When assessing Normal Sinus Rhythms Remember the following values.
Rate…………. Between 60–100
P waves…….. Present
QRS ………….. Normal (0.08–0.12 sec)
Basic ECG Assessment
Follow these steps for basic electrocardiogram interpretation.
- Determine ventricular rate.
- Determine QRS duration and shape.
- Identify P waves and determine if a P wave precedes every QRS complex.
- If more than 1 P wave precedes a QRS complex, determine ratio of P waves to QRS complex (ex., 4:1, 3:1, 2:1).
- Is P wave shape consistent?
- Determine atrial rate and rhythm.
- Determine P-R intervals and if they are consistent.
Analyzing the P-R Interval (PRI)
- PRI is consistent and between 0.12 and 0.20 sec (3–5 small boxes): This is considered a normal PRI.
- PRI is 0.12 sec (3 small boxes): consider junctional rhythm.
- PRI is longer than 0.20 sec (5 small boxes), it remains consistent in length from PRI to PRI: Consider 1 AV block.
- PRI undergoes progressive lengthening until a QRS is dropped: Consider 2 AV block, type I.
- PRI is consistent; however, there are additional P waves that do not preceed a QRS complex: Consider 2 AV block, type II.
- PRI is not consistent, nor is there any correlation between the P wave and the QRS: Consider 3 AV block (CHB).
Analyzing the QRS Complex
- QRS between 0.08 and 0.12 (2–3 small boxes): Consider normal.
- QRS 0.12 sec, “wide and bizarre”: Consider ventricular ectopy.
- QRS 0.12 sec (3 small boxes), with notched or “rabbit ears” appearance: Consider BBB.
- QRS preceded by 1–2 very narrow “spikes”: Think pacemaker.