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In: Perspectives in Aortic Valve Disease ISBN: 978-1-53618-769-4
A2
aortic component of the second heart sound
AF
atrial fibrillation
AR
aortic regurgitation
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Editor: Giovanni Concistrè © 2020 Nova Science Publishers, Inc.
Chapter 2
EPIDEMIOLOGY AND CLINICAL APPROACH
TO AORTIC VALVE DISEASE
Claudio Passino
Filippo Quattrone1, Octavian Vatavu1 and Alberto Aimo1
1
Institute of Life Sciences, Scuola Superiore Sant’Anna, Pisa, Italy
Aortic valve disease is an important cause of morbidity worldwide. Rheumatic heart
disease is the most common cause of both aortic stenosis (AS) and aortic regurgitation
(AR) in developing countries, while fibro-calcific degeneration and conditions causing
aortic root dilation are the leading causes of AS and AR, respectively, in industrialized
countries. A careful search for signs and symptoms may provide the first clues to the
presence of aortic valve disease, which can then be verified and characterized by imaging
techniques, starting from transthoracic echocardiography. In patients with known severe
aortic valve disease, prompt detection of symptom onset is crucial to refer them to aortic
valve replacement (AVR) or transcatether aortic valve implantation (in AS) or AVR (in
AR). Furthermore, a correct interpretation of the signs and symptoms of acute AR can
result in a rapid diagnostic workup and prompt patient referral to surgery
Keywords: epidemiology, aortic valve disease, aortic valve replacement, transcatheter aortic
valve
1,2,*
, Valentina Galfo1, Simone Gasparini1,
2
Fondazione G. Monasterio, Pisa, Italy
ABSTRACT
ABBREVIATIONS
*
Corresponding Author’s Email: passino@ftgm.it.
Claudio Passino, Valentina Galfo, Simone Gasparini et al.
18
AS
aortic stenosis
AVR
aortic valve replacement
BNP
B-type natriuretic peptide
CAD
coronary artery disease
CMR
cardiovascular magnetic resonance
CT
computed tomography
ECG
electrocardiogram
HF
heart failure
HR
hazard ratio
LV
left ventricle
LVEF
LV ejection fraction
MDCT
multidetector computed tomography
NT-proBNP
N-terminal fraction of pro-BNP
P2
pulmonic component of the second heart sound
PET
positron emission tomography
S1
first heart sound
S2
second heart sound
S3
third heart sound
S4
fourth heart sound
SCD
sudden cardiac death
TAVI
transcatheter aortic valve implantation
TEE
transesophageal echocardiogram
TTE
transthoracic echocardiogram
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INTRODUCTION
Stenosis of the aortic valve is the most common cause of left ventricular (LV) outflow
obstruction in children and adults. The three main manifestations of severe aortic stenosis
(AS) are angina, syncope or heart failure (HF). Symptomatic AS has a poor prognosis and
requires surgical or percutaneous treatment. The acute onset of severe aortic regurgitation
(AR) is usually a medical emergency due to the inability of the LV to quickly adapt to the
abrupt increase in end-diastolic volume caused by the regurgitant flow. If not surgically
corrected, acute severe AR commonly results in cardiogenic shock. By contrast, clinical
symptoms are a relatively late feature of chronic AR, since the gradually dilating LV and the
chronically increased diastolic volume dampens many of the hemodynamic effects of AR.
EPIDEMIOLOGY AND ETIOLOGIES
There are 3 main causes of valvular aortic stenosis (AS):
a congenitally abnormal valve, often with superimposed calcification (unicuspid or
bicuspid);
calcific disease of a trileaflet valve (degenerative aortic valve disease);
Epidemiology and Clinical Approach to Aortic Valve Disease
19
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rheumatic valve disease, which is characterized by fusion of commissures between
the leaflets, leaving a small central orifice. The rheumatic process typically involves
the mitral valve as well; as a result, most patients with rheumatic AS also have mitral
stenosis and/or mitral regurgitation.
Rare causes of AS include metabolic disorders (e.g., Fabry’s disease), systemic lupus
erythematosus and alkaptonuria. In patients with Paget disease or end-stage kidney disease,
calcific AS presents at a younger age and progresses more rapidly [1, 2]. Different causes of
AS have different relative frequencies according to geographical regions. Worldwide,
rheumatic valve disease is the most common cause of aortic valve disease and mitral valve
involvement is almost always present. In North America and Europe, aortic valve disease is
primarily due to calcific disease of a native trileaflet valve or a congenitally bicuspid valve [1,
2]. The prevalence of AS increases with age, as demonstrated by a prospective populationbased study of 3,273 participants including 164 subjects with AS. The prevalence of AS
varied from 0.2% at ages 50 to 59 years, to 1.3% at ages 60 to 69, 3.9% at ages 70 to 79
years, and 9.8% at ages 80 to 89 years [3]. Compared with the general population, mortality
was not significantly increased in the group with asymptomatic AS (hazard ratio [HR] 1.28),
nor in those who received aortic valve replacement (AVR) (HR 0.93) [3]. The relative
prevalence of trileaflet versus congenitally abnormal valves varies according to age, as
illustrated by a series of 932 adults who underwent surgery for isolated AS [4]. Patients
undergoing mitral valve replacement or with mitral stenosis were excluded to ensure
exclusion of rheumatic valve disease. An anatomically abnormal valve was present in 54%:
49% had a bicuspid valve and 4% had a unicuspid valve, but the frequency displayed a
significant variation with age:
approximately two-thirds of 7% of patients who underwent surgery at ≤50 years of
age had a bicuspid valve and one-third had a unicuspid valve;
approximately two-thirds of 40% of patients who underwent surgery between 50 and
70 years had a bicuspid valve and one-third a tricuspid valve; only few patients had a
unicuspid valve;
approximately 60% of patients over 70 years had a tricuspid valve and 40% had a
bicuspid valve [4].
The possible causes of acute AR with a native aortic valve include:
infective endocarditis, because of valve destruction and leaflet perforation, or the
rupture of a perivalvular abscess into the LV [5, 6];
aortic dissection, which can lead to AR by four mechanisms: dilation of the sinuses
with incomplete coaptation of the leaflets at the center of the valve; involvement of a
valve commissure resulting in inadequate leaflet support; direct extension of the
dissection into the base of a leaflet, resulting in a flail valve leaflet; and prolapse of
the dissection flap across the aortic valve into the LV outflow tract in diastole
impeding leaflet closure [5, 6];
rupture of a congenitally fenestrated cusp [7-9];
Claudio Passino, Valentina Galfo, Simone Gasparini et al.
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Valve disease
Aortic root dilatation
Degenerative aortic valve disease
Hypertension
Myxomatous degeneration
Congenital heart disease
Bicuspid aortic valve
Ventricular septal defect (infundibular or membranous)
Congenital heart disease
Bicuspid aortic valve
Sinus of Valsalva aneurysm
Genetic syndromes
Pseudoxanthoma elasticum
Genetic syndromes
Marfan syndrome
Familial thoracic aneurysm
Ehlers-Danlos syndrome
Osteogenesis imperfecta
Systemic rheumatic disorders
Ankylosing spondylitis
Rheumatoid arthritis
Systemic lupus erythematosus
Antiphospholipid syndrome
Systemic rheumatic disorders
Giant cell arteritis
Takayasu arteritis
Ankylosing spondylitis
Infective endocarditis
Infectious aortitis (e.g., syphilis)
Aortic dissection
Aortic dissection
Trauma
Trauma
Rheumatic heart disease
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traumatic rupture of valve leaflets after a chest trauma [10, 11];
complications of percutaneous procedures on the aortic valve [12, 13].
In a single-center series of 268 adults referred for AVR for isolated AR, 18% had acute
AR. All of the cases were due to active infective endocarditis (56%) or acute aortic dissection
(44%) [14]. Acute AR may also develop in patients with prosthetic aortic valves. AR may
occur with structural valve deterioration or leaflet destruction due to infective endocarditis.
Acute mechanical valve regurgitation can be caused by valve thrombosis or pannus formation
with incomplete leaflet closure. Paravalvular AR is caused by prosthetic valve dehiscence
occurring as a complication of infective endocarditis or inadequate valve attachment, as in the
case of aortopathy associated with Marfan syndrome [15]. As for chronic AR, a study from
the Framingham Heart Study found that AR of at least trace severity on color Doppler
echocardiography was present in 13% of men and 9% of women. The prevalence of AR
varied with age and disease severity. More than trace AR was unusual before 50 years and
then increased progressively. For mild AR, the prevalence was 3.7, 12.1, and 12.2% in men at
ages 50 to 59, 60 to 69, and 70 to 83, respectively. The corresponding values in women were
1.9, 6.0, and 14.6%. For moderate to severe AR, the prevalence was 0.5, 0.6, and 2.2% in
men at ages 50 to 59, 60 to 69, and 70 to 83, respectively, and 0.2, 0.8, and 2.3% in women
[16]. Chronic AR is caused by diseased valve leaflets or enlargement of the aortic root. In the
developing world, the most common cause of AR is rheumatic heart disease. However, in
developed countries, AR is most often due to aortic root dilation, congenital bicuspid aortic
valve, and degenerative aortic valve disease (Table 1).
Table 1. Causes of chronic aortic regurgitation
Epidemiology and Clinical Approach to Aortic Valve Disease
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CLINICAL APPROACH TO AORTIC VALVE DISEASE
Aortic Stenosis
Symptoms
The “classic” manifestations of AS are angina pectoris, syncope, and HF, but the
following symptoms are currently those most frequently encountered thanks to an earlier
diagnosis:
exertional dyspnea or decreased exercise tolerance,
presyncope or syncope during exercise,
angina pectoris [1, 17].
Patients with AS are typically asymptomatic for a long period despite the increased
pressure load on the LV [3, 46]. A wide variability exists in the degree of outflow obstruction
that causes symptoms, depending in part on patient size and level of physical activity.
However, in most patients with AS and normal LV systolic function, symptoms uncommonly
occur until stenosis is severe (defined as a valve area ≤1.0 cm2, an aortic velocity of 4.0 m/s
or higher, and/or a mean transvalvular gradient ≥40 mmHg) [18]. Notably, many patients who
meet the criteria for severe AS are still asymptomatic. The most common symptom of AS is
dyspnea during exercise, usually due to the diastolic dysfunction with a backward increase in
pulmonary pressures with exercise and an inability of the LV to increase the cardiac output
during exercise. Systolic LV dysfunction develops in a later stage. Once overt HF occurs, the
patient may complain of shortness of breath, fatigue, debilitation, and other signs and
symptoms of a low cardiac output state [17]. Presyncope or syncope is the presenting
symptom in around 10% of patients with symptomatic severe AS [19]. Several mechanisms
may lead to syncope: exercise-induced vasodilation in the presence of an obstruction with
fixed cardiac output can result in hypotension, a transient bradyarrhythmia during or
immediately after exercise, abnormalities in the baroreceptor response with a resulting failure
to appropriately increase the blood pressure, or arrhythmias such as atrial fibrillation (AF)
[17]. Approximately 50% of patients with angina pectoris have concomitant coronary artery
disease (CAD) [20-22]. AS without significant CAD can cause myocardial ischemia by
several mechanisms: increased total LV oxygen demand as a result of increased LV mass;
reduced coronary flow reserve related to myocardial and vascular factors; elevated LV
diastolic pressure contributes to a reduction in the perfusion pressure gradient, especially in
the subendocardial myocardium; reduced diastolic coronary perfusion time during
tachycardia [23].
Signs
The physical examination may provide the first clue to the presence of AS [24]. The three
findings most useful to diagnose severe AS are: a low volume and slow-rising carotid pulse; a
loud mid- or late-peaking systolic murmur in the right intercostal space; a single second heart
sound [24]. On the other hand, these findings can be absent due to concurrent vascular disease
[24-26]. The most useful signs to rule out significant AS are the absence of any systolic
murmur and normal physiologic splitting of the second heart sound (S2). A transthoracic
Claudio Passino, Valentina Galfo, Simone Gasparini et al.
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echocardiogram (TTE) is recommended when AS cannot be excluded on physical
examination in a patient with symptoms possibly due to AS [17]. The typical arterial pulse in
severe AS has been described as “parvus and tardus” (i.e., with a low volume and slowly
rising). It can be appreciated in the carotid artery, and the delay can be detected by
simultaneous palpation of the apex (point of maximum impulse) and the carotid artery. The
amplitude of the carotid upstroke may be preserved in older patients with AS due to vascular
changes. An associated carotid artery thrill or coarse vibration due to the turbulence of blood
flow across the stenotic valve can be sometimes remarked [27]. Stenosis of the aortic leaflets
is associated with reduced mobility and delayed closure [46]. S2 is soft and single since the
aortic component of the second heart sound (A2), which is due to aortic valve closure, is
delayed and tends to occur simultaneously with the pulmonic component of the second heart
sound (P2), due to pulmonary valve closure. S2 may be paradoxically split when the stenosis
is severe and associated with LV dysfunction. With increasingly severe, fixed AS, the A2
closing sound may disappear. The first heart sound (S1) is usually normal. However, an aortic
ejection click, which is more common in patients with a bicuspid aortic valve, may be heard
after S1 when the leaflets are still compliant and mobile. Vigorous left atrial contraction
against a stiff, noncompliant ventricle can produce a fourth heart sound (S4) [17, 27]. The
murmur associated with AS is described as a systolic “ejection” murmur, typically heard best
at the base of the heart in the right intercostal space. The murmur generally begins after S1
and ends before S2. The intensity of the murmur reflects the amount and velocity of blood
flow across the valve and the turbulence produced by the stenosis. A loud murmur has a high
specificity for severe AS. However, most patients with severe stenosis have a grade 3
murmur, and many have only a grade 1 or 2 murmur. In patients with concomitant AS and
LV dysfunction resulting in low-flow low-gradient, the murmur may be soft and almost
inaudible. The timing of the murmur also correlates with AS severity. An early-peaking
murmur is typical of mild to moderate AS, while a late-peaking murmur is consistent with
severe AS. The murmur is well transmitted to carotid arteries and may also radiate to the apex
(Gallavardin phenomenon); the murmur at the apex can be louder when there is an associated
mitral regurgitation [27]. AS is often associated with a small degree of AR since the stiff,
calcified, and rigid aortic valve leaflets may not coapt normally. In this case, a soft diastolic
murmur may be heard [27].
Diagnosis and Evaluation
A TTE is the primary test for the diagnosis and characterization of AS. The exam
includes evaluation of valve anatomy and structure, hemodynamic consequences,
concomitant AR or other valve disorders. In patients with AS, the aortic leaflets are generally
thickened and calcified with reduced systolic motion and a small orifice during systole. Thin
aortic leaflets with normal systolic excursion, a normal aortic root, and normal LV wall
thickness and systolic function suggest absence of significant AS. Patients with LV systolic
dysfunction may have reduced leaflet excursion, even when AS is not severe. When a
bicuspid aortic valve is present, systolic images show the two leaflets (and two commissures)
of the open valve. A bicuspid valve may appear trileaflet when a raphe is present. In patients
with a bicuspid aortic valve, the risk of associated aortic root involvement may be related to
the specific bicuspid valve phenotype (congenital fusion of the right and left versus the right
and noncoronary cusps) [28]. Doppler echocardiography allows measurement of transaortic
velocity and calculation of the LV-aorta gradient and the valve area, which are the standard
Epidemiology and Clinical Approach to Aortic Valve Disease
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parameters used to evaluate stenosis severity. Over 80% of patients with AS display also AR,
which is usually mild. The LV has usually normal size and systolic function, but the LV wall
is concentrically hypertrophied, and LV longitudinal strain is reduced. Mitral regurgitation is
common and may be exacerbated by the high systolic LV pressure due to LV outflow
obstruction. The most reliable measure of AS severity is aortic velocity (or gradient) alone
when LV ejection fraction (LVEF) is normal [27]. Valve area measurements are generally
important only in patients with a low forward stroke volume due to a low LVEF or a small
LV size. Body size should be considered in assessing aortic valve area (AVA) in smaller
patients because a small aortic valve area may be normal for body size in smaller individuals
[28]. A transesophageal echocardiogram (TEE) may be helpful in selected cases as it provides
better images of aortic valve anatomy, and is more accurate for the diagnosis of a sub- or
supra-aortic membrane. An electrocardiogram (ECG) is not needed for AS diagnosis, but is
generally performed as part of the initial evaluation. A chest radiograph is not generally
required when evaluating AS, but can aid in the differential diagnosis of dyspnea [27].
Exercise testing is suggested in patients with asymptomatic severe AS (maximum aortic valve
velocity of ≥4.0 m/s or mean aortic valve pressure gradient ≥40 mmHg) who are sedentary to
confirm asymptomatic status. Such evaluation is particularly helpful when the level of
physical activity is unclear or low. Patients with severe AS who develop typical symptoms of
AS during exercise testing should be considered symptomatic even if the clinical history is
uncertain [18]. Exercise testing should not be performed in patients with symptomatic severe
AS [27]. For patients with equivocal symptoms and severe AS, measurement of B-type
natriuretic peptide (BNP) or N-terminal fraction of pro-BNP (NT-proBNP) levels may be
helpful, as their elevation suggests that symptoms may be due to AS or other causes of high
cardiac filling pressures [27]. Among patients with severe AS, BNP and NT-proBNP are
higher in symptomatic than in asymptomatic patients [29, 30] and fall after AVR [31]. Higher
BNP values are independent predictors of reduced symptom-free survival [32] and overall
survival [33]. Among patients with low gradient AS, low-dose dobutamine stress TTE allows
to differentiate true severe AS (with a fixed small valve area) from pseudo-severe AS (with a
functionally small valve area due to reduced driving forces). Low-dose dobutamine stress test
may also be helpful in symptomatic patients with findings consistent with paradoxical
low-flow low-gradient AS. In addition, the test provides information on LV contractile
reserve, which is helpful for prognostic purposes in contemplating possible surgical AVR or
transcatheter aortic valve implantation (TAVI) [17, 27]. Cardiac computed tomography (CT)
implements the evaluation in patients with low-gradient AS, particularly patients with
classical low-flow low-gradient AS with inconclusive low-dose dobutamine stress TTE, with
symptomatic paradoxical low-flow low-gradient AS who have inconclusive low-dose
dobutamine stress TTE, or symptomatic patients with normal flow, low gradient AS. The
degree of aortic valve calcification correlates with both echocardiographic determination of
stenosis severity and clinical outcomes. Different cutoff values of aortic valve calcium score
should be used in women compared with men to identify severe AS (≥1200 vs. 2000) [34].
Multidetector CT (MDCT) also allows measurement of aortic valve calcium density (the ratio
of calcium load to cross-sectional area of the aortic annulus), which might be useful in the
identification of patients at risk of rapid progression and adverse clinical outcomes [35, 36].
Cardiovascular magnetic resonance (CMR) is not performed routinely for clinical evaluation
of AS, but it provides accurate measurements of the size and shape of the aortic sinuses and
ascending aorta [37, 38], as well as antegrade velocity through the stenotic valve without
Claudio Passino, Valentina Galfo, Simone Gasparini et al.
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Stage
AS
AR
A
Asymptomatic.
V
max
< 2 m/s; bicuspid aortic valve or other
congenital anomalies, aortic sclerosis.
Asymptomatic
At risk of AR, bicuspid aortic valve or other
congenital valve anomaly, aortic valve sclerosis,
diseases of the aortic sinuses or ascending aorta,
history of RHD or IE.
B
Asymptomatic
Mild: V
max
2.0 to 2.9 m/s or mean transvalvular
pressure gradient < 20 mmHg;
Moderate: V
max
3.0-3.9 m/s or mean transvalvular
pressure gradient 20-39 mmHg
Asymptomatic
Progressive AR; mild or moderate AR with
normal LV systolic function and normal or mildly
dilated LV volumes.
C
Asymptomatic.
Severe leaflet calcification/thickening, reduced
leaflet motion and Vmax ≥ 4 m/s; AVA ≤ 1.0 cm2
(or AVA indexed ≤ 0.6 cm2/m2).
Asymptomatic.
Alterations identified by Doppler
echocardiography, CMR or cardiac
catheterization.
C1
LVEF > 50%
LVEF ≥ 50%, LVESD ≤ 50 mm. Compensated
phase of chronic AR.
C2
LVEF < 50%.
Precedes HF.
LVEF < 50% and/or LVESD > 50mm or indexed
LVESD > 25 mm/m2.
D Symptomatic
LVEF 40-50% or < 40%.
D1
Symptomatic
Vmax ≥ 4 m/s or mean transvalvular pressure
gradient is ≥ 40 mmHg. AVA ≤ 1.0 cm2 (or AVA
indexed to body surface area is ≤ 0.6 cm2/m2) but
may be larger with mixed AS/AR.
D2
Symptomatic
LFLG AS with LVEF < 50%. AVA ≤ 1.0 cm2 and
Vmax < 4 m/s or mean pressure gradient < 40
mmHg. AVA ≤ 1.0 cm2 and Vmax ≥ 4 m/s at low-
dose dobutamine stress echocardiography.
D3
Symptomatic
Severe low-gradient AS with LVEF ≥ 50%
(paradoxical low-gradient severe AS). AVA ≤ 1.0
cm2 (or AVA indexed ≤ 0.6 cm2/m2) and Vmax < 4
m/s or mean transvalvular pressure gradient < 40
mmHg; SVi < 35 mL/m2.
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angle dependence [39], and 4D flow patterns. Cardiac catheterization is not routinely required
to assess the aortic valve gradient but is indicated for patients with suspected significant AS
when noninvasive data are nondiagnostic or if there is a discrepancy between the clinical
evaluation and noninvasive testing [18]. Coronary angiography is recommended in patients
with apparently mild to moderate AS who have one or more of the general indications for
coronary angiography such as progressive angina, objective evidence of ischemia, or either
asymptomatic or symptomatic LV dysfunction. Coronary angiography is also mandatory in
patients referred to AVR or transcatheter aortic valve implantation. Noninvasive stress
imaging tests have low sensitivity and specificity for ischemia in patients with AS [17, 27].
Table 2. Stages of aortic stenosis (AS) and aortic regurgitation (AR)
AR, aortic regurgitation; AVA, aortic valve area; AVD, aortic valve degeneration; CMR, cardiovascular magnetic
resonance; HF, heart failure; IE, infective endocarditis; LFLG, low flow, low gradient; LV, left ventricle; LVEF, LV
ejection fraction; LVESD, LV end-systolic dimension; RHD, rheumatic heart disease; SVi, stroke volume index;
Vmax, maximum transvalvular velocity. Adapted from American Heart Association/American College of Cardiology
Guidelines [18].
Epidemiology and Clinical Approach to Aortic Valve Disease
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AS is a progressive disease and 4 stages have been identified based on TTE findings and
symptoms (Table 2). Asymptomatic patients with AS with normal LVEF should be evaluated
serially by history, physical examination and TTE to search for evidence of progression.
Exercise testing is recommended if exercise tolerance is uncertain. The frequency of
recommended evaluation varies with the severity of disease:
for patients with mild AS and no significant calcification, evaluation is recommended
every 2 to 3 years;
for patients with moderate AS, evaluation should be performed every 1 to 2 years;
for patients with asymptomatic severe AS, clinical evaluation should be performed
every 6 to 12 months or sooner if symptoms develop or if there is a change in
physical exam suggestive of worsening AS [18, 34].
Clinical Features of Advanced AS
Diastolic dysfunction, secondary to hypertrophy and fibrosis, is common and often
persists after AVR. These patients may present with HF with preserved ejection fraction. A
subset of patients presents with LV systolic dysfunction due to the high afterload imposed by
the stenotic valve resulting in a low LVEF and symptoms of HF with reduced ejection
fraction. LV dysfunction due to valve obstruction improves rapidly after AVR. The
pulmonary artery pressure may be increased in AS because of the chronic elevation in LV
diastolic filling pressure. A severe elevation in pulmonary artery pressure (systolic pressure
>50 mmHg) occurs in approximately 15% of patients [40]. In some cases, pulmonary
hypertension is due to coexisting lung disease rather than to the effects of aortic valve
obstruction. Symptomatic severe AS is associated with a high risk of sudden cardiac death
(SCD). The incidence of SCD is around 1% per year in patients with asymptomatic severe
AS, and 8 to 34% in symptomatic patients [41]. The mechanism of SCD has not been
established. A potential cause is activation of ventricular baro-chemoreceptors resulting in
paradoxical bradycardia, decreased contractility, and hypotension (Bezold-Jarisch reflex).
Ventricular tachyarrhythmias are another possible cause. The risk of SCD is reduced by AVR
or TAVI [17, 27]. Intraventricular or atrioventricular conduction abnormalities are uncommon
and, when present, may be due to severe hypertrophy, extension of calcium from valve
structures into the interventricular septum, or concomitant heart disease [17]. Ventricular and
supraventricular arrhythmias usually occur in patients with LV dysfunction. Risk factors for
AF include older age, more severe AS, LV hypertrophy and systolic dysfunction [42, 43].
Among adults with mild to moderate AS, AF occurs in 5-6%, with an incidence of 1.2% new
cases per year, and highest when LV systolic dysfunction is present [43]. AF is common in
adults with severe AS (for example, in 34% in a series of patients referred to TAVI) [44].
New-onset AF can precipitate symptom onset in adults with severe AS because the loss of
atrial contraction and the rapid heart rate both limit diastolic filling of a small, stiff LV. AF
increases the risk of HF and non-hemorrhagic stroke [27, 45]. Infective endocarditis can
occur in patients with AS, particularly those with a bicuspid AV. In a series of 2,401 patients
with congenital heart lesions who were followed prospectively, those with AS developed
infective endocarditis at a rate of 0.27 percent per year [46]. A higher peak gradient across the
AV was associated with a greater risk of infective endocarditis. Although definite evidence is
lacking, it has been proposed that the risk of infective endocarditis is lower in older patients
with heavily calcified valves than in younger patients with less severe abnormalities.
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Antibiotic prophylaxis is no longer recommended when patients with AS undergo dental or
other invasive procedures that produce significant bacteremia with organisms associated with
infective endocarditis. Antibiotic prophylaxis is recommended in certain high-risk groups
(e.g., patients with prior infective endocarditis) [18, 34]. Patients with AS have an increased
risk of bleeding, particularly in the gastrointestinal tract and at skin and mucosal sites [47].
The association between chronic gastrointestinal bleeding due to angiodysplasia and
degenerative aortic valve disease has been named Heyde syndrome [48]. In a series of 42
patients with severe AS undergoing AVR, 9 had a history of skin or mucosal bleeding, and 4
had a history of gastrointestinal bleeding. The increased risk of bleeding is attributed to an
acquired von Willebrand syndrome, which has been described in 67 to 92% of patients with
severe AS. This abnormality is thought to result from mechanical disruption of von
Willebrand multimers during turbulent passage through the narrowed valve and an interaction
between the von Willebrand factor and platelets that promotes platelet clearance [47, 49]. The
severity of the von Willebrand factor abnormality is directly related to the mean transvalvular
gradient [47, 50, 51]. The hemostatic abnormality is corrected after surgery but recurs within
6 months of AVR in two-thirds of patients, especially when there is a mismatch between
patient and prosthesis (an effective orifice area <0.8 cm2/m2). The association between AS
and angiodysplasia seems apparent, since patients with AS have an increased bleeding
tendency, leading to the identification of angiodysplasia [17, 27].
Aortic Regurgitation
Acute Aortic Regurgitation
Symptoms and Signs
Severe acute AR commonly presents with acute HF or cardiogenic shock, with profound
hypotension, pallor, diaphoresis, signs of peripheral vasoconstriction, and pulmonary edema.
The pulse pressure may be normal or reduced, but the arterial pulsation is rapid and usually
with low amplitude [5]. The cardiac apex is generally not displaced and not hyperdynamic
[5]. In cases of aortic dissection, pulses and blood pressure values in the left and right arms
may be inequal [52]. The peripheral manifestations of chronic AR, associated with an
increased pulse pressure (listed below) may be absent in patients with acute AR, since LV
stroke volume and pulse pressure are not significantly increased [5].
Acute AR is often characterized by a low-pitched early diastolic murmur beginning after
S2. The murmur is sometimes not audible and its location may be variable. A systolic
murmur resulting from the increased volume of blood crossing the aortic valve may be heard,
but is usually not loud. Furthermore, acute AR alters the quality of heart sounds: the early
closure of the mitral valve generally produces a soft or absent S1, which can occasionally be
heard in mid-diastole; the aortic component of S2 is often soft, while P2 is usually increased,
reflecting pulmonary hypertension; an S3 is often heard, but an S4 is absent [5].
Other possible symptoms are related to the cause of acute AR, such as infective
endocarditis or aortic dissection. In some cases, acute AR is the first diagnostic clue to these
conditions. Aortic dissection should always be suspected in patients with AR and chest or
back pain [52].
Соседние файлы в папке Библиотека им академика М.И. Перельмана