1. Using Real-Time 3D Color Doppler Echocardiography: An in Vitro Study
ABSTRACT
Background: Shunt volume quantification is an important aspect of ventricular septal defect (VSD) evaluation. We tested feasibility of Real-Time 3D color Doppler echocardiography (RT3D-CDE) for determining the shunt volume of modeled VSDs of different shapes. Methods: VSDs were modeled by suturing latex balloons into the left and right ventricles (LV, RV) of 10 freshly harvested porcine hearts and the balloons were connected with tubing placed in perforations in the septum. Tubing was varied in area, number, and shape (circle, oval, crescent, triangle). A pulsatile pump was used to pump blood through the VSD (LV to RV) at stroke volumes of mL with a stroke rate of 60 bpm. We acquired RT3D-CDE images using a Siemens Acuson SC2000 ultrasound system. Results: Shunt volumes obtained using RT3D-CDE positively correlated with pumped stroke volumes (R² = 0.96) and a paired T-test showed no statistical difference (p = 0.82). Bland-Altman analysis showed low bias and limits of agreement (LOA) when comparing pumped and RT3D-CDE shunt volumes (Bias = -0.89, LOA = -5.4 to 5.2). Intra- and inter-observer analysis revealed excellent interclass correlation coefficients (0.989 and 0.988). Conclusions: RT3D-CDE is a feasible method for determining the shunt volume of VSDs even when their area, shape and number are varied.
CONCLUSION
The ability to accurately quantify VSD shunt volume during clinical evaluation is crucial for VSD management. This study was concerned with how RT3D-CDE would perform with non-circular and clustered VSDs. Shunt volumes obtained using RT3D-CDE positively correlated with pumped stroke volume, supporting that RT3D-CDE is a feasible method for quantifying VSD shunt volume despite variation in VSD shape or number. Although the circular sample plate did not always neatly fit over a non-circular shape, shunt volume values were still consistent with pumped stroke volume. The areas of the VSD not captured in the circular sample plate (corners of a triangle, edges of an oval or crescent) did not have enough flow going through them to significantly impact shunt volume quantification. It was possible to accurately measure the overall shunt volume of a cluster of three VSDs by placing one large sample plate over each of the three VSD.
Further lab-based and clinical-based research is needed to evaluate the feasibility of RT3D-CDE under different pathological conditions such as VSDs in different locations of the septum (membranous and perimembranous) and multiple non-clustered VSDs. The feasibility of RT3D-CDE to measure VSD shunt volume demonstrates the potential of this technology to evaluate hemodynamic conditions of congenital heart defects.
DISCLOSURES
No relationships to disclose:
David J. Sahn Evan Tracy Meihua Zhu
Kim Dang Joanne Tran Muhammad Ashraf
BACKGROUND
Ventricular septal defect (VSD) is the most common congenital heart disease, defined by a perforation in the ventricular septum allowing altered cardiac flow dynamics. Untreated VSDs can increase risk for potentially fatal diseases. VSD size and shunt flow are related to clinical outcomes and accurate evaluation is crucial for determining treatment options. Real-time 3D color Doppler echocardiography (RT3D-CDE) uses a matrix phased array transducer, which allows for instantaneous acquisition of color Doppler volumes. RT3D-CDE overcomes limitations of 2D-CDE and 3D-CDE by being free of angle dependency, geometric assumptions, and allowing for image acquisition without gating in real-time. The current RT3D-CDE program focuses on color flow through a circular sample plate, which may limit the quantification of shunt volume through non-circular or multiple clustered VSDs. The aim of this study is to evaluate the feasibility of the relatively new non-gated RT3D-CDE to determine the shunt volume of VSDs with varied shape and number.
METHODS
Ten VSD models were made using a phantom porcine heart models. VSDs were modeled by inserting a 12-inch latex balloon into each ventricle (atria and vessels removed). The balloons were connected by plastic tubing (Figure 1) of varied shape (circle, oval, crescent and triangle) area (0.38 cm²-4.4 cm²), and number (1 or 3). A perforation was made in the muscular septum and the balloons were passed through such that one balloon occupied each ventricle and the tube sat in the perforation. The necks of the balloons were attached to tubes connected to a pulsatile pump apparatus (Figure 2) with the inlet sutured at the left mitral annulus and the outlet sutured at the right tricuspid annulus. The VSD model was fixed in a water tank with the transducer facing the right ventricle. 2% cornstarch solution was used to fill the closed system in order to mimic blood viscosity. For each trial, the heart was passively pumped with Stroke Volumes ranging from mL (10 mL intervals) with 60 beats per minute. Flow traversed from the pump to the LV, through the VSD, to the RV and back to the pump. RT3D-CDE flow volumes were obtained using a 4Z1c transducer interfaced with a Siemens Acuson SC2000 ultrasound system. Siemens’ hemispheric 3D flow analysis package was used to analyze RT3D-CDE data.
Quantification of Shunt Volume Through Ventricular Septal Defects of Varied Area, Shape and Number
Using Real-Time 3D Color Doppler Echocardiography: An in Vitro Study
David J. Sahn, MD, MACC; Evan Tracy, BS; Kim Dang; Joanne Tran;
Meihua Zhu, MD, PhD; Muhammad Ashraf, MD
Oregon Health & Science University, Portland, OR, USA
RESULTS
Representative RT3D-CDE images are shown in Figure 4. RT3D-CDE images were able to exhibit adequate qualitative representation of true VSD shape. Linear regression analysis between RT3D-CDE derived VSD shunt volumes and pump stroke volume showed strong correlation (R² = 0.96)(Figure 3a). Bland-Altman analysis revealed a bias of and limits of agreement ranging from to 5.21 (Figure 3b). Linear Regression and Bland Altman analysis of inter- and intra-observer data yielded high R² values, low bias and LOA (Table 1). Interclass correlation coefficients (ICC) demonstrated excellent reproducibility of RT3D-CDE.
Figure 3: a) Linear regression of RT3D-CDE derived shunt volumes and pumped stroke volumes b) Bland-Altman analysis of RT3D-CDE derived shunt volumes and pump stroke volumes c, d) Bland Altman analysis of intra and inter-observer analysis, respectively.
Table 1: Summary of Interobserver and Intraobserver Variability and Reproducibility
Figure 2: Flow circuit diagram of VSD flow system created by the pulsatile pump. LV: Left Ventricle, RV: Right Ventricle. Arrows indicate direction of flow
Figure 4: RT3D-CDE flow analysis panels. Color flow signal going towards the transducer (red) positioned facing the right ventricle. a) Right en face view (without color), right en face view (with color and sample gate), and parasternal long axis view of a cluster of three VSDs b) Right en face view (with color) right en face view (with color and sample gate), and parasternal long axis view of a triangular VSD. a) b)
Figure 1: Tubing used to represent ventricular septal defects with 2DE and 3DE representations. 2DE and 3DE images were acquired using a GE Vivid E9 ultrasound system. These VSD models were used for the shunt volume trials in this study. c) d)
Figure 1 delete row 5