Use of mathematic modeling to compare and predict hemodynamic effects of the modified Blalock–Taussig and right ventricle–pulmonary artery shunts for hypoplastic left heart syndrome

Objective

Stage one reconstruction (Norwood operation) for hypoplastic left heart syndrome can be performed with either a modified Blalock–Taussig shunt or a right ventricle–pulmonary artery shunt. Both methods have certain inherent characteristics. It is postulated that mathematic modeling could help elucidate these differences.

Methods

Three-dimensional computer models of the Blalock–Taussig shunt and right ventricle–pulmonary artery shunt modifications of the Norwood operation were developed by using the finite volume method. Conduits of 3, 3.5, and 4 mm were used in the Blalock–Taussig shunt model, whereas conduits of 4, 5, and 6 mm were used in the right ventricle–pulmonary artery shunt model. The hydraulic nets (lumped resistances, compliances, inertances, and elastances) were identical in the 2 models. A multiscale approach was adopted to couple the 3-dimensional models with the circulation net. Computer simulations were compared with postoperative catheterization data.

Results

Good correlation was found between predicted and observed data. For the right ventricle–pulmonary artery shunt modification, there was higher aortic diastolic pressure, decreased pulmonary artery pressure, lower Qp/Qs ratio, and higher coronary perfusion pressure. Mathematic modeling predicted minimal regurgitant flow in the right ventricle–pulmonary artery shunt model, which correlated with postoperative Doppler measurements. The right ventricle–pulmonary artery shunt demonstrated lower stroke work and a higher mechanical efficiency (stroke work/total mechanical energy).

Conclusions

The close correlation between predicted and observed data supports the use of mathematic modeling in the design and assessment of surgical procedures. The potentially damaging effects of a systemic ventriculotomy in the right ventricle–pulmonary artery shunt modification of the Norwood operation have not been analyzed.

Abbreviations and Acronyms: AoA, ascending aorta, AoD, descending aorta, BTS, Blalock–Taussig shunt, CO, cardiac output, 3-D, 3-dimensional, HLHS, hypoplastic left heart syndrome, IA, innominate artery, LCA, left carotid artery, LSA, left subclavian artery, RVS, right ventricle–pulmonary artery shunt, SVR, systemic vascular resistance

CTSNet classification: 12, 21