Stress echocardiography is a diagnostic procedure utilizing echocardiography---an ultrasound test of the heart. This test visualizes the heart muscle at rest and under stress to evaluate for signs of coronary artery disease. A cardiologist then analyzes the images to determine if any part of the heart muscle's ability to pump is diminished during stress. If so, it is suggestive of a blockage in a coronary artery. Several drugs can interfere with the interpretation of the test. Patients are advised to stop these substances prior to undergoing stress echocardiography.
Beta-blockers
The accuracy of a stress test, including stress echocardiography, depends on the patient achieving a calculated target heart rate based on age and sex. Failure to reach the target heart rate during a stress test compromises the interpretation of the test. According to Cardiovascular Pharmacology Concepts, beta-blockers such as atenolol or metoprolol, decrease heart rate and blunt the heart rate response to stress. Beta-blockers also depress the pumping ability, or contractility, of the heart, limiting the interpretation of wall motion by echocardiography. Some cardiac testing laboratories recommend holding calcium-channel blockers before stress echocardiography for similar reasons.
Nitrates
Nitrate-containing drugs, such as nitroglycerin or isosorbide dinitrate, dilate blood vessels. Nitrates are commonly used to treat angina, chest pain due to inadequate blood supply to the heart. According to a 2004 study published in "Cardiovascular Ultrasound," this can alter how blood is distributed to the heart muscle which affects how the heart muscle contracts, limiting the sensitivity of stress echocardiography. Stress echocardiography is more sensitive when there are no drugs in the system that alter the dynamics of the heart.
Caffeine
Accurate interpretation of stress echocardiography is dependent on the heart muscle being subjected to a predictable amount of stress, usually estimated by heart rate and blood pressure. Caffeine limits the sensitivity of stress echocardiography, as reported by Priori.com, by causing a paradoxical slowing of the heart rate with lower concentrations of caffeine and a fast heart rate when higher amounts of caffeine are ingested.
Caffeine also causes a transient increase in blood pressure shortly after ingestion and may have an effect on the ability of blood vessels supplying the heart muscle to dilate during stress, limiting oxygen supply to the heart muscle. These caffeine-induced effects on the cardiovascular system complicates accurate stress echocardiography interpretation. All compounds containing caffeine, including coffee, soda, chocolate and some medicines, should be held for at least 24 hours prior to testing.
