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264 Dilated Cardiomyopathy

Clinical Presentation ○ Sudden cardiac death: presumptive ○ Occult DCM: often unremarkable (poor
DISEASE FORMS/SUBTYPES malignant ventricular arrhythmias • ECG
screening tool)
VetBooks.ir dysfunction and/or ventricular dilation based DIAGNOSIS ○ Normal sinus rhythm does not rule out
• Occult DCM: asymptomatic with systolic
on echocardiography and/or the presence of
presence of ventricular or atrial arrhyth-
ventricular arrhythmias.
• Diagnosis includes disease confirmation in
• Symptomatic Diagnostic Overview mias and does not rule out DCM. May
note atrial premature contractions (APCs),
○ Arrhythmias animals with clinical abnormalities and diag- VPCs, atrial fibrillation, ventricular
Ventricular arrhythmias (most common nostic screening in well dogs of commonly tachycardia
■
in boxers, Doberman pinschers) affected breeds; well cats are not routinely ○ One VPC on a 5-min ECG strongly
Atrial fibrillation (most common in the screened for DCM. warrants further examination for DCM
■
giant breeds) • Echocardiography is the current standard in Doberman pinschers.
○ CHF: left > right sided; biventricular for diagnosis of systolic dysfunction, with • Effusion analysis
possible or without dilation. DCM also causes ven- ○ Modified transudate consistent with CHF
○ Sudden cardiac death (first sign in 35% tricular arrhythmias that can result in sudden (nucleated cell count < 2500/mcL, total
of dogs) cardiac death. Gold standard screening protein < 4.0 g/dL); chylous effusion
includes an echocardiogram (p. 1094) and possible
HISTORY, CHIEF COMPLAINT Holter monitoring (24-hour ECG) (p. 1120). ○ Biventricular heart failure or severe
• Occult DCM: asymptomatic, diagnosed • Radiographs are indicated for patients with tachyarrhythmias (e.g., atrial fibrilla-
during screening examination or incidental clinical signs referable to the respiratory tion) may cause pleural and abdominal
finding system (tachypnea, dyspnea). CHF should effusion.
• Cardiac arrhythmias: lethargy, collapse/ be considered if left atrial and/or ventricular ○ Presence of only pleural effusion is unusual
syncope, weakness, precipitation of CHF enlargement, pulmonary venous congestion, presentation for CHF.
(e.g., atrial fibrillation) and/or pulmonary edema are noted. • Echocardiogram: required for definitive
• CHF: dyspnea, tachypnea, coughing, diagnosis of DCM; not required for initiating
abdominal distention (biventricular failure Differential Diagnosis therapy
or arrhythmia induced), lethargy, restlessness, • Respiratory distress (p. 1219)
weight loss • Collapse (p. 192) Advanced or Confirmatory Testing
• Pleural or abdominal effusion (pp. 79 and • Echocardiogram: ventricular and atrial dila-
PHYSICAL EXAM FINDINGS 791) tion (left > right), reduced myocardial systolic
• Auscultation: soft murmur 1/6 to 3/6 left function (decreased fractional shortening [%]
or right apical systolic, gallop heart sound, Initial Database and ejection fraction [%])
arrhythmia • Echocardiogram (see Advanced or Confirma- ○ LV internal diameter in diastole: > 49 mm;
• Pulses: hypokinetic femoral pulses, pulse tory Testing) > 99% specific for DCM in Dobermans
deficits with premature beats or atrial • Holter monitor (see Advanced or Confirma- ○ LV internal diameter in systole: > 40 mm;
fibrillation tory Testing) > 99% specific for DCM in Dobermans
2
• Findings in CHF: tachypnea, weakness, • +/− N-terminal pro-B-type natriuretic ○ End-diastolic volume index > 95 mL/m ;
cachexia, pale/cyanotic mucous membranes peptide (NT-pro-BNP) 96% specific for DCM in Dobermans
2
○ Left-sided CHF: pulmonary crackles/rales, ○ >500 pmol/L: echocardiogram recom- ○ End-systolic volume index > 55 mL/m ;
muffled lung sounds with pleural effusion mended 94% specific for DCM in Dobermans
○ Right-sided CHF: abdominal distention, • Screening recommendations vary by breed. ○ Doppler: functional mitral regurgitation
jugular pulses/distention, muffled heart and ○ Doberman pinschers: for breeding animals, common
lung sounds with pleural effusion, ventral yearly echocardiography and 24-hour • Holter monitoring
subcutaneous (pitting) edema (rare) Holter monitoring is recommended. ○ Diagnostic for DCM in Dobermans
■ Prevalence increases with age ■ >100 VPCs/24 hours
Etiology and Pathophysiology ■ Ventricular premature complexes ■ >50 VPCs/24 hours on two consecutive
• Causes of DCM (VPCs): only abnormality noted in Holters 6 months apart
○ Inherited cardiomyopathy (in many 37% of occult DCM cases • Additional case-specific testing
breeds, DCM that was previously thought Diagnosis of symptomatic animals: ○ Taurine concentration
to be idiopathic has been recognized to • CBC usually normal ■ Deficiency if < 45-50 nmol/mL (plasma)
have a genetic influence) • Biochemistry panel: usually normal or < 250 nmol/mL (whole blood)
○ Infectious myocarditis ○ Decreased total protein: if presence of large ○ Cardiac troponin I
○ Nutritional deficiency volume effusion (pleural or abdominal) ■ >0.34 ng/mL in combination with LV
○ Toxicity: doxorubicin cardiotoxicity ○ Prerenal azotemia from poor cardiac perfusion enlargement suggests an increased risk
○ Other: tachycardia induced, hypothyroidism ○ Elevated alanine aminotransferase (ALT): of sudden cardiac death
○ Idiopathic: an underlying cause is not mild, if present ○ Infectious disease testing (e.g., Chagas
identified ○ Electrolytes: especially important in titer, Lyme titer)
• Primary myocardial systolic dysfunction patients with arrhythmias. In particular,
leads to reduced cardiac output, followed hypokalemia and/or hypomagnesemia TREATMENT
by activation of various neurohormonal can exacerbate arrhythmias and/or reduce
and cytokine pathways to support blood efficacy of antiarrhythmic agents. Treatment Overview
pressure (BP) and organ perfusion. This • BP • Asymptomatic: treatment is aimed at
leads to short-term stability but long-term ○ Normal to low: systolic ≤ 100 mm Hg prolonging the preclinical period.
myocardial remodeling and enlargement with myocardial failure • Symptomatic: treatment is aimed at reliev-
(p. 408). • Radiographs ing clinical symptoms associated with
• The clinical stages of symptomatic DCM ○ Thoracic: cardiomegaly, pulmonary venous CHF (pulmonary edema and/or effusion),
are characterized by two distinct outcomes: distention, perihilar pulmonary edema, or life-threatening ventricular arrhythmias, and
○ CHF: 1-year survival rate < 10% pleural effusion significant supraventricular arrhythmias.

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