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==Overview==

==Overview==

Restrictive cardiomyopathy (RCM) is a series of acquired pathologies of the feline myocardium. The common element is marked diastolic dysfunction without major alteration of systolic function. In RCM, the compliance and distensibility of the ventricular walls is reduced (ventricles are stiff), such that filling of the ventricles in diastole is compromised. This ultimately reduces the amount of blood that the left ventricle (LV) can accept. During the rapid filling phase of diastole, the pressure within the LV rises abruptly, preventing the entry of additional blood from atrial contraction in late diastole. This consequently increases left atrial pressure and the diameter of the left atrium or both atria.

This is the second most common type of feline cardiomyopathy, representing ~20% of cases.  Restrictive cardiomyopathy (RCM) is a series of acquired pathologies of the feline myocardium. The common element is marked '''diastolic dysfunction''' without major alteration of systolic function. In RCM, the compliance and distensibility of the ventricular walls is reduced (ventricles are stiff), such that filling of the ventricles in diastole is compromised. This ultimately reduces the amount of blood that the left ventricle (LV) can accept. During the rapid filling phase of diastole, the pressure within the LV rises abruptly, preventing the entry of additional blood from atrial contraction in late diastole. This consequently increases left atrial pressure and the diameter of the left atrium or both atria.

Grossly, RCM is characterised by a normal or near-normal appearance of the ventricles with dilation of the left atrium or both atria.  The echocardiographic appearance of the cardiac chambers 2D images of cats with early RCM may be normal; however severe diastolic dysfunction may be evident from M-mode and Doppler imaging.

 

Grossly, RCM is characterised by a normal or near-normal appearance of the ventricles with dilation of the left atrium or both atria.  The echocardiographic appearance of the cardiac chambers 2D images of cats with early RCM may be normal; however severe diastolic dysfunction may be evident from M-mode and Doppler imaging. Two forms of RCM exist, these are the '''endomyocardial form (eRCM)''' and the '''myocardial form (mRCM)'''.

==Aetiology==

==Aetiology==

==Clinical Signs==

==Clinical Signs==

The clinical presentation of cats with RCM, as with other cardiomyopathies, is extremely variable. There may be a long preclinical phase during which the cat remains asymptomatic. Early signs of cardiac dysfunction, such as exercise intolerance, often goes undetected in cats due to their sedentery nature. Cats with RCM are rarely identified in the asymptomatic phase.  Cats with RCM frequently develop congestive heart failure (CHF), arterial thromboembolism (ATE) and are predisposed to arrhythmias.

The clinical presentation of cats with RCM, as with other cardiomyopathies, is extremely variable. There may be a long preclinical phase during which the cat remains asymptomatic. Early signs of cardiac dysfunction, such as exercise intolerance, often goes undetected in cats due to their sedentery nature. Cats with RCM are rarely identified in the asymptomatic phase.  Cats with RCM frequently develop congestive heart failure (CHF), arterial thromboembolism (ATE) and are predisposed to arrhythmias.

 

===Physical Examination===

===Physical Examination===

* May be completely normal

* May be completely normal

* Signs of congestive heart failure

* Signs of congestive heart failure

* Arterial thromboembolism (ATE)

* Arterial thromboembolism (ATE)

====Left-sided Congestive Heart Failure====

====Left-sided Congestive Heart Failure====

*Dyspnoea, tachypnoea, crackles (pulmonary oedema)

*Dyspnoea, tachypnoea, crackles (pulmonary oedema)

*Dyspnoea, restrictive pattern (fast,shallow breathing), muffled heart and ventral lung sounds (pleural effusion)

*Dyspnoea, restrictive pattern (rapid,shallow breathing), muffled heart and ventral lung sounds (pleural effusion)

 

====Right-sided Congestive Heart Failure====

====Right-sided Congestive Heart Failure====

* Jugular pulse

* Jugular pulse

* Hepatojugular reflux

* Hepatojugular reflux

* Occasionally ascites

* Occasionally ascites

====Arterial Thromboembolism====

====Arterial Thromboembolism====

The enlarged left atrium, stasis of blood within the left atrium, and reduced atrial function predispose to thrombus formation, and emboli may result. Typically these cases present with paresis or paralysis of one or both rear limbs due to occlusion at the aorta-iliac trifurcation. In some cases, emboli can involve other areas and can cause complex neurological manifestations, forelimb paralysis or acute renal ischemia.

The enlarged left atrium, stasis of blood within the left atrium, and reduced atrial function predispose to thrombus formation, and emboli may result. Typically these cases present with paresis or paralysis of one or both rear limbs due to occlusion at the aorta-iliac trifurcation. In some cases, emboli can involve other areas and can cause complex neurological manifestations, forelimb paralysis or acute renal ischemia.

==Diagnosis==

==Diagnosis==

===Radiography===

===Radiography===

Radiographs are useful for the diagnosis of congestive heart failure, however they are not able to distinguish the underlying cardiomyopathy. Radiographs may reveal left atrial dilation. On the dorso-ventral projection, a classic 'Valentine heart' shape may be evident due to the marked left atrial/biatrial dilation.  Pulmonary venous conjestion, interstitial/alveolar pattern or the presence of a pleural effusion may be identified.  These findings are not specific for RCM.

Radiographs are useful for the diagnosis of congestive heart failure, however they are not able to distinguish the underlying cardiomyopathy. Radiographs may reveal left atrial dilation. On the dorso-ventral projection, a classic 'Valentine heart' shape may be evident due to the marked left atrial/biatrial dilation.  Pulmonary venous conjestion, interstitial/alveolar pattern or the presence of a pleural effusion may be identified in cases of left-sided congestive heart failure. Dilation of the caudal vena cava may be observed if right-sided congestive heart failure is present.  These findings are not specific for RCM.

===Echocardiography===

===Echocardiography===

==Prognosis==

==Prognosis==

Cats with RCM usually present with advanced disease, the long term prognosis is therefore guarded.

Cats with RCM usually present with advanced disease, the long term prognosis is therefore guarded. One study of 22 cats with RCM found a median survival time of 132 days.