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Stroke Work (stroke + work)
Selected AbstractsAtrial Versus Ventricular Cannulation for a Rotary Ventricular Assist DeviceARTIFICIAL ORGANS, Issue 9 2010Daniel Timms Abstract The ventricular assist device inflow cannulation site is the primary interface between the device and the patient. Connecting these cannulae to either atria or ventricles induces major changes in flow dynamics; however, there are little data available on precise quantification of these changes. The objective of this investigation was to quantify the difference in ventricular/vascular hemodynamics during a range of left heart failure conditions with either atrial (AC) or ventricular (VC) inflow cannulation in a mock circulation loop with a rotary left VAD. Ventricular ejection fraction (EF), stroke work, and pump flow rates were found to be consistently lower with AC compared with VC over all simulated heart failure conditions. Adequate ventricular ejection remained with AC under low levels of mechanical support; however, the reduced EF in cases of severe heart failure may increase the risk of thromboembolic events. AC is therefore more suitable for class III, bridge to recovery patients, while VC is appropriate for class IV, bridge to transplant/destination patients. [source] A Mathematical Model to Evaluate Control Strategies for Mechanical Circulatory SupportARTIFICIAL ORGANS, Issue 8 2009Lieke G.E. Cox Abstract Continuous flow ventricular assist devices (VADs) for mechanical circulatory support (MCS) are generally smaller and believed to be more reliable than pulsatile VADs. However, regarding continuous flow, there are concerns about the decreased pulsatility and ventricular unloading. Moreover, pulsatile VADs offer a wider range in control strategies. For this reason, we used a computer model to evaluate whether pulsatile operation of a continuous flow VAD would be more beneficial than the standard constant pump speed. The computer model describes the left and right ventricle with one-fiber heart contraction models, and the systemic, pulmonary, and coronary circulation with lumped parameter hemodynamical models, while the heart rate is regulated with a baroreflex model. With this computer model, both normal and heart failure hemodynamics were simulated. A HeartMate II left ventricular assist device model was connected to this model, and both constant speed and pulsatile support were simulated. Pulsatile support did not solve the decreased pulsatility issue, but it did improve perfusion (cardiac index and coronary flow) and unloading (stroke work and heart rate) compared with constant speed. Also, pulsatile support would be beneficial for developing control strategies, as it offers more options to adjust assist device settings to the patient's needs. Because the mathematical model used in this study can simulate different assist device settings, it can play a valuable role in developing mechanical circulatory support control strategies. [source] Effects of combined inhibition of the Na+,H+ exchanger and angiotensin-converting enzyme in rats with congestive heart failure after myocardial infarctionBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2005Hartmut Ruetten We investigated the single vs the combined long-term inhibition of Na+,H+ exchanger-1 (NHE-1) and ACE in rats with congestive heart failure induced by myocardial infarction (MI). Rats with MI were randomized to receive either placebo, cariporide (3000 p.p.m. via chow), ramipril (1 mg kg,1 day,1via drinking water) or their combination for 18 weeks starting on day 3 after surgery. Cardiac morphology and function was assessed by echocardiography and by means of a 2.0 F conductance catheter to determine left ventricular (LV) pressure volume relationships. MI for 18 weeks resulted in an increase in LV end-diastolic diameter (LVDed) in the placebo-treated group when compared to sham (placebo: 1.1±0.04 cm; sham: 0.86±0.01; P<0.05). Combined inhibition of NHE-1 and ACE, but not the monotherapies, significantly reduced LVDed (1.02±0.02 cm). Preload recruitable stroke work (PRSW), dp/dtmax (parameter of systolic function) and end-diastolic pressure volume relationship (EDPVR, diastolic function) were significantly impaired in placebo-treated MI group (PRSW: 39±7 mmHg; dp/dtmax: 5185±363 mmHg s,1; EDPVR: 0.042±0.001 mmHg ,l,1; all P<0.05). Cariporide treatment significantly improved PRSW (64±7 mmHg), dp/dtmax (8077±525 mmHg s,1) and EDPVR (0.026±0.014 mmHg ,l,1), and reduced cardiac hypertrophy in rats with MI. Combined inhibition of NHE-1 and ACE had even a more pronounced effect on PRSW (72±5 mmHg) and EDPVR (0.026±0.014 mmHg ,l,1), as well as cardiac hypertrophy that, however, did not reach statistical significance compared to cariporide treatment alone. The NHE-1 inhibitor cariporide significantly improved LV remodeling and function in rats with congestive heart failure induced by MI. The effect of cariporide was comparable or tended to be stronger (e.g. systolic function) compared to ramipril. Combined treatment with cariporide and ramipril tended to be more effective on LV remodeling in rats with heart failure than the single treatments. Thus, inhibition of the NHE-1 may be a promising novel therapeutic approach for the treatment of congestive heart failure. British Journal of Pharmacology (2005) 146, 723,731. doi:10.1038/sj.bjp.0706381 [source] Development of a new semi-quantitative non-invasive method for evaluating ventricular stroke workCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2009Mu-Hua Cheng Abstract Background and aim:, Ventricular stroke work (SW) is one of the best indices to evaluate ventricular function, however, the SW monitoring mainly depends on the invasive method with the artery catheter. In this paper, our aim is to develop a new semi-quantitative non-invasive method for evaluating ventricular SW. Methods:, The multiple gated cardiac blood pool imaging was done in 25 patients with coronary artery disease and 12 normal controls. A new parameter, the relative stroke work (RSW) of left ventricle, was calculated using an equation derived from the principle of hydrodynamics. The left ventricular SW was analyzed by stroke volume (SV) and mean arterial pressure. Ejected fraction (EF), peak ejected rate (PER) and peak filling rate (PFR) were gotten with the routine software in imaging device. Results:, The left ventricular RSW was linearly correlated with the SW. The RSW was related to the SV, EF, PER and PFR of the left ventricle. The RSW had regressive relation with SV and PER. The RSW in patients, same as SW, SV, EF, PFR and PER, was noticeably lower than that in normal controls, P<0·01. Conclusion:, The RSW is a potential and valuable clinical index for evaluation of the ventricular function. [source] Influence of right ventricular pre- and afterload on right ventricular ejection fraction and preload recruitable stroke work relationCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 1 2001Wolfram Burger When right ventricular (RV) afterload is abnormally increased, it correlates inversely with right ventricular ejection fraction (RVEF). We tested, whether this would be different with normal afterload. Additionally, we investigated whether previous studies on the slope of RV preload recruitable stroke work (SW) relation, which used rather non-physiological measures to change RV preload, could be transferred to more physiological loading conditions. RV volumes were determined by thermodilution in 16 patients with stable coronary artery disease and normal pulmonary artery pressure (PAP) at rest. Pre- and afterload were varied by body posture, nitroglycerin (NTG) application and by exercise at different body positions. At rest, the change from recumbent to sitting position decreased PAP, cardiac index (Ci), RV diastolic and systolic volumes, and RVEF. Additionally, mean pulmonary artery pressure (MPAP) correlated positively with both RVEF and cardiac index. After correction for mathematical coupling, the RV preload recruitable SW relation was: right ventricular stroke work index (RVSWi) (103 erg m,2)= 8·1 × (RV end-diastolic volume index ,4·9), with n=96, r=0·57, P,0·001. Exercise abolished this correlation and led to an inverse correlation between RV end-systolic volume (ESV) and RVSW. In conclusion, (i) RVEF correlates positively with RV afterload when afterload varies within normal range; (ii) the slope of the RV preload recruitable SW relation, which is obtained at steady state under normal loading conditions, is substantially flatter than previously described for dynamic changes of RV preload. With increasing afterload, preload loses its determining effect on RV performance, while afterload becomes more important. This puts earlier assumptions of an afterload independent RV preload recruitable SW relation into question. [source] Does Simultaneous Antegrade and Retrograde Cardioplegia Improve Functional Recovery and Myocardial Homeostasis?JOURNAL OF CARDIAC SURGERY, Issue 5 2000F.E.T.C.S., M. J. Jasinski M.D. Methods: Forty patients who underwent elective coronary artery bypass grafting (CABG) were prospectively assigned to two clinically matched groups and analyzed in respect to cardioplegia protocol. Group I consisted of 24 patients who received continuous retrograde blood cardioplegia; Group II consisted of 16 patients who received simultaneous continuous ante- and retrograde cardioplegia. Hydrogen ion release, carbon dioxide, lactate concentration oxygen content, and oxygen extraction were measured from coronary sinus effluent and from the arterial line before and after cross-clamping of the aorta. Median changes of these parameters were reported. Cardiac output was measured and left and right ventricle stroke works were calculated. Incidence of low cardiac output, ventricular fibrillation, raised cardiac enzymes, and ischemic changes on electrocardiogram (ECG) were noted. Results: In the simultaneous group, oxygen content and oxygen extraction recovered well after cross-clamping. The same parameters did not recover to the same extent in the retrograde group. These changes were notable between groups. Hydrogen ion, carbon dioxide, and lactate releases were comparable between groups. Trend toward better recovery of left ventricle stroke work index was encountered in the simultaneous group. Conclusions: Viability of myocardium measured with oxygen utilization and functional recovery is better preserved with simultaneous antegrade and retrograde cardioplegia. However, there is no difference in anaerobic metabolism markers. Thus simultaneous ante- and retrograde cardioplegia is probably advantageous over retrograde alone. [source] | ||||||||||