Myocardial Disease I Lecture Slides PDF

Myocardial Disease I: Canine Cardiomyopathy Lauren Markovic, DVM, DACVIM (Cardiology), FACVIM (Interventional Cardiology)  Learning Objectives Be able to describe the following for dilated cardiomyopathy Pathophysiology of this disease and how the disease lead...

Myocardial Disease I: Canine Cardiomyopathy Lauren Markovic, DVM, DACVIM (Cardiology), FACVIM (Interventional Cardiology)  Learning Objectives Be able to describe the following for dilated cardiomyopathy Pathophysiology of this disease and how the disease leads to heart failure Appropriate diagnostic testing including top two echocardiographic findings Etiologies for primary and secondary dilated cardiomyopathy phenotype and differential diagnoses Understand what type of clinical signs and examination findings can be seen in the patient with canine cardiomyopathy, with and without congestive heart failure (CHF) Understand appropriate therapies for CHF secondary to myocardial failure Understand breed predisposition for dilated cardiomyopathy Canine Cardiomyopathy – Case Study Samantha 6 yo FS Doberman Pinscher 2 week history of coughing, lethargy and exercise intolerance – progressive 24 hour history difficulty breathing, inappetence and syncope  Samantha – Physical Exam RR 70br/min HR 300bpm Temp 99.5 F MM: pale pink, dry Distended jugular veins Bilateral pulmonary crackles III/VI left apical systolic murmur Weak femoral pulses  Samantha… What is the cause of her arrhythmia? Is this an emergency? What are the signs of congestive heart failure? What are differential diagnosis for left heart failure in this dog? List radiographic and echocardiographic abnormalities?  Canine Cardiomyopathy Primary disorder of the cardiac muscle Dilated cardiomyopathy (DCM) Arrhythmogenic right ventricular cardiomyopathy (ARVC) Secondary disorder of the cardiac muscle Nutritional deficiency Infectious / myocarditis Drug-induced, toxin Tachycardia-induced DDx: myocardial failure due to chronic insult from other primary cardiac disease (end-stage volume-loading valvular disease, congenital left to right shunt)  Dilated cardiomyopathy (DCM) DCM - Pathology Four chamber enlargement Left sided worse than right Walls thin to normal, valves normal Myocardial fibrosis  Pathophysiology Systolic dysfunctionà decreased stroke volume Hypotension and activation of sympathetic nervous system and renin-angiotensin-aldosterone- system (RAAS) Secondary (functional) valvular regurgitation due to annular stretch Cardiac chamber dilation (profound left atrial and ventricular dilation) Increased atrial pressure à pulmonary edema (or ascites if right involvement) Arrhythmias can be due to atrial stretch or ventricular ischemia Atrial fibrillation, ventricular tachycardia  Pathophysiology Systolic dysfunction & increased LA pressureà Pulmonary edema/left CHF  Clinical findings – DCM Review Samantha’s clinical signs… Compensated Murmur, systolic apical (L or R) Gallop (S3 due to ventricular dilation) Weak femoral pulses Arrhythmias with pulse deficits Decompensated Left congestive heart failure (CHF) Tachypnea Cough Tachycardia Crackles Right CHF Ascites, distended jugular veins, muffled heart sounds, tachycardia Degenerative valve vs. DCM? What are differentiators based on physical exam?  Radiographic findings Generalized cardiomegaly Prominent left atrial enlargement Left ventricular enlargement L CHF: Distended pulmonary veins Interstitial or alveolar infiltrates R CHF: Distended caudal vena cava Pleural effusion Ascites DCM + RCHF  Electrocardiography Tall R waves: left ventricular enlargement Tall or wide P waves: Right or left atrial enlargement Atrial fibrillation is common Ventricular arrhythmias: VPCs or VT Sudden cardiac death Tachycardias may contribute to CHF  Breed predisposition - DCM More commonly diagnosed in large dogs Doberman Pinscher Great Dane Irish Wolfhound American Cocker Spaniel Boxer Juvenile Portuguese Water Dog  Echocardiography Chamber dilation with LV Systolic dysfunction LA Normal DCM RV RV RA LV LV LA LA  Echocardiography Systolic mitral regurgitation (MR) MR is functional Typically central jet LA enlargement LV eccentric hypertrophy Echocardiography – Left atrial dimension 2-Dimensional image Ao LA  Systolic dysfunction Measure fractional shortening (%) Decreased FS < 25% Degenerative valve vs. DCM? What are differentiators of these diseases on echo?  Acute therapy – Congestive heart failure Oxygen supplementation IV furosemide (decrease preload) Pimobendan (PO), dobutamine (IV) (increase contractility) +/- sedation +/- afterload reducer (nitroprusside)  Chronic CHF therapy Furosemide Loop diuretic Enalapril or benazepril ACE-inhibitor Pimobendan Inodilator Spironolactone Aldosteone antagonist  Day 1 CHF Follow-up Recheck visit 5-7 days Thoracic radiographs Renal panel Blood pressure +/- ECG 1 week post therapy  Additional diagnostic testing to consider 24 hour ambulatory (Holter) Ambulatory event monitor Serum biochemistries, PCV/TS (or CBC) +/- U/A  Antiarrhythmic therapy – Ventricular tachycardia Lidocaine (first choice in dog) IV bolus (dog 2mg/kg) IV bolus effects are short lived Follow with a CRI (dog 50 – 75 mcg/kg/min) Check serum electrolytes Ventricular Tachycardia, HR 300 bpm  Lidocaine toxicity Do not exceed 8mg/kg IV over 30 min Toxicities can result Gastrointestinal Tremors Seizures  Ventricular tachyarrhythmias - Acute Other acute anti-arrhythmic options if lidocaine is unsuccessful Procainamide IV Magnesium sulfate or Magnesium chloride Esmolol Amiodarone (large side effect profile)  Ventricular tachyarrhythmias - Chronic Sotalol – potassium channel blocker and beta blocker (caution if heart failure or systolic dysfunction) Mexiletine – sodium channel blocker Sotalol + Mexiletine combination therapy Amiodarone – potassium channel blocker (to a lesser extent class I, II, IV effects)  Therapy - Atrial fibrillation (AF) AF is seldom reversible, due to damaged atrial myocardium Goal: slow transmission of atrial impulses to the ventricle, and thereby bring ventricular contraction rate to within reasonable range – this involves giving medications that cause (controlled) AV block, “HEART RATE control” Medications Diltiazem +/- Digoxin (can use together as combination therapy) Beta blocker Therapy - RCHF  Specific cases - DCM Doberman Pinscher DCM Breed screening for occult disease Younger dogs 3-4 years of age 24 hour Holter testing Guidelines: >300 VPC in 24h or 2 Holters with >50-300 VPC in 24h 50-100 VPC in 24h – recheck Holter Echocardiogram Genetic testing (NCSU) mutation – pyruvate dehydrogenase 4 (PDK4) American Cocker Spaniel DCM May be associated with taurine deficiency Late 20th century DCM may cause CHF in this breed Meaure whole blood taurine Normal 200-350 nmol/L Affected Cocker Spaniels < 30 nmol/L Treatment: supplementation with taurine, treat if in heart failure  Diet associated DCM Nutritionally based cardiomyopathy occurs in some dogs Clinical and echo-improvement in some after diet-change Role of taurine supplementation despite normal blood concentrations is unknown at this time  Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) “Boxer Cardiomyopathy” Primary disease of heart muscle Arrhythmias, syncope, sudden cardiac death Inherited disease, adult onset (6 years of age) Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) 3 forms 1) Asymptomatic ventricular arrhythmias Noted during physical exam Monitor for progression 2) Symptomatic ventricular arrhythmias Syncope First sign may be sudden death 3) Ventricular arrhythmias with Congestive heart failure  ARVC ARVC Pathology Fibrofatty replacement and loss of normal myocardial tissue Close resemblance of pathological features of ARVC in humans  ARVC Echocardiogram may be normal 24h Holter monitor Diagnosis if 2 of 3 of the following in a 24h-ECG 1) ≥ 100 VPCs in 24 hours 2) Presence of couplets (VPC) 3) R-on-T phenomenon Questions