Aortic dP/dtmax accurately reflects left ventricular contractility when effective preload independence is achieved

peer reviewe

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

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Arterial elastance and heart-arterial coupling in aortic regurgitation are determined by aortic leak severity

Background In aortic valve regurgitation (AR), aortic leak severity modulates left ventricle (LV) arterial system interaction. The aim of this study was to assess (1) how arterial elastance (E-a), calculated as the ratio of LV end-systolic pressure and stroke volume, relates to arterial properties and leak severity and (2) the validity of E-a/E-max (with E-max the slope of the-end-systolic pressure-volume relation) as a heart-arterial coupling parameter in AR. Methods and Results Our work is based on human data obtained from a study on vascular adaptation in chronic AR. These data allowed us to assess the parameters of a computer model of heart-arterial interaction. In particular, total peripheral resistance (R) and aortic leak severity-expressed as leak resistance (R-L,R-ao)-were quantified for different patient subgroups (group I/IIa/IIb: E-max = 2.15/0.62/0.47 mm Hg/mL; E-a = 1.24/0.66/0.90 mm Hg/mL; R = 1.9/0.6/0.85 mm Hg-s/mL, R-L,R-ao = 0.35/0.05/0.20 mm Hg-s/mL). A parameter study demonstrated that R-L,R-ao was the main determinant of E-a. With all other parameters constant, valve repair would increase E-a to 2.81, 1.08, and 1.54 mm Hg/mL in groups I,IIa, and IIb, respectively. For a given E-a/E-max, LV pump efficiency (estimated as the ratio of stroke work and LV systolic pressure-volume area) was lower than the theoretical predicted value, except for the simulations with intact aortic valve. Conclusions In AR(a) E-a is determined by aortic leak severity rather than by arterial system properties. Using E-a/E-max as a coupling parameter in general or as a mechanico-energetic regulatory parameter in particular is questionable

Early detection of abnormal left ventricular relaxation in acute myocardial ischemia with a quadratic model

Aims: The time constant of left ventricular (LV) relaxation derived from a monoexponential model is widely 12 used as an index of LV relaxation rate, although this model does not reflect the non-uniformity of ventricular 13 relaxation. This study investigates whether the relaxation curve can be better fitted with a “quadratic” model 14 than with the “conventional” monoexponential model and if changes in the LV relaxation waveform due to 15 acute myocardial ischemia could be better detected with the quadratic model. 16 Methods and results: Isovolumic relaxation was assessed with quadratic and conventional models during acute 17 myocardial ischemia performed in 6 anesthetized pigs. Mathematical development indicates that one parameter 18 (Tq) of the quadratic model reflects the rate of LV relaxation, while the second parameter (K) modifies the 19 shape of the relaxation curve. Analysis of experimental data obtained in anesthetized pigs showed that the shape 20 of LV relaxation consistently deviates from the conventional monoexponential decay. During the early phase of 21 acute myocardial ischemia, the rate and non-uniformity of LV relaxation, assessed with the quadratic function, 22 were significantly enhanced. Tq increased by 16% (p < 0.001) and K increased by 12% (p < 0.001) within 30 23 and 60 minutes, respectively, after left anterior descending (LAD) coronary artery occlusion. However, no 24 significant changes were observed with the conventional monoexponential decay within 60 minutes of ischemia. 25 Conclusions: The quadratic model better fits LV isovolumic relaxation than the monoexponential model and can 26 detect early changes in relaxation due to acute myocardial ischemia that are not detectable with conventional 27 methods

[How I treat … severe beta-blocker poisoning : pharmacological approaches and ECMO].

peer reviewedNous rapportons un cas d’intoxication sévère aux bêta-bloquants. Après l’échec des traitements pharmacologiques, la patiente a bénéficié d’une assistance circulatoire externe de type ECMO (ExtraCorporeal Membrane Oxygenation ou oxygénation par membrane extracorporelle). Nous discutons des traitements pharmacologiques conventionnels et des traitements qui ont émergé durant cette dernière décennie, comme l’insulinothérapie à haute dose et les émulsions lipidiques. L’ECMO a fait des progrès importants ces dernières années et est devenue, à l’heure actuelle, la méthode d’assistance circulatoire externe de première ligne en cas de défaillance cardiaque et/ou respiratoire. Nous verrons sa place dans la prise en charge de l’intoxication massive aux drogues cardiodépressives