Rheumatic heart disease – mitral stenosis

Rheumatic heart disease is the most important cause of mitral stenosis. Other causes of mitral stenosis like congenital mitral stenosis due to parachute mitral valve are extremely uncommon. So for practical purposes, mitral stenosis can be taken to be of rheumatic etiology, especially in a developing country.

Normal mitral valve area is about 5 sq cm. When the area falls below 2 sq cm it is considered as mitral stenosis. The commonest cause of mitral stenosis is as sequelae of rheumatic carditis.

Grading of severity of mitral stenosis by valve area

Mild mitral stenosis: Mitral valve area 1.5 – 2.0 sq cm

Moderate mitral stenosis: Mitral valve area 1.0 – 1.5 sq cm

Severe mitral stenosis: Mitral valve area <1.0 sq cm

Symptoms of mitral stenosis

The predominant symptom of mitral stenosis is exertional dyspnoea. Paroxysmal nocturnal dyspnea is a classical symptom of mitral stenosis which tends to occur earlier in the natural history and may disappear later on. Palpitation can occur due to arrhythmias in mitral stenosis. A patient with severe mitral stenosis may also present with acute pulmonary edema, usually in the presence of an intercurrent infection or arrhythmia. Rarely a patient may present with an embolic episode as the first manifestation of mitral stenosis. Embolisation secondary to left atrial thrombi is more occur with associated atrial fibrillation in mitral stenosis.

Juvenile mitral stenosis

The term juvenile mitral stenosis was coined by Prof. SB. Roy for patients with onset of symptoms of mitral stenosis before the age of 20 years. It is more common in the developing countries and the relatively underprivileged regions of developed countries. More frequent and sever rheumatic activity is thought to be the reason of earlier onset of features of mitral stenosis. They tend to have a more rapid course marked by severe pulmonary hypertension and a higher chance for restenosis after successful mitral valvotomy.

What are the situations in which a person with significant mitral stenosis become less symptomatic?

This occurs when there is associated tricuspid stenosis, pulmonary hypertension or atrial septal defect. Tricuspid stenois and pulmonary hypertension decreases the volume of blood reaching the pulmonary capillaries and reduces the chance for transudation. Atrial sepatl defect decompresses the left atrium and reduces pulmonary venous congestion.

P mitrale and right ventricular hypertrophy

P mitrale and right ventricular hypertrophy

P mitrale of left atrial enlargement is manifest as broad notched (M shaped) p wave in lead II, classically seen in mitral stenosis. The broad negative P wave in V1 is also indicative of left atrial overload. qR pattern in V1 with T wave inversions in anterior leads is suggestive of right ventricular hypertrophy. The axis appears to be in the north-west or indeterminate region, which could be a manifestation of extreme right axis deviation due to right ventricular hypertrophy as a consequence of pulmonary hypertension in mitral stenosis. T waves in V5 and V6 are unusually tall. Lead II rhythm strip at the bottom of the tracing documents a normal sinus rhythm, which can any time degenerate into atrial fibrillation in this case with gross left atrial overload. Such degeneration into atrial fibrillation can cause rapid initial deterioration in clinical status, sometimes presenting as pulmonary edema. Patients with severe pulmonary hypertension due to obliteration of pulmonary vascular bed can be sometimes be protected from pulmonary edema as the right ventricular output is restricted to certain extend, which could also be due to right ventricular dysfunction and associated tricuspid regurgitation.

Atrial flutter in mitral stenosis

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Atrial flutter is less common than atrial fibrillation in mitral stenosis. In this ECG the flutter waves are seen well in inferior leads and V1 as typical saw tooth waves while it is also seen in other leads. Such an organised flutter is rare in mitral stenosis. In most cases of mitral stenosis, the coarse fibrillary waves resemble flutter waves in some leads, but not in others. Such impure rhythms are sometimes called flutter-fibrillation, flitter or fib-flutter. In those cases the waves are irregular. In this ECG the waves are regular, suggesting true atrial flutter. The conduction ratio is varying so that the ventricular rate is irregular and resembling atrial fibrillation. The large atria in this case (both left and right atria as there is severe pulmonary arterial hypertension secondary to severe mitral stenosis) helps the maintenance of this flutter circuit.

Mitral stenosis – X-ray chest PA view

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The cardiac size is normal, but the left atrial appendage is prominent (LAA in the annotated image below). Main pulmonary artery (MPA) segement is just outside the left border, indicating pulmonary hypertension. The enlargement of left pulmonary artery (LPA) and right pulmonary artery (RPA) are just modest, if at all. The horizontal fissure is visible, indicating collection of edema fluid in the fissure. The aortic knuckle (Ao) is also seen well. There is suggestion of Kerley B lines near the costophrenic angles, but not typical.

Mitral stenosis – straightening of left border

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Mitral stenosis – straightening of left border on X-ray chest PA view. The uppermost portion on the left cardiac border is the aortic knuckle. The next slight bulging is the main pulmonary artery and the left atrial appendage is seen below that. The latter two regions are usually concave and the obliteration of the concavity contributes to the “straightening of left border”.

M-mode echocardiogram in mitral stenosis

M-mode echocardiogram in mitral stenosis

M-mode echocardiogram in mitral stenosis showing the flat EF slope and paradoxical motion of posterior mitral leaflet. Normally the anterior mitral leaflet shows and M shaped anterior movement and posterior mitral leaflet shows a smaller W shaped posterior movement pattern. The upper panel shows the doming of anterior mitral leaflet in diastole. The doming of the anterior mitral leaflet and the paradoxical anterior motion of the posterior mitral leaflet are the manifestations of commissural fusion seen in rheumatic mitral stenosis. The upper panel also shows a grossly dilated left atrium. LVIDs: left ventricular internal diameter, systolic; LVPWd: left ventricular posterior wall, diastolic; LVIDd: left ventricular internal diameter, diastolic; IVSd: interventricular septum, diastolic; EDV: end diastolic volume; FS: fractional shortening; ESV: end systolic volume; EF: ejection fraction. The difference between end diastolic and end systolic volume gives the stroke volume. Stroke volume divided by end diastolic volume gives the ejection fraction. Left ventricular ejection fraction is usually normal in mitral stenosis. IVS/LVPW ratio is abnormal in asymmetric septal hypertrophy of hypertrophic cardiomyopathy. It can also be abnormal if the septum or the left ventricular posterior walls are thinned out due to myocardial infarction.

Rheumatic mitral stenosis – echocardiogram in parasternal long axis view

Rheumatic mitral stenosis – echocardiogram in PLAX view

Mitral valve is the most commonly involved valve in rheumatic heart disease. According to Paul Wood, the involvement of the valves in rheumatic heart disease is depending on the hemodynamic load on the valve. The mitral valve faces the maximum load as it withstands the contractile force of the left ventricle during systole. The next highest load is on the aortic valve, the load on which is the aortic diastolic pressure.

Rheumatic mitral valve involvement is characterised by commissural fusion. This causes the valve leaflets to move together in the same direction during diastole. Normally the anterior mitral leaflet (AML) moves anteriorly during the opening motion in diastole and the posterior leaflet moves posteriorly. Due to commissural fusion the posterior leaflet moves anteriorly along with the anterior mitral leaflet in diastole. This is a paradoxical movement of the posterior mitral leaflet (PML). The movement of the anterior mitral leaflet is also restricted, producing a doming or hockey stick like appearance in diastole. The diastolic separation between the leaflets is also reduced, obstructing the forward flow across the valve. In cross sectional imaging the mitral valve has a fish mouth appearance, with thickening of both leaflets and fusion of anterolateral and posteromedial commissures.

The image above illustrates all the feature in the parasternal long axis view (PLAX) like doming of AML, anterior displacement of the PML and reduced leaflet separation in diastole. The dilated left atrium (LA) secondary to the mitral valve obstruction is also evident. The circular echolucency behind the left atrium is the cross section of the descending aorta. In live imaging it will seen as pulsatile, increasing dimensions in systole and reducing in diastole. Ascending aorta (Ao) is seen anterior to the left atrium and is of normal size. Aortic valve is in a closed position and is seen only faintly as it is not thickened. Left ventricular cavity is seen distal to the mitral valve (LV) and the right ventricle (RV) is seen above, with the interventricular septum in between (not marked). The apex of the triangular image is the position of the transducer, which has been kept in the left parasternal region, on the anterior chest wall, just anterior to the right ventricle.

Mitral stenosis on parasternal short axis view

Rheumatic mitral stenosis in parasternal short axis view

Parasternal short axis view showing mitral valve in cross section (dotted outline). The valve leaflets are thickened and the commissures are fused. The cut is slightly oblique as a good cut should appear circular. It is often difficult to get a good circular outline of the mitral valve to varying anatomical features of the chambers and cardiac position. Ideally the smallest full circle should be taken to planimeter the valve area. If it is not a full circle, the subvalvar pathology may be measured as the valve orifice. If the smallest full circle is not taken, it will be the valve proximal to the severest stenosis (valve belly). The mitral valve cross section in mitral stenosis has a fish mouth appearance. The left ventricular cavity surrounds the mitral orifice, which in turn is surrounded by the left ventricular wall. Interventricular septum with the right ventricle beyond is seen towards the upper left corner. MVO: mitral valve orifice; IVS: interventricular septum; LV: left ventricle; RV: right ventricle.

Rheumatic mitral stenosis in parasternal short axis view – annotated

More two dimensional (2D) and M mode echocardiograms in mitral stenosis

Mitral stenosis – parasternal long axis view showing dilated left atrium (LA), thickened and paraxodically moving (anteriorly in diastole) posterior mitral leaflet (PML) and doming anterior mitral leaflet (AL). The movement abnormalities of the mitral leaflets are due to commissural fusion. RV: right ventricle; AO: aorta; LV: left ventricle; PAS LAX: parasternal long axis.

Mitral stenosis – parasternal short axis view showing the “fish mouth appearance” of the mitral orifice (M) in the short axis view of the left ventricle (LV). Mitral valve area can be measured in this view by planimetry using the online calipers. RV: right ventricle; PAS SAX: parasternal short axis.

Mitral stenosis – M mode echocardiogram showing the paradoxical anterior motion of posterior mitral leaflet (PML) in diastole with reduced separation of the two leaflets. AML (anterior mitral leaflet) has certain points marked in its movement: C, D,E and F. The EF slope is reduced in mitral stenosis – it becomes almost flat in severe mitral stenosis. CD is the closed position of the mitral leaflets in systole and DE is the opening excursion of the anterior mitral leaflet.

Mitral stenosis – pulmonary hypertension as evidenced by the flat EF slope of the pulmonary valve M mode echocardiogram and the shallow a wave (arrow). A mid systolic notch may also appear in severe pulmonary hypertension. When Doppler echo was not available, M mode of the pulmonary valve was an important tool to assess pulmonary hypertension. Now with Doppler echo, the right ventricular systolic pressure (indirectly the pulmonary artery systolic pressure in the absence of pulmonary stenosis) can be estimated from the velocity of the tricuspid regurgitation jet.

Mitral gradient by CW Doppler in mitral stenosis

Mitral gradient by CW Doppler in mitral stenosis

Mitral gradient by CW Doppler in mitral stenosis demonstrating the maximum gradient (Max PG) of 31 mm Hg and mean gradient (Mean PG) of 18 mm Hg. The Doppler tracing is obtained by aligning the Doppler cursor along the trans mitral jet during diastole in the apical four chamber view. The outline of the tracing is sketched out manually to measure the velocities and gradient, which is calculated by the software package in the echocardiograph. Pressure half time (P1/2t) of the initial slope is calculated as 377 milliseconds. VTI: velocity time intergral; MVA: mitral valve area. Here the mitral valve area calculated by the pressure half time method [MVA(P1/2t)] is 0.58 square cm, indicating critical mitral stenosis. The large left atrium seen in the upper panel is also consistent with severe mitral stenosis. Vmax of 282 cm/s is the peak velocity of the initial peak (E) and the Vmax of 278 cm/s is the peak velocity of the second peak (A). Even though the A wave is blunted in mitral stenosis in the M-mode echocardiogram, the A of Doppler tracing is not. Slope of 219 cm/s is the slope following the initial E, which is used to estimate mitral valve area. Pressure half time is calculated from the peak velocity and the slope by the software package. The mitral valve area is derived from the pressure half time by dividing 220 by pressure half time. This is because a pressure half time of 220 ms corresponds to a mitral valve area of 1 square cm. Continuous wave Doppler is needed because the velocities are beyond the usual range for pulsed Doppler. If pulsed Doppler is used, the signals will get aliased as the velocity is beyond the Nyquist limit of the pulsed Doppler system.

Mitral valvotomy balloon

Proximal end of the mitral valvotomy balloon displays the balloon size (24 in this case). The size of the balloon required for an individual is calculated from the height of the person. Height in cm is divided by ten and ten is added to the quotient to get the size of the balloon needed in mm. 24 mm, 26 mm and 28 mm are the usual sizes being used. Each balloon can be used for a range of inflations and the size is adjusted by changing the volume of dilute contrast to be used for balloon inflation. The resultant size is checked before introduction of the balloon into the vascular system. Oversizing can increase the chance of mitral regurgitation. Undersizing may reduce the likelihood of good splittting of the fused commissures of the mitral valve. Balloon mitral valvotomy (BMV) is also called percutaneous transmitral commisurotomy (PTMC).

Snap shots of balloon mitral valvotomy fluroscopic images

Sreen shot of the fluroscopic image showing the balloon mitral valvotomy (BMV) balloon across the interatrial septum in the left atrium (LA). The left atrial pigtail guide wire is also protruding out of the deflated balloon in the left atrium. The pigtail wire prevents the balloon tip from injuring the left atrial roof while passing across the interatrial septum into the left atrium.

This screen shot shows the deflated balloon in the left ventricle (LV). The guide wire has been removed. The stillet which was introduced prior to entry into the left ventricle to curve the balloon assembly to facilitate LV entry has been partially withdrawn to minimise trauma to the left ventricle. Presence of the stillet will increase the stiffness of the assembly and increase the trauma to the left ventricle in systole while the balloon is in the left ventricle.

Initial partial inflation of the balloon causes the distal half of the dumb bell shaped BMV balloon to expand first. The distal half is tugged against the mitral valve by pulling back the shaft to ensure correct position for inflation. During proper tugging the arterial pressure tracing will show a dip due to obstruction to LV inflow.

Once the postion across the mitral valve is sure, the balloon is fully inflated to produce splitting of the fused commissures and release of the mitral valve obstruction. During full inflation the arterial pressure drops to zero and if the inflation is prolonged, the subject may feel giddiness.

After full inflation of the balloon, once the commissures have given way, the inflated balloon usually slips back into the left atrium. The balloon is rapidly deflated to avoid prolonged obstruction to the LV inflow. The stillet is removed and the left atrial pressure checked to see the effectiveness of the dilatation in terms of reduction of left atrial pressure. The pigtail catheter from the aorta which was used to guide the septal puncture can be introduced back into the left ventricle to measure the left ventricular diastolic pressure and thus calculate the transmitral gradient. Elevation of the left ventricular end diastolic pressure or undue prominence of left atrial v wave must make one suspect significant mitral regurgitation following mitral valvotomy.

Tips for balloon mitral valvotomy

Precautions during balloon dilatation of the mitral valve
First the balloon has to be introduced smoothly upto the apex and should be able to slide back and forth easily. While inflating the distal half of the balloon, if there are multiple indentations, the balloon may be going across the chordae and should not be inflated further. If it is expanding as one part of the dump bell, it can be pulled back to the mitral orifice and further inflation will expand the other half of the dump bell in the left atrium, with the waist of the balloon across the mitral valve. Full inflation of the balloon will produce good dilatation of the mitral valve.

Site of inter atrial septal puncture for balloon mitral valvotomy
Site of puncture is the region of the fossa ovalis, which can be identified as the third forward dip of the Mullin’s sheath while withdrawing from the superior vena cava into the right atrium. It should be midway between parts of the pigtail catheter in the ascending aorta and descending aorta in the transverse plane as seen in RAO view and one space below the pigtail in the vertical plane as seen on LAO view. A lower puncture may be required when the interatrial septum is bulging into the right atrium to have better alignment with with mid line of the mitral valve to facilitate easy entry of the balloon into the left ventricle.

Choosing the size of the balloon for balloon mitral valvotomy
Height of the subject in centimeters is divided by 10 and 10 is added to the quotient to get the diameter of the balloon to be used in millimeters. For example, if the height is 150 cm, it will give a balloon diameter of 25 mm [(150/10 = 15) + 10 = 25] for dilatation of the mitral valve.

Post balloon mitral valvotomy (BMV) echocardiogram

Echocardiogram in rheumatic mitral stenosis (post balloon mitral valvotomy)

Echocardiogram in rheumatic mitral stenosis (post balloon mitral valvotomy) showing the doming of the anterior mitral leaflet (AML) and paradoxical anterior movement of the posterior mitral leaflet (PML) in diastole, indicating partial commissural fusion. Left atrium (LA) is mildly dilated. RV: right ventricle; Ao: aorta; LV: left ventricle

Colour Doppler echocardiogram in parasternal long axis view showing mitral regurgitation (MR)

Mild mitral regurgitation is seen as a mosaic coloured jet into the left atrium in systole. The aortic valve is in the open position (systolic frame). Mitral valve is in the closed position.

Parasternal short axis view in mitral stenosis after balloon mitral valvotomy

Planimetry shows good valve area after a split of the commissures with BMV (balloon mitral valvotomy).

Apical four chamber (4C) view showing the MS jet

MS jet is seen as a mosaic colored jet in diastole, just beyond the mitral valve in the left ventricle. PV: pulmonary vein.

Doppler interrogation of mitral flow in mitral stenosis

Mitral inflow Doppler tracing in mitral stenosis showing fusion of E and W waves with absent diastasis due to the persistent gradient through out diastole. But the gradients are not high in this post BMV situation. Doppler line is such that the mild mitral regurgitation has not been picked up.

Colour Doppler echocardiogram video in rheumatic mitral stenosis, post BMV

Restenosis vs inadequate valvotomy

Sustained improvement in two functional classes for at least six months is needed to establish a successful closed mitral valvotomy by history. This is because of multiple reasons: After a major surgery, activities will be restricted initially and improvement in functional class as a result of surgery cannot be properly assessed. Even a small improvement in valve area will produce marked initial relief of symptoms for a person in functional class III or IV due to critical mitral stenosis. Only when they return to normal activities, will they feel the limitation in activity due to an inadequate valvotomy.

Difference in X-ray chest finding between mitral restenosis after closed mitral valvotomy vs restenosis after balloon mitral valvotomy

Absence of a prominent left atrial appendage shadow

Left atrial appendage is amputated during closed mitral valvotomy as it is an important site for thrombus formation. Hence prominence of left atrial appendage shadow is unlikely in mitral restenosis after closed mitral valvotomy.