Breathing maneuvers, i.e. hyperventilation followed by breath-holding, have been shown to change coronary dynamics; hyperventilating narrows the coronary arteries, puts stress on the heart, and increases the heart rate, whereas breath-hold dilates the coronary arteries and decreases the heart rate, rest. Heart rate response to hyperventilation has been reported to have high diagnostic accuracy to rule out heart disease. The cardiac stress test, the modality of choice for the initial assessment of patients with suspected coronary artery disease(CAD), is routinely overprescribed by physicians, which exerts a financial burden on the healthcare system. Hence, developing an inexpensive, reliable, and available tool-HR response to breathing maneuvers- may avoid unnecessary referrals for cardiac stress tests by an effective differentiation of patients with CAD from healthy people. This study aims to assess the negative predictive value of the HR response to a 4-minute breathing maneuver for inducible myocardial ischemia, avoiding further stress testing as a gatekeeper.