The important prognostic information provided by CMR post TAVR

The important prognostic information provided by CMR post TAVR

Transcatheter aortic valve replacement (TAVR) has become an important procedure for treatment of aortic valve disease in a selected group of patients. Despite the initial success it is not uncommon for residual aortic regurgitation to remain a significant complication following the procedure. Although the merits of echocardiography on pre-TAVR evaluation have been demonstrated, assessing the

Transcatheter aortic valve replacement (TAVR) has become an important procedure for treatment of aortic valve disease in a selected group of patients. Despite the initial success it is not uncommon for residual aortic regurgitation to remain a significant complication following the procedure. Although the merits of echocardiography on pre-TAVR evaluation have been demonstrated, assessing the regurgitant flow with this method imposes a few problems: the jets are usually multiple and/or eccentric, shadowing is very common due to metal/high calcification in the annulus and Doppler attenuation may also occur with over/underestimation of flow. At the same time, it has been shown previously that precise quantification of the aortic regurgitation is an important prognostic marker for short-term events on follow-up of the procedure.

In this paper by Ribeito et al, the authors propose the use of cardiovascular magnetic resonance (CMR) imaging for assessment of post-TAVR aortic regurgitation and to relate those findings to prognostic information. They enrolled 135 patients in three centers and used both echocardiography and CMR to quantify aortic regurgitation. For echocardiography, the measurement was done in a median of 6 days post-procedure. For CMR, the median time was 40 days using the technique of phase contrast imaging in the ascending aorta as has been previously validated. Patients were followed for a median of 26 months and all-cause mortality and rehospitalization for heart failure were evaluated.

The authors found that 12.8% of the patients presented with moderate/severe aortic regurgitation (regurgitant fraction > 30%) by CMR versus 17.1% by echocardiography. During follow-up, greater regurgitant fraction as classified by CMR was associated with a significantly higher chance of mortality and the combined primary outcome of death and rehospitalization (HR 1.18 and 1.19 respectively for each 5% increase in regurgitant fraction, P<0.001). The net reclassification index (NRI) provided by CMR for predicting 2-year outcome of the primary endpoint was 15% (P<0.03) and a regurgitant fraction ≥ 30% demonstrated  an area under the curve of 0.678 for determining mortality at 2 years. Patients with sever aortic regurgitation as shown by CMR but not by echocardiography presented with higher mortality according to Kaplan-Meier survival curves during follow-up (35.1% vs 13%, P=0.032 with CMR; 19.6% vs 15.2% with echocardiography, P=0.70).

In the discussion, the authors highlight the importance of correct classification of aortic regurgitation grade and suggest that limitations of echocardiography might explain the lack of differentiation in mortality by the method as compared to CMR. Therefore, quantification of aortic regurgitation by CMR might allow more accurate measurement of the grade of the post-TAVR flow with important prognostic consequences during follow-up. For now, it is still not known how the early finding of significant regurgitation might affect management but certainly future studies should be able to use this information to provide selective treatment based on the differentiation of lower and higher risk patients based on CMR findings. Despite that, it appears that patients with worse CMR findings associated with increased mortality and hospitalization post-TA

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