Aortic regurgitation is a common valvular disease that may present chronically or acutely.Normally the integrity of valve closure depends upon the anatomy of valve leaflets and on three dimensional geometry of aortic root and sinuses of Valsalva. Wide variety of causes may lead to aortic regurgitation. Usually 50 per cent of valve replacements are due to diseases of valve and 50 per cent due to root disease. However, in India predominant cause of aortic valve replacement is still rheumatic.
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| Causes of Aortic Regurgitation |
Pathology
In Post Inflammatory situations scarring and retraction of valve cusps lead to aortic regurgitation.Varying degrees of commissural fusion leads to incomplete opening and closing in rheumatic heart disease.15 – 20 per cent of bicuspid valve patients will have significant aortic regurgitation. In Marfan’s Syndrome due to abnormalities in fibrillin and in cystic medial necrosis due to abnormalities in elastin aortic wall becomes weak, stretched out and does not support commissures leading to incomplete central closure. In inflammatory aortitis situations like syphilis and ankylosing spondylitis, medial inflammation and scarring cause root dilatation. In SLE with anti cardiolipin antibodies, Libman-Sacks endocarditis and in rheumatoid arthritis, rheumatoid nodules cause scarring of valve cusps.
Pathophysiology
Left ventricle responds to chronic aortic regurgitation by chamber dilatation and an increase in its compliance so that end diastolic pressure does not increase. This is accompanied by rearrangement of muscle fibers and addition of new sarcomeres leading to eccentric hypertrophy.As the chamber dilates—with preserved systolic function – stroke volume increases compensating the regurgitant volume. However, dilated chamber increases wall stress and afterload and to compensate for the increased afterload concentric hypertrophy ensues. Thus,chronic aortic regurgitation represents combined volume and pressure overload. During this compensatory phase involving preload reserve and concentric and eccentric hypertrophy, patientremains asymptomatic with preserved left ventricular systolic function but with dilated left ventricle. This can go on for many years. Patient becomes symptomatic as the preload reserve gets exhausted and end diastolic pressure increases. Further increase in afterload leads to afterload mismatch and left ventricular systolic function declines. The changes occur very insidiously and patient may remain asymptomative till severe LV dysfunction sets in. As the chamber enlargement proceeds and geometry alters depressed myocardial function occurs and predominates over afterload mismatch.
Though both mitral and aortic regurgitation cause volume overload to left ventricle–aortic regurgitation has additional pressure overload as the increased stroke volume has to be ejected into high impedance aorta. This is also borne out by the increased left ventricular end systolic wall stress. In mitral regurgitation, the initial compensatory mechanism is increased ejection fraction with little ventricular dilatation but in aortic regurgitation it is ventricularmdilatation with preserved ejection fraction.In aortic regurgitation, coronary perfusion is impaired due to decreased aortic diastolic pressure and increased oxygen demands. This in severe cases leads to sub endocardial ischaemia.
Clinical Features
Symptoms
Patients with chronic severe AR may be asymptomatic for many years and it may be picked up on routine examination. Some patients may remain asymptomatic even with severe left ventricular systolic dysfunction. Excertional dyspnoea occurs as the left ventricle end diastolic pressure increases. Impaired coronary blood flow results in angina, sometimes occurring in the nights and awakening the patient from sleep (nocturnal angina). As the systolic dysfunction worsens,patients may have dyspnoea at rest, paroxysmal nocturnal dyspnoea, and even frank heart failure.
Angina is more pronounced in patients with Leutic or Takayasu aortitis with coronary ostial disease. Patients may also complain of palpitation due to forcible ventricular contraction. Rarely sudden death may occur in patients with severe aortic regurgitation.Physical Signs Chronic severe aortic regurgitation is characterized by wide pulse pressure and multiple peripheral signs it produces. Sharp rapid upstroke of radial pulse followed by rapid down stroke is called Corrigan’s pulse or water hammer pulse and is exaggerated by elevating the wrist. Carotids have two prominent systolic impulses called bisferiens pulse. There may be palpable thrill in carotids due to rapid ejection of increased stroke volume.
Due to rapid run off of blood from aorta in diastole and increased stroke volume, varieties of physician signs are described. Movement of head synchronously with arterial pulsation causes head bob. Auscultation over femoral arteries with gentle compression produces to and fro bruit called Duroziez’s sign and it corresponds flow reversal in aorta. The prominent pulse waves may be audible over brachial and other peripheral arteries and are called pistol shot sounds. These interfere with measurement of diastolic blood pressure. In significant aortic regurgitation diastolic blood pressure is usually less than 70 mmHg and systolic blood pressure is elevated causing wide pulse pressure. Normal systolic blood pressure difference between lower and upper limbs of 10–20 mmHg is exaggerated in aortic regurgitation. The difference of more than 60 mmHg suggests severe aortic regurgitation, 40–60 mmHg difference suggest moderate aortic regurgitation and 20–40 mmHg difference mild.
Usually cardiac enlargement is present and left ventricular hyper dynamic apex is palpable outside mid clavicular line. S 1 is normal or slightly reduced in intensity. A 2 is louder in aortic regurgitation due to aortic root disease while it is muffled in valvular aortic regurgitation. Leftventricular S 3 suggest left ventricular dysfunction. Constant ejection click may be audible in bicuspid aortic valve or with root dilatation.
Characteristic murmur is early diastolic murmur which is high pitched and blowing. It is best heard in left parasternal border third left intercostals space at end expiration with patient sitting and bending forward. A cooing or musical murmur suggests everted or perforated cusp (Seagull murmur). A murmur that is better heard on the right side of the sternum suggests aortic root disease. Ejection systolic murmur due to increased systolic flow across aortic valve is common and its presence does not necessarily mean aortic stenosis. Some patients have their cooing early diastolic murmur referred to apex. At apex one may additionally hear Austin Flint (mid diastolic) murmur. This may be due to aortic regurgitation jet pushing the anterior mitral leaflet up and causing relative mitral stenosis or just audibility of low pitched vibrations of aortic regurgitation itself. This needs to be differentiated from associated mitral stenosis.Physical signs of aortic regurgitation are unmistakable, but with cursory and casual examination – one may miss them.
Investigation
Chest X–Ray
Left ventricular dilatation produces cardiomegaly on chest radiograph. Ascending aorta is often prominent. Egg shell calcification of ascending aorta suggests Leutic etiology while widened mediastinum makes one suspect aortic dissection. Valve calcification is better seen on fluoroscopy. With left ventricular failure obvious radiological signs may emerge. Mild or even moderate aortic regurgitation may produce no radiological signs.
Electrocardiogram
Electrocardiogram shows left ventricular dominance with voltage criteria for left ventricular hypertrophy. In moderate aortic regurgitation prominent q-waves are seen in lateral leads with iso-electric ST-segment. As the severity of AR increases and LV dilates, LVH with strain pattern appears with ST-segment depression and T-wave inversion in lateral leads. Conduction blocks may be seen in patients with post inflammatory AR or due to severe calcific aortic valve disease.
Echocardiogram
Echocardiography is done to confirm the diagnosis of aortic regurgitation, evaluate the cause of AR and assess the aortic valve and severity of aortic regurgitation. It is also used to assess the left ventricular size and function.Diastolic flutter of anterior mitral leaflet and premature closure of mitral valve in severe, often acute, aortic regurgitation are noted. Dilated chamber with increased contractility suggesting volume overload pattern of left ventricle is seen. 2 D guided M-mode measurements should be made to record LV dimensions, mass and ejection fraction. It should be noted that dimension measurements can vary due to intra and inter observer variability, interim changes in loading conditions, instrumentation factors and physiological variability. Reliability is increased by comparing with previous recordings. Whenever changes are noted, it is prudent to repeat examination after a shorter interval. On the basis of 2 D Doppler and color flow imaging, severe aortic regurgitation can be differentiated from mild aortic regurgitation by following parameters:
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| Comparision between severe AR and mild AR |
Exercise Testing
It is helpful in assessing functional capacity, symptom status and hemodynamic effects in patients with severe AR with good LV function and equivocal symptoms or when patient leads sedentary life. Exercise ejection fraction, when abnormal may predict, poor long term out come. However,it is not clear if it has any independent additional predictive valve over and above LV size and function. It is not particularly indicated in patients with normal LV systolic function without severe LV dilatation.
Radionuclide ventriculography may be used in place of echocardiography where echo window is not suitable to assess LV size and function satisfactorily or when the echocardiographic data is inconclusive. It is also useful in serial follow up of patients.
It is helpful in assessing functional capacity, symptom status and hemodynamic effects in patients with severe AR with good LV function and equivocal symptoms or when patient leads sedentary life. Exercise ejection fraction, when abnormal may predict, poor long term out come. However,it is not clear if it has any independent additional predictive valve over and above LV size and function. It is not particularly indicated in patients with normal LV systolic function without severe LV dilatation.
Radionuclide ventriculography may be used in place of echocardiography where echo window is not suitable to assess LV size and function satisfactorily or when the echocardiographic data is inconclusive. It is also useful in serial follow up of patients.
Cardiac Catheterization
Often cardiac catheterization is not indicated as reliable information for management decision making can be obtained through non-invasive methods. Before Aortic valve replacement (AVR)patient may have coronary angiography if indicated to rule out coronary artery disease. Similarly,cardiac catheterization or angiography may be done if there is any discrepancy between clinical findings and echocardiographic data. Hemodynamic measurements during exercise are occasionally helpful for determining the effect of aortic regurgitation on left ventricular function.In borderline cases right heart pressures on exercise may clarify the indications for AVR.
Natural History
In asymptomatic patients with normal LV function, the rate of progression to symptoms and/or LV Systolic dysfunction is about 4 per cent per year. Average mortality rate is 0.2 per cent per year. 1.3 per cent patients per year developed LV Systolic dysfunction without symptoms.Systolic dysfunction precedes onset of symptoms about 25 per cent of patients. Serial follow up based only on symptom status evaluation is not reliable and quantitative evaluation of left ventricle is needed. Age, end systolic dimension or volume, end diastolic volume or dimensions are good indicators of onset of LV dysfunction, symptoms and/or death. Patients with end systolic dimension of > 50 mm have a likelihood of death, symptom onset and/or LV dysfunction of about 20 per cent year. In those with end systolic dimension between 40-50 mm the likelihood is about 6 per cent per year and in those with less than 40 mm it is zero. Patients with asymptomatic LV systolic dysfunction develop symptoms within 2-3 years at a rate of about 25 per cent per year. In the presurgical era, data has shown annual mortality rate of > 10 per cent in patient with angina and > 20 per cent in patients with heart failure. Symptomatic patient have poorer prognosis even when they have preserved LV function while mild AR in an elderly hypertensive may not need any serious follow up. Same is not true in an young patient with mild AR due to bicuspid aortic valve or aortic root dilatation.
Management
Vasodilators improve stroke volume, and reduce degree of regurgitation. This results from decrease in systemic vascular resistance and leads to reduction in left ventricular end diastolic volume, after load, wall stress and LV mass. They also preserve LV systolic function.Hydralazine and nefedipine when given at appropriate doses decrease left ventricular size and improve LV function. The dose should be titrated to bring down systolic blood pressure as much as possible without getting side effects. Less consistent results were obtained with ACE inhibitors and increased plasma renin activity is not an issue in these patients. Vasodilators may be given in any patient with severe AR with LV dysfunction and symptoms of heart failure when patient is a poor candidate for surgery. They may also be given to a patient with severe AR and LV dysfunction with or without symptoms to improve hemodynamic profile before surgery. They are also indicated in a patient with severe AR and normal LV function. Here they delay the onset of LV dysfunction, symptom onset and postpone the time for AVR and also improve operative outcomes. In this situation there is no proven role of any other medication. Vasodilators should not be used as a substitute for aortic valve replacement in a patient with severe AR who needs surgery either due to LV dysfunction or symptoms. They are also not indicated in patients with mild AR and normal sized left ventricle with good LV function. Following AVR, ACE inhibitors may be better choice in patients with persistent myocardial systolic dysfunction.
Serial Testing
Serial testing is indicated in asymptomatic patients with severe AR and preserved LV function since LV dysfunction may precede the onset of symptoms. The rationale is to identify those who develop symptoms, LV systolic dysfunction and rapid and progressive increase in LV size, when AVR becomes indicated. Patients with mild AR and normal LV size and systolic function need annual follow up or whenever signs and symptoms of worsening occur. Patients with severe ARand LV dilatation (LVEDD > 60 mm) require follow up once in 6 – 12 months while those with LVEDD > 70 mm or LVESD > 50 mm need more frequent follow up. Also patients with aortic root dilatation need more frequent follow up. Patients with change in effort intolerance should have prompt evaluation. When the symptoms change in equivocal or uncertain, exercise testing may be done. Otherwise it is not indicated. Radio nuclide or MRI may be done when the echo window is sub-optimal and there is discrepancy between clinical and echocardiographic findings.Chest X-ray and ECG may have additional value to echo in some patients.
Surgical Therapy
The recommendation for Aortic valve replacement is only for those patients with Severe AR. If patients with mild AR have LV dilatation, dysfunction and symptoms–other causes need to be evaluated and ruled out. If there is uncertainty about the severity of AR–it needs to confirmed with angiographic or any other modality.
In patients with Severe AR with good LV function and symptoms of NYHA ClassIII–IV or angina Canadian class II or more, surgery is indicated. In patients with NYHA Class II dyspnoea exercise testing is useful. If onset of dyspnoea is recent or patient’s LV size and LV function reach threshold values, i.e., LVEF < 50 per cent or LVEDD about 75 mm or LVESD about 55 mm – surgery is indicated.
Natural History
In asymptomatic patients with normal LV function, the rate of progression to symptoms and/or LV Systolic dysfunction is about 4 per cent per year. Average mortality rate is 0.2 per cent per year. 1.3 per cent patients per year developed LV Systolic dysfunction without symptoms.Systolic dysfunction precedes onset of symptoms about 25 per cent of patients. Serial follow up based only on symptom status evaluation is not reliable and quantitative evaluation of left ventricle is needed. Age, end systolic dimension or volume, end diastolic volume or dimensions are good indicators of onset of LV dysfunction, symptoms and/or death. Patients with end systolic dimension of > 50 mm have a likelihood of death, symptom onset and/or LV dysfunction of about 20 per cent year. In those with end systolic dimension between 40-50 mm the likelihood is about 6 per cent per year and in those with less than 40 mm it is zero. Patients with asymptomatic LV systolic dysfunction develop symptoms within 2-3 years at a rate of about 25 per cent per year. In the presurgical era, data has shown annual mortality rate of > 10 per cent in patient with angina and > 20 per cent in patients with heart failure. Symptomatic patient have poorer prognosis even when they have preserved LV function while mild AR in an elderly hypertensive may not need any serious follow up. Same is not true in an young patient with mild AR due to bicuspid aortic valve or aortic root dilatation.
Management
Vasodilators improve stroke volume, and reduce degree of regurgitation. This results from decrease in systemic vascular resistance and leads to reduction in left ventricular end diastolic volume, after load, wall stress and LV mass. They also preserve LV systolic function.Hydralazine and nefedipine when given at appropriate doses decrease left ventricular size and improve LV function. The dose should be titrated to bring down systolic blood pressure as much as possible without getting side effects. Less consistent results were obtained with ACE inhibitors and increased plasma renin activity is not an issue in these patients. Vasodilators may be given in any patient with severe AR with LV dysfunction and symptoms of heart failure when patient is a poor candidate for surgery. They may also be given to a patient with severe AR and LV dysfunction with or without symptoms to improve hemodynamic profile before surgery. They are also indicated in a patient with severe AR and normal LV function. Here they delay the onset of LV dysfunction, symptom onset and postpone the time for AVR and also improve operative outcomes. In this situation there is no proven role of any other medication. Vasodilators should not be used as a substitute for aortic valve replacement in a patient with severe AR who needs surgery either due to LV dysfunction or symptoms. They are also not indicated in patients with mild AR and normal sized left ventricle with good LV function. Following AVR, ACE inhibitors may be better choice in patients with persistent myocardial systolic dysfunction.
Serial Testing
Serial testing is indicated in asymptomatic patients with severe AR and preserved LV function since LV dysfunction may precede the onset of symptoms. The rationale is to identify those who develop symptoms, LV systolic dysfunction and rapid and progressive increase in LV size, when AVR becomes indicated. Patients with mild AR and normal LV size and systolic function need annual follow up or whenever signs and symptoms of worsening occur. Patients with severe ARand LV dilatation (LVEDD > 60 mm) require follow up once in 6 – 12 months while those with LVEDD > 70 mm or LVESD > 50 mm need more frequent follow up. Also patients with aortic root dilatation need more frequent follow up. Patients with change in effort intolerance should have prompt evaluation. When the symptoms change in equivocal or uncertain, exercise testing may be done. Otherwise it is not indicated. Radio nuclide or MRI may be done when the echo window is sub-optimal and there is discrepancy between clinical and echocardiographic findings.Chest X-ray and ECG may have additional value to echo in some patients.
Surgical Therapy
The recommendation for Aortic valve replacement is only for those patients with Severe AR. If patients with mild AR have LV dilatation, dysfunction and symptoms–other causes need to be evaluated and ruled out. If there is uncertainty about the severity of AR–it needs to confirmed with angiographic or any other modality.
In patients with Severe AR with good LV function and symptoms of NYHA ClassIII–IV or angina Canadian class II or more, surgery is indicated. In patients with NYHA Class II dyspnoea exercise testing is useful. If onset of dyspnoea is recent or patient’s LV size and LV function reach threshold values, i.e., LVEF < 50 per cent or LVEDD about 75 mm or LVESD about 55 mm – surgery is indicated.
AVR is indicated in all symptomatic patients NYHA Class II, III, IV and systolic dysfunction with EF 25 – 49 per cent. In patients with EF < 25 per cent and LVESD more than 60 mm surgery carries high risk. LV dysfunction may be irreversible and post operative morbidity is high. Patients with LV dysfunction do well if the duration of LV dysfunction is short or show improvement with intense vasodilatation, inotropic or diuretic therapy. Clinical judgement should be based on the fact that medical management alone carries very high mortality.
In patients with severe AR and no symptoms, LVEF < 50 per cent, LVEDD > 75 mm or LVESD > 55 mm are indications for surgery. Two consecutive measurements may be obtained in short duration before proceeding with surgery or findings may be confirmed in these asymptomatic patients, by 2 different modalities. AVR is also indicated in patients approaching these LV dimension if they have progressive increase in LV size or any evidence of decreasing exercise tolerance. These dimensions should be tailored to patient’s body size but no guidelines are available. Patients with concomitant CAD, Hypertension or other valve disease are also likely to be more symptomatic even with smaller LV size.
Indications for surgery should not be based on the operative techniques used. When aortic root dilatation is equal to or more than 50 mm root reconstruction should accompany aortic valve replacement.Severity of pre-operative symptoms or reduced exercise tolerance, severity of left ventricular systolic dysfunction and duration of LV dysfunction–all predict post-operative survival and recovery of LV systolic function.
Acute Aortic Regurgitation
Infective endocarditis, aortic dissection and trauma often produce severe AR. Acute increase in left ventricular end diastolic volume especially in a small pressure loaded hypertrophied heart increases left ventricular diastolic pressure and causes pulmonary edema. In the absence of compensatory mechanisms forward stroke volume is markedly decreased and patient develops cardiogenic shock. Tachycardia ensues and pulse pressure is low due to low cardiac output. In such a sick patient physical findings are difficult to appreciate. First sound is muffled. Early diastolic murmur is short and soft. Apical diastolic rumble may be present. There are noperipheral signs of chronic severe AR. Physical examination and Chest X–ray do not show any cardiomegaly.
Echocardiogram clinches the diagnosis. Severity and mechanism of AR and associated lesions will be known. Typically acute Severe AR causes short pressure half time of aortic regurgitant jet < 300 m sec., short deceleration time of early mitral filling wave < 150 m sec. and premature closure of mitral valve.
Acute severe AR is a surgical emergency. Pre-operatively patient may be stabilized with inotropes and vasodilatation like nitroprusside. IABP and beta blockers are contraindicated.Disease as well as treatment is associated with high mortality.
In patients with severe AR and no symptoms, LVEF < 50 per cent, LVEDD > 75 mm or LVESD > 55 mm are indications for surgery. Two consecutive measurements may be obtained in short duration before proceeding with surgery or findings may be confirmed in these asymptomatic patients, by 2 different modalities. AVR is also indicated in patients approaching these LV dimension if they have progressive increase in LV size or any evidence of decreasing exercise tolerance. These dimensions should be tailored to patient’s body size but no guidelines are available. Patients with concomitant CAD, Hypertension or other valve disease are also likely to be more symptomatic even with smaller LV size.
Indications for surgery should not be based on the operative techniques used. When aortic root dilatation is equal to or more than 50 mm root reconstruction should accompany aortic valve replacement.Severity of pre-operative symptoms or reduced exercise tolerance, severity of left ventricular systolic dysfunction and duration of LV dysfunction–all predict post-operative survival and recovery of LV systolic function.
Acute Aortic Regurgitation
Infective endocarditis, aortic dissection and trauma often produce severe AR. Acute increase in left ventricular end diastolic volume especially in a small pressure loaded hypertrophied heart increases left ventricular diastolic pressure and causes pulmonary edema. In the absence of compensatory mechanisms forward stroke volume is markedly decreased and patient develops cardiogenic shock. Tachycardia ensues and pulse pressure is low due to low cardiac output. In such a sick patient physical findings are difficult to appreciate. First sound is muffled. Early diastolic murmur is short and soft. Apical diastolic rumble may be present. There are noperipheral signs of chronic severe AR. Physical examination and Chest X–ray do not show any cardiomegaly.
Echocardiogram clinches the diagnosis. Severity and mechanism of AR and associated lesions will be known. Typically acute Severe AR causes short pressure half time of aortic regurgitant jet < 300 m sec., short deceleration time of early mitral filling wave < 150 m sec. and premature closure of mitral valve.
Acute severe AR is a surgical emergency. Pre-operatively patient may be stabilized with inotropes and vasodilatation like nitroprusside. IABP and beta blockers are contraindicated.Disease as well as treatment is associated with high mortality.
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