Quantitative Analysis of Left Ventricular Flow Dynamics in Latent Obstructive Hypertrophic Cardiomyopathy Using Vector Flow Mapping

Abstract

Objectives: This study aimed to assess left ventricular (LV) energy loss (EL), circulation and vortex area using vector flow mapping (VFM) in patients with latent obstructive hyper­trophic cardiomyopathy (LOHCM) and nonobstructive hypertrophic cardiomyopathy (NOHCM). Methods: Fourteen LOHCM patients, 10 NOHCM patients, and 11 healthy individuals were evaluated by transthoracic echocardiography. An offline VFM workstation was used to analyze the LV blood flow patterns and fluid dynamics. The hemodynamic parameters, EL, circulation, and vortex area in 7 cardiac phases were calculated and analyzed. Results: Compared with controls and NOHCM patients, EL was significantly higher in ­LOHCM patients during the rapid ejection phase, slow ejection (SE) phase, and isovolumetric relaxation phase (p < 0.05). LOHCM patients also showed increased circulation during SE compared to the other two groups (p < 0.05). The ability to discriminate between NOHCM and LOHCM was assessed by the area under the receiver-operating characteristic curve (AUC), and EL during SE was found to have the largest AUC (0.964); the best cutoff value was 6.34 J/m3/s, with a sensitivity of 100% and specificity of 80%. Conclusions: The VFM technique can detect abnormal changes of LV EL and vortex characteristics in hypertrophic cardiomyopathy patients. Compared with controls and NOHCM patients, the LOHCM patients have worse systolic and diastolic functions.

Energy loss by right ventricular pacing: Patients with versus without hypertrophic cardiomyopathy

“…The velocity vector of the LV intracavitary blood flow was computed by the software based on a system developed by Itatani et al 18 Based on the VFM images, the intraventricular EL, vortex area, and circulation were calculated 13,19 . The definitions of the vortex area and circulation were based on previous reports, 20‐22 that is, the vortex area was defined as the largest area of the physiological vortex measured during each cardiac cycle, and the circulation was calculated as the integral of the vorticity over an area. The circulation represented the quantity of flow swirling inside the vortex in the observed plane 21 .…”

Vector flow mapping: A review from theory to practice

“…Moreover, the LOHCM patients show also higher values of circulation during SE and IVR, which are consistent with systolic and diastolic dysfunction, since in normal subjects the flow is supposed to be laminar in these phases and, consequently, associated with lower circulation values. 41 Lastly, VFM has contributed to clarify the mechanisms underlying systolic anterior motion of the mitral valve (SAM): one is a vortex during the isovolumic phase, which incorporates mitral valve leaflets and causes mitral valve traction towards the inter-ventricular septum; the other is linked to the ejection flow, initially deflected posteriorly by the septal bulging and then redirected anteriorly, thus, pushing the mitral valve towards the inter-ventricular septum. 42…”