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Coronary flow reserve in patients with chest pain and normal coronary arteries
D R Holdright1, D C Lindsay, D Clarke
1National Heart and Lung Institute, London.
Insights
Coronary flow reserve measurements in patients with chest pain and normal arteries vary by drug. Papaverine and adenosine provide normal values, unlike dipyridamole, suggesting drug choice impacts results.
Area of Science:
- Cardiology
- Physiology
Background:
- Reduced coronary flow reserve is observed in patients with chest pain and normal coronary arteries.
- Dipyridamole is commonly used to assess coronary blood flow, but its effects may vary.
- This study investigates alternative vasodilators, papaverine and adenosine, for assessing coronary flow reserve.
Purpose of the Study:
- To determine if the impaired coronary flow reserve seen with dipyridamole can be replicated with papaverine or adenosine.
- To compare the effects of papaverine, adenosine, and dipyridamole on coronary flow reserve and coronary vascular resistance index (CVRI).
Main Methods:
- 25 patients with chest pain and normal coronary arteries underwent assessment using an intracoronary Doppler flow probe and quantitative angiography.
- Coronary blood flow velocity, coronary flow reserve, and CVRI were measured.
- Pharmacological vasodilation was induced with intracoronary papaverine (8 mg), and in a subset, with papaverine (8 and 10 mg), adenosine (6, 20, 60 micrograms), and intravenous dipyridamole (0.84 mg/kg).
Main Results:
- Intracoronary papaverine (8 mg) resulted in a coronary flow reserve of 4.1 (SEM 0.3) in all 25 patients.
- In eight patients, coronary flow reserve was 4.5 (0.3) with papaverine, 4.8 (0.3) with adenosine, and 3.5 (0.4) with dipyridamole (p=0.08).
- Coronary vascular resistance index (CVRI) was significantly lower with papaverine (0.22) and adenosine (0.21) compared to dipyridamole (0.29) (p<0.05).
Conclusions:
- Measurement of coronary flow reserve and CVRI in patients with chest pain and normal coronary arteries is dependent on the pharmacological stimulus used.
- Papaverine yielded normal coronary flow reserve values in all patients, regardless of exercise test results.
- Dipyridamole showed significantly lower values in patients with a positive exercise test compared to papaverine or adenosine, suggesting potential variability in assessing coronary flow reserve.
Background:
Many studies have shown that coronary flow reserve is reduced in patients with chest pain and angiographically normal coronary arteries. The methods used to assess coronary blood flow have varied, but in nearly all reports dipyridamole has been used to bring about vasodilatation. This study was designed to assess whether the apparent impairment of coronary flow reserve seen with dipyridamole could be reproduced with either papaverine or adenosine, which induce maximum coronary blood flow by different mechanisms.
Methods:
25 patients with chest pain and angiographically normal coronary arteries were studied with an intracoronary Doppler flow probe and quantitative angiography to determine epicardial coronary artery area, coronary blood flow velocity, coronary flow reserve, and coronary vascular resistance index (CVRI, the ratio of resistance after intervention to basal resistance). All patients received papaverine 8 mg. Eight patients with positive exercise tests received intracoronary papaverine (8 and 10 mg), intracoronary adenosine (6, 20, 60 micrograms), and high-dose intravenous dipyridamole (0.84 mg/kg).
Results:
The velocity ratio (peak after intervention: baseline) (mean (SEM)) after 8 mg papaverine was 3.3 (0.2) (n = 25) and the coronary flow reserve was 4.1 (0.3) (n = 25). There were no differences between patients with a positive (n = 16) or negative (n = 9) exercise test. In eight patients coronary flow reserve was measured after increasing doses of papaverine, adenosine, and dipyridamole. Coronary flow reserve was 4.5 (0.3) with papaverine, 4.8 (0.3) with adenosine, and 3.5 (0.4) with dipyridamole (p = 0.08 v papaverine and adenosine). CVRI was 0.22 (0.01) with papaverine, 0.21 (0.02) with adenosine, and 0.29 (0.03) with dipyridamole (p < 0.05 v papaverine, p = 0.09 v adenosine).
Conclusions:
These results indicate that measurement of coronary flow reserve and CVRI in patients with chest pain and normal coronary arteries depends on the pharmacological stimulus. Normal values were obtained with papaverine in all patients, irrespective of the exercise test response. In patients with a positive exercise test significantly lower values were obtained with dipyridamole than with papaverine, or adenosine. The reported impairment of coronary flow reserve in patients with angina and normal coronary arteries may reflect the variability in response to different pharmacological agents. The mechanism underlying this variability is unknown, but may involve an abnormality of adenosine metabolism in the myocardium.