Relation of ^99mTc-sestamibi washout with myocardial properties in patients with hypertrophic cardiomyopathy

Background. We sought to determine the relationship between ^99mTc-sestamibi washout and myocardial properties in hypertrophic cardiomyopathy (HCM) patients. Methods and Results. Twenty-four HCM patients underwent biventricular cardiac cathe- terization, with a micromanometer-tipped catheter, both at rest and during atrial pacing, echocardiography and myocardial ^99mTc-sestamibi scintigraphy at rest. The ^99mTc-sestamibi washout rate (WR) was calculated using initial and delayed planar images. The HCM patients were divided into two groups as follows: Group A consisted of 13 patients showing ^99mTc-sestamibi WR < 22.5%; group B of 11 patients showing ^99mTc-sestamibi WR ≥ 22.5%. Significant correlations were observed between ^99mTc-sestamibi WR and percentage changes in pressure half-time (T_1/2), as well as those in the maximum first derivative LV pressure (LV dP/dt_max)(r = .43, P = .033; r =-.63, P = .001). The percentage changes in LV dP/dt_max and those in T_1/2 were significantly more reduced in group B than in group A (P < .05). The biphasic force-frequency relation was more frequently observed in group B than in group A (82% vs. 18%). Conclusion. Increased ^99mTc-sestamibi washout is associated with an impaired contractile reserve and prolonged relaxation, suggesting that myocardial ^99mTc-sestamibi scintigraphy may be useful in noninvasively detecting the early impairment of myocardial function in HCM patients.