Radiography, Chest x-rays
Chest x-rays are useful to evaluate the heart overall size and shape. However, the classic “valentine”-shaped heart, which is very specific for disease, is the exception rather than the rule in cats with mild or moderate asymptomatic disease.
Chest x-rays do not allow precise determination of the type of cardiomyopathy present or the heart function.
In instances when congestive heart failure (CHF) is suspected, the chest x-rays are most useful for detecting a build up of fluid (pulmonary edema or pleural effusion).
Repeating x-rays might be useful for monitoring the effectiveness of treatment for congestive heart failure (CHF).
Cardiac Blood Test, NT-proBNP (biomarkers)
The heart is an endocrine organ (in addition to its function as a pump) that produces and responds to a wide range of neuroendocrine stimuli and substances. The heart produces diuretic and natriuretic hormones called natriuretic peptides to keep the fluid balance within the circulatory system in balance.
One of the most important peptide is B-type natriuretic peptide (BNP). BNP is produced within the myocardial cells in response to stretch or stress, inadequate oxygen supply to a heart tissue and activity of other neuroendocrine pathways. BNP is produced as a precursor molecule that is subsequently cleaved into the active neurohormone, BNP, and a byproduct called N-terminal pro—B-type natriuretic peptide (NT-proBNP)
The level of BNP or NT-proBNP in the blood increases when heart failure symptoms worsen, and decreases when the heart failure condition is stable.
During NT-proBNP blood test, a small amount of blood is taken and placed in a machine that detects the level of NT-pro-BNP in the blood.
Important Note: Biomarkers in cats:
Not a test for breeding soundness!
Not for use in routine wellness examinations!
Helps determine likelihood of heart disease in cats with findings suspicious of underlying heart disease for example heart murmur, arrhythmias etc.
Helps determine the cause of disease in cats with respiratory signs for example asthma or likely heart problems
Helps encourage owners and breeders to perform additional and more definitive diagnostics, such as echocardiography
Helps achieve a diagnosis when used in conjunction with findings from other methods for example the physical examination, ECG, and radiographs
Blood pressure test
Blood pressure is measured in cats in the same manner as in humans. An inflatable cuff will be placed on the cat's tail (video) or paw (video) and standard blood pressure measuring instruments will check the pressure. It is important to keep the cat still long enough to get an accurate reading and even more important to make sure that the cat is as relaxed as possible. The owner should always try to be present when the blood pressure is measured.
It is common practice to take several readings and average them in order to have an accurate reading. It has been determined that <160 mmHg is normal based on an average of a minimum of five recordings in a quiet room.
ECG is the standard method to assess arrhythmias. ECG is one of the inexpensive diagnostics but is relatively insensitive for detection of heart enlargement and dysfunction. Many cats with underlying cardiomyopathy will have a normal ECG. If arrhythmias are detected or ECG criteria for left ventricular enlargement are met, the likelihood of underlying disease increases in the presence of these findings. However, a normal ECG still leaves much room for doubt.
Diagnosis is complicated by the fact that:
heart murmurs are relatively common in adult cats, not every cat with a murmur has underlying heart disease.
heart disease doesn’t always cause murmurs!
The most advisable course of action would be to gather additional information about heart size, function, and electrical activity through chest radiographs, electrocardiography (ECG), and echocardiography.
Heart Scan, Echocardiography
At the moment echocardiography is the best method for diagnosing cardiomyopathy. Echocardiography allows a definitive diagnosis of the specific cardiomyopathy in most cases, as well as an assessment of heart size and function. It may be able to give an indication of prognosis, for example a large left atrium would indicate that blood is starting to back up and the cat is at risk of going in to congestive heart failure. It may be possible to visualize clots or slowing of blood within the heart, which would indicate the cat is at a greater risk of a clot (ATE). However, it may not detect mildly affected cats where changes in the heart are minimal.
It is a non invasive and non painful test. The cat does not need an anaesthetic and very rarely does it require sedation. They simply have to lie on their side while their heart is scanned with an ultrasound probe.
It is a universal recommendation for any cat with a murmur to pursue further investigation using echocardiography.
Important note: A heart scans enables the risk for the individual cat to be assessed! It helps to identify carriers of the genetic mutation in breeding programmes, therefore allowing breeders to think about removing cardiomyopathy genetic material from future lines.
The pathologists look at the whole heart and also do microscopic analysis (histopathology) to identify the arrangement of the heart muscle cells and to look at fibrosis and scarring of areas within the heart in order to diagnose diseases.
It is a very painful decision for the cat owner but it is extremely important for the understanding of this condition. Unless the researcher or pathologist can look at hearts from cats that have died from this disease, we won’t know some of the really important characteristics of the heart problems in Birmans.
The researchers are extremely interested in looking at the hearts from Birman cats that:
Have cardiomyopathy and die due to heart failure or a clot;
Have cardiomyopathy but die of another cause;
Screened normal and die of another cause.