Agent | Dose | Receptor/mediator | Comments |
Endothelium independent vasodilators | |||
Adenosine | Bolus: 12–36 μg Infusion: 1–2 mg/min | Purine receptors | Causes transient heart block. Causes maximal coronary vasodilatation and is also used for the assessment of fractional flow reserve |
Glyceryl trinitrate | Bolus: 50–200 μg | Nitric oxide donor | Predominant action on epicardial vessels |
Papaverine | Bolus: 4–12 mg | Opiate derivative causing vascular smooth muscle relaxation | Causes maximal coronary vasodilatation. Potentially arrhythmogenic |
Sodium nitroprusside | Infusion: 5–40 μg/min | Nitric oxide donor | Predominant action on coronary resistance vessels |
Endothelium dependent vasodilators | |||
Acetylcholine | Bolus: 1–100 nmol Infusion: 1–1000 nmol/min | Muscarinic receptors | Causes transient heart block. Target effective intracoronary concentration of 10-8 to 10-6 M. May cause paradoxical vasoconstriction in presence of atheroma |
Bradykinin | Bolus: 60–600 pmol Infusion: 30–2500 pmol/min | Bradykinin type 2 receptor | Tachyphylaxis and chest discomfort may occur |
Substance P | Infusion: 5–40 pmol/min | Neurokinin type 1 receptor | |
Endothelium dependent vasoconstrictors | |||
L-NMMA | Infusion: 32–64 μmol/min | Nitric oxide synthase inhibitor | Slow onset and offset of action (10–20 minutes) |
Boluses should be given in 2 ml followed by 3 ml saline flush. The bolus dose should be reduced by 30–50% for right coronary artery injection.
To avoid directly influencing coronary flow, infusion rates are usually low at 1–2 ml/min.
Adenosine and papaverine may additionally cause endothelium dependent flow associated epicardial vessel vasodilatation.
Except L-NMMA, all agents have a rapid onset and offset of action with flow velocity usually returning to baseline within ∼2 minutes.