Veterinary Cardiology: Heart Disease and Cardiac Care for Animals

Veterinary cardiology is the specialty discipline concerned with diagnosing and managing diseases of the heart, pericardium, and great vessels in animals. This page covers the scope of the specialty, the diagnostic and treatment frameworks cardiologists apply, the most common cardiac conditions encountered across species, and the clinical thresholds that separate general practice management from specialist-level intervention. Cardiac disease ranks among the leading causes of morbidity in companion animals, making familiarity with this field relevant across the broader landscape of veterinary specialties.

Definition and Scope

Veterinary cardiology is a board-certified specialty recognized by the American Board of Veterinary Practitioners (ABVP) and, more specifically, governed through the American College of Veterinary Internal Medicine (ACVIM), Cardiology Specialty. Diplomates of the ACVIM (Cardiology) complete a minimum of 3 years of residency training after a general internship, with board certification contingent on passing written and practical examinations administered by ACVIM.

The specialty encompasses:

• Congenital cardiac disease — structural defects present at birth, including patent ductus arteriosus (PDA), pulmonic stenosis, and ventricular septal defects
• Acquired cardiac disease — conditions developing over the animal's lifetime, most prominently myxomatous mitral valve disease (MMVD) and dilated cardiomyopathy (DCM)
• Pericardial disease — effusions, constrictive pericarditis, and masses affecting the pericardial sac
• Arrhythmias — rhythm disturbances ranging from benign incidental findings to life-threatening ventricular tachycardia
• Cardiac tumors — including hemangiosarcoma and chemodectoma in dogs

Species scope extends beyond dogs and cats to include horses, birds, exotics, and zoo animals, though the clinical literature is most developed for small animal patients. The exotic and zoo animal veterinary care context introduces additional complexity because reference intervals for cardiac parameters differ substantially by species.

The ACVIM's 2019 Consensus Guidelines on MMVD in dogs represent a landmark published framework, establishing standardized staging criteria (Stages A through D) that stratify patients by disease severity and guide treatment decisions across the profession (ACVIM Consensus Statement, Boswood et al., revised 2019).

How It Works

Cardiac evaluation in veterinary medicine follows a structured diagnostic sequence:

1. History and physical examination — Auscultation for murmurs graded on the Levine 1–6 scale, detection of arrhythmias, and assessment of pulse quality and jugular distension
2. Thoracic radiography — Evaluation of cardiac silhouette size using the vertebral heart scale (VHS), pulmonary vasculature, and evidence of congestive heart failure (pulmonary edema or pleural effusion)
3. Echocardiography — Two-dimensional, M-mode, and Doppler ultrasound to assess chamber dimensions, wall thickness, valve morphology, and blood flow velocity; this is the cornerstone diagnostic tool in veterinary cardiology
4. Electrocardiography (ECG/EKG) — Identification of rhythm abnormalities; ambulatory (Holter) monitoring provides 24-hour recordings for intermittent arrhythmia detection
5. Biomarkers — NT-proBNP and cardiac troponin I are validated markers used to screen for cardiac disease and monitor disease progression; reference laboratories such as IDEXX and Antech publish species-specific reference intervals
6. Blood pressure measurement — Hypertension is both a cause and consequence of cardiac disease; the ACVIM has published consensus guidelines on hypertension thresholds in dogs and cats

Treatment modalities divide into medical management and interventional or surgical procedures. Medical management relies on agents such as pimobendan (a positive inotrope and vasodilator), furosemide (diuretic for fluid overload), enalapril or benazepril (ACE inhibitors), and antiarrhythmic drugs such as sotalol or mexiletine. Interventional options include balloon valvuloplasty for pulmonic stenosis and surgical PDA ligation, procedures that require advanced imaging and often referral to a veterinary surgery service or academic center.

Diagnostic imaging plays a central role throughout; the framework connecting cardiology to veterinary radiology and imaging is operationally significant because thoracic radiography and echocardiography are interpreted in tandem during staging.

Common Scenarios

Myxomatous Mitral Valve Disease (MMVD) in Dogs
MMVD accounts for approximately 75% of cardiac disease in dogs, according to ACVIM consensus data. Cavalier King Charles Spaniels carry the highest breed prevalence, with mitral murmurs detectable in over 50% of the breed by age 5 (ACVIM Consensus Statement 2019). The condition progresses through ACVIM Stages B1 (murmur, no cardiac enlargement) to D (refractory heart failure).

Dilated Cardiomyopathy (DCM) in Dogs
DCM involves progressive myocardial failure leading to chamber dilation and reduced contractility. Doberman Pinschers and Boxers are disproportionately affected. The FDA's Center for Veterinary Medicine (FDA-CVM) issued ongoing investigations beginning in 2018 examining a possible association between grain-free diets and DCM, a regulatory matter that intersects veterinary nutrition and dietary counseling.

Hypertrophic Cardiomyopathy (HCM) in Cats
HCM is the most prevalent cardiac disease in cats, characterized by left ventricular wall thickening. Maine Coons and Ragdolls carry identified genetic mutations (MYBPC3). A significant complication is aortic thromboembolism (ATE), which presents acutely and constitutes an emergency managed under veterinary emergency and critical care protocols.

Congenital Defects
PDA, the most common surgically correctable congenital defect in dogs, is amenable to interventional closure via catheter-based coil or Amplatz occluder devices at referral centers. Pulmonic stenosis, graded by peak Doppler gradient (mild <50 mmHg, moderate 50–80 mmHg, severe >80 mmHg), drives balloon valvuloplasty decisions.

Decision Boundaries

The clinical thresholds separating general practitioner management from cardiology referral are defined through published consensus and standard-of-care frameworks:

• ACVIM Stage B2 MMVD — Patients meeting criteria for B2 (radiographic or echocardiographic evidence of cardiac enlargement) are candidates for pimobendan initiation; this staging determination requires echocardiography, which in most general practices necessitates referral
• Doppler gradient ≥80 mmHg in pulmonic stenosis — This threshold, established in ACVIM literature, marks the boundary at which balloon valvuloplasty is indicated
• Holter monitoring — Dobermans with >300 ventricular premature contractions (VPCs) per 24-hour recording meet the threshold for antiarrhythmic therapy per published cardiology guidelines
• Pleural effusion or pulmonary edema on radiography — Represents congestive heart failure requiring immediate intervention regardless of prior staging

Contrast between Stage B1 and B2 MMVD is operationally significant: B1 patients require monitoring but no cardiac medication, while B2 patients meeting ACVIM 2019 criteria (left atrium to aorta ratio ≥1.6 on echo, or VHS >10.5 on radiograph in most breeds) warrant treatment initiation.

Veterinary internal medicine specialists overlap with cardiologists in managing systemic consequences of heart disease, including secondary hypertension, renal compromise (cardiorenal syndrome), and protein-losing conditions that complicate treatment planning. The distinction lies in scope: internists manage multi-system disease, while cardiologists focus on the cardiac lesion itself and its hemodynamic consequences.

Board certification status is verifiable through the ACVIM's public diplomate directory at acvim.org, and veterinary board certification and credentials provides broader context on how specialty designations are structured across veterinary disciplines.

References

• American College of Veterinary Internal Medicine (ACVIM) — Consensus Statements
• ACVIM 2019 Consensus Guidelines on Myxomatous Mitral Valve Disease in Dogs (Boswood et al.)
• FDA Center for Veterinary Medicine — Investigation into Potential Link Between Diet and Canine DCM
• American Veterinary Medical Association (AVMA) — Veterinary Specialties
• ACVIM Diplomate Directory