A Portable Ex Vivo Heart Perfusion Apparatus for Cardiac CT Imaging: Visible Heart® Mobile

Medical device developers can often be limited in pre-clinical experimental testing of new products because of procedural complexities and safety concerns to the animal or patient. Though animal or human cadavers can be used for these types of studies thereby eliminating the need for safety precautions, the functional capabilities of the tissue can be lost. As a novel way to provide such functional device/tissue assessment, the Visible Heart® (VH®) Laboratory has developed reanimation methodologies1 that allow the four chambers of the heart to contract naturally ex vivo. Swine hearts are routinely reanimated using this methodology with a clear perfusate which allows for direct endoscopic visualization of functional cardiac anatomy and importantly the device/tissue interface. For the past two decades, these capabilities have been useful for testing early device prototypes and developing educational and procedural videos. More specifically, this approach provides the added convenience of manipulating catheters into the ex vivo prep and visually studying their behavior for validation experiments of new medical devices. Further, multimodal imaging comparative assessments using both 4D echocardiography and fluoroscopy have been routinely performed. Yet, as imaging modalities continue to develop and are utilized for device placements or post-procedure evaluations, we hope to expand VH® capabilities.

Improved cardiac protection with Sabax cardioplegia in Langendorff isolated rat hearts

Objective: Cardioplegia is an important step to facilitate cardiac surgery while limiting intraoperative myocardial injury. Although recent advances in cardioplegic arrest methods have significantly contributed to better postoperative outcomes, there is still controversy regarding the optimal composition and temperature of the cardioplegic solution. Accordingly, we aimed to assess whether cold or lukewarm Sabax cardioplegia offer improved myocardial protection compared with the classical Krebs-Henseleit solution. Methods: The hearts of 40 male Wistar rats were isolated and submitted to constant-flow retrograde perfusion using a Langendorff perfusion apparatus. The hearts were randomly assigned to cold Krebs-Henseleit (K-H), cold Sabax, or lukewarm Sabax cardioplegia. The ECG, heart rates, and left ventricular systolic pressures (LVSP) were recorded pre- and post-cardioplegia. The time needed for cardioplegia induction and post-cardioplegia recovery were also noted. Results: Both cold and lukewarm Sabax cardioplegia insured faster induction and faster recovery following isothermic reperfusion compared to the standard K-H solution (both p< 0.01). With K-H cardioplegia, the hearts presented a 21.7% force loss after reperfusion (p< 0.001), whilst Sabax cardioplegia was associated with a slight increase in ventricular mechanical activity (3% LVSP increase with lukewarm Sabax cardioplegia, p< 0.001 and 2% LVSP increase with cold Sabax cardioplegia, p = 0.02). With Sabax cardioplegia the hearts displayed considerably less major arrhythmic events and presented less significant bradycardia. Conclusions: The present data suggest that Sabax cardioplegia may be superior to the classical cold crystalloid K-H solution in preserving mechanical activity of the heart and may provide superior protection against major arrhythmias.

Acute high blood glucose level attenuates histamine-stimulated acid secretion in male Wistar rats

Studies have shown that the hyperglycemic state induced by intravenous glucagon or glucose infusion may lead to inhibition of gastric acid secretion through the inhibition of gastric vagus activity. Histamine is a well-known mammalian acid secretagogue and it stimulates acid secretion through HMale Wistar rats weighing between 200 and 250 g were divided into three groups that received an intravenous infusion of normal saline (control group), glucose (hyperglycemic group), or insulin (hypoglycemic group) followed by injection of histamine to stimulate acid secretion. The oesophageal and duodenal ends of the rats’ stomach were cannulated with polythene tubing and the stomach was perfused at room temperature using a Langendoff perfusion apparatus. The effluent was collected in aliquots over 10 min per sample and its pH was measured.There was a significant (p<0.05) decrease in acid secretion following histamine injection in the hyperglycemic rats, while histamine injection led to an increase (p<0.05) in acid secretion in the hypoglycemic rats.These results show that hyperglycemic state would result in attenuated histamine-stimulated gastric acid secretion, while hypoglycemic state would lead to increased histamine-stimulated gastric acid secretion.