The role of aortic compliance in determination of coarctation severity: Lumped parameter modeling, in vitro study and clinical evaluation

Abstract

Early detection and accurate estimation of the extent of coarctation of the aorta (COA) is critical to long-term outcome. Peak-to-peak trans-coarctation pressure gradient (PKdP) higher than 20 mmHg is an indication for interventional/surgical repair. Patients with COA have reduced proximal and distal aortic compliances. A comprehensive study investigating the effects of variations of proximal COA and systemic compliances on PKdP, and consequently on the COA severity evaluation has never been done. This study evaluates the effect of aortic compliance on diagnostic accuracy of PKdP. Lumped parameter modeling and in vitro experiments were performed for COA severities of 50%, 75% and 90% by area. Modeling and in vitro results were validated against retrospective clinical data of PKdP, measured in fifty-four patients with COA. Modeling and in vitro. PKdP increases with reduced proximal COA compliance (+36%, +38% and +53% for COA severities of 50%, 75% and 90%, respectively; p<0.05), but decreases with reduced systemic compliance (−62%, −41% and −36% for COA severities of 50%, 75% and 90%, respectively; p<0.01). Clinical study. PKdP has a modest correlation with COA severity (R=0.29). The main determinants of PKdP are COA severity, stroke volume index and systemic compliance. Systemic compliance was found to be as influential as COA severity in PKdP determination (R=0.30 vs. R=0.34). In conclusion, PKdP is highly influenced by both stroke volume index and arterial compliance. Low values of PKdP cannot be used to exclude the severe COA presence since COA severity may be masked by reduced systemic compliance and/or low flow conditions.

Elimination of Transcoarctation Pressure Gradients Has No Impact on Left Ventricular Function or Aortic Shear Stress After Intervention in Patients With Mild Coarctation

“…However, pressure gradients should be used with caution in patients with COA as we demonstrate that: 1) P K dP fails to reflect the effects of the COA (pre intervention) and transcatheter intervention on the LV and aorta hemodyanmics; 2) catheter and echocardiography pressure gradients are highly influenced by the flow rate. They are reduced when the flow rate is decreased (7,38); 3) P K dP is significantly influenced by arterial compliance. P K dP increases with reduced proximal COA compliance but decreases with reduced systemic compliance (7).…”

“…They are reduced when the flow rate is decreased (7,38); 3) P K dP is significantly influenced by arterial compliance. P K dP increases with reduced proximal COA compliance but decreases with reduced systemic compliance (7). …”

“…Vascular hemodynamic parameters : the systemic arterial compliance (SAC) and the systemic vascular resistance (SVR) (7,17); $$\mathit{SAC}={SV}_i/PP$$ $$\mathit{SVR}=80\mathit{MAP}/CO$$…”

“…Importantly, individuals with repaired coarctation without significant anatomic evidence for narrowing may demonstrate a gradient with exertion secondary to a lack of compliance at the anastomotic site as flow to the descending aorta increases with leg exercises (6,7). …”

Predicting blood pressure in aortas treated for coarctation

“…coa is a disease characterised by a narrowed region of the aorta, and accounts for 5-8% of congenital heart defects, or between three and four in every 10 000 live births [3,4]. It is considered a serious disease with a mean age of mortality of 35 years [5].…”