Within four weeks after PCI, all enrolled patients will undergo a comprehensive non-invasive coronary functional evaluation using transthoracic Doppler echocardiography (TTDE). After a 10-minute resting period, a complete baseline echocardiographic examination will be performed, including assessment of global and regional left ventricular wall motion. The mid-distal left anterior descending coronary artery (LAD) will then be identified by color Doppler imaging, and peak diastolic coronary blood flow velocity (CBFV) will be measured using pulsed-wave Doppler.
Coronary vascular function will subsequently be assessed using three sequential coronary functional tests performed under continuous 12-lead electrocardiographic monitoring, intermittent blood pressure measurements, and peripheral oxygen saturation monitoring, with a 15-minute recovery interval between tests.
The hyperventilation test will be performed by asking participants to breathe deeply and rapidly at a rate of approximately 30 breaths per minute for 5 minutes. The cold pressor test will consist of immersion of the participant's right hand in ice water for 2 minutes. Finally, dipyridamole will be administered intravenously at a dose of 0.84 mg/kg over 6 minutes to assess endothelium-independent coronary vasodilator capacity.
Coronary blood flow velocity will be measured at baseline and at the peak of each functional test. The ratio between peak and baseline CBFV will be calculated for each stimulus as an index of coronary vascular function. Symptoms, electrocardiographic changes, and inducible regional wall motion abnormalities will also be recorded throughout the examination. Patients receiving beta-blockers or calcium channel blockers will be asked to temporarily discontinue these medications for 48 hours before the study examination.
The primary endpoint is the comparison of coronary flow reserve measured during dipyridamole stress between the LAD and non-LAD groups.
Secondary analyses will evaluate the association between abnormal coronary functional responses and adverse clinical outcomes. Participants will undergo structured clinical follow-up six months after PCI through telephone contact. Information regarding recurrent angina, repeat coronary angiography, target lesion revascularization, myocardial infarction, cardiovascular death, or other cardiovascular events will be collected. Reported events will be verified through review of electronic medical records or hospital documentation whenever available.
The study is powered to detect clinically meaningful differences in coronary flow reserve between the two study groups. Statistical analyses will compare coronary functional parameters between groups using appropriate parametric or non-parametric methods according to data distribution. Multivariable generalized linear models will be used to account for potential confounding variables, while Cox proportional hazards regression analyses will evaluate the relationship between coronary functional abnormalities and six-month clinical outcomes after adjustment for relevant clinical characteristics.
