As an RN, your EKG job was usually recognition — is this a normal sinus rhythm or not? As an FNP in primary care, you'll be interpreting EKGs ordered for chest pain, palpitations, hypertension workup, pre-op clearance, and routine baselines. The FNP boards tests this. Most candidates underprepare for it.
Here's the framework I teach my students for FNP-level EKG interpretation.
You don't need cardiology-level expertise. You need to identify what's normal, recognize what's dangerous, and know when to refer.
The Six-Step Approach
Every EKG you read in primary care should run through these steps in order.
- Rate — normal 60 to 100.
- Rhythm — regular vs. irregular; sinus origin or not.
- Axis — normal, left, or right deviation.
- Intervals — PR (0.12 to 0.20), QRS (<0.12), QT (corrected <0.45 male, <0.46 female).
- Hypertrophy — left or right ventricular.
- Ischemia or infarction — ST depression, ST elevation, Q waves, T wave inversion.
The Most-Tested Findings on the FNP Exam
Atrial fibrillation
Irregularly irregular, no discernible P waves. The exam wants you to order rate control (beta blocker or CCB), assess CHA2DS2-VASc score, and decide on anticoagulation. Score ≥2 in men or ≥3 in women → anticoagulate.
Left ventricular hypertrophy
Sokolow-Lyon criteria: S in V1 + R in V5 or V6 ≥ 35 mm. Common in chronic hypertension. Implies long-standing pressure overload.
STEMI vs. NSTEMI
ST elevation in 2 or more contiguous leads = STEMI. Cath lab activation. Time is muscle. Anything else with troponin elevation = NSTEMI. Less time-critical but still admission.
First-degree AV block
PR > 0.20 seconds, every beat. Generally benign in primary care. Watch over time.
Right bundle branch block
QRS > 0.12, rabbit-ear pattern in V1 (rSR'), wide S in lateral leads. Often benign in isolation.
Left bundle branch block
QRS > 0.12, broad notched R in V5/V6, deep wide S in V1. New LBBB is a STEMI equivalent in the setting of chest pain.
Clinical Pearl: A new LBBB in a patient with chest pain should be treated as if it were a STEMI until proven otherwise. This is a tested concept.
The Five Lead Groups
Memorize which leads look at which wall of the heart. This determines which coronary artery is involved.
- Inferior: II, III, aVF → right coronary artery
- Lateral: I, aVL, V5, V6 → left circumflex or LAD
- Anterior: V1 through V4 → left anterior descending
- Septal: V1, V2 → LAD
- Posterior: tall R in V1, ST depression V1–V3 (reciprocal) → right or circumflex
The FNP exam may show you an EKG with ST elevation in II, III, aVF and ask which artery is involved. You answer: right coronary.
When to Refer
Refer to cardiology when you see:
- New-onset atrial fibrillation
- Any second- or third-degree AV block
- QTc > 500 (risk of torsades)
- Unexplained left ventricular hypertrophy
- New bundle branch blocks
- Any sign of ischemia or infarction
What to Drill
Get a stack of practice EKGs. Run every one through your six-step framework. Time yourself. By the time you sit for boards, the six steps should take 30 seconds, not 3 minutes.
EKG interpretation is procedural memory. It rewards drilling.