Short case Flashcards
Mitral Stenosis
Exam
- small volume (severe), AF
- JVP - loss of A wave with sustained V wave
- tapping apex, palpable P2, RV heave
- S1 - loud, apex + expiration
- S2 - loud P2
- Added - opening snap
- mid diastolic at apex + left lateral
- TR + PR
- basal creps, ascites, edema
DDx - rheumatic, congenital, calcific, RA/SLE
Investigations
Explain the cause of the first heart sound?
It corresponds to the closure of the atrioventricular valves. The exact cause is debated, but is thought to occur due to abrupt cessation of moving blood columns secondary to the closure of the valves, and the rapid deceleration which causes the chordae tendinae, papillary muscles and ventricles to vibrate
The intensity of S1 is due to the force of ventricular contraction and also the position of the atrioventricular valves at the onset of ventricular systole
What are the causes of a loud first heart sound?
Due to rapid ventricular contraction, as occurs with fever and other sympathetic stimulation such as SABA, thyrotoxicosis
Delayed closure of the AV valves. After atrial systole and when the ventricles begin to contract, the AV valves are held wider apart, therefore it takes longer for them to close, and when they do finally oppose each other to close, they shut at a rapid rate of deceleration because the ventricle has had enough time to generate a vigorous contraction
1) Prolapsed mitral valve because the mitral valves that prolapse take longer to tense up and thus close at a time when ventricular contraction is more forceful
2) Mitral stenosis because the pressure gradient of the LA - LV keeps the valves apart for longer and hence they take longer to close
3) Short PR interval: Ventricular systole occurs shortly after atrial systole.
4) Atrial myxoma: the tumour falls into the mitral orifice and hence there is delayed closure of the valve
What are the causes of a soft first heart sound
1) Poor ventricular contraction due to cardiomyopathy
2) LBBB
3)Prolonged PR interval: The atrial systole has occured and the atria is relaxing whilst the ventricle is filling, and when ventricular systole occurs, the mitral valve is more closely apposed. Therefore there is not enough time for the contraction to build up in strength to cause a forceful closure of the valve
4) Acute aortic regurgitation: The regurgitant volume fills the ventricle in diastole. When it is acute (ie infective endocarditis) there is not enough time for the ventricle to remodel itself in order to become more compliant. Subsequently the LV diastolic pressures increase and may match LA pressures, causing opposition of the mitral valve leaflets
Describe the finding of the opening snap in a patient with mitral stenosis
The opening snap occurs just prior to the diastolic rumbling murmur of mitral stenosis
The mechanism is thought to relate to the mitral valve billowing out into the LV due to the pressure gradient created by the stenosis, and as the maximum angles of movement are reached, the leaflets of the mitral valve rapidly decelerate creating the sound.
It is heard best at the apex, or between the apex and the left lower sternal border
What is the reason behind the inverse correlation of severity of mitral stenosis and the length of S2-OS
The tighter the stenosis the greater is the atrial force required to overcome the stenosis
Therefore the mitral valve opens earlier in diastole
What is an important differential for MS?
left atrial myxoma, which in stead of an opening snap causes a tumour plop
This may be seen in TTE
What is the medical management of MS?
Medical therapy does not alter natural history of lesion and does not delay surgery
Medical treatment is directed toward alleviating pulmonary congestion with diuretics, treating atrial fibrillation, and anti-coagulating patients who are at increased risk of arterial embolic events.
Tachycardia is typically poorly tolerated in patients with MS and can lead to an acute deterioration as diastolic filling time may be inadequate. In particular, heart rate control can be beneficial in patients with MS and atrial fibrillation and fast ventricular response
However, heart rate control may also be considered for patients with MS in normal sinus rhythm and symptoms associated with exercise
Anticoagulation with warfarin is indicated to prevent thromboembolism when atrial fibrillation is present, if there is a prior history of thromboembolism, or if a thrombus is detected in the left atrium.
Anticoagulation may also be considered if the left atrium is markedly dilated (5.0-5.5 mm) or if there is spontaneous contrast on echocardiography (Class IIb).
Long-term secondary prophylaxis is recommended for all patients with a history of rheumatic fever, rheumatic carditis or rheumatic valve disease because recurrent carditis can occur at a higher frequency after previous carditis and this can cause acceleration of the lesions natural history.
What are the surgical options for treating MS?
1) percutaneous mitral balloon commissurotomy
- catheter-based technique in which a balloon is inflated across the stenotic valve to split the fused commissures and increase the valve area
comparable with those achieved with open mitral commissurotomy
need favourable valve morphology - Severe valve calcification and/or significant thickening/calcification of the subvalvular apparatus on echocardiography before PMBC is associated with a higher complication rate and a greater risk of recurrence.
not to be done if there is LA thrombus or there is MR
Class 1/ II indications:
severe symptomatic MS (<1.5cm sq valve area)
less severe symptomatic MS (valve area > 1.5cm sq) but haemodynamically significant MS on exercise
asymptomatic MS (<1cm sq valve area)
2)open mitral commissurotomy
- Surgical mitral commissurotomy (either open or closed) may be carried out through a median sternotomy or left thoracotomy incision
3) mitral valve replacement
