Innovative balloon-inflatable venous cannula for enhanced cardiopulmonary bypass in minimally invasive cardiac surgery

Abstract

Objectives: Minimally invasive cardiac surgery (MICS) struggles with effective caval isolation and cannulation for cardiopulmonary bypass (CPB). We aimed to develop a novel MICS venous cannula, eliminating external manipulations. The goal of this study is to thoroughly evaluate both the safety and the efficacy of a newly developed venous cannula.

Methods: The study presents the Aulus venous cannula for MICS, designed with internal balloons to block caval blood flow. Preclinical bench tests with a cardiac biosimulator and large animal studies per ISO10993-2016, evaluated performance and safety.

Results: The heparin-coated Aulus cannula had a post-sterilization comparable density of ∼0.200 μg/cm2. In ex vivo tests, using porcine heart models, the cannula enabled full caval occlusion, with endoscopic views confirming precise positioning. The pressure drop remained below the haemolytic threshold of 100 mmHg, indicated lower values compared to BioMedicus. A non-Good Laboratory Practice (GLP) large animal study included eight ovine models, divided into short- and long-term follow-up groups. Clinical pathology values were consistent CPB procedures, and histopathology indicated favourable tolerance despite short-term vessel injuries and long-term stenosis with fibrosis.

Conclusions: The Aulus cannula showed effective anticoagulant activity, strong integrity, and good tolerance in vitro and in vivo, highlighting its clinical potential.

Keywords: aulus; cannula; cardiopulmonary bypass; minimally invasive cardiac surgery; open heart surgery.

Graphical abstract

Figure 1:

Device design and concept. (A) Novel Aulus venous cannula features inflatable balloons; (B) conventional venous cannulation technique; (C) guidewire-assisted insertion via the femoral vein; (D) positioned in the SVC/IVC with balloon inflation; (E) use of the Aulus cannula for MICS; (F) use of the Aulus cannula for open heart surgery

Figure 2:

In vitro bench tests. (A) A schematic diagram and test setup were used to assess pressure drop in the Aulus cannula; (B) ViViTest system was used to acquire data

Figure 3:

Heparin coating studies showing the PTT time in the study groups. Here: Blank control is PPP; Negative control is a HDPE; Positive control is glass; uncoated customer sample is the test article, Medtronic tube is the control article and coated customer tube is the heparin coated text article

Figure 4:

Ex vivo and balloon expansion tests. (A) Ex vivo set up and experiments; (B) the cannula tested in an explanted porcine heart; (C) balloon expansion test showing the inflatable balloons; (D) pressure drop test showing the material reaches a maximum diameter of 41.25 mm with 70 ml liquid

Figure 5:

H&E-stained samples showing. (A) SVC with locally extensive, minimal to mild thrombosis, (B) IVC with multifocal, minimal intimal hyperplasia, (C) iliac vein with multifocal to diffuse degenerative changes of the media, (D) RA with minimal to mild endocardial hyperplasia with no thrombosis