Relation of tissue Doppler derived myocardial velocities to myocardial structure and beta-adrenergic receptor density in humans

OBJECTIVES We sought to evaluate the relation of segmental tissue Doppler ( TD) velocities to both the regional amount of interstitial fibrosis and the myocyte beta-adrenergic receptor density in humans. BACKGROUND The systolic myocardial velocity (Sm) and early diastolic myocar dial velocity (Em) acquired by TD are promising new indexes of left ventric ular function. However, their structural and functional correlates in human s are still unknown. METHODS Ten patients with coronary artery disease underwent echocardiograph ic examination including TD imaging, along with transmural endomyocardial b iopsy at the time of coronary bypass surgery (two biopsies per patient for a total of 20 specimens). The specimens were analyzed for percent interstit ial fibrosis and beta-adrenergic receptor density. RESULTS Normal segments (n = 8) had a higher beta-adrenoceptor density (2,2 80 +/- 738 vs. 1,373 +/- 460, p = 0.03) and a lower amount of interstitial fibrosis (13 +/- 3.3% vs. 28 +/- 11.5%, p = 0.002) than dysfunctional segme nts (n = 12). Myocardial systolic velocity and Em were also significantly h igher (9.5 +/- 2.7 vs. 5.9 +/- 1.8 cm/s, p = 0.025 and 11.3 +/- 2.8 vs. 6.4 +/- 2.1 cm/s, p = 0.002, respectively) in normal segments. A significant r elationship was present between Em and the beta-adrenergic receptor density (r = 0.78, p < 0.001) and percent interstitial fibrosis (r = -0.7, p = 0.0 026), which together accounted for 81% of the variance observed in Em. Like wise, a significant relationship was present between Sm and the beta-adrene rgic receptor density (r = 0.68, p < 0.001) and the percent interstitial fi brosis (r = -0.66, p = 0.004) and together accounted for 62% of the varianc e observed in Sm. CONCLUSIONS Systolic myocardial velocity and Em are strongly dependent on b oth the number of myocytes and the myocardial beta-adrenergic receptor dens ity. (C) 2000 by the American College of Cardiology.