Terbutaline and atenolol.

Hi Dr. Marie, I’m interested in your thoughts on what may have caused my cat’s death. I’m now regretting not getting a necropsy as I have questions. Callie was a petite, 6-pound, 12-year-old Persian. Her only health issue was that at every yearly exam, it was noted that she had sinus bradycardia, a very slow heart rate. This was never considered an issue because she had no signs of illness.

One morning, after playing and eating per her usual routine, I noticed that her side was moving a little faster than normal as she napped. I took her to the vet in the afternoon. The vet said she couldn’t hear Callie’s lungs move as she breathed. She took a chest x-ray, which revealed that Callie had hypertrophic cardiomyopathy.

The vet pointed to a fuzzy white area on her lungs. She said that area could indicate fluid in the lungs due to possible congestive heart failure, or it could indicate lung disease like asthma or bronchitis, she wasn’t sure. On the overhead view of her lungs, the vet said she thought she was possibly seeing nodules, but wasn’t sure. She said her lungs needed further diagnosis by a specialist. She also said Callie had started to pant while they were doing the x-ray, so she put her in an oxygen cage.

She gave Callie an injection of terbutaline and ¼ of a 25 MG atenolol tablet. This was around 4:30 PM on a Friday. She sent me home with Callie, the two oral medications, and instructions to see a cardiologist on Monday. She said if Callie’s respiration rate didn’t go down by Saturday morning, to take her to the ER on Saturday. She counted it at 50/minute, which I’m guessing was higher than what I saw that morning, given she said Callie was stressed and panting. I never saw Callie pant or act stressed at home.

At home, about 2.5 hours later, Callie started to stagger as if she was going to collapse. My husband and I immediately rushed her to ER, which was a 30-minute drive. Callie died a few minutes before reaching the ER, after suffering terribly.

The whole ride, she was thrashing in the carrier so hard that I worried she was going to hurt herself. One second, her head would be by the carrier door, then she would jerk so violently, a split-second later her head was at the opposite end. I could hear her struggling to breathe and it sounded like she was choking. Every now and then, she would spit up a small amount of clear fluid. It was devastating. I know HCM can cause sudden death by heart attack or throwing a blood clot, but from everything I’ve read about that type of death, it doesn’t seem to match how Callie died.

I’ve read everywhere that atenolol should never be given to cats with sinus bradycardia, uncontrolled congestive heart failure, or lung disease like asthma because it depresses heart rate and airway functions, and can escalate heart failure and breathing problems. Callie had a life-long history of having sinus bradycardia, and the vet said it was possible she had congestive heart failure and/or lung disease like asthma. Should Callie have been give atenolol?

On the other hand, I’ve read that terbutaline shouldn’t be given to cats with HCM because it stimulates the heart rate and can cause heart failure. Should Callie have been give terbutaline?

Even more confusing, I’m reading that atenolol and terbutaline should not be given together because they cancel each other out. Would they have canceled each other out in Callie’s case? Or did they play some kind of deadly tug-of-war with her cardiovascular and respiratory systems?

Or, since Callie had a notoriously slow heart rate, did atenolol dominate over the terbutaline and slow her heart down too much? It sounded like she was suffocating, like she wasn’t getting oxygen. And I am reading about adult humans taking 25 MG atenolol tablets to lower blood pressure. To me, that makes 6.25 MG sound like a lot for a 6-pound cat who perhaps shouldn’t have been given atenolol in the first place.

Or, could the jumpstart shot of terbutaline simply have overstimulated her heart and caused heart failure?

Callie was jumping, running and eating in the morning, and dead less than 10 hours later, 3 hours after receiving these drugs, which I’ve read take a few hours to start working. I know I’ll never have definitive answers, but do you have any thoughts? Do any of the details of Callie’s history, treatment or death reveal anything to you, in your opinion? Thank you.

Hi Dr. Marie, Thank you so much for your response, research and condolences. From what I’ve been reading and the videos I’ve been watching, I’m thinking that Callie didn’t have asthma and more likely had congestive heart failure. I’m sure the vet was trying to help her.

I appreciate your thoughts. I’ve been adopting rescued Persians for decades and never dealt with heart or lung disease before. I know Persians are at increased risk for HCM and I’m sure I’ll continue to adopt them, so this is great information for me to have should I deal with it again. ~April