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.