Parameter
Goal
Comment
Preload
↑
- LV hypertrophied and compliance is poor
- Optimize preload to enable adequate filling of the LV (guided by cardiac output monitoring)
- Vasodilators (particularly venodilators such as GTN) should be avoided
Rate & Rhythm
↓
- Avoid tachycardia (Aim 50-70)
- Reduces diastolic filling time
- Reduces the time for coronary perfusion, therefore worsening ischaemia
- Increases oxygen demand
- Avoid excessive bradycardia
- This results in a reduced cardiac output as the stiff ventricle cannot increase the stroke volume to compensate.
- The increase in ventricular filling due to longer diastole also increases ventricular wall tension further reducing coronary perfusion.
Rhythm
Sinus
- Maintain sinus rhythm - vital
- Atrial contraction is important for LV filling
- Up to 40 % of filling in diastole is due to atrial contraction (normally only 15–20 %)
- AF and nodal rhythms are therefore poorly tolerated in these patients
- Arrhythmias need aggressive treatment
Contractility
Maintain
- Maintain myocardial contractility:
- Avoid B-blockers or myocardial ischaemia
- Increasing myocardial drive does not improve cardiac output and can precipitate ischaemia through increased oxygen consumption
Afterload
↑
- Avoiding hypotension is critical - maintain a high-normal diastolic
- Diastolic pressure must be maintained ensure filling of coronary arteries - require larger than usual due to hypertrophied LV
- Any hypotension needs to be treated early to avoid spiral of further reductions in coronary perfusion, causing myocardial depression and potentially leading to cardiac arrest
- CPR is generally ineffective in these patients unless internal massage can be performed
- Afterload essentially fixed below a certain limit due to valvular obstruction:
- Reducing SVR has no impact on ejection of blood from the LV, as the obstruction to flow is due to the stenosed valve leading to a fixed cardiac output