Which stress agent should be given to patients with heart block or a pacemaker?

In the context of patients with heart block or those who have a pacemaker, the preferred stress agent is typically a pharmacological one that does not rely on the intrinsic conduction system of the heart, as the integrity of this system is compromised.

Dobutamine is a positive inotropic agent that increases heart rate and contractility by stimulating beta-adrenergic receptors. It can be safely used in patients with pacemakers since it does not depend on the conduction pathways that are impaired in heart block. In fact, it can be beneficial in enhancing myocardial perfusion in a controlled manner, which is essential for the assessment of cardiac function during imaging studies like PET.

On the other hand, other agents such as adenosine, regadenoson, and dipyridamole primarily act by inducing vasodilation and rely on a functional coronary vascular response, which may not be as effective or reliable in patients with conduction issues. This is primarily due to the fact that adenosine can lead to bradycardia and may further exacerbate conduction abnormalities. Regadenoson and dipyridamole also might not produce the desired effect in the presence of severe conduction defects as they can lead to increased heart rates which may not properly stimulate the