Heart Attacks in Dogs

I started to post this under "internal medicine", but it’s in the right place. Dogs (in fact, all domestic animals) very rarely have a heart attack in the sense that we understand it in human medicine.

Myocardial infarction (M.I.) is the technical term for "heart attack".  Myocardium means heart muscle.  Infarction means that the blood supply to something is stopped up, causing damage to whatever has lost its circulation.   Sometimes people say they’ve "had a coronary".  The coronary arteries are the blood vessels that bring oxygen and nutrition to the heart muscle so that it can do its job.  If one of those arteries gets stopped up, the heart muscle it was taking care of gets really sick, really fast.  Maybe it just dies.  If a big enough area of heart muscle is affected, the heart ceases to function and you die. With very small areas of heart muscle damaged, your heart may keep working, but you have chest pain, nausea and all the rest of the signs of a heart attack.

The most common cause of a blockage in these coronary arteries is the build-up of atherosclerotic plaque.  Cholesterol (among other things) builds up a lining of crud inside the blood vessel, making it’s interior diameter smaller and smaller.  This in itself causes poor blood supply to the heart muscle.  If a chunk of the crud breaks off, it flows downstream and can cork the vessel off completely.  Now you’re having a heart attack.

The thing is, it’s rare for domestic animals to have high cholesterol.  There are definitely individual animals that do have high cholesterol and triglycerides (another kind of fat in the blood).  They usually have thyroid problems or other medical problems that contribute to this.  Even when they do have high cholesterol, they don’t develop the atherosclerotic plaque that would clog up their coronary arteries.  Maybe they just don’t live long enough for that to happen. Even really obese human children don’t develop that kind of heart problem before they are teenagers.  At any rate, dogs and cats and horses and cows do not have coronary arteries clogged up with junk.  This means that they very rarely have something that stops up an artery to cause death of the heart muscle.  If they do, it would be a blood clot or something similar.

What all that boils down to is that, with rare exceptions, dogs don’t have heart attacks.  Whenever I have a patient that dies suddenly with no explanation, we encourage a post-mortem examination.  If nothing shows up to the naked eye, we send tissues (pieces of the organs) to the pathologist to examine under the microscope.  With a sudden death case, we always send the entire heart.  Myocardial infarction has been reported back to me exactly one time in twenty-eight years.  It can happen, but it doesn’t happen very often.

So why do people tell you that their pet died from a heart attack?  Where did they get such an idea? Sometimes they just invent it.  You extrapolate your answers from what you know.  Why do people die suddenly?  Heart attacks.  Why wouldn’t a dog be the same? See the above.

I’m afraid that, in years past, most people have heard the pet-heart-attack story from a lazy veterinarian.  Think about it: people have experience with heart attacks.  They don’t have much understanding of other types of heart problems.  If the pet didn’t die from a heart attack, what did cause the sudden death?   If you (as a doctor) were presented with a pet who died suddenly and you could not determine the cause, which would you rather do?  1. Give a lengthy explanation of why it’s probably not a heart attack (see above) and end by saying that you don’t have a clue, OR 2. Solemnly pronounce that the pet died of a heart attack.

Two good things here: the first is that our pets are unlikely to have a heart attack.  The second is that most veterinarians won’t give you that kind of a BS answer these days.  Would you rather have an earnest "I don’t know" or a solemn load of BS?  Would "I don’t know" satisfy you?  See comments below.

708 thoughts on “Heart Attacks in Dogs

  1. Alyssa says:

    My Black Lab died suddenly this week, she was only 6 years old. The vet told us he could do an autopsy but it could cost $200 being a college student that is way beyond my budget. He stated just by looking at her she either had a stoke or a heart attack. After reading your article I feel mad knowing thats the excuse vets give to people. What if she had a heart problems all these years and the vets did not know, maybe this could have been prevented. It just makes me sad that I dont know the reason my best friend died.

    • Darlene Long says:

      My dog died on Wednesday at the vet don’t know why she died either they gave you this reason they died was from an heart attack dogs don’t have heart attacks

      • Doc says:

        Hello, Darlene,

        Dogs don’t have coronary artery disease as people do, with the plaques that break loose and stop an artery, causing a “heart attack”. That doesn’t mean that they can’t have heart failure. It is difficult to determine the cause of sudden death, so we often assume it is a heart condition. We cannot really be sure without a complete post-mortem examination and sending tissues to the pathologist for microscopic examination. When this is not an option, we take our best guess. Veterinarians often use the phrase “heart attack” because people understand it, and its easier than going through along explanation of what we don’t know.

        • Dee says:

          My 6 year old jack russell passed away on mothers day , we found her in her bed in a laying position with arms and legs out , her tounge was hanging out of her mouth and her eyes was closed , she had also opened her bowels, in the morning she was running around the house like normal no signs seen of illness , when we looked back at our dog camera , our jack russell appeared to be walking around very slowly standing in one position staring at the floor or wall , she moved slighty round the kitchen then went back to her bed and we found her when she passed away , any ideas if this could of been a heart attack as we took her to the vets and they said her tummy felt fine she looks like a healthy dog we cant understand what caused her to pass away so young

          • Doc says:

            Hello, Dee,
            The standing and staring sounds like something affecting her brain, a stroke-lie event, perhaps. These cases are very difficult to get to the bottom of, even with lots of testing, sometimes.

            I am sorry for your loss.

          • Molly says:

            Hi Dee, I’m so sorry for your loss. My 9.5 year old English Bulldog passed away on January 23rd under almost identical circumstances. She was running around the backyard playing with her ball when I saw her sit down suddenly. She was starring at nothing and didn’t respond to me. She took about 3 or 4 steps and collapsed in the snow. We ran outside and found her tongue sticking out, her eyes open with fixed and dilated pupils, completely limp and not breathing. From the time I put her out back to her collapse was only 5 or 6 minutes and I saw the whole devastating event. She was gone by the time my husband picked her up from the snow. She was almost 10 years old, which is above average life span for a bulldog, but otherwise healthy and very frequently checked by the vet (at least once every 8 weeks or so due to my fears about her aging). I wanted to share this with you for a couple reasons. First, although no autopsy was done, my vet also believed her death to be associated with some catastrophic event in her brain and second, to let you know having seen the whole thing unfold it was very quick and despite seeing it and getting her to the emergency vet immediately (less than 10 min from the time she collapsed to them attempting to resuscitate) they said that there was nothing anyone could have done to save her. My vet went so far as to say that the whole emergency vet team could have been in my backyard at the time of Marcy’s collapse and the result would have been the same. I just wanted you to know that there was nothing you could have done to prevent or save her and, given how similar the circumstances surrounding her death were to what happened to my Marcy, I believe she didn’t have any pain or awareness. I have a 3 and 5 year old daughter but losing Marcy felt/feels like I lost my first born. I loved her with every fiber of my being. She was my soulmate and I miss her more than I could ever express with words. My heart aches for you. I hope knowing that someone else can relate and truly understands what you’ve been through can bring you some comfort!
            My deepest sympathies,
            Molly

          • Kris says:

            Dee my 9 year old doodle died 3 days ago almost exactly what you explained. She ate her breakfast with my other doodle like any other day and ran outside to use the bathroom. Upon returning a few minutes later she was walking very slowly with her nose to the ground. I thought she was sniffing something. She then came into the house and collapsed. Her legs were spread out snd she lost control of her bowels. She died before we could get her into the car. I’m devastated. She was our baby.

          • Felicia says:

            Sorry for your loss. My dog passed away today. Same as your dog he was playing in the yard with my kids and suddenly he got slow laid down and passed. I was at work my 12 year old was freaking out. I got it all on camera also

          • Doc says:

            Hello, Felicia,
            Thanks for sharing your story. I cannot imagine how difficult this was with your child passing this on to you.

          • Katie says:

            My 5 year old lab passed away on Monday. She was a very healthy, active dog… the only health issue was a possible torn ACL a few years ago which healed… probably wasn’t a torn ACL after all. She went out at 628 and and at 630 I found her laying in the grass, tongue was blue and she wasn’t breathing. I tried CPR the best I could do on a 55lb lab/pit mix. I keep going back to thinking I Stopped CPR too soon. An autopsy is being done, but so far the only finding was scant of blood in her stomach. I’m just lost.

          • Doc says:

            Hello, Katie,
            Statistically, CPR in cases like this is almost never successful, no matter who is doing it, or how long they try. So don’t beat yourself up about that.

            I hope the post-mortem will give you some answers. Best wishes.

        • Dawn Rosen says:

          My almost 12 year old cockapoo died suddenly yesterday and I can’t stop blaming myself. She was fine and happy yesterday morning and had a big breakfast. I had a vet appointment scheduled because I know that she has a history of a heart murmur and had started to have an occasional cough that sounded a bit asthmatic. She was fine before they took her in, but when they brought her back out to me, she went into some sort of pulmonary distress, they said because she was stressed and panicked. They took an xray, said her heart was enlarged, tried oxygen and told me to go to the emergency vet, so I drove there, arrived, pulled into their parking lot and she actually seemed better, so i pulled back out, thinking that maybe she’d get better being calm at home and would have had another panic attack (maybe fatal) going in there. So, i started driving home and it started up again with the labored breathing and she jumped off the seat to sit on the floor. So, I turned back and tried to get back to the vet and was driving in circles trying to get back on the parkway because I was scared. She then was trying to get back up to the seat next to me, so i pulled over and put her next to me and I knew. Her body jolted a bit (i’ve seen that too many times before) – and she went limp. I drove 85 mph anyway back to the emergency vet, they tried to revive her, but it was too late. How do I process this and make sense of it to not feel so tortured?

          • Doc says:

            Hello, Dawn,
            Thank you for sharing your story. I can see how you would have felt letting the dog go home to “de-stress” would have been the appropriate action to take. Really, when a patient is lost this quickly, it is unlikely that they could have been restored to health. I have a patient with congestive heart failure who has had two trips to the specialty hospital for critical care treatment with oxygen and round-the-clock monitoring. He has been able to come home both times, but he is just “sitting on the edge” of another crisis. His heart is barely strong enough to function with the assistance of his medicines, and any additional stress gets him de-compensated.

            It is obvious that you feel guilty about your decision, but I don’t think that you should. Some things just can’t be fixed.
            I am sorry for your loss.

          • Patti H says:

            My 8 yr old dog died 2 weeks ago. He was his normal self. Around 830pm he jumped up put his head on my lap to be petted, put his paw on my hand. His nose was cold so I covered it. He got down and laid in his spot in front of me. I sat and watched TV. At around 12 I said Bubba do u need out and he didnt move. I touched him, he was cold and had passed away. Not one sound had he made. Looked as if he was sleeping. Eyes closed and moth shut. I’m trying to reason how or why.

          • Doc says:

            Hello, Patti,
            Wow. We frequently say that we wish our pets could just pass away peacefully in their sleep, but we are thinking much later in life.

            I wish that I could give you some closure here. I can only say that it doesn’t sound like there was anything you neglected. Sometimes bodies just fail.

            I am sorry for your loss.

          • john kierans says:

            dawn i had the same problem with my yorkie . took him to a cardiologist put him on viagra said he would live for 4 months . a day & a half later i found him by my bed lifeless . that day he was had laboured breathing can not stop thinking should i have taken him to the ER vet that night . the cardiologist said to keep a eye on him i keep on blaming my self

          • Doc says:

            Hello, John,
            I am sorry to hear about your loss These things are often hard to predict. We just do the best we can. I’m sure you miss him.

          • Kat says:

            Good morning Dawn Rosen. I am just coming across this website, and reading your story. I see that it has been almost a year since you lost your pet and there is never a healing for it. I am sorry for your loss. Your story stood out to me because I just recently lost my dog under similar circumstances. I took her to see a vet for some bloodwork and coughing they recommended she’d have an x-ray, she walked in her happy energetic self, and left on oxygen to the emergency hospital. I lost her two days later at home, she never became herself again she was weak didn’t want to eat and seemed lethargic she passed away in my arms. I am just wondering if you ever found out what was the cause of the loss of your beloved pet? This was a sudden loss for me, I know I am forever heartbroken.
            Thank you for sharing your story.

        • Casey w. says:

          My 1 year old Pomeranian Millie who seems to be in perfect health suddenly passed away recently I woke up for work took her out to potty and she ate breakfast with me and she was acting like her regular self I put her on our bed and she was playing on the bed and my fiancé said she was running up and down the bed and 25 minutes after I left he said he heard her yelp and then seen she was bleeding out of her nose and said he picked her up and her heart was beating really fast/hard and she was gone within 2 minutes. We’re just having a tough time trying to figure out how our little princess could be playing and then dead all of a sudden without warning. He’s thinking she might of had a heart defect and overexerted herself because of how small she was she was a runt and only grew to be 2 1/2 pounds. We aren’t able to do any after death tests because this happened March 24th and we already buried her. Just wanted some assumptions on what could have possibly happen even though we won’t know 100% what actually happened and we understand that just haven’t heard a story exactly like ours with the bleeding out the nose.

          • Doc says:

            Hello, Casey,

            I’m sorry that I don’t have anything to add. It certainly sounds like some type of birth defect that just finally gave way.

            I am sorry for your loss.

          • Ashley G says:

            I had a 7 month old pit bull female puppy. Took her for a 1/2 mile walk, once we got home she completely urinated herself. Then started to convulse and choke , I tried to give her cpr.. then she laid there while breathing slowly with bright red blood gushing from her mouth and nose.. she passed away within 5 minutes.. it’s a mystery.

          • Doc says:

            Hello, Ashley,
            That sounds like there must have been some congenital problem with her heart and the blood vessels in her lungs. I doubt that anything could have been done to prevent this or save her.

            I am sorry for your loss.

        • Kathy Gooch says:

          My 17 year furbaby just fell over dead , lifeless with in 5 to 10 seconds after coming outside with me and my other boy. I ran over grabbed him up and started CPR I am happy to say he is alive and well only thing is he is more clingy than before but I don’t mind one bit

        • Deepa A Reddy says:

          Hello doc,I left my dog to play and he didnot come back home ,I found him dead after 1 and half day ,when I found him on the roadside I thought he is sleeping,but when I went near he was dead with his mouth closed tightly ,and no insects were on him ,so can I know how many hours before he died ,I tried asking people in that area they said he was hit by a bike from behind to the private parts ,and after even that he crawled from road to the road side and then they didnot see wht happened to him ,whenni found his body the blood was dried under the tighs and still I am not knowing wht is the reason for his death ,he died because of injury to back means private part or ,he got heart attack after crawling some way ?

          • Doc says:

            Hello, Deepa,
            I had some bugs in my comments, so just now seeing this. Often with a blow from a vehicle, something inside is damaged, and there is internal bleeding. The patient goes into shock, because there isn’t enough blood inside the vessels for his circulation to work. Often you don’t see anything at all on the outside of the body. I am sorry for your loss.

        • Brooke says:

          My dog is scheduled to have a teeth cleaning this Friday. They do these from 12:00-3:00 pm on this day. He is 8 years old and a 3 lb long haired chihuahua. He was recently diagnosed with Degenerative Valvular Disease- moderate; MMVD B2 (moderate left atrial enlargement due to moderate mitral regurgitation). This was diagnosed by a Veterinary Cardiologist through an echocardiogram. The vet recommended these every 6 months along with vetmedin twice a day. The echocardiogram was suggested by my vet before putting him under anesthesia for his teeth cleaning. He stated that the cardiologist said there is a mild, at most, moderately increased risk for anesthesia; avoidance of dexdomitor, ketamine, and very aggressive usage of IV fluids is recommended. Elective anesthesia may still be performed. My dog needs multiple extractions and the tartar and plaque are very bad or I would consider skipping the teeth cleaning all together. At this point I’m worried his teeth are a detriment to his health. He has had his teeth cleaned once before when he was 4. Although he seemed in rough shape when I picked him up, he made it through without any problems known to me. This was with a different vet. My concerns now are his age since he is 8, his size since he is 3lbs, his heart condition, and the fact his procedure won’t begin until around 12:00-3:00pm that day. He is a small dog and I’m nervous about hypoglycemia since I was told to withhold food after 10:00pm. I wanted to get your opinion on this situation. I am so nervous for this teeth cleaning and I’m about 8 months pregnant and am super attached to my sweet dog, especially right now. We’ve talked to a specialist, we’ve had his preprocedure bloodwork completed and cleared, and the doctor says they will monitor his heart on the EKG and will stop the procedure at any signs of distress. He also stated that he planned on only having my dog scheduled for any procedures this day so he can focus on him.

          • Doc says:

            Hello, Brooke,
            It sounds like everything possible is being done to ensure a successful outcome. I know you are worried, but if there are heart valve problems, you don’t want that crud from the mouth getting in the bloodstream and potentially making it worse. The periodontal disease increases the risk of problems with his heart and with his kidneys, so it is in his best interest to get it cared for. Best wishes.

        • Malinda says:

          My Dog Ki Baloo Bear passed on Sunday morning May 15 2022. Completely sudden no warning, he was 3 and a half would be 4 in october of this year. Ki was a boxer shepard mix, we think a rescue we went to dog park saturday, sunday morning we went for a walk he pottied with no issues came in ate his breakfast about 10 min later he went up stairs let out an elongated howl we have two other dogs in the house and he hit the bathroom floor. We did CPR on him I did everything I could we rushed him to the ER vet and by the time we got there he was lifeless I am so sick about it I am so broken he was my baby boy. The vet said he most likely passed in the car ride or even before we left and there was nothing they could do they said they suspect he had a blood clot that went to the heart. I just dont get it, he was fine no signs of any issues help me understand this

          • Doc says:

            Hello, Malinda,
            I wish that I could give you some closure here. We can see dogs that have had a heart muscle problem their whole lives and then just die suddenly with no warning at all. The only way to make the diagnosis is by microscopic examination of the heart muscle. Some dogs have an aneurysm that bursts.

            Sometimes even with a complete post-mortem examination we still cannot give an answer.

            I am sorry for your loss.

      • Ahalya says:

        My greyhound died last week Monday, all of a sudden. He was just 2 months shy of turning 9, and was getting long walks and was on a senior dog diet plan. He was a bit lethargic since morning, but he went for a short morning walk, ate his breakfast, drank water and slept till about 5:00 pm. Since greyhounds sleep a lot during the day, that was not unusual at all for him. In the evening, my husband and I took him to a nearby trail to walk, and that was when we observed that he was not his usual self: Not running to sniff and pee as soon as he was out of the car. Instead, he was just standing there, waiting, looking down. We went for a walk for about a mile, and he suddenly stopped, and would not move forward. My husband decided to go get the car from the parking to the place he stopped, and he sat back in the car. I was worried that he was over-heated, and tried to give him some water in the car. He would not drink. Then I noticed that he was not panting, but his heart was racing. At this point, we thought getting him home on his bed would be good for him, so we brought him back home. He was able to walk to his bed and lie down. I tried giving him water and his evening meal, but he would not drink or eat. He was lying that way for about 45 minutes, then he started walking around restlessly. He was getting dizzy at this point, and nearly fell over, but I caught him in time. By now, both my husband and I knew something was wrong. He then started howling frantically for help. I had never heard such a sound from him before – he barely even barked usually. We decided to take him to the emergency vet, and carried him to the car. The vet was 20 minutes away, and we were hoping and praying that we got there in time. However, mid-way, he stopped howling and gave a deep sigh. When we got to the vet, they said there was no heartbeat or pulse. They tried 10 minutes of CPR, and adrenaline shot, but nothing could revive him. It was really devastating and at that time, we didn’t request a post-mortem. I am still trying to find out what had happened, and have been researching online since then – but I am left with more questions than answers.

        • Doc says:

          Hello, Ahalya,
          I understand that you have more questions than answers. That is usually the case in such situations. I’m sorry that I don’t have some answers for you.

      • Mrs mo dorey says:

        Is there anywhere in dorset surrounding areas that deal with jack russell who has been diagnosed with a hole in the heart cm long heart murmur and enlarged heart she is 7mths old