Page 271 - Feline Cardiology

278 Section G: Congestive Heart Failure

moderately sensitive (72%) and specific (74%) for left tomatic cats. In a large study of cats diagnosed with
atrial dilation. HCM, sinus tachycardia was not more frequent in cats
Cats with right heart failure often have a dilated with heart failure compared to cats without symptoms
caudal vena cava, right heart enlargement, pleural effu- (Atkins et al. 1992). A left axis deviation (or left anterior
sion, and possibly loss of abdominal detail suggestive of fascicular block pattern) is commonly seen in cats with
ascites (see Figure 19.12). Assessment of a dilated caudal HCM (or in normal cats). Other arrhythmias that may
vena cava in cats is subjective, since there are no studies be present in cats with heart failure include third-degree
assessing caudal vena cava size in cats. Often the caudal atrioventricular block, atrial standstill, ventricular tachy-
vena cava is dilated and tortuous when there is severe cardia, or atrial premature complexes.
right heart disease. In dogs, the ratio of the diameter
of the caudal vena cava to the diameter of the descend- Echocardiogram
ing aorta measured on a lateral thoracic radiograph
>1.5 was strongly suggestive of right heart disease Basic “triage” echocardiogram
(Lehmkuhl et al. 1997). Caudal vena caval diameters A “triage” echocardiogram is useful in emergency situa-
may be indexed to the diameter of the T5 or T6 vertebra, tions to define whether dyspnea is due to heart failure
and the mean normal CVC : V ratio is 0.75 ± 0.13, so a or primary respiratory disease. The purpose of the triage
echocardiogram is to establish whether there is signifi-
caudal vena caval diameter equal to or greater than the
Congestive Heart Failure and Bucheler 1995). A globoid-shaped cardiac silhouette signs and help define whether emergency cardiac treat-
cant enough cardiac disease to cause the patient’s clinical
diameter of T5 or T6 may indicate dilation (Buchanan
ments are needed, which may include thoracocentesis,
and cardiomegaly may be seen in cats with pericardial
pericardiocentesis, diuretic therapy, anticoagulant
effusion.
therapy, and inotropic therapy. The essentials of the
There is a variable rate of resolution of cardiogenic
pulmonary edema and pleural effusion in response to
significant pleural effusion that would require immedi-
diuretic therapy. Although diuretics have an acute onset
of action following intravenous administration and with triage echocardiogram are to identify whether there is
ate thoracocentesis, to evaluate for pericardial effusion
repeated doses for treatment of dyspnea, radiographic and/or cardiac tamponade, to identify significant left or
improvement still lags behind clinical improvement by right atrial dilation, and to evaluate myocardial struc-
as much as 12–24 hours. Convincing early signs of ture and function (subjectively or quantitatively). If
radiographic improvement may occur within 12 hours, there is no atrial dilation, the cranial mediastinum
but overt decrease in respiratory effort is almost always should be imaged for presence of a mediastinal mass in
apparent earlier, and often within 1 to a few hours after cats with pleural effusion.
diuretic administration. Complete resolution of intersti- A brief thoracic ultrasound is a useful and minimally
tial or alveolar infiltrates may take 24 hours or longer. stressful diagnostic technique for evaluation of signifi-
Pleural effusion typically requires many days to resolve cant pleural effusion in the unstable dyspneic cat. It is
with diuretic treatment alone, which explains the need often a safer choice than thoracic radiographs in the
for thoracocentesis rather than diuretics in the acute unstable patient, because minimal restraint is needed for
stabilization stage when large-volume effusion is respon- the ultrasound. The cat can be maintained in sternal
sible for dyspnea. recumbency and supplemented with oxygen if it is
tolerated. The left and right sides of the thorax
Electrocardiogram should be evaluated for significant pleural effusion,
The electrocardiogram (ECG) is the diagnostic test of and the optimal location is identified for palliative tho-
choice to evaluate a cardiac arrhythmia. It is insensitive racocentesis (see Chapter 3). Thoracocentesis is an
for detection of chamber enlargement, but it is relatively immediately life-saving procedure in cats with severe
specific. Common arrhythmias in cats with heart failure pleural effusion and should be done quickly once the
include atrial fibrillation, supraventricular tachycardia, diagnosis has been made. After the cat stabilizes, a more
ventricular premature complexes, and ventricular tachy- thorough echocardiographic examination should be
cardia. In a large retrospective study of cats diagnosed done to evaluate whether the pleural effusion is cardio-
with atrial fibrillation, a large percentage of cats had genic in origin.
heart failure consisting of pleural effusion (61% of cats) Evaluation of pericardial effusion should also be done
or pulmonary edema (22%). Cats with heart failure may on a triage basis in cats with pleural effusion and/or
have sinus tachycardia due to increased sympathetic ascites. Although it is uncommon for cats to develop
tone. However, presence of sinus tachycardia does not moderate to severe pericardial effusion and cardiac tam-
discriminate between cats with heart failure and asymp- ponade, mild pericardial effusion not requiring pericar-