Expert veterinary care for every stage of your pet’s life.
Emergency: 617-522-7282
Poison Control: 888-426-4435
Bringing pets and people together.
Advocate for animals, volunteer, or get help for your pet with our compassionate community services.
It can sometimes be challenging for a pet owner to establish care with a cardiologist rapidly — partly due to difficulty in scheduling, as well as geographic or financial constraints. However, there are many tests that a general practitioner, ER doctor, or non-cardiology specialist can perform in their practice to aid in the initial diagnostic workup of heart disease. These tests can give the practitioner more confidence in their differential diagnoses and treatment plan, either allowing for full management of that patient’s heart disease or bridging the gap until a cardiologist can see the pet. This article discusses eight tools that can be utilized in practice to aid in the workup of heart disease in pets.
Obtaining a thorough history can be of vital importance in any veterinarian-client-patient relationship. This is definitely true when asking more specific, cardiovascular-focused questions in a pet who may be presenting with heart disease. Signalment can be used to generalize a patient’s potential type of heart disease. For example, chronic degenerative mitral valve disease is more common in older, smaller-breed dogs, whereas dilated cardiomyopathy tends to impact middle-aged-to-older, large-breed dogs. Many times, a pet is asymptomatic for heart disease until later, more severe stages, so it is important to try to pick up on any subtle changes before more emergent concerns arise. A thorough diet history can be helpful in both determining if diet is impacting a pet’s cardiac health, as well as determining if changes need to be made in the future.
The patient should be fully examined at each veterinary visit. There are specific areas to focus on, if there’s concern for heart disease. Evaluate the mucous membrane color and capillary refill time (CRT). Examine jugular veins for abnormalities. The femoral pulses should be palpated, and specifics should be noted regarding any normal or abnormal findings. Most importantly, cardiopulmonary auscultation should be detailed in exam notes if concerned for cardiac disease, noting abnormal heart sounds (murmur, gallop sounds, arrhythmias) and/or abnormal respiratory auscultation. These findings can be used, alongside other aspects of the history and signalment, to guide the next potential diagnostic test recommendations. Blood pressure should also be included in the standard cardiovascular physical exam, especially in specific scenarios when blood pressure is recommended to be monitored (i.e., either in patients with abnormalities consistent with hypertensive target organ damage or patients who have comorbidities that could predispose to systemic hypertension).
There may be findings on routine screening lab work that can help explain some cardiac abnormalities.
In a CBC, for example, anemia could both cause a heart murmur as well as lead to a high-output cardiac state and potentially congestive heart failure. Eosinophilia could be an indication of heartworm disease, while polycythemia could be an indication of a right-to-left shunt.
Chemistry panels can be used to detect electrolyte abnormalities (a potential cause of arrhythmias), diabetes, markers for Cushing’s disease, and of course aid in obtaining baseline or for monitoring if patients are started on cardiac medications.
Assessing a T4 can evaluate patients for hypothyroidism or hyperthyroidism, both of which can lead to secondary cardiac abnormalitiesHypothyroidism can lead to bradycardia, low voltage complexes (ECG), and decreased systolic function. Meanwhile, hyperthyroidism can cause cardiac enlargement and potentially high-output congestive heart failure (CHF), arrhythmias, and systemic hypertension.
There are also biomarkers that can help evaluate potential cardiac abnormalities.
NTproBNP can be very important in the diagnosis and monitoring of heart disease in both cats and dogs, especially the former, and there are species-specific assays available. NTproBNP is a hormone produced and secreted by cardiomyocytes in response to excess stretching of heart muscle cells. Excessive stretching of heart muscle cells is common in many forms of heart disease and in the setting of heart failure. The magnitude of NT-proBNP increase typically correlates with the severity of disease. Annual assessment of NT-pro-BNP in asymptomatic cats being seen by their primary veterinarian can allow for potential early detection of heart disease: if the NT-pro-BNP remains normal for years, then becames elevated > 100, this could be due to heart disease, and further work up (either thoracic radiographs or referral to a cardiologist) is recommended. Assessing NT-pro-BNP in cats who are presenting with respiratory signs can also help differentiate if the respiratory signs are related to heart disease and heart failure (more likely with a BNP > 270) or non-respiratory causes (if BNP < 100, this does not support a diagnosis of CHF).
NTproBNP interpretation is more challenging in asymptomatic dogs; this test should be interpreted with some caution and utilized alongside other diagnostic tools, including thoracic radiographs or focused cardiac ultrasound.
Troponin I iscan be a helpful tool for the work-up and monitoring of myocardial disease (i.e., myocarditis, pericardial effusion, myocardial infarction, ischemic injury, cardiotoxicity). Although these diseases can increase cTnI levels in dogs and cats, it is not currently considered a helpful screening test for cardiac disease in animals.
With any of these tests, further evaluation should be done to rule out or confirm a diagnosis.
An electrocardiogram (ECG or EKG) should be performed, if the practitioner has concerns about a potential arrhythmia, unexplained tachycardia, or bradycardia during a physical exam. In addition to diagnosing arrhythmias that may warrant medical or surgical treatment (e.g., pacemaker), morphology changes on the ECG can be indicative of specific types of heart disease, or raise concern for chamber enlargement or conduction abnormalities. The ECG can be saved electronically and sent to a cardiologist for consultation, if indicated.
Likely the most important tool in the workup of heart disease in primary care practice (following physical exams), thoracic radiographs can provide a vast amount of information in diagnosing the severity and guiding the treatment of heart disease. Specific tools, including vertebral heart size (VHS) and vertebral left atrial size (VLAS), have been shown to correlate with the severity of heart disease and provide some prognostic information. Thoracic radiographs also allow the practitioner to evaluate extra-cardiac structures, specifically the airways and pulmonary patterns, to either diagnose congestive heart failure (i.e., when evidence of pulmonary edema or pleural effusion is present) or assess for other reasons for respiratory symptoms.
Focused cardiac ultrasound (FCU) and lung ultrasound can be performed by non-cardiologist practitioners to aid in diagnosing specific cardiac pathology and determining the severity of heart enlargement or respiratory symptoms.
In both feline and canine patients, these tests can help differentiate cardiac from non-cardiac causes of dyspnea. For example, key FCU findings in dilated cardiomyopathy include left ventricular dilation and severe left ventricular systolic dysfunction. FCU may identify subjective right heart enlargement or septal flattening, that can be indicative of pulmonary hypertension.
In dogs, FCU can be helpful to increase or lower one’s suspicion of left-sided congestive heart failure (LCHF), which typically manifests as pulmonary edema. Key FCU features include an increased LA/Ao, and bilateral, diffuse distribution of B-lines.
In a recent study by Loughran et al., FCU performed by a trained general practitioner allowed for appropriate cardiac assessment and initial workup of patients who were presented with respiratory signs. Identification of an enlarged LA/Ao ratio of 2:1, as well as B-line artifacts on lung ultrasound (which can support the presence of pulmonary edema) and/or the presence of pleural and/or pericardial effusion, would dramatically increase the suspicion of congestive heart failure and prompt the clinician to administer a furosemide bolus as the first step in stabilizing the patient. Identification of a normal LA/Ao ratio of 1.2:1 on FCU in a dyspneic feline patient with a history of intermittent coughing episodes may increase the suspicion of primary lower airway disease.
Veterinary cardiologists are often very willing to assist referring veterinarians in any capacity. Please contact us with your questions, and we will do our best to assist you and your clients.
While primary care veterinarians can take these initial steps to evaluate their patients for cardiac abnormalities, they may also want to refer them to a board-certified cardiologist for more specialized diagnostics and treatment. In these cases, there are several basic steps to follow:
Long-term management of a patient’s cardiac disease is typically a collaborative effort between the referring/primary care veterinarian and veterinary cardiologist. Cardiologists are willing to work with you and your client to determine the best plans for each individual patient.
