EKG Acquisition practice questions

Answer: B) The signals can merge and distort those leads

• AIncorrect. It distorts.
• BCorrect. Keep electrodes separate.
• CIncorrect. It distorts the signals.
• DIncorrect. It can distort.

Answer: A) Inverted P wave and QRS in lead I with an upright aVR

RA/LA reversal inverts lead I and swaps aVR with aVL, so a negative lead I with an upright aVR (and normal chest leads) suggests the arm electrodes were switched.

• ACorrect. Swapping RA and LA flips lead I and exchanges aVR and aVL. An inverted lead I with a positive aVR, while the precordial leads look normal, points to arm-electrode reversal.
• BIncorrect. This is the expected pattern in sinus rhythm with correctly placed limb electrodes.
• CIncorrect. Normal R-wave progression involves the precordial leads, which arm-electrode reversal does not affect.
• DIncorrect. A wandering baseline usually comes from patient movement, breathing or poor electrode contact. It is not a sign of a lead reversal.

Answer: D) Midaxillary, V4 level

• AIncorrect. That is V4.
• BIncorrect. That is V5.
• CIncorrect. That is V1.
• DCorrect. V6 is on the midaxillary line at the V4 level.

Answer: B) Relaxed at their sides

• AIncorrect. This tenses muscles.
• BCorrect. Tense muscles cause artifact.
• CIncorrect. This interferes with chest leads.
• DIncorrect. This causes artifact.

Answer: C) Red

• AIncorrect. IEC uses green for the left leg.
• BIncorrect. That's the AHA color.
• CCorrect. AHA uses white for the right arm.
• DIncorrect. IEC uses yellow for the left arm.

Answer: B) Heart rate reaches 85% of the age-predicted maximum (220 minus age)

A common endpoint for an exercise stress test is reaching 85% of the age-predicted maximum heart rate (220 minus age). Rising blood pressure, rising heart rate, and faster breathing are normal responses to exercise.

• AIncorrect. Systolic pressure normally rises with exercise. Blood pressure becomes a reason to stop when systolic pressure drops from baseline or when the patient has a marked hypertensive response.
• BCorrect. Reaching the target heart rate, 85% of the age-predicted maximum, is a standard endpoint. Tests are also stopped for symptoms, ECG changes, or when the patient asks to stop.
• CIncorrect. Sweating and faster breathing that match the workload are expected during exercise. Marked shortness of breath or signs of poor perfusion are reasons to stop.
• DIncorrect. Heart rate is expected to rise at each stage. The test continues until the target rate or another endpoint is reached.

Answer: C) Left tilt

• AIncorrect. This adds artifact and fall risk.
• BIncorrect. This can worsen symptoms.
• CCorrect. Left tilt relieves pressure on the vena cava.
• DIncorrect. Adjust her position.

Answer: B) Line-powered electrical equipment plugged in close to the lead wires

60-cycle (AC) interference shows up as perfectly regular, fine oscillations that thicken the baseline. It comes from nearby line-powered electrical equipment and is fixed by removing or moving the source and checking the leads.

• AIncorrect. Shivering causes muscle (somatic) tremor artifact, which shows up as irregular low-amplitude oscillations of varying speed, not a perfectly regular pattern. A still, relaxed patient also makes this unlikely.
• BCorrect. AC (60-cycle) interference appears as perfectly regular fine oscillations at 60 per second, and electrical equipment of any kind near the patient or leads can cause it. Unplugging or moving the equipment and checking lead connections usually fixes it.
• CIncorrect. Breathing causes the baseline to drift slowly up and down (wandering baseline). It does not cause fine, rapid, regular oscillations.
• DIncorrect. Talking and movement cause irregular motion and muscle artifact. It is erratic, not uniform, and wouldn't happen in a patient lying still.

Answer: B) 5

At 25 mm/s each small box is 0.04 s and each large box (5 small boxes) is 0.20 s, so 5 large boxes make 1 second.

• AIncorrect. One large box (5 mm) equals 0.20 seconds at 25 mm/s, not a full second.
• BCorrect. Each large box is 0.20 seconds, so 5 large boxes (25 mm) equal 1 second.
• CIncorrect. Ten large boxes equal 2 seconds (10 × 0.20 s).
• DIncorrect. Twenty-five is the number of small boxes (25 × 0.04 s) in 1 second. Twenty-five large boxes would equal 5 seconds.

Answer: B) Up to about 30 days

Event monitors are worn for up to about 30 days to capture infrequent symptoms. Holter monitors cover 24 to 48 hours, and implanted loop recorders can stay in place for 3 or more years.

• AIncorrect. This is the usual length of Holter monitoring, which records continuously and suits symptoms that happen daily.
• BCorrect. An event monitor can be worn for up to 30 days. That gives a better chance of capturing symptoms that happen less often than daily.
• CIncorrect. This applies to an implanted loop recorder, which is placed under the skin. It does not apply to an external patient-activated monitor.
• DIncorrect. One night is far too short to catch symptoms that happen only a few times a month.