Impact of differential right‐to‐left shunting on systemic perfusion in pulmonary arterial hypertension

Abstract

Objectives This study aimed at identifying the ideal right-to-left shunt-fraction to improve cardiac output (CO) and systemic perfusion in pulmonary arterial hypertension (PHT). Background Atrial septostomy has been a high-risk therapeutical option for symptomatic drug-refractory patients with PHT. Results have been unpredictable due to limited knowledge of the optimal shunt-quantity. Methods In 9 dogs, an 8-mm shunt-prosthesis was inserted between the superior vena cava (SVC) and the left atrium. With pulmonary artery banding, mean (±SEM) systolic right ventricular pressure increased from 37±1 mmHg at baseline to 44±1 mmHg (moderate PHT, P=0.005) and 50±2 mmHg (severe PHT, P<0.001). Shunt-flow was adjusted by total (forcing all flow through the shunt) or partial occlusion of the SVC and partial or total clamping of the shunt. Caval-, shunt- and aortic-flow were measured by ultrasonic flow-probes. Blood gases were drawn from the aortic root and pulmonary artery. Results At severe PHT, a shunt-flow of 11±1% of CO (253±90 mL/min) increased CO significantly by 25% (1.8±0.1 to 2.4±0.2 L/min, P=0.005) causing an increase of systemic oxygen delivery index (DO2I) by 23% (309±23 to 399±32 mL/min/M2, P=0.035). Arterial O2-saturation did not change significantly until a shunt-flow of 18±2% was exceeded, causing a drop from 96±1% to 84±4% (P=0.013). At moderate PHT, CO or DO2I did not improve significantly at any shunt-flow. Conclusions In severe PHT, a shunt-flow of 11% of CO represented the ideal shunt-fraction. Augmentation of CO compensated for declined O2-saturation due to right-to-left shunting and improved DO2I. In moderate PHT, atrial septostomy is less promising.

Study of the effect of Occlutech Atrial Flow Regulator on symptoms, hemodynamics, and echocardiographic parameters in advanced pulmonary arterial hypertension

“…29,30 Ideal shunt fraction should be titrated to patient size and hemodynamics, like the one provided by AFR. 13…”

“…12 An interatrial shunt fraction of 10–15% of cardiac output improves cardiac index and tissue oxygen delivery in severe PAH. 13 AFRs (Occlutech, Istanbul, Turkey) are new devices that provide different atrial septal fenestration diameters, titrated to the hemodynamic needs and size of the patient. 14 Animal studies show minimal inflammation, non-thrombogenicity, and retained patency.…”

Pediatric Perioperative Pulmonary Arterial Hypertension: A Case-Based Primer

“…It is sometimes said in this scenario “it is better to be blue than gray” because the patient without an atrial septal defect is not able to effectively pump their blood out to the lungs to get oxygenated and is in a low cardiac output state (“gray”). Patients who have the ability to “pop-off” from the high-pressure right side to the left side, are able to maintain their cardiac output at the expense of being more cyanotic [ 8 , 9 ]. The presence or absence of an intracardiac shunt lesion is thus an important part of the preoperative assessment.…”

Balloon Dilation Atrial Septostomy and Potts Anastomosis for Severe Pulmonary Arterial Hypertension: Why, When, and How

“…Based on recent experimental data, it would appear that increasing cardiac output no more than 15% to 20% from baseline would provide the greatest benefits and results. [45][46][47] Although atrial septostomy improves hemodynamic variables that correlate with clinical improvement and survival, true impact of septostomy on survival of patients with PAH is difficult to assess due to lack of controlled long-term studies (something that is also true for most of the current pharmacological options). However, the survival rates for patients with long-term follow-up in different case series appear to be better when compared with either historical controls or predicted survival.…”