Vaquer et al. Ann. Intensive Care (2019) 9:112 https://doi.org/10.1186/s13613-019-0586-8 LETTER TO THE EDITOR RESPONSE Open Access When one cannot see the forest for the trees: femoral dP/dtmax, LVEF and pulse pressure in critically ill patients S. Vaquer1,2,3,4* , D. Chemla3,4 and X. Monnet4,5 Dear Editor, norepinephrine dose. In addition, changes in femoral dP/ Whether the peak rate of pressure rise (dP/dtmax) in dtmax were strongly related to changes in arterial pulse peripheral arteries is influenced by left ventricular (LV) pressure (PP) in each intervention and when all interven- contractility or by loading conditions remains controver- tions were pooled (each R > 0.90). Interestingly, Sharman sial. We, therefore, appreciate the letter by Monge-García et al. have also documented strong associations between et al. [1] and have read it with interest. radial dP/dtmax and brachial PP in various populations of Our colleagues challenge the use of LV ejection fraction non-critically ill patients [4, 5]. Since PP is mainly influ- (LVEF) as a marker of LV systolic function and its com- enced by arterial stiffness and stroke volume, and given parison with femoral dP/dtmax to assess the reliability of the fact that PP explained > 80% of the variance of femo- the femoral dP/dtmax to track changes in LV contractility ral dP/dtmax, we concluded that femoral dP/dtmax was [1]. We entirely agree that LVEF is not a pure marker of mainly influenced by pulsatile arterial load [3]. These LV contractility, as widely documented by others [2], and findings suggest that femoral dP/dtmax is highly sensitive as clearly acknowledged in the discussion section of our to changes in loading conditions, especially afterload, article [3]. Furthermore, we agree that the invasive meas- and thus may not be directly interchangeable with LV ure, LV end-systolic elastance (Ees), is the gold standard contractility. methodology to estimate LV contractility, but we were In previous work [6], our colleagues have documented unable to measure it for ethical and technical reasons. In a linear relationship between Ees and femoral dP/dtmax in our paper [3], we presented LVEF data, as is commonly 10 anesthetized pigs during different loading and contrac- done in similar studies, but in contrast to the inference tile conditions. However, while the authors present good of our colleagues’ letter [1], our conclusion was not based concordance results, the strength of this relationship upon LVEF results. was rather moderate (R2 = 0.33) [6]. To our knowledge, In our study [3], we measured femoral dP/dtmax by the only other experimental study documenting the link pulse contour analysis before and after varying, LV between contractility (Ees) and femoral dP/dtmax is Mori- systolic function (dobutamine infusion), preload (vol- mont et al. [7] who studied 6 anesthetized and mechani- ume expansion and passive leg-raising) and afterload cally ventilated pigs after endotoxin-induced shock and (norepinephrine) in 19 critically ill patients with car- norepinephrine infusion. In their work, authors reported diovascular failure [3]. Femoral dP/dtmax changed, not that Ees and femoral dP/dtmax were significantly, albeit only in response to dobutamine infusion, but also fol- weakly correlated (R = 0.51, i.e., R2 = 0.26). Therefore, two lowing changes in cardiac loading, particularly fol- independent experimental studies have documented that lowing changes in afterload induced by variations in factors other than LV contractility (Ees) explain the vast majority (67% to 74%) of the variance of femoral dP/dtmax in response to LV contractility and ventricular loading *Correspondence: sergivaquer@gmail.com 1 Servei de Medicina Intensiva, Centre de Crítics, Corporació Sanitària changes [6, 7]. Universitària Parc Taulí, Parc Taulí 1, 08208 Sabadell, Spain Full list of author information is available at the end of the article © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Vaquer et al. Ann. Intensive Care (2019) 9:112 Page 2 of 2 In conclusion, our results showed that changes in Author details 1 Servei de Medicina Intensiva, Centre de Crítics, Corporació Sanitària femoral dP/dtmax are essentially analogous to changes in Universitària Parc Taulí, Parc Taulí 1, 08208 Sabadell, Spain. 2 Departament de femoral PP and therefore subject to the same dependence Medicina, Facultat de Medicina, Universitat Autònoma de Barcelona, Passeig to variations in cardiac loading conditions, especially de la Vall d´Hebron 119, 08035 Barcelona, Spain. 3 Service d’explorations fonc- tionnelles multidisciplinaires bi‑site Béclère‑Bicêtre, AP-HP, Hôpitaux universi- pulsatile arterial load. Our hypothesis is consistent with taires Paris-Sud, 78, rue du Général Leclerc, 94270 Le Kremlin‑Bicêtre, France. the previous results obtained at the upper arm level in 4 INSERM‑UMR_S999 LabEx – LERMIT, Hôpital Marie-Lannelongue, 92350 Le non-critically ill patients [4, 5] and with results from two Plessis‑Robinson, France. 5 Service de médecine intensive ‑ réanimation, Hôpi- tal Bicêtre, AP-HP, Hôpitaux universitaires Paris-Sud, 78, rue du Général Leclerc, independent experimental studies, having failed to dem- 94270 Le Kremlin‑Bicêtre, France. onstrate strong correlation between LV contractility (Ees) and femoral dP/dtmax in various experimental settings [6, Received: 10 August 2019 Accepted: 21 September 2019 7]. Acknowledgements We are grateful to Dr. David A. Green (KBRwyle for the European Astronaut Centre & King’s College London) for his help in the English proofing of this References letter. 1. Monge García MI, Cecconi M, Pinsky MR. Assessing left ventricular systolic function with ejection fraction: using a double-edged knife as a hammer. Authors’ contributions Ann Intensive Care; 2019. SV, DCH and XM contributed equally to the writing of this letter. All authors 2. Robotham JL, Takata M, Berman M, et al. Ejection fraction revisited. Anes- read and approved the final manuscript. thesiology. 1991;74:172–83. 3. Vaquer S, Chemla D, Teboul J-L, et al. Influence of changes in ventricular Funding systolic function and loading conditions on pulse contour analysis- The original study was supported by the clinical institutions where it was derived femoral dP/dtmax. Ann Intensive Care. 2019;9:61. developed. The research team performed this study as part of their regular 4. Sharman JE, Qasem AM, Hanekom L, et al. Radial pressure waveform dP/ clinical work. dtmax is a poor indicator of left ventricular systolic function. Eur J Clin Invest. 2007;37:276–81. Availability of data and materials 5. Sharman JE, Marwick TH: Re: Tartière et al, Noninvasively determined The datasets used and/or analyzed during the original study are available from radial dP/dt is a predictor of mortality in patients with heart failure (Am the corresponding author upon request. Heart J 2008;155:758–63). Am Heart J. 2008;156:e21; author reply e23. 6. Garcia MI, Jian Z, et al. Performance comparison of ventricular and arterial Ethics approval and consent to participate dP/dtmax for assessing left ventricular systolic function during different The original study was approved by local ethics committees of both par- experimental loading and contractile conditions. Crit Care. 2018;22:325. ticipating institutions (Comitè Ètic d’Investigació Clínica de la Corporació 7. Morimont P, Lambermont B, Desaive T, et al. Arterial dP/dtmax accurately Sanitària Parc Taulí CEIC2013616 and Comité pour la protection des personnes reflects left ventricular contractility during shock when adequate vascular Ile-de-France VII). All patients or next of kin gave their consent to participate filling is achieved. BMC Cardiovasc Disord. 2012;12:13. to the study. Publisher’s Note Consent for publication Springer Nature remains neutral with regard to jurisdictional claims in pub- Not applicable lished maps and institutional affiliations. Competing interests Prof. XM is a member of the medical advisory board of Pulsion Medical Sys- tems. The remaining authors declare that they have no competing interests.