Resiliencia y otros terrenos de resistencia

m oaRa a ssis c Rivelente *

3. Resiliencia y otros terrenos de resistencia

(A TYPE OF HEART-MUSCLE DISEASE)

BASICS

OVERVIEW

T he heart of the cat is composed of four chambers; the top two chambers are the left and right atria and the bottom two chambers are the left and right ventricles; heart valves are located between the left atrium and the left ventricle (mitral valve); between the right atrium and the right ventricle (tricuspid valve); from the left ventricle to the aorta (the main artery of the body; valve is the aortic valve); and from the right ventricle to the main pulmonary (lung) artery (pulmonary valve)

“ Cardiomyopathy” is the medical term for disease of the heart muscle; “ restrictive cardiomyopathy” is a disease in which the muscle is “ stiff” and does not expand, such that blood cannot fill the ventricles normally

“ Restrictive cardiomyopathy” in cats is characterized by abnormal filling of the chambers of the heart (known as “ diastolic

dysfunction”), severe atrial enlargement, normal left ventricular wall thickness and variable abnormal pumping of the heart (known as “ systolic dysfunction”)

Scar tissue of the heart muscle layer may be present; in addition, other changes or damage in the muscle may be associated with other heart-muscle disorders, including inflammatory or immune-mediated diseases

SIGNALM ENT/DESCRIPTION of ANIM AL Species

Cats

SIGNS/OBSERVED CHANGES in the ANIM AL

If Ca t Does Not Ha ve Congestive Hea rt Fa ilure (condition in which the hea rt ca nnot pump a n a dequa te volume of blood to meet the body’s needs)

Some cats have no clinical signs

Sluggishness (lethargy)

P oor appetite and weight loss

Fainting (known as “ syncope”)—rare; usually indicates serious irregular heart beats (known as “ arrhythmias”)

Weakness or paralysis (signs of blockage of blood flow secondary to the presence of a blood clot in the artery [condition known as “ arterial thromboembolism”])

Depression

Extreme weight loss with muscle wasting (known as “ cachexia”)

Rapid heart rate (known as “ tachycardia”)

Irregular heart beats (arrhythmias)

Sequence of three heart sounds (known as a “ gallop rhythm”), when listening to the heart with a stethoscope; heart beat sounds like a galloping horse instead of normal “ lub-dub”

May have a heart murmur

If Ca t Ha s Congestive Hea rt Fa ilure (condition in which the hea rt ca nnot pump a n a dequa te volume of blood to meet the body’s needs), ca t ha s signs a s previously described, plus the following:

Difficulty breathing (known as “ dyspnea”)

Rapid breathing (known as “ tachypnea”)

P anting

Open-mouth breathing

Bluish discoloration of the skin and moist tissues (known as “ mucous membranes”) of the body caused by inadequate oxygen levels in the red-blood cells (known as “ cyanosis”)

Abdominal swelling or distention

Enlarged liver (known as “ hepatomegaly”) or fluid build-up in the abdomen (known as “ ascites”), with enlargement or distension of the jugular veins (located on either side of the neck)

Short, rough snapping sounds (known as “ crackles”) heard when listening to the chest with a stethoscope

Muffled heart or lung sounds heard when listening to the chest with a stethoscope, if the cat has fluid build-up in the space between the chest wall and lungs (known as “ pleural effusion”)

Weakness or paralysis with loss of femoral pulses; one or more extremities may be cold and painful (signs of blockage of blood flow secondary to the presence of a blood clot in the artery [condition is “ arterial thromboembolism”])

CAUSES AND RISK FACTORS

T rue cause(s) unknown (so called “ idiopathic disease”); often no “ predisposing” disease can be documented

Suspected initiating causes include inflammation of the heart muscle (known as “ myocarditis”); inflammation of the inner muscle layer of the heart (known as “ endomyocarditis”); infiltration of eosinophils (a type of white-blood cell) into the heart muscle (known as “ eosinophilic myocardial infiltration”); disease characterized by inappropriate enlargement or thickening of the heart muscle of the left ventricle (known as “ hypertrophic cardiomyopathy”) with sudden lack of blood supply to the heart muscle that leads to death of tissues (known as “ myocardial infarction”); widespread (diffuse) “ small blood vessel disease;” and other causes of abnormal blood flow and resulting lack of oxygen to the heart muscle

TREATMENT

HEALTH CARE

P atients with sudden (acute), severe congestive heart failure are hospitalized for emergency care; “ congestive heart failure” is a condition in which the heart cannot pump an adequate volume of blood to meet the body’s needs

Animals that do not have clinical signs or have mild signs can be treated with outpatient medical management

Animals with severe difficulty breathing (severe dyspnea) should receive oxygen via oxygen cage, nasal cannula, or mask (beware of stress to patient)

Life-threatening fluid build-up in the space between the chest wall and lungs (pleural effusion) is reduced via tapping and draining the chest (known as “ thoracocentesis”)

T reat associated conditions (such as dehydration or low body temperature [hypothermia])

Low sodium fluids administered cautiously if dehydration occurs (beware of worsening congestive heart failure)

Heating pad may be necessary for patients with low body temperature (hypothermia)

ACTIVITY

Maintain a low stress environment to decrease patient anxiety (such as cage rest, minimize handling)

DIET

Low-salt diet may decrease fluid retention, but strict adherence to dietary changes should be avoided in sudden (acute) congestive heart failure in order to maintain food intake

Hand feed, as necessary

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.

Sudden (Acute) Congestive Hea rt Fa ilure (condition in which the hea rt ca nnot pump a n a dequa te volume of blood to meet the body’s needs)

Medication to remove excess fluid from the body (diuretic) administered by injection—furosemide

Dobutamine (drug to increase contraction of the heart muscle) to increase function of the heart

Nitroglycerin ointment, applied to the skin

Oxygen delivered by cage, mask, or nasal tube

T apping and draining the chest (thoracocentesis), as necessary to relieve difficulty breathing (dyspnea) due to fluid build-up in the space between the chest wall and lungs (pleural effusion)

Severe irregular heart beats originating above the ventricles (supraventricular arrhythmias) may be treated with diltiazem

Rapid ventricular heart rate (ventricular tachycardia) may resolve with resolution of congestive heart failure; treatment for sudden occurrence of ventricular tachycardia may include lidocaine

Beta-blockers (such as propranolol or atenolol) may be used to treat irregular heart beats that originate above or in the ventricles (supraventricular or ventricular arrhythmias), but not until congestive heart failure is treated

Long-Term (Chronic) Thera py

Medication to remove excess fluid from the body (diuretic)—furosemide, gradually decreased to lowest effective dose

Long-term (chronic) therapy with diltiazem decreases heart rate and improves irregular heart beats that originate above the ventricles (supraventricular arrhythmias) and may improve heart function

Beta-blockers may be used to slow heart rate and treat irregular heart beats that originate above or in the ventricles (supraventricular or ventricular arrhythmias)

Angiotensin-converting enzyme (ACE) inhibitors may reduce fluid retention and decrease need for medications to remove excess fluid from the body (diuretics); examples of ACE inhibitors are enalapril and benazepril

Digoxin (a heart medication) may be used if heart-muscle contraction is impaired or atrial fibrillation (rapid, irregular heart rhythm involving the top two chambers of the heart [atria]) is present

Aspirin may be administered to prevent blood clots (known as “ thromboembolism”), but effectiveness is questionable; administer aspirin only under the direction of your cat’s veterinarian

Warfarin may be administered to prevent blood clots (thromboembolism), but is not recommended unless close monitoring and repeated measurement of prothrombin time (a blood test to evaluate clotting) are feasible

FOLLOW-UP CARE

PATIENT M ONITORING

Frequent serial physical examinations (minimal stress to patient) to assess response to treatment and resolution of fluid build-up in the lungs (pulmonary edema) and fluid build-up in body cavities (known as “ effusions”)

Frequent assessment of hydration and kidney function is important in first few days of therapy to avoid removal of too much fluid from the body (known as “ over diuresis”) and development of excessive levels of urea and other nitrogenous waste products in the blood (known as “ uremia” or “ azotemia”)

Repeated tapping and draining the chest (thoracocentesis) may be necessary to maintain the amount of fluid build-up in the space between the chest wall and lungs (pleural effusion) at a comfortable level

“ Hands-off” hourly assessment of breathing rate in first 12 to 24 hours can be used to monitor efficacy of congestive heart failure therapy

Chest X-rays may be repeated in 12 to 24 hours

Blood work (especially creatinine and potassium) should be monitored closely during the first 3 to 5 days of therapy to detect dehydration, kidney failure, and low levels of potassium in the blood (known as “ hypokalemia”)—caused by medications to remove excess fluid from the body (diuretics); or high levels of potassium in the blood (known as “ hyperkalemia”), if angiotensin-converting enzyme (ACE) inhibitors are administered

Repeat physical examination and blood work (especially electrolyte analysis) after approximately 10 to 14 days of treatment

Electrocardiograms (“ ECGs,” recordings of the electrical activity of the heart) and X-rays may be repeated, as your cat’s veterinarian feels necessary

Stable patients are reevaluated every 2 to 4 months, or more frequently if problems occur

POSSIBLE COM PLICATIONS

Congestive heart failure

Death

EXPECTED COURSE AND PROGNOSIS

Highly variable, based on presentation of disease and clinical signs

Most cats with restrictive cardiomyopathy and congestive heart failure live 3 to 12 months; some live 2 years

KEY POINTS

“ Restrictive cardiomyopathy” is a disease in which the heart muscle is “ stiff” and does not expand, such that blood cannot fill the ventricles normally

Animals that do not have clinical signs or have mild signs can be treated with outpatient medical management

Most cats with restrictive cardiomyopathy and congestive heart failure live 3 to 12 months; some live 2 years

CATARACTS

BASICS

OVERVIEW

Opacity in the lens; the lens is the normally clear structure directly behind the iris (the colored part of the eye) that focuses light as it moves toward the back part of the eye (retina); if opacity is complete, it prevents passage of light to the back part of the eye (retina), leading to blindness in the affected eye

“ Cataract”—may refer to a lens that is entirely opaque or to a localized opacity within the lens; does not imply cause

GENETICS

Most cataracts are inherited

Most common mode of inheritance—simple autosomal recessive

Some breeds—dominantly inherited

SIGNALM ENT/DESCRIPTION of ANIM AL Species

Dogs and cats Breed Predilection

Many dog breeds are affected by hereditary cataracts

Cataracts that typically progress to blindness are found in miniature poodles; American cocker spaniels; miniature schnauzers

Other commonly affected dog breeds—golden retrievers; Boston terriers; Siberian huskies

Cats—P ersians; Birmans; Himalayans M ea n Age a nd Ra nge

Depend on cause

Hereditary (dogs)—may be congenital (present at birth); may develop later in life (known as “ acquired cataracts”) anytime from several months to many years of age, depending on the breed

Hereditary (cats)—all reported to date have been congenital (present at birth)

SIGNS/OBSERVED CHANGES in the ANIM AL

Opacity of the lens

Related to the degree of vision impairment

Occupy less than 30% of the lens or affect only one eye—often go unnoticed

Occupy more than 60% of the lens—usually noticed and reported to the veterinarian

Cataract caused by diabetes mellitus (sugar diabetes)—may see signs of diabetes, such as increased urination (known as “ polyuria”), increased thirst (known as “ polydipsia”), and weight loss

Cloudiness in the eye (specifically the lens) noticed before vision impairment—usually related to sclerosis, rather than cataract formation; “ sclerosis” is a normal aging change in the lens due to changes in the lens fibers, it apparently has little to no effect on vision

Associated deterioration of the back of the eye (retina; condition known as “ progressive retinal degeneration”) in dogs—difficulty seeing in dimly lighted conditions (known as “ nyctalopia” or “ night blindness”)

May be associated with inflammation of the front part of the eye, including the iris (known as “ anterior uveitis”)—typically see cloudiness of aqueous humor (the “ aqueous humor” is the transparent liquid that fills the front part of the eyeball) due to increased protein content and suspended cellular debris (condition known as “ aqueous flare”); scar tissue between the iris and the lens of the eye (known as “ synechiae”); and decreased pressure within the eye (known as “ low intraocular pressure”)

CAUSES

Heredity

Diabetes mellitus (sugar diabetes)

Spontaneous—age-related

Advanced deterioration of the back of the eye (retinal degeneration)—response to toxic dialdehydes (type of chemical, used in disinfectants and leather tanning products)

Inflammation of the front part of the eye, including the iris (anterior uveitis)—secondary to formation of scar tissue between the iris and the lens of the eye (synechia) or altered aqueous humor (the transparent liquid that fills the front part of the eyeball) composition

T oxic substances—dinitrophenol; naphthalene

Nutrition—milk-replacer diet

Low levels of calcium in the blood (known as “ hypocalcemia”)

Radiation

Electric shock

RISK FACTORS

Genetics

Multiple congenital (present at birth) eye defects

Any disease capable of causing inflammation of the front of the eye, including the iris (anterior uveitis)

Advanced deterioration of the back of the eye (retinal degeneration)

Generalized (systemic) metabolic diseases—diabetes; diseases capable of causing low levels of calcium in the blood (hypocalcemia)

TREATMENT

HEALTH CARE

Dogs undergoing cataract surgery—inpatient or outpatient

Hospitalization—rarely required for more than 48 hours

SURGERY

P hacoemulsification is a surgical procedure in which ultrasonic vibrations are used to fragment and liquefy the lens, in order to remove the lens material; procedure of choice

P rognosis for successful surgery—generally greater than 90%; depends on the stage of the cataract and other possible abnormalities in the eye

Intraocular lenses—may be implanted safely at the time of surgery, so patient will not suffer extreme farsightedness

MEDICATIONS

P rednisolone acetate (1%) to prevent and control lens-induced inflammation of the front part of the eye, including the iris (anterior uveitis)

OcluVet™ Eye Drops recently have been marketed with claims that topical application (that is, applied to the eye) reduces lens opacification in dogs; preliminary reports from veterinary eye doctors (ophthalmologists) do not support the claim of effectiveness—

further studies need to be performed

FOLLOW-UP CARE

PATIENT M ONITORING

All patients—monitor carefully for progression of cataracts

Hereditary—cataracts may progress very quickly in young dogs

PREVENTIONS AND AVOIDANCE

Do not breed patients with known or suspected inherited conditions

POSSIBLE COM PLICATIONS

Complete cataracts—potential to cause lens-induced inflammation of the front part of the eye, including the iris (anterior uveitis);

secondary glaucoma (in which the pressure within the eye [intraocular pressure] is increased secondary to inflammation in the front part of the eye); and the separation of the back part of the eye (retina) from the underlying, vascular part of the eyeball (known as the “ choroid;” condition known as “ retinal detachment”)

EXPECTED COURSE AND PROGNOSIS

Rate of progression—depends on location of cataract within the lens and the patient’s age

Diabetes mellitus–induced cataract—usually very rapid progression

Surgical intervention—for hereditary or diabetes-caused cataracts, prognosis for good vision excellent; for other types of cataracts, depends on cause

KEY POINTS

Surgery normally can be done on any hereditary cataract that is causing or is anticipated to cause vision loss

P rognosis for surgery is better if it is done early in the course of cataract development, before the cataract changes to the point where the lens is smaller and may actually “ clear” to some degree (known as “ hypermaturity” of the cataract), lens-induced inflammation of the front part of the eye, including the iris (anterior uveitis), and/or separation of the back part of the eye (retina) from the underlying, vascular part of the eyeball (retinal detachment) occur

It is not advisable to delay surgery until the patient is blind in both eyes

Surgery may or may not be indicated for nonhereditary cataracts; discuss surgery with your pet’s veterinarian

With the high success rate of phacoemulsification (surgical procedure in which ultrasonic vibrations are used to fragment and liquefy the lens, in order to remove the lens material), it is no longer appropriate to observe cataracts for possible resorption, even in young dogs

DISEASE CAUSED BY CHLAMYDOPHILA, A TYPE OF

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