Role of Adenosine in Cardiac Catheterization
Adenosine is the preferred pharmacological agent for inducing maximal coronary hyperemia during cardiac catheterization procedures, primarily used to assess the functional significance of coronary stenoses through fractional flow reserve (FFR) and coronary flow reserve (CFR) measurements. 1
Mechanism of Action
- Adenosine causes vasodilation primarily of the coronary microcirculation with minimal effect on epicardial conduit arteries, acting through A2 receptors to increase cytosolic cyclic adenosine monophosphate as the second messenger for vasorelaxation 1, 2
- It serves as an important endogenous regulator of coronary blood flow during both stress and ischemia 1, 2
- Intracoronary Doppler flow catheter studies have demonstrated that adenosine produces maximum coronary hyperemia in approximately 95% of cases within 2-3 minutes of infusion onset 2
Administration Routes and Dosing
Intracoronary Administration
- Dosage: 30-60 μg for left coronary artery; 20-30 μg for right coronary artery 1
- Onset: Rapid (5-10 seconds) 1
- Duration: Short (30-60 seconds) 1
- Incremental doses may be necessary to achieve maximal hyperemia, particularly when initial FFR values fall in the borderline range (0.75-0.90) 3
- A single high dose of 42 μg for both left and right coronary arteries is sufficient to achieve maximum hyperemia in most patients 3
Intravenous Administration
- Dosage: 140 μg/kg/min through a large, preferably central vein 1
- Onset: 1-2 minutes to achieve steady-state maximum hyperemia 1
- Duration: 1-2 minutes after discontinuation 1, 2
- Preferred for aorto-ostial lesions and when recording pressure pullback curves to differentiate focal from diffuse disease 1
Clinical Applications
- Assessment of fractional flow reserve (FFR) to determine the functional significance of intermediate coronary stenoses 1
- Measurement of coronary flow reserve (CFR) to evaluate microvascular function 1
- Index of microvascular resistance (IMR) calculation to assess microvascular dysfunction 1
- Complementary use of FFR, CFR, and IMR provides comprehensive assessment of both epicardial and microvascular coronary disease 1
Safety Profile
- Generally safe at recommended intracoronary or intravenous dosages 1
- Common side effects include:
- Serious complications are rare:
Important Considerations and Precautions
- Absolute contraindication: Asthma for intravenous adenosine administration due to risk of bronchospasm 1, 4
- Patients should avoid Valsalva maneuvers during intravenous infusion as this can interrupt continuous drug delivery and cause fluctuations in coronary blood flow and distal pressure 1
- During exaggerated respiratory activity, FFR should be taken as the lowest value of Pd/Pa during the respiratory cycle 1
- Withdraw guiding catheter slightly out of ostium if any sign of obstruction is present or if using a guiding catheter with side holes 1
- For research purposes, guiding catheters without distal side holes are recommended 1
- Adenosine is preferred over papaverine due to papaverine's potential for QT prolongation and ventricular arrhythmias 1
Technical Considerations for Optimal Measurement
- Administer intracoronary isosorbide dinitrate (2 mg) or nitroglycerin (200 μg) at least 2 minutes before FFR measurement to abolish epicardial vasoconstrictor tone 1
- Ensure proper zeroing and calibration of pressure systems to avoid measurement errors 1
- Be aware that suboptimal guide catheter engagement may result in inadequate delivery of bolus adenosine, producing submaximal hyperemia and limiting the accuracy of FFR and CFR 1
- For stability, 2 mg/mL adenosine solutions in 0.9% sodium chloride can be stored for up to 14 days at room temperature or under refrigeration 5