A 78-year-old female is admitted to ICU following aortic valve replacement for severe aortic stenosis.Her co-morbidities include ischaemic heart disease, peripheral vascular disease, hypertension, type 2 diabetes, emphysema and chronic kidney disease.

The operation was prolonged and difficult requiring repair of a right ventricular injury and emergency coronary artery bypass graft. The patient required adrenaline, noradrenaline and an intra-aortic balloon pump to separate from cardiopulmonary bypass.

At 4 hours post-operatively, she becomes progressively more hypotensive with increasing noradrenaline doses. List the potential causes for her shock state.       (60% marks)

With respect to severe aortic stenosis, list the available alternatives to open valve replacement, with the respective advantages and disadvantages. (40% marks)

[Click here to toggle visibility of the answers]

College answer

a)

Hypovolaemic • Bleeding

Cardiogenic • Acute MI • Graft obstruction • Diastolic dysfunction • RV failure • Pacing problem • Pulmonary hypertension

Distributive • Long bypass time • Occult sepsis (e.g. GI tract ischaemia) • Relative adrenal dysfunction • Nutritional deficiency

Obstructive • Pericardial tamponade • Left Ventricular Outflow Tract Obstruction • Prosthetic valve obstruction • Tension Pneumothorax (may be loculated due to previous surgery) • IABP failure / dyssynchrony/ malposition

Combination of above e.g. Aortic dissection

b)

Medical management only +/- palliation. Considered if prognosis of comorbidities is worse than natural history of AS. Avoids risks of surgery.

Medical management + balloon valvuloplasty. BAV may provide some symptomatic benefit albeit at the risk of complications from femoral vessels/ annular rupture. May also be useful diagnostically to see if dyspnoea improves.

TAVI – femoral access probably unlikely to be possible due to PVD, transapical or transoartic much higher risk but possible. Less invasive.

Discussion

When you fix an aortic stenosis and it all goes well, frequently the patient will become hypertensive instead,  which is clearly not what we see here. The table of potenstial reasons for shock is offered below, and it is similar to what is offered in the chapter about approaching the haemodynamically unstable post-pump patient

Causes of cardiovascular instability after bypass

Immediately recognisable on direct inspection

  • Artifactual - check your lines, zero to recalibrate
  • Anaphylaxis
  • Arrhythmia, eg. AF
  • Valve failure - eg. mitral regurgitation of sudden onset

Immediately recognisable on routine investigations

  • Myocardial ischaemia should not be left unrecognized
  • Pneumothorax or tension pneumothorax
  • Cardiac tamponade
  • Haemorrhage
  • LV outflow tract obstruction

Excluded by inspection and investigations

  • Rewarming-related vasodilation
  • Excessive sedation with propofol
  • Post-bypass vasoplegia
  • Post-bypass myocardial depression

In light of the offered scenario, several of these possibilities are more likely than the others:

  • Vasoplegic shock (long by pass time, more circuit exposure, and with the background history of hypertension one might confabulate that she might have been on an ACE-inhibitor chronically).
  • Cardiac tamponade (due to right ventricular injury)
  • Right heart failure due to cardiotomy 
  • Post-bypass myocardial depression (coronary arteries need to be grafted as an emergency procedure, and the background contains enough ischaemic heart disease; on top of that the college tell us that an IABP was required to wean off bypass)
  • Myocardial infarction post-operatively
  • Tension pneumothorax (the history of emphysema makes ruptured bullae more likely)

Alternatives to open valve surgery can be listed, but the "advantages/disadvantages" question is an opening to a tabulated response. The best literature reference for this would probably be something like the UpToDate article, which gives you a choice between surgery, TAVI and conservative medical therapy. The 2016 article by Fattouch et al is also a good overview (and free).

Alternatives to Open-Heart Valve Surgery

Alternative

Advantages

Disadvantages

Transfemoral
transcatheter aortic valve implantation

  • Shorter duration of hospital stay than sternotomy
  • Better pain relief
  • Comparable outcomes in matched populations (Cao et al, 2013)
  • Requires an experienced centre
  • Requires good quality femoral vessels
  • Still fairly invasive
  • Periprocedural CPR is a commonplace occurrence 
  • Unsuitable in some populations, eg. HOCM or if there is unrevascularised coronary artery disease
  • Evidence in support of TAVI is poor among good surgical candidates

Transapical transcatheter aortic valve implantation 

  • Possible even when femoral vessels are heavily calcified
  • Similar mortality rate to transfemoral approach
  • Better placement; less paravalvular leak than transfemoral (Murashita et al, 2016)
  • More invasive
  • Risk of tamponade and VT
  • No advantage in terms of mortality of ejection fraction

Balloon valvuloplasty

  • Smaller catheter required than for TAVI (i.e. able to gain access through 
  • Older technique: more experience
  • Less invasive than TAVI
  • Can reduce the risk of subsequent TAVI or AVR by improving haemodynamics (i.e. as a "bridge")
  • Potential of stroke is greatest
  • Stenosis resolves, but now regurgitation develops
  • May be poorly tolerated haemodynamically
  • Inevitably leads to restenosis (van den Brand, 1992)

Conservative management

  • Non-invasive
  • May be well suited to patients with low activity levels (eg. nursing home patients)
  • Survival is poor: 69% at one year
  • Progression of the disease is unaffected
  • Symptom control is likely going to be poor

References

Frederick A. Hensley, Jr., M.D., Donald E. Martin, M.D.,  Glenn P. Gravlee, M.D. A Practical Approach to Cardiac Anaesthesia, 3rd ed. Sibylle A. Ruesch and Jerrold H. Levy. CHAPTER 9. The Postcardiopulmonary Bypass Period: A Systems Approach. 2003 by LIPPINCOTT WILLIAMS & WILKINS

André, Arthur C. St, and Anthony DelRossi. "Hemodynamic management of patients in the first 24 hours after cardiac surgery." Critical care medicine 33.9 (2005): 2082-2093.

Rodés-Cabau, Josep, et al. "Transcatheter aortic valve implantation for the treatment of severe symptomatic aortic stenosis in patients at very high or prohibitive surgical risk: acute and late outcomes of the multicenter Canadian experience.Journal of the American College of Cardiology 55.11 (2010): 1080-1090.

Alkhouli, Mohamad, et al. "Morbidity and Mortality Associated With Balloon Aortic Valvuloplasty." Circulation: Cardiovascular Interventions 10.5 (2017): e004481.

Linke, Axel, et al. "Treatment of aortic stenosis with a self-expanding transcatheter valve: the International Multi-centre ADVANCE Study."European heart journal 35.38 (2014): 2672-2684.

Schymik, Gerhard, et al. "Long-term results of transapical versus transfemoral TAVI in a real world population of 1000 patients with severe symptomatic aortic stenosis.Circulation: Cardiovascular Interventions 8.1 (2015): e000761.

Cao, Christopher, et al. "Systematic review and meta-analysis of transcatheter aortic valve implantation versus surgical aortic valve replacement for severe aortic stenosis.Annals of cardiothoracic surgery 2.1 (2013): 10-23.

Murashita, Takashi, et al. "Clinical Outcomes After Transapical and Transfemoral Transcatheter Aortic Valve Insertion: An Evolving Experience."The Annals of thoracic surgery 102.1 (2016): 56-61.

Keeble, Thomas R., et al. "Percutaneous balloon aortic valvuloplasty in the era of transcatheter aortic valve implantation: a narrative review." Open Heart3.2 (2016): e000421.

van den Brand, Marcel, et al. "Histological changes in the aortic valve after balloon dilatation: evidence for a delayed healing process." British heart journal 67.6 (1992): 445-449.

Fattouch, Khalil, Sebastiano Castrovinci, and Patrizia Carità. "Aortic valve stenosis: treatments options in elderly high-risk patients." Journal of geriatric cardiology: JGC 13.6 (2016): 473-474.