What is Austin Flint Murmur?

The Austin Flint murmur, first identified by the American doctor Austin Flint in 1862, is a particular type of heart sound. Using his unique description, he compared it to the “blubbering sound” you hear when your lips or tongue vibrate as you breathe. Modern descriptions usually describe the noise as a low-pitched rumbling sound that occurs midway to later in the heart’s relaxation phase. This sound is best heard at the tip of the heart and often indicates a severe backflow of blood into the aorta, the body’s main artery.

What Causes Austin Flint Murmur?

Previous research suggested that the Austin Flint murmur, a specific heart sound, was not linked to fast blood flow through the mitral valve as found in a study using echocardiogram. The researchers of that study believed the murmur was in fact caused only by the backflow of blood from the aortic valve.

In another study that also used echocardiograms, it was found that the sound of the murmur comes from the clash of the backflowing blood from the aortic valve against the outer lining of the left lower heart chamber, also known as the left ventricular epicardium.

Earlier research thought the Austin Flint murmur was caused by the same backflow of blood from the aortic valve hitting the leaf of the mitral valve causing it to quiver. They hypothesized that this quivering creates waves and vibrations that alter the backflow of blood from the aortic valve, resulting in the specific sound known as the Austin Flint murmur.

In the end, there isn’t a universally agreed-upon explanation for the sound known as the Austin Flint murmur.

Risk Factors and Frequency for Austin Flint Murmur

The Austin Flint murmur is a heart sound that you’d expect to see commonly in people with severe aortic regurgitation. However, in a study, it was found that less than 1% of people under 70 years old had moderate to severe aortic regurgitation. Those aged 70 to 83 had a slightly higher incidence of 2.2% for men and 2.3% for women. But it’s important to note that not everyone with severe aortic regurgitation will have an Austin Flint murmur. Because of this, we don’t really know how common the murmur is.

Signs and Symptoms of Austin Flint Murmur

The Austin Flint murmur is a specific kind of heart murmur linked with severe aortic regurgitation. It’s a sort of noise that the heart makes, which doctors can hear using a stethoscope. This sound is most noticeable in the heart’s apex (the lower pointed edge of the heart). Normally, this sound can be best detected near the fifth rib space at the center line of collarbone.

Younger patients with this condition often have a history of abnormal aortic valve or rheumatic heart disease. On the other hand, older individuals tend to have calcium build-up on their aortic valve. When a doctor takes the blood pressure of a patient with Austin Flint murmur, they might observe an increased gap between the systolic and diastolic blood pressure numbers. This is due to the blood flowing backward through the aortic valve.

Interestingly, a clinician may feel a unique type of pulse in the patient, known as the “water hammer” pulse or “Corrigan’s pulse”. This pulse is characterized by the artery swelling and then quickly dropping in diastole (the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood).

Patients might report fainting spells or feeling light-headed due to the imbalance of forward flow through the aortic valve and the significant difference in blood pressure. They may also have reduced exercise capacity and difficulty performing their daily activities. If this is the case, they should be evaluated for this condition.

Testing for Austin Flint Murmur

For patients displaying an Austin Flint murmur, the best test to consider is a transthoracic Doppler echocardiogram. If the images from this echocardiogram are not clear due to the patient’s body shape, a cardiac MRI scan may be needed.

Moreover, medical guidelines by the American College of Cardiology and the American Heart Association advise that in severe but symptom-less aortic regurgitation cases, patients should get a transthoracic echocardiogram every year. However, if patients show left ventricular (the lower left chamber of the heart) dilation, despite showing no symptoms, the testing frequency should be increased.

Treatment Options for Austin Flint Murmur

The treatment for patients with an Austin Flint murmur, a heart murmur associated with aortic regurgitation, or the backward flow of blood into the heart, will be the same whether or not they have this murmur. The first step involves managing high blood pressure with medicines that can reduce the amount of work the heart has to do, like certain calcium channel blockers or drugs that can prevent or slow down a hormone system that can increase blood pressure.

However, the ultimate treatment usually involves replacing the aortic valve. Younger patients who can handle blood thinning therapy are often given artificial heart valves made of metal, as these can last longer than other types of heart valves. For older patients, or those who the use of blood thinning medication is not suitable for, heart valves made from animal tissue, or bioprosthetic valves, are used. These don’t need the same constant use of blood thinners as a metal valve does.

There are some patients who may not be good candidates for surgery, as determined by a risk assessment tool used by heart surgeons. In these cases, a less invasive procedure to implant a new aortic valve might be considered.

When a patient has a heart murmur and a wide difference between their systolic and diastolic blood pressures (pulse pressure), doctors might consider a number of potential causes. These could include conditions which lead to increased blood flow, such as:

Thyrotoxicosis (an overactive thyroid)
Severe anemia (low red blood cell count)
Wet beriberi or Thiamine deficiency (vitamin B1 deficiency)
Arteriovenous fistulae (abnormal connection between arteries and veins)
Pregnancy

Other conditions inside the heart that could cause similar symptoms include:

Infective endocarditis (infection of the inner layer of the heart)
Mitral stenosis (narrowing of the heart’s mitral valve)
Tricuspid stenosis (narrowing of the heart’s tricuspid valve)
Mitral regurgitation (backward flow of blood because the mitral valve doesn’t close tightly)
Pulmonic regurgitation (backflow of blood from the pulmonary artery to the right ventricle)

Furthermore, differentiation between conditions called Austin Flint murmur and mitral stenosis becomes possible thanks to specific characteristics. For instance, the presence of an opening snap in mitral stenosis, or the change in the intensity of the Austin Flint murmur after inhaling amyl nitrate, can help tell these two conditions apart. After inhalation, this murmur becomes less clear because blood pumping from the heart (afterload) decreases, while the mitral stenosis murmur tends to last longer and get louder.

What to expect with Austin Flint Murmur

The outlook for patients with severe aortic regurgitation, that’s also associated with an Austin Flint murmur, depends on several factors. Ten years after being diagnosed, approximately 75% of these patients will either have passed away or needed a valve replacement.

Survival rates are influenced by factors such as age, the severity of the patient’s symptoms, associated health conditions, irregular heart rhythms (atrial fibrillation), and the size of the left ventricular end-systolic diameter when adjusted for body surface area.

Patients with severe dysfunction in the left ventricle, one of the heart’s main pumping chambers, have a 62% survival rate. Comparatively, there’s a much higher 96% survival rate in patients with a preserved left ventricular function.

Possible Complications When Diagnosed with Austin Flint Murmur

Severe chronic aortic regurgitation has serious complications that include the progressive loss of left ventricle function and its enlargement. This can result in symptomatic congestive heart failure, heart attacks, irregular heart rhythms, and even sudden cardiac death. The risk of these complications is higher if the patient is showing symptoms of aortic regurgitation. It is also higher if an echocardiogram – a type of ultrasound of your heart – reveals a low ejection fraction (a measurement of how much blood the left ventricle pumps out with each contraction) and an increased left ventricular end-systolic dimension. This is a measurement of the size of the left ventricle at the end of contraction and its increase indicates a worsening condition. These facts underscore the need to keep a close watch on patients with aortic regurgitation to prevent harmful outcomes.

Common Complications:

Progressive loss of left ventricle function
Enlargement of the left ventricle
Congestive heart failure with symptoms
Heart attacks
Irregular heart rhythms
Sudden cardiac death

Preventing Austin Flint Murmur

In order to ensure the best treatment results for this disease, it’s crucial that patients understand their health condition and follow their doctor’s guidance. This includes taking prescribed medications regularly and getting regular check-ups. By doing so, patients can help slow down the progression of the disease and determine the best timing for any necessary surgery.

Patients should also schedule regular visits with a heart specialist for routine heart scans. This can significantly improve their health conditions in the long run.