Normothermic Ex Situ Heart Perfusion in Working Mode: Assessment of Cardiac Function and Metabolism

Summary

Normothermic ex situ heart perfusion (ESHP), preserves the heart in a beating, semi-physiologic state. When performed in a working mode, ESHP provides the opportunity to perform sophisticated assessments of donor heart function and organ viability. Here, we describe our method for myocardial performance evaluation during ESHP.

Abstract

The current standard method for organ preservation (cold storage, CS), exposes the heart to a period of cold ischemia that limits the safe preservation time and increases the risk of adverse post-transplantation outcomes. Moreover, the static nature of CS does not allow for organ evaluation or intervention during the preservation interval. Normothermic ex situ heart perfusion (ESHP) is a novel method for preservation of the donated heart that minimizes cold ischemia by providing oxygenated, nutrient-rich perfusate to the heart. ESHP has been shown to be non-inferior to CS in the preservation of standard-criteria donor hearts and has also facilitated the clinical transplantation of the hearts donated after the circulatory determination of death. Currently, the only available clinical ESHP device perfuses the heart in an unloaded, non-working state, limiting assessments of myocardial performance. Conversely, ESHP in working mode provides the opportunity for comprehensive evaluation of cardiac performance by assessment of functional and metabolic parameters under physiologic conditions. Moreover, earlier experimental studies have suggested that ESHP in working mode may result in improved functional preservation. Here, we describe the protocol for ex situ perfusion of the heart in a large mammal (porcine) model, which is reproducible for different animal models and heart sizes. The software program in this ESHP apparatus allows for real-time and automated control of the pump speed to maintain desired aortic and left atrial pressure and evaluates a variety of functional and electrophysiological parameters with minimal need for supervision/manipulation.

Introduction

Clinical relevance

While most aspects of cardiac transplantation have evolved significantly since the first heart transplant in 1967, cold storage (CS) remains the standard for donor heart preservation¹. CS exposes the organ to a period of cold ischemia that limits the safe preservation interval (4–6 hours) and increases the risk of primary graft dysfunction^2,3,4. Due to the static nature of CS, assessments of function or therapeutic interventions are not possible in the time between the organ procurement and transplantat....

Protocol

All the procedures in this manuscript were performed in compliance with the guidelines of the Canadian Council on Animal Care and the guide for the care and use of laboratory animals. The protocols were approved by the institutional animal care committee of the University of Alberta. This protocol has been applied in female juvenile Yorkshire pigs between 35–50 kg. All individuals involved in ESHP procedures had received proper biosafety training.

1. Pre-surgical Preparations

1. Place the organ chamber properly on the apparatus cart and install the silicon support membrane inside the organ chamber. The Ao, pulmonary artery (P....

Results

At the start of the perfusion (in non-working mode), the heart will normally resume a sinus rhythm when the temperature of the system and perfusate approaches normothermia. When entering working mode, as the LA pressures are approaching the desired values, ejection on the Ao pressure tracing should be observed and the LA flow (a reflection of cardiac output) should increase gradually. In a Yorkshire pig model (35–50 kg) and a starting heart weight of 180–220 grams, the initial.......

Discussion

Successful perfusion is defined according to the aims of the study; however, this should include uninterrupted ESHP for the desired amount of time and complete collection of the data on cardiac function during the perfusion. For this purpose, a few critical steps in the protocol must be followed.

The heart is an organ with high oxygen and energy demands, and minimizing the ischemic time before cannulation and perfusion is an important principle that must be followed. The process of procurement.......

Materials

Name	Company	Catalog Number	Comments
Debakey-Metzenbaum dissecting scissors	Pilling	342202
MAYO dissecting scissors	Pilling	460420
THUMB forceps	Pilling	465165
Debakey straight vascular tissue forceps	Pilling	351808
CUSHING Gutschdressing forceps	Pilling	466200
JOHNSON needle holder	Pilling	510312
DERF needle holder	Pilling	443120
Sternal saw	Stryker	6207
Sternal retractor	Pilling	341162
Vorse tubing clamp	Pilling	351377
MORRIS ascending aorta clamp	Pilling	353617
Surgical snare (tourniquet) set	Medtronic	CVR79013
2-0 SILK black 12 X 18" strands	ETHICON	A185H
3-0 PROLENE blue 18" PS-2 cutting	ETHICON	8687H
Biomedicus pump drive (modified)	Medtronic	540	Modified to allow remote electronic control of pump speed
Biomedicus pump	Maquet	BPX-80
Membrane oxigenator D 905	SORIN GROUP	50513
Tubing flow module	Transonic	Ts410
PXL clamp-on flow sensor	Transonic	ME9PXL-BL37SF
TruWave pressure transducer	Edwards	VSYPX272
Intercept tubing 3/8" X 3/32" X 6'	Medtronic	3506
Intercept tubing 1/4" X 1/16" X 8'	Medtronic	3108
Heated/Refrigerated Bath Circulator	Grant	TX-150
ABL 800 FLEX Blood Gas Analyzer	Radiometer	989-963
5F Ventriculr straight pigtail cathter	CORDIS	534550S
5F AVANTI+ Sheath Introducer	CORDIS	504605A
Emerald Amplatz Guidewire	CORDIS	502571A
Dual chamber pace maker	Medtronic	5388
Defibrilltor	CodeMaster	M1722B
Infusion pump	Baxter	AS50
Surgical electrocautery device	Kls Martin	ME411
Gas mixer	SECHRIST	3500 CP-G
Medical oxygen tank	praxair	2014408
Cabon dioxide tank	praxair	5823115
Bovine serum albumin	MP biomedicals	218057791