These are papers from the July 2011 St. Louis AVMA conference. I’ve edited them to delete some of the vet only jargon and for space considerations. If you see (…) that means that information has been deleted due to these considerations. The ones listed here include HCM, and other heart related papers, treatments, papers on x-rays and echos, thrombosis, kidney disease, idiopathic cystitis, pain management, anesthesia and cardiac disease, supplements and other hazards for pets, and some other basic information I hope is helpful.
THE COUGHING AND DYSPNEIC DOG AND CAT
Philip R. Fox DVM, Dipl. ACVIM/DECVIM (Cardiology), Dipl. ACVECC
The Animal Medical Center
Philip.fox@amcny.org Tel: 1 212 329 8606
CLINICAL OVERVIEW
Because a broad range of conditions cause or contribute to coughing and dyspnea, diagnosis
and therapy is optimized by an insightful medical history, complete physical examination,
clinical pathology tests, and diagnostic imaging (radiography, echocardiography, CT, MRI)c
findings,. Clients may confuse coughing with gagging, wheezing, labored breathing, and
reverse sneezing. Some dogs retch or vomit after coughing, and this is often misinterpreted as
gastrointestinal origin. Naso-pharyngeal diseases often induce gagging which can simulate a
cough, although these cases may also exhibit nasal discharge, sneezing and snorting,
ptyalism, or strider. Laryngeal diseases may result in gagging, strider and sometimes
coughing.
…The coughing reflex may be initiated throughout the upper and lower respiratory system (pharynx, larynx,
tracheobronchial tree, and small airways). In some animals coughing occurs just occasionally
and is of no clinical significance; in others, coughing affects quality of life (both to the animal
and the owner), or is a harbinger of serious underlying disease. Most coughs sound alike and
more than one etiology may coexist.
Dyspnea or respiratory distress refers to difficult or labored breathing. Severity may be judged
by assessing breathing effort, respiratory rate, rhythm, and character. Affected animals display
a standing or sitting posture (cats rest on their sternum), with neck extended and elbows
adducted. Tachypnea (polypnea) relates to an increased breathing rate, which may or may not
be associated with a dyspnea.
COMMON CAUSES OF COUGHING AND DYSPNEA
One should consider general disease categories associated with respiratory distress:
congestive heart failure (eg, volume overload, hypertrophic and dilated cardiomyopathy),
pleural space disease (eg, fluid, air, organs), upper airway disease (eg, nasopharynx;
collapsed trachea; foreign bodies), lower airway disease (eg, bronchitis, ‘asthma’), and
parenchymal lung disease (eg, pneumonia, parasites, neoplasia), and others.
Common etiologies for acute dyspnea include trauma, pulmonary edema, pneumonia, airway
obstruction, pneumothorax, and pulmonary thromboembolism. Chronic dyspnea can occur
from right-sided CHF, pulmonary hypertension, pericardial tamponade, broncho-interstitial
disease, pleural effusions, anemia, neoplasia, hernia, and other causes. Inspiratory dyspnea
suggests upper airway obstruction while expiratory dyspnea suggests lower airway
obstruction. Exertional dyspnea may imply organic disease (e.g., myocardial failure, dilated
cardiomyopathy), chronic obstructive lung disease, other parenchymal conditions, or
neuromuscular or musculoskeletal disorders. Paroxysmal dyspnea suggests brady or
tachyarrhythmias, especially with episodic weakness or syncope. Resolved dyspnea following
cardiac drug therapy suggests heart disease…Cats with cardiogenic pulmonary edema rarely cough (even when severe left atrial enlargement is present), but frequently cough with bronchitis, asthma, heart-worm, lungworms, neoplasia, and foreign bodies.
THORACIC IMAGING
Diagnostic imaging is a rapidly evolving field that requires familiarity with the appearances of
cardiovascular and respiratory diseases on chest radiographs, as well as images obtained with
computed tomography, magnetic resonance imaging, echocardiography, and angiography.
The thoracic radiograph provides information about thoracic musculoskeletal conformation and
disease, cardiac size and shape, pulmonary parenchymal and vascular disorders, and
conditions involving the pleura, mediastinum, esophagus, and diaphragm. Radiographs help
confirm or exclude clinical impressions, support or reject specific diagnoses, and provide
important information not otherwise suspected. They help to screen for cardiopulmonary,
systemic, and metabolic disorders and assist to formulate initial treatments…
ECHOCARDIOGRAPHY and DOPPLER ECHOCARDIOGRAPHY
Echocardiography is a rapid, noninvasive, and accurate technique with high utility to evaluate
cardiac structure and function. Tissue interfaces are enhanced by fluid and therefore, this is
particularly suited to assess the heart in the presence of pleural and pericardial effusionconditions
that limit radiographic assessment…Echocardiographic techniques provide additional information
about cardiac function. Air interferes with tissue interface, and echocardiographic examination
is limited with pneumothorax or in some animals with chronic airway disease.
CT IMAGING
CT scanning—sometimes called CAT scanning, is used to further examine abnormalities
found on conventional radiography, help diagnose the cause of clinical signs or symptoms of
disease of the chest, detect and evaluate the extent of primary or metastatic chest tumors,
assess whether neoplasia is responding to treatment, help plan radiation therapy, evaluate
injury to the chest, including the blood vessels, lungs, ribs and spine. Chest CT can
demonstrate various lung disorders, such as: lung cancer , old or new pneumonia,
emphysema, bronchiectasis, inflammation or other pleural diseases, and diffuse interstitial lung
disease. A CT angiogram (CTA) may be performed to evaluate arteries and veins as well as
cardiac structures. This involves the rapid injection of an iodine contrast material while
obtaining numerous, thinner CT images. Three-dimensional reconstruction of cardiac and
pulmonary structures using a workstation connected to a chest computed tomography (CT)
scanner may change the diagnostic strategy in patients with congenital or acquired thoracic
disease as well as chest trauma. CT is capable of identifying thickened, calcified and
congenitally absent pericardium, intracavitary masses, and is particularly useful to detect
extracardiac and pulmonary masses when pleural effusion is present. The advantage of CT
over MRI is shorter anesthesia time, and resolution of pulmonary masses that is less liable to
motion artifact associated with MRI.
MRI IMAGING
MR imaging uses a magnetic field, radio frequency pulses and a computer to produce detailed
images of organs, soft tissues, bone and virtually all other internal structures. MRI does not
use ionizing radiation. It is selected to assess masses including pulmonary neoplasia or other
tissues, which either cannot be assessed adequately with other imaging modalities (typically
CT) or which are particularly well-suited to MR imaging. Additional applications include
determine tumor size, extent, and the degree of metastasis, assess cardiac anatomy and
function and its component structures (valves, etc.), determine blood flow dynamics in the
vessels and heart chambers, display lymph nodes and blood vessels, including vascular and
lymphatic malformations of the chest, assess extracardiac disorders of the chest (vertebrae,
ribs and sternum). Chest wall lesions include a diverse group of soft tissue and osseous
thoracic diseases. MR imaging, with its superior tissue-resolving capability and multiplanar
image acquisition, is an important tool for evaluating these lesions. A special form of MRImagnetic
resonance angiography (MRA) is helpful to assess vasculature. Disadvantages of
MRI include its requirement for longer anesthesia time vs CT, challenges in cardiac monitoring,
and special equipment needed for cardiac gating.
THORACIC RADIOGRAPHY
Good quality chest films are essential for accurate diagnosis and effective management. Both
coughing and dyspnea may result from cardiac or respiratory disorders, as well as
inflammation, neoplasia, parasitic diseases, trauma, degenerative disorders, physical causes,
and allergic states. Dyspnea or respiratory distress refers to difficult or labored breathing.
Severity may be judged by assessing breathing effort, respiratory rate, rhythm, and character.
Affected animals display a standing or sitting posture (cats rest on their sternum), with neck
extended and elbows adducted. Tachypnea (polypnea) relates to an increased breathing rate,
which may or may not be associated with a dyspnea. Cough reflex may be initiated throughout
the upper and lower respiratory system (i.e., pharynx, larynx, tracheobronchial tree, and small
airways). Most coughs sound alike. Coughing may be occasional and of no clinical
significance, or persistent , fatiguing (both to the animal and the owner), and a harbinger of
serious disease. Clients may confuse coughing with gagging, wheezing, labored breathing,
and reverse sneezing. Some dogs retch or vomit after coughing, and this is often
misinterpreted as gastrointestinal disease. Naso-pharyngeal diseases often induce gagging
which can simulate a cough, although these cases may also exhibit nasal discharge, sneezing
and snorting, ptyalism, or strider. Laryngeal diseases may result in gagging, strider and
sometimes coughing. Certain generalizations have been made about the character of the
cough: tracheal disease may cause dry, honking, resonant cough (dogs) and dyspnea or
strider (cats); bronchiolar disease may cause coughing that is often followed by retching;
alveolar disease may cause mild cough with dyspnea, or a moist cough with gagging and
expiration of frothy fluid (pulmonary edema). Cats rarely cough from pulmonary edema but do
from bronchitis, asthma, heart-worm, lungworms, neoplasia, and foreign bodies. In dogs,
coughing commonly results from heart failure- particularly pulmonary edema; impingement on
the main stem bronchi by severe left heart enlargement; heart worm disease, large airway
disease; tracheobronchitis, and pulmonary fibrosis. In cats, feline bronchial disease (including
‘asthma’) is the most common cause for coughing…
RADIOGRAPHIC INTERPRETATION
Thoracic Wall The chest wall includes the spine, ribs, sternum and related soft tissues, and is
framed by the caudal cervical vertebrae cranially, and diaphragm caudally. Evaluate symmetry
in both views (altered by pectus excavatum, scoliosis, trauma). Look for lytic lesions indicative
of neoplasia or infection, fractures (trauma), masses, changes in opacity, and subcutaneous
emphysema. Some chest wall lesions may intrude into the thoracic cavity and exhibit
extrapleural signs.
The Mediastinum These are potential spaces between cranial and caudal pleural cavities. In
the cranial mediastinum lie the heart, ascending aorta, main pulmonary artery, cranial vena
cava, thoracic duct, nerves, trachea, esophagus, lymph nodes, and thymus. In the caudal
mediastinum are the posterior vena cava, trachea, descending aorta, nerves, and lymph
nodes…
Heart and Great Vessels In the lateral canine view, the heart is oriented at approximately a
45 degree angle, is situated between the 3rd-8th thoracic vertebrae, occupies about 3
intercostal spaces, and measures about 8.5-10.6 (average, 9.7) vertebral bodies (T4) wide
using the vertebral heart score method. In the VD or DV view it has a roughly elliptical shape
with a curved right ventricular and relatively straight left ventricular border. Breeds often
influence anatomic contours. Anatomical structures include (clockwise); aortic arch (extending
from 11 to 1 o'clock); main pulmonary artery segment (1 to 2 o'clock); left auricular appendage
(2 to 3 o’clock); left ventricle (2 to 6 o'clock), and right heart (6 to 12 o’clock). In the right lateral
view, the left atrium is superimposed over the caudal-dorsal one-third of the heart just distal to
the tracheal bifurcation. When significantly enlarged, the left atrium may compress main stem
bronchi and contribute to coughing in dogs. In the lateral feline view, the heart is oval and
narrower than the dog (2.5 to 3 intercostal spaces wide), varies from vertical to nearly
horizontal, and is separated from the diaphragm by 1 or 2 intercostal spaces.
Abnormalities in Cardiac Size and Shape Conformation, respiration, hydration, stage of
cardiac cycle, positioning errors and effusions alter radiographic appearances. Pleural
effusions may obscure the cardiac silhouette. Cardiomegaly usually results from congenital or
acquired lesions causing volume overload (e.g. valvular insufficiency or shunts), pressure
overload (e.g., valvular stenosis), myocardial disease (e.g., cardiomyopathy), pericardial
disease, or respiratory conditions (e.g., cor-pulmonale). The cardiothoracic distance decreases
in the DV or VD view but this can also be influenced by phase of respiration and pleural
disease. Cardiac function cannot be directly assessed by radiography…
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