Home / Practice / Veterinary: echocardiography (cats, dogs)

How an echocardiogram is done in dogs and cats

In veterinary practice an echocardiogram is done for a heart murmur, dyspnea, syncope, before anesthesia in older animals and as part of breed screening: Cavaliers and Dachshunds for mitral valve disease, Dobermans for cardiomyopathy, Maine Coons and British Shorthairs for hypertrophic cardiomyopathy. The report has a lot of numbers, some of them come from formulas, and normal values depend on species and body weight. Here is how the exam goes and where the time goes.

What is examined

The animal lies in right lateral recumbency on a table with a cutout, and the probe is placed from below: this way the heart rests against the chest wall and the lung moves out of the window. Long and short axis views are acquired from the right parasternal position, then the animal is turned onto its left side for the left apical views. The coat over the window is clipped or parted and soaked with alcohol and gel. A simultaneous ECG helps pick the right phase of the cardiac cycle.

A phased array probe is used: 7-12 MHz for cats and small dogs, 5-7 for medium dogs, 2-4 MHz for large and giant breeds. Cats are restrained gently and without hurry: in a frightened animal the heart rate climbs to a point where diastole is hard to assess and the E and A waves merge. Sedation is used with caution and only on the clinician's decision, as it changes the heart rate and some of the measurements.

In the short axis view at the level of the chordae, M-mode is used to measure the interventricular septum, the LV internal diameter and the LV posterior wall in diastole and in systole. Fractional shortening and Teichholz ejection fraction are calculated from these dimensions. In dogs the chamber dimensions are also normalized to body weight with an allometric formula, because an LVIDd of forty millimeters is normal for a Labrador and markedly enlarged for a Dachshund.

At the heart base the left atrium and aorta are measured in 2D and the LA/Ao ratio is calculated, the simplest and most reliable sign of left heart volume overload. Then Doppler: transmitral flow with E and A waves, mitral and tricuspid regurgitation, aortic and pulmonic velocities. Tricuspid regurgitation velocity is used to estimate pulmonary artery pressure. Finally the right heart, the pericardium for effusion, and the rhythm are assessed.

• Heart rate during the exam and rhythm
• LV in M-mode: IVS, LVID, posterior wall in diastole and systole
• Fractional shortening and ejection fraction
• Weight-normalized LVIDd and LVIDs (dogs)
• Left atrium, aorta and LA/Ao ratio
• Mitral valve, regurgitation grade, E and A waves
• Tricuspid valve and regurgitation velocity
• Aortic and pulmonic valves, flow velocities, right heart, pericardium

How long it takes

The exam itself takes fifteen to twenty-five minutes, longer with a nervous cat: you have to wait until the animal settles and the heart rate comes down. The report is heavy: about twenty measurements, fraction calculations, weight normalization for dogs, LA/Ao and valve descriptions. Typing it by hand adds another fifteen minutes, and many people compute the normalized dimensions on a calculator or skip them. With six to eight echos a day, typing takes an hour and a half to two hours.

The same study by voice

Species, breed, weight, age and sex go into the study record in advance and are not dictated, but the report needs the weight for normalization. After that the veterinarian names the parameter and the number, while fractions, LA/Ao, E/A and normalized dimensions are calculated automatically. Below is the dictation from a real case: a thirty-kilogram Labrador, murmur heard at a consultation, echo before elective surgery. Play it in full or click individual lines.

Abbreviations are recognized as terms: IVS, LVID and LA go into their rows. Calculated fields are not dictated: fractional shortening, ejection fraction, LA/Ao, E/A and weight-normalized dimensions appear as soon as the source numbers are dictated. If the weight in the record or the LVIDd is corrected later, all dependent values are recalculated. Reference values next to the numbers are split by species, so a dog's normal range never gets mixed up with a cat's.

Reference values in the protocol are split by species: FS 25-45 % in dogs and 35-65 % in cats; LA/Ao below 1.6 in dogs and below 1.5 in cats; in cats LVIDd up to 18 mm, posterior wall up to 5-6 mm, LA up to 16 mm. In dogs LVIDd and LVIDs are assessed after weight normalization: below 1.85 and 1.26 respectively. Normal tricuspid regurgitation velocity is below 2.8 m/s. Breed specifics and the clinical picture matter more than any single number, and interpretation always belongs to the veterinarian.

What the finished document looks like

The finished document is built from the same data. The table suits the cardiologist and makes follow-up comparison easy, which matters especially in mitral valve disease. The narrative version is used for the owner and for the veterinarian who will manage the patient going forward.

Frequent questions

What it changes on a shift

In echocardiography most errors happen not in the measurements but in the calculations that follow. When fractions, LA/Ao and weight normalization are computed with the same formula for every patient, the veterinarian works with the probe instead of a calculator, and the report is ready while the owner is putting the leash back on.

The first 15 reports are free. After that the price depends on the pack size: from 0.42 to 0.53 USD per report, whatever the length of the dictation. No subscription.

App file

Point your phone camera: the download page with the file and its checksum.

Open →

More from practice