It’s not hieroglyphic. Let me be specific. Our notion of heart motion can be un-sci-en-tif-ic.
That’s a Blood Hound Gang inspired rhyme to illustrate how the EKG can appear incoherent to a novice nurse who fails to employ a systematic approach to interpreting electrophysiology. I have included a brief summary of key points concerning the EKG, along with a 5-step approach to help students and new graduate nurses grasp some seemingly difficult concepts…
The EKG is part of the cardiovascular examination. In isolation, the EKG can only provide discrete information. In order to make a complete diagnosis, the nurse must gather and evaluate several data sets, including:
– Laboratory Data
– Physical Exam
– Health History
Incorporating knowledge of the physical status of the patient is essential. In the clinical setting, the nurse must be able to correlate EKG findings with the patient’s appearance and complaints. For example, a patient may exhibit dominant S-waves in leads V5 or V6 with a dominant R-wave in V1. The nurse may suspect right ventricular hypertrophy but the diagnosis is made all the more easy if the patient presents with a complaint of shortness of breath as opposed to an ankle sprain.
The components of the cardiovascular examination and their interplay are important in interpreting the clinical presentation of the patient. Dysrhythmias, or arrhythmias, are disorders of the formation or conduction of the electrical impulses within the heart. Changes in the conduction of the heart may be evidenced by decreased pumping action of the heart, failure to deliver oxygenated blood, or decreased blood pressure, to name a few. Dysrhythmias are diagnosed by analyzing the EKG and named according to the site of origin of the impulse and the mechanism of formation or conduction involved.
The EKG is the recording of the heart’s electrical activity, which is easily attainable and non-invasive. Like other muscles, the heart contracts in response to electrical depolarization of the muscle cells. The EKG reveals:
– Chamber Enlargement
– Conduction Defects
– Signs of Drug & Electrolyte Disorders
– Electrical Activity Related to Disease States
The EKG does NOT provide information about the mechanical activity of the heart. It can appear normal despite the presence of a pathological cardiac condition. EKG’s must be correlated with the clinical situation and serial EKG’s can be very useful.
All cardiac cells have the quality of automaticity, which is the ability to generate their own action potentials. The ability to spontaneously generate muscle contractions is a unique quality that allows the cardiac muscle to beat continuously without activation from nerves fibers. Rhythmicity is the ability to generate these potentials in a regular, repetitive manner. Gap junctions between cells allow the action potential from one cell to spread rapidly to all cells in the heart. This results in the heart acting as one large cell, in a sense. This coordination is necessary to mechanically pump blood in the proper sequence. Unfortunately, the electrical connectivity means that activation of any cell can inadvertently active the heart as whole.
- RATE: How fast heart beats. Rate of both atria & ventricles. How many R’s in a 6 second strip X 10. <OR> The number of big boxes (o.2 seconds) between R-waves divided into 300.
- RHYTHM: Regular or irregular. Is the R to R distance constant? (A-fib, Sinus Arrhythmia)
- P: Can you identify a P-wave? Are their P-waves for every QRS complex? Is there a QRS for every P? (BLOCKS, PAC)
- QRS: Can you identify a QRS? It should be 0.06 – 0.11 (> 1 small box but < 3 small boxes). Q-wave (MI) or delta wave (WPW) or widened (PVC)?
- PR-interval: Measure PR-interval. It should be 0.12 – 0.20 (< 5 small boxes/1 big box). Is it constant? May represent a delay in conduction or AV node block.
This extremely simplified version is no substitute for a further exploration of all arrhythmias, ST-changes, axis deviations, T-wave abnormalities, and other more advanced topics. However, this article should represent a good start to interpreting EKG’s.