Transcript Slide 1
Tom Robertson MA VetMB CertVDI CertVC MRCVS Subjects to be covered: Anatomy and Function of the normal heart What causes a murmur and what goes wrong in heart failure Congenital and acquired conditions in predisposed breeds Nursing the cardiac patient ? Blood pressure M The role of the cardiovascular system To provide nutrients (e.g.Oxygen)to all organs via arteries and capillary beds. To remove waste products of metabolism (e.g.Carbon dioxide) via capillaries and veins Arteries The aorta carries blood to the periphery and its elastic nature promotes flow in diastole and systole. The smaller arteries have muscular walls and contraction of these alters the vascular resistance and therefore blood pressure Veins These hold 70% of the blood volume Contraction of the venous system increases the return of blood to the heart, vasodilation reduces the return to the heart. The Heart Starlings Mechanism Systole is the period of cardiac contraction when blood is ejected from the heart into the aorta or pulmonary artery Diastole is the period of cardiac relaxation when blood returns to the heart and fills the chambers ready for the next contraction Coronary blood flow during diastole Taking a cardiac history - what’s important? History Exercise tolerance, changes in activity/behaviour Breathing changes – normal resting respiratory rate is less than 30bpm Syncope Sleep habits Alterations in appetite Weight change Coughing – does heart failure cause coughing? Cardiac Cachexia – loss of muscle mass due to heart disease. A coughing overweight dog is more likely to have lung disease. Clinical examination Observe respiration from a distance Mucous membranes – pale/cyanotic Jugular veins Check for precordial thrill at apex beat Femoral pulses Normal pulses 70-160 dogs, 90-240 cats Palpate abdomen – ascites/hepatomegaly auscultation Listen to both sides in a quiet room – heart and lungs Ideally palpate pulses at the same time as listening to the heart Listen for murmurs/gallop sounds Sinus arrhythmia Heart rates of 80-120bpm in dogs suggest heart failure is unlikely (low sympathetic drive) Cats can do anything but slow heart rates and hypothermia are bad signs!! ECG ECG Normal ecg Echocardiography X-ray Quiz Why X-Ray? Best way to assess overall heart size – VHS Only way to confirm congestive heart failure Identifies other thoracic pathology A murmur is caused by turbulent blood flow Caused by blood flowing the wrong way or blood moving too quickly Physiological – e.g anaemia, athletic lean dogs Associated with structural disease e.g VSD, AS/PS Diastolic, systolic or continuous Grade 1 – difficult to hear Grade 2 – quieter than the normal heart sounds Grade 3 – same intensity as the other heart sounds Grade 4 – louder than the other heart sounds Grade 5 – precordial thrill present Grade 6 – audible without touching the thorax Cardiac Cycle Q P R S T Normal MR PDA Gallop Rhythms The heart potentially has 4 heart sounds. A gallop is an extra audible heart sound resulting in a heart that sounds like the canter of a horse S1 – closure of the AV valves. Start of systole. S2 – closure of the semilunar valves S3 – rapid filling of the ventricle during diastole S4 – atrial contraction Preload – volume of blood returning to the left ventricle and volume of blood left over after the last contraction Afterload – resistance against which the left ventricle has to eject blood Fluid is maintained in blood vessels via hydrostatic and osmotic pressures XS fluid is removed via the lymphatic system and returned to the heart Heart Failure/Vascular Shock Heart output drops - noted by kidneys and baroreceptors in aorta and carotids Activation of the renin angiotensin system to conserve water – increased thirst and sodium retention Sympathetic nervous system activated to increased heart contractility, HR, vasoconstriction Increased blood return to the heart causes increased contractility Congestive heart failure If pre-load increases too much the hydstatic pressures in the capillaries increases, the lymphatics are overwhelmed and fluid accumalates in the interstitial areas – congestive heart failure Right sided failure – ascites, pericardial effusion Left sided failure – pulmonary oedema Forwards failure Heart output is insufficient to provide enough oxygenated blood to the head or body Leads to exercise intolerance and syncope Clinical signs of heart failure in cats Dyspnoea (difficulty breathing) Tachypnoea (rapid breathing) Often get pleural effusions Pulmonary oedema Ascites Cold extremities/cyanotic extremities No cough Embolism May not present until very late in the course of the disease Clinical signs of heart failure in dogs Tachycardia Dyspnoea/tachypnoea Ascites Cyanosis/cold extremities Weight loss ?coughing Dilated Cardiomyopathy Dilated cardiomyopathy Causes : genetic, chronic tachycardia, lack of taurine in cats (and some dogs), hypothyroidism Pre-clinical DCM Aim to diagnose at risk breeds prior to development of signs of CHF Dobermans 60% affected and 25-30% can have sudden death in the preclinical phase VPC’s are most common initial findings Boxers Arrhymthogenic right ventricular cardiomyopathy (Boxer Cardiomyopathy) Collapsing boxers Variable progression Holter monitor Troponin I Cocker Spaniels Some are Taurine deficient Better long term prognosis Classical DCM on echo Hypertrophic Cardiomyopathy HCM Most common heart disease in cats Thickening to the myocardium preventing normal filling and ventricular relaxation during diastole Maine Coons Ragdolls British Short hairs Sphinx Secondry to hyperthyroidism, acromegaly, systemic hypertension Restrictive Cardiomyopathy Fibrous irregular myocardium Systolic failure Very large left and right atria Feline aortic thromboembolism (FATE) May be the first sign of heart disease Thrombus occurs because blood is flowing more slowly than normal Normally lodges in the right brachial artery or the aorta Acute paralysis to one or both legs Severe pain/distress Hypothermia/Bradycardia poor prognostic signs Treatment of FATE Analgesia – opiates Oxygen Treat heart failure Heparin injections Nutritional support Long term clopidogrel/aspirin as preventative Consider euthanasia in severe cases Pericardial effusion Pericardial effusion Fluid around the heart occurs due to: Neoplasia, idiopathic, heart failure, infection Causes right sided failure due to cardiac tamponade Right sided failure develops: ascites, jugular venous distension. NB do not use diuresis as reduces blood pressure and worsens the tamponade Treatment of pericardial effusion Pericardiocentesis Myxomatous Mitral Valve Disease Most common acquired heart disease in dogs Small breeds CKCS Slowly progressive disease Myxomatous Mitral Valve Disease MMVD Oh no its an ECG!! Oh crap another one! Last one I promise! Tricuspid Dysplasia Tricuspid dysplasia PDA Has been reported as most common defect Failure of closure of the Ductus Arteriosus at birth Continuous murmur Females:males Toy Breeds -Maltese, Pomeranians, Yorkies, Bichon Frise Border Collies English Springer Spaniels GSD’s PDA treatment Surgery Amplatz Canine Duct Occluder 2.5k-3k cost PDA surgery http://www.youtube.com/watch?v=F1BDn6nFCII&list =UU1VXxdm_MDPqvjOa8mMgXqw Aortic Stenosis Abnormal narrowing to aorta Boxers (Breed Scheme) Golden Retrievers German short haired pointer Rottweiler GSD Newfoundlands Graded according to blood velocity Medical treatment only Pulmonic Stenosis Cocker Spaniels, Boxer, Bulldogs, Beagle, Chihuahua Abnormal narrowing to pulmonary artery Severe stenosis treatment with balloon valvulplasty http://www.youtube.com/watc h?v=0N7V7SQ7API&list=UU1VX xdm_MDPqvjOa8mMgXqw Ventricular Septal Defect English Springer Spaniels English Bulldog Are all murmurs in puppies/kitten bad? Innocent murmurs common <4months <grade 3 Should disappear by 4m in dogs No clinical signs Can continue into adulthood in cats Emergency Treatment Oxygen Minimal Stress 2mg/kg frusemide IV/IM every 2 hours Monitor urine output Free access to water Maintain correct temperature Monitor RR, HR every 2 hours Abdominocentesis Thoracocentesis Long term treatment Moderate sodium restriction in diet Good quality food Omega oil supplements – protect against muscle loss Monitor RR and HR – CEVA App Weight checks – beware cardiac cachexia Monitor electrolytes/renal function What do all those drugs do?? Improve contractility - pimobendan Reduce fluid overload - frusemide Dilate blood vessel – ace-inhibitors/pimobendan Reduce fibrosis to myocardium - spironolactone Normal blood pressure in dogs/cats 60-150 Hypetensive >170mmHg dogs, >180mmHg cats Increased blood pressure (hypertension) can affected the eyes (retinal bleed/detachment), CNS,kidneys and heart Symptoms include blindness, dilated pupils, protein loss in the kidneys, heart murmurs. Causes of hypertension Hyperthyroidism Kidney disease Diabetes Cushings Primary Measurement:direct vs indirect Oscillometric Used on the tail or leg Detects oscillations in blood vessels Doppler Treatment of high blood pressure: amlodipine Blood pressure Most normal cats have systolic pressure 130-175mmHg 175-200mmHg is suspicious of hypertension >200mmHg likely genuine hypertensive Doppler Quiet room Cuff between carpus and elbow width 40% of limb circumference Spirit over common digital artery then gel Apply probe over the common digital artery and listen for pulse (use head phones) Inflate cuff until sound goes then gradually deflate until pulse audible again Hypotension Readings of <90mmHg are consistent with hypotension Blood pressure should be maintained above 60mmHg to ensure adequate tissue perfusion to vital organs