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Archive for the ‘Hemodynamics’ Category

Mitral regurgitation is expected to occur only in systole during  left ventricular contraction. In rare pathological states , if   LV pressure exceeds the mean LA pressure at any point in diastole , small  puffs of regurgitation into LA can occur.The genesis of this MR and its  hemodynamic  significance has generated much interest .

Causes

  1. Aortic regurgitation -Severe . (Occurs mainly in acute AR or chronic AR with decompensated LV )
  2. AV blocks (especially complete AV block )
  3. Any cardiomyopathy with severely elevated LV diastolic pressures

Mechanism

No single mechanism is  responsible.

  • Common hemodynamic denominator  is transient cross over of LV pressure over and above LA pressure curve .
  • This tends to happen often soon after the atria contracts  specifically so , if the atrial contraction is not followed by a QRS complex as in heart block .
  • The fact that its reported even in the presence of atrial fibrillation (As in some cardiomyopathy ) atrial mechanism is not exclusive.
  • In Aortic regurgitation the mechanism is  different (More of  volume dependent ,  Read below )

diastolic mitral regurgitation animationTiming of  diastolic MR

It occurs in later part of diastole as it takes a time lapse for raising LV diastolic pressure  to cross the LAP and generate a reversed ventricular gradient.

Will there be a clinical evidence for this MR ?

Its silent in most cases .Some patients with complete heart block may  generate  mid diastolic murmur . (Rytand AHJ 1946) .Retrospectively this could be due to diastolic MR

Is there a link between Austin flint murmur and diastolic MR ?

Many researchers believe the generation of diastolic murmur in severe AR is attributable to premature closure of mitral valve and the poorly compliant LV  is not able to accommodate the leaking blood and it tends to regurgitate into  LA  through partially closed mitral valve in diastole (Ochaya  S,  Am Heart J. 74 1967:161-169)

Echo features

  • Doppler flow signal in mitral inflow is diagnostic
  • Color M-mode is ideal to map  diastolic MR.

Cath correlation

Wong has demonstrated this phenomenon by direct hemodynamic  recording in 4 patients

Further research

While the field of diastology is growing , still we are not clear how significant this MR in clinical diastolic dysfunction and acute LV failure that results in flash  edema.

Reference

5.Diastolic atrioventricular valve closure and regurgitation following atrial contraction: their relation to timing of atrial contraction.Okamoto M1, Tsubokura T, Kajiyama GClin Cardiol. 1989 Mar;12(3):149-53.
7. An auricular diastolic murmur with heart block in elderly patients.Rytand  DA; Am Heart J. 32 1946:578-598.
8. Late diastolic mitral regurgitation secondary to aortic regurgitation its relationship to the Austin-Flint murmur.ochaya  S, Igarashi  M, Schaffer  AB; Am Heart J. 74 1967:161-169

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