Silent mitral stenosis
When the mitral diastolic murmur is not audible despite the presence of severe mitral stenosis, it is called silent mitral stenosis.
Mechanism of silent mitral stenosis
Right ventricular hypertrophy causes clockwise rotation of the heart so that the left ventricle becomes more posterior and the apex is formed by the right ventricle. Hence the mitral diastolic murmur is not heard at the apex. Another reason is the decreased flow across the mitral valve in very severe mitral stenosis diminishing the intensity of the murmur. The decreased mobility of the thick and calcified mitral leaflets in severe calcific mitral stenosis may contribute to the decrease in intensity of the mitral diastolic murmur.
Mechanism of loud first heart sound in mitral stenosis
In severe mitral stenosis, due to elevated left atrial pressure, the closure of the mitral valve is delayed and occurs at a time when the dp/dt of the ventricular pressure tracing is higher. This enhances the intensity of the mitral component of first heart sound. The elevated left atrial pressure also keeps the mitral valve in a more open position at the onset of systole. This would mean a greater closing excursion of the mitral valve, increasing the intensity of the first heart sound. In calcific mitral stenosis, the decreased mobility of the valve leaflets may decrease the intensity of the first heart sound.
Mechanism of wide fixed split in atrial septal defect.
The P2 (pulmonary component of second heart sound) does not move with respiration in atrial septal defect (ASD) because the right ventricular output and pulmonary hang out interval does not change with respiration. Pulmonary hang out interval does not change because the pulmonary circulation is already overloaded by the left to right shunt. Right ventricular output does not change because the change in left to right shunt with respiration balances the change in right ventricular inflow due to change in venous return. In inspiration, when the venous return increases, left to right shunt across the atrial septal defect decreases and vice versa. The split is wide in ASD because the right ventricular emptying is more prolonged due to the volume overload.
Tachypnoea
Tachypnoea is an increase in the rate of respiration.
Hyperpnoea
Hyperpnoea is an increase in depth and rate of respiration.
Hyperventilation
Hyperventilation is an increase in depth and rate of respiration inappropriate to the metabolic need. It can be either or voluntary as in conversion disorders or neurogenic as in central neurogenic hyperventilation.
Pointers of associated mitral valve obstruction in severe aortic regurgitation
Long duration of symptoms, paroxysmal nocturnal dyspnoea, hemptysis and atrial fibrillation are pointers to associated mitral stenosis in a case of severe aortic regurgitation. A loud first heart sound and opening snap will favour associated mitral stenosis than Austin Flint murmur in aortic regurgitation. Orthopnoea can occur in severe mitral stenosis as well as decompensated aortic regurgitation.
What is the most important diagnostic feature of mitral regurgitation?
Apical location of the murmur is the most important feature of mitral regurgitation. Second is the blowing quality in chronic mitral regurgitation (MR). Third is the timing – chronic rheumatic MR is pansystolic while that in mitral valve prolapse can be mid or late systolic. Conduction pattern is variable depending on the etiology. Classical rheumatic MR is conducted to the axilla and back, while that of papillary muscle dysfunction is conducted medially to the base of the heart.