Diseases of the Cardiovascular System

1. Diseases of the Cardiovascular System By:Casey Conway & Jeannie Stall R.V.T. Credits: Google Images/ ClipArt Alleice Summers

2. The Cardiovascular System • Maintains homeostasis by regulating the flow of blood through vessels & capillaries • Delivers vital nutrients & oxygen into body cells & waste materials are removed • Heart (pump) circulates blood through vessels (pipes) • “Closed” system – change in one portion affects other portions of the system • Blood from heart & lungs in arteries • Veins return blood to the heart • Specialized cardiac muscles in SA node generate electrical impulses – read by ECG

3. Heart’s Blood Flow Pattern • O2-depleted blood enters R atrium via Inferior & Superior Vena Cava veins • Exits R Atrium into R ventricle via Tricuspid valve • Exits via Pulmonic valve into pulmonary artery to lungs…………… • O2- rich blood arrives from lungs, into L atrium, via pulmonary vein • Exits L Atrium via Mitral valve, into L ventricle • Exits L ventricle via Aortic valve, into Aorta & the rest of the body …………

4. Definitions: Bradycardia: Slowheart rate Tachycardia: Fast heart rate “P” wave :Atrial contraction “QRS” complex : Ventricular contraction & Atrialrepolarization “T” wave : Ventricular repolarization Atrial fibrillation: No “ P” wave d/t poor contraction Premature Ventricular Contraction (PVC’s): Wide, bizzare “QRS” complexes w/o associated “P “ waves Systole: Contraction phase Diastole: Relaxation phase

5. Heart Valve Murmurs: • Aortic: Left side of chest/dorsal mid-heart • Mitral: Left side of chest/ventral-caudal heart • Pulmonic: Left side of chest/ ventral-anterior • Tricuspid: Right side of chest/ ventral heart “Lub-Dub”= Normal heart sound Murmur = Abnormal swishing sound Gallup Rhythm: 3rd sound heard (not lub-dub), - similar to a galloping horse sound effect ie: Vent. Dilation (Dilated Cardiomyopathy) or Vent. Hypertrophic Cardiomyopathy

6. Heart Failure: When blood returning to the heart can’t be pumped out @ rate matching body’s need • Clin. signs & Tx depend on indiv. animal’s Dx • Differentiate between myocardial dysfunction (pump failure) or circulatory dysfunction (lack of circulating fluid volume) • Congestive Heart Failure –failing heart allows fluid congestion and edema to accumulate in the body

7. Canine Dilated Cardiomyopathy (DCM) • Commonly acquired K9 cardiovascular dz. • Older, large breeds/Males/ 4-10 ys. Rare in dogs < 12 kg. (less than 26.4 lb) • 4 chamber dilation caused by weak, thin & flabby cardiac muscle results in cardiac output & cardiac afterload (blood left in heart in diastole) Also, impaired systolic function of the ventricles • Effect on animal is low-output circulatory failure • Cause is unknown – Poss. viral, nutritional, Immune mediated, genetic causes ???????

8. Canine Dilated Cardiomyopathy (DCM) cont’d…… • Weakness, exercise intolerance, syncope, shock • X-rays – may show enlarged heart • Ultrasound and ECG – widened QRS & P waves • No cure exists, keep dog comfy • Rx:Diuretics– fluid load & reduce work on heart Digoxin– cardiac contractility & output Enalapril –helps vascular resistance & improve cardiac output • Most dogs die within 6mo. -2 yrs. of Dx.

9. Canine Hypertrophic Cardiomyopathy: Uncommon dz.- left ventricle muscle hypertrophies, decreased filling capacity & blocking outflow of blood during systole • Clinical signs: fatigue, cough, tachypnea, syncope, sudden death, some may be asymptomatic • Ultrasound – thickening of the left ventricle • No routine treatment • Hereditary – G. shep, Rott, Dalmation, Cocker, Boston, Shih Tzu

10. Feline Dilated Cardiomyopathy Before 1980’s, DCM was a freq. reported feline cardiac dz. • Associated w/taurine deficiency After adding taurine to commercial diets, incidence rate significantly decreased • Pathology similar to DCM in dogs • Clin. Signs: Older, mixed breed cats,dyspnea, inactivity, anorexia, acute lameness or paralysis of rear limbs, hypothermia • Dx: C/S, ECG, Ultrasound

11. Tx: oral taurine supp, Lasix, oxygen, Digoxin, Enalapril, cutaneous nitroglycerin paste (vasodilation) • Avoid iv fluid replacement – pulmonary edema/pulmonary effusion • Cats that survive first 2 weeks & respond well to taurine supp. have good prognosis- otherwise poor, long-term prognosis • Extreme caution when handling DCM cats – may die suddenly

12. Feline Hypertrophic Cardiomyopathy • Similar to K-9 HCM :Left ventric.hypertrophy • Neutered male cats most at risk • Soft, systolic murmur, gallop rhythms or other arrhythmia, acute onset of heart failure or systemic thromboembolism • Dx: X-rays, ECG, Ultrasound • Rx: Lasix Propranalol: sinus HR Diltiazem: bl. pressure & cardiac afterload HR of bpm<200=better prognosis vs. >200 bpm • Survival time ~ 2 yrs

13. Thromboembolism : Thrombus formation – common, serious complication of myocardial dz in cats • Cats have inherently high plt reactivity, making clot formation more likely with endothelial damage & sluggish blood flow w/dz • 90% of emboli lodge as “saddle thrombi” in distal aortic trifurcation • Other sites may be renal artery, coronary arteries, cerebral arteries, mesenteric artery

14. “Saddle Block” Thromboembolism To Heart To Rear Legs Photo credit: petmd.com

15. Clinical signs: acute onset of rear leg pain & paresis, cold bluish foot pads, lack of palpable rear limb pulses, Hx or clin. signs of myocardial dz. • Dx: clincial signs • Tx: TPA (fibrolysin): +/- benefit ? , $$$$$ Heparin: some benefit Prophylactic Tx: Aspirin(can cause toxicities) MUST DOSE CAREFULLY !!! Surgical removal is difficult • Prognosis: guarded to poor NOTE:Emerg. exam when clin.signs seen!

16. Patent DuctusArteriosus • Congenital defect where ductusarteriosus fails to close after fetus is born. As fetus, ductus transports blood from pulm. artery to aorta. At birth, increased O2 tension in blood causes ductus to close during 1st 12-14 hours of life. With ductus left open, blood floods lungs & L side of heart overloads. Cardiac murmur heard is “machinery” murmur Listen over pulmonary artery location- (L side/ low on anterior heart)

17. Atrial and Ventricular Septal Defects • In fetus, atria & vent. develop as a common chamber, but eventually the ventricular septum & the atrial septum develop to separate chambers • Septum defects create patencies (openings) • Fairly common in the cat • ASD(atrialseptal defect)– blood typically shunts from left to right, overloading the right side of the heart • VSD(ventral septal defect)– left side of the heart is overloaded & enlarged • Clin. signs:Congestive heart failure before 8 wks. old • Dx: X-rays, Echocardiogram • Tx: Medical management of CHF Open-heart Sx required to repair defect– rarely done

18. Atrial and Ventricular Septal Defects Normal Heart Ventricular Septal Defect

19. Stenotic Valves Pulmonic and Aortic Stenosis • Lesion in pulmonic valves narrows the outflow tract of the right ventricle – increase in vent. systolic pressure causes R ventricular hypertrophy • R atrium also becomes enlarged • Severe stenosis(narrowing) limits cardiac output during exercise • Clin.signs – breed predilection > 1yr, syncope, R-sided CHF, prominent jug.pulse • DX: X-rays, ECG • Tx: Sx. (“balloon” to relieve/remove obstruction) Medical mgmt of CHF • Sudden death may occur Genetic- Don’t breed

20. Chronic Mitral Valve Insufficiency : Most common K-9 cardiovascular disorder (rare in cats) Sm-toy breeds, >10 yrs old, males, • Lesion on the structures of the valve leaflets (nodular thickening of the edges, contract & roll up, creating failure to close sufficiently during systole causing regurgitation of blood back into L atrium) Etiology: Periodontal dz.-tartar’s bacteria gets into bloodstream, colonizes valve leaflets & thickens them

21. Clin. Signs: Pulmonary congestion, dyspnea, deep cough(worse w/exercise or @ night) systolic murmur w/”whooping” quality • Dx: X-rays, ECG • Tx: Med. management only improves length & quality of life - NO CURE Rx Diuretics, arterial dilators, Digoxin (decreases HR) • Progressive dz.= Will reach point when meds don’t relieve clinical symptoms

22. Tricuspid Valve Insufficiency • Exactly like Mitral valve insufficiency • Clin. Signs: As in R-sided heart failure: Pleural effusion, abdominal distension, hepatomegaly, GI signs – V,D, anorexia • Tx: Same as CMVI, may require abdominocentesis

23. Sinus Arrhythmia: • Normal occurrence in dogs but NOT cats • Heart rate increases on inspiration & decreases upon expiration

24. Sinus Bradycardia • Commonly seen in: lg-breed dogs, athletic or highly conditioned animals & brachiocephalic dogs during anesthesia • ECG is normal with HR < 70 bpm • Can be seen w/ increased ICP, hyperkalemia, hypothyroidism, GI disturbances, drugs • Typ. no clin. signs unless HR drops very low • Episodic weakness, syncope, collapse • Auscultation, ECG • No Tx unless clinical signs, atropine, placement of an artificial pacemaker

25. Canine Heartworm Dz. Female mosquito = intermediate host In taking a blood meal from HW infected dog, she sucks up Dirofilariaimmitismicrofilaria. Microfilaria stay 2-2 ½ weeks in mosquito then enter victim’s skin (dog #2) via mosquito’s bite. Larvae migrate in tissues for ~ 100 days. L5 stage enter vessels & migrate to pulmonary artery where they mature into adult HW. ~ 6 mo. Post-initial bite, new microfilaria detected

26. HW Damage : • Adult Hw harm endothelial lining of pulmonary artery & ‘s vessel’s permeability, “leaking” fluid & protein into perivasc. tissue Worms block outflow of blood from , creating R-sided heart enlargement & pulm. hypertension Clin. signs: In later stages- Cough/dyspnea/ exercise intolerance/hemoptysis (coughing up blood), R-sided heart failure

27. Dx: • Difil Filter test- Not used much now • Modified Knott’s test- 2% Formalin/Centrifuge/New Meth. Blue/microscope • Direct-Fresh drop of whole blood/microsope/Look for movement in RBC’s- Dirofilariaimmitis- thrashes NOTE: Dipetalonemareconitum- swims across slide ( K-9 SQ parasite, not heartworm!!!!!) SNAP test- Heartworm antigen test- > % accuracy Req’s snap test & sm. amt. of sample = fast results

28. HW Treatment: • After + test, protocol includes CBC, chem. panel, thoracic radiographs(edema/enlarged) • Prev. med: Caparsolate – harsh effects • Currently: Immiticide – less harsh effects seen ( melarsaminedihydrochloride ) Tx adults= 2 injections given deep into lumbar muscle @ 24 hr. interval /Strict activity restriction post-inj./ K/D diet eases liver strain Side effects: Resp. distess/V/D/panting/drool Tx microfilaria= 3-6 wks post-inj. of Immiticide (Ivermectin-Heartgard) or ( Milbemycin-Sentinel)

29. H/W Cases

30. Feline HW dz: • Prev. thought cats “safe”........Not anymore.. • Cats have lower # of adult worms & are usually - for microfilaria Adult Hw eliminated from host cat w/i 2 yrs. Clin. signs: Freq. asymptomatic/sudden death/ resp. issues ie: cough/dyspnea / GI tract issues ie: vomiting/anorexia/lethargy ataxia/blindness/seizure/wt.loss/R-sided CHF Tx: N/A due to toxicity issues Now advise Prevention via monthly Revolution

31. HEARTWORM PREVENTATIVE MEDICATION: Heartgard Plus: Ivermectin/Pyrantelpamoate - HW/Rds/Hks Interceptor: Milbemycin - HW/ Rds/Whips/Some Hks Sentinel:Milbemycin/Lufenuron – HW/Rds/Whips/S. Hks/Flea eggs K-9 Revolution: Selemectin – HW/Fleas & eggs/ear mites/ Sarcoptes mange/Amer. Dog Ticks Fel. Revolution:Selemectin – HW/Fleas & eggs/ ear mites/ One type of Rds. & Hks K9 Advantage Multi:Moxidectin/Imidacloprid-HW/Fleas/ Rds/Hks/Whips Fel.Adv.Multi:Moxidectin/Imidacloprid-Hw/Fleas/Rds/Hks/ Ear Mites

32. Valvular Disease – Equine • Common in foals (congenital) or in mature horses (degenerative or infectious) Dz’d valves impede normal flow (stenosis) or allow backflow (insufficiency), which increases heart’s workload & decreases cardiac output Clin.signs: Murmur, exercise intolerance, fever, wt. Off & on lameness, arrhythmias, developing CHF • Dx: Exam, ECG, Echo, exercise test, Halter monitor • Tx & Prognosis: depends on symptom’s severity & lesion location: Tricuspid, Mitral & Aortic valve regurgitation prognosis generally good. Endocarditis prognosis generally poor • Don’t ride these horses!! – Sudden death issue !!

33. Vascular Disease – Equine • Vascular disorders seen in horses: • Thrombophlebitis d/t cath. Placement / IV inj. • Parasitic thromboemboli in mesentery arteries • Vascular rupture Thrombophlebitis: Heat, pain swelling at site over vein, fever. – High doses of br.sp abx based on cult, hot compresses, sx resection Parasitic: Vessel damage not reversable. Recurrent colic signs. Req. good deworming plan ie: Ivermectin Vascular rupture: Anurysm = Sudden death. No time for Tx. since sudden death is only sign.

34. The End….