P799A new invasive validation method for non-invasive central blood pressure measurement using a suprasystolic sphygmomanometer

Background

Central blood pressure (cBP) is a better predictor of the damage caused by hypertension in comparison with peripheral blood pressure (pBP). Although challenging to measure, numerous devices are trying to reliably estimate cBP non-invasively. Pulse wave velocity (PWV) is another important independent cardiovascular risk factor.

Aim

We sought to deploy a new validation method using a high-fidelity pressure wire as the invasive gold standard measurement for sphygmomanometer devices estimating cBP. Moreover, we invasively calculated the PWV to investigate its relationship to the non-invasively estimated cBP.

Methods

In 50 patients requiring a cardiac catheterization, we measured the blood pressure in the ascending aorta (AAo) with a fluid-filled (FF) guiding catheter (NaCl 0,9%). We compared these values with the results derived simultaneously with a novel sphygmomanometer that estimates cBP from the analysis of brachial artery suprasystolic pressure waves, based on the pressure-wave propagation of a water-hammer acoustic model. This was measured on the left arm with the BP+ device from USCOM Pty Ltd (Sydney, NSW, Australia) while the catheterization was performed via the right radial artery. On 14 of these patients so far, we placed a 0.014" high-fidelity pressure wire in the AAo to measure cBP, when it was clinically indicated to evaluate one or more coronary stenosis by Fractional Flow Reserve (FFR). Ultimately, the wire was pulled back into the humeral artery (HUM). PWV was then calculated from the length of the pullback and the time delay between AAo and HUM pulses by gating to the R-wave of the ECG for both measurements, using MatLab software.

Results

Bland-Altman analysis of the sphygmomanometrically estimated cBPsys and the measured one by a FFR wire (left on figure) demonstrates less scatter than with the FF catheter (right). The mean difference with the sphygmomanometrically derived cBPsys was −1.2±4.7 mmHg (CI95%: −3.8; 1.8) for the FFR wire and 6.0±9.8 mmHg (CI95%: 3.2; 8.9) for the FF catheter. Central diastolic and mean BP were both overestimated by the sphygmomanometer, with respectively −7.8±6.8 mmHg (CI95%: −11.4; −4.2) and −5.5±6.1 mmHg (CI95%: −8.6; −2.3) compared to the FFR wire and −10.3±6.7 mmHg (CI95%: −12.2; −8.3) and −5.5±6.5 (CI95% : −7.3; −3.6) for the FF catheter. The average PWV was 7.0±1.4 m/s. No significant relationship of PWV and cBP was identified (p=0.189). The PWV was 0.8 m/s lower in patients with only one cardiovascular risk factor versus more than one, but without reaching statistical significance.

cBPsys measured. A. FFR; B. FluidF vs BP+

Conclusions

Using a FFR wire in the AAo as a high-fidelity pressure reference, we demonstrated that cBPsys derived from this new sphygmomanometer was accurate, with a non-significant bias (<5mmHg) and high precision (standard deviation <8mmHg) as recommended, criteria not met using the FF guiding catheter measurements. PWV measurements were also easily obtained from the FFR wire method.

P5637A novel bioresorbable magnesium-based stent: initial clinical results and 6-months follow-up by coronary computed tomography angiography scan

Background

Drug-eluting stents (DES) are the gold standard in percutaneous coronary interventions (PCI), but leave a permanent metallic “caging” of the treated vessels limiting further assessment of in-stent lumen patency by coronary computed tomography angiography (CCTA) due to artifacts. Absorbable scaffolds were designed to overcome the caging limitation but the first generation made of poly-L-lactic acid demonstrated higher thrombosis rates. A novel bioresorbable magnesium-based (Mg-)stent coated with a biodegradable polymer eluting sirolimus has been developed, with promising results in the BIOSOLVEII-III studies.

Aim

We sought to characterize PCI results by CCTA at 6-mo follow-up of patients treated with at least one Mg-stent in our institution.

Methods

Prospective observational registry started since January 2017 of younger patients with de novo lesions preferably treated with Mg-stents after balloon pre-dilatation. Procedural data and major adverse clinical events (MACE) at hospital discharge and 6-mo follow-up were collected. Reference vessel and in-stent minimal lumen area were measured on a CCTA performed at 6-mo.

Results

34 Mg-stents (mean diameter: 3.2±0.2 mm, length 21.3±4.1 mm) were successfully implanted in 29 patients (mean age 54±6 years with male:female ratio 3:1). Acute coronary syndrome was the presenting diagnosis in 76% (n=22) with STEMI in 31% (n=9). The left anterior descending artery was treated in 62% (n=21). Calcifications on angiography were found in 14 lesions (41%). Intravascular imaging was performed in 3 PCI. With CCTA at 7.1±3.5 months (n=15 up to date, ongoing further follow-up to be presented), proximal and distal stent markers were well visualized while scaffold struts were not discernible. Mean proximal and distal reference lumen area were respectively 8.5±4.2 mm2 and 6.1±2.8 mm2. Mean in-stent minimal lumen area (MLA) was 6.3±2.9 mm2, with no statistical difference with the mean of the proximal and distal references (7.3±3.3 mm2, p=0.155, Wilcoxon rank test) demonstrating minimal instent hyperplasia at 6-mo: significant in-stent restenosis was noted in only one patient who remains so far asymptomatic (MLA 1.1 mm2; reference vessel lumen area 5.5 mm2). CCTA were non interpretable in 2 patients due to artifacts unrelated to the Mg-stents. One death secondary to a complicated cardiac tamponade was reported. No further MACE at 6-mo were noted.

CCTA cross sectional cut

Conclusion

6-mo CCTA of patients treated with a Mg-stent are fully interpretable to detect in-stent restenosis, without blooming artifacts. Accurate non-invasive assessment of the late results of our monocentric observational registry demonstrated 1 asymptomatic instent restenosis in 34 Mg-stents (3%) and overall optimal stent deployment and late artery patency, achieved with only 1 MACE in 29 patients (3.4%). This highlights the potentials of this new Mg-bioresorbable stent and the use of CCTA for clinical follow-up of the treated patients.