K eywoRds
6. Dimensión local e internacional
(BLOOD CLOTS IN THE AORTA)
BASICS
OVERVIEW
“ Aortic” refers to the aorta, the main artery of the body; “ thromboembolism” is blockage of blood flow secondary to the presence of a blood clot in an artery
“ Aortic thromboembolism” results from a blood clot (known as a “ thrombus”) that is dislodged within the aorta, causing severely reduced blood flow to the tissues receiving blood from that particular part of the aorta, leading to decreased oxygen in the tissues (reduced blood flow leading to decreased oxygen in the tissues is known as “ ischemia”)
T he heart of the dog or cat is composed of four chambers; the top two chambers are the right and left atria and the bottom two chambers are the right and left ventricles
GENETICS
Although aortic thromboembolism is not commonly thought of as an inherited disease, a commonly associated disease, “ hypertrophic cardiomyopathy” (a disease characterized by inappropriate enlargement or thickening of the heart muscle of the left ventricle) likely is inherited
A family of domestic shorthair (DSH) cats with hypertrophic cardiomyopathy recently were reported to have died from aortic thromboembolism
SIGNALM ENT/DESCRIPTION of ANIM AL Species
Cats, rarely dogs Breed Predilections
Mixed-breed cats most commonly are affected
Abyssinian, Birman and ragdoll purebred cats were reported in one study to have a higher number of cases than would be expected normally
M ea n Age a nd Ra nge
Mean age is approximately 8 years
Age range is 1 to 20 years Predomina nt Sex
Males are affected twice as frequently as females
SIGNS/OBSERVED CHANGES in the ANIM AL
Sudden (acute) onset paralysis and pain are the most common clinical signs
Weakness or paralysis of the rear legs; occasionally weakness of a front leg
Lameness or gait abnormality
Rapid breathing (known as “ tachypnea”) or breathing distress is common
Difficulty breathing (known as “ dyspnea”)
Vocalization and anxiety
Vomiting
Absent or diminished femoral pulses
Bluish or pale nail beds and foot pads
Low body temperature (known as “ hypothermia”) is common
Heart murmur, irregular heart beats (known as “ arrhythmias”) or gallop sound (sequence of three heart sounds heard when listening to the heart with a stethoscope; heart beat sounds like a galloping horse instead of normal “ lub-dub”)
CAUSES
Heart muscle disease (known as “ cardiomyopathy”)
Increased levels of thyroid hormone in the body (known as “ hyperthyroidism”)
Cancer
Generalized bacterial infection (known as “ sepsis”) in dogs
Increased levels of steroids produced by the adrenal glands (known as “ hyperadrenocorticism” or “ Cushing’s disease”) in dogs
Disease in which proteins are lost from the body through the kidneys (known as “ protein-losing nephropathy”) in dogs
RISK FACTORS
Markedly enlarged left atrium
Blood clot within the chambers of the heart
TREATMENT
HEALTH CARE
Initially, treat cats as inpatients, because many have coexistent congestive heart failure as well as having considerable pain and distress; “ congestive heart failure” is a condition in which the heart cannot pump an adequate volume of blood to meet the body’s needs
Fluid therapy administered cautiously, as many cats are in congestive heart failure
Supplemental oxygen therapy or a medical procedure to tap the chest (known as “ thoracocentesis”) may be beneficial, if pet is in congestive heart failure
Initially, the affected legs should be handled minimally; however, as blood flow returns, physical therapy (passive extension and flexion of the legs) may speed full recovery
Initially, these cats may have difficulty posturing to urinate and may need to have their bladders expressed to prevent over-distention or development of skin lesions due to contact with urine, when the hair and skin remain damp (known as “ urine scald”)
ACTIVITY
Activity should be restricted
Keep the cat quiet and stress-free
DIET
Initially, most cats have lack of appetite (known as “ anorexia”)
T empt these cats with any type of food
It is important to keep these cats eating to avoid hepatic lipidosis (a disease in which fats and lipids [compounds that contain fats or oils] accumulate in the liver)
SURGERY
Surgical removal of the blood clot typically is not recommended as these are high-risk patients because of severe heart disease
MEDICATIONS
Medications presented in this section are intended to provide general information about possible treatment. T he treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive.
Medications to break up existing clots (known as “ thrombolytic drugs,” such as urokinase, streptokinase or tissue plasminogen activator) are used extensively in people and infrequently in cats; these drugs are expensive and carry a significant risk for bleeding complications and thus rarely are used in general veterinary practice
Heparin is the preferred drug in general practice; it has no effect on the established clot; however, it prevents further clotting
Aspirin theoretically is beneficial during and after an episode of aortic thromboembolism because of its antiplatelet effects; “ platelets”
are normal cell fragments that originate in the bone marrow and travel in the blood as it circulates through the body; platelets act to “ plug” tears in the blood vessels and to stop bleeding; if they accumulate in a blood vessel, they may lead to a blood clot (known as “ thrombosis”)—aspirin should be administered only under the direction of your pet’s veterinarian
Clopidogrel, an anti-platelet aggregation drug, has some promise for management and prevention of future aortic thromboembolism
Buprenorphine is an opiate used to relieve pain (known as “ analgesia”) and to sedate the pet; for stronger analgesia, fentanyl or hydromorphone could be used
Acepromazine may be used cautiously for its sedative effects and to dilate blood vessels (known as “ vasodilation”)
Warfarin, a vitamin-K antagonist, is a medication that decreases blood clotting (known as an “ anticoagulant”); it is used most widely in people and has been proposed for prevention of re-embolization in cats surviving an initial episode—long-term management with warfarin can be challenging because of the necessity for frequent monitoring and dose adjustments as well as side effects, such as bleeding
Low molecular-weight heparin (LMWH) recently has been proposed for the long-term prevention of feline aortic thromboembolism;
LMWH has a more predictable relationship between dose and response than warfarin and does not need frequent monitoring or dose adjustments; it also has a lower risk of bleeding complications than warfarin
T reat the patient’s heart disease; medications determined by type and severity of heart disease
FOLLOW-UP CARE
PATIENT M ONITORING
Electrocardiogram (“ ECG,” a recording of the electrical activity of the heart) monitoring is helpful to detect heart problems with
re-establishment of blood flow (known as “ re-perfusion injury”) and high levels of potassium in the blood (known as “ hyperkalemia”)
Monitoring blood work (electrolytes and kidney tests) periodically may be helpful to improve management of the heart disease
Examine the legs daily to assess clinical response
Blood-clotting tests (such as “ activated partial thromboplastin time [AP T T ], prothrombin time [P T ]) should be performed; decision upon which clotting test is performed and frequency of testing is determined by medication (such as heparin or warfarin) that pet is receiving
PREVENTIONS AND AVOIDANCE
P revention of future blood clots in the aorta with long-term (chronic) administration of aspirin, clopidogrel, warfarin, or LMWH is recommended strongly because of the high rate of blood-clot formation
POSSIBLE COM PLICATIONS
Bleeding with medications to prevent blood clotting (anticoagulant therapy)
P ermanent nervous system deficits or muscular abnormalities in the hind legs
Recurrent congestive heart failure; “ congestive heart failure” is a condition in which the heart cannot pump an adequate volume of blood to meet the body’s needs
Sudden death
EXPECTED COURSE AND PROGNOSIS
Expected course is days to weeks for full recovery of function to the legs
P rognosis in general is poor—in two studies, approximately 60% of cats were euthanized or died during the initial episode of aortic thromboembolism
Long-term prognosis varies between 2 months to several years; however, the average is approximately a few months with treatment
P redictors of poorer prognosis include low body temperature (hypothermia; less than 99o F), and congestive heart failure; “ congestive heart failure” is a condition in which the heart cannot pump an adequate volume of blood to meet the body’s needs
P redictors of better prognosis include normal body temperature (known as “ normothermia”), only a single leg affected and presence of ability to move the leg on initial examination
Recurrence of aortic thromboembolism is common
KEY POINTS
Be aware of the poor short- and long-term prognosis
Most cats will develop future blood clots
Most cats that survive the initial episode will recover complete function of their affected legs; however, if decreased blood flow and lack of oxygen to the tissues (ischemia) was severe and prolonged, sloughing of parts of the lower legs or persistent nervous system deficits may result
Most cats that survive the initial episode will be on some type of medication to prevent blood clotting (anticoagulant therapy) and may require frequent reevaluations and an indoor lifestyle
ARTHRITIS (OSTEOARTHRITIS)
BASICS
OVERVIEW
“ Arthritis” is the medical term for inflammation of the joints; “ osteoarthritis” is a form of joint inflammation (arthritis) characterized by long-term (chronic) deterioration or degeneration of the joint cartilage
P rogressive and permanent deterioration of joint cartilage
Also known as “ degenerative joint disease” or “ DJD”
GENETICS
P rimary degenerative joint disease (progressive and permanent deterioration of joint cartilage) is rare—once associated with a colony of beagles
Dogs—causes of secondary degenerative joint disease (progressive and permanent deterioration of joint cartilage) are varied, including abnormal development of the hip (known as “ hip dysplasia”) or elbow (known as “ elbow dysplasia”); abnormal development of bone and cartilage, leading to a flap of cartilage within the joint (known as “ osteochondritis dissecans” or “ OCD”); dislocation of the knee cap (known as a “ patellar luxation”); congenital (present at birth) shoulder dislocation (known as a “ shoulder luxation”); noninflammatory death of tissue (known as “ necrosis”) involving the femoral head (the “ ball” of the hip joint) with collapse of the bone (condition known as “ Legg-Calvé-P erthes disease”); and cranial cruciate ligament rupture of the stifle or knee
Cats—causes of secondary degenerative joint disease (progressive and permanent deterioration of joint cartilage) are dislocation of the knee cap (patellar luxation), abnormal development of the hip (hip dysplasia), and any joint disease (known as an “ arthropathy”)
SIGNALM ENT/DESCRIPTION of ANIM AL Species
Dogs and cats
M ea n Age a nd Ra nge
Secondary degenerative joint disease (progressive and permanent deterioration of joint cartilage) due to congenital (present at birth) disorders (such as hip dysplasia) seen in immature animals; some present with DJD signs when older (such as cases of hip or elbow dysplasia)
Secondary to trauma—any age
SIGNS/OBSERVED CHANGES in the ANIM AL
Dogs—decreased activity level; unwilling to perform certain tasks; intermittent lameness or stiff gait that slowly progresses
P ossible history of joint trauma; abnormal development of bone and cartilage, leading to a flap of cartilage within the joint (osteochondritis dissecans); or developmental disorders
Lameness or abnormal gait may become worse with exercise, long periods of lying down or resting, and/or cold weather
Cats—obvious lameness may not be seen; instead, may have difficulty grooming, jumping onto furniture, or accessing the litter box;
may have increased irritability
Stiff-legged or altered gait (such as “ bunny hopping” in hip dysplasia)
Not using the affected leg(s)
Decreased range of motion
Grating detected with joint movement (known as “ crepitus”)
Joint swelling (fluid build-up in the joint [known as “ joint effusion”] and/or thickening of the joint capsule)
Joint pain
Joint instability
Obvious joint deformity
CAUSES
P rimary—no known cause (so called “ idiopathic osteoarthritis”)
Secondary—results from an initiating cause, such as abnormal wear on normal cartilage (examples, secondary to joint instability, abnormal joints, trauma to cartilage or supporting soft tissues) or normal wear on abnormal cartilage (example, secondary to defects in the bone and cartilage [known as “ osteochondral defects”])
RISK FACTORS
Working, athletic, and obese dogs place more stress on their joints
Dogs with disorders that affect collagen or cartilage (such as increased levels of steroids produced by the adrenal glands [known as “ hyperadrenocorticism” or “ Cushing’s disease”], diabetes mellitus [“ sugar diabetes”], inadequate levels of thyroid hormone [known as “ hypothyroidism”], excessive looseness of the joints [known as “ hyperlaxity”], or prolonged treatment with steroids)
TREATMENT
HEALTH CARE
Medical treatment—usually tried initially
P hysical therapy—very beneficial
Maintaining or increasing joint motion—passive range of motion exercises, massage, swimming (as directed by your pet’s veterinarian)
P ain management—cold and heat therapy, as directed by your pet’s veterinarian
Muscle tone/strengthening exercises—swimming (aerobic exercise with minimal weight bearing), controlled leash walks up hills or on soft surfaces (such as sand), and dry or water treadmill
ACTIVITY
Limited to a level that minimizes aggravation of clinical signs
DIET
Weight reduction for obese patients—decreases stress placed on arthritic joints
Omega fatty acids may decrease inflammation; use as directed by your pet’s veterinarian
SURGERY
Surgical options—improve joint geometry or remove bone-on-bone contact areas
Surgical procedure cutting into or entering a joint (known as an “ arthrotomy”)—used to remove aggravating causes (such as bone and/or cartilage fragments or flaps)
Using a special lighted instrument called an “ arthroscope” (general term for procedure is “ arthroscopy”) to allow the surgeon to see inside the joint—used to diagnose and remove aggravating causes; flushing the joint may be beneficial
Reconstructive procedures—used to eliminate joint instability and correct structural or anatomic problems (such as in animals with dislocation of the knee cap [patellar luxation])
Joint removal—such as removal of the femoral head (the “ ball”) of the hip joint for cases of abnormal development of the hip (hip dysplasia; procedure known as “ femoral head and neck ostectomy” or “ FHO”)
Joint replacement—total hip replacement is common; total elbow replacement still is experimental
Joint fusion (known as “ arthrodesis”)—in selected long-term (chronic) cases and for joint instability
MEDICATIONS
Medications presented in this section are intended to provide general information about possible treatment. T he treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive.
Nonsteroidal anti-inflammatory drugs (NSAIDs) to decrease pain and inflammation—examples are carprofen, deracoxib, etodolac, meloxicam, tepoxalin
Medications intended to slow the progression of arthritic changes and protect joint cartilage (known as “ chondroprotective drugs”), such as polysulfated glycosaminoglycans, glucosamine, and chondroitin sulfate—may help limit cartilage damage and degeneration; may help alleviate pain and inflammation
Steroids—decrease inflammation; however, long-term (chronic) use may delay healing and may initiate damage to joint cartilage;
examples of steroids are prednisone administered by mouth or triamcinolone administered by injection into the joint (known as an “ intra-articular injection”)
FOLLOW-UP CARE
PATIENT M ONITORING
Clinical deterioration—indicates need to change drug selection or dosage; may indicate need for surgical intervention
PREVENTIONS AND AVOIDANCE
Early identification of conditions that may lead to osteoarthritis and prompt treatment to help reduce progression of secondary conditions
EXPECTED COURSE AND PROGNOSIS
Slow progression of disease likely
Medical or surgical treatment usually allows a good quality of life
KEY POINTS
Medical therapy is designed to control signs of osteoarthritis (known as “ palliative treatment”) and not to cure the condition
Slow progression of disease likely
Medical or surgical treatment usually allows a good quality of life
Discuss treatment options, activity level, and diet with your pet’s veterinarian