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|ASD Diameter = 1.41 cm
ASD VTI = 57.3
|TV Diameter = 3.76 cm
TV VTI = 21.7 cm or 12.0
|TR PISA = 0.686 cm
TR VTI = 112 cm
TR Vmax = 2.86 m/sec
|RVOT DIameter = 2.45 cm
RVOT VTI = 24.5 cm
|AV VTI = 19.6 cm
LVOT Diameter = 1.56 cm
In calculating the shunt, the pulmonary valve stroke volume is the Qp (pulmonary flow) and the stroke volume though the AV is the Qs (systemic flow). The Qp is the calculated using the RVOT diameter and the RVOT or PV VTI which calculates a Qp of 115 mls. The Qs uses the LVOT diameter and AV VTI to calculate a Qs of 34.7 mls. The Qp - Qs is the shunt volume or, in this case, the flow through the ASD of 77.9 mls. The shunt fraction is the Qp/Qs which yields a shunt fraction of 3.08 which is a large shunt. The TR volume is PISA 0.686 cm, VTI 112 cm with a Vmax of 286 cm/sec for a regurgitant volume of 84 mls.
The RVSP calculates to around 43 mmHg.
Using the ASD numbers, the ASD diameter and the ASD VTI, the ASD stroke volume is 89.4 mls. Why is the shunt volumes different? It could be as simple as measurement error since the numbers are only off about 10-12% which could easily be done when measuring the diameters of the RVOT, LVOT or ASD.
Alternatively, on the color Doppler scan, the TR jet initially shoots straight for the ASD and on some frames, actually goes into the left atrium thereby possibly increasing the size of the shunt from more pressure in the LA in early diastole. Of course, the TR jet directed towards the ASD may also impede flow across the ASD directly or increase the RA pressure which would decrease the gradient across the ASD and lower it's flow. So the question remains, what is the effect of a TR jet on an ASD?
Kai et al looked at TR jets and ASDs and found that right-to-left shunting occurred in patients with large ASD diameters (> 2.5 cm), older (54 yo versus 34 yo), had higher PA pressures (36 versus 25), had larger shunts (Qp/Qs 3.6 versus 2.4), and had moderate or more TR (TR jet area > 4cm2 versus mild or no TR). When looking at this patient, it appears this patient fits with the right to left shunt from a TR jet would be likely to occur.
The etiology of the TR after a longstanding ASD would most likely be annular dilation or right ventricular enlargment with restriction of the tricuspid valve. In this case the tricuspid valve annulus was not enlarged. However, in the last loop, the TV appears exhibit coaptation below the plane of the annulus. Therefore, restricted leaflet motion of the anterior and/or posterior leaflets was likely. ASDs can be associated with mitral and tricuspid valve prolapse.
Tricuspid regurgitation has undergone an envolution in therapy. Originally, it was thought that TR was not that bad and, in any event, if the left sided lesions where fixed, then the TR would resolve. TR was monitored until it was severe and then patients were sent to surgery with the resulting high mortality rates. Recently, it was thought that patients with moderate or severe TR should be referred sooner rather than later to reduce the mortality rate. Current recommendations mainly look at the tricsupid valve diameter and the amount of TR. In this patient the TV annulus diameter wasn't enlarged, however, the severe TR should be fixed to avoid worsening right heart failure.
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