Final answer:
A decrease in levels of cardiac biomarkers such as creatine kinase MB and cardiac troponin is the most reliable indicator of successful reperfusion after thrombolytic therapy for an MI.
Step-by-step explanation:
The most reliable indicator that reperfusion has occurred following thrombolytic therapy after a myocardial infarction (MI) is a decrease in cardiac biomarker levels. When the blocked coronary artery is successfully reopened, levels of biomarkers such as creatine kinase MB and cardiac troponin, which are released into the blood by damaged heart muscle cells, begin to normalize.
These biomarkers are crucial in diagnosing an MI alongside other tools such as ECG, echocardiography, or cardiac MRI. It's also important to monitor the patient for clinical signs of improved heart function and relief from ischemic symptoms. In contrast, an increased heart rate is not a reliable indicator of successful reperfusion, as it could be influenced by various factors and does not directly reflect the resolution of the arterial blockage that caused the MI.