BackgroundThe aim of this study was to assess the relationship between extracorporeal blood flow (EBF) and left ventricular (LV) performance during venoarterial extracorporeal membrane oxygenation (VA ECMO) therapy.MethodsFive swine (body weight 45 kg) underwent VA ECMO implantation under general anesthesia and artificial ventilation. Subsequently, acute cardiogenic shock with signs of tissue hypoxia was induced. Hemodynamic and cardiac performance parameters were then measured at different levels of EBF (ranging from 1 to 5 L/min) using arterial and venous catheters, a pulmonary artery catheter and a pressure–volume loop catheter introduced into the left ventricle.ResultsMyocardial hypoxia resulted in a decline in mean (±SEM) cardiac output to 2.8 ± 0.3 L/min and systolic blood pressure (SBP) to 60 ± 7 mmHg. With an increase in EBF from 1 to 5 L/min, SBP increased to 97 ± 8 mmHg (P < 0.001); however, increasing EBF from 1 to 5 L/min significantly negatively influences several cardiac performance parameters: cardiac output decreased form 2.8 ± 0.3 L/min to 1.86 ± 0.53 L/min (P < 0.001), LV end-systolic volume increased from 64 ± 11 mL to 83 ± 14 mL (P < 0.001), LV stroke volume decreased from 48 ± 9 mL to 40 ± 8 mL (P = 0.045), LV ejection fraction decreased from 43 ± 3 % to 32 ± 3 % (P < 0.001) and stroke work increased from 2096 ± 342 mmHg mL to 3031 ± 404 mmHg mL (P < 0.001). LV end-diastolic pressure and volume were not significantly affected.ConclusionsThe results of the present study indicate that higher levels of VA ECMO blood flow in cardiogenic shock may negatively affect LV function. Therefore, it appears that to mitigate negative effects on LV function, optimal VA ECMO blood flow should be set as low as possible to allow adequate tissue perfusion.

IntroductionVeno-arterial extracorporeal life support (ECLS) is increasingly being used to treat rapidly progressing or severe cardiogenic shock. However, it has been repeatedly shown that increased afterload associated with ECLS significantly diminishes left ventricular (LV) performance. The objective of the present study was to compare LV function and coronary flow during standard continuous-flow ECLS support and electrocardiogram (ECG)-synchronized pulsatile ECLS flow in a porcine model of cardiogenic shock.MethodsSixteen female swine (mean body weight 45 kg) underwent ECLS implantation under general anesthesia and artificial ventilation. Subsequently, acute cardiogenic shock, with documented signs of tissue hypoperfusion, was induced by initiating global myocardial hypoxia. Hemodynamic cardiac performance variables and coronary flow were then measured at different rates of continuous or pulsatile ECLS flow (ranging from 1 L/min to 4 L/min) using arterial and venous catheters, a pulmonary artery catheter, an LV pressure-volume loop catheter, and a Doppler coronary guide-wire.ResultsMyocardial hypoxia resulted in declines in mean cardiac output to 1.7±0.7 L/min, systolic blood pressure to 64±22 mmHg, and LV ejection fraction (LVEF) to 22±7%. Synchronized pulsatile flow was associated with a significant reduction in LV end-systolic volume by 6.2 mL (6.7%), an increase in LV stroke volume by 5.0 mL (17.4%), higher LVEF by 4.5% (18.8% relative), cardiac output by 0.37 L/min (17.1%), and mean arterial pressure by 3.0 mmHg (5.5%) when compared with continuous ECLS flow at all ECLS flow rates (P<0.05). At selected ECLS flow rates, pulsatile flow also reduced LV end-diastolic pressure, end-diastolic volume, and systolic pressure. ECG-synchronized pulsatile flow was also associated with significantly increased (7% to 22%) coronary flow at all ECLS flow rates.ConclusionECG-synchronized pulsatile ECLS flow preserved LV function and coronary flow compared with standard continuous-flow ECLS in a porcine model of cardiogenic shock.

Despite the urgent need for experimental research in the field of acute heart failure and, particularly cardiogenic shock, currently there are only limited options in large animal models enabling research using devices applied to human subjects. The majority of available models are either associated with an unacceptably high rate of acute mortality or are incapable of developing sufficient severity of acute heart failure. The objective of our research was to develop a novel large animal model of acute severe cardiogenic shock. Advanced left ventricular dysfunction was induced by global myocardial hypoxia by perfusing the upper body (including coronary arteries) with deoxygenated venous blood. The model was tested in 12 pigs: cardiogenic shock with signs of tissue hypoxia developed in all animals with no acute mortality. Cardiac output decreased from a mean (± SD) of 6.61±1.14 l/min to 2.75±0.63 l/min, stroke volume from 79.7±9.8 ml to 25.3±7.8 ml and left ventricular ejection fraction from 61.2±4.3 % to 17.7±4.8 % (P≤0.001 for all comparisons). In conclusion, the porcine model of acute cardiogenic shock developed in the present study may provide a basis for studying severe left ventricular dysfunction, low cardiac output and hypotension in large animals. The global myocardial hypoxia responsible for the decrease in cardiac contractility was not associated with acute death in this model.

Extracorporeal membrane oxygenation in veno-arterial configuration (VA-ECMO) is a method widely used to support circulation during the most severe conditions of heart failure or refractory cardiac arrest. It frequently bridges this otherwise fatal status to recovery, therapeutic intervention or other circulatory support. However, the use of VA-ECMO in critical situations of severely impaired heart function is associated with specific limitations. One common complication is left ventricular overload and distension, primarily due to the increased afterload caused by extracorporeal blood flow. To date, various techniques has been proposed to decrease left ventricular distension and improve its function, including insertion of intra-aortic balloon pump or percutaneous left ventricular assist device, left atrial and left ventricular venting, or switch to surgically inserted left ventricular support with or without oxygenator. The present review summarizes current minimally invasive approaches to unload overloaded left ventricle during VA-ECMO support.

Femoral cannulation is a minimally invasive method which is an alternative method for central cannulation. This review focuses on the parameters and features of the available peripheral cannulas. Nowadays there exist many peripheral cannulas in a variety of sizes, configurations and lengths to meet the specific needs of the patients. Modern cannulas are strong, thin-walled and one piece reinforced constructions. Furthermore, modern cannulas are manufactured from a biocompatible material and surface coatings are applied to the cannulas to reduce the activation of the clotting. When peripheral cannulas are applied, bleeding, thrombosis and hemolysis are the most common complications.