AORTIC REGURGITATION AETIOLOGY AND CLINICAL FEATURES
Aetiology
The aortic valve cusps normally overlap on closure to the extent of about 25% of the cusp area. Aortic regurgitationcan arise from:
• Dilatation of the valve ring so that the cusps no longer meet adequately to prevent leakage
• Damage to the cusps themselves
• In some diseases, a combination of these factors.Dilatation of the valve ring occurs classically in syphiliticaortic regurgitation, but can also occur with hypertensionand aortic dissection; less common causes include cysticmedial necrosis in Marfan's syndrome, and osteogenesis imperfecta.Damage to the valve cusps is a feature of rheumaticaortic regurgitation, infective endocarditis, and less common conditions such as Libman-Sacks endocarditis, mucopolysaccharidoses and pseudoxanthoma elasticum. The seronegative arthritides, ankylosing spondylitis,Reiter's disease and psoriatic arthritis can be associatedwith an aortitis and cusp damage, leading to aortic regurgitation.Rarely, rheumatoid arthritis is associated with a nodular cusp damage leading to aortic regurgitation.Bicuspid aortic valve (found in 1% of the population)can lead to predominant aortic regurgitation. There are other congenital forms of aortic regurgitation, e.g. that associated with a supracristal ventricular septal defect.
Clinical features
Symptoms and pathophysiology Aortic regurgitation can be well tolerated for years if it develops slowly. Up to 80% regurgitation can be found in severe chronic aortic regurgitation, but acute regurgitation(such as follows aortic dissection or acute infective endocarditis) is poorly tolerated.The severity of the regurgitation is normally indicated by a low diastolic blood pressure and wide pulse pressure.These may appear more 'normal' in heart failure as the stroke volume falls and the end-diastolic pressure of theleft ventricle rises. As aortic regurgitation progresses,the increasing leakage requires a larger and larger forwardflow. This is usually achieved not by a tachycardia but by the left ventricular end-diastolic size increasing with anincreased stroke volume. Initially, the ejection fraction of the left ventricle is well maintained and exercise tolerance is excellent. However, after an unpredictable time there is a steady or sudden deterioration in left ventricular function, usually with a great increase in heart size and thedevelopment of symptoms of left ventricular failure. Eventually,right heart failure follows, with the development of pulmonary hypertension. The development of heart failure indicates serious dilatation of the left ventricleand the need for urgent consideration of valve surgery.Heart failure in aortic regurgitation is associated withrapidly worsening left ventricular function, which may never recover even with valve replacement. Angina can develop because the dilated left ventriclehas increased oxygen requirements (as in congestive cardiomyopathy),but is usually associated with coronary artery disease. AF occurs in about 15% of cases, usually those with long-standing failure.
Physical signs
The physical signs of aortic regurgitation are related to the large stroke volume, the peripheral vasodilatation and the compensatory increase in size of the left ventricle. The pulse may be collapsing or bisferiens, or feel normal if there is heart failure. The blood pressure indicates the large pulse pressure and low diastolic pressure. If the diastolic pressure is well maintained in the presence of severe aortic regurgitation,coincident hypertension should be suspected. The left ventricle is very active, and in severe cases the apex beatis displaced.The increased forward flow is often accompanied bya systolic flow murmur, which, of itself, does not indicate coincident stenosis. The early diastolic murmur is notoriously difficult to hear. The murmur is best heard with the diaphragm of the stethoscope, with the patient sitting forward having breathed out. It may be best heard at the left sternal edge, nearer the apex or in the aortic area,depending on the direction of the jet. Typically, valve ring dilatation regurgitation is better heard in the third right interspace rather than the third left.An Austin Flint murmur may be associated with aortic regurgitation. This is an apical diastolic murmur, similar tothat of mitral stenosis, arising from the anterior cusp of the mitral valve, which vibrates in the jet of aortic regurgitation.Because aortic regurgitation may be both difficult tohear and is a frequent lesion in infective endocarditis, a patient with a fever and steadily widening pulse pressureis regarded as having aortic regurgitation and endocarditisuntil proved otherwise.
Investigation
ECG shows left ventricular hypertrophy of the diastolicoverload type, in that, initially at least, voltage changes withprominent Q waves over the lateral leads predominateover T-wave changes. Later, the T waves invert.Chest X-ray shows increasing size of the left ventricleand often some dilatation of the proximal aorta.Generalized cardiac enlargement may follow and, eventually,changes of raised pulmonary venous pressure.Echocardiography. M mode shows the dilated left ventricleand its wall thickness. Calculation can be made of thestroke volume and ejection fraction, which are useful forfollowing progress. In many cases vibration of the anteriorcusp of the mitral valve or the septum can be seen, confirmingthe diagnosis. Doppler ultrasound will confirm thediagnosis but cannot quantify the lesion.Cardiac catheterization is necessary to examine left ventricularfunction, the severity of the aortic regurgitationand its anatomy, as well as looking for other pathology,such as mitral regurgitation and coronary artery disease.
Management
Surgery Those in heart failure have been left too late to obtain themaximum benefit from surgery, as a dilated 'myopathic'heart never returns to normal and is associated with ahigh risk of sudden death. The currently used criteria forsurgery are based on echocardiographic dimensions; othersare now being developed based on the use of isotope leftventricular angiography. A fall in the ejection fraction ofthe left ventricle on exercise has been suggested as a criterionfor surgery, as the ejection fraction is normally wellmaintained or even increases. Acute aortic regurgitationrequires very close attention and urgent valve replacementat the first sign of heart failure. Delay can result in catastrophicheart failure and death, as the degree of regurgitation and size of the heart rapidly increase.
The aortic valve cusps normally overlap on closure to the extent of about 25% of the cusp area. Aortic regurgitationcan arise from:
• Dilatation of the valve ring so that the cusps no longer meet adequately to prevent leakage
• Damage to the cusps themselves
• In some diseases, a combination of these factors.Dilatation of the valve ring occurs classically in syphiliticaortic regurgitation, but can also occur with hypertensionand aortic dissection; less common causes include cysticmedial necrosis in Marfan's syndrome, and osteogenesis imperfecta.Damage to the valve cusps is a feature of rheumaticaortic regurgitation, infective endocarditis, and less common conditions such as Libman-Sacks endocarditis, mucopolysaccharidoses and pseudoxanthoma elasticum. The seronegative arthritides, ankylosing spondylitis,Reiter's disease and psoriatic arthritis can be associatedwith an aortitis and cusp damage, leading to aortic regurgitation.Rarely, rheumatoid arthritis is associated with a nodular cusp damage leading to aortic regurgitation.Bicuspid aortic valve (found in 1% of the population)can lead to predominant aortic regurgitation. There are other congenital forms of aortic regurgitation, e.g. that associated with a supracristal ventricular septal defect.
Clinical features
Symptoms and pathophysiology Aortic regurgitation can be well tolerated for years if it develops slowly. Up to 80% regurgitation can be found in severe chronic aortic regurgitation, but acute regurgitation(such as follows aortic dissection or acute infective endocarditis) is poorly tolerated.The severity of the regurgitation is normally indicated by a low diastolic blood pressure and wide pulse pressure.These may appear more 'normal' in heart failure as the stroke volume falls and the end-diastolic pressure of theleft ventricle rises. As aortic regurgitation progresses,the increasing leakage requires a larger and larger forwardflow. This is usually achieved not by a tachycardia but by the left ventricular end-diastolic size increasing with anincreased stroke volume. Initially, the ejection fraction of the left ventricle is well maintained and exercise tolerance is excellent. However, after an unpredictable time there is a steady or sudden deterioration in left ventricular function, usually with a great increase in heart size and thedevelopment of symptoms of left ventricular failure. Eventually,right heart failure follows, with the development of pulmonary hypertension. The development of heart failure indicates serious dilatation of the left ventricleand the need for urgent consideration of valve surgery.Heart failure in aortic regurgitation is associated withrapidly worsening left ventricular function, which may never recover even with valve replacement. Angina can develop because the dilated left ventriclehas increased oxygen requirements (as in congestive cardiomyopathy),but is usually associated with coronary artery disease. AF occurs in about 15% of cases, usually those with long-standing failure.
Physical signs
The physical signs of aortic regurgitation are related to the large stroke volume, the peripheral vasodilatation and the compensatory increase in size of the left ventricle. The pulse may be collapsing or bisferiens, or feel normal if there is heart failure. The blood pressure indicates the large pulse pressure and low diastolic pressure. If the diastolic pressure is well maintained in the presence of severe aortic regurgitation,coincident hypertension should be suspected. The left ventricle is very active, and in severe cases the apex beatis displaced.The increased forward flow is often accompanied bya systolic flow murmur, which, of itself, does not indicate coincident stenosis. The early diastolic murmur is notoriously difficult to hear. The murmur is best heard with the diaphragm of the stethoscope, with the patient sitting forward having breathed out. It may be best heard at the left sternal edge, nearer the apex or in the aortic area,depending on the direction of the jet. Typically, valve ring dilatation regurgitation is better heard in the third right interspace rather than the third left.An Austin Flint murmur may be associated with aortic regurgitation. This is an apical diastolic murmur, similar tothat of mitral stenosis, arising from the anterior cusp of the mitral valve, which vibrates in the jet of aortic regurgitation.Because aortic regurgitation may be both difficult tohear and is a frequent lesion in infective endocarditis, a patient with a fever and steadily widening pulse pressureis regarded as having aortic regurgitation and endocarditisuntil proved otherwise.
Investigation
ECG shows left ventricular hypertrophy of the diastolicoverload type, in that, initially at least, voltage changes withprominent Q waves over the lateral leads predominateover T-wave changes. Later, the T waves invert.Chest X-ray shows increasing size of the left ventricleand often some dilatation of the proximal aorta.Generalized cardiac enlargement may follow and, eventually,changes of raised pulmonary venous pressure.Echocardiography. M mode shows the dilated left ventricleand its wall thickness. Calculation can be made of thestroke volume and ejection fraction, which are useful forfollowing progress. In many cases vibration of the anteriorcusp of the mitral valve or the septum can be seen, confirmingthe diagnosis. Doppler ultrasound will confirm thediagnosis but cannot quantify the lesion.Cardiac catheterization is necessary to examine left ventricularfunction, the severity of the aortic regurgitationand its anatomy, as well as looking for other pathology,such as mitral regurgitation and coronary artery disease.
Management
Surgery Those in heart failure have been left too late to obtain themaximum benefit from surgery, as a dilated 'myopathic'heart never returns to normal and is associated with ahigh risk of sudden death. The currently used criteria forsurgery are based on echocardiographic dimensions; othersare now being developed based on the use of isotope leftventricular angiography. A fall in the ejection fraction ofthe left ventricle on exercise has been suggested as a criterionfor surgery, as the ejection fraction is normally wellmaintained or even increases. Acute aortic regurgitationrequires very close attention and urgent valve replacementat the first sign of heart failure. Delay can result in catastrophicheart failure and death, as the degree of regurgitation and size of the heart rapidly increase.
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