Thermoelectric characterization of flexible micro-thermoelectric generators

A new experimental setup for the characterization of flexible micro-thermoelectric generators is reported. The system can measure the power generated and the thermoelectric conversion efficiency of devices under mechanical stresses and deformations, in atmospheric environment and under vacuum, in the temperature interval 293 K-423 K, as a function of the load resistance and of the mechanical pressure, with an uncertainty on the temperature difference of ±0.02 K. The system has been tested on commercial rigid devices and on a custom-made, flexible, proof-of-concept, organic-inorganic hybrid generator made of eight thermocouples. Repeatability on the power generated and conversion efficiency within 5% and 3%, respectively, was demonstrated, and accuracy of the measurement was granted by minimization of all the potential sources of heat flux losses.

Mechanical circulatory support for acute heart failure in 2013: an update on available devices, indications and results

Severe acute heart failure often requires some form of mechanical support to circulation. The use of intraaortic balloon counterpulsation in postinfarction cardiogenic shock - perhaps the most common scenario of this kind - has been recently questioned in the IABP SHOCK trial. In the most severe forms, extracorporeal membrane oxygenation is becoming the mainstay of treatment to support circulation or in order to gain time for a further evaluation. Moreover, advances in technology and a reducing number of donors are leading to more extended indications to the implantation of ventricular assist devices. Herein, we offer a focused review on recent articles dealing with mechanical support to circulation in acute heart failure, which we found relevant in terms of their possible impact on therapeutic strategies and indication.

Distal embolization of Edwards SAPIEN prosthesis during transcatheter aortic valve implantation

AIM

Transcatheter aortic valve implantation (TAVI) is considered an alternative therapy in high risk patients with severe aortic stenosis. Despite this, such a minimally invasive procedure is not free from complications.

CASE REPORT

An 86-year-old woman underwent a 26-mm SAPIEN TAVI for aortic valve stenosis. Procedure was complicated by valve embolization into the ascending aorta likely due to a sub-optimal positioning of prosthesis during its deployment. Patient was treated by surgical removal of stent-valve and conventional valve replacement. Patient was discharged from hospital 7 days after surgery. At six months follow-up she was asymptomatic and the valve had a good competence with a mean transaortic gradient of 8 mmHg.

CONCLUSIONS

After TAVI prosthesis embolization, conversion to conventional surgical treatment is imperative and can be associated with excellent outcome.

Mechanisms involved in the desflurane-induced post-conditioning of isolated human right atria from patients with type 2 diabetes

BACKGROUND

Desflurane triggers post-conditioning in the diabetic human myocardium. We determined whether protein kinase C (PKC), mitochondrial adenosine triphosphate-sensitive potassium (mitoK(ATP)) channels, Akt, and glycogen synthase kinase-3β (GSK-3β) were involved in the in vitro desflurane-induced post-conditioning of human myocardium from patients with type 2 diabetes.

METHODS

The isometric force of contraction (FoC) of human right atrial trabeculae obtained from patients with type 2 diabetes was recorded during 30 min of hypoxia followed by 60 min of reoxygenation. Desflurane (6%) was administered during the first 5 min of reoxygenation either alone or in the presence of calphostin C (PKC inhibitor) or 5-hydroxydecanoate (5-HD) (mitoK(ATP) channel antagonist). Phorbol 12-myristate 13-acetate (PKC activator) and diazoxide (a mitoK(ATP) channel opener) were superfused during early reoxygenation. The FoC at the end of the 60 min reoxygenation period was compared among treatment groups (FoC(60); mean and sd). The phosphorylation of Akt and GSK-3β was studied using western blotting.

RESULTS

Desflurane enhanced the recovery of force [FoC(60): 79 (3)% of baseline] after 60 min of reoxygenation when compared with the control group (P>0.0001). Calphostin C and 5-HD abolished the beneficial effect of desflurane-induced post-conditioning (both P<0.0001). Phorbol 12-myristate 13-acetate and diazoxide enhanced the FoC(60) when compared with the control group (both P<0.0001). Desflurane increased the level of phosphorylation of Akt and GSK-3β (P<0.0001).

CONCLUSIONS

Desflurane-induced post-conditioning in human myocardium from patients with type 2 diabetes was mediated by the activation of PKC, the opening of the mitoK(ATP) channels, and the phosphorylation of Akt and GSK-3β.

Continuous administration of remifentanil and sufentanil induces cardioprotection in human myocardium, in vitro

BACKGROUND

Remifentanil and sufentanil are widely used opioids during general anaesthesia for cardiac and non-cardiac surgery. This study was conducted to evaluate the hypothesis that the continuous administration of remifentanil and sufentanil, at clinically relevant concentrations, could provide protection of human myocardium, in vitro, against hypoxia-reoxygenation injury.

METHOD

Isometrically contracting isolated human right atrial trabeculae were exposed to 30 min of hypoxia and 60 min of reoxygenation. In separate groups, remifentanil at 10(-11), 10(-10), 10(-9), or sufentanil at 10(-11), 10(-10), 10(-9) M were administered 10 min before hypoxia until the end of the experiment. The force of contraction (FoC) of trabeculae was recorded continuously. Developed force was compared (mean ± standard deviation) between the groups using a variance analysis and post hoc tests.

RESULTS

At the end of the 60-min reoxygenation, remifentanil 10(-11) M (FoC: 82 ± 7% of baseline), 10(-10) M (FoC: 78 ± 5% of baseline), 10(-9) M (FoC: 80 ± 4% of baseline) and sufentanil 10(-11) M (FoC: 78 ± 8% of baseline), 10(-10) M (FoC: 83 ± 6% of baseline), 10(-9) M (FoC: 83 ± 8% of baseline) enhanced the recovery of FoC as compared with the control group (53 ± 9% of baseline, P<0.0001).

CONCLUSIONS

Remifentanil and sufentanil, at clinically relevant concentrations, confer cardioprotection of human myocardium against hypoxia reoxygenation, in vitro.

Desflurane-induced postconditioning of diabetic human right atrial myocardium in vitro

AIM

We tested the hypothesis that brief exposure to desflurane at the time of reoxygenation might be able to protect against hypoxia-reoxygenation injury in human myocardium from diabetic (insulin-dependent, ID; and non-insulin-dependent, NID) patients and non-diabetic (ND) subjects.

METHODS

The force of contraction (34 degrees C, stimulation frequency 1Hz) in the right atrial trabeculae was recorded during 30min of hypoxia followed by 60min of reoxygenation. Desflurane (at 3, 6 and 9%) was administered during the first 5min of reoxygenation. The force of contraction at the end of the 60-min reoxygenation period (FoC(60)) was compared in the study groups (means+/-SD).

RESULTS

In the ND group, desflurane at 3, 6 and 9% (FoC(60): respectively 78+/-10%, 84+/-4% and 85+/-12% of baseline) enhanced the recovery of FoC(60) compared with the ND-controls (53+/-7% of baseline; P<0.05). In the ID group, desflurane at 3% (61+/-4%) did not modify the recovery of FoC(60) compared with the ID-controls (54+/-6%), whereas desflurane at 6 and 9% (75+/-11% and 81+/-8%, respectively) enhanced the recovery of FoC(60)vs the controls (P<0.05). In the NID group, desflurane at 3% (57+/-5%) also failed to modify the recovery of FoC(60) compared with the NID-controls (52+/-10%), while desflurane at 6 and 9% (80+/-10% and 79+/-7%, respectively) enhanced the recovery of FoC(60)vs the controls (P<0.05).

CONCLUSION

Desflurane in vitro was able to postcondition diabetic (both ID and NID) human myocardium at 6 and 9%, but not at 3%.

Sevoflurane- and desflurane-induced human myocardial post-conditioning through Phosphatidylinositol-3-kinase/Akt signalling

BACKGROUND

The role of phosphatidylinositol-3-kinase (PI3K) in sevoflurane- and desflurane-induced myocardial post-conditioning remains unknown.

METHODS

We recorded isometric contraction of isolated human right atrial trabeculae (oxygenated Tyrode's at 34 degrees C, stimulation frequency 1 Hz). In all groups, a 30-min hypoxic period was followed by a 60-min reoxygenation period. At the onset of reoxygenation, muscles were exposed to 5 min of sevoflurane 1%, 2%, and 3%, and desflurane 3%, 6%, and 9%. In separate groups, sevoflurane 2% and desflurane 6% were administered in the presence of 100 nM wortmannin, a PI3K inhibitor. Recovery of force after the 60-min reoxygenation period was compared between groups (mean +/- SD).

RESULT

As compared with the Control group (49 +/- 7% of baseline) PostC by sevoflurane 1%, 2%, and 3% (78 +/- 4%, 79 +/- 5%, and 85 +/- 4% of baseline, respectively) and desflurane 3%, 6%, and 9% (74 +/- 5%, 84 +/- 4%, and 86 +/- 11% of baseline, respectively) enhanced the recovery of force. This effect was abolished in the presence of wortmannin (56 +/- 5% of baseline for sevoflurane 2%+wortmannin; 56 +/- 3% of baseline for desflurane 6%+wortmannin). Wortmannin alone had no effect on the recovery of force (57 +/- 7% of baseline).

CONCLUSION

In vitro, sevoflurane and desflurane post-conditioned human myocardium against hypoxia through activation of phosphatidylinositol-3-kinase.

Video recording of cardiac surgical procedures: what the surgeon needs to know

In the past, rudimentary devices were used to record surgical operations. Currently, the introduction of technologic advances such as high-definition television and the miniaturization of high-resolution digital video cameras provides an opportunity for making significantly enhanced surgical records. These enhancements, coupled with the recent advances in telemedicine and surgical simulation, will improve cardiac surgery training and skill acquisition, decrease operative times and costs, minimize morbidity, and improve overall patient care. The present paper provides a discussion of the media technology offered to surgeons for recording a surgical procedure on video. Hardware technology, including different types of cameras and analogical or digital post processing methods, are reviewed with a surgical ''eye''. This ''how to'' paper provides practical suggestions to surgeons in order to enhance surgical video recording.

Le phéochromocytome comme cause inhabituelle de choc cardiogénique

The authors reported a case involving a young patient with a cardiogenic shock associated to an acute pulmonary oedema. According to the seriousness of the shock, an external ventricular assist device (VAD) was initially inserted and replaced thereafter because of the cardiovascular instability, by an external pneumatic biventricular assist device. A cardiogenic shock induced by an acute adrenergic myocarditis due to a phaeochromocytoma was diagnosed. The patient was weaned from the VAD on day 84 and was scheduled for elective surgery of the phaeochromocytoma on day 93. The authors discussed the time of the surgery according to the anticoagulation therapy necessary to the VAD and the necessary caution taken if a cardiogenic shock appeared around surgery.

Less invasive radial artery harvest

BACKGROUND

Recent studies have sparked a renewed interest in the use of autogenous radial arteries in coronary operations. Some concerns have been found about sequelae of conventional harvesting. A less invasive technique for radial artery harvesting has been proposed by others using endoscopic devices. This technique is time consuming, needs expensive instrumentation and an important learning curve.

METHODS

A new less invasive approach for radial harvesting has been developed with a light assisted retractor under direct vision. A small skin incision, median in the forearm, is followed by dissection of the proper plane of the artery. A subcutaneous tunnel is created around the vessel and all the branches are ligated or clipped. The dissection of the pedicle under the skin is completed with the aid of a modified light assisted retractor, originally designed for the saphenous vein harvesting. The incision is closed after heparin reversal with a small redon as drainage.

RESULTS

A preliminary serie of 15 patients have been operated with this technique. In all patients the radial artery was patent and functional at the postoperative angiography. Morbidity included only a light hematoma at the beginning of our experience.

CONCLUSION

This less invasive technique for the radial artery harvesting appears to be an excellent surgical compromise between the open technique and the endoscopic procedure; it is easy to perform, the learning curve is acceptable and it offers an excellent aesthetic result.

Pre-operative balloon counterpulsation and off-pump coronary surgery for high-risk patients

Coronary artery bypass surgery (CABG) can be performed less invasively without cardiopulmonary bypass (CPB). Multivessel off-pump CABG (OPCAB) is challenging in patients with critical left main stenosis (> 70%) and/or severe ventricular dysfunction (ejection fraction < 0.35) Our objective was the evaluation of efficiency of intra aortic balloon pump (IABP) preoperatively in this high-risk group in order to perform OPCABG safely.

MATERIAL AND METHOD

In a consecutive 10-month period (out of 88 OPCABG patients) 23 high-risk patients were treated and were compared with 15 on-pump patients (out of 69) with the same criteria.

RESULTS

Preoperative implantation of IABP was significantly higher in the OPCABG group (70% vs 46%, p < 0.05). No conversion to CPB was required in the OPCABG group. Post-operative angiography was systematically performed and demonstrated 97.5% patency of anastomosis. No device-related complications occurred. No difference was found concerning age, risk factors, emergency surgery, ejection fraction, mean number of grafts per patient (2.64 versus 2.75) and average operating time. In contrast, OPCABG demonstrated a trend toward reduced morbidity in terms of atrial fibrillation, reexploration for bleeding and prolonged ventilator requirement > 12 h. Mortality was less in the OPCABG group (p < 0.05).

CONCLUSION

More randomized controlled trials are needed to evaluate the true efficacy of elective IABP in OPCABG high-risk patients. Until such studies are evaluated, and therefore because older and sicker patients now constitute a greater percentage of candidates for OPCABG, the timing of application of the IABP is warranted. These results may further justify preoperative use of the IABP in a large proportion of this group of patients.

Surgical treatment of abdominal aortic aneurysms associated with aortic valve incompetence: strategies and outcomes

BACKGROUND

The exact incidence of associated aortic valve incompetence (AVI) and abdominal aortic aneurysm (AAA) in the general population is not known. In recent years, we have observed this association with increasing frequency. This observation is probably due to the extensive preoperative screening of the cardiac and vascular status of patients who are candidates for surgical procedures. The choice of the optimal surgical strategy is needed to achieve low operative morbidity and mortality. The present study reviews our experience with a subset of patients suffering the association of AVI and large AAA. Surgical strategy, clinical management and outcome are presented.

METHODS

Between January 1982 and May 2000, 76 patients with the association of AAA and AVI have been evaluated in our institution. Forty-four patients have been treated for both AAA and aortic valve (AV) regurgitation. These patients have been divided into three groups on the basis of the surgical strategy adopted. Group 1: combined procedure (16 patients); group 2: AAA repair prior to AV surgery (nine patients); group 3: AV surgery prior to aneurysm repair (19 patients).

RESULTS

Hospital mortality was 4.5% (two patients); overall mortality was 6.8% (three patients).

CONCLUSIONS

In patients with AAA and AVI, an accurate and complete preoperative evaluation is essential. Surgical strategy should be individualized on the basis of the cardiac preoperative status.