Quantification of aortic valve calcification in contrast enhanced computer tomography

Introduction

Aortic valve calcification (AVC) is linked to higher gradients and worse prognosis in aortic valve stenosis. Current guidelines recommend calcium scoring of the aortic valve as additional factor for decision making in low-flow, low-gradient aortic stenosis. Calcium Scoring is performed by native computed tomography (CT). For planning of interventional valve replacement (TAVR) a second scan with contrast agent (CECT) is needed at the cost of additional radiation exposure and work up time. The aim of this study is to assess and validate an estimate conversion factor of aortic valve quantification by using CECT without native imaging.

Methods

The Agatston score was measured on native CT in 45 patients and used as a reference. In contrast enhanced CT, mean aortic attenuation values in Hounsfield units (HU) were determined by placement of a region of interest in the ascending aorta with a standard deviation of 4xHU for calcification threshold. AVC was segmented semi-automatically. A conversion formula was created by plotting of native Agatston score versus aortic valve calcification segmented on contrast enhanced CT and linear regression. Validation of calculated conversion formula was established by Intra-class coefficient (ICC) and Bland Altman analysis.

Results

The linear regression model yielded an Agatston score conversion formula of 691 + 1.83 × AVCCECT. Validation of the formula in a validation cohort (n=20) showed high agreement (r2=0.802, ICC 0.915 (CI 95%: 0.786–0.966) p<0.001, p=0.055).

Conclusion

Approximation by our calculated conversion factor from contrast enhanced CT has shown excellent reliability to determine aortic valve calcification. Further studies are needed to extend this finding to larger cohorts and diverse clinical environments.

Funding Acknowledgement

Type of funding sources: None.

Comparison of various late gadolinium enhancement magnetic resonance imaging methods to high-definition voltage and activation mapping for detection of atrial cardiomyopathy

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Medtronic

Background/Introduction

Atrial cardiomyopathy (ACM) is associated with the progression from paroxysmal through persistent to permanent atrial fibrillation (AF) and increased arrhythmia recurrence rates after pulmonary vein isolation (PVI).

Purpose

We compare the most common left atrial (LA) late gadolinium enhancement magnetic resonance imaging (LGE-MRI)-methods (Utah-method and image-intensity-ratio (IIR)-methods) and endocardial voltage mapping for ACM-detection and outcome prediction after PVI for AF.

Methods

In this prospective study, 37 ablation-naive patients (66±9 years, 84% male) with persistent AF were included and electrically cardioverted into sinus rhythm. Subsequently, they underwent LA-LGE-MRI and high-definition voltage and activation mapping (2129±484 sites) in sinus rhythm prior to PVI. MRI-post-processing-analyses were performed by two independent expert laboratories (Marrek for the Utah segmentation as describers of this methodology and Adas 3D medical as developers of the Adas software for the IIR-methods) which were blinded to any clinical data. Arrhythmia recurrence was recorded within 12 months following PVI.

Results

The global ACM-extent was highly variable: median LA low-voltage substrate (LA-LVS) was 12.9% at <1.0mV and 2.7% at <0.5mV; median LA-LGE-extent using the Utah-method was 18.3% and 0.03%-93.1% using the IIR-methods. LA activation time was significantly correlated with LA-LVS (r=0.76 at <0.5mV and r=0.82 at <1.0mV, both p<0.0001), but not with LA-LGE-extent.

The highest regional matching between LA-LVS <0.5mV and LA-LGE was found for the anterior wall in 57% of patients using the Utah-method and in 59% using IIR 1.20. The corresponding values for the posterior wall were 19% and 38%, respectively.

Arrhythmia recurrence occurred in 15 (41%) patients. Freedom from arrhythmia was significantly lower in those with relevant LA-LVS (≥2cm2 at 0.5mV) but not in those with relevant LGE (Utah-stages III&IV): 43% versus 81%, p=0.009 and 50% versus 67%, p=0.338, respectively. Furthermore, relevant

LA-LVS was the only predictor for arrhythmia recurrence in multivariate regression analysis.

Conclusion

The different LA-LGE-MRI methods have large dicrepancies regarding extent and distribution of ACM and are different to the extent and regional distribution of LA-LVS as assessed in endocardial high-definition voltage mapping in sinus rhythm. Further improvements of the LA-LGE-MRI-methods are required to enable correct diagnosis of ACM and for future evaluation of MRI-guided ablation protocols.

A human factors approach to evaluate predicators of acute care nurse occupational fatigue

Nurses function at the point of care and assume a significant role in intercepting errors. They work in a mentally and physically demanding profession that is comprised of shift-work, subjecting nurses to considerable fatigue. Yet, few studies constructed a comprehensive model that integrates personal and occupational factors to explore their relationship with various types of fatigue (acute, chronic, physical, mental, and total). Here, we examine this type of comprehensive fatigue-model, in a report that represents one aim of a larger, mixed-methods study. The study sample comprised of 1137 registered nurses working in eight hospitals in a Midwestern state. Nurses reported higher levels of acute and total fatigue than chronic and physical fatigue. Staffing and resource adequacy, exercise, and sleep were among the strongest predictors. Since fatigue is a multi-faceted construct, a comprehensive fatigue-management strategy that targets both day and night-shift nurses is the optimal way to manage nurse fatigue.

Prosthesis position and its influence on complications after transcatheter aortic valve implantation with self-expanding valves

Background/Introduction

Prior studies in patients with transcatheter aortic valve implantation (TAVI) demonstrated an influence of transcatheter heart valve (THV) position on the occurrence of new conductions disturbances (CD) and paravalvular leakage (PVL) post TAVI in balloon-expandable valves (BEV).

Purpose

Purpose of this study was to investigate the THV position and its influence on the occurrence of CD and PVL in self-expanding valves (SEV).

Methods

We performed fusion imaging of pre- and post-procedural computed tomography angiography in 104 TAVI-patients (all with Evolut R) to receive a 3-D reconstruction of the THV within the native annulus region. The THV length below the native annulus was measured for assessment of implantation depth. Electrocardiograms pre-discharge were assessed for conduction disturbances (CD), PVL was determined in transthoracic echocardiography.

Results

The mean implantation depth of the THV in the whole cohort was 4.3±3.0 mm. Using the best cut-off of >4 mm in receiver operating characteristic curve analysis (sensitivity 83.3%, specificity 60.0%) patients with lower THV position developed more new CD after TAVI (68.2 vs. 23.7%, P<0.001). A deep THV position was identified as the only predictor for new CD after TAVI (odds ratio [CI]: 1.312 [1.119–1.539], P=0.001). The implantation depth showed no influence on the grade of PVL (r=0.052, P=0.598).

Conclusions

In patients with TAVI using the Evolut R SEV, a lower THV positioning (>4 mm length below annulus) was a predictor for new conduction disturbances. In contrast, prosthesis position was not associated with the extent of PVL.

Funding Acknowledgement

Type of funding sources: None.

[Atypical depression as a risk factor for obstructive sleep apnea syndrome in young adults]

OBJECTIVES

In the literature, several studies have investigated the particular relationship between major depression and obstructive sleep apnoea syndrome (OSAS). However, most of these studies have focused primarily on middle-aged to elderly individuals (≥40 years) which means that this problem has been little studied in young adults (<30 years). Nevertheless, in young adults the prevalence of major depression (particularly its atypical subtype) is not negligible, which seems to justify carrying out additional investigations in order to allow a better understanding of the potential role played by major depression in the pathophysiology of OSAS in this particular subpopulation. The aim of this study was therefore to empirically investigate the prevalence of OSAS in young adults and to study the risk of OSAS associated with major depression in this particular subpopulation.

METHODS

Polysomnographic and demographic data from 264 young adults were collected from the Erasme Hospital Sleep Laboratory (Brussels, Belgium) database to enable our analyses. During their two-night stay (including a first night of habituation and a night of polysomnography) at the Sleep Laboratory, these individuals underwent a complete somatic assessment (including blood test, electrocardiogram, daytime electroencephalogram and urinalysis), a systematic psychiatric assessment by a unit psychiatrist and an assessment of their complaints related to sleep. These different steps made it possible to systematically diagnose all somatic pathologies, psychiatric disorders according to the diagnostic criteria of the DSM-IV-TR and sleep pathologies according to the diagnostic criteria of the AASM. This allowed the selection of young adults included in our study based on our inclusion and exclusion criteria. Polysomnographic recordings from our Sleep Laboratory were visually scored according to AASM criteria. An obstructive sleep apnoea-hypopnoea index ≥5/hour was used for the diagnosis of OSAS. At the statistical level, in order to allow our analyses, we subdivided our sample of young adults into two groups: a control group without OSAS (n=215) and a patient group with OSAS (n=49). After checking the normal distribution of our data, normally distributed data were analysed with t-tests whereas asymmetrically or dichotomously distributed data were analysed with Wilcoxon tests or Chi² tests. Univariate regression models were used to study the risk of OSAS associated with major depression (categorized: absent, typical, atypical) in young adults and potential confounding factors. In multivariate regression models, the risk of OSAS associated with major depression (categorized: absent, typical, atypical) in young adults was adjusted only for confounding factors significantly associated with OSAS during univariate analysis. These confounding factors were introduced in a hierarchical manner in the various multivariate regression models constructed.

RESULTS

The prevalence of OSAS in our population of young adults was 18.6 %. During univariate analyses, atypical depression [OR 2.51 (95% CI 1.18-5.32), p-value=0.014], male gender [OR 4.53 (95% CI 2.20-9.34), P-value <0.001], presence of snoring [OR 2.51 (95% CI 1.33-4.75), P-value=0.005], presence of at least one cardio-metabolic alteration [OR 2.26 (95% CI 1.19-4.28), P-value=0.012], body mass index>30 kg/m² [OR 4.55 (95% CI 2.07-10.03), P-value <0.001] and ferritin ≥150 μg/L [OR 3.28 (95% CI 1.69-6.36), P-value<0.001] were associated with increased risk of OSAS in our population of young adults. After adjusting for these major confounding factors associated with OSAS (gender, body mass index, cardio-metabolic alterations, ferritin level, and snoring) in the four models studied, multivariate regression analyses confirmed that unlike typical depression, atypical depression [OR 3.09 (95% CI 1.26-7.54), P-value=0.019] was a risk factor for OSAS in young adults.

CONCLUSIONS

In our study, we demonstrated that the prevalence of OSAS was 18.6 % in young adults referred to the Erasme Hospital Sleep Laboratory. In addition, we have shown that unlike typical depression, atypical depression was associated with an increased risk of OSAS in young adults, which seems to justify more systematic research of this pathology in young adults suffering from atypical depression in order to allow the establishment of adapted therapeutic strategies and avoid the negative consequences associated with the co-occurrence of these two pathologies.

Flow rate and stroke volume index as predictors of mortality in patients undergoing transcatheter aortic valve implantation

Background

Reduced flow rate and stroke volume are a common finding in patients with severe aortic stenosis. The aim of this study was to assess their impact on mortality in patients undergoing transcatheter aortic valve implantation (TAVI).

Methods

A total of 1080 patients with severe aortic stenosis who underwent TAVI between 2007 and 2017 were followed for a mean of 2.4±1.6 years. Patients were allocated into two groups according to flow rate (cut-off 200mL/s), 805 patients had a normal flow rate and 275 patients had reduced flow rate. Long-term survival was summarized using Kaplan-Meier curves and Cox-regression models.

Results

Patients with reduced flow rate were older (83.8±5.5 years; P&lt;0.01) with more diabetics (36.7% P=0.02). Kaplan-Meier survival curves demonstrated inferior survival for patients with reduced flow rate (global log rank, P&lt;0.01), Multivariable Cox-regression analysis (adjusted for age, creatinine, diabetes, hemoglobin and presence of atrial fibrillation) confirmed flow rate as an independent risk factor of all-cause mortality (HR: 0.998; 95%-CI: 0.997–0.999; P&lt;0.01). Similar results were obtained for stroke volume index (SVI).

Conclusion

Patients with a reduced flow rate exhibit an increased mortality even after TAVI (similar to patients with reduced SVI) and should therefore be carefully evaluated in the heart-team.

PostTAVI survival according to flow rate

Funding Acknowledgement

Type of funding source: None

Invasive exercise hemodynamics in patients with severe primary mitral regurgitation and preserved ejection fraction predicts future valve surgery

Background

The role of invasive exercise hemodynamics in the management of asymptomatic patients with severe primary mitral regurgitation (MR) is unclear.

Methods and results

We compared the predictive power of parameters of invasive exercise testing for future valve surgery to guideline-defined non-invasive criteria. Maximal pulmonary capillary wedge pressure (PCWP), PCWP normalized to workload and weight (PCWL), and invasive maximal systolic pulmonary artery pressure (SPAP) were assessed in 113 asymptomatic patients with severe primary MR between 1996 and 2012. Mean age was 52±11 years, 16% were female, ejection fraction was ≥55% in all patients. During a median follow up of 4.5 years (IQR2.0; 8.3) 54 patients (48%) underwent valve surgery. In univariate analysis PCWP (P&lt;0.001), PCWL (P&lt;0.001), and maximal SPAP (P=0.009) were significantly associated with future mitral valve surgery. In multivariate analysis maximum PCWP and PCWL predicted future mitral valve surgery (HR 2.1 (1.44–3.10), P=0.005 and HR 1.31 (1.14–1.52), P&lt;0.001, respectively) whereas SPAP did not. Adding maximum PCWP &gt;25mmHg to a Cox regression model based on non-invasive guideline criteria resulted in a significant increase in the area under the curve (0.61 to 0.68, P=0.02).

Conclusion

In asymptomatic patients with severe primary mitral regurgitation and preserved left ventricular function invasive exercise hemodynamics improves information derived from current non-invasive guideline criteria.

Figure 1

Funding Acknowledgement

Type of funding source: None

Influence of prosthesis related factors on the occurrence of early leaflet thrombosis after transcatheter aortic valve implantation

Background

Early leaflet thrombosis (LT) is a well described phenomenon after transcatheter aortic valve implantation (TAVI) with an incidence between 10 and 16%. So far, data about predictors of LT are scarce.

Purpose

The purpose of the study was to investigate the influence of prosthesis related factors on the occurrence of LT.

Methods

Fusion imaging of pre- and post-procedural CTA was performed in 140 TAVI-patients (55 with LT, 85 without LT) to obtain a 3D-reconstruction of the transcatheter heart valve (THV) within the native annulus region. All patients received a balloon-expandable Sapien 3 THV. The length of the THV above and below the native annulus was measured within the fused images to assess the implantation depth. The deployed THV area was quantified on three heights (left ventricular outflow tract end, center of the stent, aortic end) to determine the average expansion of the prosthesis as percent of the nominal area. We also calculated the extent of prosthesis waist in percent of maximum area. The stent tilt was determined in relation to the annulus plane.

Results

After multivariate adjustment the extent of THV expansion (odds ratio per 10 percent [CI]: 0.660 [0.555–0.786], P&lt;0.001) and waist (odds ratio per 10 percent [CI]: 0.725 [0.615–0.854], P&lt;0.001) had significant, independent influence on the occurrence of LT. Neither the implantation depth nor the stent tilt showed any influence on LT manifestation (P=0.393 and 0.578).

Conclusion

Our study suggests that less than fully expanded Sapien 3 THVs are more prone to LT, whereas some degree of waist was protective. These deployment characteristics may help identify patients who qualify for intensified surveillance.

Funding Acknowledgement

Type of funding source: None

[Support for insomnia : Recommendations for practice in general medicine]

In Belgium, poor sleep complaints are numerous and frequent in the general population. Of these complaints, one of the most important is insomnia. Acute onset and chronicity of insomnia can be explained by different models based on genetic criteria, neurophysiological, neuroendocrine, neuroimmunological and neuroimaging. Insomnia can be associated with a lot of somatic and psychiatric comorbidities. The diagnosis of insomnia is primarily a clinical diagnosis based on medical history and physical examination. Different tools can help us in our approach, such as self-questionnaires and sleep diaries while additional tests (polysomnography and actigraphy) should be reserved for research of associated sleep disorders and for unclear situations. The management of insomnia can be non-drug treatment (exercise, light therapy, acupuncture and self-treatment cognitive behavioral therapy) but also drug treatment (benzodiazepine, Z-DRUGS, melatonin, antidepressants, herbal medicines, neuroleptics and antihistaminics). Each of these approaches has advantages and disadvantages that must be considered when choosing treatment. The aim of this review is to allow general practitioners to better understand the mechanisms of insomnia and to have recommendations for the diagnosis and treatment of insomnia.

Acute effects of superimposed electromyostimulation during cycling on myokines and markers of muscle damage

OBJECTIVES

The purpose of the present study was to evaluate the effects of superimposed electromyostimulation (E) during cycling on myokines and markers of muscle damage, as E might be a useful tool to induce a high local stimulus to skeletal muscle during endurance training without performing high external workloads.

METHODS

13 subjects participated in three experimental trials each lasting 60 min in a randomized order. 1) Cycling (C), 2) Cycling with superimposed E (C+E) and 3) E. Interleukin-6 (IL-6), brain-derived neurotrophic factor (BDNF), creatine kinase (CK) and myoglobin were determined before (pre) and 0', 30', 60', 240' and 24h after each intervention.

RESULTS

Only C+E caused significant increases in levels of CK and myoglobin. BDNF and IL-6 significantly increased after C and C+E, however increases for IL-6 were significantly higher after C+E compared to C.

CONCLUSION

The present study showed that superimposed E during cycling might be a useful tool to induce a high local stimulus to skeletal muscle even when performing low to moderate external workloads. This effect might be due the activation of additional muscle fibers and mild eccentric work due to the concomitant activation of agonist and antagonist. However the higher load to skeletal muscle has to be taken into account.

Myocardial effects of local shock wave therapy in a Langendorff model

OBJECTIVE

Applying shock waves to the heart has been reported to stimulate the heart and alter cardiac function. We hypothesized that shock waves could be used to diagnose regional viability.

METHOD

We used a Langendorff model to investigate the acute effects of shock waves at different energy levels and times related to systole, cycle duration and myocardial function.

RESULTS

We found only a small time window to use shock waves. Myocardial fibrillation or extrasystolic beats will occur if the shock wave is placed more than 15 ms before or 30 ms after the onset of systole. Increased contractility and augmented relaxation were observed after the second beat, and these effects decreased after prolonging the shock wave delay from 15 ms before to 30 ms after the onset of systole. An energy dependency could be found only after short delays (-15 ms). The involved processes might include post-extrasystolic potentiation and simultaneous pacing.

CONCLUSION

In summary, we found that low-energy shock waves can be a useful tool to stimulate the myocardium at a distance and influence function.

Simplified detection of myocardial ischemia by seismocardiography. Differentiation between causes of altered myocardial function

Seismocardiography (SCG) is a noninvasive technique for recording cardiac vibrations. Changes in these waves have been correlated with chronic and acute alterations in myocardial function. This analysis is complex and clinical integration limited. The current study aimed to simplify the utilization of SCG by fast Fourier transformation for a reliable discrimination between different intra- and postoperative causes of hypotension (i.e., myocardial ischemia or hypovolemia). We operated on nine pigs and recorded SCG at baseline, at hypovolemia (occlusion of the inferior vena cava), and at ischemia (occlusion of the right coronary artery). In conclusion, SCG enables detection and differentiation of ischemia and hypovolemia as important causes of altered myocardial function during and after surgery. Thus, this simple and noninvasive diagnostic tool may be used intra- and postoperatively to identify patients at risk.

Effect of anesthesia and cerebral blood flow on neuronal injury in a rat middle cerebral artery occlusion (MCAO) model

Middle cerebral artery occlusion (MCAO) models have become well established as the most suitable way to simulate stroke in experimental studies. The high variability in the size of the resulting infarct due to filament composition, rodent strain and vessel anatomy makes the setup of such models very complex. Beside controllable variables of homeostasis, the choice of anesthetics and the grade of ischemia and reperfusion played a major role for extent of neurological injury. Transient MCAO was induced during either isoflurane or ketamine/xylazine (ket/xyl) anesthesia with simultaneously measurement of cerebral blood flow (CBF) in 60 male Wistar rats (380-420 g). Neurological injury was quantified after 24 h. Isoflurane compared with ket/xyl improved mortality 24 h after MCAO (10 vs. 50 %, p = 0.037) and predominantly led to striatal infarcts (78 vs. 18 %, p = 0.009) without involvement of the neocortex and medial caudoputamen. Independent of anesthesia type, cortical infarcts could be predicted with a sensitivity of 67 % and a specificity of 100 % if CBF did not exceed 35 % of the baseline value during ischemia. In all other cases, cortical infarcts developed if the reperfusion values remained below 50 %. Hyperemia during reperfusion significantly increased infarct and edema volumes. The cause of frequent striatal infarcts after isoflurane anesthesia might be attributed to an improved CBF during ischemia (46 ± 15 % vs. 35 ± 19 %, p = 0.04). S-100β release, edema volume and upregulation of IL-6 and IL-1β expression were impeded by isoflurane. Thus, anesthetic management as well as the grade of ischemia and reperfusion after transient MCAO demonstrated important effects on neurological injury.

Determination of total polar parts with new methods for the quality survey of frying fats and oils

During the frying process the fat undergoes several chemical and physical changes caused by heat, water and atmospheric oxygen. With prolonged heating time the accumulation of deterioration products leads to organoleptic failures and a decrease of the nutritive value. For the quality control of frying fats or oils the determination of total polar parts by preparative column chromatography is an approved standard method. Many attempts were undertaken to replace this time and chemical consuming method. To substitute for the determination of polar components by column chromatography the measurement of dielectric properties with a food oil sensor, nuclear magnetic resonance spectroscopy (NMR) and near infrared spectroscopy (NIR) proved to be suitable.

The effects of metoprolol on hypoxia- and isoflurane-induced cardiac late-phase preconditioning

BACKGROUND

The detrimental effects of metoprolol on early-phase preconditioning (pc) have been proven. The late phase of pc is mediated via gene transcription and cyclooxygenase-2 (COX-2) was identified as one of the key mediators. The effect of metoprolol on this is yet unknown as is its effect on cellular energy metabolism and reactive oxygen species (ROS) creation.

METHODS

Cardiomyocytes from neonatal rats were cultured and randomly assigned to four pairs of treatment groups. In each pair, one group received metoprolol at a dose of 0.5 μg/ml medium. One pair served as a control; the others were subjected to 5 h of hypoxia 24 h after either hypoxia-induced, isoflurane-induced or no pc. Cell survival was measured with a redox indicator for cell metabolism. COX-2 transcription, ATP and ROS creation were measured.

RESULTS

Whereas both ischemic and isoflurane pc produced mild beneficial effects (48.8±6.0% and 48.2±7.8% of surviving cells, respectively) compared with unpreconditioned controls (35.9±7.9%, P<0.01 for both), adding metoprolol was detrimental for both kinds of pc (hypoxia: 31.5±3.5%; isoflurane: 25.7±3.8%, P<0.001) but not in the unpreconditioned group (39.4±4.9%). mRNA for COX-2 was up to 10-fold elevated in pc cells. This induction was suppressed by metoprolol. Hypoxic and isoflurane-induced pc showed significant differences in ATP balance and ROS generation.

CONCLUSION

Metoprolol abolishes the protection of both isoflurane- and hypoxia-induced late-phase pc in our model. This effect is accompanied by the blockade of COX-2 induction. The differences between hypoxic and isoflurane pc in ATP and ROS creation allow to presume distinct pathways on the mitochondrial level.

Accidental renal injury by an external heating device during surgery in rats

Hypothermia can be caused by anaesthesia and/or surgery and represents a daily challenge in the operating room. Experimental animal surgery settings typically use heating pads or warming blankets to maintain the rodent's body temperature during long-lasting experiments. Warming is crucial in small animal experiments because these animals quickly lose temperature due to their large body surface to body weight ratio. While establishing a left ventricular infarction model in rats, we inserted a rectal temperature probe. The heating pad's set point was 37°C. Although a dual set point control circuit should prevent overheating, we observed a maximum heating pad's surface temperature of 43°C between the animal's back and the surface of the heating pad. At the end of the experiments, which lasted up to 8 h, the animals showed severe haematuria and segmental kidney damage. We hypothesized that overheating of the heating pad and uneven distribution of temperature led to kidney damage. Therefore, the maximal temperature of commonly used heating pads must be tightly controlled to avoid overheating, which may cause kidney or tissue injury, may falsify the experimental data and could influence the study results.

Xenon and isoflurane improved biventricular function during right ventricular ischemia and reperfusion

BACKGROUND

Although anesthetics have some cardioprotective properties, these benefits are often counterbalanced by their negative inotropic effects. Xenon, on the other hand, does not influence myocardial contractility. Thus, xenon may be a superior treatment for the maintenance of global hemodynamics, especially during right ventricular ischemia, which is generally characterized by a high acute complication rate.

METHODS

The effects of 70 vol% xenon and 0.9 vol% isoflurane on biventricular function were assessed in a porcine model (n=36) using the conductance catheter technique, and the expression of the type B natriuretic peptide (BNP) gene was measured. The animals underwent 90 min of right ventricular ischemia followed by 120 min of reperfusion. A barbiturate-anesthetized group was included as a control.

RESULTS

Cardiac output was compromised in unprotected animals during ischemia by 33+/-18% and during reperfusion by 53+/-17%. This was mainly due to impaired contractility in the left ventricle (LV) and increased stiffness. Isoflurane attenuated the increase in stiffness and resulted in a higher preload. In contrast, xenon increased the right ventricular afterload, which was compensated by an increase in contractility. Its effects on diastolic function were less pronounced. Upregulation of BNP mRNA expression was impeded in the remote area of the LV by both isoflurane and xenon.

CONCLUSIONS

Xenon and isoflurane demonstrated equipotent effects in preventing the hemodynamic compromise that is induced by right ventricular ischemia and reperfusion, although they acted through somewhat differential inotropic and vasodilatory effects.

Anti-ischemic effects of inotropic agents in experimental right ventricular infarction

BACKGROUND

Right ventricular (RV) function is an important determinant of survival after myocardial infarction. The efficacy of reperfusion therapy might be increased by the cardioprotective action of inotropic agents, which are used for symptomatic therapy in situations with compromised hemodynamics. Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of milrinone, levosimendan and dobutamine on the extent and degree of myocardial injury.

METHODS

IR injury was induced by temporary ligation of the distal right coronary artery for 90 min, followed by 120 min of reperfusion. Treatment was initiated 30 min after coronary artery occlusion. A bolus of milrinone (n=12; 50 microg/kg) and levosimendan (n=10; 24 microg/kg) was applied in different groups, followed by continuous infusion of the drugs at 0.5 and 0.2 microg/kg/min, respectively. The effects on myocardial injury and inflammation were compared with a control (n=12) and a dobutamine group (n=10), where treatment was started with an infusion of 5 microg/kg/min.

RESULTS

Milrinone and levosimendan reduced the resulting infarct size with respect to the area at risk (41.7+/-10.2%, 45.7+/-8.1%) when compared with the control group (58.3+/-6.1%). In contrast, dobutamine had no effect (55.8+/-7.7%). All drugs reduced the number of neutrophils infiltrating into the different myocardial regions and the circulating levels of interleukin-6. Increased levels of tumor necrosis factor alpha during reperfusion were only abated by milrinone and levosimendan.

CONCLUSIONS

Cardioprotective properties of milrinone and levosimendan were demonstrated for the first time in a clinically relevant model of RV infarction.

Combining magnetic resonance imaging and ultrawideband radar: a new concept for multimodal biomedical imaging

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area.

Xenon: recent developments and future perspectives

The noble gas xenon exerts favorable anesthetic properties along with remarkable hemodynamic stability in healthy patients undergoing elective surgery. Recent investigations documented that it does not prolong the duration of widely used neuromuscular blocking agents, including mivacurium and rocuronium. Some studies also suggest reduced neurocognitive compromise in the very early phase after general anesthesia. These properties differ from those observed for conventional inhalational anesthetics like isoflurane, desflurane and sevoflurane. However, a wider use of xenon in daily clinical routine has been limited owing to its higher price and technical restraints regarding economic delivery. Although there are controversial opinions, xenon seems to exert its main anesthetic features via the glutamate receptor. Recently, a novel binding cavity on the NMDA-subtype glutamate receptor has been elucidated that is occupied by xenon as well as isoflurane. Studies utilizing advanced imaging technologies have furthermore revealed that xenon markedly suppresses cerebral blood flow and glucose metabolism in distinct regions of the human brain. These investigations promise to further the understanding of the basic mechanisms underlying the induction and maintenance of anesthesia in general. Results from in vitro studies and various animal models have consistently demonstrated organoprotective properties of xenon, mainly in settings of ischemia and reperfusion injury. Interestingly, these effects have frequently been observed at subanesthetic concentrations and seem to be synergistic when used in combination with therapeutic hypothermia. Future studies will have to prove whether the high costs of xenon administration might be outweighed by its ability to substantially reduce the sequelae of myocardial and cerebral ischemia.

Establishment of a porcine right ventricular infarction model for cardioprotective actions of xenon and isoflurane

BACKGROUND

Right ventricular (RV) function is an important determinant of post-operative outcome. Consequences of RV infarction might be limited by pre-conditioning with volatile anesthetic drugs. Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of isoflurane and xenon on the extent and degree of myocardial injury.

METHODS

IR injury was induced by a 90-min ligation of the distal right coronary artery and 120-min reperfusion in thiopental anesthetized pigs. A control group (n=12) was compared with two groups, which received either 0.55 minimum alveolar concentration (MAC) isoflurane (n=10) or xenon (n=12) starting 60 min before ischemia. Myocardial injury was described by three criteria: the infarct size related to area at risk (IS/AAR), the infiltration of neutrophils as determined by myeloperoxidase (MPO) activity, and the plasma levels of tumor necrosis factor alpha (TNFalpha), interleukin 6 (IL-6), myoglobin and troponin-T (TnT).

RESULTS

IS/AAR was reduced from 58.3+/-6.2% in the control group to 41.8+/-7.8% after isoflurane and 42.7+/-8.5% after xenon pre-treatment, which equals an absolute reduction of 16.5% [95% confidence interval (CI): 10.9-22.1] and 15.5% (95% CI: 10.1-20.9). The maximum increase of TnT could be observed within the xenon group. Both treatment groups were characterized by lower MPO activity, in the infarct and periinfarct region and lower plasma concentrations of TNFalpha and IL-6.

CONCLUSIONS

It could be demonstrated for the first time in a model of RV infarction that the continuous application of isoflurane or xenon before, during and after ischemia reduced the extent (size) and severity (inflammation) of myocardial injury.

A comparison of waste gas concentrations during xenon or nitrous oxide anaesthesia

BACKGROUND AND OBJECTIVE

The aim of this study was to compare waste gas concentrations during xenon or nitrous oxide anaesthesia.

METHODS

A total of 64 patients were included in this study. Gas concentrations were measured with a mass spectrometer during anaesthesia. The probes were taken beside the patient's head and thorax and at a height of 180 cm above and at the floor level.

RESULTS

In both groups, waste gas concentrations peak after intubation and extubation. Waste gas levels during xenon anaesthesia are low compared with nitrous oxide.

CONCLUSIONS

The low waste gas levels of xenon seem to be beneficial compared to nitrous oxide.

Xenon alters right ventricular function

BACKGROUND

In contrast to other volatile anesthetics, xenon produces less cardiovascular depression with fewer fluctuations of various hemodynamic parameters, but reduces cardiac output (CO) in vivo. Besides an increase in left ventricular afterload and reduction of heart rate, an impairment of the right ventricular function might be an additional pathophysiological mechanism for the reduction of CO. Therefore, we used an animal model to study the effects of xenon as a supplemental anesthetic on right ventricular function, especially right ventricular afterload.

METHODS

Right ventricular function was monitored with a volumetric pulmonary artery catheter in 11 pigs during general anesthesia with thiopental. Six animals received additional 70% (volume) xenon (equivalent to 0.55 MAC minimum alveolar concentration). Parameters for systolic function, afterload, and preload were calculated at baseline and during 50 min of xenon application, and in a corresponding control group. Significant differences were detected by multivariate analyses of variance for repeated measures.

RESULTS

Xenon reduced CO on average by 30% and increased pulmonary arterial elastance by 60%, which led to a reduction of the right ventricular ejection fraction by 25%. Whereas right ventricular preload remained stable, maximal slope of pulmonary artery pressure and the right ventricular elastance increased. No effect on the ratio of stroke work and end-diastolic volume was found.

CONCLUSION

The reduction in CO during xenon anesthesia was partly due to an impairment of the right ventricular function, mainly caused by an increased afterload, without an impairment of systolic ventricular function.

Xenon or propofol anaesthesia for patients at cardiovascular risk in non-cardiac surgery

BACKGROUND

The results of two European multi-centre trials on xenon anaesthesia led to the hypothesis that a xenon-based anaesthetic would keep left ventricular (LV) and circulatory function more stable than a propofol-based anaesthetic, in patients with coronary artery disease (CAD).

METHODS

In a prospective, randomized design, 40 patients of ASA classes III and IV with known CAD were anaesthetized for elective non-cardiac surgery with either xenon (n=20) or propofol (n=20), each combined with remifentanil. Target criteria were intraoperative LV function as evaluated by transoesophageal echocardiography (TOE: Tei index, circumferential fibre shortening), arterial pressure, and heart rate (HR).

RESULTS

Mean arterial pressure was decreased with propofol but was stable at pre-anaesthetic level with xenon (P<0.02) and HR was lower with xenon (P<0.01). The Tei index (also known as myocardial performance index) improved from 0.53 (0.14) to 0.45 (0.10) after 1 h with xenon and changed from 0.50 (0.14) to 0.55 (0.20) with propofol anaesthesia [means (SD); P=0.01 between the groups]. Deviation of circumferential fibre shortening from expected value after 1 h was -2 (14)% with xenon and -14 (18)% with propofol [means (SD); P=0.03]. There were no perioperative signs of acute myocardial ischaemia (TOE, ECG, and troponin T release).

CONCLUSIONS

Xenon anaesthesia provided a higher arterial pressure level than propofol, with no signs of cardiovascular compromise, in patients with CAD. Echocardiographic indices showed better LV function with xenon.