Final answer:
Pre-operative cardiac testing for a patient with an active lifestyle and a history of left anterior fascicular block could involve non-invasive stress testing with thallium-201, pending further clinical risk assessment.
Step-by-step explanation:
The most appropriate pre-operative cardiac testing for a 70-year-old male with a history of left anterior fascicular block and premature atrial contractions (PACs), who is active and swims regularly, would be dictated by current clinical guidelines which generally recommend non-invasive stress testing for patients with at least two clinical risk factors undergoing high-risk surgery. However, considering the patient's ECG changes were from 2 years ago and his regular activity level indicating a certain level of fitness, further clinical assessment and risk stratification is essential to determine the necessity of pre-operative cardiac testing. Key considerations include the patient's functional capacity, current symptoms, and the nature of the planned surgery. Administering thallium-201 during a stress test could be one such modality used to analyze heart function and blood flow if non-invasive testing is indicated based on the patient's risk profile.