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Echo-of-the-Day
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Echo-of-the-Day Information
The Case-of-the-Week is a presentation of 8 or more video loops to present an important topic in echocardiography. Please reveiw the image or video loops and then answer the questions below. After you have answered the questions you can view the explanation and obtain CME credit (if available).

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Preop Preop TEE or TTE
Intraop An Intraop TEE
IntraopPreOp Intraop TEE or TTE before Operation
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IntraopEnd Intraop TEE or TTE at End of Anesthesia
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Case of the Month Information Table
IntraopEnd is usually a TEE after the Operation and after some event occured to show a change in the TEE
Does PHT have rhythm problems?
Case#: 235
AMA CME Units: 0.25 Units
Estimated Time: 15 minutes.
Presentation:
Two videos are presented. One has atrial fibrillation and the other is normal sinus rhythm.
 
Loop(s):
Case Discussion
 
The measurement method is called the Pressure Half-Time method. The concept of pressure half-time is based upon diastolic rate of flow across the mitral valve measured by continuous wave Doppler. As the mitral valve area decreases, the flow across the mitral valve becomes closer or exceeds a pan-diastolic time period. When the flow becomes pan-diastolic, the pressure gradient must rise to fill the left ventricle and the Vmax of the diastolic flow increases. The slope of the Vmax to the end of the rapid filling phase correlates with the mitral valve area. This was standardize to the time it takes the pressure to decrease by half, hence the pressure half time or PHT. Normal pressure half-time is 20-60 msec. PHT is insensitve to MR, atrial fibrillation, or exercise and replaced the Gorlin formula. A PHT > 220 msec correlated with a MVA < 1.0 cm2.

Mitral valve gradients are sensitive to cardiac output, rising as the flow rises. 2D planimetry, while a useful tool, depends upon a perpendicular cut across the mitral valve which may be difficult to obtain.

PHT decreases with aortic regurgitation that is moderate or severe. Since AR is filling up the ventricle at the same time as the atrium, the left ventricular pressure rises faster and the PHT will be falsely shorter than if the AR was absent. One study reported that only severe AR affects the PHT while moderate AR does not.

Similarly, patients with increased left ventricular stiffness (diastolic dysfunction), the pressure in the left ventricle will rise faster, thereby decreasing the PHT and overestimating the MVA by PHT.

 MVG and PHT doe not correlate well with the MVA calculation by continuity equation after a mitral valve repair. Continuity equation should be used for MVA calculation after a MV repair in one study.

Finally, atrial fibrillation as reported above does not affect PHT. However, one study from JASE showed that patients in NSR tended to have normal atrial-ventricular compliance and overestimated the MVA by PHT whereas patients with atrial fibrillation had increased compliance and underestimated the MVA by PHT when compared to 2D measurements. The article pointed out that it was the compliance that affected the PHT, however, most patients with atrial fibrillation had abnormal compliance.

 
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