Ascending Aortic Constriction in Rats for Creation of Pressure Overload Cardiac Hypertrophy Model

Summary

We describe a stepwise procedure for creating pressure overload and left ventricular hypertrophy in Wistar rats by constriction of the ascending aorta using a small metallic clip. This model is extensively used for studying remodeling changes during cardiac hypertrophy and for identifying and evaluating strategies for regression of such changes.

Abstract

Ascending aortic constriction is the most common and successful surgical model for creating pressure overload induced cardiac hypertrophy and heart failure. Here, we describe a detailed surgical procedure for creating pressure overload and cardiac hypertrophy in rats by constriction of the ascending aorta using a small metallic clip. After anesthesia, the trachea is intubated by inserting a cannula through a half way incision made between two cartilage rings of trachea. Then a skin incision is made at the level of the second intercostal space on the left chest wall and muscle layers are cleared to locate the ascending portion of aorta. The ascending aorta is constricted to 50–60% of its original diameter by application of a small sized titanium clip. Following aortic constriction, the second and third ribs are approximated with prolene sutures. The tracheal cannula is removed once spontaneous breathing was re-established. The animal is allowed to recover on the heating pad by gradually lowering anesthesia. The intensity of pressure overload created by constriction of the ascending aorta is determined by recording the pressure gradient using trans-thoracic two dimensional Doppler-echocardiography. Overall this protocol is useful to study the remodeling events and contractile properties of the heart during the gradual onset and progression from compensated cardiac hypertrophy to heart failure stage.

Introduction

Small animal models are the most preferred tools for the study of chronic changes in the development of cardiac hypertrophy and its progression to heart failure. Heart failure models by surgical methods were originally developed in rats as these animals are most suitable for open chest surgical procedures, echocardiography and evaluation of hemodynamic parameters. They also provide adequate post mortem samples for tissue, cellular and molecular level studies¹. Constriction of the ascending aorta is one of the most common and successful surgical models for creating pressure overload heart failure^2,3. This model is well suited....

Protocol

Animal experiments were performed after obtaining approval from the Institutional Animal Ethics Committee. Wistar rats were housed under a 12 hr dark to light cycle, constant room temperature (24 ± 2 °C) with food and water ad libitum (as per the CPCSEA guidelines).

1) Pre-operative Care and Anesthesia

1. Keep rat (approximately 200 g body weight) under antibiotic umbrella 24 hr before surgery by administering amoxicillin orally (dose: 500 mg/L of water).
2. Sterilize all surgical tools (such as scissors, forceps, clip applicator, suture needles, and needle holder) by autoclaving at 121 °C for 1....

Results

In our experiments we are able to achieve more than 80% survival rates. The effectiveness of aortic constriction was confirmed by performing Doppler echocardiography. Rats (n=6) with a pressure gradient of about 60 mm of Hg at the aortic constricted site were observed for 8 weeks and sacrificed to analyze for the development of cardiac hypertrophy (Figure 1). After 8 weeks post-surgery echocardiographic evaluation revealed a significant increase in left ventricular parameters such as inter ventricular se.......

Discussion

There are several surgical models for the induction of pressure overload as well as cardiac hypertrophy and heart failure. In small animals, Lorell and colleagues developed the model we have described here and they reported the occurrence of compensated cardiac hypertrophy 8 weeks post aortic banding⁵. Cardiac changes gradually progress to a decompensated state and then result in heart failure. The main advantage of this model is the gradual onset of increase in left ventricular pressure and thus similar to cl.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Wistar rats			Maintained at ARF, RGCB
Inhalation anaesthesia systems	VetEquip	AB19276
Rodent ventilator	CWE Inc	SAR- 830/AP
Rat tracheal cannula	CWE Inc	13-21032
Ultrasound system	Philips	HD7
Ultrasound transducer	Philips	S 12
Titanium clip (small)	Horizon	1204
Clip applicator	Weck	137081
Electric shaver	Vinverth	VBT0817
BP blade (size:11)	Surgeon	REF10111	Preparation of surgical site
Tramadol	Orchid health care	OCH043
Amoxycillin Hydrochloride	Ranbaxy
Isoflurane	Piramal health care	A23M10A
Syringes	BD	2015-09
4-0 braided silk	Diamond
3-0 prolene	Johnson&Johnson	NW018
Surgical tape	Romsons	SH 6301
Povidone iodine	Win Medicare
Temp. controlled heating pad	Flamingo	HC1003