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The rhythm of this strip is first-degree atrioventricular (AV) block. Both the atrial and ventricular rhythms are regular. Because the rate is regular, I used the 6 second method to determine the heart rate to be 70 beats per minute (BPM). There is a P wave preceding each QRS complex. The P waves are normal and are identical, smooth, rounded, and upright (or positive). They measure 0.12 seconds in duration and 1.5 mm in height. Each PR interval (PRI) is consistently 0.24 seconds long, making it prolonged since it is greater than 0.20 seconds long. Each QRS complex is normal at 0.08 seconds in duration. The QT interval is borderline as, at 0.40 seconds duration, it is exactly half the R-R interval. The ST segment is minimally elevated. Finally, the T wave is 5 mm in height and is abnormal as it is tall and peaked.

A first-degree AV block may be normal in some people, particularly athletes (Aehlert, 2018, p. 196). Increased vagal tone is typically the cause of first-degree AV block in younger people, while fibrotic changes in the cardiac conduction system is a common cause in the elderly (Oldroyd, et al., 2021, Etiology). Other conditions that may cause first-degree AV block include acute myocardial infarction (MI), particularly inferior wall MI, coronary artery disease (CAD), cardiomyopathy, ischemia or injury to the AV node or AV bundle, infections such as acute myocarditis, acute endocarditis, and rheumatic fever; electrolyte abnormalities; valvular heart disease, rheumatoid arthritis, scleroderma, neuromuscular disorders, and medications (Aehlert, 2018, p. 196; Oldroyd, et al., 2021, Etiology).

Nursing care for patients with first-degree AV block primarily consists of assessing for cardiovascular compromise, via questioning the patient about any dizziness, nausea, or chest pain, and monitoring vital signs (Aehlert, 2018, p. 196; Oldroyd, et al., 2021, Etiology). It is very important that the patient is placed on a cardiac monitor to assess for worsening block or a change to a higher-grade block (Aehlert, 2018, p. 196; Oldroyd, et al., 2021, Etiology).

Treatment of first-degree AV block is not necessary if it is not accompanied by signs and symptoms of cardiovascular compromise (Aehlert, 2018, p. 196; Oldroyd, et al., 2021, Treatment / Management). If the block is associated with an MI, then implantation of a pacemaker may be indicated, but this should be delayed as sometimes the block resolves once the patient recovers from the MI (Oldroyd, et al., 2021, Treatment / Management). First-degree AV block in the presence of symptomatic bradycardia should be treated (Aehlert, 2018, p. 197).

Resources

Aehlert, B. (2018). ECGs made easy. Elsevier.

Oldroyd, S., Rodriguez, B., & Makaryus, A. (2021). First degree heart block. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK448164/