A 60-year-old male is admitted to the postanesthesia care unit (PACU) following an uneventful endovascular repair of an abdominal aortic aneurysm. On arrival, his BP is 140/90 and his heart rate is 110. Finger oximetry is 96%. He made 100 mL of urine during the previous hour. He is breathing comfortably with face mask oxygen. The nurse calls you because he is beginning to have a bunch of premature ventricular contractions (PVCs). When you arrive at the patient’s bedside, the nurse hands you a rhythm strip (see Figure 24-1):
Rhythm strip which includes two wide complex beats that appear different (multifocal).
1. Does this patient have a high or low risk of underlying cardiac disease?
2. What is the first thing you should ask the nurse to do?
This is a patient with peripheral vascular disease and therefore likely coronary artery disease. He begins to throw multifocal (QRS morphology looks different) PVCs following a stressful, even if “uneventful,” vascular procedure. Therefore, when evaluating this patient, your index of suspicion for myocardial ischemia should be relatively higher.
For any abnormal rhythm, your first step is to ask the nurse to obtain a 12-lead EKG to more fully characterize the rhythm, conduction, and repolarization of the myocardium. While you wait, you can begin by looking at the rhythm strip.
When all the PVCs look the same (monomorphic), the culprit is typically a small bit of myocardium on the edge of a previous myocardial infarction. This bit of ischemic muscle did not die and has become electrically unstable. However, all the impulses activate the ventricles along the same pathway and all the PVCs look the same.
When the shapes (morphology) of the PVCs are different, the activation sites within the ventricles are also different, and something is making the whole myocardium electrically unstable/irritable.
This patient’s PVCs are polymorphic, and are therefore most likely related to a diffuse myocardial process.
The rhythm strip exhibits classical multifocal ventricular ectopy (extra beats from several sites). Most beats are sinus (NSR) with a “narrow” QRS (0.08 second, 80 milliseconds or two little boxes on the ECG paper) following an atrial “P” wave. But then two PVCs appear, each with a unique morphology. Each of them takes at least five little boxes or 0.2 second to completely activate the ventricles. This is termed “aberrant ventricular conduction.” When an electrical impulse begins at the A-V node and travels down the high-velocity Purkinje fibers, the entire ventricles activate rapidly (0.08 second or a “narrow” QRS complex). When activation of the ventricles begins somewhere “ectopic” within the ventricular muscle, the impulse must travel along back dirt roads before it gets to the Purkinje superhighway. Activation of the ventricles takes a ...
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