Pepper has an echocardiogram after surgery, and the veterina…

Pepper has an echocardiogram after surgery, and the veterinarian sees shadows that suggest the possibility of heart disease.  Pepper has no symptoms, however, and is sent home after recovering well from surgery.  Because Pepper is asymptomatic, the veterinarian instructs the owner to monitor for rapid breathing, or _____________, which can be the first sign that heart disease has progressed to heart failure.