What is the primary clinical concern with cats infected by Dirofilaria immitis?

The primary clinical concern with cats infected by Dirofilaria immitis, commonly known as heartworm, is pulmonary hypertension. When heartworms infest a cat, they often do not reside in the heart like they do in dogs; instead, they tend to migrate to the pulmonary arteries. This can lead to significant respiratory issues and elevated blood pressure in the lungs, which is referred to as pulmonary hypertension.

In cats, heartworm disease can manifest as a variety of symptoms. However, the significant concern of elevated pulmonary pressure can result in severe complications and is the primary reason this condition is critical in feline patients. Cats may experience difficulty breathing, coughing, and other serious respiratory symptoms that stem from this condition.

Aberrant migration of worms can occur but is not the primary clinical concern when evaluating the overall impact of Dirofilaria immitis in cats. It may lead to unusual clinical signs if worms migrate outside the usual pathway, but the overarching danger of pulmonary damage from the worms' presence in pulmonary arteries represents the more pressing health risk for affected cats.