Page 373 - Feline Cardiology

Chapter 25: Pulmonary Thromboembolism and Hypertension 389

monary hypertension (likely forms 1 or 3, above), orrhage from bleeding disorder), and pleural diseases
leading to reversal of the shunt (right-to-left). (e.g., idiopathic chylothorax). Often split heart sounds
Eisenmenger’s physiology typically occurs early on, may be misdiagnosed as extra heart sounds such as sys-
often by 6 months of age, depending on the size of tolic clicks and gallop sounds. Echocardiographic right
the left-to-right shunt and response of the pulmo- ventricular enlargement (often with concentric and
nary vasculature. eccentric hypertrophy) must be differentiated from
concentric right ventricular hypertrophy caused
Signalment by pulmonic stenosis or branch pulmonary arterial
Cats of any age and either sex may have pulmonary stenosis.
hypertension. The signalment of affected cats likely Diagnostic Testing
reflects the signalment associated with the inciting
cause; for example, pulmonary hypertension that coex- Thoracic radiographs are indicated for evaluation of any
ists with congenital heart disease likely is more prevalent patient suspected of having pulmonary hypertension,
in younger patients. since dyspnea is the main clinical abnormality being
pursued. Pulmonary arterial dilation, pulmonary paren-
chymal abnormalities, and signs of right heart enlarge-
History, Chief Complaint, and Physical
Examination ment are possible. Lobar pulmonary artery dilation
seems to be one of the more prominent abnormalities
Pulmonary hypertension alone is not conclusively asso- in cats with pulmonary hypertension. Identification of
ciated with specific clinical manifestations in cats. Based prominent central portions of the pulmonary arteries
on clinical signs observed in patients of other species, that rapidly taper, in conjunction with right heart
such signs as dyspnea, decreased stamina, lethargy, syn- enlargement should raise the suspicion of pulmonary
copal episodes and inappetence could be expected espe- hypertension.
cially in severe cases; often, such signs are difficult to The electrocardiogram (ECG) is insensitive for the
separate from signs caused by the concurrent disorder. detection of mean electrical axis shifts in general in cats,
For example, cats with post-capillary pulmonary hyper- and is not a reliable test for assessing cor pulmonale.
tension caused by congestive heart failure likely are dys-
pneic from the congestion, with an uncertain contribution Echocardiography
to clinical signs from the pulmonary hypertension. Practically speaking, pulmonary hypertension and cor
Physical examination abnormalities likewise could be pulmonale is best identified, albeit indirectly, through
expected to reflect those caused by the predisposing dis- echocardiography. Pulmonary hypertension is consis-
order. Additionally, a split second heart sound (delayed tent with the following pair of findings: absence of pul-
closure of the pulmonic valve) is classically noted in monic stenosis, plus elevated tricuspid regurgitation
dogs and humans with pulmonary hypertension. Such velocity (>2.5 m/s), elevated pulmonic insufficiency
a finding has not been reported in cats, possibly because velocity (>2 m/s), or both. Right ventricular and right
the faster heart rate and softer or obscured heart sounds atrial enlargement, and flattening of the interventricular Pulmonary Arterial Disorders
in a dyspneic cat make such sounds difficult to hear. septum, have been documented in chronic feline pulmo-
Abdominal enlargement due to ascites, jugular venous nary hypertension associated with pulmonary thrombo-
distension, dyspnea due to pleural effusion, and other embolism (Sottiaux and Franck 1999). Other findings
manifestations of right-sided congestive heart failure could include a rapid decrease in right ventricular
stemming from cor pulmonale were not reported in a outflow velocity in midsystole due to the increased resis-
cat with a pulmonary arterial systolic pressure of tance to flow imposed by pulmonary hypertension and
56 mm Hg (Sottiaux and Franck 1999) and appear to be a decreased time to peak right ventricular outflow tract
infrequent compared to such signs in dogs with severe velocity. Tissue Doppler imaging is an emerging applica-
pulmonary hypertension.
tion in other species to evaluate for elevated pulmonary
artery pressure, which appeared to be superior to stan-
Differential Diagnosis dard techniques for identifying even mild elevations in
On physical examination, dyspnea must be differenti- pulmonary arterial pressure in dogs (Serres et al. 2007).
ated from primary airway or pulmonary disease (e.g., Finally, echocardiography is also useful for identifying
allergic airway disease, airway obstruction, pneumonia, underlying causes such as heartworms, a pulmonary
neoplasia), metabolic disease (notably those causing thrombus, or significant left heart disease.
metabolic acidosis), secondary pulmonary disease (e.g., The gold standard for documenting pulmonary
cardiogenic or noncardiogenic edema, pulmonary hem- hypertension is direct measurement of pulmonary