NCMA EKG and Cardiovascular Procedures 2 — Questions and Answers

Question 1: When applying limb electrodes for a 12-lead EKG, where are the four limb electrodes placed?

On the shoulders and hips
On the right arm (RA), left arm (LA), right leg (RL), and left leg (LL) — on the inner wrists and inner ankles (Correct answer)
On the upper arms and upper thighs only
On the fingertips of the right hand and left hand, and the big toes

Correct answer: On the right arm (RA), left arm (LA), right leg (RL), and left leg (LL) — on the inner wrists and inner ankles

Standard limb electrode placement: right arm (inner wrist area), left arm (inner wrist), right leg (inner ankle), left leg (inner ankle). The right leg electrode serves as the ground/neutral reference.

Limb electrode placement details: RA (red) — inner aspect of right wrist or forearm; LA (yellow or black) — inner aspect of left wrist or forearm; RL (black or green) — inner aspect of right ankle or lower leg (ground); LL (green or red) — inner aspect of left ankle or lower leg. Electrodes should be placed on fleshy areas, not over bony prominences or muscles (causes artifact). If patient has a limb amputation, AHA recommends moving the electrode to the stump (not shifting to adjacent limb). If patient has a cast or IV, place electrode above the cast/IV site on the same limb. Limb lead reversal (especially RA/LA swap) is the most common EKG error.

Question 2: Atrial fibrillation (A-fib) on an EKG is characterized by which of the following findings?

Regular rhythm with wide QRS complexes
Irregularly irregular rhythm with absent discrete P waves and an irregular baseline (Correct answer)
Regular rhythm with P waves that gradually increase in PR interval before a dropped beat
Regular sawtooth baseline at 300 bpm with regular QRS complexes

Correct answer: Irregularly irregular rhythm with absent discrete P waves and an irregular baseline

Atrial fibrillation is characterized by: absent distinct P waves (replaced by chaotic fibrillatory baseline), irregularly irregular ventricular response (QRS complexes occur at unpredictable intervals), and normal QRS morphology (unless aberrant conduction exists).

Atrial fibrillation ECG features: No distinct P waves — replaced by chaotic irregular fibrillatory activity (f waves) at 350–600/min; Irregularly irregular RR intervals (ventricular response) — NOT regularly irregular; QRS complex is usually narrow (normal conduction) but can be wide if aberrant conduction occurs; Ventricular rate varies; can be rapid, controlled, or slow. A-fib clinical significance: most common sustained cardiac arrhythmia; 5× increased stroke risk due to atrial thrombus formation; management includes rate control, rhythm control, anticoagulation. Compare: Atrial flutter — regular sawtooth P waves at ~300/min with regular or regularly variable QRS; Sinus arrhythmia — varies with respiration, P waves present.

Question 3: During an EKG procedure, you notice the tracing shows a 60-cycle interference pattern (thick fuzzy baseline). What is the most likely cause and solution?

Patient movement; ask the patient to hold their breath
AC (alternating current) electrical interference; check for loose electrodes, ensure patient is not touching metal, and unplug nearby electrical devices (Correct answer)
Low battery in the EKG machine; replace batteries
Wrong speed setting; change from 25 mm/s to 50 mm/s

Correct answer: AC (alternating current) electrical interference; check for loose electrodes, ensure patient is not touching metal, and unplug nearby electrical devices

60-cycle (60 Hz) AC interference appears as a thick, fuzzy, regular oscillation on the baseline. It is caused by electromagnetic interference from nearby electrical sources, loose electrodes, or broken lead wires. Solutions include checking electrode contact, removing electrical devices, and ensuring the patient's limbs are not touching metal.

EKG artifact types and solutions: AC/60-cycle interference — thick fuzzy baseline; causes: loose/dry electrodes, frayed lead wires, patient near electrical equipment, wet alcohol on skin; solutions: check electrode adhesion, dry skin, ensure lead wires not coiled/tangled, unplug nearby electrical devices, use EKG machine's AC filter (though this may affect ST segments); Somatic (motion) artifact — irregular baseline disturbances; causes: patient movement, shivering, talking, Parkinson's tremor; solutions: reposition patient comfortably, warm the room, re-instruct patient; Wandering baseline — slow undulating baseline; causes: breathing, loose limb electrodes, patient talking; solutions: ensure limb electrodes on fleshy areas, ask patient to breathe normally. Good skin prep prevents most artifacts.

Question 4: What does the ST segment on an EKG represent, and why is ST elevation clinically significant?

Atrial repolarization; ST elevation indicates atrial enlargement
Early ventricular repolarization; ST elevation indicates acute myocardial injury or infarction (Correct answer)
AV node conduction; ST elevation indicates first-degree heart block
Ventricular depolarization; ST elevation indicates bundle branch block

Correct answer: Early ventricular repolarization; ST elevation indicates acute myocardial injury or infarction

The ST segment represents early ventricular repolarization — the period between the end of ventricular depolarization (QRS) and ventricular repolarization (T wave). ST elevation in two or more contiguous leads indicates acute myocardial injury and is the hallmark of STEMI (ST-elevation myocardial infarction).

ST segment analysis: Normal: at the isoelectric baseline (same level as TP segment); ST elevation: ≥1 mm (0.1 mV) in limb leads or ≥2 mm in precordial leads in ≥2 contiguous leads is clinically significant; indicates acute myocardial injury/STEMI — requires immediate emergency intervention (percutaneous coronary intervention or thrombolytics); also occurs in pericarditis (diffuse elevation), Prinzmetal's angina, early repolarization (normal variant); ST depression: ≥1 mm in ≥2 contiguous leads; indicates myocardial ischemia, NSTEMI (non-ST elevation MI), reciprocal changes. Contiguous leads: V1–V4 (anterior), II/III/aVF (inferior), I/aVL/V5–V6 (lateral). Medical assistants must alert the physician immediately when ST elevation is noted.

Question 5: Which of the following is a contraindication for a cardiac stress test?

Controlled mild hypertension (140/90 mmHg)
Suspected stable angina requiring evaluation
Acute myocardial infarction (AMI) within the past 2 days (Correct answer)
Moderate obesity without symptoms

Correct answer: Acute myocardial infarction (AMI) within the past 2 days

An acute myocardial infarction (within 2–4 days) is an absolute contraindication to cardiac stress testing because the patient's heart is still acutely injured and further physical stress could cause life-threatening complications.

Absolute contraindications to exercise stress testing (per ACC/AHA): Acute MI within 2–4 days; Unstable angina; Uncontrolled cardiac arrhythmias with hemodynamic compromise; Symptomatic severe aortic stenosis; Uncontrolled symptomatic heart failure; Acute pulmonary embolus or infarction; Acute myocarditis or pericarditis; Acute aortic dissection. Relative contraindications (physician weighs risk/benefit): Left main coronary stenosis; Significant hypertension (SBP >200, DBP >110); Electrolyte abnormalities; Hypertrophic obstructive cardiomyopathy. The medical assistant's role: obtain 12-lead EKG before stress test, monitor BP and ECG during test, recognize indications to stop (chest pain, ST depression, severe hypertension, arrhythmias, patient requests to stop).

Question 6: A Holter monitor records cardiac activity over 24–48 hours. What is it primarily used for?

Monitoring blood pressure continuously over 24 hours
Detecting intermittent arrhythmias and correlating cardiac symptoms with ECG findings over an extended period (Correct answer)
Providing a permanent pacemaker backup during cardiac recovery
Measuring continuous oxygen saturation in cardiac patients

Correct answer: Detecting intermittent arrhythmias and correlating cardiac symptoms with ECG findings over an extended period

A Holter monitor is a continuous ambulatory ECG recorder worn by the patient for 24–48 hours (or longer with event monitors). Its primary purpose is to detect arrhythmias or ECG changes that occur intermittently and may not be present during a routine in-office EKG.

Holter monitor indications: unexplained syncope or near-syncope; palpitations; suspected arrhythmia not captured on resting ECG; post-ablation monitoring; assessment of pacemaker function; stroke with suspected arrhythmia cause (A-fib). Patient instructions: maintain an activity/symptom diary; avoid MRI; keep device dry; continue normal activities. The monitor records 2–3 continuous ECG channels. After the recording period, data is downloaded and analyzed by a technician/cardiologist for arrhythmias, conduction abnormalities, and ST changes. Event monitors record for 30 days when activated by patient symptoms. Implantable loop recorders (ILR) are inserted under the skin for years of monitoring in refractory cases.

NCMA EKG and Cardiovascular Procedures 2

When applying limb electrodes for a 12-lead EKG, where are the four limb electrodes placed?