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This study assesses positional changes in cardiac power output and stroke work compared with classic hemodynamic variables, measured before and after elective coronary artery bypass graft surgery. The hypothesis was that cardiac power output was altered in relation to cardiac stunning. The study is a retrospective analysis of data from two previous studies performed in a tertiary care university hospital. Thirty-six patients scheduled for elective coronary artery bypass graft surgery, with relatively preserved left ventricular function, were included. A pulmonary artery catheter and a radial artery catheter were placed preoperatively. Cardiac power output and stroke work were calculated through thermodilution both supine and standing prior to induction of anesthesia and again day one postoperatively. Virtually all systemic hemodynamic parameters changed significantly from pre- to postoperatively, and from supine to standing. Cardiac power output was maintained at 0.9-1.0 (±0.3) W both pre- and postoperatively and from supine to standing on both days. Stroke work fell from pre- to postoperatively from 1.1 to 0.8 J (P < 0.001), there was a significant fall in stroke work with positional change preoperatively from 1.1 to 0.9 J (P < 0.001). Postoperatively the stroke work remained at 0.8 J despite positional change. Cardiac power output was the only systemic hemodynamic variable which remained unaltered during all changes. Stroke work appears to be a more sensitive marker for temporary cardiovascular dysfunction than cardiac power output. Further studies should explore the relationship between stroke work and cardiac performance and whether cardiac power output is an autoregulated intrinsic physiological parameter., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

Cardiac surgery patients are urged to resume light physical activity on the first postoperative day, even if cardiac function may not have recovered fully after the operation. To elucidate the postoperative recovery process, we examined cardiac surgery patients with exercise echocardiography before and on the first day after the operation. Patients undergoing on-pump coronary artery bypass grafting were examined with echocardiography during semirecumbent cycle exercise. Patients exercised for five minutes at 10 W intensity and five minutes at 30 W intensity in bed with the upper body supported to approximately 30°. Fourteen patients were studied. Mitral annulus excursion and pulsed wave Doppler from the left ventricular outflow tract indicated postoperatively reduced cardiac stroke volume. Early diastolic tissue velocities of the mitral annulus were reduced, and early trans-mitral flow velocity was increased. The ratio between early mitral flow velocity and early diastolic mitral tissue velocity was increased postoperatively, indicating impaired left ventricular relaxation and increased left atrial pressure. Postoperative systolic mitral annulus tissue velocities were similar to preoperative velocities, indicating maintained systolic function. Postoperative exercise was associated with improvements in myocardial function indices and cardiac stroke volume similar to preoperative improvements. There were no signs of further deterioration in myocardial function during 30 W exercise. In summary, reduced left ventricular diastolic function after surgery resulted in reduced cardiac stroke volume, increased left atrial pressure and a higher rate of perceived exertion on the first postoperative day., (© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.)

Objective: To assess the effect of coronary artery bypass grafting with cardiopulmonary bypass on muscle perfusion, oxygen extraction, and lactate release during postoperative rest and exercise., Design: Prospective observational study., Setting: University hospital., Participants: Patients undergoing planned coronary artery bypass grafting., Intervention: Knee-extensor exercise before and after coronary artery bypass grafting., Measurements and Main Results: Femoral artery blood flow was measured with ultrasound. Femoral vein blood and arterial blood were sampled at rest and during light exercise and were analyzed for hemoglobin, lactate, oxygen saturation, and oxygen partial pressure. Fourteen patients were tested before and after surgery. The arterial lactate concentrations were increased after surgery, both at rest and during light exercise. Resting arterial lactate increased from 0.65 (0.5-0.8) to 1.0 (0.9-1.3) mmol/L (p=0.01) (median and interquartile range). Furthermore, lactate was released from the leg even during postoperative rest, and the release of lactate was increased during postoperative exercise. There were no significant differences between the preoperative and postoperative femoral artery blood flow. Femoral vein oxygen partial pressure was reduced significantly after surgery, indicating reduced muscle cell oxygen partial pressure., Conclusions: The patients had elevated anaerobic metabolism in skeletal muscle after surgery to compensate for anemia. Lactate was released from the leg into the general circulation during postoperative rest and exercise. The postoperatively reduced hemoglobin concentration of 11.4 mg/dL (10.6-12.3) resulted in increased anaerobic metabolism and release of lactate from skeletal muscle. The authors concluded that coronary artery bypass grafting patients are susceptible to anaerobic metabolism even with maintained peripheral blood flow., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aims: Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts., Methods and Results: Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition., Conclusion: Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

Objective: The aim of the study was to evaluate the impact of an additional subcutaneous suture line on the incidence of postoperative (p.o.) infection at the vena saphena magna harvesting site (VSMHS) after coronary artery bypass grafting (CABG)., Methods: Two hundred and forty three patients undergoing CABG were included. Patients in Group A (n = 119) all operated by one physical assistant (PA) were prospectively randomised into Group A1 (n = 59) receiving intracutaneous closure suture alone whereas 60 patients (Group A2) received an additional subcutaneous suture line. Group B (n = 120), operated by surgical residents, served as control population. All patients were due to follow-up at six weeks p.o., Results: Subcutaneous suture did not impact the p.o. infection rate (A2 vs. A1; 4/60 vs. 2/59, n.s.). A significant lower p.o. infection rate was observed in Group A vs. Group B (6/119 (5%) vs. 15/120 (13%) p < 0.05)., Conclusion: Subcutaneous suture did not impact the p.o. infection rate at VSMHS. The infection rate observed in patients operated by an experienced PA was significantly lower than in patients operated by various surgical residents.

Early mobilization after cardiac surgery induces a marked reduction in mixed venous oxygen saturation (Svo2). Using pulmonary artery catheters and indirect calorimetry, we investigated the effects of exercise and postural change on cardiac index (CI) and Svo2 before and on the first morning after coronary artery bypass surgery. Sixteen patients with an ejection fraction >0.50 were studied at rest, during supine bicycle exercise, and during passive standing. Supine cycling at 30 W increased CI by 1.5 +/- 0.8 L x min(-1) x m(-2) before and 0.9 +/- 0.7 L x min(-1) x m(-2) after surgery (P < 0.05), whereas Svo2 was reduced from 80% +/- 4% at rest to 63 +/- 6% preoperatively (P < 0.05) and from 71% +/- 5% to 46% +/- 11% postoperatively (P < 0.05). Passive standing reduced CI by 0.8 +/- 0.5 L x min(-1) x m(-2) before and 0.3 +/- 0.4 L x min(-1) x m(-2) after surgery (P < 0.05). Svo2 was reduced from 79% +/- 5% to 64% +/- 7% preoperatively (P < 0.05) and from 72% +/- 6% to 60% +/- 6% postoperatively (P < 0.05). The exercise challenge revealed an altered cardiovascular response after surgery, causing a larger reduction in Svo2 for the same workload. Passive standing significantly reduced Svo2 both days, but this effect was less pronounced after surgery. The response to postural change and exercise was altered after surgery and may both contribute to the reduction in Svo2 during postoperative mobilization.

Objectives: The use of cardiopulmonary bypass in coronary artery bypass grafting (CABG) may contribute to the postoperative inflammatory response. The molecular chaperone heat-shock protein (HSP) 70 may be induced by ischemia, and has been detected both in the myocardium and in the circulation after CABG. In vitro, extracellular HSP70 may activate both innate and adaptive immunity. Hypothesizing that use of cardiopulmonary bypass (CPB) leads to more circulating HSP70, we explored the release of it in 10 patients undergoing CABG with the use of CPB, and in 10 patients undergoing off-pump surgery CABG (OPCAB)., Methods: Blood samples were taken preoperatively, twice peroperatively, 2 and 6 h postoperatively and the next day. Serum analyses were performed by means of immunoassays., Results: We detected a significant difference in postoperative circulating HSP70 between on-pump and off-pump patients (median peaks of 2849 and 756 pg/ml, respectively, P < 0.01 2 h postoperatively). Interleukin-6 and -8 increased in all patients, without significant differences between the groups. Serum interleukin-10 increased at the end of the operation in 7 of 10 patients operated with cardiopulmonary bypass (median 51.7 pg/ml), but in none of the off-pump patients. Furthermore, in the first group, interleukin-10 correlated with the HSP70 concentration at the end of the operation, r = 0.75, P < 0.05. Serum markers of myocardial damage were higher in conventional than off-pump patients on day 1 postoperatively: median cardiac Troponin T was 0.358 and 0.126 microg/l, respectively, P < 0.01. Correspondingly, median creatine kinase-MB was 23.6 and 7.8 microg/l in on-pump and off-pump patients, respectively, P < 0.001. Peak HSP70 correlated with both Troponin T and creatine kinase-MB measured on day 1., Conclusions: Significantly more HSP70 was released into the circulation following conventional than following off-pump CABG. Circulating HSP70 may indicate cellular stress or damage. Furthermore, HSPs are suggested as immunoregulatory agents, and may be important in the host defence postoperatively.

Low-molecular-weight heparin and acetyl salicylic acid have become an established treatment for unstable angina. A retrospective study on our database of one year was carried out to see what impact preoperative low-molecular-weight heparin versus none had on the postoperative course of 473 patients having coronary surgery exclusively. Apart from the fact that the low-molecular-weight heparin patients had a higher New York Heart Association classification and marginally more grafts, longer bypass and cross-clamp time, the preoperative characteristics and surgery of the two groups were similar. The low-molecular-weight heparin group had twice as many (9.7% versus 4.7%) re-operations for bleeding, 46% versus 26% had blood transfusion and 22.3% versus 12.6% plasma transfusion. The postoperative outcome was otherwise similar. Preoperative treatment of unstable angina with low-molecular-weight heparin carries a definite risk of postoperative bleeding. Although this study did not reveal any serious consequences, bleeding, transfusions and re-operations are associated with infections, wound healing problems and death. The indications and length of treatment with low-molecular-weight heparin in unstable angina patients have to be appropriate and the perioperative management of these patients has to address the bleeding tendency.

Background: There is significant uncertainty regarding the timing of onset of cardiovascular stunning after cardiac surgery. Cardiovascular stunning is affecting both contractility (Ees) and arterial load. Arterial load may be represented by arterial elastance (Ea) and participates in ventriculo-arterial coupling through the Ea/Ees ratio, giving information on efficiency and performance. An alternative approach to ventriculo-arterial interaction is oscillatory power fraction (OPF). The aim of this study was to investigate the immediate beat-to-beat effects of on-pump coronary artery bypass graft (CABG) surgery on contractility, cardiac power parameters, arterial load and ventriculo-arterial coupling as well as classical haemodynamic parameters.Methods: We included 41 patients scheduled for fast-track CABG surgery. Measurements were taken before and after cardiopulmonary bypass. A flow and pressure curve were recorded from transoesophageal pulsed wave Doppler and a radial artery catheter, respectively. This enabled the calculation of stroke work, total cardiac energy delivery, OPF and Ea/Ees ratio. Routine haemodynamic monitoring provided the classical haemodynamic parameters.Results: Immediately after cardiopulmonary bypass there was no firm evidence for alterations in contractility, stroke work, stroke volume or arterial elastance. Ea/Ees ratio and OPF remained unchanged.Conclusions: There was no evidence for clinically relevant cardiac stunning or altered arterial load immediately after cardiopulmonary bypass for CABG surgery. The unchanged Ea/Ees ratio and OPF are indicating unchanged cardiac efficiency before and after cardiopulmonary bypass. This indicates that in elective CABG patients cardiovascular stunning is perhaps a phenomenon of inflammation and not immediate ischaemia-reperfusion injury or mechanical handling. [ABSTRACT FROM AUTHOR]

Summary: The rate of energy transfer from the left ventricle to the aorta is viewed in terms of mean power (MP) and total power (TP). The difference between MP and TP is due to the pulsatility of the circulation and is known as oscillatory power (OP). OP is considered the energy spent to accelerate the blood flow. The aim of this study was to investigate the baseline left ventricular oscillatory power fraction (OP/TP) and how this was affected by acute cardiovascular dysfunction and altered preload. Twenty‐eight patients undergoing elective coronary artery bypass graft surgery were included. Before administration of anaesthesia, we simultaneously recorded an arterial pressure curve and instantaneous cardiac outflow with pulsed wave Doppler. Postoperatively, prior to extubation, these measurements were repeated in neutral, Trendelenburg and reverse‐Trendelenburg position. The final measurements were taken on the awake patient the day after the operation. TP is the mean of the instantaneous product of the flow and pressure curves. MP was calculated by multiplying mean arterial pressure with mean cardiac output. The oscillatory power fraction is therefore calculated as (TP‐MP)/TP. The oscillatory power fraction in neutral position decreased from 23% preoperatively to 16% immediately postoperatively (P<0·001) and increased again to 19% the first postoperative day (P = 0·001). The oscillatory power fraction also increased from 16% in neutral to 19% in Trendelenburg (P = 0·001) and decreased comparing to neutral, to 14% in reverse‐Trendelenburg (P = 0·04). The oscillatory power fraction is situation‐dependent and is influenced by both the operation and the altered preload. [ABSTRACT FROM AUTHOR]