Feature
JAP Volume 7 Issue 1
Table 2: Common causes of aortic stenosis Causes of Aortic Stenosis
Table 1: Prevalance of aotic stenosis in relation to age. Age
Prevalence of ‘aotic sclerosis’
65 – 75 years 75 – 85 years >85 years
20% 35% 48%
Table 3: Indications for TAVI Severe symptomatic AS with one of the following:
• High perioperative surgical risk (e.g. calculated by EuroSCORE >20) • Contraindication to surgery eg. mediastinal radiotherapy
severe kyphoscoliosis • Previous sternotomy and patent coronary graft
1.3% 2.4% 4%
Prevalence of ‘aotic stenosis’
• Calcific aortic valave disease • Congenital aortic stenosis • Rheumatic valve disease
Table 4: Contraindications to TAVI Contraindications to TAVI
• Aortic valve endocarditis • Mechanical aortic valve • Severe mitral regurgitation • Recent myocardial infarction or stroke • Coexisting coronary artery disease requiring bypass graft surgery • Poor left ventricular function with ejection fraction <20% • Left ventricular or artial thrombus • Life expectancy <1 year
Type of anaesthesia The key objective of anaesthetic management is to maintain
haemodynamic stability. The anaesthetic options include general anaesthesia (GA) or local anaesthesia with sedation. Epidural anaesthesia has also been reported.5
Various sedation
regimens have been suggested including the use of remifentanil with or without propofol. Arterial and venous access sites may be infiltrated with local anaesthesia supplemented with regional nerve blocks e.g. iliohypogastric/ilioinguinal nerve blocks (for transfemoral procedures) or superficial cervical plexus blocks (for transaxillary procedures). Local anaesthesia with conscious sedation has recently been shown in some studies to be advantageous over GA in terms of early postoperative recovery and lower incidence of intraoperative haemodynamic instability.6–8
However, GA with tracheal intubation remains
the most commonly employed technique. There are several advantages of performing TAVI under GA as listed below. Standard monitoring (ECG, pulse oximeter, NIBP, airway
gases, airway pressure) along with invasive arterial pressure monitoring is mandatory. Large bore peripheral IV and central venous accesses are recommended. Urinary catheterisation is commonly performed. Continuous temperature monitoring is ideal and warming aids are used to prevent hypothermia, as it could be a long procedure. Anaesthetic goals are similar to those for the management of aortic stenosis. Preload is adequately maintained with intravenous fluids. Sinus rhythm with low/normal heart rate (50-70bpm) should be maintained as tachycardia impairs diastolic filling. Cardiac arrhythmias should be aggressively managed. Vasopressors such as alpha-adrenergic agonists should be used to treat hypotension immediately and maintain coronary perfusion pressure. Maintenance of haemodynamic stability is particularly important following rapid ventricular pacing, as often there is a period of hypotension. This hypotensive period can be prolonged in patients with pre-existing poor left ventricular function. Rarely cardiopulmonary bypass may have to be instituted via femoral arterial and venous access if haemodynamic instability is profound and fails to recover.
Postoperative care The degree of paravalvular regurgitation is evaluated and the
presence of haemopericardium and aortic dissection are ruled out by echocardiography at the end of the procedure. Access wound sites are infiltrated with local anaesthetic. After tracheal extubation, the patient may be transferred to the intensive care unit or a general cardiac ward after a short stay in postanaesthesia care unit depending on patient’s comorbidity and haemodynamic stability during the procedure. In view of the risk of AV block, temporary pacing wires are left in situ for several hours postoperatively. Continuous ECG monitoring is necessary and blood pressure must be monitored regularly. Simple analgesia with paracetamol with or without weak opioids are sufficient following transfemoral TAVI. Transapical TAVI requires multimodal analgesia with patient- controlled IV opioid analgesia and intercostal nerve blocks. Adequate hydration with IV crystalloids should be continued to prevent contrast-induced nephrotoxicity.
Complications Vascular complications
Major vascular complications at femoral access sites may occur and retroperitoneal blood loss may not be immediately apparent. Transapical access complications may result in major blood loss due to the thin friable left ventricular apex in these patients.
Cardiac complications Myocardial ischaemia or infarction may occur as a result of obstruction of the coronary ostia due to displaced native or prosthetic valve leaflets or as a result of embolism of calcific material from the native valve. Atrioventricular conduction block occurs due to mechanical compression of conduction tissue in the small native valve annulus by the large deep-seated valve prosthesis. Recovery from AV block is uncommon if it occurs and hence permanent pacemaker implantation should be planned after a period of temporary pacing. Mild paravalvular aortic regurgitation is observed in almost half of patients post-implantation, but severe regurgitation is reported in only five percent of procedures.9 severe regurgitation may result in haemolytic anaemia, ventricular
Very
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