Pump flow setting and assessment of unloading in clinical practice.

The rationale for mechanical circulatory support (MCS) in cardiogenic shock is to restore cardiac output in selected patients when critically low or in case of refractory cardiac arrest. Furthermore, an MCS device that moves blood from either the left atrium or the left ventricle to the systemic circulation will potentially unload the ventricle. These devices are used alone or in combination with venoarterial extracorporeal membrane oxygenation (VA-ECMO). If a left-sided Impella device is used, it should be run at the highest possible performance level during treatment while avoiding suction events. When combined with VA-ECMO, the Impella device should be run at a lower performance level, ensuring sufficient left ventricular emptying but avoiding suction. Continuous monitoring is pivotal and patients managed outside the catheterization laboratory should be monitored with an arterial line, a central venous catheter, frequent use of pulmonary artery catheters and regular imaging by transthoracic echocardiogram.

Microfluidic approaches for the assessment of blood cell trauma: a focus on thrombotic risk in mechanical circulatory support devices.

INTRODUCTION: Mechanical circulatory support devices (MCSDs) are emerging as a valuable therapeutic option for the management of end-stage heart failure. However, although recipients are routinely administered with anti-thrombotic (AT) drugs, thrombosis persists as a severe post-implant complication. Conventional clinical assays and coagulation markers demonstrate partial ability in preventing the onset of thrombosis. Through years, different laboratory techniques have been proposed as potential tools for the evaluation of platelets' hemostatic response in MCSD recipients. Most rely on platelet aggregation tests; they are performed in static or low shear conditions, neglecting the prominent contribution of MCSD shear-induced mechanical load in enhancing platelet activation (PA). On the other hand, those tests able to account for shear-induced PA have limited possibility of effective clinical translation. AIMS AND METHODS: Advances on this side have been addressed by microfluidic technology. Microfluidic devices have been developed for AT drug monitoring under flow, able to replicate physiological and/or constant shear flow conditions in vitro. In this paper, we present a newly developed microfluidic platform able to expose platelets to MCSD-specific dynamic shear stress patterns. We performed in vitro tests circulating human platelets in the microfluidic platform and quantifying the dynamics of PA by means of the Platelet Activity State (PAS) assay. RESULTS: Our results prove the feasibility of using microfluidics for the diagnosis of MCSD-related thrombotic risk. This study paves the way for the development of a miniaturized point-of-care device for monitoring AT drug regimen. Such a system may have significant impact on limiting the incidence of thrombosis in MCSD recipients.

Dynamic assessment of 'valvular reserve capacity' in patients with rheumatic mitral stenosis.

AIMS: Mitral stenosis (MS) may exhibit a dynamic valvular reserve. When resting gradients and systolic pulmonary pressure (sPAP) do not reflect the real severity of the disease, a dynamic evaluation becomes necessary. The aim of the study was to assess the clinical utility of exercise echocardiography in symptomatic patients with apparently subcritical MS. METHODS AND RESULTS: One hundred and thirty consecutive patients were referred for symptomatic MS. Patients with unimpressive resting MVA (>1-1.5 cm(2)) and mean PG (≥5-9 mmHg) underwent exercise echocardiography. Cardiac performance and mitral indices (MVA, peak/mean PG, sPAP) were measured. Exhaustion of valvular reserve capacity under exercise was defined as appearance of symptoms and sPAP > 60 mmHg. Forty-six patients (35%) (age: 53 ± 10 years; 74%, female) with resting MVA (1.2 ± 0.36 cm(2)), mean PG (6.8 ± 2.7 mmHg), and sPAP (38 ± 7 mmHg) inconsistent with symptoms underwent stress echocardiography. Exercise was stopped for dyspnoea (76%) or fatigue (24%). At peak workloads (57.2 ± 21.8 Watts), increased mean PG (17.2 ± 4.8 mmHg, P< 0.001) and sPAP (67.4 ± 11.4 mmHg; P< 0.0001) were observed, without change in MVA (1.25 ± 0.4 cm(2); P= n.s.). At univariate analysis, predictors of adaptation to exercise were age (-0.345; P = 0.024), mean PG (0.339; P= 0.023), and sPAP (0.354; P= 0.024); at multivariate analysis, best predictor was resting mean PG, although correlation was poor (-0.339; P= 0.015). CONCLUSION: In MS with limiting symptoms despite unimpressive findings at rest, valvular capacity exhaustion should be tested on a dynamic background, as no single resting index can predict potential haemodynamic adaptation to exercise. In such context, the contribution of exercise echocardiography remains extremely valuable.

Cardiac index assessment by the pressure recording analytic method in unstable patients with atrial fibrillation.

OBJECTIVE: Most-Care (powered by the pressure-recording analytic method [PRAM]; Vytech HealthTM, Padova, Italy) is a minimally invasive cardiac output monitoring. This system already has been studied and validated in cardiac surgery and in children. It already showed a correlation with thermodilution methods in hemodynamically unstable patients. The purpose of this study was to confirm the reliability of cardiac index determinations by Most-Care in unstable patients with atrial fibrillation. DESIGN: A prospective study. SETTING: A teaching hospital. PARTICIPANTS: Forty-nine patients. INTERVENTIONS: Simultaneous cardiac index measurements by bolus thermodilution and by PRAM from a standard arterial access (radial and femoral) were obtained. The thermodilution cardiac index was calculated as the mean of 3 separate measurements. Because PRAM is a beat-to-beat monitoring system, the mean cardiac index of 12 consecutive beats was considered for the analysis. Correlations were calculated and differences compared by Bland-Altman analysis. MEASUREMENTS: Eight patients were excluded because the signal was altered by the arterial catheter resonance so that the study described the remaining 41 patients. The overall estimates of cardiac index measured by PRAM did not show agreement with the reference cardiac index by thermodilution (mean difference = 0.136 L/min/m(2) [0,43 L/min/m(2)-0.15 L/min/m(2)], with an upper limit of agreement of 1.94 L/min/m(2) and a lower limit of agreement of -1.665 L/min/m(2), respectively). The median (interquartile) value of cardiac index assessed by thermodilution was 2.42 L/min/m(2) (2.21-2.98 L/min/m(2)), and by PRAM it was 2.48 L/min/m(2) (1.80-3.00 L/min/m(2), p = 0.6). CONCLUSIONS: The authors concluded that PRAM did not compare well with thermodilution in unstable patients with atrial fibrillation.