cardiology-workup

name	cardiology-workup
description	Veterinary cardiac examination and diagnostic workup including murmur grading (I-VI), arrhythmia classification, echocardiography indications, and ACVIM staging for MMVD and DCM.

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.