Transvalvular Gradients for Balloon-Expandable and Self-Expanding Valves

Abstract: Self-expanding valves have been associated with superior hemodynamics versus balloon-expandable valves. Our aim was to compare invasive gradients between valve types for similarly sized valves. Patients who underwent transcatheter aortic valve replacement (TAVR) at the Malcom Randall Veterans Affairs Medical Center and the Bern University Hospital were considered for this analysis. From 1623 subjects who underwent TAVR, a total of 566 had available invasive hemodynamic data. After applying exclusion criteria, we included 499 for analysis. With immediate invasive hemodynamic assessment, balloon-expandable valves were associated with similar/marginally lower transvalvular gradients versus self-expanding valves. With postoperative echocardiography within 24 hours, self-expanding valves were associated with lower Doppler gradients versus balloon-expandable valves for all size categories.

J INVASIVE CARDIOL 2020;32(10):E258-E260. 

Key words: hemodynamics, transcatheter heart valves

Transcatheter aortic valve replacement (TAVR) is commonly performed with balloon-expandable or self-expanding valves. Self-expanding valves have been associated with superior hemodynamics versus balloon-expandable valves.¹ Accordingly, self-expanding valves have been associated with a lower incidence of prosthesis-patient mismatch versus balloon-expandable valves.² This has been postulated as an advantage of self-expanding valves when considering device options, especially in small aortic annuli, where prosthesis-patient mismatch is possible.² The data for these observations are derived from postoperative echocardiography. Our primary aim was to compare immediate invasive gradients between valve types for similarly sized valves.

Methods

Patients who underwent TAVR at the Malcom Randall Veterans Affairs Medical Center in Gainesville, Florida and the Bern University Hospital in Bern, Switzerland were considered for this analysis. We excluded patients who underwent valve-in-valve TAVR or received an investigational device. Aortic annulus measurements were obtained from TAVR-protocol computed tomography. Immediate transvalvular mean gradients were obtained by invasive hemodynamic assessment. Postoperative Doppler assessment of mean gradient was obtained by echocardiography within 24 hours. Invasive assessments of left ventricular and aortic pressures were performed with a dual-lumen pigtail catheter or 2 single-lumen pigtail catheters, 5-10 minutes after valve implantation. Catheter(s) were flushed and zeroed. Left ventricular and aortic pressures were recorded during stable rhythm at end of expiration. 

Balloon-expandable 23 mm and self-expanding 26 mm valves were categorized as “small” valves, balloon-expandable 26 mm and self-expanding 29 mm valves were categorized as “medium” valves, and balloon-expandable 29 mm and self-expanding 31/34 mm valves were categorized as “large” valves. Continuous data are reported as mean ± standard deviation and P-values were derived from Student’s t-tests.

Results

From 1623 patients who underwent TAVR, a total of 566 patients had available invasive hemodynamic data. After applying exclusion criteria, we included 499 patients in the analysis. Mean age was 80.1 ± 7.6 years, conscious sedation was performed in 77.3%, and transfemoral access was used in 97.6%. Among the small valve group (n = 128), 43.0% were CoreValves (Medtronic), 35.2% were Sapien 3 valves (Edwards LifeSciences), 12.5% were Sapien XT valves (Edwards LifeSciences), and 9.4% were Evolut R valves (Medtronic). Among the medium valve group (n = 240), 49.2% were Sapien 3 valves, 25.8% were CoreValves, 19.2% were Sapien XT valves, and 5.8% were Evolut R valves. Among the large valve group (n = 131), 58.8% were Sapien 3 valves, 24.4% were CoreValves, 13.7% were Sapien XT valves, and 3.1% were Evolut R valves.

Invasive gradients. Immediate transvalvular mean gradients were similar for small balloon-expandable and self-expanding valves. Immediate transvalvular mean gradients were marginally lower for medium and large balloon-expandable valves compared with self-expanding valves (Table 1).

Doppler gradients. Doppler mean gradients were lower for self-expanding valves compared with balloon-expandable valves for each category of valve size (Table 1). 

Discussion

The principal findings of this research are: (1) with immediate invasive hemodynamic assessment, balloon-expandable valves were associated with similar/marginally lower transvalvular mean gradients versus self-expanding valves; and (2) with postoperative echocardiography, self-expanding valves were associated with lower Doppler mean gradients versus balloon-expandable valves for all size categories. 

This research confirms previous observations that self-expanding valves were associated with lower Doppler mean gradients than balloon-expandable valves.¹ Our Doppler gradients were also similar to other reports according to valve type and size.¹ A novel finding from this research is that we documented similar/lower transvalvular mean gradients immediately after valve implantation with balloon-expandable valves compared with self-expandable valves. While invasive hemodynamic assessment is considered the gold standard for evaluation of transvalvular gradients, postoperative echocardiography has been used exclusively in landmark clinical trials for assessment of early valve performance.¹ 

It is possible that balloon-expandable valves could be associated with a small degree of early recoil, while self-expanding valves could be associated with continued valve expansion. This has been postulated as the reason for the reduction in paravalvular aortic regurgitation over intermediate-term follow-up with self-expanding valves.³ A separate study that examined invasive gradients after valve deployment and nearly simultaneous Doppler gradients found that Doppler overestimated transvalvular gradients.⁴ This was attributed to the pressure recovery phenomenon.⁵ It is possible that differences exist in Doppler assessment of transvalvular gradients between valve types.

A strength of this research is the use of TAVR-protocol computed tomography measurements of aortic annulus dimensions. Within valve size categories, area-derived and perimeter-derived diameters were nearly identical between valve types. Limitations are a relatively small subcohort of large self-expanding valves, a lack of core laboratory analysis for invasive and echocardiography measurements, a relatively small proportion of patients eligible for study participation, and insufficient data to examine “very small” valves (ie, balloon-expandable 20 mm and self-expanding 23 mm valves). These results do not apply to valve-in-valve procedures. Postoperative echocardiography was performed within 24 hours after the procedure and it is conceivable that flow dynamics could change from the immediate operative to early postoperative period. However, the focus of this study was to examine transvalvular gradients at a discrete time point, rather than compare gradient change as a function of time. The clinical significance of this research is unknown. A prospective study is needed to examine invasive transvalvular gradients at a later time point, after any potential valve remodeling has occurred. 

Conclusion

Immediate invasive mean gradients are similar in balloon-expandable and self-expandable valves. Early postoperative Doppler gradients are lower for self-expanding valves compared with balloon-expandable valves.

From the ¹Department of Medicine University of Texas Southwestern, Dallas, Texas; ²Department of Medicine, University of Florida, Gainesville, Florida; ³Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; and ⁴Division of Cardiology, Mitsui Memorial Hospital, Tokyo, Japan. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Bavry reports significant honoraria from the American College of Cardiology. Dr Okuna reports modest lecture fees from Abbott Vascular. Dr Stortecky reports grant support to his institution from Edwards Lifesciences, Medtronic, Abbott Vascular, and Boston Scientific; personal fees from Boston Scientific, BSC/BTG, and Teleflex. Dr Windecker reports research and educational grants to his institution from Abbott Vascular, Amgen, Bayer, BMS, Biotronik, Boston Scientific, CSL Behring, Edwards Lifesciences, Medtronic, Polares, and Sinomed. Dr Pilgram reports research grants to his institution from Biotronik, Boston Scientific, Edwards Lifesciences; personal speaker fees from Biotronik and Boston Scientific; consultant income from HighLifeSAS. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript accepted April 21, 2020.

Address for correspondence: Anthony A. Bavry, MD, MPH, Department of Internal Medicine, Division of Cardiology, UT Southwestern Medical Center, 2001 Inwood Rd, Dallas, TX 75390. Email: aabavry@alumni.harvard.edu; Twitter:  @AABavry

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