Doppler-catheter discrepancies in patients with bileaflet mechanical prostheses or bioprostheses in the aortic valve position

Transthoracic echocardiographic Doppler metrics in evaluating bioprosthetic tricuspid valve dysfunction

PURPOSE

There is currently limited information on the utility of transthoracic echocardiography (TTE)-derived Doppler parameters for assessing bioprosthetic tricuspid valve (BTV) dysfunction. Our study aimed to establish the precision and appropriate reference ranges for routinely collected transthoracic Doppler parameters in the assessment of BTV dysfunction.

METHODS

We retrospectively evaluated 100 BTV patients who underwent TTE. Based on redo surgical confirmation or more than 2 repeat TTE or transesophageal echocardiography (TEE) examinations, patients were allocated to normal (n = 61), regurgitant (n = 24), or stenotic (n = 15) BTV group. Univariate and multivariate binary logistic regression were performed to identify TTE Doppler parameters that detected BTV dysfunction.

RESULTS

The VTI ratio (VTITV/VTILVOT) was the most accurate Doppler parameter for detecting BTV dysfunction, with a ratio of >2.8 showing 84.6% sensitivity and 90.2% specificity. VTI ratio > 3.2, mean gradient (MGTV) > 6.2 mmHg and pressure half-time > 218 ms detected significant BTV stenosis, with sensitivities of 100%, 93.3% and 93.3% and specificities of 82.4%, 75.3% and 87.1%, respectively. After multivariate analysis, the VTI ratio > 2.8 (OR = 9.00, 95% CI = 2.13-41.61, p = .003) and MGTV > 5.1 mmHg (OR = 6.50, 95% CI = 1.69-27.78, p = .008) were the independent associations of BTV dysfunction. With these cutoff values, 75.0%-92.2% of normal and 62.5%-96.0% of dysfunctional BTV were identified.

CONCLUSIONS

Doppler parameters from TTE can accurately identify BTV dysfunction, particularly with VTI ratio > 2.8 and MGTV > 5.1 mmHg, to assess the need for additional testing with TEE.

Discrepancy between invasive and echocardiographic transvalvular gradient after TAVI: Insights from the LAPLACE-TAVI registry

BACKGROUND

Echocardiography-based transvalvular mean pressure gradient (ECHO-mPG) used to assess the forward valve function and structural valve deterioration could overestimate the true pressure gradient. This study evaluated the discrepancy between invasive and ECHO-mPG after transcatheter aortic valve implantation (TAVI) with respective valve type and size, its impact on a device success criterion, and predictors of a pressure discrepancy.

METHODS

We analyzed 645 patients registered in a multicenter TAVI registry (balloon-expandable valve [BEV]: 500; self-expandable valve [SEV]: 145). The invasive transvalvular mPG was measured after valve implantation using two Pigtail catheters (CATH-mPG), while the ECHO-mPG was measured within 48 h after TAVI. Pressure recovery (PR) was calculated using the following formula: ECHO-mPG × effective orifice area (EOA)/ascending aortic area (AoA) × (1 - EOA/AoA).

RESULTS

ECHO-mPG was weakly correlated with (r = 0.29, p < 0.0001), and consistently overestimated CATH-mPG in both BEV and SEV, and respective valve sizes. The magnitude of the discrepancy was larger for BEV than SEV (p < 0.001) and smaller valves (p < 0.001). After the correction of PR using the above formula, the pressure discrepancy remained for BEV (p < 0.001) but not SEV (p = 0.10). The proportion of patients with an ECHO-mPG > 20 mmHg decreased from 7.0% to 1.6% after correction (p < 0.0001). Among the baseline and procedural variables, post-procedural ejection fraction, BEV versus SEV, and smaller valves were associated with a larger discrepancy in mPG.

CONCLUSIONS

ECHO-mPG could be overestimated after TAVI, especially in patients with a smaller BEV. A higher ejection fraction, BEV, and smaller valves were predictors of a pressure discrepancy between CATH- and ECHO-mPG.

Significant intra-valvular pressure loss across EPIC SUPRA and perimount magna supra-annular designed aortic bioprostheses in patients with normal aortic size

Doppler-derived trans-prosthetic gradients are higher and the estimated effective valve area is smaller than the catheter-derived and directly measured hemodynamic values, mostly due to pressure recovery phenomenon. Pressure recovery to a varying extent is common to all prosthetic heart valves including bioprostheses. Pressure recovery-related differences are usually small except in patients with bileaflet metallic prosthesis, wherein high-pressure local jets across central orifice have been documented since long back and also in patients with narrow aortic root. We describe two patients with normally functioning stented aortic bioprostheses with supra-annular design (EPIC SUPRA and PERIMOUNT MAGNA), wherein very high trans-prosthetic gradients and critically reduced estimated effective valve orifice areas in presence of normal aortic size were consistently recorded over long periods of follow-up. The valve leaflets, however had normal excursion, were thin, opened with a triangular or oblong shape and had expected geometric valve area (1.7 and 1.6 cm² respectively) measured by 3D trans-oesophageal echocardiographic planimetry. Pressure recovery upstream the valves accounted for 20% and 12% of total pressure gradients respectively. Dominant site for pressure drop was intra-valvular (75–85%). Such a phenomenon has not been reported in vivo for these two valve designs.

Validation of a numerical FSI simulation of an aortic BMHV by in vitro PIV experiments

In this paper, a validation of a recently developed fluid-structure interaction (FSI) coupling algorithm to simulate numerically the dynamics of an aortic bileaflet mechanical heart valve (BMHV) is performed. This validation is done by comparing the numerical simulation results with in vitro experiments. For the in vitro experiments, the leaflet kinematics and flow fields are obtained via the particle image velocimetry (PIV) technique. Subsequently, the same case is numerically simulated by the coupling algorithm and the resulting leaflet kinematics and flow fields are obtained. Finally, the results are compared, revealing great similarity in leaflet motion and flow fields between the numerical simulation and the experimental test. Therefore, it is concluded that the developed algorithm is able to capture very accurately all the major leaflet kinematics and dynamics and can be used to study and optimize the design of BMHVs.

Impact of energy loss index on left ventricular mass regression after aortic valve replacement

Background

Recently, the energy loss index (ELI) has been proposed as a new functional index to assess the severity of aortic stenosis (AS). The aim of this study was to investigate the impact of the ELI on left ventricular mass (LVM) regression in patients after aortic valve replacement (AVR) with mechanical valves.

Methods

A total of 30 patients with severe AS who underwent AVR with mechanical valves was studied. Echocardiography was performed to measure the LVM before AVR (pre-LVM) (n = 30) and repeated 12 months later (post-LVM) (n = 19). The ELI was calculated as [effective orifice area (EOA) × aortic cross sectional area]/(aortic cross sectional area − EOA) divided by the body surface area. The LVM regression rate (%) was calculated as 100 × (post-LVM − pre-LVM)/(pre-LVM). A cardiac event was defined as a composite of cardiac death and heart failure requiring hospitalization.

Results

LVM regressed significantly (245.1 ± 84.3 to 173.4 ± 62.6 g, P < 0.01) at 12 months after AVR. The LVM regression rate negatively correlated with the ELI (R = −0.67, P < 0.01). By receiver operating characteristic (ROC) curve analysis, ELI <1.12 cm²/m² predicted smaller (<−30.0 %) LVM regression rates (area under the curve = 0.825; P = 0.030). Patients with ELI <1.12 cm²/m² had significantly lower cardiac event-free survival.

Conclusion

The ELI as well as the EOA index (EOAI) could predict LVM regression after AVR with mechanical valves. Whether the ELI is a stronger predictor of clinical events than EOAI is still unclear, and further large-scale study is necessary to elucidate the clinical impact of the ELI in patients with AVR.

Validation study of Doppler-derived transmitral valve gradients compared to near simultaneously obtained directly measured catheter gradients immediately after mitral valve repair surgery

OBJECTIVE

To evaluate the accuracy of Doppler-derived transmitral valve gradients immediately after mitral valve repair by comparing them with near simultaneously obtained direct catheter gradients.

DESIGN

A prospective study.

SETTING

A tertiary care medical center.

PARTICIPANTS

Twenty elective adult surgical patients presenting for mitral valve repair surgery.

METHODS

Mitral valve surgery proceeded in standard fashion except for the use of a smaller than usual left ventricular vent catheter (Medtronic DLP 10 French left heart vent catheter). After completion of the mitral valve repair and subsequent cardiac de-airing, the patient was weaned from cardiopulmonary bypass. Immediately after separation, the study period began. Near simultaneous transmitral Doppler gradients were obtained with directly measured catheter gradients via the vent catheter.

RESULTS

While the mean peak gradient difference of 1.1 mmHg was small (p-value 0.18, 95% CI: -0.54 to 2.73 mmHg), the correlation between Doppler and catheter gradient measurements (Pearson correlation coefficient r = 0.54, p = 0.055) only approached statistical significance due to the large variance associated with the small sample size. In all patients with a peak gradient greater than 10 mmHg (4 of the 20 patients), overestimation of catheter gradients by Doppler occurred, with two showing a 62% to 73% discrepancy. In these two cases, there was also evidence for elevated left ventricular end-diastolic pressure (LVEDP) along with high transmitral blood flow velocities.

CONCLUSION

Doppler-derived transmitral gradients provide a simple, safe, and reliable measure of the true physiologic transmitral valve gradient. At the same time, it is important to recognize that significant Doppler over-estimation of catheter gradients may occur in patients with elevated Doppler transmitral velocities. The causes of these overestimations are unknown. They may be related to technical recording errors. They may also be related to an inherent weakness in Doppler technology--its inability to account for any distal recovery of pressure, which in a select group of patients could be significant.

Falsely elevated valve gradients by echocardiography in the 3f aortic bioprosthesis

The 3f Aortic Bioprosthesis (Medtronic, Inc, Minneapolis, MN) is a stentless aortic valve with a novel design that resembles a "tube within a tube." Although it has the potential for improved durability and hemodynamic performance, long-term data on this valve remain elusive. We present here 3 patients in whom postoperative echocardiography revealed significantly elevated transvalvular gradients of the 3f valve while transcatheter gradients proved to be negligible. By virtue of the unique design of the 3f bioprosthesis, great caution should be taken when interpreting echocardiographically derived gradients.

Localized transvalvular pressure gradients in mitral bileaflet mechanical heart valves and impact on gradient overestimation by Doppler

BACKGROUND

It has been reported that localized high velocity may be recorded by continuous-wave Doppler interrogation through the smaller central orifices of bileaflet mechanical heart valves (BMHV) and that this may result in overestimation of the transvalvular pressure gradient (TPG). However, the prevalence and clinical relevance of this phenomenon remain unclear, particularly for BMHVs in the mitral position. The objective of this in vitro study was to assess the presence and magnitude of localized high velocity in mitral BMHVs as well as its impact on TPG overestimation by Doppler.

METHODS

Nine BMHVs were tested under nine different flow conditions (volumes and flow waveforms) in a simulator specifically designed to assess mitral valve hemodynamics. Flow velocity was measured at three different locations (leading edge, midleaflets, and trailing edge) within the central and lateral orifices of the BMHVs using pulsed-wave Doppler. TPG was measured by pulsed-wave and continuous-wave Doppler and by catheterization.

RESULTS

The maximum flow velocity occurred within the central orifice of the BMHV in 61% of the 81 tested conditions. This locally higher velocity within the central orifice predominantly occurred at the leading edge of the prosthesis. Doppler overestimated mean TPG by an average of 5% to 10% compared with catheterization. The magnitude of the localized high velocity and ensuing overestimation of TPG by Doppler was more important at higher mitral flow volumes (P < .0001) as well as in BMHVs with smaller internal ring diameters (P < .0001).

CONCLUSIONS

This study shows that the flow velocity distribution within the three orifices of mitral BMHVs is not uniform and that higher velocity occurs more frequently, but not always, within the inflow aspect of the central orifice. In most mitral BMHVs and flow conditions, this localized high-velocity phenomenon causes small overestimation of TPGs (<2 mm Hg and <10%) by Doppler and is thus not clinically relevant. However, in small mitral BMHVs exposed to high flow rates, the overestimation of TPG due to localized high velocity could become more important and overlap with the range of gradients found in patients with prosthesis dysfunction or prosthesis-patient mismatch.