Vertical displacement of the beating heart by the octopus tissue stabilizer: influence on coronary flow

Rapid cardiac ischemia detection with an epicardial graphene probe

Introduction

In this study, a new probe was designed to enable electrocardiography of a rotated heart during cardiac surgery when skin electrodes became non-functional. This probe adhered non-invasively to the epicardium and collected the ECG signal independently from the position of the heart. The study compared the accuracy of cardiac ischemia detection between classic skin and epicardial electrodes in an animal model.

Methods

Using six pigs, an open chest model was devised with cardiac ischemia induction by coronary artery ligation in two non-physiologic heart positions. Both the accuracy and the time of detection of electrocardiographic symptoms of acute cardiac ischemia were compared between skin and epicardial methods of signal collection.

Results

Heart rotation to expose either the anterior or the posterior wall resulted in a distortion or loss of the ECG signal collected by skin electrodes after coronary artery ligation, standard skin ECG monitoring did not reveal any ischemia symptoms. Attachment of an epicardial probe on the anterior and posterior walls helped in the recovery of the normal ECG wave. After ligation of the coronary artery, the epicardial probes recorded cardiac ischemia within 40 s.

Discussion

This study highlighted the effectiveness of ECG monitoring with epicardial probes in a rotated heart. It can be concluded that epicardial probes can detect the presence of acute ischemia of a rotated heart when skin ECG monitoring becomes ineffective.

Implementation of a beating heart system for training in off-pump and minimally invasive coronary artery bypass

Background

Several training devices have been developed to train anastomotic skills in off-pump coronary artery bypass grafting (OPCAB). However, assessment of trainees’ improvement remains challenging. The goal of this study was to develop a new practical scoring chart and investigate its reliability and utility for anastomotic skills in OPCAB and minimally invasive direct coronary artery bypass (MIDCAB).

Methods

A training device was used, which included a beating heart model installed in a dedicated box. A soft plastic tube was used as the left anterior descending artery, and a porcine ureter was used as the left internal mammary artery. Five cardiac surgery fellows (Fellows, > 5 year of surgical experience) and five residents or medical students (Residents, ≤ 5 year of surgical experience) were enrolled for this study. Before and after training, skills were evaluated using a scoring chart that took into account anastomotic time, leakage, shape, flow measurement, and self-estimation.

Results

Mean total score of all trainees was 15.4 ± 4.0 at pre-training and 18.5 ± 2.4 at post-training (P = 0.05). Before training, there was a significant difference in the total score between Fellows and Residents (18.6 ± 2.2 vs 12.2 ± 2.4 points, P = 0.002), which disappeared after training (19.4 ± 2.5 vs 17.6 ± 2.2 points, P = 0.262). Residents benefitted from training with improvements in their time, total score, score for time, score for flow and subtraction score; however, these effects were not seen in Fellows. The most evident training effect was improvement of self-estimation, which was also seen in Fellows.

Conclusions

Residents were most likely to derive benefit from these training models with regard to both efficiency and quality. Training models seem to have an important role in making surgeons feel more comfortable with the procedure.

Fast-Track Anaesthesia in Off-Pump Coronary Surgery: A Comparison of Normotensive and Hypertensive Patients

Objective

In this study, our aim was to investigate the efficacy and sufficiency of bispectral indeks (BIS) guided remifentanil-desflurane anaesthesia on intraoperative haemodynamic stability in both normotensive and hypertensive patients undergoing off-pump coronary artery bypass surgery.

Methods

Thirty adult, ASA I-III patients undergoing elective off-pump coronary surgery were included in the study. According to the presence of essential hypertension preoperatively, patients were divided into two groups. Haemodynamic parameters were recorded at 11 time points during the operation.

Results

There were no differences in the demographic data, heart rate and intraoperative and postoperative parameters between the groups. Arterial blood pressure and additional requirement of remifentanil were found to be significantly higher in the hypertensive group intraoperatively.

Conclusion

In patients undergoing off-pump coronary revascularisation surgery, intraoperative haemodynamic stabilisation with remifentanil-desflurane anaesthesia under BIS guidance was safely provided, but higher remifentanil doses were required in hypertensive patients.

Application of a user-friendly comprehensive circulatory model for estimation of hemodynamic and ventricular variables

Purpose

Application of a comprehensive, user-friendly, digital computer circulatory model to estimate hemodynamic and ventricular variables.

Methods

The closed-loop lumped parameter circulatory model represents the circulation at the level of large vessels. A variable elastance model reproduces ventricular ejection. The circulatory model has been modified embedding an algorithm able to adjust the model parameters reproducing specific circulatory conditions. The algorithm reads input variables: heart rate, aortic pressure, cardiac output, and left atrial pressure. After a preliminary estimate of circulatory parameters and ventricular elastance, it adjusts the amount of circulating blood, the value of the systemic peripheral resistance, left ventricular elastance, and ventricular rest volume. Input variables and the corresponding calculated variables are recursively compared: the procedure is stopped if the difference between input and calculated variables is within the set tolerance. At the procedure end, the model produces an estimate of ventricular volumes and Emaxl along with systemic and pulmonary pressures (output variables). The procedure has been tested using 4 sets of experimental data including left ventricular assist device assistance.

Results

The algorithm allows the reproduction of the circulatory conditions defined by all input variable sets, giving as well an estimate of output variables.

Conclusions

The algorithm permits application of the model in environments where the simplicity of use and velocity of execution are of primary importance. Due to its modular structure, the model can be modified adding new circulatory districts or changing the existing ones. The model could also be applied in educational applications.

Anesthetic challenges in minimally invasive cardiac surgery: Are we moving in a right direction?

Continuously growing patient's demand, technological innovation, and surgical expertise have led to the widespread popularity of minimally invasive cardiac surgery (MICS). Patient's demand is being driven by less surgical trauma, reduced scarring, lesser pain, substantially lesser duration of hospital stay, and early return to normal activity. In addition, MICS decreases the incidence of postoperative respiratory dysfunction, chronic pain, chest instability, deep sternal wound infection, bleeding, and atrial fibrillation. Widespread media coverage, competition among surgeons and hospitals, and their associated brand values have further contributed in raising awareness among patients. In this process, surgeons and anesthesiologist have moved from the comfort of traditional wide incision surgeries to more challenging and intensively skilled MICS. A wide variety of cardiac lesions, techniques, and approaches coupled with a significant learning curve have made the anesthesiologist's job a challenging one. Anesthesiologists facilitate in providing optimal surgical settings beginning with lung isolation, confirmation of diagnosis, cannula placement, and cardioplegia delivery. However, the concern remains and it mainly relates to patient safety, prolonged intraoperative duration, and reduced surgical exposure leading to suboptimal treatment. The risk of neurological complications, aortic injury, phrenic nerve palsy, and peripheral vascular thromboembolism can be reduced by proper preoperative evaluation and patient selection. Nevertheless, advancement in surgical instruments, perfusion practices, increasing use of transesophageal echocardiography, and accumulating experience of surgeons and anesthesiologist have somewhat helped in amelioration of these valid concerns. A patient-centric approach and clear communication between the surgeon, anesthesiologist, and perfusionist are vital for the success of MICS.

Effect of Pre-operative Angiotensinconverting Enzyme Inhibitors on Haemodynamic Parameters and Vasoconstrictor Requirements in Patients Undergoing Off-pump Coronary Artery Bypass Surgery

The effects of pre-operative angiotensin-converting enzyme inhibitor (ACEI) treatment on haemodynamic status and vasoconstrictor requirements during off-pump coronary artery bypass surgery (OPCAB) were studied. Eighty patients selected for OPCAB were divided into those who had been treated with ACEIs for 4 weeks or more pre-operatively (ACEI group) (n = 43) and those who had not been treated with ACEIs (control group) (n = 37). Noradrenaline was infused during the operation when the mean systemic arterial pressure (SAP) fell below 60 mmHg. No significant differences in the haemodynamic parameters measured were detected between the two groups, except for cardiac output, which was found to be significantly greater in the control group. During anastomosis of the obtuse marginal branch of the left circumflex artery (OM), a significantly larger amount of noradrenaline was required by the ACEI group compared with the control group. In conclusion, pre-operative treatment with ACEIs significantly increased the amount of vasoconstrictor necessary to maintain the target SAP during OM anastomosis during OPCAB.

Exposures of Lateral and Inferior Cardiac Surface for Coronary Anastomosis during Minimally Invasive Coronary Artery Bypass Grafting

Exposure of the lateral and inferior surface of the heart during off-pump coronary artery bypass grafting is associated with some degree of cardiac instability during recovery with completion of grafting. Exposure of lateral and posterior surfaces by currently available equipment is difficult in minimally invasive coronary artery bypass grafting (MICABG) owing to limited exposure. We describe an effective variation of often-used technique of pericardial stitch in exposure of cardiac surfaces during MICABG. This technique was used in 24 patients undergoing multivessel MICABG. Deep pericardial sutures were used to manipulate the exposure of cardiac surfaces. Left anterior descending artery was grafted in all 24 cases. Obtuse marginal artery was grafted in 20 cases and posterior descending artery in 12 cases. Average grafts were 2.3 per patient. There was no conversion to median sternotomy. Use of deep pericardial suture is simple technique for exposure of lateral and inferior surface during multivessel MICABG. This offers adequate exposure and operating space for easy maneuverability.

A novel coronary active perfusion system using a conventional intra-aortic balloon pump for off-pump coronary artery bypass grafting

OBJECTIVE

It is important for coronary active perfusion systems to avoid myocardial ischemia during off-pump coronary artery bypass grafting. We have developed a new concept for a perfusion system to pump blood based on changes in helium gas volume. This system uses a conventional intra-aortic balloon pump to activate the perfusion pump. Our study used basic and animal experiments to investigate the most suitable system for coronary perfusion using this new concept.

METHODS

A conventional intra-aortic balloon pump was used to supply power. A device for perfusion was developed with a balloon placed inside a stiff syringe barrel. The device was connected to the helium gas line of the intra-aortic balloon pump. Changes in flow with changes in augmentation level were noted when volumes outside and within the balloon were changed. Six pigs with occlusion of the left anterior descending artery were used for system validation, with monitoring to identify changes in hemodynamics and cardiac enzyme levels.

RESULTS

In the basic experiment, an 80-mL outside volume and 3.0-mL inner volume resulted in the greatest percentage change in flow rate with respect to changes in augmentation. In the animal experiment, the new coronary active perfusion system prevented myocardial ischemia during coronary occlusion.

CONCLUSIONS

We clarified the most suitable method for our new coronary active perfusion system. Using this system, safe anastomosis was consistently performed in animal experiments. Clinically, off-pump coronary artery bypass may potentially be performed more safely and easily using this new system.

Placing a saline bag underneath the heart enhances transgastric transesophageal echocardiographic imaging during cardiac displacement for off-pump coronary artery bypass surgery

OBJECTIVE

The authors hypothesized that placing a saline bag (saline-filled surgical glove) underneath a displaced heart would improve ultrasound transmission for transgastric (TG) imaging and transesophageal echocardiography (TEE) to visualize left ventricular regional wall motion (LV-RWM) during cardiac displacement for off-pump coronary artery bypass (OPCAB) surgery.

DESIGN

Prospective observational study.

SETTING

Tertiary University Hospital.

PARTICIPANTS

Adult patients undergoing OPCAB surgery.

INTERVENTIONS

Intraoperative TEE examination

MEASUREMENT AND MAIN RESULTS

For off-line analyses of LV-readable segments, mid-esophageal (ME, 4-chamber, 2-chamber, and long-axis) and TG (basal- and mid-short-axis) TEE views were recorded under 3 different intraoperative conditions in 13 cases of OPCAB surgery: Before cardiac displacement (Tcontrol), after cardiac displacement (Tdisplaced), and after placing the saline bag underneath the displaced heart (Tsaline-bag). There were more LV-readable segments in the 17-segment model using integrated ME and TG views(ME + TG views) at Tsaline-bag and Tcontrol (mean[95% confidence interval], 17[17-17] and 17[17-17]) than using ME+TG at Tdisplaced (15[15-16], P = 0.002 and P<0.001, respectively). Using ME + TG views provided more LV-readable segments in the 17-segment model than using ME views at Tsaline-bag (vs. 16[14-16], P < 0.001), but not at Tdisplaced (vs. 15[14-15]). Incidences of inadequate RWM monitoring (LV-readable segments<14/17 using ME + TG views) at Tsaline-bag and Tcontrol (all 0/13) were less frequent than at Tdisplaced (3/13, all P = 0.038). There were more LV-readable segments in TG basal- and mid-short-axis views at Tsaline-bag (median [range], 6[5-6] and 5[5-6]) than at Tdisplaced (0[0-2] and 0[0-1], all P < 0.05).

CONCLUSIONS

Placing a saline bag underneath the displaced heart enhances the ability of TEE to visualize global LV-RWM by improving TG TEE imaging during OPCAB surgery.

Hemodynamic changes during myocardial revascularization without extracorporeal circulation

BACKGROUND AND OBJECTIVES

Cardiac positioning and stabilization during myocardial revascularization without extracorporeal circulation (ECC) may cause hemodynamic changes dependent to the surgical site. The objective of this study was to evaluate these changes during distal coronary anastomosis.

METHODS

Twenty adult patients undergoing myocardial revascularization without ECC were monitored by pulmonary artery catheter and transesophageal Echo Doppler. Hemodynamic data were collected at the following times before removing the stabilizer wall: (1) after volume adjustments, (2) at the beginning of distal anastomosis, and (3) after 5 minutes. Treated coronary arteries were grouped according to their location in the lateral, anterior, or posterior wall. Two-way ANOVA with repetition and Newman-Keuls post-test were used in the analysis. A p value < 0.05 was considered statically significant.

RESULTS

During myocardial revascularization without ECC, pulmonary artery wedge pressure showed elevation from 17.7 ± 6.1 to 19.2 ± 6.5 (p < 0.001) and 19.4 ± 5.9 mmHg (p < 0.001), while the central venous pressure went from 13.9 ± 5.4 to 14.9 ± 5.9 mmHg (p = 0.007) and 15.1 ± 6.0 mmHg (p = 0.006). Intermittent cardiac output was reduced from 4.70 ± 1.43 to 4.23 ± 1.22 (p < 0.001) and 4.26 ± 1.25 L.min(-1) (p < 0.001). According to transesophageal Doppler, a significant group-time interaction was observed in cardiac output, which was reduced in the lateral group from 4.08 ± 1.99 to 2.84 ± 1.82 (p = 0.02) and 2.86 ± 1.73 L.min(-1) (p = 0.02), and aortic blood flow, which went from 2.85 ± 1.39 to 1.99 ± 1.26 (p = 0.02) and 2.00 ± 1.21 L.min(-1) (p = 0.02). Other hemodynamic changes were not observed during anastomoses.

CONCLUSIONS

A significant hemodynamic deterioration was observed during myocardial revascularization without ECC. Transesophageal Doppler detected a decrease in cardiac output only in the lateral group.

A novel counterpulsation mode of rotary left ventricular assist devices can enhance myocardial perfusion

The effect of rotary left ventricular assist devices (LVADs) on myocardial perfusion has yet to be clearly elucidated, and several studies have shown decreased coronary flow under rotary LVAD support. We have developed a novel pump controller that can change its rotational speed (RS) in synchronization with the native cardiac cycle. The aim of our study was to evaluate the effect of counterpulse mode, which increases the RS in diastole, during coronary perfusion. Experiments were performed on ten adult goats. The EVAHEART LVAD was installed by the left ventricular uptake and the descending aortic return. Ascending aortic flow, pump flow, and coronary flow of the left main trunk were monitored. Coronary flow was compared under four conditions: circuit-clamp, continuous mode (constant pump speed), counterpulse mode (increased pump speed in diastole), and copulse mode (increased pump speed in systole). There were no significant baseline changes between these groups. In counterpulse mode, coronary flow increased significantly compared with that in continuous mode. The waveform analysis clearly revealed that counterpulse mode mainly resulted in increased diastolic coronary flow. In conclusion, counterpulse mode of rotary LVADs can enhance myocardial perfusion. This novel drive mode can provide great benefits to the patients with end-stage heart failure, especially those with ischemic etiology.

Jugular bulb desaturation during off-pump coronary artery bypass surgery

PURPOSE

Off-pump coronary artery bypass grafting surgery (OPCAB) frequently results in significant jugular bulb desaturation. Although jugular bulb desaturation during OPCAB may be associated with postoperative cerebral injury, routine jugular bulb oximetry appears to be invasive and expensive. We hypothesized that intraoperative hemodynamic compromise during OPCAB due to cardiac displacement is associated with jugular bulb desaturation which correlates with specific hemodynamic and physiological changes.

METHODS

Hemodynamic and physiological data were measured at the following points: (1) before anastomosis of the coronary artery (baseline); (2) during anastomosis of the left anterior descending artery; (3) during anastomosis of the circumflex branch or posterior descending artery; and (4) after chest closure. Arterial, mixed venous, and jugular venous bulb blood gas analyses were performed serially.

RESULTS

Jugular bulb desaturation (<or=50%) frequently occurred during surgical displacement of the heart. Mixed venous oxygen saturation (S(VO2)), partial pressure of carbon dioxide (Pa(CO2)), and central venous pressure (CVP) showed a significant relationship with jugular bulb oxygen saturation (r = 0.45) by multivariate linear regression analysis. Multivariate logistic regression analysis also demonstrated that S(VO2) <or= 70%, Pa(CO2) <or= 40 mmHg, and CVP >or= 8 mmHg were likely predictors of the occurrence of jugular bulb desaturation.

CONCLUSION

Changes in S(VO2) and Pa(CO2) were associated with jugular bulb oxygen saturation, and S(VO2) <or= 70%, Pa(CO2) <or= 40 mmHg, and CVP >or= 8 mmHg had a significant odds ratio for jugular bulb desaturation. We suggest that achieving normal values of S(VO2), Pa(CO2) and CVP may be important to prevent cerebral desaturation during OPCAB.

Minimally invasive direct coronary artery bypass and off-pump coronary artery bypass surgery: anesthetic considerations

Many new surgical technologies are being developed, with the overall aim of improving outcomes. One common feature of many new technologies is that they offer a safer approach than previous techniques; one of the greatest forces for change over the last 30 years is risk reduction. Cardiac surgery risk has been effectively undercut by percutaneous-based procedures, which have offered dramatic reductions in risk--at least in the short term. Beating heart techniques, whether minimally invasive direct coronary artery bypass (MIDCAB), off-pump coronary artery bypass surgery (OPCAB), or in other forms, such as percutaneous valve replacement, are likely to dramatically increase over the next decade. What role OPCAB and MIDCAB techniques will play in this new era is anyone's guess.

A randomized comparative study of patients undergoing myocardial revascularization with or without cardiopulmonary bypass surgery: The MASS III Trial

The MASS III Trial is a large project from a single institution, The Heart Institute of the University of Sao Paulo, Brazil (InCor), enrolling patients with coronary artery disease and preserved ventricular function. The aim of the MASS III Trial is to compare medical effectiveness, cerebral injury, quality of life, and the cost-effectiveness of coronary surgery with and without of cardiopulmonary bypass in patients with multivessel coronary disease referred for both strategies. The primary endpoint should be a composite of cardiovascular mortality, cerebrovascular accident, nonfatal myocardial infarction, and refractory angina requiring revascularization. The secondary end points in this trial include noncardiac mortality, presence and severity of angina, quality of life based on the SF-36 Questionnaire, and cost-effectiveness at discharge and at 5-year follow-up. In this scenario, we will analyze the cost of the initial procedure, hospital length of stay, resource utilization, repeat hospitalization, and repeat revascularization events during the follow-up. Exercise capacity will be assessed at 6-months, 12-months, and the end of follow-up. A neurocognitive evaluation will be assessed in a subset of subjects using the Brain Resource Center computerized neurocognitive battery. Furthermore, magnetic resonance imaging will be made to detect any cerebral injury before and after procedures in patients who undergo coronary artery surgery with and without cardiopulmonary bypass.

TRIALS REGISTRATION

Clinical Trial registration information ISRCTN59539154 Off-pump vs. on-pump surgery in patients with Stable CAD MASS III.

A randomized comparative study of patients undergoing myocardial revascularization with or without cardiopulmonary bypass surgery: The MASS III Trial

The MASS III Trial is a large project from a single institution, The Heart Institute of the University of Sao Paulo, Brazil (InCor), enrolling patients with coronary artery disease and preserved ventricular function. The aim of the MASS III Trial is to compare medical effectiveness, cerebral injury, quality of life, and the cost-effectiveness of coronary surgery with and without of cardiopulmonary bypass in patients with multivessel coronary disease referred for both strategies. The primary endpoint should be a composite of cardiovascular mortality, cerebrovascular accident, nonfatal myocardial infarction, and refractory angina requiring revascularization. The secondary end points in this trial include noncardiac mortality, presence and severity of angina, quality of life based on the SF-36 Questionnaire, and cost-effectiveness at discharge and at 5-year follow-up. In this scenario, we will analyze the cost of the initial procedure, hospital length of stay, resource utilization, repeat hospitalization, and repeat revascularization events during the follow-up. Exercise capacity will be assessed at 6-months, 12-months, and the end of follow-up. A neurocognitive evaluation will be assessed in a subset of subjects using the Brain Resource Center computerized neurocognitive battery. Furthermore, magnetic resonance imaging will be made to detect any cerebral injury before and after procedures in patients who undergo coronary artery surgery with and without cardiopulmonary bypass.

TRIALS REGISTRATION

Clinical Trial registration information ISRCTN59539154 Off-pump vs. on-pump surgery in patients with Stable CAD MASS III.

Numerical simulation of hemodynamic changes during beating-heart surgery: analysis of the effects of cardiac position alteration in an animal model

Hemodynamic instability, mostly due to vertical lifting of the heart, is usually observed during beating-heart surgical procedures. However, some hemodynamic parameters, such as coronary blood flow, are not routinely measured. A digital computer model of the circulation able to simulate and analyze the effects of heart lifting and the Trendelenburg maneuver, and thus supply detailed hemodynamic information to the clinicians would provide a useful analytical tool. A lumped parameters model of the circulation was applied to both beta-blocked and not beta-blocked pigs. The results confirmed a drop of cardiac output and coronary flow during heart lifting and a rise of both variables after the Trendelenburg maneuver for beta-blocked animals. In not beta-blocked pigs, the analysis was more complex but the model reproduced experimental data and permitted coronary flow to be estimated. These results showed the feasibility of numerical simulation for specific circulatory conditions encountered during beating-heart surgery.

Starfish™ heart positioner maintains right ventricular function during lateral wall displacement

BACKGROUND

: The authors examined parameters of cardiovascular function using Starfish and deep pericardial sutures (DPS) in a beating heart porcine model and to clarify toleration of right ventricular function with Starfish in lateral wall displacement.

METHODS

: Eight healthy pigs were used. In addition to normal pressure monitor catheters, a Swan-Ganz continuous cardiac output (CO) and end diastolic volume thermodilution catheter was used for precise and quantitative monitoring of the right ventricular function.

RESULTS

: Lateral displacement of the heart with DPS resulted in a significant hemodynamic compromise. Cardiac output and right ventricular ejection fraction (RVEF) decreased from 3.0 ± 0.9 to 2.6 ± 1.0 L/min (P = 0.014) and from 27.9 ± 3.0% to 23.3 ± 4.8% (P = 0.019). With Starfish™, CO and RVEF were maintained from 3.0 ± 0.9 to 3.0 ± 0.9 L/min (P = 0.743) and from 27.9 ± 3.0% to 28.3 ± 3.8% (P = 0.476).

CONCLUSION

: Starfish™ contributed to the stability of hemodynamics by maintaining the right ventricular function. Lateral displacement with PDS resulted in significant hemodynamic compromised compared with Starfish™ and baseline neutral position.

Displacement of the Beating Heart with a Low-Profile Suction-Based Apical Positioning Device in a Closed Chest

Background

Off-pump, multivessel, endoscopic coronary artery bypass requires cardiac displacement within an intact chest. The current study evaluated right ventricular performance and systemic hemodynamics while exposing the posterior surface of the heart using a novel, low-profile, apical suction-based cardiac positioner in a closed-chest, beating-heart model.

Methods

Six pigs underwent instrumentation with continuous monitoring of arterial pressure by fluid-filled transducer and cardiac output and coronary blood flow by ultrasound transit time flow probe. Right ventricular (RV) pressure-volume loops were generated by an impedance catheter. Heart rate was maintained between 80 and 100 beats per minute pharmacologically. The cardiac positioner displaced the heart endoscopically through a port. Data were obtained in 5 sequential phases: (1) baseline/free-beating, (2) positioner coaptation, (3) addition of Trendelenburg, (4) cardiac displacement with Trendelenburg, and (5) cardiac displacement without Trendelenburg.

Results

Cardiac displacement without Trendelenburg (Phase 5) resulted in a significant (P < 0.05) decrease in cardiac output, coronary blood flow, RV systolic pressure (RVSP), mean arterial pressure, RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) compared with baseline (Phase 1). With Trendelenburg added to cardiac displacement (Phase 4), all parameters improved, but only RVSP, mean arterial pressure, and RVEDV were comparable to baseline (Phase 1). There were no local complications from device coaptation.

Conclusions

The low-profile endoscopic cardiac positioner is safe and effective in the closed-chest, beating-heart porcine model. Nevertheless, cardiac displacement in a closed chest does cause impairment in ventricular performance that can be ameliorated by the addition of Trendelenburg and further technological progress.

Transmural distribution of myocardial blood perfusion and phasic coronary blood flow pattern in a canine model of acute ischemia

BACKGROUND

Although several investigators have analyzed coronary artery blood flow under various conditions, almost all these studies have measured only some branches of the left anterior descending (LAD), left circumflex (LCX), or right coronary (RCA) artery.

METHODS

In a canine model of acute ischemia (n = 5), we simultaneously assessed (a) regional myocardial blood perfusion using microspheres and (b) phasic coronary blood flow patterns as measured by three epicardial flow probes placed around the LAD, LCX, and RCA.

RESULTS

The results from this study indicated that the LAD supplies blood to the epicardial (r = 0.687, p<0.0001), midwall (r = 0.556, p = 0.0021), and endocardial layers (r = 0.666, p = 0.0001) of the LAD area; the LCX supplies the midwall (r = 0.514, p = 0.0051) and endocardial layer (r = 0.621, p = 0.0004) of the LCX area, antero-lateral papillary muscle (r = 0.548, p = 0.0025), and postero-medial papillary muscle (r = 0.641, p = 0.0002), especially during the diastolic phase; and the RCA supplies the right ventricular apex (r=0.559, p=0.0020), left atrium (r = 0.618, p = 0.0005), right atrium (r = 0.471, p = 0.0114), and postero-medial papillary muscle (r = 0.486, p = 0.0088), especially during the systolic phase.

CONCLUSIONS

These results are potentially relevant to understanding the physiology of myocardial blood perfusion and to improving treatment of acute myocardial ischemia and infarction.

Portable coronary active perfusion system for off-pump coronary artery bypass grafting

PURPOSE

The present study was performed to develop a new perfusion system for off-pump coronary artery bypass grafting and to examine whether even a simple coronary perfusion system can maintain adequate blood flow delivery during anastomosis.

DESCRIPTION

The experiment was performed in two stages. In procedure 1, 3 pigs with left anterior descending artery occlusion were used to evaluate optimal perfusion flow rate and coronary artery internal pressure, and to evaluate the safety area of perfusion. In procedure 2, 6 pigs were used to validate the new portable coronary perfusion system.

EVALUATION

The optimal blood flow in the portable coronary active perfusion system was less than approximately 40 mL/min. The small, easy to use pump system (ie, the portable coronary active perfusion system) may prevent hemodynamic deterioration and ventricular arrhythmia during coronary occlusion, resulting in better maintenance of left ventricular function.

CONCLUSIONS

Even a simple pump system can achieve effective perfusion for safe anastomosis. Further studies are required to allow the clinical use of this system.

Off-pump myocardial revascularization

Since 1998, a large body of literature regarding off-pump coronary bypass surgery has been published, although varying techniques and outcomes likely have led to its inconsistent application. One approach has been developed and standardized at KU Leuven. This approach is straightforward and can be replicated without need for conversion toward cardiopulmonary bypass. The patient is 'conditioned' before and during the procedure. Both mammary arteries are harvested through a standard sternotomy. The anterior surface of the heart is exposed with a horizontal line of left-sided pericardial stitches, just above the level of the heart. The anterior coronary vessels are anastomosed after routine shunting. The lateral and inferior aspects of the heart are exposed without deforming the atrio-ventricular axis. This is performed in a stepwise manner. The first step is anchoring a sling into the posterior pericardium under the roof of the left atrium. Second, this sling is gradually pulled upwards, supporting the heart as a cradle. Once the heart is exposed toward the zenith, an apical suction device stabilizes, reformats and exposes the ventricle. The lateral and inferior walls are then revascularized. As a strict no-touch technique is used, free grafts are anastomosed to in-situ arterial grafts.

Esophageal Doppler and thermodilution are not interchangeable for determination of cardiac output

PURPOSE

This study compares thermodilution cardiac output (TD-CO) and esophageal Doppler cardiac output (ED-CO) during periods of hemodynamic stability and after heart stabilization during off-pump coronary artery bypass (OPCAB) surgery.

METHODS

After Institutional Review Board approval, 58 patients undergoing OPCAB had simultaneous comparison of TD-CO and ED-CO at three time periods. Measurements were recorded, in a blinded manner, after probe insertion (T0), immediately before and after (T1,T2) heart displacement and before starting any pharmacological treatment (if needed) to maintain systolic blood pressure to its value before heart mobilization. Measurements were also taken before sternal closure (Tfinal).

RESULTS

Three hundred and two pairs of data were analyzed using the Bland and Altman method. Bias, standard deviation (SD) of the bias (precision), and degree of agreement (bias +/- 2 SD) were calculated. Based on published literature, we considered that the highest degree of agreement should be < 0.5 L.min(-1) to consider both methods as interchangeable. At T0, bias and SD of bias between TD-CO and ED-CO were -0.1 +/- 1.0 L.min(-1). Immediately before heart stabilization, bias +/- SD was 0.6 +/- 1.0 L.min(-1) and after heart displacement, 0.5 +/- 0.8 L.min(-1). At Tfinal, bias +/- SD was 0.7+/- 0.7 L.min(-1).

CONCLUSION

Because the degree of agreement was > 0.5 L.min(-1) at all measurement periods except T0, we conclude that TD and ED are not interchangeable at any time during OPCAB surgery.

Hemodynamic Changes During Posterior Vessel Off-Pump Coronary Artery Bypass: Comparison Between Deep Pericardial Sutures and Vacuum-Assisted Apical Suction Device

BACKGROUND

Displacement of the heart to expose posterior vessels during off-pump coronary artery bypass may cause hemodynamic derangement. The aims of this study were (1) to elucidate the hemodynamic changes during off-pump coronary artery bypass for the obtuse marginal branch (OM) of the left circumflex artery; and (2) to compare the hemodynamic changes caused by a deep pericardial suture technique with those caused by a vacuum-assisted apical suction device for displacement of the heart.

METHODS

Hemodynamic changes during posterior vessel off-pump coronary artery bypass were studied in a prospective randomized manner. A deep pericardial suture technique (group 1, n = 10) or a vacuum-assisted apical suction device (group 2, n = 10) was used to facilitate the exposure of the OM. Hemodynamic variables such as cardiac index, stroke volume index (SVI), mean arterial pressure, mean pulmonary artery pressure, central venous pressure, pulmonary capillary wedge pressure, heart rate, systemic vascular resistance, pulmonary vascular resistance, left ventricular stroke work index, and right ventricular stroke work index were monitored during off-pump coronary artery bypass. Hemodynamic data were obtained before revascularization of the left anterior descending coronary artery at a baseline (T0), 3 minutes after heart displacement for revascularization of OM (T1), 3 minutes after the beginning of OM grafting (T2), and 3 minutes after the completion of OM grafting and heart repositioning (T3).

RESULTS

There were no significant differences in the baseline hemodynamic variables (T0) between the two groups. In group 1, SVI, cardiac index, left ventricular stroke work index, and right ventricular stroke work index decreased significantly, and central venous pressure and pulmonary capillary wedge pressure increased significantly, during displacement of the heart (T1, p < 0.05). In group 2, SVI decreased significantly, and central venous pressure, pulmonary capillary wedge pressure, and mean pulmonary artery pressure increased significantly during displacement of the heart (T1, p < 0.05). The percent changes of cardiac index, SVI, and right ventricular stroke work index during OM grafting (T2) in comparison with baseline values (T0) were significantly larger in group 1 than in group 2 (cardiac index, 73% +/- 12% versus 90% +/- 11%; SVI, 69% +/- 12% versus 86% +/- 8%; right ventricular stroke work index, 30% +/- 17% versus 71% +/- 25%, in groups 1 versus 2, respectively; p < 0.05).

CONCLUSIONS

Displacement of the heart using either a deep pericardial suture technique or a vacuum-assisted apical suction device caused a significant decrease in SVI. The hemodynamic changes during OM grafting were smaller when using a vacuum-assisted apical suction device.

Que faut-il attendre de la chirurgie coronaire sans circulation extracorporelle ?

Coronary artery bypass surgery with beating heart (off-pump) has become more common in the last ten years allowing seven randomized studies with at least 60 patients, comparing off-pump and on-pump coronary bypass. Anaesthesia, monitoring and haemodynamic complications are described. Randomized studies concluded to less elevation of biochemical markers of myocardial and renal injury, less hydric inflation, less cerebral microemboli, reduction of homologous blood transfusions, of hospital stay and global costs. However in low risk patients no reduction in myocardial infarction, atrial fibrillation, stroke, acute renal failure, early reoperation, surgical site infection and mortality were observed. Non-randomized studies suggest a benefit in stroke and mortality in elderly patients but the possibility of incomplete revascularization remains.

Ninety-degree anterior cardiac displacement in off-pump coronary artery bypass grafting: the Starfish cardiac positioner preserves stroke volume and arterial pressure

PURPOSE

In off-pump coronary surgery through sternotomy, exposure of posterior circumflex branches causes circulatory deterioration in both patients and pigs. We assessed cardiac pump function when displacing the pig heart anteriorly with a suction cardiac positioner.

DESCRIPTION

Six pigs (+/-80 kg) underwent sternotomy for hemodynamic instrumentation using catheter-tipped manometers and paced at 80 beats/min. Ultrasound flow probes were placed around the aorta and proximal coronary arteries. The heart was retracted anteriorly to 90 degrees with the Starfish cardiac positioner attached to the apex by means of suction (-400 mm Hg). Retraction was guided by cardiac output monitoring.

EVALUATION

Anterior displacement to 90 degrees facilitated full exposure of posterior arteries. Stroke volume and mean arterial pressure decreased to 94% +/- 13% (mean +/- SD, p = 0.135) and 95% +/- 13% (p = 0.09) of control values, respectively. Right and left ventricular end-diastolic pressure increased to 129% +/- 37% (p = 0.009) and to 128% +/- 57% (p = 0.235), respectively. Coronary flow remained unchanged. Additional 15-degree head-down positioning increased stroke volume to 113% +/- 17% (p = 0.015) and mean arterial pressure to 113% +/- 25% (p = 0.087) at the expense of further increased right and left ventricular end-diastolic pressure (186% +/- 63%, p < 0.001 and 157% +/- 49%, p < 0.001, respectively).

CONCLUSIONS

When lifting the porcine heart ninety degrees anteriorly, the Starfish cardiac positioner facilitated exposure of posterior branches and, when guided by cardiac output, preserved stroke volume and arterial pressure.

Haemodynamic effects of a milrinone infusion without a bolus in patients undergoing off-pump coronary artery bypass graft surgery

The haemodynamic effects of a continuous infusion of milrinone without an initial bolus dose were evaluated in patients undergoing off-pump coronary artery bypass graft surgery. After internal mammary artery harvest, milrinone 0.5 microg.min(-1).kg(-1) (29 patients) or a normal saline infusion (33 patients) was started and continued until all graft anastomoses were completed. Haemodynamic variables were recorded before application of the tissue stabiliser, at 1, 3, 5 and 10 min after the application of the stabiliser, and after its removal. The administration of a milrinone infusion was associated with a smaller decrease in cardiac output and mixed venous oxygen saturation during all the coronary artery anastomoses, with no severe complications and a decreased dose of norepinephrine infused to maintain systemic arterial pressure.

Off-pump coronary artery bypass surgery: physiology and anaesthetic management †

Increasing interest is being shown in beating heart (off-pump) coronary artery surgery (OPCAB) because, compared with operations performed with cardiopulmonary bypass, OPCAB surgery may be associated with decreased postoperative morbidity and reduced total costs. Its appears to produce better results than conventional surgery in high-risk patient populations, elderly patients, and those with compromised cardiac function or coagulation disorders. Recent improvements in the technique have resulted in the possibility of multiple-vessel grafting in all coronary territories, with a graft patency comparable with conventional surgery. During beating-heart surgery, anaesthetists face two problems: first, the maintenance of haemodynamic stability during heart enucleation necessary for accessing each coronary artery; and second, the management of intraoperative myocardial ischaemia when coronary flow must be interrupted during grafting. The anaesthetic technique is less important than adequate management of these two major constraints. However, experimental and recent clinical data suggest that volatile anaesthetics have a marked cardioprotective effect against ischaemia, and might be specifically indicated. OPCAB surgery requires team work between anaesthetists and surgeons, who must be aware of each other's constraints. Some surgical aspects of the operation are reviewed along with physiological and anaesthetic data.

Cardiac output monitoring during off-pump coronary artery bypass grafting

OBJECTIVE

To evaluate and compare monitors of cardiac output during repositioning and stabilization of the heart for off-pump coronary artery bypass (OPCAB) surgery.

DESIGN

Prospective, observational, clinical study.

SETTING

University teaching hospital.

PARTICIPANTS

Consecutive patients scheduled to undergo elective OPCAB (n = 19).

INTERVENTIONS

Monitoring, induction, and anesthesia followed a routine protocol for coronary artery bypass patients. This included the use of transesophageal echocardiography (TEE) and pulmonary artery catheter placement.

MEASUREMENTS AND MAIN RESULTS

After positioning and stabilization for OPCAB surgery, the changes in descending aortic flow velocity (VTI) times heart rate (HR) and the mixed venous oxygen saturation (SvO(2)) could be used to predict the changes in thermodilution cardiac output (TDCO) using the following model: deltaTDCO((calc))=-13.15+0.35(deltaVTI*HR)+0.61(deltaSvO(2)) where Delta indicates the percentage change from baseline values. The changes in mean arterial pressure, mean pulmonary artery pressure, and continuous cardiac output did not correlate with the changes in TDCO.

CONCLUSION

The use of the VTI*HR, as determined by TEE, in addition to the SvO(2) can strengthen clinical decision making during repositioning and stabilization of the heart during OPCAB. Changes in the VTI*HR and SvO(2) can be used as surrogate markers for changes in CO during OPCAB surgery.

Analysis of thoracic aortic blood flow during off-pump coronary artery bypass surgery

OBJECTIVES

The non-invasive monitoring of thoracic aortic blood flow (TABF) during off-pump coronary artery bypass (OPCAB) surgery is becoming more commonly used and proved to be invaluable in the early detection of haemodynamic compromise due to heart displacement. The aim of this study was to analyze the changes in the TABF during OPCAB using transoesophageal Doppler and compare them with the changes observed by other monitoring methods as cardiac output, invasive pulmonary and radial pressures and mixed venous oxygen saturation.

METHODS

The measurements obtained from classic haemodynamic monitoring methods including the radial artery line and the pulmonary artery catheter with continuous monitoring of the cardiac output and mixed venous blood oxygen saturation were compared to the measurements of TABF obtained from a transoesophageal Doppler probe in 15 consecutive patients who underwent OPCAB surgery.

RESULTS

The TABF decreased significantly during the construction of coronary anastomoses from 3.42 +/- 0.94 l/min (baseline) to 2.2 +/- 0.8 l/min during the first coronary anastomosis and then to 2.14 +/- 1.12 l/min during the second coronary anastomosis (F=4.29, P=0.008). TABF returned to the baseline values (2.85 +/- 1.19 l/min) at chest closure. The cardiac output measurement showed no significant decrease compared to baseline.

CONCLUSIONS

Low TABF occurred without significant changes in the measurements obtained from classic haemodynamic monitoring methods during OPCAB surgery. This finding could be of vital importance in helping improve the monitoring and consequently the management of patients undergoing OPCAB surgery.

Deep pericardial stitch enables hemodynamically stable exposure of beating heart

The use of a deep pericardial stitch to obtain optimal exposure for precise distal anastomoses was assessed in 51 patients (mean age, 56.5 +/- 9.1 years) undergoing off-pump coronary artery bypass grafting. Hemodynamic data were recorded after sternotomy, before, and after each of the 120 distal anastomosis. Most hemodynamic parameters did not change throughout the procedures. During exposure of the circumflex artery, there were significant decreases in systolic arterial pressure from 106.0 +/- 15.5 to 87.7 +/- 13.6 mm Hg, mean systemic arterial pressure from 83.9 +/- 11.7 to 68.5 +/- 17.0 mm Hg, stroke volume from 68.5 +/- 23.3 to 50.5 +/- 18.3 mL, and stroke index from 34.4 +/- 11.5 to 24.3 +/- 8.7 mL x m(-2). Cardiac function was not affected when other coronary arteries were bypassed. On completion of all anastomoses, hemodynamics returned to baseline status. It was concluded that the deep pericardial stitch enabled stable and safe exposure of the heart for off-pump coronary artery grafting.

Endoscopic exposure and stabilization of posterior and inferior branches using the endo-starfish cardiac positioner and the endo-octopus stabilizer for closed-chest beating heart multivessel CABG: hemodynamic changes in the pig

BACKGROUND

Closed-chest, off-pump, multivessel CABG requires modified instruments to expose and stabilize posterior and inferior coronary branches. Using three new prototype devices, we explored the feasibility of endoscopic bypass grafting on these branches and assessed cardiac function during cardiac displacement.

METHODS

Eight pigs (75 to 85 kg) were instrumented for hemodynamics and paced at 80 to 100 bpm. After closure of the sternotomy wound, the Da Vinci endoscope was inserted subxiphoidally. A sternal hook was used to hoist the sternum ventrally by 5 cm. The articulating EndoStarfish cardiac positioner was placed through a trocar (Ø12 mm). The positioner was fixed to the apex using -400 mm Hg suction and the heart was displaced anteriorly to 90 degrees. In 12 other pigs (75 to 85 kg), both internal mammary arteries (IMA) were harvested and the sternal wound was closed. Five trocar ports were placed for instrumentation (Ø12 mm, two in left chest, two in right chest, and one subxiphoidally). For coronary stabilization, a novel deployable EndoOctopus cardiac stabilizer was employed (suction -400 mm Hg). The Da Vinci robot-telemanipulator system was used for endoscopic grafting of the left and right IMA on posterior and inferior branches (16 anastomoses).

RESULTS

When circumflex arteries were fully exposed and accessible for coronary surgery, stroke volume decreased by 18%+/-3 versus baseline (P=0.02) and mean arterial pressure decreased by 27%+/-6 (P=0.001). Additional 10 degrees Trendelenburg head-down positioning normalized stroke volume and arterial pressure. In the displaced heart, obtuse marginal branches (OM) and the ramus descending posterior (RDP) of the right coronary artery became fully exposed with a mean arterial pressure >70 mm Hg during grafting. No accidental detachment occurred. Coronary target motion was restrained to approximately 1x1 mm. In two test cases, five sham distal anastomoses were created (grafts sewn to epicardium, left IMA to OM2 jump to OM3, right IMA to RDP, and composite graft from left IMA jump to diagonal branch). In 10 animals, 16 successfully completed anastomoses to RPD and OM branches of Ø1.75 to 2.5 mm required 25 to 60 minutes each to construct. At sacrifice, all anastomoses were patent.

CONCLUSIONS

In the closed-chest pig in Trendelenburg position and during lifting of the sternum, the EndoStarfish and EndoOctopus enabled IMA grafting of posterior and inferior branches on the beating heart without mean arterial pressure dropping below 70 mm Hg.

Off-pump coronary surgery: how do the anesthetic considerations differ?

In recent years, there has been much interest in performing coronary artery bypass graft (CABG) surgery without the aid of cardiopulmonary bypass (CPB). Initial efforts focused on "minimally invasive" direct coronary artery bypass, wherein the left anterior descending artery is bypassed with an in situ left internal mammary artery graft through a small left anterior thoracotomy. A more widely adopted approach however, is off-pump CABG (OPCAB), in which CABG surgery is performed on one or more vessels through the usual median sternotomy approach without the aid of CPB. This article reviews the differences in the anesthetic considerations of OPCAB compared to conventional CABG using CPB.