A nurse is reviewing the cardiac monitor strip for a client who is recovering from an acute myocardial infarction. Which of the following findings should the nurse report to the provider immediately?

A. Sinus tachycardia rate 104/min: Mild sinus tachycardia may occur in response to pain, anxiety, or hypovolemia and is usually not immediately life-threatening. While it should be monitored, it does not require urgent reporting unless it worsens or is accompanied by other concerning signs. B. Two premature ventricular contractions per minute: Occasional PVCs can be benign, especially in a post-MI patient, and may not require immediate intervention. Frequent or paired PVCs, or those occurring in runs, are more concerning for ventricular arrhythmias. C. First degree heart block: This is characterized by a prolonged PR interval but generally does not compromise cardiac output. It is often stable and can be monitored rather than reported as an urgent finding. D. A new onset of atrial fibrillation: New-onset atrial fibrillation following a myocardial infarction increases the risk of decreased cardiac output, thromboembolism, and hemodynamic instability. This arrhythmia requires immediate notification of the provider for assessment and initiation of appropriate interventions such as rate or rhythm control and anticoagulation.