Mechanism of inducible regional dysfunction during dipyridamole stress

Jian Ping Bin, Elizabeth Le, Robert A. Pelberg, Matthew P. Coggins, Kevin Wei, Sanjiv Kaul

    Research output: Contribution to journalArticle

    33 Scopus citations

    Abstract

    Background - We hypothesized that increased myocardial oxygen demand resulting from hypotension and reflex tachycardia unmasking a reduced endocardial myocardial blood flow (MBF) reserve is the mechanism of dipyridamole-induced regional dysfunction in chronic coronary artery disease. Methods and Results - Ameroid constrictors were placed around the proximal coronary arteries and their major branches in 15 dogs to create chronic coronary stenosis. Seven days later, radiolabeled microsphere-derived MBF and 2-dimensional echocardiography-derived percent wall thickening (%WT) were measured at rest and after 0.56 mg/kg dipyridamole. Dipyridamole caused an increase (mean, 21%) in the rate-pressure product secondary to reflex tachycardia resulting from mild systemic hypotension. %WT in myocardial segments with an endocardial MBF reserve (dipyridamole/resting MBF) of 1.5 to 2.5 (n=35) did not change after dipyridamole, whereas it decreased in segments with an endocardial MBF reserve of <1.5 (n=30) and increased in those with an endocardial MBF reserve of ≥2.5 (n=45) (P<0.05). Most (80%) segments with endocardial MBF reserve of <1.5 and 14% with an endocardial MBF reserve of 1.5 to 2.5 showed inducible dysfunction after dipyridamole, whereas none of the segments with an endocardial MBF reserve of ≥2.5 showed this finding. A sigmoid relation (y=-6.74/[1+exp (19.9 · [x-1.84])]+1.35 · x, r=0.93, P<0.0001) was noted between endocardial MBF reserve and Δ%WT. In contrast, neither the epicardial MBF reserve nor the endocardial/epicardial MBF ratio during hyperemia was associated with inducible regional dysfunction. Conclusions - Increased myocardial oxygen demand resulting from hypotension and reflex tachycardia unmasking a reduced endocardial MBF reserve is the primary mechanism of dipyridamole-induced regional dysfunction in chronic coronary artery disease.

    Original languageEnglish (US)
    Pages (from-to)112-117
    Number of pages6
    JournalCirculation
    Volume106
    Issue number1
    DOIs
    StatePublished - Jul 1 2002

    Keywords

    • Blood flow
    • Myocardium
    • Stress
    • Tachycardia

    ASJC Scopus subject areas

    • Cardiology and Cardiovascular Medicine
    • Physiology (medical)

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