It inhibits the enzyme adenosine deaminase which normally breaks down adenosine. This inhibition leads to increased levels of adenosine. Adenosine activates the enzyme adenylate cyclase which leads to increased cyclic AMP (cAMP) synthesis.
Dipyridamole also inhibits the enzyme phosphodiesterase which normally breaks down cAMP.

Both of these mechanisms lead to increased levels of cAMP within platelets. cAMP impairs platelet aggregation.

Modified release dipyridamole is used in conjunction with aspirin (Aggrenox®) in the secondary prevention of stroke and transient ischemic attack.

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Sensitivity, specificity, positive predictive value, and negative predictive value of the dipyridamole sestamibi stress test comparing arterial to vein
From CHEST, 10/1/04 by Albert J. DeLuca

Study objectives: To determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the dipyridamole stress test (DSST) in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native coronary artery disease (CAD) compared with saphenous vein graft obstruction [greater than or equal to] 50% in patients with prior coronary artery surgery and symptoms.

Design: In 144 patients with prior coronary artery surgery who underwent a DSST within 8 [+ or -] 7 days of coronary angiography performed because of cardiac symptoms, we investigated the sensitivity, specificity, PPV, and NPV of the DSST in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD (201 total arterial conduits) vs [greater than or equal to] 50% obstruction of saphenous vein grafts (total saphenous grafts = 246).

Setting: A university hospital.

Patients: The 144 patients included 88 men and 56 women, mean age 68 [+ or -] 9 years ([+ or -] SD).

Results: The DSST had a sensitivity of 81%, a specificity of 87%, a PPV of 84%, and a NPV of 84% in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD. The DSST had a sensitivity of 88%, a specificity of 82%, a PPV of 86%, and a NPV of 85% in predicting [greater than or equal to] 50% obstruction of saphenous vein grafts.

Conclusion: There was no significant difference in sensitivity, specificity, PPV, or NPV of the DSST in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD vs predicting [greater than or equal to] 50% obstruction of saphenous vein grafts in patients with prior coronary artery surgery and cardiac symptoms. (CHEST 2004; 126:1040-1041)

Key words: coronary artery disease; coronary artery surgery; dipyridamole sestamibi stress test; internal mammary artery; saphenous vein grafts

Abbreviations: CAD = coronary after, disease; DSST = dipyridamole sestamibi stress test: NPV = negative predictive value; PPV = positive predictive value

**********

The dipyridamole sestamibi stress test (DSST) is useful in detecting myocardial ischemia due to obstructive coronary artery disease (CAD). (1-3) However, to the best of our knowledge, there are no published data showing in patients with prior coronary artery surgery the sensitivity specificity, positive predictive value (PPV), and negative predictive value (NPV) of the DSST in diagnosing [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD (defined as [greater than or equal to] 50% obstruction in either a previously unbypassed coronary artery or distal to the insertion of a bypass graft) or in predicting saphenous vein graft obstruction [greater than or equal to] 50%. This article reports the sensitivity, specificity, PPV, and NPV of the DSST in diagnosing [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD vs saphenous vein graft obstruction [greater than or equal to] 50% in 144 patients with prior coronary artery, surgery who underwent coronary angiography because of cardiac symptoms. Therefore, the uniqueness of this article is the comparison of arterial to vein conduits.

MATERIALS AND METHODS

The 144 patients included 88 men and 56 women, mean age 68 [+ or -] 9 years ([+ or -] SD; range, 43 to 85 years), with prior coronary artery surgery who underwent a DSST within 8 [+ or -] 7 days of coronary angiography performed because of cardiac symptoms. One hundred four of the 144 patients (72%) were white. The DSST was performed as previously described. (4,5)

We investigated the sensitivity, specificity, PPV, and NPV of the DSST in predicting [greater than or equal to] 50% obstruction of an internal mammary artery (n = 121) or new native CAD (n = 80; 201 total arterial conduits) vs [greater than or equal to] 50% obstruction of saphenous vein grafts (total saphenous vein grafts = 246). New native CAD was defined as [greater than or equal to] 50% obstruction in either a previously unbypassed coronary artery or distal to the insertion site of a bypass graft. The three patients with both disease of the saphenous vein bypass graft and new native vessel disease were classified as having new native vessel disease. The quantification of lesions in the arteries or venous grafts was made visually. Student t tests were used to analyze continuous variables. [chi square] tests were used to analyze dichotomous variables.

RESULTS

Table 1 shows the sensitivity, specificity, PPV, and NPV of the DSST in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD vs saphenous vein obstruction [greater than or equal to] 50%. Table 1 also lists levels of statistical significance. There was no significant difference in sensitivity, specificity, PPV, or NPV if obstruction of arterial conduits was compared with distal arterial disease or venous graft disease.

DISCUSSION

The DSST is useful in detecting myocardial ischemia due to obstructive CAD. (1-3) However, to the best of our knowledge, there are no published data showing the sensitivity, specificity, PPV, and NPV of the DSST in predicting either [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD (defined as [greater than or equal to] 50% obstruction in either a previously unbypassed coronary artery or distal to the insertion site of a bypass graft) or in predicting saphenous vein graft obstruction [greater than or equal to] 50% in patients with prior coronary artery surgery and symptoins. The present study showed in 144 patients that the sensitivity, specificity, PPV, and NPV, respectively, of the DSST in predicting internal mammary artery obstruction or new native CAD vs saphenous vein graft obstruction were 81% vs 88%, 87% vs 82%, 84% vs 86%, and 84% vs 85%. Despite the physiologic differences in vasodilator properties of dipyridamole in arterial vs venous conduits, there was no significant difference in sensitivity, specificity, PPV, or NPV of the DSST in predicting [greater than or equal to] 50% obstruction of an internal mammary artery or new native CAD vs [greater than or equal to] 50% obstruction of saphenous vein grafts in patients with prior coronary artery surgery and cardiac symptoms. There was no significant difference in sensitivity, specificity, PPV, or NPV if obstruction of arterial conduits was compared with distal arterial disease or venous graft disease.

REFERENCES

(1) Candell-Riera J, Santana-Boado C, Castell-Conesa J, et al. Dipyridamole administration at the end of an insufficient exercise Tc-99m MIBI SPECT improves detection of multivessel coronary artery disease in patients with previous myocardial infarction. Am J Cardiol 2000; 85:532-535

(2) Smart SC, Bhatia A, Hellman R, et al. Dobutamine-atropine stress echocardiography and dipyridamole sestamibi scintigraphy for the detection of coronary artery disease: limitations and concordance. J Am Coil Cardiol 2000; 36:1265-1273

(3) Soman P, Taillefer R, DePuey EG, et al. Enhanced detection of reversible perfusion defects by Tc-99m sestamibi compared to Tc-99m tetrofosmin during vasodilatar stress SPECT imaging in mild-to-moderate coronary artery disease. J Am Coil Cardiol 2001; 37:458-462

(4) Belkin RN, Ghosh J, DeLuca AJ, et al. Comparison of two-dimensional echocardiographic tissue harmonic imaging and gated sestamibi singe-photon emission computed tomographic left ventricular ejection fraction measurements. Am J Cardiol 2003; 92:759-762

(5) Taillefer R. Ahlberg AW, Masood Y, et al. Acute [beta]-blockade reduces the extent and severity of myocardial perfusion defects with dipyridamole Tc-99m sestamibi SPECT imaging. J Am Coil Cardiol 2003; 42:1475-1483

* From the Department of Medicine, Cardiology Division, Westchester Medical Center/New York Medical College, Valhalla, NY.

Manuscript received February 4, 2004; revision accepted May 7, 2004.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e mail: permissions@chestnet.org).

Correspondence to: Wilbert S Arnnow, MD, Cardiology Division, New York Medical College, Macy Pavilion, Room 138, Valhalla, NY 10595; e-mail: WSAronow@aol.com

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