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Bay Four

          Patterns, pearls and practical medicine

Aortic valve disease

Aortic stenosis: signs and investigation

  • Commonest valve disease in the developed world (moderate AS found in 3% of patients aged > 75)
  • Often underdiagnosed and undertreated
  • Symptoms
      • Can cause triad of (all increase the risk of SCD).
          • Exertional CP
          • SOB/CCF (this is the most worrying symptom)
          • Syncope/dizziness
      • Decompensated AS = worsening symptoms, heart failure, syncope, shock
      • Most develop symptoms before they develop heart failure
      • 40% of those with severe AS have no symptoms at diagnosis (but a third of these will have symptoms unmasked by exercise testing)
      • Outcomes are poor once symptomatic. 50% mortality at 2 years in severe symptomatic AS
  • Features
      • Slow rising, low volume pulse
      • Heaving apex beat
      • Harsh ejection systolic murmur radiating to carotids and softens with Valsalva
      • ECG may show LV strain pattern
  • Causes
      • Degenerative calcification (80%)
      • Bicuspid valve (or occasionally unicuspid)
          • More common in young patients
          • Often associated with aortic dilatation
      • Rheumatic fever
          • Especially in low/middle income countries
          • Often associated MV disease
      • Rarely
          • Congenital
          • Associated with Paget’s, SLE, CRF, Fabry’s, metabolic diseases, transthyretin cardiac amyloidosis
  • Clinical markers of severity
      • Narrow pulse pressure
      • Thrill
      • S4 present
      • A longer and later peaking murmur
  • Echo markers of severity
      • Mean pressure gradient (most robust parameter), peak transvalvular velocity (Vmax), and effective AVA (which has various technical limitations)
      • Severe AS is a bit more complicated to define than this, but generally taken to be
          • Peak transvalvular velocity of >4m/s
          • And mean pressure gradient >40mmHg
          • And/or aortic valve area (AVA) of < 1.0 cm2
      • Evaluate LV EF and stroke volume index (SVi) when there is discordance between echocardiographic parameters
      • Cardiac computed tomography calcium AV scoring also correlates with severity and outcomes
  • Work up
      • CTCA often used (calcium scores correlates closely to severity of AS, and helps assess suitability for TAVI)
      • Exercise testing can be useful if no symptoms, in order to aid decision making re interventions, but often not possible if mobility poor or frail
      • Troponin and BNP (used in intervention decisions)
      • CMR can help ascertain whether LV dysfunction is related to AS, remodelling or scarring/fibrosis (which has a worse outcome)
      • Sometimes stress echo or CMR required

Aortic stenosis: general management

  • Depends on
      • Symptoms (and deemed ‘symptomatic’ if symptoms uncovered by exercise testing)
      • Severity on echo
      • Frailty / age / comorbidities / estimated life expectancy
      • LV function
      • Procedural risk
      • Patient preference
  • If severe – advise no driving and no exercise
  • Prognosis of severe symptomatic AS is poor if untreated – so intervention generally advised if life expectancy is > 1 year
  • Generally refer for intervention if symptomatic and severe, or asymptomatic and any of:
      • Vmax (peak aortic jet velocity) >5m/s
      • Severe valve calcification and Vmax progression of >0.3m/s / year
      • Valve area <0.6cm2
      • EF <55%
      • Elevated troponin or BNP attributable to AS (some guidelines use BNP > 2 x ULN)
      • Symptoms on exercise testing (or haemodynamic intolerance (fall in BP >20 mm Hg))
  • However… not all severe AS is the same
      • Patients with severe AS are triaged as routine, expedited or urgent
      • If symptoms well controlled, gradient <100 and good LV function – could have a TAVI in 3-6 months
      • If NYHA 2-4 or angina or presyncope or moderate LV impairment – Get a CT and book TAVI in 1-3 months
      • If syncope, mean gradient >60, severe LV impairment (or deteriorating LV function), a/w urgent cancer treatment – needs urgent assessment within 2 weeks, CT scan and TAVI within 1 month
  • Not much evidence yet about treating asymptomatic AS
  • Check aortic valve calcium score on cardiac CT if severity of symptomatic AS is uncertain
  • For low gradient AS with reduced EF – often intervention will cause improvement in LV function (if it was due to excessive afterload), but not if it was due to fibrosis/scarring or cardiomyopathy
  • Moderate AS
      • Surveillance echo every 1-2 years
      • Surgical intervention only for those who also need a CABG, aortic surgery or other valve surgery
      • Rate of AS progression varies widely
  • Medical treatment for AS
      • No medical treatments have been shown to influence the natural history of AS
      • Treat HTN (to reduce additional afterload) – ACE-I probably best (titrate carefully)
      • Diuretics and betablockers can be used (especially if prognosis < 1 year or TAVI will have no effect on quality of life)
      • Treat HF as usual but don’t delay procedural intervention if required

Interventions for aortic stenosis

  • TAVI (transcatheter aortic valve implantation)
      • Role of TAVI is expanding and the surgery has become less invasive
      • Around 8000 done annually in UK, in > 30 centres (more than AVRs now)
      • Only performed in centres where cardiothoracic surgeons on site in case there are complications
      • 25% done urgently (and can be done in shocked patients with AS)
      • 94% performed under conscious sedation, and around 96% performed via femoral artery access
      • Takes around 45 minutes if uncomplicated
      • Average length of stay is 3 days if elective, but often monitored bed overnight and home the next day
      • No validated risk score
      • Usually transfemoral (can be transapical, or axillary)
      • Patient selection
          • Used in high risk and moderate risk. Low risk patients might be given TAVI as an option. Very low risk should be surgery, not TAVI
          • Useful if patient high risk and older, and this can be done urgently (but better if its planned).
          • Only generally considered if aged >70 (especially good if aged >80)
          • Younger patients with severe AS often have a bicuspid valve, and there is little data for these
          • Mean age for TAVI in the UK currently is 81
          • Might consider if aged >65 if previous sternotomy
          • Not useful if very poor LV function and frail (too high risk)
          • Generally favoured over surgical valve replacement if porcelain aorta, previous intact CABG, severe chest deformity/scoliosis, previous chest radiotherapy, frailty
      • Work up includes ECG, lung function, echo, CT angiogram (not an invasive angio unless high pretest likelihood of CAD) and gated CT aorta (vital to get sizing done, must be gated).
      • Then there is an MDT discussion. Ideally all done in a matter of weeks.
      • CTCA has high sensitivity in elderly patients but moderate specificity
      • COE review essential – they can assess frailty, cognition, optimise comorbidities, and help develop an exit plan if things don’t work out
      • Complications (<2% major comps, 30-day mortality 1.3% if elective, 3.1% if urgent)
          • Vascular injury (1.4%)
          • Aortic rupture (esp if not sized correctly, or very calcified vessels/valves)
          • Stroke (2%)
          • Para valvular leak
          • Damaging conduction system requiring a PPM (7%)
          • Major bleeding (1%)
          • Failure to improve AS very much, or quick recurrence of severe AS (1.8%)
          • Recurrence can happen 6 months or so later due to HALT (hypoattenuating leaflet thickening). Manage with warfarin, gradient will get better (not TAVI failure per say)
      • Afterwards
          • Durability comparable to tissue aortic valve
          • Consider long term aspirin (or clopidogrel) afterwards (unless anticoagulated, then not required). Don’t worry about holding these if need a procedure (not as vital to continue unlike cardiac stents)
          • Check valve gradient afterwards
  • Balloon valvuloplasty
      • Only done in extremis, as a bridge to TAVI or valve replacement (eg if require urgent non cardiac surgery).
  • Surgical valve replacement
      • A good option for younger patients
      • Also useful if iliofemoral artery disease precludes TAVI, or in bicuspid aortic valves
      • Higher post op risks of AKI, severe bleeding and AF compared to TAVI (but lower risk of paravalvular leak)
      • Tissue verses metal (metal lasts longer but requires anticoagulation). Metal valves can last 30 years, tissue valves around 10.
      • Generally speaking, aortic metal valves preferred in those aged <60, and aortic tissue valves if aged >65
  • The Ross procedure
      • Replacement of the aortic valve with patient’s own pulmonary valve, combined with donor pulmonary valve replacement.
      • Used in young people. No anticoagulation required.
      • However a more complex procedure and 15% of patients need reintervention within 15 years

Chronic aortic regurgitation

  • Typical clinical features
      • Large volume, collapsing pulse
      • Arterial pulsations in neck
      • Thrusting/hyperkinetic laterally displaced apex beat
      • High pitched early diastolic murmur at left sternal edge and loudest with patient leaning forward and in expiration
      • Occasionally
          • Fingertip capillary bed pulsation
          • Head bobbing
          • Uvular pulsations
          • Pistol shot femorals
          • Austin flint murmur
  • Clinical signs of severity
      • Wider pulse pressure
      • Longer diastolic murmur
      • Austin flint murmur (mid-diastolic low pitched rumble)
      • Displaced apex
      • Systolic pressure in legs>60mm than arms (Hill’s sign)
  • Causes
      • Rheumatic fever (in middle/low-income countries)
      • Bicuspid valve
      • Rarely due to aortic root dilatation, atherosclerosis, VSD, CTD, syphilis, collagen disorders.
      • Acute AR is usually due to IE or aortic dissection
      • In cases of chronic pure severe AR, >50% have a bicuspid valve associated with dilatation of the aorta
  • Assessment
      • Check for imaging features of severe AR
          • Abnormal valve morphology / flail cusp / large coaptation defect
          • Vena contracta >6mm, PHT <200ms, large central jet, holodiastolic flow reversal in descending aorta
          • Quantitative : EROA >30mm2 , R vol >60ml/beat, RF >50% on echo, RF >40% on CMR
          • Bear in mind that hypertension can lead to an overestimation of regurgitant volume
      • Look for clues to mechanism – including aortic diameter. Root dilatation can also determine type of surgery required.
      • Assess for LV damage – this can help determine eligibility for surgery (especially if asymptomatic)
  • Management
      • Give vasodilators like ACE-I and nifedipine
      • AR is a relative contraindication to betablockers – they can increase regurgitation volume by increasing the length of diastole (but can be used after surgery if indicated)
      • Surgery indicated in severe symptomatic AR (unless risk prohibitive) regardless of LV function
      • Refer for intervention if asymptomatic and
          • EF < 50% or
          • LV ESD (end systolic diameter) >50mm or
          • LV ESDI (end systolic diameter index) >25mm/m2 on echo
      • Can now do TAVI for severe AR (but not if acute). Generally used if symptomatic severe AR and ineligible for surgery
      • If aortic dilatation present – assess whether surgery required irrespective of severity of AR (surgery generally recommended if max aortic root or ascending aneurysm diameter is >55mm). May require valve-sparing aortic root replacement
      • If a patient needs a CABG – often do AVR as well if severe AR, irrespective of symptoms. If moderate AR, consider replacement at the same time too
  • Follow up
      • Annually for asymptomatic severe AR (or every 3-6 months if approaching thresholds for surgery, or with progressive LV dilatation.
      • Annual follow up for moderate AR, with echo every 2 years
      • Consider exercise restriction if severe AR and aortic dilatation

Acute Aortic Reguritation

  • Most is caused by IE (rarely by prosthetic valve failure, dissection, trauma or iatrogenic)
  • Decompensation can be rapid and mortality high
  • Emergency surgery likely (TAVI not indicated)
  • Can present with collapse, hypotension and can be missed
  • Murmur can be absent (or only Austin Flint)
  • IABP ineffective so resuscitation is hard
  • Echo can help differentiate from chronic AR
  • If premature mitral valve closure best managed on ITU, and if diastolic MR also present, emergency surgery in 4 hours is indicated

 

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