Which medication is most likely to produce a false positive result during an exercise stress test?

The medication most likely to produce a false positive result during an exercise stress test is Digitalis. This is primarily due to the effects Digitalis has on the heart's electrical activity, particularly how it can alter the ST segment on an electrocardiogram (ECG). Patients taking Digitalis may exhibit characteristic changes on the ECG, such as scooped ST segments or other alterations that could be misinterpreted as ischemic changes, leading to a false positive result during stress testing.

Exercise stress tests are designed to assess how well the heart functions under stress, and the interpretation of the results hinges significantly on the ECG readings. Medications like Nitrates and Calcium channel blockers generally work to improve coronary blood flow and can help in exercise tolerance, making them less likely to cause misinterpretation of results. Propranolol, a beta-blocker, mainly reduces heart rate and myocardial demand, which can also help clarify test results rather than produce misleading indicators.

In contrast, Digitalis's impact on electrical conduction and the ST segment can create confusion during the analysis of the stress test results, making it the medication that most commonly results in a false positive finding in this context.