Author + information
- Thach Nguyen1,2,
- Thao Dang2,
- Tu NT. Nguyen2,
- Le Dieu Anh2,
- Le Nhan Tam2,
- Tarneem Darwish3 and
- Gianluca Rigatelli4
The coronary arteries supply blood by giving out branches, penetrating the myocardium and forming the subendocardial plexuses. During diastole, the left ventricle (LV) relaxes, creating negative pressure in the sub-epicardial and subendocardial arterial plexuses As a result, the coronary blood flows forwards. During systole, the LV contracts and compresses these plexuses. The epicardial flow stops. The contracting force is greatest in the subendocardial layers where it approximates the intraventricular pressure. How to measure the intensity of the negative pressure in the sub-epicardial layer, before and after percutaneous coronary interventions (PCI)? Which imaging technique can we use as surrogates reflecting the flow across the subendocardial layer? What was the transit time through the subendocardial layers before and after PCI?
Angiograms with PCI were selected. The left coronary arteries were recorded in the right anterior oblique caudal or antero-posterior cranial view at 15 frames per second. The right coronary artery was recorded in the left anterior oblique view. The angiograms were reviewed frame by frame searching antegrade flow versus slow diffusion of contrast into the surrounding myocardium. The length in time of a strong antegrade flow reflected the intensity of a negative pressure generated by the relaxation of the LV at the subepicardial level. The length in time for the contrast to dissipate totally into the surrounding myocardium reflects the transit time through the subendocardial layer, Both time frames were recorded before and after PCI.
The results from 50 coronary angiograms showed two phases of coronary flow. In the first phase, the blood flowed from the ostium to the mid segment of the 3 epicardial arteries lasting 0.18-0.24 sec. After that, there was no strong organized antegrade flow. The blood just dissipated slowly into the surrounding myocardium. This phase 2 lasted an average of 1.3sec. The length of phase 2 before PCI was (1.7sec) longer than after PCI (1.3sec with p<0.05).
This is the first time, the strength of negative pressure in the subepicardial layer could be imaged and calculated even there was no significant change before and after PCI. However, after PCI, the transit time for blood across the subendocardial layer was shorter, suggesting better.