Can a simple echocardiographic Doppler VTI based flow comparison between the RVOT and LVOT assist in identifying patients with a significant atrial septal defect?

Background

Detection of haemodynamically significant shunting from atrial septal defect (ASD) can be identified by using the pulmonary-systemic flow ratio (Qp/Qs). However, calculation of Qp/Qs by echocardiography relies on geometric assumptions that outflow tracts are circular, suffers from squared linear measures, and accurate measurement of right ventricular outflow tract (RVOT) diameter is challenging. Whilst adults with ASD should have overt right ventricular dilatation, RV sizing on echocardiography is often subjective and underappreciated. We evaluated whether a dimensionless index of flow (VTI) differences between the RVOT and left ventricular outflow tract (LVOT) could assist in identifying patients with ASD, and compared it with relative atrial index (RAI), a parameter previously assessed in identifying atrial shunting.

Methods

Data from 64 consecutive patients who underwent ASD closure and had no concomitant lesions, were compared with 63 normal controls. RVOT VTI, LVOT VTI, LVOT diameter, and atrial areas were measured.

Results

Between controls and ASD patients, there was no difference in LVOT VTI or forward stroke volume, but ASD patients had significantly higher RVOT VTI. The RVOT-LVOT VTI ratio was 1:1 in controls and 1.5:1 in ASD patients. Area under the ROC curve analysis of RVOT-LVOT VTI ratio was 0.83, and a ratio of 1.1:1 predicted patients with ASD with 86% sensitivity and 73% specificity. In comparison, the area under the ROC curve analysis of RAI was 0.70, and an RAI of 1.05:1 predicted patients with ASD with 77% sensitivity and 44% specificity.

Conclusion

Calculation of the dimensionless RVOT-LVOT VTI ratio is simple, and may be a useful additional semi-quantitative tool to assist cardiologists and sonographers in detecting atrial shunting, particularly in patients with borderline or overt right heart dilatation, and identify who patients should undergo further evaluation.

Funding Acknowledgement

Type of funding sources: None.

Association between prosthesis geometry and leaflet thrombosis following transcatheter aortic valve replacement

Introduction

Leaflet thrombosis (LT) following transcatheter aortic valve replacement (TAVR) is a recognised condition. The association between prosthesis geometry [expansion, implant depth and commissural alignment (CA)] and LT is unclear.

Methods

Patients that received intra-annular TAVR prosthesis and post-procedure computed tomography (CT) with a 320-slice scanner were included. LT, defined as at least 50% restricted leaflet motion, was assessed with a dedicated 3Mensio workstation by two experienced CT readers. Prosthesis expansion was defined as actual divided by expected prosthesis area as a percentage of expected area whilst eccentricity was [(maximum diameter − minimum diameter) / maximum diameter) × 100%], both measured at prosthesis inflow, annulus and outflow. Implant depth was the average distance between prosthesis inflow and nadir of each cusp. CA was the average angle between each native and prosthesis leaflet coaptations. Significant commissural misalignment (CMA) was defined as CA greater than 30 degrees. To exclude anticoagulation bias, similar analysis was also performed in the cohort of non-anticoagulated patients.

Results

117 patients were included; the prevalence of LT was 13.7% [13/93 cases (14.0%) of Lotus valves and 3/24 cases (12.5%) of Sapien 3 valves]. Baseline demographics (age, STS score, cardiac risk factors) and procedural characteristics (access site, post-dilation, repositioning) were similar in both groups. None of the patients with LT were discharged on anticoagulation therapy (0.0% vs 22.8%, p<0.01). There were no differences in actual prosthesis area, perimeter or eccentricity at the three prosthesis levels. Patients with LT had reduced annulus expansion (89.3±9.8% vs 94.6±8.3%, p=0.02), lower implant depth (6.9±1.5mm vs 4.9±1.5mm, p<0.01) and more significant CMA (81.3% vs 48.5%, p=0.02). These findings were similar in patients that were not anticoagulated (94/117 patients).

Conclusion

Patients with LT had reduced annulus expansion, lower implant depth and greater CMA. These findings were not affected by presence or absence of anticoagulation. These factors may be important considerations during procedural planning for TAVR.

Graphical abstract

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Health and Medical Research Council (NHMRC). National Heart Foundation (NHF) Australia.

P2238Prognostic value and incremental benefit of ischaemic myocardial burden subtended by non-invasive CT-derived fractional flow reserve (FFRCT) significant stenoses

Background

Fractional flow reserve derived from CT-coronary angiography (FFRCT) accurately identifies ischaemic vessels which may be associated with clinical outcomes. Its predictive value in grey zone FFRCT values between 0.7–0.8 is not defined. The technique permits estimation of burden of ischaemic myocardium subtended by FFRCT significant vessels.

Purpose

To evaluate the prognostic value and incremental benefit of FFRCT defined ischaemic myocardial burden when compared to FFRCT alone.

Methods

This is a subanalysis of NXT (Analysis of Coronary Blood-Flow Using CTA:Next-Steps), a prospective study of stable coronary artery disease (CAD) patients referred for invasive angiography (ICA) undergoing invasive FFR, CTA and FFRCT in whom treating physicians had been blinded to FFRCT results. Primary endpoint, defined as a composite of non-fatal myocardial infarction and any revascularisation, was determined in 206 patients (age 64±9.5 years, 64% male) and 618 vessels. Burden of ischaemic myocardium was defined as percentage of myocardium subtended beyond the point at which a vessel's FFRCT becomes ≤0.8 as estimated by APPROACH score (FFRCT-APPROACH). In significant FFRCT vessels, the predictive value and incremental benefit of FFRCT-APPROACH was compared with significant FFRCT (≤0.8) for primary endpoint as measured by area under the receiver operator characteristic curve (AUC). Significant ischaemic myocardial burden was defined as >10%. The incidence and relationship between the primary endpoint with each 10% increase in FFRCT-APPROACH and 0.05-unit decrease in FFRCT values ≤0.8 was determined.

Results

Significant FFRCT was identified in 52.9% of patients (109/206) and 29.3% of vessels (181/618). At 4.7 years median follow-up the incidence of the primary endpoint in vessels with significant FFRCT-APPROACH was 58.9% (96/163) which was comparable with vessels with significant FFRCT (55.2%,100/181; P=0.50). The predictive value of FFRCT-APPROACH for the primary endpoint was comparable with FFRCT (AUC 0.72 [95% CI 0.65–0.79] vs 0.71 [0.63–0.78], P=0.79). When combined, there was significant predictive improvement compared with FFRCT alone (AUC 0.77 [0.70–0.84]; P=0.01). The largest incremental benefit upon FFRCT was observed in vessels with FFRCT values in the grey zone between 0.70–0.80 (AUC 0.76 [0.65–0.86] vs 0.62 [0.48–0.74]; P<0.01). Each 10% increase in FFRCT-APPROACH (Adjusted-HR 1.36; 95% CI 1.16–1.60; P<0.001) and each 0.05-unit FFRCT decrease (Adjusted-HR 1.42; 1.19–1.70; P<0.001) were independently associated with significant increase in the incidence of the primary-endpoint.

Conclusion

In patients with stable CAD referred for ICA, the burden of ischaemic myocardium subtended by FFRCT significant vessels predicted non-fatal myocardial infarction and future revascularisation. This provided significant incremental benefit when used in combination with FFRCT particularly at FFRCT values in the grey zone between 0.7 to 0.8.