[Long COVID : which neuropsychological intervention ? The example applied at the Leenaards Memory Centre]

A "Long COVID" care management was created at the Leenaards Memory Centre (Lausanne University Hospital) to meet the high demand for neuropsychological examinations in the patients which have persistent symptoms for several months. A multidisciplinary evaluation specifically addressing aspects of fatigue and sleep as well as cognition has been developed to receive these patients. Depending on the severity of their symptoms, they are then oriented towards a holistic group treatment, integrating cognitive remediation including psycho-education, restorative and compensatory methods to cope with their cognitive difficulties, and tools to manage the various symptoms of COVID-long (fatigue, insomnia, stress, depression and reduced quality of life).

Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

Potential value of the low frequency/high frequency ratio of heart rate variability to guide atrial fibrillation ablation procedures

Funding Acknowledgements

Type of funding sources: None.

Background.

The  differentiation  between  vagally  and  non-vagally mediated  atrial fibrillation (AF)  could be useful  to decide  adding  ganglionated  plexi  ablation  (GPA)  to  pulmonary vein isolation (PVI)  in  patients with vagally mediated  AF  onset.

The role of the autonomic nervous system in triggering paroxysmal AF can be analyzed through heart rate variability (HRV) parameters. The low frequency/high frequency ratio (LF/HF) is used as an index of sympatho-vagal interaction. Based on clinical criteria, values of LF/HF <1.5 are considered to reflect an increase of vagal modulation. 

Purpose

Identify  patients with paroxysmal AF who may benefit from GPA in addition to PVI, based on analysis of HRV parameters

Material and methods

From our database of unselected Holter recordings containing paroxysmal AF episodes, 199 analyzable AF onsets were labelled. We analyzed HRV frequential parameters by segments every 300 RR intervals to identify adrenergic and vagal onsets of AF episodes. We categorized AF onsets, depending of their respective values of LF/HF. We also checked the relationship of these parameters to heart rate (HR). We followed the evolution of the mean normalized values of LF/HF from the beginning of the recordings to the AF onsets (see figure).

Results

We found a progressive increase of LF/HF  in normalized units  (mean [95% confidence interval]) from  2.44  [2.12-2.76]  to 3.12  [2.85-3.39]  in the adrenergic group  (n = 113)  and a  progressive decrease of LF/HF from  1.51 [1.28-1.75]  to 1.02 [0.95-1.09]  in the  vagal group (n = 86). Differences between adrenergic and vagal AF were highly significant using Mann-Whitney test (p < 0.001). A given patient shows the same type of AF in 80% of cases.  We found no correlation between frequential parameters and HR.

Conclusions

Our data show  potential  added value of  frequential  HRV  analysis  to  guide additional ganglionated  plexi ablation  to PVI. This  remains  to be demonstrated in a prospective study. The ratio LF/HF should be  considered  to optimize the decision-making process for  the ablation procedure. Abstract Figure. Frequential HRV parameters before AF

[Cognitive fitness to drive : feedback at Leenaards Memory Centre]

Cognitive impairment can interfere with the fitness to drive. An increase in requests to assess this aspect is observed at Leenaards Memory Centre. Changes in the law could be an explanatory factor. The views formulated in 2019 are mainly unfavorable because all the patients present cognitive disorders, generally attributed to Alzheimer's disease or a related disorder, but never linked with aging only. Moreover, unfavorable views are frequently expressed before the age of 75. Therefore, each patient is unique, and each decision is based neither on the patient's age or his diagnosis, but rather on his cognitive profile. In this article we discuss the reasons for an unfavorable view and discuss them in the context of the tasks of our centre.

Unravelling the black box of machine learning for atrial fibrillation forecast: role of heart rate variability and of premature beats

Background

The identification of patients still in sinus rhythm who will present one month later an atrial fibrillation episode is possible using machine learning (ML) techniques. However, these new ML algorithms do not provide any relevant information about the underlying pathophysiology.

Purpose

To compare the predictive performance for forecasting AF between a machine learning algorithm and other parameters whose pathophysiological mechanisms are known to play a role in the triggering of arrhythmias (i.e. the count of premature beats (PB) and heart rate variability (HRV) parameters)

Material and methods

We conducted a retrospective study from an outpatient clinic. 10484 Holter ECG recordings were screened. 250 analysable AF onsets were labelled. We developed a deep neural network model composed of convolutional neural network layers and bidirectional gated recurrent units as recurrent neural network layers that was trained for the forecast of paroxysmal AF episodes, using RR intervals variations. This model works like a black box. For comparison purposes, we used a “random forest” (RF) model of ML to obtain forecast results using HRV parameters with and without PB. This model allows the evaluation of the relevance of HRV parameters and of PB used for the forecast. We calculated the area under the curve of the receiving operating characteristic curve for the different time windows counted in RR intervals before the AF onset.

Results

As shown in the table, the forecasting value of the deep neural network model (ML) was not superior to the random forest algorithm. Prediction value of both decreased when analyzing the RR intervals further away from the onset of AF

Conclusions

These results suggest that HRV plays a predominant role in triggering AF episodes and that premature beats could add minor information. Moreover, the closer the window from AF onset, the better the accuracy, regardless of the method used. Such detection algorithms once implemented in pacemakers, might prove useful to prevent AF onset by changing pacing sequence while patients would still be in sinus rhythm, however this remains to be demonstrated

Funding Acknowledgement

Type of funding source: None

The influence of propofol and sevoflurane on intestinal motility during laparoscopic surgery

BACKGROUND

Volatile anaesthetics have an influence on small bowel peristalsis during laparoscopic surgery. A recent study concluded that desflurane increased intestinal motility compared to sevoflurane. Hence, a desflurane-based anaesthesia protocol may reduce surgical exposure during intestinal suturing or stapling due to small bowel hyperperistalsis. The effect of propofol on intestinal motility is not well studied. We tested the hypothesis that a propofol-remifentanil anaesthesia increases intestinal contractions in comparison with a sevoflurane-remifentanil anaesthesia.

METHODS

Patients scheduled for laparoscopic gastric bypass surgery were randomized in this single blind randomized controlled trial to receive remifentanil combined with sevoflurane or propofol (ISRCTN 12921661). Bispectral index monitoring was used to guide depth of anaesthesia. Visual observation of peristaltic waves was performed during 1 min at the planned site of the jejunostomy. Statistical analysis was performed using Wilcoxon two-sample test.

RESULTS

After obtaining written informed consent 50 patients were included. Groups were similar for demographic variables, and depth of anaesthesia during the observations. The median number of peristaltic waves was lower in the sevoflurane-remifentanil group compared to the propofol-remifentanil group (0 vs. 6, P < 0.001).

CONCLUSION

Propofol-remifentanil increases intestinal motility compared with sevoflurane-remifentanil during laparoscopic gastric bypass surgery. A sevoflurane-based protocol can help to avoid disturbing peristalsis.

Treatment of acquired flexural deformity of the distal interphalangeal joint in the horse: a retrospective study of 51 cases

Flexural deformity of the distal interphalangeal joint is an important disorder in horses, which can be acquired during the first year of life, often as a result of lateralization during grazing. In this retrospective study, the medical files of 51 cases presented at the Faculty of Veterinary Medicine of Ghent University (1999-2013) were analyzed, followed by a telephone questionnaire. In 65% of the conservatively treated patients, the hoof conformation corrected completely, which was not significantly different from what was seen in the surgically treated group (complete correction in 56% of cases). Foals treated conservatively before the age of six months and foals treated surgically before twelve months of age, had a significantly better chance of a successful correction than older foals. Moreover, cases in which treatment did not restore the hoof conformation completely, presented a significantly higher chance of (persisting) lameness and were significantly less likely to have an athletic career. Finally, this study proved a significant association between the hoof conformation of the dam and her foals.

Tooth loss, chewing efficiency and cognitive impairment in geriatric patients

BACKGROUND

Patients with dementia have poorer oral health and fewer teeth than their peers without cognitive impairment.

OBJECTIVE

The hypothesis of this study is that the number of natural teeth and the chewing efficiency are associated with cognitive functioning.

METHODS

This cross-sectional study included 29 patients diagnosed with dementia aged 75 years or older and 22 controls who were either cognitively normal (n = 19) or with mild cognitive impairment (n = 3). Neuropsychological, nutritional and dental assessments were performed. The chewing efficiency was evaluated with a two-colour mixing test.

RESULTS

Demented patients and controls presented with a mean of 4.9 and 6.5 teeth, respectively (n.s.). The number of natural teeth was not associated with dementia (p = 0.553). Same results were found for age (p = 0.746) and sex (p = 0.901). The chewing efficiency by visual inspection proved worse in participants with dementia than in the controls (p < 0.011) and explained 9.3% of the variance in the diagnosis of dementia. Neither dental state nor chewing efficiency was related to the nutritional state.

CONCLUSION

Chewing efficiency seems stronger associated with cognitive impairment than the number of teeth. Hence, in a more holistic approach for the geriatric assessment, the dental examination may be complemented by a chewing efficiency test.

I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study

BACKGROUND

Interscalene brachial plexus block (ISB) provides excellent, but time-limited analgesia. Dexamethasone added to local anaesthetics prolongs the duration of a single-shot ISB. However, systemic glucocorticoids also improve postoperative analgesia. The hypothesis was tested that perineural and i.v. dexamethasone would have an equivalent effect on prolonging analgesic duration of an ISB.

METHODS

We performed a prospective, double blind, randomized, placebo-controlled study. Patients presenting for arthroscopic shoulder surgery with an ISB were randomized into three groups: ropivacaine 0.5% (R); ropivacaine 0.5% and dexamethasone 10 mg (RD); and ropivacaine 0.5% with i.v. dexamethasone 10 mg (RDiv). The primary outcome was the duration of analgesia, defined as the time between performance of the block and the first analgesic request. Standard hypothesis tests (t-test, Mann-Whitney U-test) were used to compare treatment groups. The primary outcome was analysed by Kaplan-Meier survival analysis with a log-rank test and Cox's proportional hazards regression.

RESULTS

One hundred and fifty patients were included after obtaining ethical committee approval and patient informed consent. The median time of a sensory block was equivalent for perineural and i.v. dexamethasone: 1405 min (IQR 1015-1710) and 1275 min (IQR 1095-2035) for RD and RDiv, respectively. There was a significant difference between the ropivacaine group: 757 min (IQR 635-910) and the dexamethasone groups (P<0.0001).

CONCLUSIONS

I.V. dexamethasone is equivalent to perineural dexamethasone in prolonging the analgesic duration of a single-shot ISB with ropivacaine. As dexamethasone is not licensed for perineural use, clinicians should consider i.v. administration of dexamethasone to achieve an increased duration of ISB.

Hepatic Steatosis, Carbohydrate Intake, and Food Quotient in Patients with NAFLD

Is steatosis related to the spontaneous carbohydrate intake in patients with NAFLD? We performed dietary records for 24 patients with NAFLD, 3 months after their liver biopsy was performed and before the deliverance of a dietary advice. The food quotient, indicator of the proportion of calories from carbohydrates, was calculated as (1.00×%  calories from carbohydrates/100) + (0.70×%  calories from lipids/100) + (0.81×%  calories from proteins/100). The associations between diet variables and steatosis% on the hepatic biopsies were tested by regression analysis, and diet variables were compared according to the presence of fibrosis. The subjects displayed a large range of steatosis, 50.5% ± 25.5 [10-90], correlated with their energy intake (1993 ± 597 kcal/d, r = 0.41, P < 0.05) and food quotient (0.85 ± 0.02, r = 0.42, P < 0.05), which remained significant with both variables by a multivariate regression analysis (r = 0.51, P < 0.05). For the 17/24 patients with a hepatic fibrosis, the energy intake was lower (fibrosis: 1863 ± 503 versus others: 2382 ± 733 kcal/d, P < 0.05), and their food quotients did not differ from patients without fibrosis. Hepatic steatosis was related to the energy and carbohydrate intakes in our patients; the role of dietary carbohydrates was detectable in the range of usual carbohydrate intake: 32% to 58% calories.

Randomized clinical trial on the influence of anaesthesia protocol on intestinal motility during laparoscopic surgery requiring small bowel anastomosis

Background

Hyperperistalsis of the small bowel during laparoscopic surgery may cause mucosal prolapse and reduce exposure, making laparoscopic suturing or stapling more demanding for the surgeon. Although it is commonly accepted that both opioids and volatile anaesthetics induce intestinal paralysis, intestinal hyperactivity during anaesthesia is not uncommon. This randomized trial investigated the effect of different volatile anaesthetics on intestinal motility and the impact on surgeon satisfaction.

Methods

Patients scheduled for laparoscopic gastric bypass surgery were randomized to receive sevoflurane or desflurane in a balanced anaesthetic regimen. After surgical exposure peristaltic waves were counted over 1 min in a segment of the jejunum. Following evaluation of intestinal motility, N-butylhyoscine, an antimuscarinic anticholinergic agent that relaxes bowel smooth muscle cells, could be administered if the surgeon judged the intestinal motility as disturbing. The endpoints were number of peristaltic waves and incidence of N-butylhyoscine administration, a surrogate for surgeon satisfaction.

Results

Twenty-two patients were randomized to each group. The groups were similar in age, sex and body mass index. There was a statistically significant difference in intestinal motility between the desflurane and sevoflurane groups: median (range) 7 (0–12) versus 1 (0–10) waves counted over 1 min respectively (P &lt; 0·001). A higher proportion of patients in the desflurane group received N-butylhyoscine (10 of 22 versus 1 of 22 in the sevoflurane group; P = 0·004).

Conclusion

Desflurane increased intestinal motility and decreased surgeon satisfaction compared with sevoflurane during laparoscopic gastric bypass surgery. A sevoflurane-based anaesthetic protocol can help to avoid disturbing hyperperistalsis. Registration number: B39620097060 (http://www.clinicaltrials.be).

Perioperative management of phaeochromocytoma

Phaeochromocytoma is a rare catecholamine producing tumour, feared for its life threatening cardiovascular disturbances during anaesthesia. Improved medical and anesthetic management resulted in reduction of perioperative phaeochromocytoma resection mortality from about 50% in the pioneer period to near 0% nowadays. Cardiomyopathy is usually reversible if managed properly. Stress related or (inverted) Tako Tsubo cardiomyopathy is a recent finding, deserving our attention. Preoperative alpha blockade should be performed to achieve cardiovascular stability and decrease uncontrolled intraoperative surges in blood pressure. During anaesthesia, additional antihypertensive (also mainly alpha blocking) agents are essential to prevent and overcome hypertensive crises. Magnesium sulphate is a safe and promising agent in improving cardiovascular stability and should have a place in standard therapy. A careful selection of anaesthetic drugs and techniques that cause the least hypertension is most important. Preoperative and intraoperative beta-blockade can only be used as adjuvant therapy, mainly to control tachycardia and other rhythm disturbances. Postoperatively, the patient is transferred to the intensive care unit where adequate management of haemodynamic and metabolic complications takes place.

Relation of arterial stiffness to diastolic dysfunction in hypertensive heart disease

OBJECTIVES

To examine the relation of arterial compliance to diastolic dysfunction in hypertensive patients with suspected diastolic heart failure (HF).

PATIENTS

70 medically treated hypertensive patients with exertional dyspnoea (40 women, mean (SD) age 58 (8) years) and 15 normotensive controls.

MAIN OUTCOME MEASURES

Mitral annular early diastolic velocity with tissue Doppler imaging and flow propagation velocity were used as linear measures of diastolic function. Arterial compliance was determined by the pulse pressure method.

RESULTS

According to conventional Doppler echocardiography of transmitral and pulmonary venous flow, diastolic function was classified as normal in 33 patients and abnormal in 37 patients. Of those with diastolic dysfunction, 28 had mild (impaired relaxation) and nine had advanced (pseudonormal filling) dysfunction. Arterial compliance was highest in controls (mean (SD) 1.32 (0.58) ml/mm Hg) and became progressively lower in patients with hypertension and normal function (1.04 (0.37) ml/mm Hg), impaired relaxation (0.89 (0.42) ml/mm Hg), and pseudonormal filling (0.80 (0.45) ml/mm Hg, p = 0.011). In patients with diastolic dysfunction, arterial compliance was inversely related to age (p = 0.02), blood pressure (p < 0.001), and estimated filling pressures (p < 0.01) and directly related to diastolic function (p < 0.01). After adjustment for age, sex, body size, blood pressure, and ventricular hypertrophy, arterial compliance was independently predictive of diastolic dysfunction.

CONCLUSIONS

In hypertensive patients with exertional dyspnoea, progressively abnormal diastolic function is associated with reduced arterial compliance. Arterial compliance is an independent predictor of diastolic dysfunction in patients with hypertensive heart disease and should be considered a potential target for intervention in diastolic HF.

Late incomplete lesion coverage following Cypher stent deployment for diffuse right coronary artery stenosis

The availability of the only drug eluting stent currently approved in the USA has been limited, so that operators often resort to the deployment of multiple undersized stents and post-stenting high pressure inflations with larger balloons to achieve optimal lesion coverage and stent expansion. A case of stent fracture following percutaneous coronary intervention in which this strategy was used is reported.

In vitro study of FFR, QCA, and IVUS for the assessment of optimal stent deployment

We tested whether fractional flow reserve (FFR) discriminates between suboptimally and optimally deployed stents. Latex tubes (diameter solidus in circle = 4 mm) with diameter stenosis 40% (n = 3), 50% (n = 3) and 60% (n = 3) were tested in a pulsatile flow system, using water. Measurements were done at baseline (n = 9; FFR/QCA) and after suboptimal (SOD; 3-mm balloon at 8 atm) and optimal (OD; 4 mm balloon at 16 atm) deployment of a 35-mm stent (n = 6; FFR/QCA/IVUS). Varying Q from 150 to 50 ml/min increased FFR by 2-7%. Conversely, at 100 ml/min, FFR increased by only 0.8% from SOD to OD (P < 0.05). Extrapolating data to blood flow, the gain in FFR from SOD to OD is less than 5% for Q = 100 ml/min, while FFR may increase by 15-20% by changes in blood flow from 50 to 150 ml/min. We conclude that IVUS and QCA are more appropriate for the assessment of optimal stent deployment.

Peripheral "oscillatory" compliance is associated with aortic augmentation index

The augmentation index (AIx) and "oscillatory" compliance (C(2)) are wave contour analysis parameters for the central aorta (P(ao)) and radial artery pressure wave (P(rad)), respectively. Both are sensitive to cardiovascular risk factors such as aging, hypertension, and diabetes and have been proposed as prognostic markers for cardiovascular disease. In this work, we studied the relation between both. We first calculated P(rad) corresponding to a typical aortic A-type (AIx >0.15) and C-type wave (AIx <0), taken from the literature, by using a generalized aorta-radial pressure transfer function. P(rad) corresponding to C-type waves yielded the highest C(2) value. We further used simultaneously measured aortic and radial artery pressure in 45 human subjects age 34 to 84 years (63+/-12 [SD]) at baseline and after administration of nitroglycerin to calculate AIx(meas) and C(2), respectively. Transfer function was used to calculate reconstructed aortic pressure and AIx(rec). AIx(rec) underestimates AIx(meas) by 0.03+/-0.16, but both values correlate well (r=0.64; P<0.001). C(2) and AIx were inversely correlated (r=-0.36; P<0.001 for AIx(meas); r=-0.30; P<0.01 for AIx(rec)). Both AIx(meas) (0.06+/-0.17 versus 0.20+/-0.21; P<0.01) and AIx(rec) (0.04+/-0.12 versus 0.16+/-0.16; P<0.001) were lower after nitroglycerin, whereas C(2) increased only nonsignificantly (0.080+/-0.036 versus 0.071+/-0.042). C(2) is related to AIx and reflects, at least in part, hemodynamic changes affecting central aortic pressure. Nevertheless, given the model assumptions and computational steps associated with calculating C(2), AIx could be a more appropriate parameter to use in the clinical setting because it is determined directly from the pressure wave contour.

Early induction of apoptosis in B-chronic lymphocytic leukaemia cells by hydroxychloroquine: activation of caspase-3 and no protection by survival factors

We have investigated the effect of hydroxychloroquine (HCQ), an anti-rheumatic drug, on malignant B cells from 20 patients with B-chronic lymphocytic leukaemia (B-CLL). HCQ induced a decrease in cell viability in a dose- and time-dependent manner. The mean IC50 was 32 +/- 7 microg/ml (range, 10-75 microg/ml) for 24 h of exposure. This cytotoxic effect was owing to apoptosis, as demonstrated by morphological changes, annexin V binding capacity and DNA fragmentation (28 +/- 4% of apoptotic cells as early as 5 h post incubation, increasing to 82 +/- 4% at 18 h post treatment). The apoptosis was associated with caspase-3 activation because the cleavage and activity of caspase-3 were increased by HCQ. The amount of bcl-2 protein was reduced during apoptosis, evidenced using quantitative flow cytometry. As early as 1 h post-HCQ treatment, a reduction of the mitochondrial transmembrane potential was measured by 3,3'-dihexyloxacarbocyanine iodide. Interestingly, the HCQ effect was not affected by exposure to interleukin-4 or co-culture with bone marrow stromal cells. Our observations suggest that HCQ may offer a new therapeutic tool in the treatment of B-CLL patients.

Randomized comparison of primary stenting and provisional balloon angioplasty guided by flow velocity measurement. Doppler Endpoints Balloon Angioplasty Trial Europe (DEBATE) II Study Group

BACKGROUND

Coronary stenting improves outcomes compared with balloon angioplasty, but it is costly and may have other disadvantages. Limiting stent use to patients with a suboptimal result after angioplasty (provisional angioplasty) may be as effective and less expensive.

METHODS AND RESULTS

To analyze the cost-effectiveness of provisional angioplasty, patients scheduled for single-vessel angioplasty were first randomized to receive primary stenting (97 patients) or balloon angioplasty guided by Doppler flow velocity and angiography (523 patients). Patients in the latter group were further randomized after optimization to either additional stenting or termination of the procedure to further investigate what is "optimal." An optimal result was defined as a flow reserve >2.5 and a diameter stenosis <36%. Bailout stenting was needed in 129 patients (25%) who were randomized to balloon angioplasty, and an optimal result was obtained in 184 of the 523 patients (35%). There was no significant difference in event-free survival at 1 year between primary stenting (86.6%) and provisional angioplasty (85.6%). Costs after 1 year were significantly higher for provisional angioplasty (EUR 6573 versus EUR 5885; P:=0.014). Results after the second randomization showed that stenting was also more effective after optimal balloon angioplasty (1-year event free survival, 93.5% versus 84.1%; P:=0. 066).

CONCLUSIONS

After 1 year of follow-up, provisional angioplasty was more expensive and without clinical benefit. The beneficial value of stenting is not limited to patients with a suboptimal result after balloon angioplasty.

Individualizing the aorto-radial pressure transfer function: feasibility of a model-based approach

We fitted a three-segment transmission line model for the radial-carotid/aorta pressure transfer function (TFF) in 31 controls and 30 patients with coronary artery disease using noninvasively measured (tonometry) radial and carotid artery pressures (P(car)). Except for the distal reflection coefficient (0.85 +/- 0.21 in patients vs. 0.71 +/- 0.25 in controls; P < 0.05), model parameters were not different between patients or controls. Parameters were not related to blood pressure, age, or heart rate. We further assessed a point-to-point averaged TFF (TFF(avg)) as well as upper (TFF(max)) and lower (TFF(min)) enveloping TFF. Pulse pressure (PP) and augmentation index (AIx) were derived on original and reconstructed P(car) (P(car,r)). TFF(avg) yielded closest morphological agreement between P(car) and P(car,r) (root mean square = 4.3 +/- 2.3 mmHg), and TTF(avg) best predicted PP (41.5 +/- 11.8 vs. 41.1 +/- 10.0 mmHg measured) and AIx (-0.02 +/- 0.19 vs. 0.01 +/- 0.19). PP and AIx, calculated from P(car) or P(car,r), were higher in patients than in controls, irrespectively of the TFF used. We conclude that 1) averaged TFF yield significant discrepancies between reconstructed and measured pressure waveforms and subsequent derived AIx; and 2) different TFFs seem to preserve the information in the pressure wave that discriminates between controls and patients.

Stroke volume changes during dobutamine-atropine stress echocardiography: the influence of heart rate and ischaemia

BACKGROUND

A decrease in stroke volume during dobutamine-atropine stress echocardiography heralds ischaemia and possible hypotension. Hypotension results from worsening of LV-function (as a result of ischaemia) left ventricular outflow tract obstruction or hypovolemia, while an increase of stroke volume indicates the preservation of myocardial contractile reserve.

OBJECTIVE

To assess stroke volume changes during dobutamine stress echocardiography in relation to heart rate and occurrence of ischaemia and to validate a new automated cardiac output measurement device.

METHODS

In fifty patients, the stroke volume was assessed using the echocardiographic biplane discs method during a stress echocardiography. These data were reference values for the validation of a new automated cardiac output measurement using the first method as a reference.

RESULTS

Stroke volume measured by the biplane discs method and automated cardiac output device decreased from rest to peak stress, respectively, from 54+/-16 to 34+/-9 (63%) ml and 63+/-17 to 38+/-15 (60%) ml (p < 0.001). Stroke volume decreased with increased heart rate and stress-induced ischaemia when assessed by the biplane discs method, but with the automated device it decreased only with increased heart rate.

CONCLUSIONS

Both increased heart rate and myocardial ischaemia during dobutamine stress echocardiography cause a reduction of stroke volume. However, the automated device did not detect the effects of stress-induced ischaemia on stroke volume. It appears that the biplane discs method is more sensitive for evaluating the effect of ischaemia.

Pulse pressure method and the area method for the estimation of total arterial compliance in dogs: sensitivity to wave reflection intensity

We estimated total arterial compliance (C) in eight anesthetized mongrel dogs with (i) the area method (AM), (ii) the pulse pressure method (PPM), and (iii) the stroke volume-to-pulse pressure ratio (SV/PP). Average compliance was C(AM)=1.1+/-0.73 ml mm Hg(-1) using AM; C(PPM)=0.60+/-0.31 ml mm Hg(-1) using PPM and C(SV/PP)=0.87+/-0.49 ml mm Hg(-1) using SV/PP. Mean aortic pressure was 64+/-23 mm Hg. The overall agreement between C(AM) and C(PPM) was relatively poor (C(AM)=0.15+/-1.61 C(PPM); r2=0.48), with a consistent overestimation of the area method with respect to the pulse pressure method. There was a significant correlation (r=-0.78) between the relative difference between PPM and AM, and the modulus of the first harmonic of the wave reflection coefficient [gamma] which was low in our dog population (0.37+/-0.18). SV/PP overestimated PPM, but both methods were highly correlated (C(SV/PP)=0.06+/-1.60C(PPM); r2=0.97). C(SV/PP) and C(AM) were similar only for [gamma]>0.4. The effect of isolated changes of [gamma] on PPM, AM, and SV/PP was studied using the linear wave separation technique. The area method appeared very sensitive to the wave reflection intensity. For low reflection coefficients, the diastolic wave profile was flattened and compliance was overestimated. PPM and SV/PP were relatively independent of [gamma] and remained even applicable for [gamma]=0. We believe that the pulse pressure method is the most consistent method for the estimation of total arterial compliance in hemodynamic conditions characterized by a low wave reflection intensity.

Effect of catheter placement on 3-D velocity profiles in curved tubes resembling the human coronary system

Novel measurement techniques based on intravenous ultrasound (IVUS) technology ('IVUS-Flowmetry') require the location of a catheter inside the coronary bed. The present study quantifies disturbances in the 3-D velocity profile induced by catheter placement inside a tube, applying computational fluid dynamics. Two curved, circular meshes (radius K = 0.025 m and K = 0.035 m) with and without a catheter inside the lumen were applied. The catheter was located at the inner curve, the outer curve and at the top position. Boundary conditions were: no slip on the wall, zero stress at the outlet, uniform inflow with entrance velocities of 0.1, 0.2 and 0.4 m/s. Curvature-associated centrifugal forces shifted the maximal velocity to the outer curve and introduced two symmetrical vortices. Additional catheter placement redistributed the 3-D axial velocity field away from the catheter, which was accompanied by the appearance of multiple low-strength vortices. In addition, peak axial velocity increased, peak secondary velocities decreased, axial pressure drop increased and shear stress increased. Flow calculations simulated to resemble IVUS-based flowmetry changed by only 1% after considering secondary velocity. In conclusion, placement of a catheter inside a curved tube resembling the human coronary system changes the velocity field and reduces secondary patterns. The present study supports the usefulness of catheter-based flowmetry during resting flow conditions. During hyperemic flow conditions, flow measurements might be accompanied by large axial pressure drops because the catheter, itself, might act as a significant stenosis.

Echo decorrelation estimated from signal powers

Volume flow can be estimated from the decorrelation of radiofrequency (RF) intravascular ultrasound signals. The method is based on a rather time-consuming process that measures the decorrelation slope from a time signal sequence. To improve the speed of flow processing, a more efficient way of estimating the flow velocity from the ratio between the power of the temporal averaged signal and the mean signal power is described in this paper. The relationship between the signal power-ratio index and the decorrelation slope was analyzed and tested using computer-simulated data. Volumetric flow data obtained with the power-ratio method were compared to those derived from the decorrelation slope in five patients. Results of the comparison studies indicate that no significant differences in flow measurements were found between the two methods, but the power-ratio method is able to improve the processing speed significantly.

Quantification of mitral regurgitation by the automated cardiac output method: an in vitro and in vivo study

BACKGROUND

Recently, the automated cardiac output method (ACM) was introduced for the calculation of blood flow at the left ventricular outflow tract (LVOT). This study was performed to examine the possibility of using ACM for flow calculation at the level of the mitral valve and for the quantification of mitral regurgitation (MR) in vitro and in vivo.

METHODS AND RESULTS

In a computer-controlled in vitro model of the human heart, aortic and mitral normal bioprosthetic valves were inserted. ACM and electromagnetic probe flow measurements correlated well at the LVOT and at the mitral level (r2 = 0.79 and 0.77, respectively). For stroke volumes ranging from 30 to 100 ml/beat, there was no statistically significant bias between ACM and electromagnetic flow probe (-1.5 and 1.3 ml for LVOT and mitral level, respectively). Limits of agreement were [-14; +11] ml and [-18; +16] ml, respectively. We evaluated 68 patients in our in vivo study. They were divided into three groups according to the results of "standard" echocardiographic Doppler methods for the semiquantification of MR: echocardiographic color Doppler cartography, intensity of the continuous wave Doppler spectra, and in some patients, pulmonary venous flow, conventional Doppler, and proximal isovelocity surface area quantitative data. Group 1 consisted of 35 patients without MR or a physiologic one; the 17 patients in group 2 had a mild MR (1-2/4) and in group 3, 16 patients with MR 3-4/4 were included. Regurgitant volume (RV) was calculated as the difference between ACM mitral flow and ACM aortic flow, and regurgitant fraction (RF) was defined as the ratio between RV and ACM mitral flow. When mitral flow was measured only from the four-chamber view, we found in group 1, RV = -0.57 (0.67) L/min and RF = -16% (19%); in group 2, RV = -0.31 (1.06) L/min and RF = -8% (19%); and in group 3, RV = 1.53 (0.94) L/min and RF = 23% (13%). RV and RF were statistically higher in group 3 compared with group 2 or group 1 (p < 0.0005), but no significant difference was found between groups 1 and 2. When mitral flow was measured by the mean value of ACM four-chamber and two-chamber views, this resulted in group 1, RV = -0.26 (0.63) L/min and RF = -8% (15%); in group 2, RV = 0.01 (1.04) L/min and RF = -2% (18%); and in group 3, RV = 2.07 (1.21) L/min and RF = 34% (19%). RV and RF were again significantly higher in group 3 (p < 0.0001). There was no significant difference between group 1 and group 2, but in group 1 RF was no longer statistically different from 0%.

CONCLUSIONS

(1) In our in vitro setting, ACM is reliable both at the LVOT and at the mitral valve. (2) In the in vivo situation, some overlapping does exist between the three groups of MR. However, ACM is a very easy, rapid, and objective method to differentiate hemodynamic nonsignificant (<3/4) from significant (> or =3/4) MR. Together with other well-known methods for the quantification of MR, it should facilitate the gradation of MR in the clinical setting. The absence of significant differences between group 1 and group 2 proves that the accuracy of ACM measurements at the mitral valve needs to be ameliorated before ACM can be used as a gold standard for the noninvasive measurement of RV and RF.

Decreased coronary flow reserve in hypertrophic cardiomyopathy is related to remodeling of the coronary microcirculation

BACKGROUND

Ischemia occurs frequently in hypertrophic cardiomyopathy (HCM) without evidence of epicardial stenosis. This study evaluates the hypothesis that the occurrence of ischemia in HCM is related to remodeling of the coronary microcirculation.

METHODS AND RESULTS

End-diastolic septal wall thickness was significantly increased in patients with HCM (25.8+/-2.9 mm) in comparison with cardiac transplant recipients (control subjects: 11.4+/-3.0 mm; P<0.05). Although the diameter of the left anterior descending coronary artery was similar in both groups (3.0+/-0.8 versus 3.0+/-0.5 mm, P=NS), the coronary resistance reserve (CRR=CRRbasal/CRRhyperemic), corrected for extravascular compression (end-diastolic left ventricular pressure), was reduced to 1.5+/-0.6 in HCM (P<.05; control, 2.6+/-0.8). Arteriolar lumen (AL) divided by wall area was lower in HCM (21+/-5% versus 30+/-4%; P<.05), and capillary density tended to decrease (from 1824+/-424 to 1445+/-513 per mm2, P=.11) in HCM. CRR was linearly related to normalized AL according to the formula CRR=O.1 AL-0.45 (r=.57; P<.05). Further analysis revealed that CRR, AL, and capillary density were all linearly related to the degree of hypertrophy.

CONCLUSIONS

Decrements in CRR were related to changes of the coronary microcirculation. Both the decrease in CRR and these changes in the coronary microcirculation were related to the degree of hypertrophy. All these factors might contribute to the well-known occurrence of ischemia in this patient group.

Potentials of volumetric blood-flow measurement

Current intravascular ultrasound techniques produce real-time imaging of a vessel cross-section with a scan plane normal to blood flow. When randomly distributed blood particles travel through this ultrasound imaging plane, the received echo signals decorrelate as a function of time. The speed of such a decorrelation procedure is proportional to the flow velocity. This phenomenon provides a potential to estimate blood velocities by means of decorrelation analysis. In this paper, we present a method for measuring local blood velocity and quantifying volume flow directly from cross-sectional intravascular ultrasound data. This method is based on multiple decorrelation assessments with a sequence of radio frequency echo signals. The velocity measurement is obtained by comparing the measured decorrelation value with the prior knowledge of the beam characteristics of an intravascular ultrasound transducer. Volume flow is derived by integrating the cross-sectional area and its corresponding velocity vector over the vessel lumen. The decorrelation-based method was tested in vitro with a flow phantom. Measurements were also carried out in vivo in pig experiments to determine the usefulness of this method in clinical settings. Preliminary results of these experiments indicate that the proposed decorrelation method is able to extract cross-sectional velocity profiles and volumetric flow both in vitro and in vivo.

Lymph node perforation into the airway in AIDS-associated tuberculosis

A 27 year old African woman infected with the human immunodeficiency virus (HIV) presented with pulmonary complaints. Her sputum smears were positive for acid-fast bacilli (AFB). Chest roentgenogram showed right mediastinal and hilar adenopathy with a right pulmonary infiltrate. At fibreoptic bronchoscopy, mucosal infiltration with perforation and presence of thick caseum was detected in the bronchus intermedius confirming the diagnosis of a perforated lymph node. This case demonstrates that a more liberal indication of bronchoscopy helps in evaluating the impact of enlarged intrathoracic lymph nodes on neighbouring bronchi, leading to earlier detection of endobronchial tuberculosis in patients with the acquired immune deficiency syndrome (AIDS).

Lymph node perforation into the airway in AIDS-associated tuberculosis

A 27 year old African woman infected with the human immunodeficiency virus (HIV) presented with pulmonary complaints. Her sputum smears were positive for acid-fast bacilli (AFB). Chest roentgenogram showed right mediastinal and hilar adenopathy with a right pulmonary infiltrate. At fibreoptic bronchoscopy, mucosal infiltration with perforation and presence of thick caseum was detected in the bronchus intermedius confirming the diagnosis of a perforated lymph node. This case demonstrates that a more liberal indication of bronchoscopy helps in evaluating the impact of enlarged intrathoracic lymph nodes on neighbouring bronchi, leading to earlier detection of endobronchial tuberculosis in patients with the acquired immune deficiency syndrome (AIDS).

Does nitrous oxide affect the hemodynamic effects of anesthesia induction with propofol?

Anesthesia was induced in 20 patients, ASA physical status I and II, with either propofol (2.5 mg.kg-1), vecuronium (100 micrograms.kg-1), and 100% oxygen (Group A), or with equal doses of propofol and vecuronium but with 70% nitrous oxide in oxygen (Group B). All patients were premedicated with lorazepam 2 mg orally. In both groups systolic arterial pressure decreased after 3 minutes (P less than 0.05) due to decreases in cardiac output and stroke volume (P less than 0.05). Systemic vascular resistance in both groups did not change immediately after administration of propofol but increased (P less than 0.05) following intubation. Addition of nitrous oxide did not alter hemodynamic parameters associated with propofol induction.