American Journal of Critical Care. 2004;13: 519-520
A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses ECG interpretation for clinical practice. We welcome letters to the Editors regarding this feature.
Premature Beats
By
Michele M. Pelter, RN, PhD and
Mary G. Adams, RN, PhD.
From
Washoe Health System and the School of Nursing, University of Nevada, Reno, NV (MMP), and the School of Nursing at State University of New York at Buffalo (MGA).
Scenario: This 12-lead ECG was obtained in a 79-year-old male patient presenting for an elective cardiac catheterization procedure. The cardiac catheterization was ordered because the patient has experienced increasing chest pain during the past 2 weeks. The patient has a history of coronary artery disease, anterior myocardial infarction (MI), and hypertension.
Interpretation: Normal sinus rhythm at 75 beats per minute with a premature junctional complex (PJC); ST T-wave morphology suggestive of recent anterior myocardial injury; and Q waves in V2 and V3, indicating an anterior infarct.
Rationale
Looking at the rhythm strip, the R-R interval is regular until the sixth beat, at which time a premature beat occurs. There is a visible P wave prior to the QRS complex; however, the P wave is inverted (lead II), indicating that the impulse was generated outside of the sinus node and then conducted retrogradely (backward) into the atria. The inverted P wave in lead II suggests that the impulse was generated in the AV node, hence the term junctional. The QRS complex remains narrow because normal conduction via the bundle branches proceeds downward into the ventricles. In leads V2, V3, and V4, the ST segments are slightly elevated (>1mm) and the terminal portion of the T wave is negative, suggesting recent injury. The Q waves present in V2 and V3 indicate that anterior infarction has occurred. Given the ST T-wave changes in these same leads, it is possible that this MI was a recent event.
Nursing Actions
The etiology of PJCs includes normal finding, stress, caffeine, alcohol, heart failure, myocardial ischemia, pericarditis, valvular heart disease, coronary artery disease, lung disease, electrolyte abnormalities, and excessive vagal tone. The patient’s history and ECG both support that the etiology of the PJC is most likely due to myocardial ischemia. Given the patient’s increased chest pain during the past 2 weeks and the ST T-wave findings, an acute MI should be ruled out (ie, troponin I). A prior 12-lead ECG would be helpfulto determine if the Q waves in V2 and V3 are new.
