In Coronary Artery, Laminar Flow Preserves Stability and Resonance (Combined Vibrations from two Sources) Precipitates Acute Coronary Syndrome: Analysis of In-Vivo Coronary Flow from a Fluid Mechanics Perspective*

The cardiovascular system is conceptualized as a network of pump and pipes. Using a novel angiographic technique, coronary laminar or turbulent, antegrade or retrograde flows could be identified and recorded. Patients with unstable angina who presented to the cardiac catheterization laboratories were screened; those with moderate lesions on their angiograms were included. The aim was to investigate which flow patterns contributed to the stability, regression, or progression of these moderate lesions. A total of 53 patients were included. In 35 patients, the antegrade flow across the lesion was laminar, with no retrograde flow. These patients remained stable if their blood pressure and hyperlipidemia were well controlled. In contrast, the 18 patients whose lesions exhibited retrograde and turbulent flow became unstable and required interventions. Further investigation revealed that the retrograde flow behaved similarly to a pressure wave in the water hammer shock phenomenon. Due to repetitive contractions of the left ventricle during systole and dilation in diastole, axial vibrations occurred in the coronary blood column. When the coronary blood vibration frequency (in its retrograde direction) matched the natural frequency of coronary artery, resonance occured at the transition zone from diastole to systole, causing turbulent flow, rupturing the cap of coronary plaques. The images of these phenomena are strong evidences linking fluid mechanic event to acute coronary syndrome (or heart attack).