A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Summary

This protocol presents a model of long-term ventricular fibrillation in rat hearts induced by continuous stimulation with low-voltage alternating current. This model has a high success rate, is stable, reliable, and reproducible, has a low impact on cardiac function, and causes only mild myocardial injury.

Abstract

Ventricular fibrillation (VF) is a fatal arrhythmia with a high incidence in cardiac patients, but VF arrest under perfusion is a neglected method of intraoperative arrest in the field of cardiac surgery. With recent advances in cardiac surgery, the demand for prolonged VF studies under perfusion has increased. However, the field lacks simple, reliable, and reproducible animal models of chronic ventricular fibrillation. This protocol induces long-term VF through alternating current (AC) electrical stimulation of the epicardium. Different conditions were used to induce VF, including continuous stimulation with a low or high voltage to induce long-term VF and stimulation for 5 min with a low or high voltage to induce spontaneous long-term VF. The success rates of the different conditions, as well as the rates of myocardial injury and recovery of cardiac function, were compared. The results showed that continuous low-voltage stimulation induced long-term VF and that 5 min of low-voltage stimulation induced spontaneous long-term VF with mild myocardial injury and a high rate of recovery of cardiac function. However, the low-voltage, continuously stimulated long-term VF model had a higher success rate. High-voltage stimulation provided a higher rate of VF induction but showed a low defibrillation success rate, poor recovery of cardiac function, and severe myocardial injury. On the basis of these results, continuous low-voltage epicardial AC stimulation is recommended for its high success rate, stability, reliability, reproducibility, low impact on cardiac function, and mild myocardial injury.

Introduction

Cardiac surgery is usually performed via thoracotomy, with blocking of the aorta and perfusion with a cardioplegic solution to arrest the heart. Repeat cardiac surgery can be more challenging than the initial surgery, with higher complication and mortality rates^1,2,3. Furthermore, the conventional median sternotomy approach may cause damage to the bridge vessels behind the sternum, the ascending aorta, the right ventricle, and other important structures. Extensive bleeding due to the separation of connective tissue, sternal wound infection, and sternal osteomyelitis ....

Protocol

All the experimental procedures and protocols used in this investigation were reviewed and approved by the Animal Care and Use Committee of PLA General Hospital.

1. Preparing the Langendorff apparatus

1. Prepare the Krebs-Henseleit (K-H) buffer. To prepare the K-H buffer, add the following to distilled water: 118.0 mM NaCl, 4.7 mM KCl, 1.2 mM MgSO₄, 1.2 mM NaH₂PO₄, 1.8 mM CaCl₂, 25.0 mM NaHCO₃, 11.1 mM glucose, an.......

Discussion

This protocol establishes an animal model of long-term VF in isolated rat hearts that has not been previously reported. Additionally, different electrical stimulation conditions were compared in this study. This study provides a model for studies related to ventricular fibrillation arrest during cardiac surgery.

The success rate of the model is a very important indicator that is related to personnel, time, and economic costs. In VF models, the success rate includes whether VF can be induced in.......

Materials

Name	Company	Catalog Number	Comments
0 Non-absorbable suture	Ethicon, Inc.		Preparation of the isolated heart
95% O2 + 5% CO2	Beijing BeiYang United Gas Co., Ltd.		K-H buffer
AcqKnowledge software	BIOPAC Systems Inc.	Version 4.2.1	Software
Automatic biochemistry analyzer	Rayto Life and Analytical Sciences Co., Ltd.	Chemray 800	CK-MB assay
BIOPAC research systems	BIOPAC Systems Inc.	MP150	Hardware
Blunt needle (20 G, TWLB)	Tianjin Hanaco MEDICAL Co., Ltd.	H-113AP-S	Modified Langendorff perfusion system
Calcium chloride	Sinopharm Chemical Reagent Co.,Ltd	10005861	K-H buffer
CK-MB assay kits	Changchun Huili Biotech Co., Ltd.	C060	CK-MB assay
Curved forcep	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
EDTA	Sinopharm Chemical Reagent Co.,Ltd	10009717	K-H buffer
Electrical stimulator	BIOPAC Systems Inc.	STEMISOC	Hardware
Filter	Tianjin Hanaco MEDICAL Co., Ltd.	H-113AP-S
Glucose	Sinopharm Chemical Reagent Co.,Ltd	63005518	K-H buffer
Heparin sodium	Tianjin Biochem Pharmaceutical Co., Ltd.	H120200505	Preparation of the isolated heart
Isoflurane	RWD Life Science Co.,LTD	21082201	Preparation of the isolated heart
Magnesium sulfate	Sinopharm Chemical Reagent Co.,Ltd	20025118	K-H buffer
Needle electrodes	BIOPAC Systems Inc.	EL452	Hardware
Ophthalmic clamp	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Ophthalmic forceps	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Ophthalmic scissors	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Perfusion tube	Tianjin Hanaco MEDICAL Co., Ltd.	H-113AP-S	Modified Langendorff perfusion system
Potassium chloride	Sinopharm Chemical Reagent Co.,Ltd	10016318	K-H buffer
Sodium bicarbonate	Sinopharm Chemical Reagent Co.,Ltd	10018960	K-H buffer
Sodium chloride	Sinopharm Chemical Reagent Co.,Ltd	10019318	K-H buffer
Sodium dihydrogen phosphate dihydrate	Sinopharm Chemical Reagent Co.,Ltd	20040718	K-H buffer
Sprague-Dawley (SD) rats	SPF (Beijing) biotechnology Co., Ltd.	Male, 300-350g	Preparation of the isolated heart
Thermometer	Jiangsu Jingchuang Electronics Co., Ltd.	GSP-6	Modified Langendorff perfusion system
Tissueforceps	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Tissue scissors	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Toothed forceps	Shanghai Medical Instrument (Group) Co., Ltd.		Preparation of the isolated heart
Ventilator	Chengdu Instrument Factory	DKX-150	Preparation of the isolated heart
Water bath1	Ningbo Scientz Biotechnology Co.,Ltd.	SC-15	Modified Langendorff perfusion system
Water bath2	Shanghai Yiheng Technology Instrument Co., Ltd.	DK-8D	Modified Langendorff perfusion system