DIAGNOSIS AND MANAGEMENT OF THE FELINE CARDIAC PATIENT JEREMY ORR DVM, DVSC, DACVIM (CARDIOLOGY)

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1 1 DIAGNOSIS AND MANAGEMENT OF THE FELINE CARDIAC PATIENT JEREMY ORR DVM, DVSC, DACVIM (CARDIOLOGY) 2 CATS ARE DIFFERENT THAN DOGS Heart Murmurs As it is in dogs, the PMI is not as useful in cats Murmurs are typically loudest along the sternum or parasternum Cranial vs caudal: A cranial murmur may be more likely to physiologic Murmurs are labile in cats and often heart rate dependent When examining a cat for a possible subtle murmur, can attempt to increase heart rate to provoke a more obvious murmur 3 CATS ARE DIFFERENT THAN DOGS Heart Murmurs Not all cats with heart disease have heart murmurs and not all cats with heart murmurs have heart disease Contrasts dogs where an acquired heart murmur in an older patient is generally due to cardiac disease and can be present for years prior to onset of clinical signs

2 4 HEART MURMURS IN CATS I hear a heart murmur in a cat - what does it mean? Literature is variable, but innocent murmurs are not uncommon in cats (even geriatric patients) JAVMA 2009, Paige et al 103 healthy cats 15.5% had murmurs - of these cats, 31% had cardiomyopathy Remainder of cats with murmurs had normal hearts 11 cats had cardiomyopathy without a murmur 5 INNOCENT MURMURS IN CATS When a murmur is noted in a cat, echocardiography is warranted Innocent murmurs often related to dynamic right ventricular outflow tract obstruction 6 CATS ARE DIFFERENT THAN DOGS Pulmonary Edema In contrast to dogs, distribution of cardiogenic edema is extremely variable In cats, reported distribution pattern of edema: Diffuse/non-uniform in 61% Diffuse/uniform in 17% Multifocal in 17% Focal in 4% Appearance is also variable Besides interstitial changes, 83% had concurrent alveolar infiltrates and 61% had concurrent bronchial changes

3 7 8 9 CATS ARE DIFFERENT THAN DOGS Pleural effusion is common in feline CHF patients, even when their primary cardiac disease is left sided In canine patients, pleural effusion (if related to cardiac disease) is typically a manifestation of right sided heart failure Can often be seen in systolic dysfunction cases due to biventricular failure and also in those patients with atrial fibrillation

4 CATS ARE DIFFERENT THAN DOGS Thoracic radiographs may have a lower yield in diagnosing patients with mild-moderate cardiac disease As the most common form of disease is HCM, radiographs are insensitive to detect mild-moderate cardiomegaly VD radiograph is more reliable to assess VHS in cats - use short axis dimensions scaled to vertebrae starting at the cranial border of T4 Normal VHS in this plane is generally < 3.5 vertebrae

5 Source: Dr. James Buchanan Valentine shaped heart On DV/VD Relates to left atrial/ auricular enlargement Shifting of apex from midline 15 CATS ARE DIFFERENT THAN DOGS Cats are generally more sensitive to diuretics than dogs As the most common form of disease is one of diastolic dysfunction, patients need some degree of preload to prime their stiffened left ventricle Excessive preload reduction with diuretics can limit priming/ diastolic filling lead to reduced cardiac output Maximum furosemide dose is controversial but I generally avoid exceeding 3 mg/kg PO q. 8 hrs for chronic maintenance therapy for CHF

6 16 CATS ARE DIFFERENT THAN DOGS Thromboembolic complications Uncommon in canine heart disease even with atrial fibrillation Generally extra cardiac disease is a more common risk factor (PLN, PLE, Cushing s) Very common in feline patients Virchow s Triad In a study of 127 cats with feline arterial thromboembolism, a clot was the first sign of disease in 76% of affected cats 17 LEFT ATRIAL ENLARGEMENT Normal Left Atrium Ginormous Left Atrium 18 SMOKE IN CATS Spontaneous echocontrast

7 19 FELINE ARTERIAL THROMBOEMBOLISM Appearance of left atrial enlargement and/or smoke places cats at high risk for development of a left atrial thrombus 20 FELINE ARTERIAL THROMBOEMBOLISM Cats with HCM have been shown to have platelet hypercoagulability = risk factor Represents clot formed in a cardiac chamber which embolizes and lodges in a distal vessel 71% of cases are bilateral Can affect forelimbs Right forelimb may be more likely 21 FELINE ARTERIAL THROMBOEMBOLISM Pathophysiology Physical occlusion of a vessel Vasoactive substances released from thrombus/ endothelium cause vasoconstriction of collateral vessels Serotonin, prostaglandins Causes ischemic damage to tissues Five P s: Pain, pulselessness, pallor, paresis, poikilothermia

8 22 THERAPY FOR FELINE ARTERIAL THROMBOEMBOLISM Surgery not an option Removal of clot does not reverse collateral circulatory shut down Analgesia *** Improve systemic perfusion Judicious use of fluids - many in CHF Manage CHF Thrombolytic therapy $$$, case studies to dat show high mortality Anticoagulant therapy Heparins, clopidogrel 23 THERAPY FOR FELINE ARTERIAL THROMBOEMBOLISM Heparin therapy: U/kg SQ q. 8 hrs (1st dose IV if shocky) ACT/PTT less predictive of plasma heparin concentrations therefore many do not measure clotting parameters Low-molecular weight heparin therapy: Enoxaparin 1 mg/kg SQ q. 8 hrs Can be continued long term after hospitalization Clopidogrel mg orally once daily (1/4 of a 75 mg tablet) 24 PROGNOSIS OF FELINE ARTERIAL THROMBOEMBOLISM With complete aortic occlusion 35% survive initial episode With partial embolization 70% survive initial episode Spontaneous resolution occurs in over 50% cases within 2-6 weeks Recurrence rate of embolization is high, usually within 6 months If no concurrent CHF - median survival 225 days If CHF present - median survival days

9 25 CATS ARE DIFFERENT THAN DOGS Vetmedin (pimobendan) is generally contraindicated for use in cats, unless an echocardiogram has been performed to diagnose their underlying disease Vetmedin as a positive inotrope can worsen obstruction to cardiac output - dynamic obstructions are common in feline HCM The vasodilator effect of Vetmedin may still be helpful in some forms of feline cardiac disease 26 CATS ARE DIFFERENT THAN DOGS CHF can be precipitated in an otherwise asymptomatic feline patient much more commonly than reported in canine patients Recent fluid administration Recent general anesthesia Repositol corticosteroid administration (generally 3-6 days later) Recent stressful event 27 DIAGNOSIS OF FELINE CARDIAC DISEASE - HISTORY May be asymptomatic Non-specific findings: lethargy, weight loss, anorexia, dyspnea, limping, hiding, etc. Less common findings: ascites, collapse Cough is rarely noted in cats with heart failure - more commonly due to feline allergic airway disease

10 28 DIAGNOSIS OF FELINE CARDIAC DISEASE - DYSPNEA In a study of 90 cats presenting for dyspnea: 38% had underlying cardiac disease 32% had underlying respiratory disease 20% had neoplasia to account for their dyspnea 29 PHYSICAL EXAM FINDINGS IN CARDIAC DISEASE Diagnosis of cardiac disease can be challenging as a recent study revealed that upwards of 69% of cats with HCM did not have a heart murmur Therefore, evaluation is generally always recommended for a new heart murmur in a feline patient Gallop sound (not rhythm) Arrhythmias 30 GALLOPS IN CATS Tripling of the heart sounds Think the canter of a horse Represents an S3 or S4 heart sound S3 - ventricular gallop S4 - atrial gallop

11 31 GALLOPS IN CATS Best heard with the bell of the stethoscope Low frequency sound Murmurs are high frequency sounds and therefore best heard with the diaphragm Typically represents significant myocardial disease Occasionally can be a normal finding in older, stressed cats The presence of a gallop in a cat warrants further evaluation including an echocardiogram 32 DIAGNOSIS OF FELINE CARDIAC DISEASE - RADIOGRAPHS Thoracic radiographs are indicated for any patient with respiratory signs If patient is stressed, a DV radiograph can be easily taken with minimal handling/stress on the patient Can be used to confirm pleural effusion if exam findings are consistent and without access to ultrasound Pleural effusion is poorly responsive to diuretics - thoracocentesis is indicated! Patient can be sedated if needed to perform films 33 DIAGNOSIS OF FELINE CARDIAC DISEASE - ECHOCARDIOGRAPHY Echocardiography is the gold standard diagnostic test to assess for underlying cardiac disease in cats Determines etiology of an incidental heart murmur in an asymptomatic patient Determines etiology of gallop Help to evaluate for cause of dyspnea in a patient with equivocal thoracic radiographs Evaluate for other sequelae to cardiac disease - thrombi, effusions, assess systolic function

12 34 DIAGNOSIS OF FELINE CARDIAC DISEASE - ECG Electrocardiogram (ECG) is indicated if an arrhythmia is noted A baseline ECG has a poor sensitivity to detect cardiac chamber enlargement in feline patients If LV enlargement is present, may see tall R waves in lead II ECG is often normal in feline patients with cardiac disease (unless arrhythmia is present) 35 DIAGNOSIS OF FELINE CARDIAC DISEASE - BIOMARKERS NT-proBNP Released from heart due to atrial or ventricular stretch/ dilation Causes natriuresis and vasodilation, counteracts the RAAS NT form is biologically inactive - used as a marker as stable with long half life May identify cardiac disease in asymptomatic patients - sensitivity reported at 90%, specificity at 85% 36 DIAGNOSIS OF FELINE CARDIAC DISEASE - BLOOD PRESSURE Used to screen for hypertension Hypertension can contribute to concentric LV hypertrophy Remember, hypertension does not occur secondary to heart disease Generally secondary to CKD in feline patients

13 37 HYPERTROPHIC CARDIOMYOPATHY Acquired idiopathic myocardial disorder Rule out hypertension, hyperthyroidism Characterized by concentric hypertrophy of the LV Results in diastolic dysfunction Primary etiology unknown Familial and heritable form has been identified Maine Coons, Ragdolls, Persians Breed specific mutation of myosin binding protein-c gene has been found to be causative in Maine Coons & Ragdolls 38 SIGNALMENT & PREVALENCE Median age is 5.5 years at time of diagnosis Equally distributed amongst males and females Represents 67.6% of feline cardiomyopathies Most common in domestic shorthairs Increased risk in Maine Coons, Ragdolls, Persians, Sphynx, Himalayan 39 OUTCOME Arrhythmias Related to myocardial hypertrophy and ischemia Risk for sudden death Congestive heart failure Related to increased LV diastolic filling pressures and left atrial enlargement Feline arterial thromboembolism Some affected individuals are asymptomatic for entire natural lifespan

14 40 ECHOCARDIOGRAPHIC FINDINGS 41 OBSTRUCTIVE FORM OF HCM Related to systolic anterior motion of the mitral valve (SAM) causing obstruction in the LV outflow tract Characterized by turbulence and increased velocity of blood flow in the LVOT Present in about 50% of cats with HCM Etiology is suspected to be related to altered LV geometry related to HCM Complicated by the hyper-dynamic state of LV related to hypertrophy 42 SAM Anterior mitral leaflet in systole comes into contact with IVS Associated turbulence in LVOT and mitral insufficiency (posteriorly directed)

15 SAM in Still Form TREATMENT OF HCM Principles of therapy Improve LV diastolic function Reduce pulmonary edema & pleural effusion Prevent thromboembolic disease Clopidogrel, enoxaprin, apixaban Treat any underlying disorders Hyperthyroidism, hypertension 45 BETA BLOCKERS Can improve LV diastolic function indirectly by reducing HR and improving myocardial perfusion, thus enhancing diastolic filling Negative inotropic properties reduce myocardial oxygen demand to reduce ischemia Anti-Arrhythmic properties; blockage of deleterious effects of chronic SNS stimulation Dose: mg/cat PO q hrs Do not start in patients with CHF until CHF controlled - they may require a lower dosage

16 46 TREATMENT OF HOCM Hemodynamic changes that will reduce degree of obstruction: Decrease in contractility, heart rate Increase in preload, afterload Our target: decrease contractility and slow heart rate (goal bpm in hospital) Start low with dose and titrate up while monitoring for side effects 47 TREATMENT OF EDEMA & EFFUSIONS Diuretic Furosemide: 1-3 mg/kg PO q hrs Lowest dose possible to control congestion ACE inhibitors Enalapril or benazepril mg/kg PO q. 24 hrs Blocks RAAS when furosemide used Periodic centesis for recurrent effusions may be necessary Then diuretics to help stop/delay return of effusion 48 DRUGS TO AVOID Direct arteriolar dilators will potentially exacerbate the situation Reduces afterload and can promote hypotension as the LV (which is already contracting maximally) cannot substantially augment stroke volume (due to diastolic dysfunction) to raise blood pressure

17 49 PROGNOSIS FOR HCM JAVMA 2002, Rush et al Median survival was 709 days (overall) Asymptomatic cats: 1129 days Cats with CHF: 563 days Cats with FATE: 184 days No data to suggest that obstructive form has a different outcome from non-obstructive form If due to hyperthyrodisim, hypertension - prognosis excellent as therapy can potentially reverse the underlying disorder 50 RESTRICTIVE CARDIOMYOPATHY (RCM) Unknown etiology Characterized by diastolic dysfunction and increased myocardial stiffness In some patients can have extensive endomyocardial fibrosis, in others a large endomyocardial scar spanning the LV can be noted 51 JVC 2004, Fox

18 52 TREATMENT & PROGNOSIS Treatment: Diuretics - judicious - patients heavily dependent on certain degree of preload for LV filling ACE inhibitors Thromboembolic prophylaxis +/- pimobendan Prognosis: Variable but generally considered to be guarded (when in CHF) - survival measured in months, rarely years 53 ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY (ARVC) Uncommon cardiomyopathy Etiology unknown Characterized by extensive replacement of the RV myocardium with fibrous and fatty tissue Marked RV/RA dilation Hypokinetic wall motion and right heart failure Arrhythmias - ventricular and atrial origin 54 Circulation 2000, Fox et al

19 55 ARVC Therapy Treat for right heart failure: furosemide, ACE inhibitors Treat arrhythmias: atenolol, sotalol (ventricular, atrial); diltiazem (atrial) Prognosis Very poor Fox 2000: 2 days to 4 months, median 1 month 56 DILATED CARDIOMYOPATHY Rare form of cardiomyopathy Taurine deficiency was previously common - now rare due to addition to diets Burnt out heart - a DCM like phenomenon is noted in cats with endstage HCM LV enlargement, reduced contractility, regions of myocardial hypokinesis/ akinesis, atrial enlargement 57 DCM Treatment As per other forms of cardiomyopathy Pimobendan - safety and efficacy of use unknown in cats - dose likely lower than dogs (0.625 mg twice daily) Prognosis If due to taurine deficiency - with supportive care and supplementation prognosis may be good Otherwise prognosis is grave - death in weeks

20 58 ACUTE MANAGEMENT OF THE FELINE CHF PATIENT DO NOT STRESS Sedating is much safer if needed Oxygen Attempt IV catheter - but avoid stress Furosemide 2 mg/kg IV or IM (not SQ) If pleural effusion is present, immediate thoracocentesis Sedate if necessary 59 ACUTE MANAGEMENT OF THE FELINE CHF PATIENT Furosemide can be repeated at 1-2 mg/kg IM/IV q hrs More judicious dosing than dogs Could consider furosemide CRI but do not exceed 0.5 mg/kg/hr Tailor furosemide dosing to the needs of the patient Consider anti-platelet therapy with clopidogrel, heparins 60 DIAGNOSTICS FOR THE ACUTE CHF PATIENT Baseline lab work - renal values, electrolytes, T4 level Radiographs repeated in hours to follow resolution of CHF Blood pressure measures Hourly respiratory rate monitoring

21 61 MANAGEMENT STRATEGIES FOR FELINE CHF Refractory CHF Ensure owner is compliant with administering medications Identify diuretic resistance Measure urine sp gr (should be < when receiving diuretics) If suspected, change to SQ furosemide administration or add second diuretic such as HCTZ; change to torsemide Avoid dietary sodium excess 62 MANAGEMENT STRATEGIES FOR FELINE CHF Identify concurrent anemia Moderate anemia can contribute to volume overload Treatment with EPO may lessen degree of volume overload and improve oxygen handling capacity 63 TORSEMIDE Potent loop diuretic - 10x more potent than furosemide with longer duration of diuretic effect (peak 4 hours, lasts 12 hours) Contrasts to furosemide with duration of effect of about 6 hours Can block aldosterone and limit myocardial fibrosis Dose reported mg/kg PO q hrs Can replace furosemide with torsemide Some have added to furosemide while reducing furosemide dose by 50%

22 64 AZOTEMIA Not uncommon in patients receiving high doses of diuretics Treatment is generally withdrawing diuretics temporarily if safe to do so (ie: no overt CHF). If significant, judicious IV fluids can be given Half strength saline DO NOT give fluids while still giving diuretics Counterproductive Which disorder is predominant: kidneys or heart? 65 CONCURRENT FELINE ALLERGIC AIRWAY DISEASE Steroids have been associated with CHF in cats - injectable generally sooner than oral administration (4 days vs 34 days) Alternatives include inhaled steroid therapy with fluticasone (Flovent) at 110 mcg once to twice daily Often ideal to start with short oral course of steroid due to their potency Reduce environmental triggers 66 QUESTIONS?