cardiology-workup

# Cardiology Workup ## Overview Veterinary cardiac examination and diagnostic workup including murmur grading (I-VI), arrhythmia classification, echocardiography indications, and ACVIM staging for MMVD and DCM. ## When to Use - User presents a case or question involving cardiology workup in a veterinary context - User asks about species-specific approaches to cardiology workup - Keywords: cardiac, heart, murmur, arrhythmia, echo, ACVIM, MMVD, DCM, CHF, heart failure, pimobendan, furosemide ## Murmur Grading (I-VI) | Grade | Description | | --- | --- | | I | Faint; heard only after prolonged auscultation in a quiet room | | II | Soft but readily audible | | III | Moderate intensity; no precordial thrill | | IV | Loud; precordial thrill palpable | | V | Very loud; thrill palpable; audible with stethoscope barely on chest | | VI | Audible with stethoscope lifted off the chest wall; thrilling | ## ACVIM Staging (MMVD / DCM) | Stage | Criteria | | --- | --- | | A | At risk (breed predisposition) but no structural disease | | B1 | Murmur present; no cardiomegaly on imaging | | B2 | Cardiomegaly confirmed: LA:Ao > 1.6 **or** LVIDDN ≥ 1.7 (radiographic and/or echocardiographic evidence of cardiomegaly). Treatment threshold. | | C | Current or prior clinical signs of heart failure | | D | Refractory heart failure despite standard therapy | ## Workflow 1. Confirm species and signalment (MANDATORY for clinical skills). 2. Gather relevant clinical history and examination findings. 3. Grade the murmur (I-VI) and classify any arrhythmia. 4. Apply ACVIM staging criteria; determine if B2 threshold is met. 5. Apply species-specific protocols and reference ranges. 6. Consider breed predispositions relevant to this domain. 7. Reference current veterinary guidelines and cite sources. ## Treatment Landmarks | Stage | Action | | --- | --- | | B1 | Monitor; no treatment indicated. Recheck echocardiogram q6-12 months. | | B2 | **Initiate pimobendan** (0.25-0.3 mg/kg PO q12h). EPIC trial demonstrated 15-month median delay to onset of CHF. | | C (first episode) | Pimobendan + furosemide (2-4 mg/kg PO q12h, titrate to effect) + ACE inhibitor (enalapril/benazepril 0.5 mg/kg q12h). | | C (chronic) | Optimize furosemide dose; add spironolactone (1-2 mg/kg q12h). Consider dietary sodium restriction. | | D (refractory) | Maximize diuretics (add hydrochlorothiazide 1-2 mg/kg q12h cautiously), sildenafil if pulmonary hypertension, consider pimobendan dose increase. Specialist referral strongly recommended. | ## Key Species Differences **Canine:** - **MMVD (myxomatous mitral valve disease):** Most common acquired heart disease. Small breeds predominate (CKCS, Dachshund, Chihuahua, WHWT). Left-sided murmur, mitral regurgitation on echo. ACVIM staging applies directly. - **DCM (dilated cardiomyopathy):** Large/giant breeds (Doberman, Great Dane, Irish Wolfhound, Boxer). Doberman DCM is occult (arrhythmias before clinical signs); annual Holter + echo screening recommended starting age 3-4 years. - **Pericardial effusion:** Common cause of right-sided heart failure in large breeds. Rule out hemangiosarcoma (right atrium) and heart base tumor (chemodectoma). Pericardiocentesis is diagnostic and therapeutic. **Feline:** - **HCM (hypertrophic cardiomyopathy):** Most common feline heart disease. Often occult until CHF or aortic thromboembolism (ATE). Diagnosed by echo: LV wall thickness >6mm. Maine Coon and Ragdoll have heritable forms (MyBPC3 mutation). - **ATE (arterial thromboembolism):** Devastating complication of feline cardiomyopathy. Acute hindlimb paralysis, pain, absent femoral pulses. Prognosis guarded; ~33% survive to discharge. - **Treatment differs from dogs:** Atenolol (beta-blocker) for HCM with obstruction or tachycardia; furosemide for CHF; clopidogrel (18.75 mg PO q24h) for ATE prevention. Pimobendan use in cats is controversial (may worsen dynamic outflow obstruction in HCM). **Equine:** - **Atrial fibrillation:** Most common clinically significant arrhythmia in horses. May be incidental in large horses or cause exercise intolerance. Treatment: quinidine sulfate (via nasogastric tube) or transvenous electrical cardioversion. - **Murmurs in horses:** Physiologic flow murmurs are common and usually benign. Functional murmurs (grade I-III, systolic) in resting horses without structural disease are often normal. - **Aortic regurgitation:** Common in older horses; usually grade I-III diastolic murmur. Monitor progression; restrict athletic work if severe. ## Limitations - This skill provides clinical reference frameworks, not patient-specific treatment plans. - Physical examination and diagnostics are required for clinical decision-making. - Referral to a board-certified specialist should be considered for complex cases. - Evidence quality varies; some recommendations are based on expert consensus rather than RCTs.