Acquired heart conditions Flashcards
Dilated cardiomyopathy–K9
General/lesions
- Decreased myocardial contractiliy–systolic dysfunction–leading to progressive dilation of the L and/or R ventricle
- Mild thinning of the walls
- Can lead to eventual L or R-sided CHF
- Histo lesions include
- Lack of inflammation
- Wavy myofibers
- Fibro-fatty infiltration
- Loss of myocytes and myocardial fibrosis
Dilated cardiomyopathy–K9
Pathophysiology
- Idiopathic–diagnosis of exclusion, but poss. familial etiology in dobies, boxers, cockers, wolfhounds
- End-stage of various other processes–L-carnitine or taurine deficiencies, toxicities (doxorubicin, alcohol), ischemia, infections, immunological, tachycardia and metabolic abnormalities
Dilated cardiomyopathy–K9
Doberman pinscher progression
- Arrhythmogenic cardiomyoathy
- Arrhythmias but normal L ventricular contractility
- IWH may have lone AF
- Dobies present w/ VDs, generally progresses to the next stage of dz
- Occult DCM
- Animals appear normal but have mophological changes (L ventricular enlargement), trending towards dec. contractility
- Ventricular arrhythmias or AF common
- Classic DCM: heart failure
- L-sided more common
- Ventricular enlargement, dec. contractility–systolic dysfunction
- Ventricular arrhythmias or AF present
Dilated cardiomyopathy–K9
Taurine/L-carnitine deficiency
- Bile acids are conjugated with taurine
- Important moderator of Ca flux, reduces platelet aggregation, stabilizes neural membranes, + inotrope
- Dogs can synthesize (those on lamb and rice diet have recently been diagnosed w/ deficiencies)
- Recommend supplementing dogs on these diets w/ taurine and carnitine
- Dogs which develop DCM can improve w/ medication and may eventually only need supplementation (will not reverse damage)
Dilated cardiomyopathy
Signalment
Usual history
- Signalment
- Seen in giant and some smaller breeds of dogs
- Dif. gene pools may be over-represented in dif. countries
- Most common in middle-aged males
- History
- Depends on ventricles involved
- Wt. loss, exercise intolerance, weakness, syncope, etc.
- Sudden death occurs in ~30% of dobies
Dilated cardiomyopathy–K9
Common abnormalities on PE
- Poor BCS
- Signs of heart failure
- Muffled heart and lung sounds
- Signs of A-fib
- Systolic murmur from mitral regurg
- S3 gallop sounds common
Dilated cardiomyopathy–K9
Abnormalities commonly found on special exam
- Labwork
- Pre-renal azotemia
- Elevated liver enzymes
- Low taurine or arnitine levels (rare)
- Future–natriuretic and cardiac tropoin level testings (early diagnosis)
- X-ray–generalized heart enlargement
- Echo–definitive diagnosis
- Ventricular enlargement w/ ‘flabby,’ thin walls
- Reduced contractility and fractional shortening is decreased (~23% is normal for dobies)
- M-mode–fractional shortening <20% (N = 25-45% in normal dogs)
- Doppler–mitral valve insufficiency and reduced SV
- ECG
- VPDs–dobies
- Up to 50/day ok
- A-fib in other breeds
- Signs of heart enlargement and ST segment depression
- VPDs–dobies
Dilated cardiomyopathy–K9
DDx
Prevention
Prognosis
- DDx–pericardial effusion
- Prevention–genetic markers should be available to detect animals at risk to keep them from breeding programs
- Autosommal dominant in dobies–mutation in pyruvate dehydrogenase kinase (PDK4); commercial test available
- Age of onset variable
- Prognosis
- Guarded to poor
- Therapy will inc. quality of life
- ACE inhibitors and pimobendan together improve life expectancy to 350 days
- American cocker spaniels can recover completely w/ taurine and carnitine deficiency
Dilated cardiomyopathy–K9
Treatment: ACM
- Arrhythmogenic CM
- Treat if avg HR >90bpm or >250bpm w/ exercise
- No evidence that treating will reduce risk of sudden death
- Recommended to treat dogs w/ runs of VT, RonT phenomenon, or excessive VPDs
- Lone A-fib
- Beta blockers–atenolol, metoprolol
- Control arrhythmias and ‘cardio-protection’
- Diltiazem–control HR
- Ventricular arrhythmias
- Beta-blockers: sotalol
- Combination of mexiletine and atenolol–reduce frequency of ventricular beats and runs
- Indication to delay onset of further stages
Dilated cardiomyopathy–K9
Treatment: OCM
- Ace inhibitors in dobies seem to delay onset of DCM
- Same effect possibly with beta-blockers
- Treat arrhythmias and moitor for dz progression
Dilated cardiomyopathy–K9
Treatment–DCM and CHF
- Mild failure: furosemide, ACE inhibitors, pimobendan, and antiarrhythmics
- Severe failure: hospitalized, oxygenated, and treated w/ injectable furosemide (monitor for hypo- K, Na, and Cl); observe RR and change administration of furosemide accordingly
- Dobutamine can be used in cases of hypotension and markedly decreased contractility
- Reduced preload w/ nitroglycerine ointment or sodium nitroprusside
- Control w/ ACE inhibitors after
- Pimobendan–(+) inotrope, inc. sensitivity to existing Ca w/o an inc. in myocardial oxygen demand
- PDE III inhibitor–inc. contractility, general vasodilator
- Digoxin + diltiazem–slow ventricular response rate in dogs w/ A-fib
- Hypotension and heart block may occur
- Dogs w/ clinical signs from ventricular arrhythmias, runs of VT, numerous VPDs w/ tachy, or RonT phenomenon–lidocaine followed by long-term mexiletine
- No evidence that this will prevent sudden death
- Reserve this trtmt for dogs w/ VT
- Beta-blockers–dec. # and complexity of ventricular arrhythmias at low doses
-
High doses are (-) inotropes and cause severe decompensation
- Should not be initiated until heart failure is controlled and standard therapy is in place
- Metoprolol or carvediolol–dose should be gradually inc. until decompensation occurs, then back off
- Optimal dose is unknown–low dose better than nothing
-
High doses are (-) inotropes and cause severe decompensation
- After discharge from hospital animal should set own activity level + restricted Na diet
- Taper to lowest poss. dose of furosemide, start ACE inhibitors low and gradually inc. to max over a few weeks
- Renal fx should be monitored/assessed after 3-7d (furosemide doseage)–dec. if BUN, Cr elevated
- Supplement for any deficiencies ID’d
- Fish oil improves cachexia in dobies
Dilated cardiomyopathy–feline
Pathophysiology
- Characterized by ventricular dilation, thinning of ventricular wall, and dec. contractility
- Majority of cases are due to taurine deficiency
- Rare disease now
Dilated cardiomyopathy–feline
Signalment
Usual history
- Signalment
- Middle aged to older males
- Burmese, siamese, abyssinian predisposed
- History
- Acute onset of paresis/paralysis due to ATE
- Dyspnea, anorexia, lethargy, vomiting, and lung sounds
- Gallop rhythms and murmur from AV valvular insufficiency common
- Focal areas of retinal degeneration are suggestive of taurine deficiency
Dilated cardiomyopathy–feline
Common abnormalities on PE
DDx
Prevention
- PE
- Hypothermic, weak femoral pulses, poor CRT
- Dyspnea, muffled heart and lung sounds
- Gallop rhythms and murmur from AV valvular insufficiency common
- Focal areas of retinal degeneration are suggestive of taurine deficiency
- DDx–hypertrophic cardiomyopathy
- Prevention–ensure cats receive adequate levels of taurine
Dilated cardiomyopathy–feline
Abnormalities on special exam
- Labwork–low taurine or high T4
- X-ray
- Pleural effusion
- Heart appears diffusely enlarged
- Diffuse alveolar and interstitial patterns in lungs
- Echo–definitive diagnosis
- Dilated, thin-walled left ventricle w/ reduced contractility
- M-mode
- Inc. left atrial dimensions
- Dec. ventricular wall thickness
- Reduced fractional shortening
- Doppler–mitral valve insufficiency, reduced stroke volume
- ECG–normal or tall R waves in lead II
Dilated cardiomyopathy–feline
Treatment
Prognosis
- Treatment
- Treat pulmonary edema/pleural effusion if present
- Oxygen, furosemide, venodilator therapy, thoracocentesis
- ACE inhibitors can improve systolic fx
- Treat ATE if present
- Supplement taurine if found deficient
- Will see echocardiographic improvement in ventricular performance by 6wks
- Treat hyperthyroidism if present
- Treat pulmonary edema/pleural effusion if present
- Prognosis: fair if taurine deficient; if not, most cats die w/in 2 months regardless of treatment
Hypertrophic cardiomyopathy
Pathophysiology
- Functional abnormalities in myocytes that leads to inc. cell stress and activation of trophic and mitotic factors–papillary musc. and left ventricular concentric hypertrophy (diffuse or focal)
- Histo-myocytes are enlarged w/ fiber disarray
- Intramural coronary arteriosclerosis and myocardial interstitial fibrosis
- Primary and idiopathic in most cases
- Hypertrophied and fibrosed L ventricular wall lacks compliance and cannot fill during diastole–diastolic failure; ventricular chamber non-existent in systole
- Dynamic outflow tract obstruction by hypertrophied ventricular septum
- Systolic anterior motion of the anterior mitral valve leaflets–misalignment of the mitral valve; anterior leaflets blocking outflow tract during systole
- Can cause mitral insufficiency and regurg of blood back into atrium during systole = murmur
- Lack of diastolic filling in L ventricle = inc. pressure in the L atrium –> chamber enlargement – L CHF signs
- Blood stasis in the L atrium can predispose to clot formation
- If dislodges–> iliac bifurcation of the aorta an dlodge–> ischemia in one/both hind limbs
- Muscle necrosis, lameness
- If dislodges–> iliac bifurcation of the aorta an dlodge–> ischemia in one/both hind limbs
Hypertrophic cardiomyopathy
Signalment
Usual history
- Signalment
- Most common cardiomyopathy in cats; exclusion diagnosis
- Middle-aged male cats
- History
- Most asymptomatic; only pick up murmur as incidental finding
- Can trigger animal into heart failure if too stressful
- Some may die suddenly–arrhythmias
- Cats in heart failure resent w/ acute dyspnea–apear perfectly normal until then
- Heart failure cats may also have painful hind limb lameness
Hypertrophic cardiomyopathy
Common findings on E
- Pronounced apex beat on L side
- S4 gallop rhythms and systolic murmurs common
- Hind limbs may be cold to the touch, muscles hard and painful–lameness may be only sign
- Remember that distress signs can mimic heart failure
Hypertrophic cardiomyopathy
Common abnormalities found on special exams
- Labwork
- Troponin-1 and pro-BNP biomarkers elevated
- ATE–muscle necrosis and elevated ck AND ast
- K+ may be elevated
- Normal coag
- X-ray
- Valentine-shaped heart on DV
- 50% have generalize heart enlargement–appear like DCM
- Pulmonary edema present if in CHF
- Echo
- Marked thickening of the ventricular septum or L ventricular free wall
- Papillary muscle hypertrophy
- Reduced ventricular lumen
- Can see regional or segmental hypertrophy
- Can see dynamic outflow obstruction and SAM
- Doppler
- Turbulence in outflow tract
- Can also see jets at mitral valve if insufficient
- Spectral doppler will allow measurements of pressure gradients–determines severity of obstructions if resent
- M-mode–thickened ventricular free wall and septum
- Angio
- Enlarged heart and septum, enlarged papillary muscles, dec. ventricular volume
- Can be used to confirm ATE
- ECG–normal or signs of L heart enlargement, dysrrhythmias or microscopic intramural myocardial infarction (MIMI)