Insights into functional mitral regurgitation using the average pixel intensity method

The Pixel Variation Score: An Echocardiographic Index to Assess Temporal Variation of Mitral Regurgitant Flow

BACKGROUND

In mitral regurgitation (MR), temporal variation of MR flow has been considered an important reason for inaccurate MR grading. Current echocardiographic methods for assessing temporal MR flow variation are complex, and their clinical relevance has not been investigated. In this study, we investigated whether assessing MR flow variation using a dimensionless index with echocardiography is feasible, clinically meaningful, and related to patient outcomes.

METHODS

Consecutive patients with mitral valve prolapse (MVP, n = 244) and functional MR (FMR, n = 396) underwent comprehensive echocardiography. Mitral regurgitation severity was assessed using an integrated approach advocated by current guidelines. The MR continuous-wave Doppler envelope was divided into 3 segments of equal duration. Each segment's pixel intensity was assessed to calculate the pixel variation score (PVS).

RESULTS

The PVS was lower in FMR patients than in MVP patients. Lower PVS was associated with worse MR, larger left atrial and left ventricular dimensions, lower ejection fraction, and higher pulmonary artery pressures. In MVP, PVS was significantly associated with postoperative left ventricular reverse remodeling and was able to reclassify most patients in whom single-frame measures overestimated MR severity. Finally, PVS had incremental prognostic value on top of clinical and echocardiographic predictors of outcome.

CONCLUSIONS

Temporal variation in MR flow can reliably be assessed with echocardiography through analysis of the continuous-wave Doppler signal. A high PVS value may alert the echocardiographer to defer from single-frame MR grading and also suggests that the MR is probably not severe.

Diagnostic and Prognostic Value of Several Color Doppler Jet Grading Methods in Patients With Mitral Regurgitation

Color Doppler is a widely used ultrasound imaging method for assessing mitral regurgitation (MR) in clinical practice. Nevertheless, color Doppler-based grading of the MR jet has been rarely considered in clinical studies. We investigated the diagnostic and prognostic value of several color Doppler MR jet grading methods and compared them with quantitative grading of MR. The MR color Doppler jet was assessed in 476 MR patients using an 'integrated' eyeballing approach by quantifying the color Doppler jet area, jet area/left atrium area and jet length and using quantitative methods. Clinical endpoints were scored as major adverse clinical events, including cardiovascular death, heart failure hospitalization and mitral valve intervention. When assessed by three echocardiographers, there was a moderate inter-observer agreement for eyeballing color Doppler grade of MR (intraclass correlation coefficient 0.69, p < 0.001). The intra-observer agreement was good for all color Doppler approaches. In primary MR, eyeballing color Doppler correlated well with (in)direct measures of MR severity, with a negative predictive value of 91% when using a grade 2 color Doppler as cut-off. In secondary MR, eyeballing color Doppler grade and jet length were predictors of clinical outcome in Cox proportional hazards analysis (p = 0.003), independent of pulmonary pressures, atrial and ventricular volumes. Overall, the integrated eyeballing approach performed better than color Doppler quantification of the MR jet area and length. In conclusion, this study shows that color Doppler grading of the distal MR jet performs well in predicting events in primary and secondary MR, compared to quantitative grading methods.

Arrhythmic Mitral Valve Prolapse: Introducing an Era of Multimodality Imaging-Based Diagnosis and Risk Stratification

Mitral valve prolapse is a common cardiac condition, with an estimated prevalence between 1% and 3%. Most patients have a benign course, but ever since its initial description mitral valve prolapse has been associated to sudden cardiac death. Although the causal relationship between mitral valve prolapse and sudden cardiac death has never been clearly demonstrated, different factors have been implicated in arrhythmogenesis in patients with mitral valve prolapse. In this work, we offer a comprehensive overview of the etiology and the genetic background, epidemiology, pathophysiology, and we focus on the state-of-the-art imaging-based diagnosis of mitral valve prolapse. Going beyond the classical, well-described clinical factors, such as young age, female gender and auscultatory findings, we investigate multimodality imaging features, such as alterations of anatomy and function of the mitral valve and its leaflets, the structural and contractile anomalies of the myocardium, all of which have been associated to sudden cardiac death.

Outcome of degenerative nonprolapse mitral regurgitation using the average pixel intensity method

BACKGROUND

Primary mitral valve regurgitation (MR) is a comprehensive term that mostly comprises mitral valve prolapse (MVP), while other causes of degenerative MR are often not considered. We describe the echocardiographic characteristics of degenerative nonprolapse mitral regurgitation (DMR) and assess the outcome at medium-term follow-up using the novel average pixel intensity (API) method.

METHODS

Of 126 patients with any nonprolapse DMR were consecutively included. MR was graded according to all guideline-recommended parameters and with the API method. MR flow dynamics in DMR were compared to MVP-MR and functional MR (FMR).

RESULTS

DMR is associated with moderate-to-severe calcifications of the mitral valve apparatus, and a low event rate was observed at a mean follow-up of 27 months. The API grading method had a higher feasibility (94%) compared to proximal isovelocity surface area (PISA) (60%) method and vena contracta width (VCW) (71%) for assessing MR. The API method was predictive for events. The API method also provides insights into DMR flow dynamics: A triphasic pattern was observed with a midsystolic nadir for both API and PISA-EROA, which is similar to the dynamic flow pattern described in FMR, but distinct from holosystolic MVP-MR. Compared to FMR and MVP-MR patients, DMR is less severe and patients with DMR are generally older than MVP-MR patients.

CONCLUSIONS

DMR is a distinct MR pathology and conveys a relatively low event rate. MR grading was feasible with the API method, and flow dynamics demonstrated a similar triphasic pattern compared to FMR but distinct from holosystolic MVP-MR.

Proportionate or disproportionate secondary mitral regurgitation: how to untangle the Gordian knot?

Recent randomised percutaneous mitral intervention trials in patients with heart failure with secondary mitral regurgitation (SMR) have yielded contrasting results. A 'relative load' or 'proportionality' conceptual framework for SMR has been proposed to partly explain the disparate results. The rationale behind the framework is that SMR depends on the left ventricular dimension and not vice versa. In this review, we provide an in-depth analysis of the proportionality parameters used in this framework and also discuss the regurgitant fraction. We also consider haemodynamic observations in SMR that may affect the interpretation and comparisons among proportionality parameters. The conclusion is that the proportionality concept remains hypothetical and requires prospective validation before envisaging its use at individual patient level for risk stratification or therapeutic decision-making.

Average pixel intensity method for prediction of outcome in secondary mitral regurgitation

Background

Echocardiographic grading of secondary mitral regurgitation (SMR) severity is challenging and involves multiple guideline-recommended parameters. We previously introduced the average pixel intensity (API) method for grading SMR. In this study, the clinical outcome in SMR based on the API method for grading MR was compared with conventional grading methods.

Methods

231 patients with systolic heart failure and reduced ejection fraction (ischaemic/non-ischaemic) and SMR were prospectively enrolled. MR was graded using all guideline-recommended parameters and the API method, which is based on the pixel intensity of the continuous wave Doppler signal. The primary outcome was MACE (major adverse cardiac event).

Results

The API method was applicable in 98% of patients with SMR (n=227). During a median follow-up of 24 months, 98 patients (43%) had a MACE (cardiovascular mortality (n=50, 22%), heart failure hospitalisation (n=44, 19%), mitral valve surgery (n=11, 5%), percutaneous mitral intervention (n=12, 5%), heart transplantation (n=5, 2%)). On log-rank test, the API method was highly significant in predicting clinical outcome. On multivariable Cox proportional hazard analysis, SMR grading with the API method was an independent predictor of clinical outcome (along with NYHA class and right ventricular systolic pressure; p<0.001), increasing the event risk by 9% per 10 au API rise (p=0.001). In the same multivariable analysis, proximal isovelocity surface area (PISA)-effective regurgitant orifice area or PISA-regurgitant volume were not independent predictors of events (p=0.18 and 0.26, respectively).

Conclusion

SMR grading with the API method is an independent predictor of clinical outcome and provides prognostic information in addition to clinical and other echocardiographic variables.