The goal of this observational study is to compare the value of NTG-Pd/Pa and saline-Pd/Pa in participants with intermediate stenosis of the coronary artery. The main questions it aims to answer are:

The numerical difference between NTG-Pd/Pa and saline-Pd/Pa To compare the diagnostic performance of NTG-Pd/Pa and saline-Pd/Pa in predicting the binary result of FFR assessment?

Participants will undergo NTG-Pd/Pa, Saline-Pd/Pa, and FFR successively in the target vessel.

Fractional Flow Reserve (FFR) is the gold standard for determining the functional ischemia of coronary arteries with intermediate lesions. Both intracoronary nitroglycerine (NTG) administration and saline administration induce an acute drop in trans-lesional coronary pressure. Both pressure ratios correlate well with FFR values and can reliably predict positive results in FFR assessments. The aims of this study were

1. To evaluate the numerical difference between NTG-Pd/Pa and saline-Pd/Pa.
2. To test the repeatability of saline-Pd/Pa.
3. To compare the diagnostic performance of NTG-Pd/Pa and saline-Pd/Pa in predicting the binary result of FFR assessment.

Participants will be enrolled prospectively from National Taiwan University Hospital Hsinchu Hospital, Miaoli General Hospital, and Taichung Veterans General Hospital. The coronary artery with intermediate stenosis will undergo NTG-Pd/Pa, saline-Pd/Pa, and FFR assessments sequentially. Saline-Pd/Pa will be tested repeatedly during the assessment.

Inclusion Criteria:

• Participants with coronary artery with 50-90% stenosis.
• In participants who suffered from ST elevation myocardial infarction within 5 days, only the non-culprit vessel was eligible for coronary functional testing.

Exclusion Criteria:

• Systolic blood pressure is less than 90 mmHg for more than 5 minutes during examination.
• Resting heart rate is less than 50 beats per minute.
• Heart failure remains decompensated at the time of examination, such as inability to lie flat or cardiogenic shock.
• Acute onset of asthma or chronic obstructive pulmonary disease.

Participants referred for coronary angiography with intermediate lesions will be invited to join the registry. Enrollment sites include medical facilities in northern and central Taiwan.

Data cannot be shared publicly because of ethical restrictions. The restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are from the National Taiwan University Hospital Ethics Committee (contact via ntuhrec@ntuh.gov.tw) for researchers who meet the criteria for access to confidential data.