Cardiomyopathy

Cardiomyopathy



Basic Information image



Definition


A myocardial disease process resulting in decreased myocardial function. In horses, this often results in dilation and decreased contractility, which can lead to congestive heart failure, arrhythmias, or both. Myocarditis is often a precursor to cardiomyopathy.



Synonym(s)


Dilated cardiomyopathy



Epidemiology



Risk Factors


Any cause of myocarditis that does not completely resolve has the potential to progress to cardiomyopathy (see “Myocarditis” in this section).



Geography and Seasonality


Cardiomyopathy associated with selenium deficiency is most common in young horses (see “Myocarditis” in this section).



Clinical Presentation



Disease Forms/Subtypes


Acute, subacute, and chronic: These subtypes have not been well characterized in horses.



History, Chief Complaint




• Exercise intolerance


• Signs of left-sided heart failure: Tachypnea, dyspnea, cough, nostril flare, weakness


• Signs of right-sided heart failure: Jugular pulses, jugular distension, edema, abdominal distension


• Syncope, sudden death



Physical Exam Findings




• Tachycardia, arrhythmias, gallop rhythm


• Cardiac murmurs


• Tachypnea, dyspnea, nostril flare, cough


• Exercise intolerance


• Weak pulses, jugular pulses, jugular distention, ventral (pectoral) edema


• Abdominal distension


• Syncope


• Nonspecific signs include weight loss (cardiac cachexia), depression, anorexia, weakness



Etiology and Pathophysiology




• Causes of myocarditis that become chronic may progress to cardiomyopathy.


• Most often leads to decreased systolic function and chamber dilation, with subsequent arrhythmias.


• Arrhythmogenic right ventricular cardiomyopathy is also seen in horses, rarely.



Diagnosis image



Differential Diagnosis




• For exercise intolerance, lethargy, weakness, weight loss: Abnormalities in respiratory, neuromuscular, gastrointestinal systems


• For arrhythmias: Arrhythmias secondary to severe valvular or congenital heart disease with cardiac enlargement; systemic disease; electrolyte abnormalities


• For heart failure: Primary valvular, pericardial, or congenital heart disease


• For respiratory signs: Primary pulmonary or pleural disease



Initial Database




• The complete blood count may be normal or may show characteristics of concurrent disease.


• Chemistry panel: Changes consistent with passive congestion from right-sided heart failure (increased liver enzymes) or changes consistent with organ dysfunction caused by decreased cardiac output (azotemia). Elevations in creatine kinase in horses with selenium deficiency may be seen. Elevations in lactate associated with poor tissue perfusion may be seen.


• Thoracic radiography: Evidence of pulmonary edema (interstitial or alveolar pattern may be seen), cardiomegaly, pleural effusion.


• Electrocardiogram (ECG): Sinus tachycardia with any additional arrhythmias.


• Echocardiogram: Will show evidence of dilated cardiomyopathy, including dilated atria and ventricles possibly with thin walls, decreased systolic function (low fractional shortening), spontaneous contrast indicating a low flow state, and distended pulmonary artery suggesting pulmonary hypertension. The left ventricle will appear hypokinetic, with an increased septal–E point separation. Doppler evaluation may show valvular regurgitation. There may be evidence of infiltrative cardiomyopathy (thick walls, heteroechogenicity of myocardium) (Figure 1).


• Cardiac troponin I: Likely elevated in cases of cardiomyopathy associated with active myocardial necrosis.


image

FIGURE 1 Right-sided parasternal longitudinal four-chamber echocardiographic view of a horse with cardiomyopathy secondary to monensin intoxication. Note the thick heteroechoic myocardial walls from active inflammation and the mild pericardial effusion. Systolic function was significantly decreased. This scan was acquired at 1.5 MHz and a depth of 30 cm.

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Cardiomyopathy

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