DISEASES OF THE CARDIOVASCULAR SYSTEM

The right side of the heart: Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart As the atrium contracts, blood flows from the right atrium into the right ventricle through the open tricuspid valve When the ventricle is full, the tricuspid valve shuts. This prevents blood from flowing backward into the atrium while the ventricle contracts As the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated Inferior (caudal vena cava) Superior (cranial vena cava) Pulmonary artery: carriers unoxygenated blood (switched in this case) – This leads right into the lungs

The left side of the heart: The pulmonary vein empties oxygen-rich blood from the lungs into the left atrium of the heart As the atrium contracts, blood flows from the left atrium into the left ventricle through the open mitral valve When the ventricle is full, the mitral valve shuts. This prevents blood from flowing backward into the atrium while the ventricle contracts As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the body (switched again-oxygen-rich blood through the vein)

Flow of the heart: https://www.youtube.com/watch?v=lt7Tj_KGTNE

CANINE DILATED CARDIOMYOPATHY: Dilated cardiomyopathy (DCM) is a disease of the heart muscle that is characterized by an enlarged heart that does not function properly. Both the upper and lower chambers of the heart become enlarged, with one side being more severely affected than the other. When the ventricle becomes enlarged, its ability to pump blood out into the lungs and body deteriorates. Could lead to Congestive heart failure When the heart’s ventricle does not pump enough blood into the lungs or body, fluid begins to accumulate in the lungs. An enlarged heart soon becomes overloaded, and this often leads to congestive heart failure (CHF)- a chronic progressive condition that affects the pumping power of your heart muscles (BOTH SIDES ARE AFFECTED) Usually affects both sides, one might be worse than the other (usually the left side)

MOST COMMON ACQUIRED CARDIOVASCULAR DISEASE IN DOGS Heart is larger, looks stretched, walls are thin and flabby (dilation) THE WALLS OF THE HEART ARE WEAK, FLABBY, AND DILATED MOST COMMON ACQUIRED CARDIOVASCULAR DISEASE IN DOGS

CANINE DILATED CARDIOMYOPATHY The cause of DCM in dogs is largely unknown. Nutritional deficiencies of taurine or carnitine (amino acid ) have been found to contribute to the incidence of DCM in certain breeds such as Dobermans and Cocker Spaniels. Evidence also suggests that some breeds have a genetic susceptibility to the disease. In most breeds, male dogs are more susceptible to the disease than female dog 90% of cases occur in Doberman Pinschers and Boxers OTHER BREEDS INCLUDE WOLFHOUNDS, GREAT DANES, AND COCKER SPANIELS

CANINE DILATED CARDIOMYOPATHY: PATHOPHYSIOLOGY DECREASED CONTRACTILITY from an unknown cause (viral?, carnitine deficiency?) Decreased contractility = decreased overall cardiac output CO (CARDIAC OUTPUT) = SV (STROKE VOLUME) X HR (HEART RATE) Causes: Virus, bacterial, nutrition, immune-mediated. Carnitine-amino acid (burns fats to create usable energy) If there is a deficiency it interferes with the processing of food (Specifically fat). The dilation results in decreased cardiac output and increased cardiac afterload (blood left in the heart). In this case the stroke volume is decreased because less blood is leaving the heart due to the dilation. Amt. of blood ejected with Each cardiac contraction (affected by afterload, preload, and inherent contractility) How often the heart contracts The amt. of blood that leaves The heart in a given unit of time

CANINE DILATED CARDIOMYOPATHY: THE BODY COMPENSATES BY: 1. INCREASING THE HEART RATE *this is done by sympathetic nervous system stimulation 2. TRYING TO INCREASE STROKE VOLUME BY INCREASING PRELOAD (this means that the body increases filling of the heart) *This is done by retaining sodium and water Stroke volume: how much blood leaves the heart. The body increases how much it fills the heart in hopes that it will increase the stroke volume, resulting in more blood being pumped out, although this just leads to backed up blood in the heart and lungs. Retaining sodium and water results in an increased blood volume.

CANINE DILATED CARDIOMYOPATHY: CLINICAL SIGNS Physical exam can find: pulse deficits, ventricular premature contractions and slow capillary refill time. The dog’s breathing sounds may also have a muffled or crackling sound due to the presence of fluid in the lungs PLEURAL EFFUSION: a buildup of fluid between the tissues that line the lungs and the chest ASCITES: the accumulation of fluid in the peritoneal cavity, causing abdominal swelling LETHARGY, EXERCISE INTOLERANCE, COUGHING, TACHYPNEA, SYNCOPE, SOFT MURMUR, PLEURAL EFFUSION, ASCITES, HEPATOMEGALY

Normal Echocardiogram

Canine Dilated Cardiomyopathy Echocardiogram Much faster and the valves are flapping all over. (EKG) may reveal atrial fibrillation and ventricular tachycardia (rapid beating of the heart)

CANINE DILATED CARDIOMYOPATHY: ECHOCARDIOGRAM PERFORMING AN ECHOCARDIOGRAM IS THE DEFINITIVE WAY TO DIAGNOSE DILATED CARDIOMYOPATHY Can also be diagnosed with: Radiographs Electrocardiogram (ECG) Stress test would NOT give an accurate diagnosis(doesn’t work well with animals) An ultrasound of the heart using echocardiograph imaging is required for a definitive diagnosis of DCM. This test examines the size of the heart, and the ability of the ventricles to contract. In the case of DCM, an echocardiograph will reveal an enlarged left ventricular and left atrial, and low contraction ability A stress test shows how the heart works during physical activity

CANINE DILATED CARDIOMYOPATHY Radiographs may be normal early in the disease process. May show enlarged heart later in the disease process. Enlarged, round heart

CANINE DILATED CARDIOMYOPATHY PULMONARY EDEMA: A condition caused by excess fluid in the lungs (Left side of the heart) PLEURAL EFFUSION: A buildup of fluid between the tissues that line the lungs and the chest (Right side of the heart) PLEURAL EFFUSION PULMONARY EDEMA PATIENT MAY SHOW SIGNS OF LEFT-SIDED, RIGHT-SIDED, OR HEART FAILURE FROM BOTH SIDES

PULMONARY EDEMA VS PLEURAL EFFUSION Pulmonary edema is the accumulation of fluid in the ALVEOLI of the lungs Causes dyspnea due to air being displaced by fluid Left sided heart failure Pleural effusion is the accumulation of fluid in the pleural space OUTSIDE of the lungs Causes dyspnea due to lungs not being able to expand fully Right-sided and congestive heart failure Seen more in large breeds 4-10 years old-DCM Know right sided vs. left sided heart failure

CANINE DILATED CARDIOMYOPATHY: PATHOPHYSIOLOGY Constant stimulation of the heart by the sympathetic nervous system causes ventricular arrhythmias and myocyte death Most common arrhythmias: VPC’s and ventricular tachycardia, esp. in boxers & Dobies; other dogs may have APC’s and atrial fibrillation ONE VPC Myocyte: muscle cell VPC’s: Ventricular premature comtractions occur when the lower chambers of your heart contract before they should. When this happens, the heartbeat becomes out of sync APC’s: Atrial premature complex: arrhythmia characterized by premature heartbeats originating in the atria Atrial Fibrillation: An irregular, often rapid heart rate that commonly causes poor blood flow MULTIPLE VPCs CAUSING TACHY-CARDIA

CANINE DILATED CARDIOMYOPATHY: DIAGNOSTICS Laboratory tests Atrial Natriuretic peptide increase Released from atria in response to excess stretch Brain natriuretic peptide increase released from ventricles in response to excess stretch Pro-BNP release Troponin 1 (cTn1) increased Released when heart muscle is damaged The atrial natriuretic (ANP) is a cardiac hormone. Its main function is to lower blood pressure (found in body, but increased due to trying and compensating) Brain natriuretic peptide (BNP), is a hormone secreted by cardiomyocytes in the heart ventricles in response to stretching caused by increased ventricular blood volume (due to increased blood sitting in the ventricle) Troponin 1: protein found in cardiac muscle, it is released when there is cardiac damage.

CANINE DILATED CARDIOMYOPATHY: TREATMENT INCREASES CONTRACTILITY DIGOXIN FUROSEMIDE CONTRACTILITY: strength of contractions REDUCES FLUID RETENTION ENALAPRIL DIURETIC-ELIMINATES EXCESS FLUID

CANINE DILATED CARDIOMYOPATHY: TREATMENT COENZYME Q10: Provides energy to cells. Taurine: It helps eliminate cholesterol, maintains normal blood pressure, and acts as a powerful antioxidant L-CARNITINE: the production of energy by transporting fatty acids into your cells L-CARNITINE COENZYME Q10 TAURINE – USED IN COCKER SPANIELS AND CATS, MAINLY DIETARY SUPPLEMENTS THAT MAY HELP IMPROVE HEART FUNCTION, ESP IF THERE IS A DEFICIENCY

CANINE DILATED CARDIOMYOPATHY: CLIENT INFO DCM is a progressive diseases that is almost always fatal Most dogs die within 6 months -2 years Death may occur suddenly due to arrhythmias

CANINE DILATED CARDIOMYOPATHY https://www.youtube.com/watch?v=w5f34rHvs78 Introduction to veterinary cardiomyopathy (DOVE) 5 mins Placing holter monitor (DOVE) 5 mins

FELINE DILATED CARDIOMYOPATHY A globular-shaped heart with severe dilation of all four chambers. Depressed ventricular contractile performance occurs. Ventricular dilation distorts the atrioventricular valves leading to mitral regurgitation and atrial enlargement Starts in the ventricles ABNORMALLY THIN VENTRICULAR WALLS

FELINE DILATED CARDIOMYOPATHY In the 1980’s DCM in cats was one of the most commonly diagnosed heart diseases. It was discovered that this was caused by a deficiency of TAURINE, an amino acid. Since that time commercial foods have added taurine to feline diets, which has significantly decreased the number of cases of feline DCM Cats that do not respond well to taurine supplements, have a poor prognosis. Taurine: It helps eliminate cholesterol, maintains normal blood pressure, and acts as a powerful antioxidant Overall: it is caused by a nutritional deficiency