1. I usually use a rodent ventilator. You can try to use an hand made balloon but the important thing is to set the tidal volume and the respiratory rate.

2. To evacuate air and fluids I use a small catheter introduced in the thorax. The chest was then closed in layers.

3. To help the animal survive you have to be fast during ligation. The survival depends also on infarct size. I usually tie anterior descending coronary artery 2-3 mm from the edge of the left auricle.

4. ketamine chloride 40 mg/kg ip plus medetomidine hydrochloride 0.15 mg/kg ip. After surgery, all animals were given atipamezole hydrochloride 0.15 mg/kg im. Antibiotic therapy (gentamicine sulphate 10 mg/kg im ) was given during the subsequent 3 days.

Thank you so much Dr. Savi. Useful information. Seems like you have adequate experience in this regard, I'll ask you for more help in the future..

Regards

One more comment as well. You can't see the LCA. You simply know approximately where it should be and take a bit of myocardium. In the end you'll have some animals that die from too large an infarct, some that have a small or no infarct, and other that are just right. If you have 50% survival and appropriate infarct size that would be a good target.

Great point Dr. Ruble.. as you know, Lca is divided into to branches: 1. LAD (left anterior descending) and 2. left circomflex. There is also a very short route for LCA before it divides into these two branches. Is it better to assign the ligation to the artery before it divides, or on the LAD?

One more question, which form of recumbency is better for the surgery to be performed, dorsal or right lateral recumbency??

Best approach per Pfeffer Circ Research paper (1979): ligate LCA between the pulmonary artery outflow tract and the left atrium.; 40-50% mortality within the first 24 hours following occlusion. right lateral placement of animal.

As listed in the other answers, there are many studies using this approach, so I'll add just a few comments. First, the animal should be on a respirator and it helps at closing the chest to have positive pressure of ~5 cm water on the outflow of the respirator to help keep the lungs inflated. Open the chest between the 3rd and 4th ribs on the left side (about half way from the collar bone to the last rib. The left common carotid artery (rodents don't have an LAD), starts more left lateral and angles more medial, so this provides a better view. Open the pericardium and locate the 1st diagonal branch coming off the Left coronary. Ligation just distal to this artery still maintains a reasonable infarct (30-50% of the left ventricle), but preserves a significant part of the base and posterior-apical left ventricle to reduce post ligation mortality, although there still will be post-operative mortality. I also use a Xylazine-Ketamine anaesthetic regime, but long-lasting preoperative analgesics are also essential, and may be supplemented by post-operative analgesia.

Great information Dr. Jones. Thank you for the time you consumed.. I'll certainly need more of you help in the process..

We usually use a volume rodent ventilator (Harvard Scientific) or a pressure control ventilator (TOPO by Kent Scientific), but in our experience, if you do a small cut in the intercostal muscle (we usually puncture with a fine tweezers and separate the incision edges whith a separators made of surgical wire at the size and shape of a small paper clip) just above the zone of the heart that you need to expose for the suture collocation and ligation of the LAD, you don’t need a ventilator, but you need to use ketamine/xilacine for anesthesia, and work fast, usually we take 7 to 10 minutes since incision of the skin to the closure, if you use phentobarbital or similar anesthetic, the rat stops breathing, second if you put a tube for the drainage of fluid and air, you need a valve mechanism for this, because you only perpetuate the neumotorax if you don’t have it, in our experience, a few years ago, We extract fluids and air after the closure of the chest through a Teflon tube settled inside the chest during the surgery and making negative pressure with a syringe, without improvement of the survival, other good anesthetic for this procedure without a ventilator it's cloral hidrate, but I think it's out of the market. if you need help with this, we can make you a video for you.

Dear Dr. Islas,

Thank you so much for your valuable hints. However, we have failed to perform the procedure without a ventilator even with ketamine/xylazine. I think we were not fast enough. Currently we are totally disappointed! So I'd really appreciate if you could send us the video which you mentioned. I bet that will help a lot..

Doing LCA ligation in rat without ventilation is absolutely possible. The key things are

1. Small rat (150g or less) is better tolerating this procedure. If the body weight is over 250g I would do ventilated way.

2. The negative pressure can be reset once the air is removed from the cavity. There is no need to use any tubing or needle suction, just use the fingers to press the chest and move from back to front. Since only one side chest is opened, a little air residual is ok.

3. The animal (both mice and rat) can be survival for as long as 4 months after MI. The key point is a good surgery.

4. The LCA is visible right after the heart is pop out. Quick pop is the key.

Thank you so much for your detailed answer Dr. Gao. That sounds pretty interesting because all the rats that we have used so far were so big, since we believed bigger rats might better tolerate the surgery!! I'll try the procedure with smaller ones. As we have experienced, after opening of the chest, the respiratory rate suddenly decreases as well as the heart rate! You mean that the animal could survive without any ventilator or intratracheal tube only if the animal is small and the ligation is fast?

Yes, the procedure of MI in small size rat is the same as in mice. For detail please check my two papers.

erhe

Dear Dr. Gao

I studied your article entitled "A Novel and Efficient Model of Coronary Artery Ligation and Myocardial Infarction in the Mouse" and many other articles of yours. It was amazing!! I also watched the relevant video in the supplementary file. It`s great to have researchers like you and your colleagues to follow and learn from.

Would you please answer some more questions of mine in this regard?

You have used inhalative anaesthesia (2% isoflurane) to perform the procedure, however we don`t even have such facilities! Is it possible to perform it using a combination of ketamine and xylazine (IP)?

Moreover, as I saw in the movie, I realized that the heart rate of the rodent was very low making the ligation much more easier. am I right? Is it because of the anaesthetic you used? How can we overcome this problem if we don`t have the equipment for inhalation?!

Dear Sir,

Please contact :

Professor Lepran Istvan and check his articles

[email protected]

Best,

Dr. Koncz Istvan

AT FIRST when i established this model, everything was ok. but suddenly i started to have this problem of air bubble inside the chest. no matter how much i remove the air and close the chest or be quick, as sson as i close the chest mice start dying (i can see the air bubble becoming bigger within seconds, even when chest is closed) , and when i reopen the chest, ECG comes back to normal. what could be the problem?? and how to avoid this.

please comment

Syeda, you probably perporate the tracheal bifurcation when you were intubating the rodent that is why the positive pressure is building up into the chest cavity. Try to use a 22-24 gauge indwelling catheter and make sure to go slow and not too deep. Try to do the left lateral approach incision of the chest and when you close the chest cavity, close the muscles and skin separately then you can perform thoracocentesis to remove the air in the chest cavity. I use 25g needle and a 6cc syringe in rat and 30g needle and 1cc syringe in mice and aspirate it slowly but make sure you are away from the heart so you don't puncture it.

hi yasmin,

may be you perforate the tracheal bifurcation when you were intubating the mice, so for that you can follow the suggestions by Dr. tony above.

personally , i started doing the procedure quickly, and while opening the chest , i try to make a small opening and try best to avoid any contact with lungs, so to avoid any lung injury. initially i was using a little piece of cotton in chest to avoid the lungs, but i stopped it later thinking that it might be the problem. and now its all ok.

so main point is a small opening in chest cavity and avoiding lung injury.

i hope it helps.