Ex Vivo Comparison of the Elastic Properties of Vascular Substitutes Used for Pulmonary Artery Replacement

INTRODUCTION

Study aims were to evaluate the elastic properties of vascular substitutes frequently used for pulmonary artery (PA) replacement, and then to compare their compliance and stiffness indexes to those of human PA.

METHODS

A bench-test pulsatile flow experiment was developed to perfuse human cadaveric vascular substitutes (PA, thoracic aorta, human pericardial conduit), bovine pericardial conduit, and prosthetic vascular substitutes (polytetrafluorethylene and Dacron grafts) at a flow and low pulsed pressure mimicking pulmonary circulation. Intraluminal pressure was measured. An ultrasound system with an echo-tracking function was used to monitor vessel wall movements. The diameter, compliance, and stiffness index were calculated for each vascular substitute and compared to the human PA at mean pressures ranging from 10 to 50 mmHg.

RESULTS

The compliance of the PA and the thoracic aorta were similar at mean physiological pressures of 10 mmHg and 20 mmHg. The PA was significantly less compliant than the aorta at mean pressures above 30 mmHg (P = 0.017). However, there was no difference in stiffness index between the two substitutes over the entire pressure range. Compared to the PA, human pericardial conduit was less compliant at 10 mmHg (P = 0.033) and stiffer at 10 mmHg (P = 0.00038) and 20 mmHg (P = 0.026). Bovine pericardial conduit and synthetic prostheses were significantly less compliant and stiffer than the PA for mean pressures of 10, 20, and 30 mmHg. There were no differences at 40 and 50 mmHg.

CONCLUSIONS

Allogenic arterial grafts appear to be the most suitable vascular substitutes in terms of compliance and stiffness for PA replacement.

Wrist fracture in a 6-year-old girl after an accidental electric shock at low voltages

Bone injuries related to electric shocks are usually seen with high-voltage current exposure or with additional traumas, such as falls. Few cases of fractures after electric shocks at low-voltages (with no direct blunt trauma) are reported in the literature. They result from electrically-induced tetanic muscle contractions. Most of them involve the proximal appendicular skeleton, while distal fractures of limbs are uncommon. We report the case of a 6-year-old girl who suffered local superficial burns of the hand and a distal radius buckle-type fracture after sustaining a 230-V electric shock. The accident occurred while the girl was touching with the right hand the metallic stand of a non-insulated street lamp. She felt a sudden jolt and managed to pull her hand free quickly, without falling or losing consciousness. The superficial burns of the hand were consistent with Jellinek's electric marks, while the buckle fracture of the radius was consistent with a forceful contraction of the flexor muscles of the hand. Only four cases of radius fractures resulting from accidental electric shocks at low voltages have been previously reported in the literature. All of them involved pediatric patients, suggesting that a child's vulnerability to this kind of fracture may exist. The present case is the youngest one ever described.