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88  Section C: Congenital Heart Disease


                                                                 cal)  procedures  are  not  typically  beneficial.  Medical
                                                                 therapy to control signs of right heart failure or signs
                                                                 caused by arrhythmias should be considered if they are
                                                                 present  (see  Chapter  18).  Additionally,  because  right
                                                                 atrial dilation may predispose a cat to thromboembolic
                                                                 disease, preventative measures should be considered in
                                                                 cats with moderate or marked right atrial dilation (see
      Congenital Heart Disease                                   Outcome and Prognosis
                                                                 Chapter 20).



                                                                 The  prognosis  for  tricuspid  valve  dysplasia  is  likely
                                                                 dependent on the severity of the valve malformation and
                                                                 the presence of concurrent defects, and it is best deter-
                                                                 mined for each individual case based on echocardiogra-
                       A
                                                                 phy. Extent of valve dysplasia, concurrent heart defects,
                                                                 arrhythmias, and congestive heart failure appear to be
                                                                 negative prognostic indicators in the cat (Chetboul et al.
                                                                 2004).


                                                                 MITRAL VALVE MALFORMATION/DYSPLASIA

                                                                 Mitral valve malformation is considered to be one of the
                                                                 most common congenital malformations in the cat. As
                                                                 with  tricuspid  valve  dysplasia,  this  defect  may  be
                                                                 observed  as  an  isolated  malformation  or  with  other
                                                                 defects, including tricuspid valve dysplasia.
                B
                                                                 Etiology, Pathophysiology, and
              Figure 10.1.  Radiographs	from	a	cat	with	tricuspid	valve	mal-  Gross Pathology
              formation.	Note	the	enlarged	right	atrium,	auricle,	and	right	ven-
              tricle	on	the	ventrodorsal	view	(A).	A	dilated	and	tortuous	caudal	  Etiology
              vena	cava	is	apparent	on	both	views	(B).           The  etiology  of  this  malformation  is  not  known,
                                                                 and  there  is  no  evidence  of  a  familial  etiology  at  this
                                                                 time.

              All cats in stage 1 were asymptomatic. The staging did   Pathophysiology
              not correspond to murmur loudness and it has not yet   Mitral valve malformation results in mitral valve regur-
              been studied to see whether stage of disease correlates   gitation, and left atrial and left ventricular enlargement.
              with progression (Chetboul et al. 2004).           Elevated pressures in the left atrium can result in pul-
                 Tricuspid valve dysplasia has been observed to coexist
              with additional congenital heart malformations; there-  monary venous congestion and the development of pul-
                                                                 monary  edema.  Pulmonary  hypertension  and  right
              fore,  a  thorough  echocardiographic  evaluation  should   ventricular failure can occur as well.
              be performed.
              Diagnosis                                          Gross Pathology
              The physical examination and electrocardiographic and   Mitral  valve  dysplasia  is  characterized  by  an  enlarged
              radiographic  findings  can  overlap  with  many  other   mitral  valve  annulus;  short,  thickened  leaflets;  short,
              cardiac  malformations  and  diseases,  and  therefore  an   stout chordae tendinae; and malposition of the papillary
              echocardiogram is needed to confirm the diagnosis.  muscles that can result in valve dysfunction, primarily
                                                                 valve insufficiency (Liu 1977) (Figure 10.2).
              Treatment
              Because a dysplastic tricuspid valve is not generally ste-  Signalment
              notic in the cat, interventional (cardiac catheter, surgi-  There are no known breed predispositions.
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