Objective:To evaluate the effect of coronary microvascular dysfunction (CMD) on left atrial and ventricular function in patients with ischemia and non-obstructive coronary artery disease (INOCA) under the drug stress of regadenoson by speckle tracking imaging and left ventricular pressure-strain ring ultrasound technology.Methods:A total of 43 patients with INOCA who were admitted to the Department of Cardiology of the First Bethune Hospital of Jilin University from May 2022 to October 2023 were prospectively enrolled, and drug stress tests were performed. The coronary flow velocity reserve (CFVR) values were obtained by transthoracic Doppler echocardiography, and the INOCA patients with CFVR<2.0 were assigned to the CMD group ( n=24), and those with CFVR≥2.0 were assigned to the contrast group (CON group, n=19), and 20 healthy people without chest pain matched by clinical data were selected as the negative group (NEG group). The differences in general clinical data, routine echocardiography before and after stress, left atrial strain, and myocardial work parameters were compared between the groups. The correlation analysis of intra-group parameters was performed, and then the ROC curve was used to evaluate the diagnostic value of ultrasound parameters for INOCA. Results:Compared with the CON group and the NEG group, the ratio of early diastoic velocity E peak of mitral value orifice to the late diastoic velocity A peak(E/A) decreased and the ratio of early diastoic velocity E peak of mitral valve orifice to the early diastoic velocity e′ of the mitral valve annulus(E/e′) increased in the CMD group, and the differences were statistically signnificant (all P<0.05).There were statistically significant differences in left atrial strain parameters including left atrial strain reservoir (LASr), left atrial conduit strain (LAScd), left atrial contraction strain (LASct) between CON group and CMD group before and after stress (all P<0.05).However, there were no statistically significant differences between CON group and CMD group in myocardial work parameters including global longitudinal strain (GLS), peak strain dispersion (PSD), global work index (GWI), global constructive work (GCW), global wasted work (GWW), global work efficiency (GWE) at rest (all P>0.05), and there were significant differences only after stress (all P<0.05). E/e′ was negatively correlated with LASr and LAScd in the CMD group and CON group ( rs=-0.36, r=-0.31; all P<0.05), GLS was positively correlated with GWI, GCW, GWE( r=0.81, 0.61, 0.37; all P<0.05). GLS was positively correlated with GWI, GCW and GWE at stress state( r=0.66, 0.51, 0.52; all P<0.05), and negatively correlated with GWW ( rs=-0.39, P<0.05). PSD was positively correlated with GWW ( rs=0.30, P<0.05), and negatively correlated with GWI, GCW and GWE ( r=-0.46, -0.40, -0.38; all P<0.05). Univariate regression analysis showed that left atrial strain and myocardial work had good predictive values for CMD, and the predictive values of rest LASr and stress GLS were higher, with AUC values of 0.927 and 0.882, respectively. Conclusions:In patients with INOCA and CMD, the left atrial strain capacity decreases at both rest and stress state, and the myocardial work capacity decreases only under the stress. The changes in parameters of left atrial strain and myocardial work provide new ultrasound parameters and predictors for clinical evaluation of CMD.