Austin Flint Murmur


Article Author:
Christopher Foth


Article Editor:
Roman Zeltser


Editors In Chief:
William Gossman


Managing Editors:
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Frank Smeeks
Kristina Soman-Faulkner
Benjamin Eovaldi
Radia Jamil
Sobhan Daneshfar
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Hajira Basit
Phillip Hynes


Updated:
12/16/2018 3:59:06 PM

Introduction

American physician Austin Flint first described his namesake murmur in 1862.[1] In his own poetic words: "The murmur is oftener rough than soft. The roughness is often peculiar. It is a blubbering sound, resembling that produced by throwing the lips or the tongue into vibration with the breath of respiration."

The murmur is best described in modern terms as a low-pitched mid to late diastolic rumble heard best at the apex of the heart and is associated with severe aortic regurgitation.

Etiology

An echocardiogram-based study found the Austin Flint murmur was not associated with rapid mitral inflow as others had previously suggested.[2] The authors concluded that the murmur resulted from the regurgitant aortic jet alone.[2] Another study of echocardiogram findings concluded that the sound auscultated resulted from abutment of the aortic regurgitant jet against the left ventricular epicardium.[3] A prior study had suggested that the Austin Flint murmur was caused by a regurgitant aortic jet directed at the anterior mitral leaflet resulting in shuddering of the leaflet.[4] The authors hypothesized that this shuddering resulted in vibrations and shock waves that ultimately distorted the regurgitant aortic jet and caused the familiar sound heard in the Austin Flint murmur. Ultimately, there is no consensus about the cause of the sound auscultated as the Austin Flint murmur.

Epidemiology

The prevalence of the Austin Flint murmur would be expected to correlate to with that of severe aortic regurgitation. In the Framingham study, the incidence of moderate to severe aortic regurgitation was less than 1% in age groups under 70 years old.[5] In the 70 to 83-year-old age group, the incidence was 2.2% for men and 2.3% for women.[5] However, not all patients with severe aortic regurgitation will have an Austin Flint murmur; therefore, the true prevalence of the murmur is currently unknown.

Pathophysiology

In developing countries, the most common cause of aortic regurgitation remains rheumatic heart disease.[6] In developed countries, aortic regurgitation occurs most often in young patients with a bicuspid aortic valve and in an advanced age when the burden of calcific aortic disease is at its greatest.[5]

History and Physical

The Austin Flint murmur is a rumbling diastolic murmur best heard at the apex of the heart that is associated with severe aortic regurgitation and is usually heard best in the fifth intercostal space at the midclavicular line. Younger patients are more likely to have a history of a bicuspid aortic valve or rheumatic heart disease while older patients are more likely to suffer from calcific valvular disease. A blood pressure reading on the patient will show an increased pulse pressure (systolic blood pressure, diastolic blood pressure) due to the backflow of blood through the aortic valve during diastole. You may be able to palpate a "water hammer" pulse which is also known as "Corrigan's pulse." This finding is characterized by arterial swelling followed by a brisk diastolic fall.

Patients may endorse a history of syncope or lightheadedness associated with an inability to maintain forward flow through the aortic valve and the significant difference between systolic and diastolic pressure. Decreasing exercise tolerance and inability to perform activities of daily living should be screened for in all patients.

Evaluation

The most appropriate test to order in a patient with an Austin Flint murmur is a transthoracic Doppler echocardiogram.[7] A cardiac MRI indicates if the echocardiogram images are suboptimal due to body habitus.[7] In severe asymptomatic aortic regurgitation, the AHA/ACC recommend yearly monitoring with a transthoracic echocardiogram.[7] This monitoring interval should be shortened in patients that remain asymptomatic despite LV dilation.

Treatment / Management

Treatment and management of a patient with an Austin Flint murmur are the same as other patients with severe aortic regurgitation regardless of whether an Austin Flint murmur is auscultated. Medical management consists of treating hypertension with afterload reducing agents such as dihydropyridine calcium channel blockers or angiotensin-converting enzyme inhibitors/angiotensin receptor blockers.[7]. Definitive management is with aortic valve replacement.[7] Metallic prosthetic valves are preferred in younger patients who can tolerate anticoagulation due to increased longevity compared to bioprosthetic valves.[7]. Elderly patients and patients with contraindications to anticoagulation should undergo implantation of bioprosthetic valves which do not require the same lifelong anticoagulation therapy as a metallic valve.[7] Patients who are poor surgical candidates, as determined by calculating the society of thoracic surgeons cardiac risk score (STS score), can be evaluated for the implantation of a transcatheter aortic valve replacement.[7]

Differential Diagnosis

The Austin Flint murmur can be differentiated from organic mitral stenosis by the presence of an opening snap in mitral stenosis. Further differentiation can be achieved with amyl nitrate inhalation which will decrease the intensity of the Austin Flint murmur due to a decrease in afterload. The murmur of mitral stenosis will increase in both duration and intensity with amyl nitrate inhalation.

Prognosis

The prognosis of patients with severe aortic regurgitation associated with the Austin Flint murmur depends on a variety of factors. Within 10 years of diagnosis of severe aortic regurgitation, 75% of patients will either pass away or require valve replacement.[8] Predictors of survival include: age, functional class, comorbidities, atrial fibrillation, and left ventricular end-systolic diameter corrected for body surface area.[8] Those with severe left ventricular dysfunction have a survival rate of 62% compared to 96% in patients with preserved left ventricular function.[9]

Consultations

The first consultation for a patient with an Austin Flint murmur should be with a cardiologist. The cardiologist can medically manage the patient while they coordinate care with prompt referral to a cardiothoracic surgeon for evaluation of surgical aortic valve replacement. If the patient is not a candidate for a surgical aortic valve replacement due to an elevated STS score, an interventional cardiologist trained in structural heart disease should be consulted to evaluate the patient for a transcatheter aortic valve replacement.

Enhancing Healthcare Team Outcomes

When you auscultate an Austin Flint murmur in a patient, it correlates with that patient having severe aortic regurgitation. Coordinated care between cardiologist, cardiothoracic surgeon, and interventional cardiologist are integral in managing these complex patients. In patients that are candidates, surgical aortic valve replacement is the gold standard. (Level 1) In patients with prohibitively high STS scores, the option for a transcatheter aortic valve approach should be discussed with the patient. (Level 1)

The recovery time from an aortic valve replacement is 4 to 8 weeks.  The most important factors in recovery are nutrition and exercise.  Nutritional guidance should be provided before discharge, and follow up with a nutritionist after discharge may be beneficial in high-risk patients.  Patients that are elderly or with significant comorbidities benefit from cardiac rehabilitation which has been shown to increase aerobic capacity and quality of life.[10] (Level I)


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Austin Flint Murmur - Questions

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Which namesake murmur is associated with severe aortic regurgitation?



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A 79-year-old female present with worsening shortness of breath and episodes of dizziness that have been progressively worsening for the past two months. The blood pressure on the chart reads as 130/50 mmHg. Her only medication is an aspirin daily. Which physical examination finding is most likely to be found?



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A 78-year-old female with no known past medical history presents with recent a recent syncopal episode. She was gardening at the time, and when she stood up, she immediately passed out. A low pitched rumbling mid-diastolic murmur heard best at the apex. What is the most probable significance of this murmur?



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An echocardiogram shows an eccentric aortic regurgitant jet directed at the anterior mitral valve leaflet resulting in shuddering of the leaflet. Which physical examination finding would be expected?



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A 17-year-old female with a medical history of Turner syndrome visits the cardiologist after being referred by her primary care provider after auscultating an Austin Flint murmur. Which genetic structural heart defect is this patient most likely to have?



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Austin Flint Murmur - References

References

Emi S,Fukuda N,Oki T,Iuchi A,Tabata T,Kiyoshige K,Fujimoto T,Manabe K,Ito S, Genesis of the Austin Flint murmur: relation to mitral inflow and aortic regurgitant flow dynamics. Journal of the American College of Cardiology. 1993 May     [PubMed]
Flint A, Classics in cardiology: on cardiac murmurs(*) (part 3). Heart views : the official journal of the Gulf Heart Association. 2012 Apr     [PubMed]
Landzberg JS,Pflugfelder PW,Cassidy MM,Schiller NB,Higgins CB,Cheitlin MD, Etiology of the Austin Flint murmur. Journal of the American College of Cardiology. 1992 Aug     [PubMed]
Rahko PS, Doppler and echocardiographic characteristics of patients having an Austin Flint murmur. Circulation. 1991 Jun     [PubMed]
Nishimura RA,Otto CM,Bonow RO,Carabello BA,Erwin JP 3rd,Guyton RA,O'Gara PT,Ruiz CE,Skubas NJ,Sorajja P,Sundt TM 3rd,Thomas JD, 2014 AHA/ACC guideline for the management of patients with valvular heart disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Journal of the American College of Cardiology. 2014 Jun 10     [PubMed]
Singh JP,Evans JC,Levy D,Larson MG,Freed LA,Fuller DL,Lehman B,Benjamin EJ, Prevalence and clinical determinants of mitral, tricuspid, and aortic regurgitation (the Framingham Heart Study) The American journal of cardiology. 1999 Mar 15     [PubMed]
Bekeredjian R,Grayburn PA, Valvular heart disease: aortic regurgitation. Circulation. 2005 Jul 5     [PubMed]
Savage PD,Rengo JL,Menzies KE,Ades PA, Cardiac Rehabilitation After Heart Valve Surgery: COMPARISON WITH CORONARY ARTERY BYPASS GRAFT PATIENTS. Journal of cardiopulmonary rehabilitation and prevention. 2015 Jul-Aug     [PubMed]
Bonow RO,Picone AL,McIntosh CL,Jones M,Rosing DR,Maron BJ,Lakatos E,Clark RE,Epstein SE, Survival and functional results after valve replacement for aortic regurgitation from 1976 to 1983: impact of preoperative left ventricular function. Circulation. 1985 Dec     [PubMed]
Dujardin KS,Enriquez-Sarano M,Schaff HV,Bailey KR,Seward JB,Tajik AJ, Mortality and morbidity of aortic regurgitation in clinical practice. A long-term follow-up study. Circulation. 1999 Apr 13     [PubMed]

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