What can cause a false positive in a stress test?

A false positive in a stress test can occur due to various factors, one of which is the impact of recent smoking. Smoking can affect cardiovascular response during the test, leading to altered heart rate and blood pressure responses that may mimic ischemic changes on the electrocardiogram (EKG). This can cause the test to suggest that there is a problem with blood flow to the heart when there actually isn’t one.

Considering other factors that could cause false positives, high blood pressure is generally related to physiological responses rather than indicative of ischemia during the test itself. Dehydration can affect performance during the stress test but doesn't typically create electrocardiographic changes indicative of ischemia. Electrode misplacement can also lead to erroneous readings, but it is a less common cause compared to the systemic effects seen with smoking.

Therefore, the relationship between recent smoking and the potential alteration of the body’s response during a stress test makes this choice particularly relevant in understanding factors that can lead to misleading results.