06/03/2026
🙌🏼 Ready to level up your ECG interpretation skills? Once you’ve gotten down the top 5 arrhythmias (see previous post), it’s time to get familiar with these:
1️⃣ SVT is NOT sinus tachycardia: the QRS is narrow but the rate is rapid and P waves are abnormal or hidden. Find the cause - hypovolemia, pain, thyroid storm, etc. and treat!
2️⃣ V-tach: Monomorphic = not great, but more stable. Polymorphic QRS = more unstable myocardium, more urgency. Find underlying cause and treat the patient, keeping in mind felines are more sensitive to lidocaine than canines- consider propranolol if you’ve got it!
3️⃣ A-fib: You’ll catch it more often in giant breed dogs. The rhythm is irregularly irregular, meaning there is no regularity in the R-R interval. Ascults as “sneakers in a dryer”. Patients on pre-existing rate control (diltiazem, digoxin) may have heart rate decrease on induction - know your patient's baseline!
4️⃣ Left and Right BBB: Both can be mistaken for V-tach because of the wide QRS. The differentiator: BBB has visible P waves with a fixed, normal PR interval before each QRS, while V-tach does not. Can be a benign incidental finding under anesthesia, or indicate structural underlying heart disease.
5️⃣ Reflex bradycardia: Can often be seen after alpha 2 agonist or vasopressor administration due to increase in vasoconstriction. Use caution when reflectively reaching for Atropine or Glyco in these cases! BP is often adequate (or high!) and lower than typical heart rate can be tolerated transiently.
🧐Which of these do you see most often? Let me know the number ( 1️⃣2️⃣3️⃣4️⃣5️⃣) in the comments! 👇🏼