Echocardiography

Question 1

Pulmonic Stenosis

Answer 1

Echocardiography is useful to confirm the diagnosis and to grade the severity of the stenosis.

Findings include:

• Concentric hypertrophy of the RV (Figure 7.59), secondary to pressure overload on the RV. Seen as a thickening of the right ventricular free wall that can approach or exceed the thickness of the left ventricular free wall
• Prominent right ventricular papillary muscles are sometimes visible
• Flattening of the IVS due to the elevated right ventricular pressure. On M-mode images, paradoxical motion of the septum may be seen (Figure 7.60)
• Abnormal pulmonic valve (Figure 7.61):
  
  • Thickened, with a limited systolic excursion
  • Hyperechoic
  • If the valve leaflets are fused, occasionally ballooning can be seen during systole.
• Abnormal subvalvular region:
  
  • discrete subvalvular fibrous ring may also be seen as well as generalized infundibular hypertrophy
• Post-stenotic dilatation of the main pulmonary artery distal to the valve
• Possible right atrial dilatation (and occasionally right ventricular dilatation).

Doppler studies:

• Accelerated ejection velocity through the pulmonic valve (Figure 7.62). Care should be taken to achieve parallel alignment and to use continuous wave (CW) Doppler to achieve accurate velocity measurements.
• Turbulent ejection flow in the main pulmonary artery (Figure 7.63). Possible mild to moderate pulmonary insufficiency (diastolic back-flow from the main pulmonary artery to the RV) (Figure 7.62).
• The severity of the obstruction can be estimated by accurate measurement of the peak flow velocity through the main pulmonary artery. This is then used to calculate the instantaneous PG across the obstruction using the modified Bernoulli equation. The PG may be used to grade the severity of the stenosis, though it should be noted that the reliability of this measurement may vary with myocardial contractility and sedation/ anaesthesia:
  
  • Mild: <50 mmHg
  • Moderate: 50-6O mmHg
  • Severe: >80 mmHg. Such animals are likely to develop right-sided cardiac failure early and are candidates for balloon valvuloplasty.
• Tricuspid insufficiency. Measurement of this may also be useful to assess the degree of stenosis when accurate measurement of main pulmonary artery velocity cannot be obtained.

Question 2

Aortic Stenosis

Answer 2

It can be extremely difficult to detect mild aortic stenosis with standard echocardiography. Subtle or no changes may be seen.

Moderate to severe cases:

• Left ventricular concentric hypertrophy is seen, with thickening of the left ventricular free wall and IVS
• Hyperechoic ridge or circumferential ring of hyperechoic tissue in the region of the LVOT
• Post-stenotic dilatation of the ascending aorta

Severe cases as above plus:

• Hyperechoic papillary muscles and endocardial surface due to areas of myocardial ischaemia and subsequent fibrosis
• If there is mitral regurgitation, left atrial enlargement may be observed
• Systolic anterior motion of the mitral valve may be seen in animals with concurrent mitral dysplasia

Doppler studies:

These are important in diagnosis and are characterized by high-velocity turbulent aortic flow. The maximum normal aortic velocity in most dogs is 1.7 m/s. However, higher velocities can be seen in normal dogs and also breeds with slightly reduced LVOT size (e.g. Boxers, Golden Retrievers, Bull Terriers). Note also that conditions of excitement and stress will increase the velocity, and myocardial failure will reduce it.

• Subcostal (retroxiphoid) views are ideal for good alignment and accurate estimation of aortic velocities, although they are difficult to achieve in larger breed dogs due to the distance between the transducer and the LVOT; CW Doppler should be used.
• The diagnosis is reinforced when increased velocities show rapid focal acceleration in the LVOT and/or are accompanied by turbulent flow and anatomical lesions.
• Calculation of the PG across the stenosis (using the maximal aortic velocity) may be used for grading severity and estimating prognosis:
  
  • Dogs with maximal PG of <50 mmHg and minimal ventricular hypertrophy are more likely to lead normal lives
  • Dogs with maximal PG of >125 mmHg are very likely to develop serious complications or die suddenly.
• Mitral inflow studies may show an increased A wave during diastole (decreased E:A ratio) due to loss of compliance in the hypertrophied LV.
• Functional mitral regurgitation might be present in severe cases and those with concurrent mitral dysplasia. When present, it usually has a higher velocity than normal due to increased left ventricular pressure (and hence increased PG between the LV and the LA).

Question 3

Dilated Cardiomyopathy

Answer 3

Echocardiography (including Doppler studies):

2D and M-mode echocardiography are normally sufficient to make the diagnosis of DCM. However, since the stringent diagnosis of DCM requires the active exclusion of other congenital or acquired cardiac disease, colour flow and Doppler echocardiography are indicated. Furthermore, Doppler studies are required for identifying and classifying abnormalities in diastolic function, and for supporting the presence of systolic function. Guidelines for the robust diagnosis of DCM have recently been proposed.

2D echocardiographic abnormalities in DCM typically include:

• Subjective findings include LV dilatation with relatively thin walls and poor contractility
• A rounded LV chamber (increased sphericity)
  
  • LV diastolic length:LV diastolic width at chordae tendinae level (= M-mode left ventricular internal dimension in diastole, LVIDd) <1.65
• End-systolic volume index >30 ml/m² (confirms systolic dysfunction and chamber dilatation)
• Ejection fraction <40%
• The LA is dilated in symptomatic dogs
• The right-sided chambers mayor may not be dilated

M-mode echocardiographic abnormalities in DCM include:

• Increased LVIDd and left ventricular internal dimension in systole (LVIDs) for size or breed-based reference ranges
• Relative wall thickness (left ventricular free wall in diastole, LVFWd:LVIDd) is decreased
• Fractional shortening <20%
• Increased mitral valve M-mode EPSS
• Reduced aortic root systolic excursion on aortic M-modes, and possibly premature closure of aortic valve
• The LA may be enlarged in symptomatic dogs (increased M-mode LA:Ao ratio)
• Systolic time intervals: M-mode aortic pre-ejection period (PEP):ejection time (ET) >0.4.

Findings with Doppler studies in DCM include:

• Colour flow Doppler may identify mitral and/or tricuspid regurgitation , without grossly abnormal valve apparatus, due to stretch of the atrioventricular annuli
• Mitral regurgitant velocity may be lower than normal, due to impaired LV systolic function and elevated LA pressures, giving a reduced systolic PG between the LV and LA. Mitral regurgitant velocity <4 m/s is associated with poor prognosis
• Aortic velocity and velocity time integrals may be lower than normal, due to systolic dysfunction
• Aortic PEP:ET ratio may be increased (>0.4)
• The assessment of diastolic function is important to provide prognostic information. Dogs with a restrictive physiology have reduced survival.

Question 4

Boxer Cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy

Answer 4

Boxer dogs with cardiomyopathy may present with the classical findings of DCM, as described above. Until recently, this was the most common presentation in UK and European Boxers. In contrast, North American Boxers are reported to present with malignant ventricular arrhythmias, of right ventricular origin, with minimal changes initially on echocardiography, although systolic dysfunction and LV dilatation can occur later in the course of the disease. This form is now being increasingly recognized in the UK and Europe. In some affected Boxers, the RV may appear dilated with dysplastic RV apical papillary muscles. However, in many Boxers there may be no echocardiographic evidence of structural abnormalities, despite severe ventricular arrhythmias.

Arrhythmogenic right ventricular cardiomyopathy (feline):

Feline ARVC has been recently described, The disease is histopathologically characterized by fibrofatty replacement and infiltration in the myocardium, most pronounced in the RV. Affected cats mayor may not show malignant ventricular arrhythmias. They may show ascites as a manifestation of right-sided congestive heart failure.

Radiographic findings include:

• Changes may show evidence of right-sided congestive heart failure or biventricular failure
• Ascites in association with a dilated CdVC indicate that the abdominal effusion is associated with right-sided congestive failure (Figure 7.118). A pleural effusion may also be present
• There mayor may not be radiographic evidence of left-sided congestive heart failure.

Doppler echocardiographic findings include:

• There is marked right-sided RA and RV dilatation
• Tricuspid regurgitation may be evident due to stretch of the tricuspid annulus (Figure 7.119a). ARVC must be distinguished from tricuspid dysplasia (which will usually show an immature age of onset compared with the middle or older age onset in ARVC)
• A hallmark of this condition is evidence of dysplastic papillary muscles within the RV apex (the transducer needs to be moved far enough caudally and sternally to appreciate this feature from the RPS long-axis view)
• Variable changes affect the LV. In advanced disease, the LV also becomes dilated and hypokinetic (Figure 7.119b).

Question 5

Hypertrophic Cardiomyopathy

Answer 5

Doppler echocardiography:

This is the imaging modality of choice to distinguish between the various forms of myocardial disease. The following 2D and M-mode findings (Figure 7.103) are typical in HCM:

• Generalized or focal, symmetrical or asymmetric hypertrophy, with diastolic wall thickness 2:6 mm
• The LV chamber diameter may be normal or small
• Subjective impression that the papillary muscles are hypertrophied
• LA size may be normal or dilated
• Systolic function is normally preserved; fractional shortening can often be >45%, indicating a hyperkinetic LV, due to the low wall stress

The typical findings in feline HCM patients at various stages of the disease are documented in Figure 7.109. The mitral inflow patterns are illustrated in Figures 7.110 and 7.111 . Corresponding abnormalities in diastolic dysfunction are illustrated for IVRT (Figure 7.112) and PVF (Figure 7.113).

Question 6

Hypertrophic (Obstructive) Cardiomyopathy

Answer 6

Hypertrophic (obstructive) cardiomyopathy:

This term is reserved for forms of HeM where dynamic obstruction of the LVOT is documented by echocardiography. A simplified series of events leading to this finding include:

• Turbulence of flow in the LVOT as blood travels around a basal septal bulge associated with the hypertrophy. This may be recognized as colour variance in the LVOT
• This may result in a Venturi effect on the anterior mitral valve leaflet, which is ‘sucked’ into the LVOT during systole. This further narrows the LVOT
• The LVOT and aortic velocities may then be increased, with abnormal biphasic acceleration on spectral Doppler, giving a scimitar shape
• The mitral valve is therefore incompetent, and typically, an eccentric jet of mitral regurgitation, coursing towards the posteriolateral LA wall, is recorded by colour flow Doppler
• Other factors are almost certainly involved in systolic anterior motion of the mitral valve, such as altered papillary muscle alignment
• Systolic anterior motion can be confirmed by mitral M-mode. Normally, the temporal resolution of 2D is not sufficient to confirm this in real time.

Hypertrophic (obstructive) cardiomyopathy (HOCM) is frequently diagnosed in asymptomatic cats, due to the identification of a heart murmur. The murmur is due to mitral regurgitation or LVOT obstruction, and it may be variable depending upon how relaxed or stressed the cat is. It may not be possible to document HOCM in a sedated or very relaxed cat during echocardiography.

Question 7

Restrictive Cardiomyopathy

Answer 7

Doppler echocardiographic findings include:

• There is a marked left atrial enlargement
• An organized thrombus may be apparent in the LA or LAu
• Spontaneous echocontrast of blood within the LA may be seen, giving the impression of swirling ‘smoke’. This represents a prothrombotic state
• The LV has relatively preserved systolic function, and relatively normal LV dimensions and wall thickness
• This is a disease of diastolic dysfunction. Detailed Doppler assessment of myocardial function is consistent with a restrictive physiology
• In the endomyocardial form of RCM, adhesions may be seen crossing the LV chamber and the endocardium may appear irregularly thickened
• In the myocardial form of RCM , the myocardium and endocardium echotexture appear unremarkable.

Question 8

Mixomatous Valve Disease

(Mitral or Tricuspid)

Answer 8

Echocardiography:

Echocardiography is useful to confirm the diagnosis and assess systolic function. It cannot be used to identify heart failure, hence radiography and ultrasonography are complementary techniques in the evaluation of this condition. It is important to examine the entire valve as the lesions may be unevenly spread.

• Early signs include a systolic bulging of the valve leaflet(s) with or without regurgitation.
• This progresses to thickening of the leaflet, most pronounced at the tip. The leaflet may appear thickened, nodular or club- like. Changes are often more pronounced on the septal leaflet. Note that the valvular changes in large-breed dogs may not appear obvious, yet severe disease may still be present.
• Thickening of the chordae tendinae.
• Flail leaflet:
  
  • Mild to moderate: the tip of the leaflet moves into the LA during systole
  • Severe: the entire leaflet moves into the LA during systole
• Enlarged LA. It is very important to assess left atrial size as this parameter reflects severity (except in cases of acute chordae tendinae rupture).
• LV and M-mode parameters:
  
  • Mild mitral myxomatous valvular degeneration does not lead to abnormal left ventricular size
  • However, with time the left ventricular end-diastolic short-axis dimension increases but the end-systolic dimension remains the same. This is the result of eccentric hypertrophy seen in moderate to severe disease
  • It is important to note that with moderate to severe mitral regurgitation the values of ejection phase indices (e.g. fractional shortening, ejection fraction, velocity of circumferential fibre shortening) are often increased. This is due to the rapid regurgitation of left ventricular blood into the low pressure LA during systole
  • Hyperdynamic wall motion will be seen (Figure 7.132)
  • Small-breed dogs often have a fractional shortening percentage of greater than 50% with severe mitral regurgitation. Hence, if a normal fractional shortening (or other ejection phase index) is identified in a small-breed dog with severe mitral valvular disease, then reduced myocardial contractility is present
  • End-systolic volume indices more accurately assess myocardial contractility
  • Breed differences: note that myocardial failure is more severe and develops earlier in large-breed dogs with myxomatous mitral valvular degeneration . Also note that large dogs usually have a fractional shortening percentage within the 25-40% range with severe mitral regurgitation.
• Right ventricular and right atrial enlargement, depending on the degree of tricuspid disease.

Dopper Studies:

• Valvular insufficiency (mitral, tricuspid. Note that a small jet near the mitral valve should not be over interpreted as this can be seen in normal dogs.
• Typically the mitral regurgitant jet is 5-6 m/s in dogs without myocardial failure. The speed of the jet depends on the pressure differences between the LA and LV:
  
  • Systemic hypertension increases jet velocity
  • Systemic hypotension, a large orifice, dramatic increases in left atrial pressure and systolic failure all decrease jet velocity.
• An increased tricuspid regurgitant jet velocity (~2.8 m/s) indicates pulmonary hypertension. Pulmonary oedema, secondary to severe mitral disease or other causes of pulmonary hypertension should be considered . Pulmonic stenosis will also increase the velocity of a tricuspid regurgitant jet, but other changes will be present (see Congenital heart disease, above).
• The size of the mitral regurgitant jet can be compared with the size of the LA and is useful in assessing the severity of the disease.
• Additional Doppler techniques have been described, but left atrial size remains a more reliable parameter for the evaluation of the disease severity.
• Mitral diastolic filling velocity is usually increased when significant mitral regurgitation is present.
• Doppler parameters of systolic function can be assessed (see Chapter 2).

Question 9

Infective Endocarditis

Answer 9

Infective endocarditis involves bacterial infection and inflammation of the cardiac valves in almost all cases, though strictly speaking the term refers to any infection of the endocardial surface of the heart. Transient or persistant bacteraemia is the most common aetiology. The condition is seen mainly in medium to large pure-breed dogs and rarely in cats. German Shepherd Dogs may be over-represented. The mitral valve and aortic valve are the most commonly affected in both species.

Bacteria colonize the valve and create vegetative lesions or destroy the valve, both of which lead to valvular regurgitation. Less commonly the valve may narrow and become stenotic. Organisms reported in canine endocarditis include Staphylococcus aureus, haemolytic and non-haemolytic streptococci and Escherichia coli. Rarer isolates include Corynebacterium, Pseudomonas, Erysipelothrix and infection with the proteobacteria Bartonella vinsonii.

Clinical presentation of the condition varies. Clinical signs include lethargy, pyrexia, weakness, anorexia, gastrointestinat disease and lameness. A heart murmur is usually, but not always, present. A recent onset of a murmur, pyrexia and the presence of lameness should increase the index of suspicion for infective endocarditis. Blood cultures are used to confirm the diagnosis of bacteraemia, but are not always sensitive.

Echocardiography:

This is extremely useful in diagnosis:

• Visualization of vegetations. Vary from small nodules to large florid cauliflower-like masses (Figure 7.134). The valve lesions can look identical to those in myxomatous valvular degeneration
• Infective endocarditis lesions are usually solitary and more echogenic. History and signalment are helpful in distinguishing the two:
  
  • Myxomatous mitral valve degeneration: small breed, older, chronic history of murmur, pyrexic, systemically well
  • Infective endocarditis: large breed, recent onset of murmur, pyrexic, systemic illness.
• Valvular destruction in the absence of vegetations may also be present. Seen as a defect in the valve and consequent regurgitation Abnormal valvular motion.

Doppler studies: Depending upon which valve is involved, aortic or mitral valve regurgitation may be seen .

Question 10

Pulmonic and Aortic Insufficiency

Answer 10

There are many congenital diseases that result in clinically significant pulmonic or aortic insufficiency (see Congenital heart disease) . However, both pulmonic and aortic insufficiency may also be seen as non-clinically significant findings in acquired conditions. This is especially the case for pulmonic insufficiency, which is an incidental finding in many dogs. Myxomatous degeneration of the valve leaflets has also been described in both locations, but is very unlikely to result in clinical signs.

Other acquired diseases that may result in aortic and pulmonic insufficiency are:

• Aortic - infectious endocarditis
• Pulmonic - pulmonary hypertension, main pulmonary artery dilatation (e.g. heartworm).

Echocardiography

Pulmonic insufficiency:

• A small flame-like jet of pulmonic insufficiency is commonly seen in clinically normal dogs (Figure 7.135). The maximal velocity is usually 1 m/s
• Pulmonary hypertension should be considered when the jet velocity is ~2.2 m/so
• Pulmonic stenosis will also give a high-velocity jet (see Congenital heart disease).

Aortic insufficiency:

• A small flame-like jet of aortic insufficiency is occasionally seen in clinically normal dogs
• A large jet should alert suspicion of subaortic or aortic stenosis (see Congenital heart disease) and requires further investigation.

Question 11

Traumatic Valvular Disease

Answer 11

Traumatic rupture of the chordae tendinae or papillary muscles may occur and has been reported in dogs and cats secondary to falling from a height or other blunt thoracic trauma. The result is acute onset mitral or tricuspid regurgitation.

Radiography:

Varying degrees of chamber enlargement may be seen, depending on the time elapsed since the injury occurred, the extent of injury and whether the mitral or tricuspid valve was involved . Animals with left-sided injury develop rapid onset pulmonary oedema.

Echocardiography

Features seen include:

• Structural abnormalities depending on the extent of the injury:
  
  • Flail leaflet
  • Partial separation of the leaflet(s) of the valve from the valve annulus
  • Abnormal papillary muscles
• Extensive regurgitant jet from either the mitral or tricuspid valve
• Enlarged left atrial or right atrial dimensions (depending on which valve is involved).

Question 12

Pericardial Effusion

(causes, diagnosis and pathogenesis)

Answer 12

Pericardial effusion is the most common pericardial disease seen in small animals. Fluid can accumulate in the pericardial sac due to a variety of disorders that can be systemic, cardiac or pericardial in origin. All generally produce the same end result of cardiac tamponade and congestive heart failure.

Cardiac tamponade can be defined as compression of the heart due to collection of blood or fluid in the pericardial sac.

• Chronic effusions can reach large volumes before clinical signs occur as the pericardium is able to slowly enlarge.
• More acute pericardial effusions (such as those which occur with left atrial rupture) can produce severe tamponade at small volumes (florid tamponade) and even result in death.

Pericardial effusion may be seen in any dog or cat but older large-breed dogs are predisposed. Clinical signs include lethargy, respiratory distress, anorexia, collapse and abdominal distension. Evidence of right-sided heart failure is usually identified on clinical examination. Heart sounds are muffled on auscultation , pulses are weak and pulsus paradoxus may be present.

Causes of pericardial effusion:

The most common causes of pericardial effusion include (see also Cardiac neoplasia):

• Cardiac haemangiosarcoma
• Idiopathic pericardial effusion
• Heart base neoplasia
• Mesothelioma
• Congestive heart failure
• Other (see below).

Cardiac haemangiosarcoma:

• Most common cause of pericardial effusion in dogs in retrospective studies.
• Older dogs, average weight 32 kg.
• Golden Retrievers and German Shepherd Dogs are over-represented.
• By the time of diagnosis, cardiac haemangiosarcoma has usually metastasized and should be considered a systemic disease.
• Effusion is haemorrhagic but does not clot.

Idiopathic pericardial effusion:

By definition this is an effusion where no underlying cause is identified. It must be a cautious diagnosis as small mass lesions and mesothelioma may be missed on echocardiographic examination and fluid analysis. The features include:

• Older dogs
• Golden Retrievers are over-represented
• The aetiology is poorly understood
• Fluid appears haemorrhagic usually but does not clot.

Heart base neoplasia:

• Usually aortic body tumours.
• Older dogs.
• Brachycephalic breeds are predisposed. It may
• be associated with chronic hypoxia inducing hyperplasia and neoplasia of the chemoreceptors in these breeds.
• Rarely reported in cats.
• May metastasize to lung, LA, pericardium and kidney.
• The effusion varies but is often haemorrhagic.

Mesothelioma:

• May be a more common cause of pericardial effusion than originally thought.
• There is no breed predisposition; occasionally seen in the cat.
• This is a difficult diagnosis to make even with histopathology.
• Mesothelioma is a diffuse neoplasm of the pericardium and cannot be diagnosed on echocardiography.
• Fluid analysis cannot distinguish between idiopathic pericardial effusion and mesothelioma.
• One paper reports that accumulation of significant amounts of fluid within 120 days of pericardectomy increases suspicion of mesothelioma.

Other:

• Congestive heart failure. Often present in right-sided heart failure but rarely of clinical significance.
• Feline infectious perifonitis (FIP).
• Coagulopathy:
  
  • Rarely results in significant tamponade
  • Reported in both dogs and cats.
• Left atrial rupture (uncommon cause):
  
  • Small-breed dogs with chronic myxomatous mitral valve degeneration
  • Acute tamponade and life-threatening condition
  • Effusion will be haemorrhagic and will clot
  • Clots and fluid seen on echocardiography. Trauma. Rare, fluid will be haemorrhagic and will clot.
• Uraemia. Has been reported in both dogs and cats
• Septic pericarditis (rare):
  
  • Migrating foreign bodies, such as grass awns
  • Bite wounds
  • Fungal disease - coccidioidomycosis, one case of aspergillosis.
• Constrictive pericarditis (see below).
• Cardiac lymphoma. Rare, reported in dogs and cats, pericardial fluid will give diagnosis.
• Cardiac rhabdomyosarcoma. Rare, reported in dogs and cats.

Pericardial effusion in the cat: This is most commonly part of a more generalized disease:

• Congestive heart failure
• FIP
• Lymphoma

Symptomatic pericardial effusion in the cat is uncommon. A recent study found that congestive heart failure was the most common cause of pericardial effusion in the cat.

Question 13

Pericardial Effusion

Answer 13

Echocardiography:
This is the diagnostic technique of choice; it is easy, accurate and non-invasive.

Important tip:

The ultrasound examination should be performed before draining the pericardial effusion to improve the chance of visualizing a mass lesion.

• Pericardial effusion is seen as an anechoic (to slightly echoic, depending on type) circular region surrounding the heart. The pericardium is seen as a thin hyperechoic line surrounding the fluid.
• Pleural fluid can occasionally mimic pericardial effusion:
  
  • Pleural effusion is more diffuse and the edges of lung lobes and the mediastinal structures will be outlined by fluid
  • Pericardial effusion is more abundant at the apex and is scant or absent behind the LA. Pleural effusion will surround the LA.
• The heart may swing in the pericardial effusion.
• Cardiac tamponade:
  
  • This affects the lower pressure right side more than the left
  • There is late diastolic to systolic inversion of the RA and diastolic collapse of the RV.
• Identification of mass lesions:
  • An extremely careful search should
    be performed from both LPS and RPS approaches. The tip of the right auricular appendage (RAu) should be visualized and the search should extend dorsally until the aorta and main pulmonary artery are no longer seen
  • A negative examination does not rule out neoplasia
  • Haemangiosarcomas are often found in the RAu or RA
  • Mass lesions surrounding the aorta and main pulmonary artery are commonly chemodectomas
  • Mesothelioma will not be seen
  • Care should be taken not to diagnose intrapericardial thrombi as mass lesions, but it can be impossible to differentiate between them.
  *

Question 14

Constrictive and effusive-constrictive pericarditis

Answer 14

Constrictive pericarditis is characterized by thickened, fibrotic and non-distensible pericardial sac.

Two forms have been described:

1. Constrictive = fusion of the visceral and parietal serous pericardial layers
2. Effusive-constrictive = constriction by the visceral pericardium plus a small volume pericardial effusion. **More common in dogs.

The condition can develop secondary to:

• Chronic idiopathic effusion
• Mycotic pericarditis
• Chronic septic pericarditis
• Foreign body reactions
• Traumatic pericardial haemorrhage
• Intrapericardial neoplasia.

The stiff pericardium will limit ventricular diastolic filling abruptly in mid diastole. Animals present in right-sided heart failure with ascites and jugular venous distension .

Radiography

• Radiography mayor may not be helpful
• Cardiac silhouette can be normal or enlarged, depending on the presence and amount of pericardial fluid
• Enlarged CdVC
• Pleural fluid is often seen
• Hepatomegaly and ascites.

Echocardiographic findings include:

• Cardiac tamponade with only a small (millilitres) pericardial effusion
• Diagnosis can be extremely difficult in the absence of a pericardial effusion (constrictive form)
• Occasionally, the pericardium may appear thickened if effusion is present
• Signs of right-sided heart failure (pleural effusion, enlarged CdVC).

Doppler studies:

• Mitral and tricuspid inflow (E and A waves) may show a restrictive pattern in both dogs and cats. This condition is extensively covered in Chapter 14 in the section on diaphragmatic hernias and so will not be discussed here.