to them. The patient says he feels faint and looks pale. What should the technician do?

• a.Recheck the electrodes, since a rate that low is usually a lead problem
• b.Report the strip to the supervisor at the end of the current monitoring round
• c.Ask the patient to sit upright so his ventricular rate will come up
• d.Stay with the patient and alert the nurse at once, per facility policy✓

A new complete heart block at 34 beats per minute in a patient with symptoms is an emergency finding, so the technician stays with the patient, summons the nurse or the emergency response as facility policy directs, and keeps the strip running for the team. Holding the tracing until the end of the round delays care that is needed now. Clean, regular wide complexes with independent P waves are a real rhythm and not a lead problem, so troubleshooting electrodes first wastes time. Sitting a lightheaded patient upright does not restore conduction through a blocked pathway and adds a fall risk.

A sinus strip at 70 beats per minute contains one wide, bizarre beat sandwiched between two consecutive sinus beats, and the surrounding sinus P-P and R-R intervals are undisturbed. What is the wide beat called?

• a.A ventricular escape beat, since no pause follows it
• b.A fusion beat formed by two impulses meeting in the ventricle
• c.An interpolated premature ventricular contraction✓
• d.A junctional premature beat with aberration

An interpolated premature ventricular contraction falls between two normally timed sinus beats without resetting the sinus node, so no compensatory pause follows it and the underlying cycle continues undisturbed. A ventricular escape beat is late rather than early and appears after a pause when the higher pacemakers have failed, which does not fit a beat squeezed into an intact sinus cycle. A fusion beat is a single hybrid complex whose shape lies between that of a sinus beat and that of a ventricular beat. A junctional premature beat is narrow unless it is conducted aberrantly, comes early with an inverted P wave near the complex, and usually resets the underlying rhythm.

A strip shows a rapid wide-complex rhythm whose QRS complexes change amplitude gradually and appear to twist around the baseline. Which measurement from the same patient's earlier tracing is most closely related to this rhythm?

• a.A PR interval of 0.22 second measured on the earlier tracing
• b.A QRS duration of 0.10 second measured on the earlier tracing
• c.A corrected QT interval of 0.52 second measured on the earlier tracing✓
• d.An R-R interval that varied with breathing on the earlier tracing

The twisting pattern is torsades de pointes, a polymorphic ventricular tachycardia that arises when the QT interval is prolonged, and a corrected QT of 0.52 second is well beyond the usual upper limits of about 0.44 second in men and 0.46 second in women. A PR interval of 0.22 second is a first-degree AV block, a delay in conduction into the ventricles that does not set up this rhythm. A QRS of 0.10 second is within the normal range of less than 0.12 second. R-R intervals that vary with breathing describe sinus arrhythmia, a normal variant.