Aortic Stenosis & Aortic Stenosis & Non-Cardiac SurgeryNon-Cardiac Surgery

Stephen R. Ellis, MDStephen R. Ellis, MD

David Warters, MDDavid Warters, MD

ABG: ABG: – 7.58/32/472/30/8.27.58/32/472/30/8.2– Na/K 139/3.8Na/K 139/3.8– HCT 44HCT 44

IntroductionIntroduction

Aortic stenosis derives its position as Aortic stenosis derives its position as the most important valvular lesion the most important valvular lesion because of its potential for sudden because of its potential for sudden death (15–20%), and because of the death (15–20%), and because of the inability to obtain adequate systemic inability to obtain adequate systemic perfusion by external cardiac perfusion by external cardiac massage during a cardiac arrest. massage during a cardiac arrest.

IntroductionIntroduction

AorticAortic stenosisstenosis without accompanying without accompanying mitral valve diseasemitral valve disease is more common in is more common in men than in women and very rarely occurs men than in women and very rarely occurs on a rheumatic basis. Instead, isolated AS on a rheumatic basis. Instead, isolated AS is usually either congenital or is usually either congenital or degenerative in origin. degenerative in origin.

The natural history of the disease is of a The natural history of the disease is of a long asymptomatic latent period followed long asymptomatic latent period followed by the onset of characteristic symptoms by the onset of characteristic symptoms (angina, syncope, dyspnea). (angina, syncope, dyspnea).

EtiologyEtiology

Degenerative calcific aortic stenosisDegenerative calcific aortic stenosis – Mechanical stress over time leads to Mechanical stress over time leads to

progressive fibrosis and calcification of a progressive fibrosis and calcification of a previously normal tri-leaflet valve. previously normal tri-leaflet valve.

– Initially, this process is seen as sclerosis. Initially, this process is seen as sclerosis. – It is an early form of the disease that can It is an early form of the disease that can

progress to stenosis. progress to stenosis. – associated with many of the risk factors for associated with many of the risk factors for

coronary artery disease - diabetes, coronary artery disease - diabetes, hypercholesterolaemia, smoking and hypercholesterolaemia, smoking and hypertension.hypertension.

EtiologyEtiology Congenital bicuspid aortic valveCongenital bicuspid aortic valve

– Bicuspid aortic valve is the most common Bicuspid aortic valve is the most common congenital cardiac malformation ( 2% of general congenital cardiac malformation ( 2% of general population). population).

– abnormal valve structure - two rather than three abnormal valve structure - two rather than three leaflets - leads to turbulent flow, which, in turn, leaflets - leads to turbulent flow, which, in turn, can produce fibrosis, calcification and orifice can produce fibrosis, calcification and orifice narrowing secondary to trauma. narrowing secondary to trauma.

– commonly produces symptoms in the fourth to commonly produces symptoms in the fourth to sixth decades of life.sixth decades of life.

– accounts for 50% of patients <70 yr requiring accounts for 50% of patients <70 yr requiring aortic valve surgery for stenosis but only 25% of aortic valve surgery for stenosis but only 25% of those >70 yr.those >70 yr.

EtiologyEtiology Rheumatic ASRheumatic AS

– results from adhesions and fusions of the results from adhesions and fusions of the commissures and cuspscommissures and cusps

– There is vascularization of the leaflets of the There is vascularization of the leaflets of the valve ringvalve ring

– This leads to retraction and stiffening of the This leads to retraction and stiffening of the free borders of the cusps. free borders of the cusps.

– Calcific nodules develop on both surfaces, and Calcific nodules develop on both surfaces, and the orifice is reduced to a small round or the orifice is reduced to a small round or triangular opening. triangular opening.

– As a consequence, the rheumatic valve is often As a consequence, the rheumatic valve is often regurgitant and stenoticregurgitant and stenotic

EtiologyEtiology

A.A. Normal aortic valve. Normal aortic valve.

B.B. Congenital aortic Congenital aortic stenosis. stenosis.

C.C. Rheumatic aortic Rheumatic aortic stenosis.stenosis.

D.D. Calcific aortic Calcific aortic stenosis. stenosis.

E.E. Calcific senile aortic Calcific senile aortic stenosis.stenosis.

ClassificationClassification

Mild AS – AVA 1.2-1.8cmMild AS – AVA 1.2-1.8cm22, mean gradient , mean gradient 12-25 mmHg12-25 mmHg

Moderate AS – AVA 0.8-1.2cmModerate AS – AVA 0.8-1.2cm22, mean , mean gradient 40-50 mmHggradient 40-50 mmHg

Severe AS – AVA <0.8cmSevere AS – AVA <0.8cm22, mean gradient , mean gradient > 50 mmHg> 50 mmHg

PathophysiologyPathophysiology The normal aortic valve area (AVA) is 2.6–The normal aortic valve area (AVA) is 2.6–

3.5 cm3.5 cm22 in adults. in adults. Hemodynamically significant obstruction Hemodynamically significant obstruction

occurs as the AVA approaches 1.0 cmoccurs as the AVA approaches 1.0 cm22.. Increasing obstruction hypertrophy, Increasing obstruction hypertrophy,

which allows the LV to maintain a pressure which allows the LV to maintain a pressure gradient across the valve without dilating gradient across the valve without dilating or reducing the cardiac output.or reducing the cardiac output.

PathophysiologyPathophysiology However, over time the hypertrophied However, over time the hypertrophied

ventricle becomes increasingly stiff, ventricle becomes increasingly stiff, diastolic dysfunction with a reduced diastolic dysfunction with a reduced compliance. compliance.

This is transmitted to the pulmonary This is transmitted to the pulmonary circulation circulation pulmonary pulmonary edemaedema

PathophysiologyPathophysiology A normal sinus rhythm is beneficial as the A normal sinus rhythm is beneficial as the

left atrial kick accounts for 40% of LV left atrial kick accounts for 40% of LV filling. filling.

LA hypertrophies secondary to this LA hypertrophies secondary to this increased demand on it increased increased demand on it increased chance of atrial fibrillation.chance of atrial fibrillation.

Major alterations of myocardial oxygen Major alterations of myocardial oxygen supply and demand occur.supply and demand occur.

The ventricle becomes The ventricle becomes – very sensitive to changes in preloadvery sensitive to changes in preload– dependent on the maintenance of sinus rhythm dependent on the maintenance of sinus rhythm – susceptible to ischemia, especially when susceptible to ischemia, especially when

arterial pressure is reduced.arterial pressure is reduced.

PathophysiologyPathophysiology

Eventually, cardiac output, stroke volume Eventually, cardiac output, stroke volume and therefore pressure gradient across the and therefore pressure gradient across the valve fall. valve fall.

Left ventricular dilatation occurs late in the Left ventricular dilatation occurs late in the disease processdisease process

PathophysiologyPathophysiology There is a There is a

direct direct relationship b/w relationship b/w the aortic valve the aortic valve area and the area and the flow across the flow across the valve.valve.

Blood flow is Blood flow is not significantly not significantly impeded until impeded until the aortic valve the aortic valve area is < 0.5-area is < 0.5-0.7 cm0.7 cm22

PathophysiologyPathophysiology

Assessment - SymptomsAssessment - Symptoms

As stated the three cardinal signs of As stated the three cardinal signs of AS are – angina, syncope, and AS are – angina, syncope, and dyspnea.dyspnea.

Angina Angina – occurs as oxygen demand from the occurs as oxygen demand from the

hypertrophied LV outstrips the supplyhypertrophied LV outstrips the supply– Initial symptom in 50-70% of ptsInitial symptom in 50-70% of pts

Syncope Syncope – etiology unclearetiology unclear– Initial symptom in 15-30% of pts Initial symptom in 15-30% of pts

Assessment - SymptomsAssessment - Symptoms

Dyspnea – pulmonary congestion, Dyspnea – pulmonary congestion, CHFCHF

Symptoms that develop late in AS, Symptoms that develop late in AS, and reflect inc pulmonary HTN – and reflect inc pulmonary HTN – exertional dyspnea, orthopnea, PND, exertional dyspnea, orthopnea, PND, pulmonary edemapulmonary edema

Assessment - ExamAssessment - Exam

Arterial pulse is slow rising, and of Arterial pulse is slow rising, and of low volumelow volume

Carotid thrillCarotid thrill Precordial thrill with leaning forward Precordial thrill with leaning forward

during expirationduring expiration Late systolic murmur (2Late systolic murmur (2ndnd intercostal intercostal

space at base of heart)space at base of heart)

Assessment - ExamAssessment - Exam

EKG:EKG:– LVH – present in ~ 85% of ptsLVH – present in ~ 85% of pts– T-wave inversion & ST depression as T-wave inversion & ST depression as

hypertrophy becomes worsehypertrophy becomes worse– AV and intraventricular blocks can be AV and intraventricular blocks can be

seenseen

Assessment - ExamAssessment - Exam

ECHO:ECHO:– Used to assess the anatomy of the aortic Used to assess the anatomy of the aortic

valve, grade the stenosis, and assess LV valve, grade the stenosis, and assess LV function.function.

Assessment - ExamAssessment - Exam

ECHO:ECHO:

Anesthetic Management for Anesthetic Management for Non-Cardiac SurgeryNon-Cardiac Surgery

Careful hemodynamic monitoring is essential:Careful hemodynamic monitoring is essential:– Arterial lineArterial line

AorticAortic stenosisstenosis produces a fixed obstruction to left produces a fixed obstruction to left ventricular ejection that results in reduced stroke volume ventricular ejection that results in reduced stroke volume and an arterial pressure waveform that rises slowly and an arterial pressure waveform that rises slowly ((pulsus tarduspulsus tardus) and peaks late in systole ) and peaks late in systole

Pulsus parvus (narrow pulse pressure) Pulsus parvus (narrow pulse pressure)

– CVC, or large bore PIVsCVC, or large bore PIVs– Swan-Ganz? Absolutely not, as the potential Swan-Ganz? Absolutely not, as the potential

for it to precipitate arrhythmias is too high. for it to precipitate arrhythmias is too high.– TEE is appropriate if availableTEE is appropriate if available

Anesthetic Management for AS Anesthetic Management for AS & Non-Cardiac Surgery& Non-Cardiac Surgery

Avoid systemic hypotensionAvoid systemic hypotension– leads to myocardial ischemia, and then decreased leads to myocardial ischemia, and then decreased

contractility and a vicious cycle ensues.contractility and a vicious cycle ensues.– vasoconstrictors must be at hand – consider an vasoconstrictors must be at hand – consider an

infusion from the beginninginfusion from the beginning– treat hypotension aggressivelytreat hypotension aggressively

Maintain sinus rhythmMaintain sinus rhythm– sinus tachy decreases diastolic time for sinus tachy decreases diastolic time for

myocardial perfusionmyocardial perfusion– sinus brady limits CO in pts with fixed stroke sinus brady limits CO in pts with fixed stroke

volumevolume

Anesthetic Management for AS Anesthetic Management for AS & Non-Cardiac Surgery& Non-Cardiac Surgery

Treat arrhythmias promptlyTreat arrhythmias promptly ContractilityContractility

– Stroke volume is maintained with a Stroke volume is maintained with a heightened contractile stateheightened contractile state

Maintain adequate intravascular Maintain adequate intravascular volume to ensure ventricular fillingvolume to ensure ventricular filling– b/c of dec LV compliance and inc LVEDP b/c of dec LV compliance and inc LVEDP

& LVEDV, preload augmentation is & LVEDV, preload augmentation is needed for a normal stroke volumeneeded for a normal stroke volume

Anesthetic Management for AS Anesthetic Management for AS & Non-Cardiac Surgery& Non-Cardiac Surgery

GA vs Regional:GA vs Regional:– successful use of spinal and epidural successful use of spinal and epidural

have been reported.have been reported.– Can use combined lumbar plexus and Can use combined lumbar plexus and

sciatic PNB for hipssciatic PNB for hips– GA is safe, as long as care is taken to GA is safe, as long as care is taken to

maintain blood pressure and sinus maintain blood pressure and sinus rhythmrhythm Narcotic-based technique is often usedNarcotic-based technique is often used

Postoperative ManagementPostoperative Management

Monitored bed with invasive Monitored bed with invasive monitoring, and adequate pain monitoring, and adequate pain control.control.

Maintain appropriate intravascular Maintain appropriate intravascular filling, blood pressure and sinus filling, blood pressure and sinus rhythm.rhythm.

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