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JOURNAL OF CARDIOVASCULAR DISEASE
ISSN: 2330-4596 (Print) / 2330-460X (Online)
VOL.2 NO.4
JULY 2014
http://www.researchpub.org/journal/jcvd/jcvd.html
Pitfalls in the Estimation of the Severity of a
“Low-Flow Low-Gradient” Aortic Valve
Stenosis in absence of Contractile Reserve
Wilhelm P. Mistiaen, MD, ScD, PhD, Philip Van Cauwelaert, MD and Philip Muylaert, MD

Abstract— In some patients, the severity of aortic valve
stenosis is difficult to estimate. In an elderly patient with
aortic valve stenosis, heart failure and other co-morbid
conditions, severity of aortic valve stenosis was estimated
with a dobutamine stress echocardiography. The patient
died six days after valve replacement. A literature search
revealed pitfalls in the diagnostic procedure and difficulties
in
the
interpretation
of
dobutamine
stress
echocardiography. Absence of contractile reserve, low
mean transvalvular gradient and presence of coronary
artery disease in this patient can be considered as increased
risk. However, valve replacement might be offered on an
individual basis.
Keywords — Aortic valve stenosis, low-flow low-gradient,
dobutamine stress echocardiography.
Cite this article as: Mistiaen WP, Van Cauwelaert P, Muylaert
P. Pitfalls in the Estimation of the Severity of a “Low-Flow
Low-Gradient” Aortic Valve Stenosis in absence of Contractile
Reserve. JCvD 2014;2(4):213-217.
I. INTRODUCTION
T
HE only life-prolonging treatment for symptomatic severe
calcified aortic valve stenosis (CAVS) is aortic valve
replacement (AVR). The criteria for severe CAVS are an aortic
valve area (AVA) of less than 1.0 cm², a mean transvalvular
gradient (TVG) of over 40 mmHg and an aortic peak jet
velocity (PJV) of over 4 m/sec. However, there are some
difficulties that can be encountered in the evaluation of some
patients.1 First, symptoms are notoriously difficult to provoke
in elderly patients.2,3 Second, there can be a discrepancy
between indicators of severe CAVS.3,4 This makes use of these
This paper is submitted for review on January 15, 2014. There has been no
funding or financial support to declare. There are no conflicts of interests.
Affiliations: University of Antwerp, Faculty of Medicine and Health Sciences,
Antwerp, Belgium; Artesis-Plantijn University College, Dept. of Healthcare
Sciences, Antwerp, Belgium (first author); ZNA Hospital Middelheim, Dept. of
Cardiovascular Surgery, Antwerp, Belgium (second and third author).
Correspondence to ([email protected] )
213
measurements as sole parameters undesirable.1 Third,
concomitant disorders such as arterial hypertension and
coronary atheromatosis, which are frequent in patients with
CAVS 5,6 can have an additional effect on the left ventricular
(LV) function.1 We present a case of an elderly man with
CAVS in whom difficulties and pitfalls have been encountered,
which could have been avoidable.
II. CASE
A male patient of 86 years had a long history of
cardiovascular disease. This included hypertension (AHT),
diabetes with retinopathy, chronic kidney disease, coronary
artery disease complicated with acute myocardial infarction
and with episodes of unstable angina, atrial fibrillation and
bradycardia, which needed pacemaker implantation as well as
recurrent transient ischemic attacks. Episodes of heart failure
were treated with infusions of dobutrex. The patient also had
polycythemia vera, which was under control. The patient
complained of gradually increasing dyspnea. Physical
examination revealed a blood pressure of 115/90 mmHg. There
were no clinical signs of overt heart failure. An ejection
murmur was clearly audible.
Electrocardiography showed a pacemaker rhythm.
Echocardiography showed a poorly contractile dilated
hypertrophic LV, with an ejection fraction (EF) of 13% and an
increased LV end-diastolic pressure. The aortic valve was
calcified with a mean TVG of 13 mm Hg. AVA was estimated
at 0.96 cm².There was a moderate mitral valve regurgitation. A
dobutamine stress echocardiography (DSE) confirmed the
presence of a dilated LV with poor function. Infusion of 40 µg
Dobutamine did not result in an increase in AVA. There was no
mentioning of change in LV contractility. The patient was
diagnosed with severe CAVS with deteriorating LV function.
He was referred for AVR. Coronary angiography also revealed
serious disease of the dominant right coronary artery. The left
coronary artery was moderately affected. The EUROScore was
14%.
The patient underwent coronary artery bypass grafting (A
venous jump graft on the right coronary artery) and AVR
(Medtronic Mosaic size 27). A slow weaning of extracorporeal
circulation was possible. The postoperative course was initially
favourable. Arterial partial oxygen pressure was kept over 95
mmHg, by mechanical ventilation for 54 hours with 40%
oxygen and positive end-expiratory pressure of 5 mmHg. The
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patient was sedated for 2 days. On the second day, recurrent
short bursts of ventricular tachycardia were observed, for which
intravenous amiodarone was started. There was a prolonged
need for inotropic medication: decreasing doses of
noradrenalin for 2 days, dopamine for 3 days, with cardiac
index varying between 1.2 and 2.5 litres/minute/m². Left atrial
pressure reached levels of 33 mmHg. After 5 days, the patient
could be transferred to the ward. At the 6th day, an
electromechanical dissociation occurred. Cardiopulmonary
resuscitation had no result. Necropsy showed a severely dilated
left ventricle, severe pulmonary oedema but no signs of recent
ischemia or bleeding. There were no other abnormalities
observed at gross examination.
TABLE I
SOURCES OF ERROR IN ESTIMATING SEVERITY OF CAVS
Ref
Source
Significance
4
Vena contracta
Overestimation of severity
1,3,4,9
Pressure recovery
Overestimation of severity
7,12
Mal-alignment of
Doppler beam
Underestimation of PJV
Aortic valve
regurgitation
Underestimation of AVA
7,9,11,
12,20
Underestimation of left
ventricular outflow
tract cross section
Underestimation of flow, stroke
volume and of AVA
4,14
Beat to beat variation
of Doppler wave
Mismatch between AVA and TVG
III. DISCUSSION
Echocardiography is the first choice to diagnose and estimate
the severity of CAVS.7,8 It can describe the parameters of other
valves, of LV function and of other cavities.9 Echocardiography
is operator dependent, however. The classical parameters
which can be measured or calculated by echocardiography are
mean TVG, AVA, and PJV. The left ventricle can be examined
for its function and presence of hypertrophy. Mean TVG is
more flow dependent than AVA, while the latter is more prone
to measurement errors. AVA needs also indexing. PJV is more
robust and reproducible. PJV can be a part of an integrated
approach, together with AVA and mean TVG.1,7,10,11
Using these common parameters, a spectrum in presentation of
symptomatic CAVS can be discerned, ranging from a
normal-flow high-gradient CAVS with preserved LVEF,12
paradoxical low-flow low-gradient case with preserved LVEF
and a low-flow low gradient case with low LVEF. Low-flow
states with small AVA and discrepantly low TVG need to be
distinguished from a pseudo-severe CAVS 1,12, because a low
TVG does not exclude severe CAVS. A more comprehensive
approach is required for difficult cases.11,12
Before considering measurement inconsistencies, other
sources of error must be ruled out. These can be found in table
I. These sources can be responsible for errors in calculation of
AVA and stroke volume and hence for a mismatch between
AVA and TVG. Moreover catheter based and
echocardiographic measurement of AVA and TVG are not
necessarily interchangeable.1,3,4,9
Furthermore, mutual inconsistent criteria for severity of
CAVS must be taken into account: an AVA of 1.0 cm²
corresponds better with a mean TVG of 30-35 mmHg and less
with 40 mmHg, which is considered a cut-off value. It might be
tempting to lower this cut-off to 0.8 cm², but is has been
demonstrated that an AVA of less than 1.0 cm² predicts
excessive mortality irrespective of the level of TGV and of
symptomatic status .3,10,13
Several additional hemodynamic and other parameters can
be measured to assess the severity of CAVS in difficult cases.
These can be found in table II. The current case is a low-flow
state with low LVEF, in which an echocardiography at rest
might not solve the problem. Application of DSE has a class IIa
recommendation with an evidence of level B.3,4,9,13 If a
contractile reserve is present, the infusion of dobutamine during
214
CAVS = Calcified aortic valve stenosis; PJV = peak jet velocity; AVA=
aortic valve area; TVG= transvalvular gradient
DSE increases the transvalvular flow and stroke volume index
(SVI) because of the inotropic effect.14 For the latter, SVI is a
better parameter than cardiac index, since mean TVG depends
more on flow per beat than on flow per minute.13 Induction of
ischemia and ventricular arrhythmias must be avoided, by using
low doses and longer stages to reach a steady state. Three
possibilities can be discerned.2,4,7,8,12
1) Increase of stroke volume index (>20%) and in TVG
(>40 mmHg) or PJV (>4 m/sec) with fixed AVA (<1.0
cm²). This is a true severe CAVS.
2) Increase of stroke volume index and in AVA (>0.2
cm²), but without increase in TVG or PJV: this is a
pseudo-severe CAVS.
3) No increase in stroke volume index due to lack in
contractile reserve: the severity of CAVS cannot be
determined by this technique.13
The presence of coronary artery disease, of previous
infarction or of other myocardial diseases (exhaustion by
prolonged afterload mismatch can nullify the inotropic effect of
dobutamin. This could be the case in the current patient. The
rise in flow and TVG will be less than expected .13
An additional parameter of DSE is the projected AVA. The
variable increase in flow during DSE can make interpretations
for individual patients difficult. To overcome this difficulty, the
projected AVA (the expected AVA with standard flow of
250ml/sec) can be derived from the AVA/flow curve. A
projected AVA<1.0cm² is considered as marker for severe
CAVS.2,4,13-15
The use of DSE has its limitations: its results predicts only the
operative risk, not the long-term results.13,16 Preoperative risk
factors for operative mortality are absence of contractile
reserve, mean TVG under 20 mmHg and presence of
multi-vessel coronary artery disease.13 Operative mortality in
patients without contractile reserve is estimated between 30%
JOURNAL OF CARDIOVASCULAR DISEASE
ISSN: 2330-4596 (Print) / 2330-460X (Online)
VOL.2 NO.4
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TABLE II
ADDITIONAL PARAMETERS FOR ADEQUATE ESTIMATION OF
SEVERITY OF CAVS
Ref
Parameter
Significance
1
Energy loss coefficient
More equivalent to AVA; requires
inclusion of several parameters;
prone to error
1
Stroke work loss
Takes pressure recovery into account;
is more predictive for outcome than
AVA
1,11,12
Stroke volume index
Requires inclusion of several
parameters; it is superior to cardiac
index but prone to error
1
Valvulo-arterial
impedance
Measures the total ventricular
afterload; the effect of
pseudonormalized hypertension can
be underestimated
21
Upstroke of Doppler
wave form
Is an indication of ejection time and
severity of CAVS; is slower in severe
CAVS
8,10
Pulmonary artery
pressure
Is an indication for left ventricular
diastolic dysfunction
12,13
Abnormal longitudinal
left ventricular
function
Predictor of adverse outcome after
AVR; indicates left ventricular
fibrosis
12,14
Calcium score on
computer tomography
Estimates severity of CAVS and is an
indicator of its rate progression
survivors of AVR, benefit from the operation, since it relieves
the LV from the after-load mismatch. Moreover, operative risks
of AVR improved over time.19
The available literature reveals a large number of possible
parameters in the evaluation of the severity of CAVS in
difficult cases. The most commonly used parameters are shown
in table II. No single parameter can represent the severity of
CAVS in all patients. For patients with a low-flow state, the
parameters which are most easy to determine and with high
sensitivity and specificity, as shown in table I, should be
selected. The experience of the operator plays a major role
herein.
IV. CONCLUSIONS.
In this difficult case, even DSE could not solve all problems
in estimating the severity of CAVS. Even an explicitly
documented lack of contractile reserve could be partially
reversible due to concomitant treatment of coronary artery
disease. What could be helpful in the decision making are
documenting the projected AVA, the presence of myocardial
fibrosis, the plasma level of B-type natriuretic peptide and the
calcium score. This patient was operated in an era when
trans-catheter aortic valve implantation was upcoming. In such
patients, this approach could be an alternative.
V. ACKNOWLEDGMENTS
CAVS = Calcified aortic valve stenosis; AVA= aortic valve area; AVR=
aortic valve replacement;
16-18
and 50%.
In patients with low TVG, operative mortality
increased to 53% and in patients with prior AMI, this was even
67%.14,16 These data illustrate the necessity of individual
tailoring of the treatment of this condition by AVR, for which a
class IIa, level C evidence has been proposed by the European
Society of Cardiology / European Association of
Cardio-Thoracic Surgery.13 However, a long-term beneficial
effect of the operation in terms of New York Heart Association
functional status and improvement of LVEF has been observed.
The lack of contractile reserve is not necessarily due to an
irreversible LV dysfunction and is not always a reason to deny
the operation.16
These observations seem to justify the operation in this case,
but some comments have to be made. Age is in itself not a
reason to deny AVR 5, but it should be taken into consideration
together with the co-morbid conditions. On the one hand, there
were some conditions increasing the operative risk: a
“pseudo-normalized” hypertension, atrial fibrillation and the
need for a pacemaker. The very low mean TVG, the need for
coronary artery bypass grafting, a previous AMI and the very
low LVEF in this patient were all predictors for an increase in
operative mortality. A very low LVEF and an absence of
increase in TVG during DSE could indicate to an absence of
contractile reserve. This was not described explicitly in this
patient. On the other hand, if this absence of contractile reserve
was due to ischemia during DSE, this absence could be
reversed by coronary artery bypass grafting. Furthermore,
215
There are no conflicts of interest to declare.
There was no financial support
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JOURNAL OF CARDIOVASCULAR DISEASE
ISSN: 2330-4596 (Print) / 2330-460X (Online)
VOL.2 NO.4
JULY 2014
http://www.researchpub.org/journal/jcvd/jcvd.html
Wilhelm P. Mistiaen graduated as MD in
1984 and earned a PhD in 1999 and in 2009. He is currently
employed as associate professor at the University of Antwerp
and Artesis-Plantijn University College, Antwerp, Belgium. He
is a member of the Society of Heart Valve Disease and
published about 20 papers concerning aortic valve disease and
replacement. The current interest are complications after aortic
valve replacement and their predictors
217