In-Vitro Effects of Cardioplegic Solutions on Human Saphenous Vein Endothelium - a Scanning Electron Microscopy Study

Summary

In order to evaluate the effects of potassium cristalloid cardioplegic Solutions (CPS) on the endothelial morphology, human saphenous veins were studied by scanning electron microscopy after exposure to three CPS namend MKP (magnesium-potassium-procaine cardioplegia), LK (low-potassium cardioplegia), and HKA (high-potassium-albumin cardioplegia) and to their main components.

Vein rings, selected from the saphenous veins sampled for graft harvesting in 63 patients undergoing aorto-coronary bypass surgery, were exposed for 30, 60, and 120 minutes to the following buffered Solutions: Krebs bicarbonate (as control); MKP cardioplegia; KCl (16.0 mmol/L); MgCl₂2 · 6H₂O (16.0 mmol/L); Procaine (0.05 mmol/L); NaCl (92.5 mmol/L); LK cardioplegia; KCl (10.0 mmol/L); Mannitol (74.3 mmol/L); Glucose (27.7 mmol/L); HKA cardioplegia; KCl (30 mmol/L).

Severe endothelial lesions, consisting of diffuse disendothelialization and diffuse signs of endothelial suffering, were induced by KCl (30 and 16 mmol/L) after 60-120 min, and by MKP cardioplegia and KCl (10 mmol/L) after 120 min. Moderate endothelial lesions, characterised by diffuse endothelial surface changes and focal cellular loss, were induced by KCl (30 and 16 mmol/L) after 30 min, MKP cardioplegia and KCl (10 mmol) 30-60 min, LK cardioplegia, HKA cardioplegia, and MgCl₂ · 6H₂O after 120 min. Slight endothelial lesions, consisting of diffuse endothelial bulging, or absence of significant endothelial changes, were found in samples otherwise treated.

Our findings showed a signiflcant damaging effect of CPS on the human saphenous vein endothelium in-vitro. The endothelial lesions seemed related to the presence of potassium and magnesium, and to Prolongation of the time of exposure to the cardioplegic Solutions. On the other hand, these lesions were significantly reduced in samples exposed to a low-potassium cardioplegia containing glucose and mannitol, and in samples exposed to a high-potassium cardioplegia containing albumin, glucose, and mannitol. The most signifleant alteration consisted in loss of endothelial cells accompanied by wide exposure of subendothelial connective tissue. This lesion may induce thrombogenic mechanisms and consequently it may favour graft occlusion.

Zusammenfassung

Den von 63 Patienten gewonnenen Saphena-Venen wurden 0,5 cm breite Segmente entnommen, auf die drei verschiedene kardioplegische Lösungen einwirkten. Es handelte sich dabei um eine Mg-KCl-Procain-Lösung, eine KCl-Lösung von geringer Konzentration und um eine hochkonzentrierte KCl-Albumin-Lösung. Außerdem wurden noch die Wirkungen folgender Substanzen isoliert geprüft: MgCl, Procain, NaCl, Manitol und Glukose. Die einzelnen Proben wurden elektronenmikroskopisch untersucht, wobei nach einer Einwirkungszeit der Lösungen von 30, 60 und 120 Minuten fehlende, leichte oder schwere Endothelveränderungen beobachtet wurden. Die Veränderungen waren von der Einwirkungsdauer und der Anwesenheit von Kalium und Magnesium abhängig; sie waren weniger ausgeprägt, wenn die Lösungen Albumin, Glukose und Mannitol enthielten.

Key words

Endothelium - Human saphenous vein - Graft - Cardioplegia - Scanning electron microscopy