Download Cardiology-Mitral-valve-insufficiency

March 2011
Diagnostic
Update
Case
report
By colleagues for colleagues
Cardiology: Mitral valve insufficiency
Nt-proBNP as a deciding factor for further cardiological testing
of stage B2 patients
Clinical signs and preliminary report
Laboratory tests
A 13-year-old, uncastrated male Miniature Schnauzer was presented at the clinic. The owner reported that the dog had shown symptoms of diminished capacity for exercise for several months, for
example, tiring easily, reduced desire for exercise and increased
need for sleep. Other symptoms, such as cough, panting, loss
of appetite, increase in abdominal circumference, paralysis, etc.
were not observed.
Haematology
by Dr P. Holzhauer,
Werl Animal Clinic
NSF
Biochemistry
ALT
112 U/l
(reference range 10-100 U/l)
ALP
436 U/l (reference range 23-112 U/l)
Na/K/Cl NSF
Other biochem. parameters NSF
Cardiopet® proBNP 1987 pmol/l
Evaluation for the range >1800 pmol/l:
The likelihood that clinical signs (e.g. respiratory and/or exercise intolerance) are due to heart failure is high. Further cardiac
workup or cardiac consultation recommended.
Further cardiological testing
Radiographic examination
The latero-lateral projection of the chest radiograph showed a
vertebral heart score (VHS) of 11.5 vertebral bodies and left atrial
enlargement with loss of cranial tapering in the transition from the
right atrium to the right ventricle. The trachea was elevated, the
two mainstem bronchi were divergent and the mitral triangle was
diminished. There was moderate peribronchial alveolar oedema
and the pulmonary veins were slightly distended.
Clinical examination
Nutritional status: healthy muscle status,
well-defined ’waist’
Conjunctivas/
mucous membranes: pale pink, smooth and shiny
Capillary refill:
<2 seconds
Tip of nose:
dry
Oral cavity/teeth
NSF
Skin turgor: preserved
Cough reflex larynx: active
Heart rate: 86 bpm, regular,
distinct heartbeats, strong
Heart murmur:systolic heart murmur grade
I-II/VI over the mitral valve
Pulse:
regular, strong, no pulse deficit
Respiratory rate:18 breaths/min., slightly increased
upon inspiration
Palpation of abdomen: borders of organs palpable without
pain, no indication of fluid or
increase in size
Body temperature: 38.3°C
Body weight:
10 kg
Right latero-lateral
chest projection
Dorsoventral chest projection
The dorsoventral chest projection
showed left atrial and left ventricular
enlargement, as well as diverging
mainstem bronchi superimposed on
the left atrium.
Echocardiography
From the right:
Dimension measurements in B-mode
LVAW = 6.7 mm
(norm 5.8 – 6.9 mm)
LV = 32.6 mm
(norm 21.5 – 33.2 mm)
VS = 8.2 mm
(norm 7.3 – 8.5 mm)
LA = 29.6 mm (
norm 118 – 27.2 mm)
Measurement of the
dimensions of LA and
AO in M-mode...
Mild enlargement
of the left atrium
Measurement of the
EPSS in M-mode
Mildly increased
EPSS due to mitral
valve insufficiency
Teichholz formula
for LV in B-mode
Normal motion of
the wall of the left
ventricle
…and in B-mode
Enlargement of
the left atrium in
proportion to the
aorta
Measurement of
the shortened
cycle in B-mode
Hyperechogenic
papillary muscles with
partly hyperechogenic
exterior wall of the left
ventricle
From the left:
Visualization of the
LA, the mitral valve
and the LV in B-mode
in systole
Mildly dilated left
atrium, mitral valve
thickened at the tips
of the leaflets
Visualization of the
blood flow at the mitral
valve in systole using
PW Doppler
Marked insufficiency
flow profile in systole
with 3 m/sec
Visualization of the
flow conditions at the
mitral valve in systole
using colour Doppler in
systole
Turbulence (green)
and regurgitation
flow (blue) into the
left atrium in systole
with closed mitral
valve
ECG
Lead II measurements
(reference ranges in brackets)
P wave 0.04 sec (0.04 sec)
P wave 0.6 mV (0.4 mV)
PR interval
0.06 sec (0.06 sec)
QRS complex 0.04 sec (0.05 sec)
R wave 1.6 mV (2.5 mV)
ST segment deviation > 0.2 mV depression
(<0.2 mV depression)
T wave < 25% of R wave height, +ve,
(< 25% of R wave height, +ve,
-ve or biphasic)
Diagnosis
The patient was diagnosed with moderate stage B2 mitral valve
insufficiency (ACVIM Consensus Statements). This is a structural
heart disease without or with earliest clinical symptoms, however,
with haemodynamically significant regurgitation and radiological
and echocardiographic signs, such as enlargement of the left side
of the heart and enlargement of the atrium.
Mitral valve dysplasia
Mitral valve dysplasia is a congenital deformity of the mitral valve.
It occurs most frequently in large dog breeds. Echocardiography
shows visible morphological changes, including thickened or
shortened leaflets, prolapsed leaflets, papillary muscles that are
shifted upwards or deformed and excessive dilatation of the valve
annulus. The functional disorder is caused by the regurgitation
being clinically relevant. As soon as ventricular filling is impaired,
left atrial pressure increases and pulmonary oedema can occur.
This leads to clinical symptoms including diminished capacity for
exercise, respiratory symptoms of left-sided heart failure (dyspnoea, cough), loss of appetite and atrial arrhythmia. A systolic
heart murmur can be auscultated at the left apex. Enlargement
of the left atrium and a dorsal shift of the mainstem bronchus are
characteristic radiographic findings.9
Exclusion:
The dog is a Miniature Schnauzer, i.e. a small dog breed. In the
patient’s history prior to the first visit, only slight impaired performance was reported. In the echocardiogram, no morphological
deformities could be detected.
Differential diagnoses
Subaortic stenosis (SAS)
Subaortic stenosis is a congenital deformity of the aortic valve.
Clinical symptoms include diminished capacity for exercise,
weakness upon effort and syncope. Respiratory symptoms of
left-sided heart failure (dyspnoea, cough) are possible. A weak,
small pulse is characteristic. Findings on auscultation include a
systolic heart murmur on the left in the area of the apex of the
heart. In dogs with mild SAS, the radiological changes of pulmonary oedema may be mild or absent. The echocardiogram shows
left ventricular hypertrophy with subaortic stenosis. Furthermore,
dilatation of the ascending aorta, thickening of the aortic valve
and left atrial enlargement with hypertrophy may occur. Doppler
echocardiography can visualize systolic turbulence and detect
high systolic outflow velocities within the aorta. Mitral regurgitation9 is a frequent occurrence.
Exclusion:
In the dog‘s history as a puppy, there were no pathological findings on auscultation. Prior to the first visit, the dog had only very
minor clinical symptoms. The dog’s pulse was normal and the
systolic heart murmur could be auscultated left of the apex. There
were no morphological changes in the left ventricular outflow tract
and the flow profile and flow velocity at the aorta were normal.
Physiological Doppler flow
profile at
the aorta
Four-chamber view, left scanning;
visualization of the physiological mitral valve leaflets
Treatment
The patient was prescribed an ACE inhibitor and a diuretic
for treatment.
Treatment guidelines for chronic atrioventricular valve
disease
Patients without symptoms/with mild symptoms (stage B)
· Inform the patient’s owner about the course of disease
and early signs of heart failure
· Perform routine measures (blood pressure measurement, chest
radiograph and echocardiography) and annual check-ups,
ensure normal body weight, maintain fitness, regular exercise
· Monitor and treat other medical problems
· Low-sodium diet
· In dogs with dilatation of the LA and/or of the LV, prescribe
ACE inhibitors and diuretics.
Discussion
The formation and release of atrial natriuretic peptide (ANP) and
B-type natriuretic peptide (BNP) in the heart is primarily triggered
by stretching of the myocardium. In dogs with heart failure, levels
of ANP and BNP in the blood are elevated.13
In patients with heart disease, this results in overstimulation of the
renin-angiotensin-aldosterone system. The natriuretic peptides
Diagnostic
Update
Case
report
counteract this activity by stimulating natriuresis, increasing blood
flow in the kidneys, promoting diuresis and vasodilatation and
strengthening diastolic heart function. The circulating concentrations of the atrial natriuretic peptide (ANP) and the B-type
natriuretic peptide (BNP) are elevated primarily as a reaction to
the increased burden on the myocardial wall.9
Nt-proBNP occurs when serum endopeptidases split proBNP
in order to form BNP. Whilst Nt-proBNP is biologically inactive,
it possesses a higher stability than the biologically active BNP.
Since Nt-proBNP and BNP are formed at a ratio of 1:1, the measurement of Nt-proBNP measured in the context of heart disease
precisely reflects the amount of active BNP formed.9
Due its better stability and longer half-life, Nt-proBNP is used for
immunoassay.
It is difficult to determine the underlying reason for respiratory
symptoms in older small breed dogs, in which concomitant mitral
valve diseases and primary chronic respiratory disorders are not
uncommon. In these cases, an elevated Nt-proBNP concentration
may be helpful if the patient does not have a history of symptoms
or there are no clinical symptoms or radiographic findings at
present.4
The measurement of the natriuretic peptides in the blood can
support the diagnosis of heart disease when combined with physical examination, radiographic examination and echocardiogra-
phy. Nt-proBNP assay can be helpful for the diagnosis of occult
cardiomyopathy in dogs with only mild symptoms.9
The combination of different biomarkers, such as cTnl (troponin I)
and Nt-proBNP, may be able to provide better diagnostic results
in dogs with early symptoms than the determination of cTnl
alone.9
Two published studies evaluated the efficacy of treatment with
angiotensin-converting enzyme inhibitors (ACE inhibitors) in dogs
in the early stage of disease.7,10
ACE inhibitors combined with diuretics improve clinical symptoms
and prolong survival times.2
Treatment control/screening
Dogs that are apparently healthy with an only slightly elevated
individual Nt-proBNP level should undergo repeat testing.5
In the Miniature Schnauzer examined here, an ACE inhibitor and
diuretic were administered based on the radiographic and echocardiographic findings. Cardiac troponin l levels are elevated in
the blood in dogs with congestive heart failure. For the diagnosis
of acute heart failure, it can be detected 4 hours to one week after
myocardial damage.8,12
Nt-proBNP can be detected in the blood for more than one week.
For this reason, a combination of troponin I and Nt-proBNP testing may be recommended.
Literatur
1)Boswood A. Herzklappenerkrankungen beim Hund. Veterinary Focus 2008; Vol 18 No 3, 25-31
2)BENCH, Pouchelon JL, Martignoni L, et al. The effects of benazepril on survival times and clinical signs of dogs with congestive heart failure: Results of a multicenter,
prospective, randomized, double-blinded, placebo-controlled, long-term clinical trial. J Vet Cardiol 1999; 1:7-18
3)Chetboul V, Serres F, Tissier R, Lefebvre HP, Carlos Sampedrano C, Gouni V , Poujol L, Hawa G, Pouchelon JL. Association of plasma N-terminal pro-B-type natriuretic
peptide concentration with mitral regurgitation severity and outcome in dogs with asymptomatic degenerative mitral valve disease. J Vet Intern Med 2009; 23:984-994
4)Fine D, DeClue A, Reinero C. Brain natriuretic peptide for discrimination of respiratory distress due to congestive heart failure or primary respiratory disease. Abstr. in Proceedings 25th Annu Forum ACVIM 2007
5)Kellihan H, Oyama M, Reynolds C, et al. Weekly variability of plasma and serum Nt-proBNP measurements in normal dogs. Abstr. in Proceedings. 26th Annu Forum ACVIM
2008
6) Kraft W, Dürr UM, Hrsg. Klinische Labordiagnostik in der Tiermedizin. 6.Aufl., Verlg. Schattauer
7)Kvart C,Haggstrom J, Pedersen HD, et al. Efficacy of enalapril for prevention of congestive heart failure in dogs with myxomatous valve disease and asymptomatic mitral
regurgitation. J Vet Intern Med 2002; 16:80-88
8)Mellor J, Mellanby RJ, Baines EA, Villiers EJ, Archer J, Herrtage ME. High serum troponin I concentration as a marker of severe myocardial damage in a case of suspected
exertional heatstroke in a dog. Journal of Veterinary Cardiology 2006; Vol8, p 55-62
9) Nelson RW, Couto CG. Innere Medizin der Kleintiere. 2. Dt. Auflage, Verlg. Urban & Fischer München
10)Pouchelon JL, JametN, Gouni V, et al. Effect of benazepril on survival and cardiac events in dogs with asymptomatic mitral valve disease: A retrospective study of 141
cases. J Vet Intern Med 2008; 22:905-914
11)Reynolds C, Oyama M. Biomarker in der Diagnose caniner Herzerkrankungen. Veterinary focus 2008; Vol18 No3
12)Tobias R, Skrodzki M, Schneider M. Kleintierkardiologie kompakt. 1. Aufl. 2008, Schlütersche Verlagsgesellschaft GmbH
13)Vollmer, A. Atrioventrikular-(AV-)Klappenerkrankungen. Kleintierpraxis 2010; 55; Heft 9; 505-522
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