# Echocardiography in Dogs and Cats: Indications and Basic Interpretation


## Key Takeaways

- Echocardiography is the gold standard for assessing cardiac structure and function in dogs and cats, indicated by clinical signs, physical exam findings (murmurs, arrhythmias), cardiomegaly on radiographs, or systemic disease with cardiac involvement.
- Key echocardiographic measurements include left ventricular internal diameter (LVIDd), left atrial to aortic root ratio (LA:Ao), interventricular septal thickness, left ventricular free wall thickness, ejection fraction (EF), and fractional shortening (FS), with species-specific normal ranges and interpretation criteria.
- Left atrial enlargement (LA:Ao > 1.6 in dogs, > 1.5 in cats) signifies chronic pressure or volume overload and is a critical prognostic indicator for adverse outcomes, including congestive heart failure and thromboembolism in cats.
- Systolic dysfunction is identified by reduced EF and FS, often seen in dilated cardiomyopathy in dogs, while preserved systolic function with hypertrophy suggests hypertrophic cardiomyopathy in cats.
- Doppler echocardiography is essential for assessing valvular function (regurgitation, stenosis) and estimating pulmonary artery pressure via tricuspid regurgitation velocity, with specific thresholds indicating likely pulmonary hypertension.
- Serial echocardiography is crucial for monitoring disease progression in conditions like myxomatous mitral valve disease and hypertrophic cardiomyopathy, and for detecting cardiotoxicity from chemotherapy agents like doxorubicin.

---

Echocardiography is the standard imaging method for structural and functional cardiac assessment in dogs and cats. This article provides the general practitioner with a framework for deciding when to recommend echocardiography, what the standard examination includes, and how to interpret the measurements most commonly used in clinical decision-making. It is written for veterinarians who perform or refer echocardiographic studies and who need to integrate the results into patient management.

The primary clinical questions addressed are whether a patient's clinical signs, physical examination findings, or thoracic radiographs justify echocardiography, what information a standard study should provide, and how to distinguish clinically significant findings from normal variation. Species differences between dogs and cats are emphasized throughout, because normal values, common diseases, and technical limitations differ substantially between them.

## At a Glance

| Parameter | Dog | Cat | Clinical Relevance |
|---|---|---|---|
| Left ventricular internal diameter in diastole (LVIDd) | 12 to 18 mm/kg indexed, breed-dependent | 11 to 17 mm absolute | Enlargement supports volume overload or dilated cardiomyopathy |
| Left atrial to aortic root ratio (LA:Ao) | Less than 1.6 | Less than 1.5 | Ratio above threshold indicates left atrial enlargement |
| Interventricular septal thickness in diastole | 6 to 12 mm, breed-dependent | 3 to 5 mm | Thickening suggests hypertrophy |
| Left ventricular free wall thickness in diastole | 6 to 12 mm, breed-dependent | 3 to 5 mm | Asymmetric thickening raises suspicion for hypertrophic cardiomyopathy |
| Ejection fraction (EF) | 40 to 60 percent | 40 to 60 percent | Reduced EF indicates systolic dysfunction |
| Fractional shortening (FS) | 25 to 45 percent | 30 to 50 percent | Low FS supports systolic failure |
| Right ventricular size | Less than 1.0 relative to left ventricle | Less than 1.0 relative to left ventricle | Enlargement suggests pulmonary hypertension or tricuspid disease |
| Pericardial effusion | Absent | Absent | Presence changes diagnostic and therapeutic approach |

## Physical Basis of Ultrasound in Cardiac Imaging

Echocardiography uses high-frequency sound waves between 2 and 12 MHz, depending on patient size and the depth of the structures being examined. The transducer emits pulses that reflect off tissue interfaces, and the returning echoes are processed to create real-time two-dimensional images. M-mode provides a single-line temporal display that allows precise measurement of wall thickness and chamber dimensions. Doppler modalities, including spectral, color, and tissue Doppler, assess blood flow velocity and direction, which permits estimation of pressure gradients and detection of valvular regurgitation or stenosis.

The physics of ultrasound impose practical limits. Air is a poor conductor of ultrasound, so the examination requires acoustic coupling gel and firm transducer contact with a clipped area of the thorax. The heart lies within the ribcage, and the lungs and bone block ultrasound, so imaging windows are limited to areas where the heart contacts the thoracic wall directly. The right parasternal window is the standard approach in both dogs and cats, with the left parasternal window used for specific views of the left heart and great vessels. The American College of Veterinary Radiology provides resources on imaging standards and safety that apply to echocardiography as an ultrasound-based modality [ACVR resources on diagnostic imaging practice](https://acvr.org/).

## Indications for Echocardiography

Echocardiography is indicated when clinical findings suggest structural heart disease, when a murmur or arrhythmia requires characterization, when thoracic radiographs show cardiomegaly or pulmonary edema of suspected cardiac origin, and when systemic disease with cardiac involvement is suspected. The MSD Veterinary Manual describes the clinical approach to cardiac disease in dogs and cats, including the role of imaging in confirming suspected diagnoses [MSD Veterinary Manual professional reference](https://www.msdvetmanual.com/).

Specific indications include a new or changing heart murmur, particularly a left apical systolic murmur in a cat, which raises suspicion for hypertrophic cardiomyopathy. A dog with a diastolic murmur or a continuous murmur warrants echocardiography to identify valvular or congenital lesions. Syncope, unexplained weakness, or exercise intolerance with a cardiac murmur or arrhythmia justifies imaging. Systemic hypertension, hyperthyroidism in cats, and chronic kidney disease are conditions in which echocardiography can document secondary cardiac changes.

Echocardiography is also indicated for monitoring. Patients with known myxomatous mitral valve disease should be re-evaluated when clinical signs progress or when therapy is adjusted. Cats with hypertrophic cardiomyopathy benefit from serial studies to track left atrial enlargement, which predicts congestive heart failure risk. Dogs receiving doxorubicin chemotherapy require baseline and serial echocardiograms to detect systolic dysfunction before clinical heart failure develops.

## Standard Echocardiographic Views

The complete examination uses a consistent sequence of imaging planes. From the right parasternal window, the long-axis four-chamber view provides an overall assessment of chamber sizes and wall motion. The long-axis left ventricular outflow tract view displays the aortic valve and ascending aorta. The short-axis views at the level of the papillary muscles, chordae tendineae, and mitral valve allow M-mode measurements of the left ventricle and assessment of regional wall motion. The short-axis view at the aortic root permits measurement of the left atrium and aorta in the same frame, yielding the LA:Ao ratio.

From the left parasternal window, the apical four-chamber view is used for Doppler assessment of transmitral and pulmonary venous flow. The left cranial parasternal view provides access to the pulmonary artery and the right ventricular outflow tract, which is necessary for measuring pulmonary flow velocities and detecting pulmonic stenosis.

## Basic Measurement Principles

M-mode measurements of the left ventricle are obtained from the short-axis view at the level of the chordae tendineae, with the cursor positioned perpendicular to the interventricular septum and left ventricular free wall. Measurements include interventricular septal thickness in diastole and systole, left ventricular internal diameter in diastole and systole, and left ventricular free wall thickness in diastole and systole. From these, fractional shortening is calculated as the difference between diastolic and systolic internal diameter divided by the diastolic diameter, expressed as a percentage.

Two-dimensional measurements are preferred for the left atrium because M-mode can underestimate left atrial size when the atrium is asymmetrically enlarged. The LA:Ao ratio is measured from the short-axis view at the aortic root, comparing the diameter of the left atrium to the diameter of the aorta in early diastole. This ratio is a robust indicator of left atrial enlargement and carries prognostic significance in both dogs and cats.

Doppler echocardiography measures blood flow velocities across valves and within chambers. The peak velocity of mitral inflow during early diastole (E wave) and during atrial contraction (A wave) provides information about diastolic function. The E:A ratio normally exceeds 1 in dogs but is variable in cats. Tissue Doppler imaging of the mitral annulus adds information about myocardial relaxation that is less load-dependent than transmitral flow alone.

## Indications for Referral and Advanced Imaging

Echocardiography performed by a general practitioner identifies structural and functional abnormalities, but certain findings warrant referral to a veterinary cardiologist or a facility with advanced imaging capabilities. Referral is indicated when the echocardiogram reveals complex congenital malformations, suspected cardiac masses, pericardial effusion with suspected neoplasia, or when Doppler interrogation suggests severe pulmonary hypertension that may require targeted therapy. The [American College of Veterinary Radiology resources](https://acvr.org/) outline specialty standards for diagnostic imaging that support referral when image quality or interpretive confidence is limited.

Referral is also appropriate when the echocardiogram is technically difficult, when the patient is unstable, or when the clinical picture and echocardiographic findings conflict. A cat with respiratory distress and a normal echocardiogram may have noncardiogenic causes, and a dog with a loud murmur but equivocal measurements may need advanced assessment. In these situations, the cardiologist can perform transesophageal echocardiography, contrast studies, or tissue Doppler imaging that may not be available in general practice.

## Normal Reference Ranges and Their Limitations

Reference ranges for echocardiographic measurements vary with body weight, breed, age, and species. Published values from the [MSD Veterinary Manual](https://www.msdvetmanual.com/) provide a starting point, but the interpreting clinician must account for the individual patient. Body weight is the strongest predictor of cardiac chamber dimensions in dogs, and breed-specific differences are substantial. A Great Dane and a Chihuahua have different normal left ventricular internal diameters at the same body weight index.

| Measurement | Dog (typical range) | Cat (typical range) | Clinical Significance |
|---|---|---|---|
| Left ventricular internal diameter in diastole (LVIDd) | 2.5 to 4.5 cm depending on weight | 1.2 to 1.8 cm | Increased in dilated cardiomyopathy, volume overload |
| Left ventricular internal diameter in systole (LVIDs) | 1.5 to 3.0 cm depending on weight | 0.6 to 1.2 cm | Increased with systolic dysfunction |
| Interventricular septal thickness in diastole (IVSd) | 0.6 to 1.2 cm | 0.3 to 0.6 cm | Increased in hypertrophy |
| Left ventricular free wall thickness in diastole (LVFWd) | 0.6 to 1.2 cm | 0.3 to 0.6 cm | Increased in hypertrophy |
| Left atrial to aortic root ratio (LA/Ao) | Less than 1.6 | Less than 1.5 | Increased with left atrial enlargement |
| Ejection fraction (EF) | 40 to 60 percent | 40 to 60 percent | Decreased in systolic dysfunction |
| Fractional shortening (FS) | 25 to 45 percent | 30 to 50 percent | Decreased in systolic dysfunction |

These ranges are guidelines, not absolute thresholds. A dog with borderline left atrial enlargement and respiratory signs may still have clinically significant disease, while a cat with a mildly thickened ventricular wall may have physiologic hypertrophy from age or hyperthyroidism. The echocardiogram must be interpreted in the context of signalment, clinical signs, blood pressure, and other diagnostic tests.

## Decision Tree for Common Cardiac Diseases

The following decision framework prioritizes the most common echocardiographic presentations in dogs and cats. It assumes a complete standard examination has been performed and that image quality is adequate.

### Step 1: Assess Left Atrial Size

Measure the LA/Ao ratio from the right parasternal short-axis view. If the ratio is less than 1.5 in cats or 1.6 in dogs, left atrial size is normal. If the ratio exceeds these values, left atrial enlargement is present. Left atrial enlargement indicates chronic pressure or volume overload and is a predictor of adverse outcomes in both species.

### Step 2: Assess Left Ventricular Wall Thickness

Measure IVSd and LVFWd in diastole. Normal wall thickness in cats is less than 0.6 cm. Values above this threshold indicate hypertrophy. In dogs, wall thickness must be indexed to body weight. Concentric hypertrophy with a normal or small ventricular chamber suggests hypertrophic cardiomyopathy in cats or physiologic hypertrophy in dogs. Eccentric hypertrophy with chamber dilation suggests volume overload.

### Step 3: Assess Systolic Function

Calculate fractional shortening and ejection fraction. Reduced systolic function with a dilated left ventricle indicates systolic dysfunction, most commonly dilated cardiomyopathy in dogs. Preserved systolic function with hypertrophy supports a diagnosis of hypertrophic cardiomyopathy in cats. Hyperdynamic systolic function with a small ventricular chamber may indicate hypovolemia or tachycardia.

### Step 4: Integrate Doppler Findings

If mitral regurgitation is present, assess its severity with color Doppler. Trace the regurgitant jet area relative to left atrial area. Severe mitral regurgitation with a large jet area and left atrial enlargement supports degenerative mitral valve disease in dogs. If aortic outflow velocity is increased, consider aortic stenosis. If tricuspid regurgitation velocity exceeds 3.0 m per second in dogs or 2.8 m per second in cats, pulmonary hypertension is likely.

### Step 5: Correlate With Clinical Findings

The echocardiogram never stands alone. A dog with a grade III left apical systolic murmur, LA/Ao of 1.8, and normal systolic function has degenerative mitral valve disease. A cat with a gallop rhythm, LA/Ao of 2.0, and severe concentric hypertrophy has hypertrophic cardiomyopathy. A dog with weakness, a dilated left ventricle, and fractional shortening of 15 percent has dilated cardiomyopathy. When the echocardiogram and clinical findings disagree, repeat the examination or seek a second opinion.

## Monitoring Parameters and Serial Assessment

Serial echocardiography is indicated for patients with known cardiac disease, for patients receiving cardiotoxic chemotherapy, and for breeds predisposed to inherited cardiomyopathy. The interval between examinations depends on disease severity and clinical stability.

For dogs with degenerative mitral valve disease, repeat echocardiography is recommended when clinical signs change, when a new arrhythmia is detected, or when thoracic radiographs show progressive cardiomegaly or pulmonary edema. The key parameters to track are LA/Ao ratio, left ventricular internal diameter in diastole, and estimated pulmonary artery pressure from tricuspid regurgitation velocity.

For cats with hypertrophic cardiomyopathy, repeat echocardiography is indicated when clinical signs progress, when congestive heart failure develops, or when aortic thromboembolism is suspected. The LA/Ao ratio is the most important serial measurement because it predicts thromboembolic risk. Cats with an LA/Ao ratio above 2.0 have a substantially higher risk of arterial thromboembolism than cats with a ratio below 1.5.

For dogs receiving doxorubicin or other cardiotoxic agents, echocardiography should be performed before each dose or according to the protocol recommended by the [American Veterinary Medical Association practice resources](https://www.avma.org/resources-tools). A decrease in fractional shortening of more than 10 percentage points from baseline, or an absolute value below 25 percent, warrants discontinuation of the cardiotoxic agent and cardiology consultation.

## Documentation and Reporting

A complete echocardiographic report should include patient identification, signalment, body weight, heart rate, and rhythm. The report must list all measured values with the reference range used, describe the image quality and any limitations, and state the echocardiographic diagnosis. Include a subjective description of chamber sizes, wall thickness, valvular morphology, and pericardial space. Doppler findings should be reported with measured velocities and the derived pressure gradients.

The report should also include a comparison with any previous echocardiograms. State whether the findings are stable, improved, or progressive. This comparison is essential for monitoring disease progression and for adjusting therapy. The report should end with a recommendation for the next examination interval and any additional diagnostic tests that are indicated.

Store all echocardiographic images and loops in the patient record. Digital storage allows retrospective review, comparison with future studies, and consultation with a cardiologist. The [American College of Veterinary Radiology resources](https://acvr.org/) provide guidance on image archiving and quality standards that support consistent documentation across practices.

## Species-Specific Considerations

Feline echocardiography differs from canine echocardiography in several practical ways. Cats require chemical restraint more often than dogs, particularly when they are fractious or when the examination is prolonged. Acepromazine or butorphanol may be used, but these agents can alter heart rate and cardiac output, so measurements should be interpreted with caution. Cats also have a higher heart rate, which makes timing of diastolic measurements more challenging. The examiner should obtain multiple cardiac cycles and average the measurements.

Dogs are usually examined without sedation, but anxious or dyspneic dogs may benefit from light sedation. The examiner must balance the need for patient cooperation against the effect of sedatives on cardiac function. In both species, the examination should be performed with the patient in lateral recumbency on a table with a cutout that allows transducer access from below. The right parasternal views are obtained first, followed by the left apical and left cranial views.

Body condition affects image quality. Obese patients have increased attenuation from subcutaneous fat, and patients with deep-chested conformations may require adjustment of transducer position. The examiner should document any technical limitations that affect measurement accuracy.

## Recognized Complications and Early Detection

Echocardiography is minimally invasive, but complications occur. The most common is sedation-related cardiovascular depression. Dogs with occult cardiomyopathy or cats with hypertrophic cardiomyopathy may decompensate under sedation. Detect this early by monitoring blood pressure and heart rate continuously during the study. If systolic pressure falls below 90 mmHg in dogs or 80 mmHg in cats, or if arrhythmias appear, stop the examination and allow recovery.

Vagal events from transducer pressure on the thoracic inlet can produce bradyarrhythmias, particularly in cats. Release pressure immediately and observe rhythm recovery. Cats may also develop respiratory distress from prolonged lateral recumbency, especially those with pre-existing airway disease. Limit examination time and use minimal restraint.

Ultrasound gel contact dermatitis is rare but recognized. Wipe gel thoroughly after the study, particularly in patients with thin skin or dermatologic disease. The ACVR professional resources on diagnostic imaging practice emphasize standard equipment care and operator safety, including transducer disinfection between patients [American College of Veterinary Radiology resources](https://acvr.org/).

## Common Errors and Corrective Actions

| Observation | Likely Cause | Discriminating Check |
|---|---|---|
| Left atrial dimension reads falsely large | Off-axis imaging plane through the atrium | Confirm the left atrium is visualized in its maximal dimension with the interatrial septum parallel to the transducer face |
| Aortic root appears small | Incorrect timing in the cardiac cycle | Measure at end-diastole, at the onset of the QRS complex |
| Mitral E wave exceeds A wave in a cat | Heart rate above 160 beats per minute causes E and A wave fusion | Re-evaluate at a slower heart rate or use tissue Doppler imaging |
| Left ventricular internal diameter appears reduced | Foreshortening of the ventricle from a non-apical imaging plane | Ensure the true apex is included in the image sector |
| Wall thickness appears increased | Oblique section through the ventricular wall | Confirm the M-mode cursor is perpendicular to the septum and free wall |

The most frequent error in basic interpretation is measuring the left atrium and aorta at different points in the cardiac cycle. The left atrium should be measured at end-ventricular systole, just before mitral valve opening, while the aorta is measured at end-diastole. Using the same frame for both measurements introduces systematic error.

A second common error is accepting a single measurement as diagnostic. Borderline values should be repeated across three to five cardiac cycles and averaged. Respiratory variation in intrathoracic pressure alters venous return and chamber dimensions, so measurements taken during a breath hold differ from those taken during quiet respiration.

## Limitations of Current Evidence

Normal reference ranges for canine and feline echocardiography derive largely from single-center studies with modest sample sizes. Breed-specific variation is substantial, particularly in sighthounds, boxers, and Maine coon cats. Published ranges may misclassify an individual animal as normal or abnormal when breed-specific values would change the interpretation. The MSD Veterinary Manual professional edition provides species-specific reference values and cautions that ranges must be interpreted in light of signalment and clinical context [MSD Veterinary Manual professional edition](https://www.msdvetmanual.com/).

Expert opinion still differs on the threshold for initiating therapy in preclinical myxomatous mitral valve disease. Some cardiologists treat when left atrial enlargement is detected, while others wait for clinical signs. The evidence base for early intervention in dogs is evolving, and current recommendations reflect expert consensus instead of definitive trial data.

Feline hypertrophic cardiomyopathy presents a similar problem. The distinction between physiologic hypertrophy in athletic cats and pathologic hypertrophy can be difficult, and no single measurement reliably separates them. Serial assessment and Doppler evaluation of diastolic function provide additional information, but diagnostic certainty is not always achievable.

## When to Refer, Consult, or Report

Referral to a cardiologist is appropriate when the general practitioner cannot obtain diagnostic images, when measurements are borderline and clinical decisions hinge on small differences, or when complex congenital disease is suspected. A board-certified cardiologist brings advanced training in Doppler interrogation, transoesophageal imaging, and interventional procedures. The AVMA practice resources describe the scope of specialty referral and the importance of clear communication between primary and referral veterinarians [AVMA practice resources](https://www.avma.org/resources-tools).

Laboratory consultation is warranted when echocardiographic findings suggest an extracardiac cause. For example, a cat with severe concentric hypertrophy and concurrent hypertension requires blood pressure measurement and thyroid hormone testing. A dog with pericardial effusion and a cardiac mass may need cytology or histopathology, which requires referral to a pathologist.

Regulatory reporting obligations are uncommon in companion animal echocardiography. However, if an echocardiogram is performed as part of a pre-purchase examination for a breeding animal, the findings may have contractual implications. In production animal settings, cardiac disease may trigger food safety considerations, and the WOAH terrestrial animal health standards address disease surveillance and reporting obligations that vary by jurisdiction [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). Veterinarians should confirm local requirements before acting on incidental cardiac findings in food-producing species.

## Frequently Asked Questions

### How Much Does an Echocardiogram Cost, and How Should I Discuss This With a Client?

Cost varies widely with region, facility type, and whether a boarded cardiologist or general practitioner performs the study. A complete examination with Doppler typically costs more than a limited screening study, and emergency or mobile services carry additional fees. When discussing cost with a client, frame the echocardiogram as a diagnostic investment that directly guides therapy, prognosis, and monitoring frequency. Explain that a single study can prevent costly and ineffective treatments for conditions it rules out. For clients with financial constraints, offer a staged approach: a focused study to answer the immediate clinical question, with a full examination deferred. Professional practice resources from the [American Veterinary Medical Association](https://www.avma.org/resources-tools) can help you structure fee discussions and informed consent documents.

### What Can I Do When a Full Echocardiogram Is Not Feasible in My Practice?

When complete equipment or expertise is unavailable, a focused cardiac ultrasound is still valuable. Use a phased-array probe if available, but a microconvex probe can acquire diagnostic images in many dogs and cats. Prioritize the right parasternal long-axis four-chamber view for left atrial to aortic root ratio and subjective systolic function. Record cine loops for offline review or telemedicine consultation. If you cannot obtain interpretable images, do not guess. Refer the patient for a complete study, because a poor-quality study that misses severe disease is worse than no study. The [American College of Veterinary Radiology](https://acvr.org/) maintains resources on imaging standards and can help identify specialists in your region.

### How Does Echocardiographic Interpretation Differ Between Dogs and Cats?

The most important species difference is the prevalence and phenotype of disease. Cats with hypertrophic cardiomyopathy typically show symmetric or asymmetric left ventricular wall thickening with normal or hyperdynamic systolic function, and left atrial enlargement is a key prognostic marker. Dogs more often present with myxomatous mitral valve disease or dilated cardiomyopathy, so chamber enlargement and systolic dysfunction dominate the differential list. Normal reference ranges differ substantially between species and, in dogs, by breed. A greyhound or other sighthound may have a larger left ventricular internal diameter and lower fractional shortening than a non-sighthound without being diseased. Always interpret measurements against species-appropriate and breed-appropriate references, and consult the [MSD Veterinary Manual](https://www.msdvetmanual.com/) for species-specific normal values and disease descriptions.

### How Should I Document an Echocardiogram in the Medical Record?

Record the indication, the views obtained, the machine settings including transducer frequency and depth, and every measurement with the view and cardiac cycle used. Store at least one cine loop per standard view, also still frames, because motion is essential for assessing wall motion and valve morphology. Note the heart rate and rhythm during acquisition, since tachycardia or arrhythmia alters measurements. Write a structured report that separates findings from interpretation, and state a specific echocardiographic diagnosis or differential list. Include a comparison with any prior study and a recommendation for recheck interval. This documentation supports serial assessment, medicolegal defense, and continuity of care if the patient is referred to a cardiologist.

### How Do I Explain an Abnormal Echocardiogram to a Client Without Causing Panic?

Start with what the heart is doing well before discussing what is abnormal. Use a simple analogy, such as describing the heart as a pump with four rooms and four doors, and explain which room or door shows a problem. Give the client a written summary with the diagnosis, the clinical stage of disease, and the treatment plan in plain language. Distinguish between an anatomic abnormality and current clinical signs, because a cat with mild hypertrophy may need no therapy, while a dog with severe mitral regurgitation needs medication. Emphasize that echocardiography provides a baseline for monitoring, not a single verdict. Offer a follow-up call or recheck appointment to answer questions that arise after the client has processed the information.

### When Should I Repeat an Echocardiogram, and What Interval Is Appropriate?

The recheck interval depends on the disease, its severity, and whether therapy has changed. For stable myxomatous mitral valve disease in dogs, reassess when clinical signs progress or when radiographic heart size increases. For cats with asymptomatic hypertrophic cardiomyopathy, repeat the study every 12 to 24 months, or sooner if left atrial enlargement is present. After starting or adjusting cardiac medication, a recheck in 2 to 4 weeks can confirm the expected effect on chamber size or function. For patients with suspected pulmonary hypertension or pericardial effusion, repeat sooner, guided by clinical status. Serial studies are most useful when performed by the same operator with consistent technique, so note the operator and machine in each report.

## Related Clinical & Scientific Guides

* [MRI Monitoring of Brain Tumor Response to Therapy in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/mri-monitoring-brain-tumor-response-therapy-dogs)
* [Ultrasound-Guided Drainage of Abscesses in Small Animals](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-drainage-abscesses-small-animals)
* [Radiographic Monitoring of Total Hip Replacement in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-monitoring-total-hip-replacement-dogs)


## References and Further Reading

- [Percutaneous replacement of pulmonary valve in a right-ventricle to pulmonary-artery prosthetic conduit with valve dysfunction.](https://pubmed.ncbi.nlm.nih.gov/11052583/). 2000.
- [American College of Veterinary Radiology Resources](https://acvr.org/). American College of Veterinary Radiology.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.
- [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association.
- [WOAH Terrestrial Animal Health Code](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/). WOAH.

## Related Articles

- [Dental Radiography Positioning and Interpretation in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/dental-radiography-positioning-interpretation-dogs-cats)
- [Radiographic Assessment of Fracture Healing in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-assessment-fracture-healing-dogs-cats)
- [Systematic Interpretation of Thoracic Radiographs in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/systematic-interpretation-thoracic-radiographs-dogs-cats)
- [Veterinary CT Angiography: Indications and Interpretation](/knowledge/veterinary-medicine/diagnostic-imaging/veterinary-ct-angiography-indications-interpretation)
- [Radiographic Evaluation of Feeding Tube Placement in Dogs and Cats](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-evaluation-feeding-tube-placement-dogs-cats)

> This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.