Aortic Valve Flashcards
What is the relative use of mechanical vs tissue valves?
15%, USA 2011
Name 5 points in evaluating a valve procedure’s effectiveness
- Ease of performance
- Safety
- Efficacy (haemodynamics, EOA)
- Durability
- Event-free survival
Should patients having other cardiac surgery and moderate AS undergo AS?
Yes, class IIa indication, level of evidence B
Give 4 indicators of prosthetic aortic valve dysfunction
- Valve area 20mmHg
- Peak velocity >3m/s
- Moderate or severe AR
Give 3 class I indications for AVR in aortic stenosis
- Severe AS and symptoms
- Severe AS and LVEF <50%
- Severe AS undergoing other cardiac surgery
What class of indication is AVR for an asymptomatic patient with exercise induced symptoms or abnormal blood pressure response (hypotension)
Class IIb, level of evidence C
Is severe asymptomatic AS with high likelihood of progression (age, calcification, CAD) a class I indication for AVR?
No. Class IIb, level of evidence C
Define severe aortic stenosis (with normal LV)
- Peak Doppler echo >4m/s
- Mean gradient >4mmHg
- Valve area <1.0cm2
Is AVR indicated for asymptomatic very severe AS (area 5 m/s, mean >60mmHg)?
Only a class IIb, level C indication if operative mortality <1.0%
Give 3 class I indications for AVR in aortic regurgitation
- Symptomatic severe AR
- Asymptomatic severe AR and LVEF <50%
- Severe AR undergoing other cardiac surgery
When is AVR indicated in severe asymptomatic AR and normal LV systolic function?
LVESD >50mm LVEDD >70mm Or progressive LV dilatation Or declining exercise tolerance Or abnormal haemodynamic response to exercise
Define severe aortic regurgitation
Evidence of volume load on LV &: Regurgitant orifice area >0.3cm2 Regurgitant fraction>60% Regurgitant volume >60ml/beat Vena contracta width >0.6cm (point in a fluid stream where the diameter is the least)
Give 3 indications for surgery in aortic valve endocarditis
- Severe heart failure
- Abscesses, heart block, resistant infection
- Recurrent emboli
Give 5 measurements indicating a need for replacement of the ascending aorta or root when aortic valve is bicuspid
- Diameter > 5.0cm (5.5 if tricuspid)
- Diameter > 2.5cm/m2
- Cross-section : Ht ratio >10cm2/m
- Dilating >0.5cm/yr
- > 4.5cm if undergoing AVR
Give the 4 main factors to consider in the preoperative assessment of AS
- Verify disease severity
- Evaluate LV function
- Assess for coronary disease
- Delineate major comorbidities
What is the expected survival for untreated severe symptomatic AS?
Mean survival 2 years (1yr 50%, 5 yr 20%)
Give a definition of frailty
3 or more of following present:
- unintentional weight loss >10lb/yr
- self-reported exhaustion
- weakness (grip strength)
- slow walk speed (<5m/6sec)
- low physical activity
Give 3 physical signs of AR
- decrescendo diastolic murmur left sternal border
- wide pulse pressure
- bounding pulses
Give 3 physical findings in AS
- ejection systolic murmur, radiation to carotids
- single or paradoxically split 2nd sound
- diminished carotid upstroke
What features might be seen on a CXR in AS?
- rounded heart border due to LVH
- aortic calcification
- pulmonary oedema + cephalic blood flow in left heart failure
What PFT values predict increased postoperative morbidity after AVR?
- pCO2 >50mmHg
* FEV1 <50%
How might chronic pulmonary disease be distinguished from AS as a cause of dyspnoea?
Balloon aortic valvuloplasty (BAV) as a physiological test
What is the Gallavardin phenomenon in AS?
The musical component of an AS murmur best heard at the apex
What ECG changes occur with AS?
- Evidence of LVH
* Conduction abnormalities (LBBB or RBBB with R/L axis deviation)
Give 6 class I indications for rchocardiography in AS or AR
- check severity
- assess LV size, function, wall thickness
- changing signs & symptoms
- monitor asymptomatic patients
- monitor change in pregnancy
- check intra-operative repair / replacement
How often should asymptomatic AS or AR patients have echo assessment?
- severe 6 months
- moderate 1-2 years
- mild 3-5 years
What is the role of exercise testing in AS or AR?
May be considered if asymptomatic to induce symptoms or abnormal blood pressure response [<20mmHg rise] (class IIb). It should not be performed if symptomatic (high risk complications)
How can true gradients be determined in AS with LV dysfunction?
This is low-flow low-gradient AS → low-dose dobutamine infusion
What ECG changes occur with exercise testing in AS?
80% develop ST-depression, of no known prognostic value
What are the uses of CT in assessment for TAVI?
- potential leaflet calcium obstructing coronary ostia
- aortic annulus diameter
- assess aortoiliac system (size, disease,(tortuosity)
What is a positive test in dobutamine stress echo?
Fixed valve area with an increase in gradient and stroke volume
Failure to increase stroke volume => lack of contractile reserve → very poor prognosis (with medicine or surgery)
Give 4 class I indications for cardiac catheterisation in assessment of AS or AR
- look for coronary disease if risk factors
- look for coronary disease if >45 years
- haemodynamic measurements if inconclusive non-invasive tests
- Ross procedure planned
What measurements are made, if indicated, to assess AS at cardiac catheterisation?
- simultaneous LV and ascending aortic pressures
* cardiac output by Fick principle or indicator-dilution
How often is the Circle of Willis incomplete?
15%
What are the cannulation options for AVR and aortic root surgery?
- ascending aorta
- aortic arch
- axillary /subclavian (with 8mm dacron graft)
- femoral artery (right is spared in 80% of dissections)
- LV apex
What are the disadvantages of femoral artery cannulation?
- size (achieving adequate body perfusion)
- distal limb perfusion compromise
- atherosclerotic disease involvement (emboli)
Give 4 class I management recommendations for patients receiving mechanical AVR
- preoperative coronary angiogram for CAD symptoms, risk or age >45
- perioperative antibiotic prophylaxis
- warfarin for life
- dental antibiotic cover
What orientation gives the least turbulence in mechanical bileaflet AVR?
Axis of leaflets in middle of non-coronary cusp
Give 5 potential late complications of mechanical AVR
- thromboembolism & bleeding (warfarin)
- structural dysfunction
- non-structural dysfunction (paravalvular leak, haemolysis)
- tissue ingrowth
- endocarditis
What are the approximate rates of mechanical AVR complications?
- structural dysfunction 0.1% / yr
- non-structural dysfunction 0.2% / yr
- thromboembolism 1-2% / yr
- bleeding 1-2% / yr
- endocarditis 0.5% / yr
Give 4 indications for tissue over mechanical AVR
- Contraindication to anticoagulation (class I)
- age >65 (class I)
- patient preference (class IIa)
- woman of childbearing age (class IIb)
What are the 3 types of tissue prosthesis?
- xenograft (stented, stentless) - porcine, pericardial
- homograft (=allograft)
- autograft (Ross procedure)
How does the internal diameter of a bioprosthesis relate to it’s labelled valve sizer?
standard valve 4-6mmHg smaller
suprannular valve 2-4mmHg smaller
What are the pros and cons of collagen cross-linking with gluteraldehyde of bioprostheses?
Pros: * block immune response * tissue stabilisation Cons: * creates calcium influx * exposes residual phospholipids (→ Ca++ binding)
What factors increase to rate of structural valve deterioration of bioprostheses?
Age Female Larger valve Mitral position Renal failure Hyperparathyroidism Hypertension
What are the structural valve deterioration incidence by 15 years for a bioprosthesis inserted at age: >65, <40?
> 65 → 10%
<40 → 40%
How does structural valve deterioration differ between porcine and pericardial valves?
Porcine valve calcification at areas of high stress (commissures) leading to acute tears
Pericardial calcification diffuse, leading to gradual AS
In aortic valve replacement, what is the effective orifice area (EOA) index?
EOA/BSA, used to identify patient prosthesis mismatch (ppm)
What is patient-prosthesis mismatch and how is it defined?
Present when the effective prosthetic heart valve area, after insertion into the patient, is less than that of a normal human valve. Use same criteria as for native valve stenosis (e.g. severe if <0.6cm2/m2
When should patch enlargement of aortic root be considered in AVR?
When EOA of prosthesis will be <0.65cm2/m2
Give 5 methods to increase inserted prosthesis size in the small aortic root
- Konno - through R sinus into muscular septum
- Manouguian - through NC/LC commissure, may involve LA dome
- Nicks - through mid NC sinus, maybe onto anterior MV leaflet
- Supra-annular insertion
- Root replacement
Give 2 class I recommendations in homograft replacement of the aortic valve
- Consider in endocarditis with extensive destruction of annulus
- Use as a root replacement preferred
Describe 3 types of homograft AVR
- Sub-coronary implantation
- Root inclusion cylinder
- Total root replacement
Give 3 pros & 3 cons of stentless aortic valve replacement
Pros: 1. Excellent haemodynamics 2. Avoid anticoagulation 3. Readily available Cons: 1. More demanding insertion 2. Uncertain durability 3. TAVI replacement difficult
Give 3 potential indications for stentless aortic root replacement
- Small root with high risk patient-prosthesis mismatch
- Aneurysmal root
- Endocarditis with annular destruction
What is the main indication for AVR using the Ross procedure?
Children with no suitable alternative
What are the long-term disadvantages of the Ross procedure?
- neo-aortic dilatation
- neo-aortic valve regurgitation
- pulmonary homograft failure
