Asymmetry of flow in aortic root and its application in hypertrophic obstructive cardiomyopathy

The aortic root (AR) performs sophisticated functions regulating the blood dynamics during the cardiac cycle. Such complex function depends on the nature of flow in the AR. Here, we investigate the potential of new quantitative parameters of flow asymmetry that could have clinical implications. We developed a MATLAB program to study the AR hemodynamics in each sinus of Valsalva using two-dimensional (2-D) cardiac magnetic resonance imaging during systole and particularly at peak systolic flow in 13 healthy volunteers and compared with 10 patients with hypertrophic obstructive cardiomyopathy (HOCM). We show that the effective area of the aortic jet in healthy volunteers is significantly higher at peak systolic flow and on average during systole. The flow asymmetry index, indicating how the jet is skewed away from the left coronary sinus (LCS), is small in healthy volunteers and much larger in HOCM at peak systole. The average of this index over systole is significantly more different between cohorts. Looking in more detail at the flow in the sinuses during systole, we show that the AR jet in healthy volunteers is more symmetrical, affecting the three sinuses almost equally, unlike the asymmetric AR jet in patients with HOCM that has decreased flow rate in the LCS and increased fractional area of backward flow in the LCS. The percentage of backward flow in the sinuses of Valsalva calculated over systole is a potential indicator of perturbed AR hemodynamics and the distribution of vortical flow and could be used as a measure of flow asymmetry. NEW & NOTEWORTHY The aortic root is a vital organ responsible for performing sophisticated functions to regulate the blood flow dynamics during the cardiac cycle. Such synchronized complex performance affects and is affected by the flow symmetry and type of flow reaching the aorta. Here, we report flow asymmetry in the aortic root which could have clinical implications, and we investigate the potential of various quantitative parameters as measures of flow asymmetry in hypertrophic obstructive cardiomyopathy.