American Journal of Critical Care. 2007;16: 93-94
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.
Evaluating Pacemaker Function With Full Disclosure
By
Mary G. Carey, RN, PhD and
Michele M. Pelter, RN, PhD.
From the School of Nursing at the State University of New York at Buffalo (MGC) and Renown Health and Orvis School of Nursing, University of Nevada, Reno, Nev (MMP).
Scenario: A 68-year-old woman with a ventricular pacemaker was admitted to the telemetry unit for exacerbation of congestive heart failure. The nurse noticed changes in the patient’s cardiac rhythm on telemetry, so she examined a 30-second strip of lead II from the telemetry’s full disclosure software (below). Because the full disclosure does not have an electrocardiogram (ECG) grid on it, the nurse zoomed in on the onset of the rhythm change.
Interpretation: Sinus bradycardia with an intermittent wide QRS rhythm (accelerated ventricular escape rhythm versus ventricular pacing) and a premature junctional contraction (PJC).
Rationale
The underlying rhythm is normal until the sinus node fails to fire and the heart rate falls below 50/min (after sixth beat). After the pause, the rate is slower, there are no P waves, and the QRS complex widens and changes morphology from Rs to QS with notching. All of these changes suggest either an accelerated ventricular escape rhythm or ventricular pacing. During a recurrence of the cardiac rhythm change, a 12-lead ECG was obtained (not shown) and pacemaker spikes were notable, indicating that the first change in cardiac rhythm seen above is due to ventricular pacing. After 6 seconds of pacing, there is an intrinsic P wave and pacemaker is appropriately inhibited from further pacing until the last line, when there is another pause after a PJC (inverted P wave) and again the pacer appropriately fires until inhibited by an intrinsic P wave. Therefore, the ventricular pacemaker is functioning properly.
Nursing Actions
Many hospital ECG monitors have full disclosure capability, allowing for storage of ECG data. This feature means clinicians can go back in time to evaluate cardiac rhythms and identify the onsets and offsets of arrhythmias. The retrospective capabilities of full disclosure aid clinicians in careful yet efficacious cardiac monitoring. A limitation with using the full disclosure feature is that certain diagnoses require standard ECG format or evaluation of multiple ECG leads (ie, ST-segment deviation). In such cases, full disclosure can help guide the clinician to the period of interest, at which point the appropriate measurement tools (grid and calipers) can be applied.
