Dissection Techniques and Histological Sampling of the Heart in Large Animal Models for Cardiovascular Diseases

Summary

Due to the complex anatomy, a consistently reproducible dissection and harvesting protocol for cardiac samples can be challenging to implement. This manuscript presents the key elements of some standard cardiac dissection protocols, highlighting both the gross examination approaches and the sampling sites commonly used for histopathologic examination.

Abstract

The standard gross examination and sampling are key elements in the reproducibility and success of experimental studies of cardiovascular diseases carried out in large animals. Considering the complex anatomy of the heart, interspecies differences, and the types of compensatory and pathological reactions, consistent protocols are challenging to implement. The utilization of multiple dissection protocols is usually adapted to suit the prosector's experience, and personal preference continues to be a source of experimental and interobserver variability. Here, the aim is to present the main anatomical features and landmarks, dissection protocols, and histological sampling standards of the heart in some commonly used species (including dogs, pigs, ruminants, and cats) as models of cardiovascular diseases.

Two standard gross examination protocols are presented here. First, the inflow-outflow method, which follows the physiological blood flow direction through the heart and large vessels (frequently used in dogs, ruminants, and pigs), and second, the four-chamber dissection technique (exemplified in cats). Both techniques can be adapted to any species in certain experimental circumstances. The sampling protocols include all the areas of interest (sinoatrial node, ventricles, interventricular septum, atria, valves, and aorta), and if properly carried out, improve both the reproducibility and reliability of experimental studies.

Introduction

Due to the complex anatomy and early rigor, which can interfere with assessing the cardiac wall thickness, the gross examination of the heart is challenging and prone to several technique-related or interpretation errors. This is amplified by the interspecific morphological variations and by the fact that many clinical, major cardiac pathologies (including early cases of coronary heart diseases, fibrosis, arteritis, and amyloidosis) are not associated with any gross changes, being, in essence, histological pathologies. A standardized dissection and histological sample harvesting protocol can bring consistency between observers and, at the same time, comparability and ....

Protocol

The experimental protocol received bioethical agreement (No. 311 from 2022) and was approved by the Bioethics Committee of the University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, in compliance with both national (Law No. 43 of 2014) and European (EU Directive No 63 from 2010) legislation. See the Table of Materials for details about all materials and instruments used in this protocol.

1. Necropsy protocol

NOTE: It is recommended that the same necropsy protocol be used for all the species presented due to easier access it is when performed^....

Results

This protocol was used to visualize anatomical features and collect samples for histological examination of the heart in four different species (dog, cat, pig, and cow). The necropsy protocol was repeated in each of the above-mentioned species but illustrated only in dogs. The necropsy protocol begins with an extensive external examination of the body (Figure 1A) (including the skin, explorable lymph nodes, and exterior mucosa), measuring the overall weight, and scoring the general state of .......

Discussion

When performing the current protocol, several critical steps should be carefully considered for consistent results. In young animals, cardiac measurements are different from those in adults (including ventricular wall thickness), and generally, the heart represents a greater proportion of body weight^11,12. The degree of ventricular hypertrophy can be quantified by applying a general weight formula, the ratio between the left ventricle plus septum divided by the f.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.9% saline solution	B. BRAUN MELSUNGEN AG	W04479004	For washing all the blood, and blood clots from the heart.
10% neutral buffered formalin (NBF)	Q Path	11699404	Materials for collecting histopathology samples.
Bone cutting forceps	HELEN SRL	LS109HV	Sturdy instrument for cutting bone.
Cutting board	Ambition	86304	For an easier manipulation, and cutting the organs.
Decalcifying solution	Thermo Scientific TBD-2	6764004	1:1 mixture of 8% formic acid and hydrochloric acid.
Digital camera	Canon Inc.	PowerShot SX540 HS	For photographic, and videographic documentation.
Forceps	MKD-Medicale	15-430	Dissection instruments.
Histological cassettes	Q Path	720-2215	Materials for collecting histopathology samples. Dimensions: 3 × 2.5 × 0.4 cm
Knife	TEHNO FOOD COM SERV SRL	D2006/15	Sharp blade for cutting soft tissue.
Latex gloves	MKD-Medicale	SANTEX-S	Protection equipment.
Mask	MKD-Medicale	21221	Protection equipment.
Petri dishes	MKD-Medicale	0598-1V	Materials for collecting ancillary testing samples.
Plastic recipients	Corning Gosselin	TP200-02	Materials for collecting histopathology samples.
Scale	ESPERANZA	MEEKS008	For weighing the organs.
Scale	White Deals	72	For weighing the subjects.
Scalpel	MKD-Medicale	10322E	Sharp blade for cutting soft tissue.
Scissors	MKD-Medicale	13-260	Dissection instruments.
Scrub	MKD-Medicale	410100-52	Protection equipment.
Syringes	MKD-Medicale	10573EU	Materials for collecting ancillary testing samples.