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In the left ventricle (LV), blood flow in a healthy biventricular human heart forms an energetically efficient vortex, which facilitates inflow into the ventricle, minimizes the dissipation of energy, preserves momentum, and redirects the flow toward the LV outflow.
In a healthy human right ventricle (RV), the blood flow path from inflow to outflow follows a gradual curvature through the basal and midventricular parts of the chamber, reflecting the regional anatomy of RV, compared with the more acute bend in the mid-to-apical ventricle observed in the LV.
The blood flow patterns with SRV and SLV are unknown.
We analyzed the intraventricular vortex in patients with univentricular hearts using vector flow mapping software (Hitachi Aloka Medical, Tokyo, Japan) to compare the energetic efficiency (intraventricular energy loss, kinetic energy of outflow, mean vorticity during diastole) of SRV to that of SLV.
Two dimensional color Doppler cineloop images obtained in the midesophageal LV long-axis view by transesophageal echocardiography were stored, and the images were analyzed using vector flow mapping software. SRV is defined as a single dominant morphologic RV with a rudimentary LV, and SLV is defined as a single dominant morphologic LV with a rudimentary RV. This prospective observational study was approved by the institutional ethics committee of Kyoto Prefectural University of Medicine (ERB-C-437-1), and written informed consent was obtained from all patients and their parents.
Five patients with SRV and five patients with SLV were enrolled. In the patients with SRV, the main diagnoses were hypoplastic left heart syndrome with aortic atresia (two patients), pulmonary atresia with dextrocardia (one patient), transposition of the great arteries with dextrocardia (one patient), and pulmonary atresia with patent ductus arteriosus (one patient). In patients with SLV, the main diagnoses were tricuspid atresia with ventricular septal defect (two patients), total anomalous pulmonary venous return with atrial septal defect (one patient), interruption of the aortic arch (one patient), and tricuspid stenosis with ventricular septal defect (one patient). An intraventricular vortex was created during diastole in all patients (Fig 1, left panel). There was no significant difference between the SRV group and the SLV group in intraventricular energy loss (24.8 [22.1-30.2] mW/m, 37.6 [27.2-38.6] mW/m, p = 0.09) (Fig 1, right panel). Kinetic energy of the SRV group was significantly lower than that of the SLV group (16.3 [9.2-17.5] mW/m, 75.8 [74.9-142.5] mW/m, p < 0.05). Vorticity during diastole of the SRV group was significantly lower than that of the SLV group (228.4 [196.9-282.5] /s, 332.2 [330.6-530.8] /s, p < 0.05).
Fig 1Vector flow mapping and energy loss images of SRV and SLV. SLV, single left ventricle; SRV, single right ventricle; EL, energy loss; VFM, vector flow mapping.
A diastolic vortex was observed in both SRV and SLV patients. However, the kinetic energy and vorticity were lower in the SRV compared with the SLV. These results suggested that the vortex in the SRV is not as efficient as the vortex in the SLV. This relative energetic inefficiency may make it more challenging for the SRV to support systemic circulation. Furthermore, analysis of the intraoperative energetic parameters may be helpful for anesthetic management of a patient with a univentricular heart.
Conflicts of Interest
Keiichi Itatani is an endowed chair of Kyoto Prefectural University of Medicine financially supported by Medtronic Japan and has a stock option of Cardio Flow Design. Other authors have no interest declared.
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