The Clinical Implications of Body Surface Area as a Poor Proxy for Cardiac Output

ABSTRACT

Background

Prosthesis-patient mismatch (PPM), routinely used to characterize the degree of hemodynamic obstruction caused by a prosthetic heart valve, is associated with adverse patient outcomes after aortic valve replacement (AVR). In the common definition of PPM, the opening area of the valve is related to the patients’ cardiac output, by indexing effective orifice area (EOA) with body surface area (BSA). The aim of this study is to assess the implications of using BSA as a proxy for cardiac output.

Methods

744 patients with normal LV function underwent echocardiographic assessment after surgical AVR. To validate the use of BSA as a proxy for cardiac output, the relation between these variables was analyzed. The effects of BSA on the classification of PPM (EOAi < 0.85 cm²/m²) and the presence of hemodynamic obstruction (mean gradient ≥ 20 mmHg and/or Doppler velocity index < 0.35) were estimated.

Results

There was a weak correlation between BSA and cardiac output (r: 0.29, 95% CI: 0.22;0.35), and cardiac output was not proportional to BSA (Cardiac output = 1.5 x BSA +1.9). As a result, the increased risk of patients with a large BSA to be labelled with PPM (OR: 5.2, 95% CI: 2.5,11 per m² BSA), was not reflected by a significantly higher risk of hemodynamic obstruction (OR: 1.5, 95% CI: 0.5,4.9 per m² BSA).

Conclusions

The current definition of PPM results in a systematic overestimation of hemodynamic obstruction in patients with a larger BSA, and we recommend cautious use in this subgroup.

Abbreviations: AVR: Aortic valve replacement; BMI: Body mass index; BSA: Body surface area; EOA: Effective orifice area; EOAi: Indexed effective orifice area; LVOT: Left ventricular outflow tract; PERIGON: PERIcardial SurGical AOrtic Valve ReplacemeNt Pivotal Trial; PPM: Prosthesis-patient mismatch; TTE: Transthoracic echocardiography; VARC-2: Valve Academic Research Consortium-2.

KEYWORDS:

• Prosthesis-patient mismatch
• body surface area
• epidemiology
• prosthetic valves
• AVR

Disclosure statement

M.D.V. has received a research grant from Medtronic, H.C.H has received institutional research funding from Abbott Vascular, Bayer, Boston Scientific, Edwards Lifesciences, Medtronic, and St. Jude Medical; and has been a consultant for Edwards Lifesciences, Medtronic, and Siemens Healthineers, S.J.H and A.P.K. are employees of Medtronic, R.J.M.K. has received a research grant from Medtronic, consultation and proctoring fees from Medtronic and LivaNova, and participates in speakers bureaus for Medtronic, LivaNova, and Edwards Lifesciences. R.H.H.G., R.A.F.D.L.V.W and P.A.V. have no conflict of interest to declare.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website

Additional information

Funding

PERIGON Pivotal trial is funded by Medtronic.