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Heartworm: Clinical Severity Heartworm: Dirofilaria Versus Acanthocheilonema 1228.e1

Heartworm: Clinical Severity
VetBooks.ir Classification of Heartworm Disease Severity Based on Signs, Physical Examination, and Radiographic Findings

Class Clinical Signs Examination Findings Radiographic Findings
1 None to occasional cough Normal examination No lesions
2 Occasional cough and mild to moderate Increased lung sounds Slight pulmonary arterial enlargement
exercise intolerance
Fair general condition Circumscribed perivascular density plus mixed
alveolar-interstitial lesions
3 Persistent cough, moderate to severe Increased lung sounds Moderate to severe pulmonary arterial enlargement
exercise intolerance
Caval syndrome Weight loss, cachexia Accentuated or split S 2 RV enlargement
Respiratory distress Right apical gallop Diffuse and severe pulmonary infiltrates
Overt right heart failure Tachypnea, dyspnea
General loss of condition
With permission from Fox P: Textbook of canine and feline cardiology: principles and practice, St. Louis, 1999, Saunders, p. 707 and American Heartworm Society guidelines (https://heartwormsociety.org/
images/pdf/2014-AHS-Canine-Guidelines.pdf, page 15; accessed Feb. 13, 2018).

Differentials, Lists, and Mnemonics

Heartworm: Dirofilaria Versus Acanthocheilonema

Differentiating Characteristics of Acanthocheilonema (Formerly Dipetalonema) reconditum and Dirofilaria immitis

Number in Blood Motion Shape Length (Modified Knott Test)
Acanthocheilonema reconditum Usually few Progressive Curved body 263 microns (250-288 microns)
Blunt head
Curved or “buttonhook” tail
Dirofilaria immitis Usually many Stationary Straight body and tail 308 microns (295-325 microns)
Tapered head
Modified from Ettinger S, Feldman E, Côté E: Textbook of veterinary internal medicine, ed 8, St. Louis, 2017, Saunders, p. 1319.

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