Dilated Cardiomyopathy (DCM) Part 4

Flashcards covering the pathophysiology, clinical signs, diagnosis, and treatment protocols for Dilated Cardiomyopathy in small animals.

Dilated cardiomyopathy (DCM)

The second-most common heart disease of the dog, primarily affecting large breeds, characterized by myocardial dysfunction leading to

decreased contractility

compensatory eccentric (dilated) ventricular hypertrophy.

Doberman pinscher lifetime risk

The probability of this breed developing Dilated cardiomyopathy (DCM) is $58.2\%$, which is significantly higher than other breeds like the Great Dane ($25\%$).

Secondary DCM etiologies

Non-inherited causes of the disease including

prolonged tachycardia

toxicity ($doxorubicin$)

infections ($parvo virus$)

metabolic causes

nutritional disorders such as taurine deficiency or grain-free diets.

Eccentric ventricular hypertrophy

The specific type of ventricular dilation that occurs in DCM as a compensatory mechanism for myocardial dysfunction and loss of myocyte contractility.

DCM Auscultation findings

Includes a soft (low grade) left apical murmur, gallop rhythms, and potential arrhythmias; muffled heart sounds may be heard if pleural effusion is present.

Left-sided Heart Failure clinical signs

Symptoms including

respiratory distress

pulmonary crackles

cyanosis caused by pulmonary edema.

Right-sided Heart Failure clinical signs

Symptoms such as

abdominal distention (ascites)

jugular pulses, which are less common than left-sided signs in DCM patients.

Modified transudate

The classification of DCM-related effusion cytology, defined by a total protein less than $4.0\,g/dL$ and a cell count less than $2500/\mu L$.

NT-proBNP and cardiac troponin

Blood biomarkers used as markers of myocyte damage to assist in the diagnosis and monitoring of cardiac disease.

Echo and 24-hour Holter monitoring

The gold standard diagnostic combination for DCM, used to visualize chamber dilation and identify more than $100$ VPCs in a $24$-hour period.

PROTECT study

A study demonstrating that the use of pimobendan prolongs the pre-clinical period in Dobermans and Irish wolfhounds showing evidence of systolic dysfunction.

Acute DCM treatment

Emergency management consisting of

oxygen

furosemide boluses ($IM$ or $IV$)

pimobendan

dobutamine $CRI$ for severe edema, centesis of effusions

anti-anxiety narcotics ($butorphanol$).

Beta blockers contraindication

These medications are avoided in DCM patients because of their negative inotropic effect, which would further decrease damaged myocardial contractility.

Sotalol +/- mexiletine

Medications typically used for the chronic management of significant ventricular arrhythmias in DCM patients.

Diltiazem +/- digoxin

Medications typically used for the chronic management of supraventricular arrhythmias, such as atrial fibrillation, in DCM patients.

“R on T” complexes

Rapid, overlapping VPCs seen on ECG that represent a high risk for progression into ventricular fibrillation.

Taurine

An essential amino acid in cats that they cannot synthesize; deficiency leads to secondary DCM which may have a good prognosis if the patient survives the first $2$ to $3$ weeks of supplementation.

DCM Prognosis (Cats vs. Dogs)

Grave in cats with a medium survival of $2$ weeks; in dogs, average survival is $6$ months after clinical signs, though $75\%$ of Dobermans die within $3$ months.