ObjectiveTo estimate the value of transthoracic coronary flow Doppler imaging to detect coronary flow reserve (CFR) changes in patient with obstructive sleep apnea syndrome (OSA). Methods Fifty patients with OSA who hospitalized or were outpatient in Aerospace 731 Hospital during the period of 2010 March to 2013 December were enrolled in this study and were divided into three groups according to apnea hypopnea index (AHI). Eighteen cases of patients which AHI was greater than 5 and less than 20 were defi ned as mild group, 16 cases of patients which AHI was more than 20 and less than 40 were defi ned as middle group, 16 cases of patients which AHI was greater than 40 were defi ned as severe group. The diastolic peak velocity (PDV) and meanfl ow velocity (MDV) of the distance segment of left anterior descending coronary (LAD) were measured by transthoracic echocardiography at rest and after intravenous infusion of adenosine triphosphate (ATP). Meanwhile, CFR was calculated. Forty healthy persons were chosen as control group. Thettest was used to compare the difference of PDV, MDV and CFR between OSA group and healthy controls. The single factor analysis of variance was used to compare the difference of PDV, MDV and CFR in patients with different AHI. SNK -q test was used to compare in different OSA groups. Thet test was used to compare the difference of PDV, MDV among OSA group, healthy control and OSA groups with different AHI at rest and after intravenous infusion of ATP.ResultsCoronaryfl ow velocity Doppler signals were successfully obtained in all the groups. PDV ([92.78±7.68] cm/s) and MDV ([85.93±6.98] cm/s) after intravenous infusion of ATP in control group were significant higher than those at rest ([28.09±4.55] cm/s and [21.76±5.09] cm/s) (t=49.687 and 58.259, bothP<0.001). PDV ([82.73±6.91] cm/s) and MDV ([77.39±6.73] cm/s) after intravenous infusion of ATP in OSA group were signifi cant higher than those at rest ([29.93±3.66] cm/s and [22.28±4.15] cm/s) (t=55.381 and 47.700, bothP<0.001). There was no statistically signifi cant difference between PDV and MDV at rest in OSA group and control group. The difference of PDV and MDV between OSA group and normal group was statistically signifi cant after intravenous infusion of ATP (t=6.524 and 5.884, bothP<0.01). There was no statistically signifi cant difference between OSA groups with different AHI at rest. There were statistically signifi cant difference between OSA groups with different AHI after intravenous infusion of ATP (5≤AHI<20:t=-32.903 and-32.771, both P=0.000; 20≤AHI<40:t=-37.122 and-32.623, bothP=0.000; AHI>40:t=-28.197 and-20.184, both P=0.000). PDV and MDV of patients with AHI>40 were less than those of patients with 5≤AHI <20 and 20≤AHI<40 and the differences were statistically signifi cant (PDV:q=21.048 and 15.667, bothP<0.05; MDV:q=12.958 and 18.182, bothP<0.05). However, the differences of PDV and MDV was not statistically signifi cant between patients with 5≤AHI<20 and patients with 20≤AHI<40.The CFRmax and CFRmean in OSA group were lower than those in control group (t=5.310 and 6.430, bothP=0.000). There were statistically signifi cant difference for CFRmax and CFRmean in patients with different AHI and the difference decreased with severity of OSA increased. The CFRmax and CFRmean in patients with 5≤AHI<20 were higher than those in patients with 20≤AHI<40 and AHI>40 (CFRmax:q=2.889 and 4.142, bothP<0.05; CFRmean:q=3.080 and 4.204, bothP<0.05). There was no statistical signifi cant difference for CFRmax and CFRmean between patients with 20≤AHI<40 and patients with AHI>40.ConclusionsIn patients with obstructive sleep apnea syndrome, transthoracic coronaryfl ow imaging combined with intravenous infusion of adenosine triphosphate shows impaired in CFR. It means the patients with OSA have a coronary artery microcirculation impairment in early stage. Assessing CFR in the patients with OSA is of important clinical value for the evaluation of treatment effective of medicine and surgery and follow-up.