VMED 105 – FELINE MEDICINE
DISEASES AND DISORDERS OF THE FELINE CARDIOVASCULAR SYSTEM
By: Jason David Frank Cabalo
COMMON CONGENITAL CARDIOVASCULAR DISEASES
DISEASE/DISORDER &
SYNONYMS
PATHOPHYSIOLOGY,
SYSTEMS AFFECTED
ATRIAL SEPTAL DEFECTS:
PATHOPHYSIOLOGY:
characterized by incomplete
▪ Atrial septal defect allows
formation of the interatrial septum
communication between left
and communi-cation between the left
and right atria; producing
and right atrium. Acquired atrial
shunting of blood between the
septal defects can also occur from
atria.
rupture of the interatrial septum.
▪ Normally left to right shunt;
SYNONYMS: ASD,
large shunts may result in
ostiumprimum/secundum defect,
volume overload of the right
persistent
atrium and ventricle, leading
atrioventricularcanal/atrioventricular
to pulmonary overperfusion,
septal defect, endocardial cushion
pulmonary hypertension and
defect (together with ventricular
right ventricular hypertrophy.
septal defect), sinus venosus defect.
Right-sided CHF may ensue.
▪
Left-to-right atrial shunt →
overloads right atrium and
ventricle → increased right
atrial and right ventricular
pressures → overcirculation
of lungs → left atrium (and
left ventricle).
SYSTEMS AFFECTED:
SIGNALMENT &
SIGNS
Dog and cat.
Persian cats may be
more at risk for ASDs
No sex
predisposition
SIGNS:
CHF, or cyanosis;
exercise intolerance,
syncope, and
dyspnea.
Soft systolic murmur
INCIDENCE/
PREVALENCE
DIAGNOSIS, DIAGNOSTIC
PROCEDURE,
DIFFERENTIAL DIAGNOSIS
CBC/BIOCHEMISTRY/URINALYSIS Typically normal. Polycythemia with
right-to-left shunting.
DIAGNOSTIC PROCEDURES:
Electrocardiography
DIFFERENTIAL DIAGNOSIS:
Physical/radiographic: pulmonic
stenosis, tricuspid dysplasia, tetralogy
of Fallot.
TREATMENT & MEDICATION,
FOLLOW UP
MEDICAL THERAPY
• Standard treatment of
CHF—furosemide,
pimobendan, angiotensinconverting enzyme (ACE)
inhibitor).
• Treatment of polycythemia
(right-to-left shunting) if
clinically indicated.
VMED 105 – FELINE MEDICINE
VENTRICULAR SEPTAL DEFECTS: is PATHOPHYSIOLOGY:
a common feline congenital
▪ Embryological failure of
malformation. It is characterized by
development of
an opening in the ventricular septum
interventricular septum,
that occurs due to failure of the
leaving conduit between left
ventricular septum to complete
ventricle and right ventricle
formation.
→ left ventricular pressure
exceeds normal right
SYNONYMS: Interventricular septal
ventricular pressure in systole
defect, VSD
→ systolic left-to-right
shunting occurs across the
defect.
▪ Large defects in lower part of
septum (less common) →
volume overload of right
ventricle, pulmonary
circulation, left atrium and left
ventricle.
▪ Defects higher in septum
(more common) →
discharge into the pulmonary
artery → overloaded
pulmonary circulation, left
atrium and left ventricle.
Age: median, 9-12
months
Breed: domestic
short-hairs and
Maine coons
No sex
predisposition
SIGNS:
In the case of a
large L→R VSD or in
R→L VSD, the
following may be
observed:
• Exercise
intolerance
• Dyspnea,
tachypnea
• Cough (L→R)
• Cyanosis
(R→L)
• Syncope
One of the
most common
congenital
cardiac malformations in
cats,
comprising
50% of cases
with congenital
cardiac
defects in one
study.
DIAGNOSIS:
CBC/BIOCHEMISTRY/URINALYSIS:
• Results usually normal.
• Uncommon right-to-left
shunting results in
compensatory erythrocytosis.
• Patients with severe
congestive heart failure (CHF)
may have prerenal azotemia.
DIFFERENTIAL DIAGNOSIS:
Tricuspid dysplasia (TVD), subaortic
stenosis (SAS), PS, tetralogy of Fallot
(of which VSD is one component),
hypertrophic cardiomyopathy (HCM)
in cats.
DIAGNOSTIC PROCEDURE:
Thoracic Radiographs
Electrocardiogram (ECG): often
normal
Echocardiography: (confirmatory test
of choice)
TREATMENT OVERVIEW:
• Often no treatment is
required because most
VSDs are small and do not
result in volume overload
or other significant clinical
consequences.
• Treatment of large L→R
VSDs is directed at
decreasing the shunt
volume and preventing or
eliminating the signs of
CHF.
• Treatment of R→L VSDs is
directed at reducing RV
pressure and palliating the
effects of erythrocytosis.
MEDICATIONS:
DRUG(S) OF CHOICE:
Furosemide, enalapril,
pimobendan, and, in some
circumstances, digoxin
recommended for animals with
CHF.
SYSTEMS AFFECTED:
Respiratory
Cardiovascular
ATRIOVENTRICULAR VALVE
DYSPLASIA:
PATHOPHYSIOLOGY:
SPECIES
Dog and cat.
Most common
congenital
cardiac
DIFFERENTIAL DIAGNOSIS:
• Ventricular septal defect
• Aortic stenosis
MEDICATIONS:
Furosemide
Enalapril
VMED 105 – FELINE MEDICINE
A congenital malformation of the
mitral or tricuspid valve apparatus.
SYNONYMS: AVVD, TVD, MVD
Valvular malformation → valvular
incompetence → congestive heart
failure.
MITRAL DYSPLASIA:
Mitral regurgitation → left atrial
and left ventricular volume overload
→ left atrial and ventricular dilation
→ increased left atrial pressure →
pulmonary venous congestion →
pulmonary edema (left-sided CHF).
TRICUSPID DYSPLASIA:
Triscupid regurgitation → right
atrial and right ventricular overload
→ right atrial and ventricular
dilation → increased right atrial
pressure → increased central
venous pressure Central venous
pressure jugular distension and
chronic venous congestion of liver
(right-sided CHF).
ENDOCARDIAL FIBROELASTOSIS
is a rare cardiac disease defined as
diffuse thickening of the left
ventricular endocardium secondary
to proliferation of fibrous and
elastic tissue
SYSTEMS AFFECTED:
Cardiovascular
Respiratory
Neurologic
PATHOPHYSIOLOGY:
Excessive fibroblast proliferation
occurs in the left ventricular
endocardium, which produces
collagen and elastin fibers. Marked
lymphatic dilation and accumulation
of edema within the endocardium are
BREED
PREDILECTIONS
TVD—common in
cats.
MVD— Siamese cat.
MEAN AGE AND
RANGE: few years
after birth.
abnormality in
the cat (17%
of congenital
heart lesions).
•
•
•
Atrial septal defect
Pulmonic stenosis.
Tetralogy of Fallot
Digoxin
Diltiazem
Beta blockers such as atenolol
DIAGNOSTIC PROCEDURE:
Radiography
Electrocardiography
PREDOMINANT SEX:
Males
SIGNS:
Exercise intolerance,
Abdominal
distention, weight
loss, and stunting
(TVD), Labored
respiration (MVD)
Syncope
SPECIES
dogs and cats
BREED
PREDILECTIONS
• Siamese,
Burmese, and
DIAGNOSIS:
The diagnosis is primarily based on
pathology findings
DIFFERENTIAL DIAGNOSIS:
Mitral valve dysplasia,
Ventricular septal defect
TREATMENT:
There is no specific treatment for
endocardial fibroelastosis.
Therapy consists of treating
congestive heart
failure when present
VMED 105 – FELINE MEDICINE
SYNONYMS:
PATENT DUCTUS ARTERIOSUS: is
an uncommon defect in the cat. A
patent ductus arteriosus occurs when
the embryologic ductus that allows
shunting of blood
between the pulmonary artery and
the ascending aorta fails to close
SYNONYMS: duct of botallo, ductus
botalli, patent arterial duct.
other features of the disease and
may occur secondary to impaired
cardiac lymphatic drainage. The end
result is left or biventricular heart
failure, which develops secondary to
myocardial failure and ventricular
dilation. Pulmonary edema and
pleural effusion may be observed.
When the
right ventricular endocardium is
involved, hepatic congestion and
ascites may develop
PATHOPHYSIOLOGY:
TYPICAL
Pulmonary vascular resistance much
lower than systemic vascular
resistance so: Left to right shunt (aorta
to pulmonary artery) →
increased flow through pulmonary
vasculature → increased return
to left heart → volume overload
of left heart → chronic left-sided
CHF.
RARE
Right-to-left shunt.
Pulmonary hypertension → due to
retention of fetal type pulmonary
vasculature and/or massive
pulmonary overcirculation with a leftright shunt resulting in reactive
some
domestic
shorthair cats
Endocardial cushion defects
DIAGNOSTIC PROCEDURE:
Electrocardiography
Radiography
Echocardiography
MEAN AGE AND
RANGE: <6 months
old
OUTCOME AND PROGNOSIS:
The prognosis is grave, and most
affected cats die of heart failure
or suddenly at a young age.
SIGNS:
A left apical
holosystolic murmur
of mitral
regurgitation,
tachycardia, and a
gallop rhythm.
SPECIES
Dog and cat.
BREED
PREDILECTIONS
MEAN AGE AND
RANGE
Vast majority
identified during
initial vaccination
sequence.
SIGNS:
• Continuous,
loud,
machinerytype murmur
Estimated
prevalence up
to 2.5
cases/1,000
live canine
births; less
common in
cats.
DIAGNOSIS:
CBC/BIOCHEMISTRY/URINALYSIS:
Usually normal unless rPDA
(erythrocytosis with packed cell
volume [PCV] 55–80%).
DIFFERENTIAL DIAGNOSIS:
• Congenital aortic stenosis with
aortic insufficiency
• Ventricular septal defect
(VSD) with aortic valve
prolapse
• Pulmonary arteriovenous
malformations
DIAGNOSTIC PROCEDURE:
Thoracic Radiography
Echocardiography
Angiography
TREATMENT:
• Manage pulmonary
edema with furosemide,
pimobendan, and, if
necessary, oxygen,
nitrates, and cage rest;
following stabilization,
promptly occlude the PDA.
• Ductal closure by surgical
ligation or various
catheter-based occlusion
techniques.
MEDICATIONS:
DRUG(S) OF CHOICE:
• Furosemide • ACE inhibitor such as
enalapril and
pimobendane
VMED 105 – FELINE MEDICINE
hypertension (a left-to-right shunt
typical of PDA) → pulmonary
over circulation → pulmonary
hypertension (as Eisenmenger's
physiology) → right-left shunt.
SYSTEMS AFFECTED:
Cardiovascular
Hemic/lymph/immuneRespiratory
•
•
•
•
AORTIC STENOSIS: A narrowing of
the left ventricular outflow tract
(LVOT) that restricts blood flow
leaving the ventricle; most commonly
congenital, often heritable
SYNONYMS: subaortic stenosis,
discrete subaortic stenosis.
PATHOPHYSIOLOGY:
▪ Congenital narrowing of left
ventricular outflow tract,
aortic valves, or aortic root
causes ventricular
hypertrophy and may
eventually lead to left-sided
cardiac failure or sudden
death.
▪ Sudden death may result from
myocardial hypoxia and fatal
dysrhythmias
▪ Syncope may result from
outflow tract obstruction,
hypoxia or arrythmias.
SEVERE CASES
▪ Obstructed aortic outflow →
reduced cardiac output and
increased left ventricular
pressure → pressure
loudest over
PA
Precordial
thrill.
Arterial
pulses
Caudoventral
displacement
of palpable
LV apex.
Tachypnea,
dyspnea, and
inspiratory
crackles
SPECIES
• Dog and cat.
BREED
PREDILECTIONS
• Himalayans
and 3 mixedbreed cats.
• Siamese cat
MEAN AGE AND
RANGE
• first few
weeks to
months of life
as
subvalvular
lesion
progresses.
PREDOMINANT SEX:
N/A
•
•
Aortic stenosis
reported as
small
contributor of
feline
congenital
heart disease,
about 6%;
approximately
2 out of 1,000
dogs and 0.2
per 1,000 cats
evaluated at
veterinary
teaching
hospitals are
diagnosed
with aortic
stenosis, SAS
most often in
DIAGNOSIS:
CBC/BIOCHEMISTRY/URINALYSIS
• Typically within normal limits.
Digoxin and Diltiazem
hydralazine
DRUG(S) OF CHOICE:
Beta adrenergic blockers
FOLLOW‐UP:
DIFFERENTIAL DIAGNOSIS:
PATIENT MONITORING:
▪ Atrioventricular valve
• Monitor by ECG, Holter
dysplasia
monitor, thoracic
▪ Pulmonic stenosis.
radiography, and
echocardiography.
▪ Ventricular septal defect
(VSD)
• additional monitoring for
renal/electrolyte, blood
▪ Hypertrophic cardiomyopathy
with dynamic left ventricular
pressure, and rhythm
outflow tract obstruction
disturbances.
▪ Innocent 'flow' murmur.
▪ Tetralogy of Fallot
DIAGNOSTIC PROCEDURE:
Contrast Radiography
Radiography
Electrocardiography
VMED 105 – FELINE MEDICINE
▪
TETRALOGY OF FALLOT: is an
uncommon congenital defect in the
cat. It is characterized by a
ventricular septal defect, obstruction
of the right ventricular outflow tract
(pulmonic stenosis), an overriding
(dextropositioned) aorta (arising
from both ventricles), and secondary
right ventricular hypertrophy.
SYNONYMS: Fallot’s Tetralogy,
Fallot’s Syndrome
overload → ventricular
concentric hypertrophy
(LaPlace Law) → increased
myocardial oxygen
consumption → coronary
perfusion not proportional to
hypertrophy → myocardial
hypoxia → ventricular
dysrhythmias →
syncope/sudden death.
Rarely → myocardial
failure → left-sided CHF.
SYSTEMS AFFECTED:
Cardiovascular
Respiratory
PATHOPHYSIOLOGY:
SEVERE
• Secondary right ventricular
hypertrophy → increased
right ventricular pressure →
shunting from right-to-left
ventricle → cyanosis →
hypoxia → hypoxic kidneys
release erythropoietin →
increased red blood cell
production → polycythemia
→ animal incapacitated by
hypoxia.
SIGNS: development
of congestive heart
failure and include
tachypnea, dyspnea,
and crackles
heart murmur of
aortic stenosis might
be expected to be
loudest
SPECIES, AGE, SEX
Dogs and cats;
present at birth;
possible male
predisposition in cats
SIGNS:
HISTORICAL
FINDINGS
• Weakness.
• Syncope.
• Shortness of
breath.
• Exercise
intolerance
• Stunted
growth
dogs and
supravalvular
aortic stenosis
most often in
cats.
DIAGNOSIS:
CBC/BIOCHEMISTRY/URINALYSIS:
• Compensatory erythrocytosis
if the shunt is right-to-left.
TREATMENT:
• Most treated as
outpatients.
• Exercise restriction
recommended.
DIFFERENTIAL DIAGNOSIS:
• Treat erythrocytosis by
• Aortic stenosis
periodic phlebotomy to
• Atrioventricular valve
maintain a PCV of 62–
dysplasia
68%.
• Pulmonic stenosis.
• Palliative surgical
procedures that enhance
• Ventricular septal defect
pulmonary blood flow
(VSD)
have been performed.
• Hypertrophic cardiomyopathy
•
Definitive surgical
with dynamic left ventricular
correction requires
outflow tract obstruction
cardiopulmonary bypass.
• Innocent 'flow' murmur.
• Endocarditis
MEDICATIONS:
VMED 105 – FELINE MEDICINE
PULMONIC STENOSIS: Congenital
narrowing of the right ventricular
outflow tract, obstructing the
passage of flow from the right
ventricle (RV) to the pulmonary
artery (PA); usually valvular, but
may be subvalvular or
supravalvular. Double chambered
RV is a variant of subvalvular
pulmonic stenosis (PS) characterized
by a focal muscular or fibromuscular
stenosis in the mid RV.
Pulmonic stenosis or stenosis of the
pulmonary artery, (main pulmonary
artery or a peripheral pulmonary
artery) results in similar hemodynamic
effects. Increased right ventricular
systolic pressure resulting in right
ventricular concentric hypertrophy,
septal flattening, right atrial dilation,
and the development of right heart
failure can all be observed
SYSTEMS AFFECTED:
• Cardiovascular
PHYSICAL
EXAMINATION
FINDINGS
• Systolic left
basilar
ejection
murmur,
caused by
RVOTO in
most patients;
some with
hyperviscosity
and severe
pulmonary
stenosis do
not have
murmurs.
• Cyanosis
• Arterial
pulses usually
normal.
DIAGNOSTIC PROCEDURE:
Thoracic Radiography
Echocardiography
DRUG(S) OF CHOICE
Nonselective β-adrenergic
antagonists such as propranolol
may be palliative
SPECIES
Dog and cat
DIAGNOSIS:
CBC/BIOCHEMISTRY/URINALYSIS
• Generally unremarkable.
• Polycythemia may be present with
right-to-left shunting.
• NT-proBNP is increased,
particularly with severe stenosis or if
clinical signs present.
MEDICATIONS
DRUG(S) OF CHOICE
If signs of CHF, treat ascites with
furosemide
Uncommon in
cats,
especially as
BREED
an isolated
PREDISPOSITION has defect;
not been noted.
comprised 3%
These defects have
of congenital
been reported in 1
heart
Devon Rex, several
defects in one
domestic shorthairs,
study
and 1 Persian.
IMAGING/DIAGNOSTIC
PROCEDURE:
Radiography
Echocardiography
VMED 105 – FELINE MEDICINE
SYNONYMS
Pulmonary stenosis, pulmonary valve
dysplasia
VASCULAR RING ANOMALIES:
Congenital malformation of one or
more parts of the aortic arch during
embryogenesis such that vessels
encircle the esophagus and trachea,
causing compressionartery ventrally,
and ductus or ligamentum arteriosum
on the left and dorsally.
SYNONYMS
Vascular ring malformation;
persistent right aortic arch (PRAA),
which is the most common vascular
ring anomal
• Hepatobiliary
• Respiratory
• Nervous
PATHOPHYSIOLOGY
Esophageal stricture →
regurgitation of solid food (usually
first seen at weaning) → poor
growth and voracious appetite.
Esophageal cicatrization,
megaesophagus and esophageal
hypomotility may develop - affect
long-term prognosis.
Aspiration pneumonia - common
complication
SIGNS
General Comments:
• Mild stenosis—
usually no clinical
signs.
• Severely affected
patients—may
develop CHF,
exertional syncope,
or sudden death.
Historical Findings:
• Abdominal
distension.
• Dyspnea.
• Exertional syncope,
exercise intolerance,
or sudden death.
• Asymptomatic.
SPECIES, AGE, SEX
Dogs > cats; no sex
predisposition
Clinical signs usually
develop shortly after
weaning.
SIGNS:
Regurgitation of
undigested solid
food in
animals <6 months
old.
• Malnourishment in
many animals.
Doppler Echocardiography
Angiography
Electrocardiography
DIAGNOSIS
CBC/BIOCHEMISTRY/URINALYSIS
• Results usually normal.
• High white blood cells in some
animals with aspiration pneumonia.
DIFFERENTIAL DIAGNOSIS
• Congenital megaesophagus.
• Stricture, diverticulum, or
esophageal foreign body.
• Esophageal motility disorder in
shar-peis.
IMAGING
Thoracic radiography
Contrast esophagography
TREATMENT
Surgical correction of the vascular
entrapment is indicated
Medical management of
concurrent aspiration pneumonia
may be necessary.
Feeding procedures for
megaesophagus may also be
necessary for a prolonged period.
Supportive care with oxygen may
be needed in animals with
aspiration pneumonia.
VMED 105 – FELINE MEDICINE
• Time between
eating and
regurgitation varies.
• Signs of aspiration
pneumonia (e.g.,
cough,
tachypnea, or
dyspnea) in some
animals
Fluoroscopy
Angiography
MEDICATIONS
DRUG(S) OF CHOICE
Broad-spectrum antibiotics, such as
enrofloxacin and amoxicillin