Recognizing Patterns on a Resting 12-Lead Electrocardiogram

Abstract

Scenario: During an annual physical examination, a healthy 55-year-old man who works as a long-haul truck driver had a routine 12-lead electrocardiogram (ECG) recorded. Overall, he had no complaints and was asymptomatic. His body mass index was within normal limits, and he was taking simvastatin for high cholesterol and lisinopril for high blood pressure (current blood pressure, 128/78 mm Hg).Sinus rhythm at 85 beats per minute with first-degree atrioventricular (AV) block and premature ventricular contractions (PVCs) in a trigeminy pattern.Trigeminy is a pattern of PVCs occurring in a series of 3 heart beats, either 2 normal sinus beats followed by a PVC (as in this example) or 1 normal sinus beat followed by 2 PVCs. Trigeminy is not common, is often transient, and can disturb the normal contraction and cardiac output of the heart because a premature impulse interrupts sinus rhythm. In this case, there are more sinus beats than PVCs, most likely supporting normal cardiac output. The PVCs are similar in morphology, or unifocal, suggesting the origin (focus) is at 1 ventricular site. The etiology of trigeminy is not definitive, but some causes include caffeine, medications (eg, antihistamines), alcohol, anxiety, and heart disease. Of note, the PR interval is slightly prolonged (210 milliseconds), meeting criteria for a first-degree AV block. This occurs when electrical conduction through the AV node is slowed but atrial to ventricular conduction is not interrupted. In this case, the continuous rhythm strip at the bottom of the 12-lead ECG is very helpful in capturing the onset and offset of the PVCs. Also, the low R-wave amplitude may be a sign for hypertensive patients requiring further workup with echocardiography.Although this patient is asymptomatic, options to monitor the patient for a long, continuous period include portable monitors like a Holter or event recorder to improve assessment of the prevalence of the PVCs and other dysrhythmias. Potential modifications that should be recommended to this patient to avoid possible triggers include reducing caffeine intake, managing anxiety, monitoring his blood pressure, and exercising (given the sedentary nature of his profession). In general, first-degree AV block is considered benign, is not traditionally treated, and in this case was not new. However, recent epidemiological research from the Framingham study indicates a relationship between first-degree AV block and a higher risk of hospitalization for heart failure, cardiovascular mortality, and all-cause mortality. Although currently asymptomatic, the patient should monitor for potential symptoms of worsening of cardiovascular health, for example, new-onset palpitations. If symptoms develop and evidence suggests more sustained arrhythmia, an echocardiogram may be warranted.