PATHOLOGY OF THE CARDIOVASCULAR SYSTEM

PATHOLOGY OF THE CARDIOVASCULAR SYSTEM Lecture 5: Vascular System Shannon Martinson, 2018 VPM 2220 Systemic Pathology II http://people.upei.ca/smartinson/

VASCULAR SYSTEM The vascular system is formed by: Arteries Arterioles Capillaries Venules Veins Lymphatic vessels are also considered part of the vascular system Tunica media Tunica intima Microcirculation or systemic capillary bed is formed by the arterioles, capillaries and venules Capillaries are where the actual exchange between blood and tissue takes place Tunica adventitia

VASCULAR SYSTEM RESPONSE TO INJURY Edema / congestion Hemorrhages Thrombosis Ischemia / Infarcts

VASCULAR SYSTEM Arteriosclerosis Atherosclerosis Arterial hypertrophy Hardening of the arterial wall with loss of elasticity +/-reduced vascular lumen Aneurysms Arterial medial calcification Fibrinoid necrosis Vasculitis

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Arteriosclerosis Arteriosclerosis is a degenerative (aging) change that results in hardening of the artery: Loss of arterial elasticity Luminal narrowing Arterial calcification Normal Aorta Arteriosclerosis Mainly found in elastic arteries Aorta Arterial branching sites are commonly affected Turbulence may play a role Grossly, the intima has raised corrugated white plaques Often become mineralized Histologically, fibrosis in the intima and smooth muscle hypertrophy in the media Typically no clinical significance Noah s Arkive Cow, Johne s Disease

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Atherosclerosis Dog Refers to the formation of cholesterol plaques (= atheromas) in the intima and media of arteries Large elastic arteries and medium arteries Common in humans Coronary artery heart attack Carotid / cerebral arteries stroke Rare in animals In dogs it occurs as a result of cholesterolemia: Hypothyroidism Diabetes mellitus Hyperlipoproteinemia In pigs, psittacine birds and pigeons: If fed a high lipid diet Aged psittacines Noah s Arkive

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Atherosclerosis Dog Gross: Prominent thick yellow white arteries Histology: Plaques in the intima and media Composed of foamy lipid-laden macrophages, cholesterol clefts, fibroblast and smooth muscle proliferation Pathology of Domestic Animals, Elsevier, 2016

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Atherosclerosis Lovebird History of weight loss Died Major arteries hard and rigid on postmortem exam

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Atherosclerosis Significance? Hard to say Commonly found in parrots with no associated clinical signs Lipid-laden macrophages

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Arterial hypertrophy Normal pulmonary artery Hypertrophic pulmonary artery Occurs in muscular arteries Characterized by hypertrophy of the smooth muscle (medial hypertrophy) Results in loss of elasticity and occlusion of the arterial lumen Often caused by systemic hypertension (eg. chronic kidney disease) or volume flow

Arterial hypertrophy VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Brisket Disease Pulmonary Artery: moderate hypertrophy of the smooth muscle High altitude Chronic alveolar hypoxia Pulm arterial constriction Medial hypertrophy Vasc resistance RV hypertrophy RHF

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Arterial hypertrophy In cats Medial hypertrophy is common in the lungs of cats Possibly normal in this species Aelurostrongylus abstrusus? Identical lesions are found in SPF cats Dirofilaria immitis in cats and dogs can cause both smooth muscle hypertrophy and intimal proliferation (endarteritis)

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Aneurysms Refers to a localized weakening and dilation of blood vessels Particularly elastic arteries and to a lesser extent veins Two main anatomic types of aneurysm: Saccular aneurysm: Spherical dilation of the blood vessel resembling a balloon filled with blood Dissecting aneurysm A tear of the intima allows blood to enter into the potential space between the intima and media, progressively dissecting the wall of the vessel http://www.rwjuh.edu/brain-aneurysm/brain-aneurysm-overview.aspx Aneurysms are prone to rupture and cause hemothorax, hemoabdomen, hemopericardium, etc

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Aneurysms Horse, cranial mesenteric artery, Strongylus vulgaris larval migration The most common causes of aneurysms in domestic animals are: Strongylus vulgaris in horses Cranial mesenteric artery Aorta Spirocerca lupi in dogs Aorta Copper deficiency in mare and pigs Uterine artery (mare) Trauma Pathology of Domestic Animals, Elsevier, 2016 Occasional see spontaneous aortic rupture +/- dissecting aneurysm: Stallions Turkeys Dog, aorta, Spirocerca lupi larval migration *

VASCULAR SYSTEM DEGENERATIVE DISEASES OF ARTERIES Arterial Medial Calcification Causes of medial mineralization Hypervitaminosis D Iatrogenic Calciferol rodenticides Toxic plants (Solanum, Cestrum) Granulomatous disease Johne s disease Tuberculosis Uremia Arteriosclerosis

Fibrinoid Necrosis VASCULAR SYSTEM NECROSIS / VASCULITIS Refers to the vascular necrosis with the microscopic deposition of acidophilic proteinaceous material in the walls of arteries/arterioles Fibrinoid necrosis is associated with: Viral infections: CSF, PCV-2, MCF Toxic conditions: Uremia and mercury poisoning Bacterial toxins: Enterotoxemia, Edema disease of swine (E. coli)* Nutritional deficiencies: Mulberry heart disease* Purpura hemorrhagica in horses: Streptococcus equi Immune mediated vasculitis: Systemic Lupus erythematosus Eosinophilic material is a mix of fibrin, antibodies, complement and platelets

Fibrinoid Necrosis VASCULAR SYSTEM NECROSIS / VASCULITIS Mulberry Heart Disease Bacterial sepsis (H. parasuis, Strep suis) is the major differential

Fibrinoid Necrosis VASCULAR SYSTEM NECROSIS / VASCULITIS Mulberry Heart Disease Vitamin E / Selenium deficiency in pigs fibrinoid necrosis and thrombosis of small vessels hemorrhage and necrosis in the heart

Fibrinoid Necrosis VASCULAR SYSTEM NECROSIS / VASCULITIS Hemolytic E coli Edema Disease Some strains of hemolytic E coli produce cytotoxins target endothelial cells fibrinoid necrosis edema

Vasculitis VASCULAR SYSTEM VASCULITIS Refers to inflammation of the blood vessels (small arteries and veins) Consequences of vasculitis: Hemorrhage Edema Thrombosis Infarcts DIC Fungal rumenitis Common causes of vasculitis include: Systemic infections (virus, bacteria, fungi) or toxins Hypersensitivity reaction/ autoimmune reactions Ag-Ab complex deposition Adverse drug reactions Feline Infectious Peritonitis PCV-2 Noah s Arkive

VASCULAR SYSTEM VASCULITIS Vasculitis Consequences of vasculitis: Hemorrhage Edema Thrombosis Infarcts DIC DIC: Disseminated Intravascular coagulation Highly fatal condition resulting from the formation of fibrin clots in microvasculature Ischemic necrosis Consumptive coagulopathy Results in hemorrhage Several potential underlying causes including diseases that cause vasculitis Sepsis Systemic viral disease Heartworm disease

Arteritis VASCULAR SYSTEM VASCULITIS Strongylus vulgaris Verminous arteritis Larvae (L4) migrate in the wall of the aorta and mesenteric artery Damages the wall of the vessel inducing inflammation Adult worm lives in the small intestine

Arteritis VASCULAR SYSTEM VASCULITIS Dirofilaria immitis Heartworm Disease Parasite of dogs Adult worms live in the pulmonary arteries Infections are often asymptomatic Detected on routine blood testing Heavy infections can back up into the RV and vena cava Occasionally infects cats, wild felids and canids, ferrets, etc. Often produce no or few microfilariae Can be difficult to diagnose on routine testing

JPC SYSTEMIC PATHOLOGY CARDIOVASCULAR SYSTEM, May 2013 C-P03 Arteritis VASCULAR SYSTEM VASCULITIS Dirofilaria immitis Heartworm Disease Adults in lumen of Pulmonary arteries Proliferative endoarteritis and arteriosclerosis Pulmonary hypertension Right heart failure Clinical signs: Cough, exercise intolerance, dyspnea, ascites

VASCULAR SYSTEM VASCULITIS Phlebitis Refers to inflammation of the veins Inflamed veins often become thrombosed Thrombophlebitis The most common forms of thrombophlebitis in veterinary practice are: Vena caval thrombosis in cattle Femoral thrombophlebitis Prolonged prostration in large animals can result in inflammation and thrombosis of femoral veins Omphalophlebitis Iatrogenic jugular thrombophlebitis In all species, a potential complication of venipuncture

Phlebitis / Thrombophlebitis VASCULAR SYSTEM VASCULITIS Omphalophlebitis Inflammation of the umbilical vein Particularly common in farm animals Ascending infection after birth Opportunistic bacteria E coli Sepsis may result

Phlebitis / Thrombophlebitis VASCULAR SYSTEM VASCULITIS Venal caval thrombosis Rumenitis (Grain overload) Bacteria cross the ruminal mucosa Bacteria drain via the portal system to the liver Hepatic abscesses Rupture through the Vena cava Phlebitis and Thrombosis Pieces of infected thrombus often detach circulation Endocarditis (tricuspid) embolic pneumonia dilate and erode vessels Hemoptysis

Phlebitis / Thrombophlebitis VASCULAR SYSTEM VASCULITIS Young adult cow with a 2 wk history of coughing Minimal improvement with antibiotics Tachycardia Died on the way to the barn for milking Hemorrhage in the lungs Venal caval thrombosis and endocarditis *

TUMOURS OF THE CARDIOVASCULAR SYSTEM The most common cardiovascular tumors seen in domestic animals PRIMARY SECONDARY (METASTATIC) Hemangioma / Hemangiosarcoma Lymphoma Rhabomyoma / Rhabdomyosarcoma Heart Base Tumor: Aortic Body Chemodectoma Carotid Body Chemodectoma Mesothelioma

TUMOURS OF THE CARDIOVASCULAR SYSTEM Hemangioma Benign tumour of endothelial cells Common in dogs Less often in cats, horses, ruminants Can arise in any tissue Most common in the skin nordenergi.org

TUMOURS OF THE CARDIOVASCULAR SYSTEM Hemangiosarcoma Malignant tumour of endothelial cells Hemangiosarcoma is an important canine malignancy Occurs less commonly in cats, cattle, horses etc. Hemangiosarcoma most commonly arises in the right atrium and the spleen Other common sites include the liver and lungs, and metastasis can occur to any site Masses are often dark red in colour and can be single or multiple Bloody on section

Hemangiosarcoma TUMOURS OF THE CARDIOVASCULAR SYSTEM In situ Cardiac hemangiosarcoma Can cause cardiomegaly, congestive heart failure, hemopericardium, +/- cardiac tamponade Readily metastasizes to the lungs, liver, brain, spleen, etc. Histology Images C Legge Histology: Spindle-shaped neoplastic (endothelial) cells line irregular channels filled with blood Gross: Red irregular mass invades the right atrium (auricle)

Hemangiosarcoma TUMOURS OF THE CARDIOVASCULAR SYSTEM

TUMOURS OF THE CARDIOVASCULAR SYSTEM Rhabdomyoma Benign tumour of skeletal muscle Rhabdomyosarcoma Malignant tumour of skeletal muscle Cardiac rhabdomyoma has been described in pigs, cattle, sheep and, are often found incidentally at slaughter It may be congenital It appears as a white solid mass within the myocardium

TUMOURS OF THE CARDIOVASCULAR SYSTEM Chemodectoma (Paraganglioma) Tumour of the chemoreceptors Aortic body tumour Carotid body tumour Usually benign Typically non-functional Carotid body tumours occur at the bifurcation of the carotid artery (cervical mass) Aortic body tumours form single or multiple masses near the base of the heart within the pericardial sac Space occupying mass: May block lymphatics causing pericardial effusion and cardiac tamponade Can cause heart failure because of compression of the atria or vena cava Brachycephalic breeds are predisposed and may have concurrent aortic and carotid body tumours

TUMOURS OF THE CARDIOVASCULAR SYSTEM Chemodectoma Grey-white nodular mass surrounding the great arteries, heart, dog Ectopic thyroid carcinoma and mesothelioma can also cause a heart base mass

TUMOURS OF THE CARDIOVASCULAR SYSTEM Mesothelioma May arise from the pericardium Diffuse pericardial involvement is more common than a discrete mass Causes pericardial effusion Can be difficult to diagnose May have concurrent pleural and/or peritoneal involvement Yamamoto S et al. Mixed Form of Pericardial Mesothelioma with Osseous Differentiation in a Dog J. Comp. Path. 2013, Vol. 149, 229e232

TUMOURS OF THE CARDIOVASCULAR SYSTEM Lymphoma The heart is often involved with lymphoma in cattle (Enzootic bovine leukosis Bovine leukemia virus) Noah s Arkive

Lymphoma TUMOURS OF THE CARDIOVASCULAR SYSTEM

Sincere thanks to Drs A Lopez and E Aburto, AVC, for their contribution to this material.