Which of the following radiopharmaceuticals is NOT appropriate for a left to right cardiac shunt examination using the first pass method?

In a left to right cardiac shunt examination using the first-pass method, the appropriate radiopharmaceuticals are those that can effectively identify blood flow and shunting within the heart. The first-pass technique evaluates the movement of a radiopharmaceutical through the heart chambers, providing crucial information about blood flow dynamics and any abnormalities.

Thallous chloride is not ideal for this purpose because it is primarily used for myocardial perfusion imaging and does not provide the same rapid assessment of blood transit across the heart chambers as the other options. It has a higher affinity for myocardial tissue and requires a different imaging approach, typically better suited for assessing myocardial viability or perfusion rather than shunts.

On the other hand, pertechnetate, sestamibi, and tetrofosmin are all used in techniques that can adequately highlight cardiac functionality and are effective for first-pass examinations. They circulate through the blood and can be easily tracked as they pass through cardiac structures, making them suitable for assessing left-to-right shunts. Therefore, thallous chloride stands out as the less appropriate choice for this specific type of cardiac evaluation.