87. Valvular heart disease

Question 1

Preoperative evaluation of valvular heart disease

Answer 1

Determine severity of lesion – history, examination and investigations.

Haemodynamic significance – e.g. echocardiogram, cardiac catheterization.

LV function

Degree of end-organ dysfunction – pulmonary, renal, hepatic

Concomitant ischaemic heart disease.

Question 2

What are the principles of anaesthetising a patient with aortic stenosis?

Answer 2

Maintain myocardial oxygen supply (maintain SVR with -agonist).

Maintain normal sinus rhythm.

Maintain heart rate at 60–90 bpm.

Maintain intra-vascular volume.

Appropriate monitoring – arterial BP, ST changes (CMV5), ?PAFC, ?TOE.
Avoid hypotensive drugs, neuro-axial blocks.

‘Slow and tight’.

Question 3

Critical aortic stenosis

Answer 3

Critical aortic stenosis exists when the orifice is less than 0.5–0.7 cm2 (normal is
2.5–3.5 cm2). This correlates with a trans-valvular gradient of >50 mmHg with
a normal cardiac output. Note that a low gradient may indicate LV failure.
In aortic stenosis the left ventricle is hypertrophied (concentric) and poorly
compliant resulting in diastolic dysfunction.

LVH increases myocardial oxygen demand while the supply is decreased as a
result of high ventricular wall pressures compressing intramyocardial coronary
vessels. Aortic diastolic pressure and normal heart rate must be maintained to
promote coronary blood flow

Question 4

Left ventricle

Answer 4

The poorly compliant left ventricle causes elevated LVEDP which impairs
ventricular filling. Patients are therefore very sensitive to changes in
intravascular volume. Filling by atrial contraction is extremely important
(contributes 40% of ventricular filling). Loss of atrial systole may cause heart
failure or hypotension. Avoidance of arrhythmias is essential (consider
immediate cardioversion).
Patients may behave as though they have a fixed stroke volume. Cardiac
output is thus dependent on heart rate. Bradycardia is poorly tolerated.

Question 5

Principles of anaesthesia for aortic incompetence (‘fast and loose’)

Answer 5

Eccentric hypertrophy, dilated left ventricle.

↑Oxygen demand due to dilated ventricle and ↑ work.

GA generally well tolerated as ↓ afterload→↓regurgitation.

Watch diastolic (coronary perfusion pressure) – tends to be low.
Keep HR 80–100.
Avoid bradycardia as ↓ HR→↑LVEDP which may → failure.
Avoid ↑ SVR as →↑ regurgitation.
Dopamine/dobutamine preferable to vasoconstrictors.
Keep the patient ‘fast and loose’.

Question 6

Principles of anaesthesia for mitral incompetence (‘fast and loose’)

Answer 6

Principles of anaesthesia for mitral incompetence (‘fast and loose’)

Eccentric hypertrophy, dilated left ventricle.

Proportion regurgitated depends on LV afterload.

Dilated left atrium.

GA generally well tolerated as ↓ afterload→↓regurgitation.

Keep preload ↓ (keeps LV volume ↓).

Keep HR 80–100.

Avoid bradycardia as→↑regurgitation.

Avoid ↑ SVR as→↑regurgitation.

Keep the patient ‘fast and loose’.