Activated rate-response is associated with increased mortality risk in cardiac device carriers with acute heart failure

AIMS

This study investigated whether an activated R-mode in patients carrying a cardiac implantable electronic device (CIED) is associated with worse prognosis during and after an episode of acutely decompensated heart failure (AHF).

METHODS

Six hundred and twenty-three patients participating in an ongoing prospective cohort study that phenotypes and follows patients admitted for AHF were studied. We compared CIED carriers with activated R-mode stimulation (CIED-R) to CIED carriers not in R-mode (CIED-0) and patients without CIEDs (no-CIED). The independent impact of R-mode activation on 12-month all-cause death was examined using uni- and multivariable Cox proportional hazards regression taking into account potential confounders, and hazard ratios (HR) with their 95% confidence intervals (CI) were reported.

RESULTS

Mean heart rate on admission was lower in CIED-R (n = 37, 16% women) vs. CIED-0 (n = 64, 23% women) or no-CIED (n = 511, 43% women): 70 bpm vs. 80 bpm or 82 bpm; both p<0.001. In-hospital mortality was similar across groups, but age- and sex-adjusted all-cause 12-month mortality risk was differentially affected by R-mode activation; CIED-R vs. CIED-0: HR 2.44, 95%CI 1.25-4.74; CIED-R vs. no-CIED: HR 2.61, 95%CI 1.59-4.29. These effects persisted after multivariable adjustment for potential confounders. Within CIED-R, mortality risk was similar in patients with pacemakers vs. ICDs and in subgroups with left ventricular ejection fraction (LVEF) <50% vs. ≥50%.

CONCLUSION

In patients admitted with AHF, R-mode stimulation was associated with a significantly increased 12-month mortality risk. Our findings shed new light on "admission heart rate" as a potentially treatable target in AHF. Our data are compatible with the concept that chronotropic incompetence contributes to an adverse outcome in these patients and may not be adequately treated through accelerometer-based R-mode stimulation.

Population data-based federated machine learning improves automated echocardiographic quantification of cardiac structure and function: the Automatisierte Vermessung der Echokardiographie project

Aims

Machine-learning (ML)-based automated measurement of echocardiography images emerges as an option to reduce observer variability. The objective of the study is to improve the accuracy of a pre-existing automated reading tool ('original detector') by federated ML-based re-training.

Methods and results

Automatisierte Vermessung der Echokardiographie was based on the echocardiography images of n = 4965 participants of the population-based Characteristics and Course of Heart Failure Stages A-B and Determinants of Progression Cohort Study. We implemented federated ML: echocardiography images were read by the Academic Core Lab Ultrasound-based Cardiovascular Imaging at the University Hospital Würzburg (UKW). A random algorithm selected 3226 participants for re-training of the original detector. According to data protection rules, the generation of ground truth and ML training cycles took place within the UKW network. Only non-personal training weights were exchanged with the external cooperation partner for the refinement of ML algorithms. Both the original detectors as the re-trained detector were then applied to the echocardiograms of n = 563 participants not used for training. With regard to the human referent, the re-trained detector revealed (i) superior accuracy when contrasted with the original detector's performance as it arrived at significantly smaller mean differences in all but one parameter, and a (ii) smaller absolute difference between measurements when compared with a group of different human observers.

Conclusion

Population data-based ML in a federated ML set-up was feasible. The re-trained detector exhibited a much lower measurement variability than human readers. This gain in accuracy and precision strengthens the confidence in automated echocardiographic readings, which carries large potential for applications in various settings.

Mortality risk is increased in chronotropic incompetent device carriers with acute heart failure

Introduction

In heart failure (HF), chronotropic incompetence is a major factor limiting cardiac output and exercise capacity. In patients carrying cardiac implantable electronic devices (CIED), accelerometer-based rate adaption (R-mode) counterbalances chronotropic incompetence during physical activity but fails to modulate heart rate under circumstances of high metabolic demand.

Purpose

We hypothesized that an activated R-mode, a surrogate of chronotropic incompetence, indicates worse prognosis during and after episodes of acutely decompensated HF (AHF).

Methods

We analysed 632 patients enrolled between 01/2014 and 02/2018 in an ongoing registry that phenotypes and follows patients admitted for AHF. We compared CIED carriers with activated R-mode (CIED-R; n=37, 16% women) with CIED carriers not in R-mode (CIED-0; n=64, 23% women) and patients without CIEDs (no-CIED; n=511, 43% women). Information on survival status was collected up to 12 months after discharge from index hospitalisation (IH). Uni- and multivariable Cox proportional hazard regression was used to identify predictors of 12-month mortality risk.

Results

Mean age of the study sample was 74 (11) years, 39% were women, median LVEF on admission was 51 (quartiles 32, 59) % and de novo HF was detected in 20% of all patients. Median length of IH was 10 (7, 14) days. In-hospital mortality was similar across groups, but 12-month mortality risk was affected by chronotropic incompetence as indicated by R-mode activation: age- and sex-associated hazard ratio (HR) for CIED-R was 2.61 (95% CI 1.59–4.29, p&lt;0.001) compared to group no-CIED, and 2.44 (95% CI 1.25–4.74, p=0.009) compared to group CIED-0. Amongst univariable predictors of mortality risk, strong associations were found for NT-proBNP levels (p&lt;0.001), Charlson comorbidity index (p=0.001), and de novo HF (p=0.003). These effects persisted after multivariable adjustment for comorbidity burden. Within CIED-R, mortality risk was similar in patients with pacemakers vs. ICDs (HR 1.20, 95% CI 0.49–2.95) and in subgroups with LVEF &lt;50% vs. ≥50% (HR 1.10, 95% CI 0.79–1.53). Mean heart rate on admission was lower in CIED-R vs. CIED-0 or no-CIED (70 bpm vs. 80 bpm or 82 bpm; both p&lt;0.001). Heart rate on admission had no impact on frequency of in-hospital worsenings or death. However, we found a 36% increase in mortality risk per tertile of heart rate at discharge (HR 1.36, 95% CI 1.10–1.69, p=0.004) after exclusion of patients with an activated R-mode.

Conclusion

In AHF, R-mode stimulation was associated with an increased 12-month mortality risk, independent of LVEF, type of CIED, burden of comorbidities and type of presentation. Further, increased resting heart rate at discharge predicted 12-month mortality risk only in patients without an activated R-mode. Our findings suggest that chronotropic incompetence per se worsens outcome in AHF and may not be adequately treated through accelerometer-based R-mode stimulation.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Comprehensive Heart Failure Centre (CHFC) Würzburg is funded by the Federal Ministry of Education and Research, Integrated Research and Treatment Centre “Prevention of Heart Failure and its Complications”.

Sex-specific bimodal clustering of left ventricular ejection fraction in patients with acute heart failure

Aims

There is an ongoing discussion whether the categorization of patients with heart failure according to left ventricular ejection fraction (LVEF) is scientifically justified and clinically relevant. Major efforts are directed towards the identification of appropriate cut‐off values to correctly allocate heart failure‐specific pharmacotherapy. Alternatively, an LVEF continuum without definite subgroups is discussed. This study aimed to evaluate the natural distribution of LVEF in patients presenting with acutely decompensated heart failure and to identify potential subgroups of LVEF in male and female patients.

Methods and results

We identified 470 patients (mean age 75 ± 11 years, n = 137 female) hospitalized for acute heart failure in whom LVEF could be quantified by Simpson's method in an in‐hospital echocardiogram. Non‐parametric modelling revealed a bimodal shape of the LVEF distribution. Parametric modelling identified two clusters suggesting two LVEF peaks with mean (variance) of 61% (9%) and 31% (10%), respectively. Sub‐differentiation by sex revealed a sex‐specific bimodal clustering of LVEF. The respective threshold differentiating between ‘high’ and ‘low’ LVEF was 45% in men and 52% in women.

Conclusions

In patients presenting with acute heart failure, LVEF clustered in two subgroups and exhibited profound sex‐specific distributional differences. These findings might enrich the scientific process to identify distinct subgroups of heart failure patients, which might each benefit from respectively tailored (pharmaco)therapies.

Dynamics of Left Ventricular Myocardial Work in Patients Hospitalized for Acute Heart Failure

BACKGROUND

The left ventricular ejection fraction (LVEF) is the most commonly used measure describing pumping efficiency, but it is heavily dependent on loading conditions and therefore not well-suited to study pathophysiologic changes. The novel concept of echocardiography-derived myocardial work (MyW) overcomes this disadvantage as it is based on LV pressure-strain loops. We tracked the in-hospital changes of indices of MyW in patients admitted for acute heart failure (AHF) in relation to their recompensation status and explored the prognostic utility of MyW indices METHODS AND RESULTS: We studied 126 patients admitted for AHF (mean 73 ± 12 years, 37% female, 40% with a reduced LVEF [<40%]), providing pairs of echocardiograms obtained both on hospital admission and prior to discharge. The following MyW indices were derived: global constructive and wasted work (GCW, GWW), global work index (GWI), and global work efficiency. In patients with HF with reduced ejection fraction with decreasing N-terminal prohormone B-natriuretic peptide levels during hospitalization, the GCW and GWI improved significantly, whereas the GWW remained unchanged. In patients with HF with preserved ejection fraction, the GCW and GWI were unchanged; however, in patients with no decrease or eventual increase in N-terminal prohormone B-natriuretic peptide, we observed an increase in GWW. In all patients with AHF, higher values of GWW were associated with a higher risk of death or rehospitalization within 6 months after discharge (per 10-point increment hazard ratio 1.035, 95% confidence interval 1.005-1.065).

CONCLUSIONS

Our results suggest differential myocardial responses to decompensation and recompensation, depending on the HF phenotype in patients presenting with AHF. The GWW predicted the 6-month prognosis in these patients, regardless of LVEF. Future studies in larger cohorts need to confirm our results and identify determinants of short-term and longer term changes in MyW.

Global wasted myocardial is unrelated to conventional markers of systolic and diastolic function in patients with acute heart failure

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The AHF Register is supported by an unrestricted grant of Behringer Ingelheim, and grants of the German Ministry of Research and Education within the Comprehensive Heart Failure Center, Würzburg (BMBF 01E01004 and 01E01504)

onbehalf

AHF Registry

Background & Aim Myocardial Work (MyW) analysis quantifies myocardial performance using non-invasively derived pressure-strain loops. It is considered less load-dependent than left ventricular ejection fraction (LVEF) and longitudinal strain, since it integrates blood pressure into the assessment. We assessed associations between MyW indices, natriuretic peptide (NT-proBNP), and conventional markers of systolic and diastolic cardiac function mirroring the hemodynamic changes occurring during hospitalization, in patients hospitalized for acute heart failure (AHF).

Methods Consecutive patients (≥18 years) hospitalized for AHF with serial high-quality pairs of echocardiograms (i.e., early after hospitalization and prior to discharge) were eligible. Exclusion criteria were high output AHF, cardiogenic shock, and being listed for high urgency transplantation. The following MyW measures [definition in brackets] were analyzed from the stored recordings: Global constructive work (GCW) [sum of positive work performed during systolic shortening plus negative work during lengthening in isovolumetric relaxation (IVR)], global wasted work (GWW) [sum of negative work performed during systolic lengthening plus work performed during shortening in IVR], global work efficiency (GWE) [constructive work/(constructive work + wasted work)]; global work index (GWI) [total work performed from mitral valve closure to mitral valve opening]. Associations were determined using scatter plots and Pearson Product-Moment correlation coefficients.

Results N = 126 patients (73 ± 12 years, 37% female) were eligible. GWI and GCW proved significantly correlated with surrogates measured both on admission and at discharge, NT-proBNP, LVEF, and e’ (Table). By contrast, GWW did not correlate with any of these variables. GWE was also correlated with NT-proBNP (and e’ at discharge), but at both time points respective correlations were more pronounced.

Conclusion In patients hospitalized for AHF, GWI, GCW and GWE were associated with conventional parameters of myocardial stress and LV dysfunction. In contrast, GWW was unrelated with any of these established markers. Future studies in larger cohorts and with longer-term follow-up need to clarify to what extent might GWW carry complementary clinical and prognostic significance.

Abstract Figure.

P803 Myocardial work in acutely decompensated heart failure patients differs between HFrEF and HFpEF

OnBehalf

AHF Registry

Background & Aim A novel echocardiographic method to non-invasively determine left ventricular (LV) myocardial work (MyW) based on speckle-tracking derived longitudinal strain and blood pressure has recently been validated against invasive reference measurements. MyW is considered less load-dependent than LV ejection fraction (EF) and LV longitudinal strain. We investigated MyW indices in patients with reduced ejection fraction (LVEF &lt;40%; HFrEF) and patients with preserved ejection fraction (LVEF ≥50%, HFpEF) admitted for acutely decompensated heart failure (AHF).

Methods The AHF registry is a monocentric prospective follow-up study that comprehensively phenotypes consecutive patients hospitalized for AHF. Echocardiography was performed on the day of admission. MyW assessment was performed off-line using EchoPAC (GE, version 202). Here we present MyW indices and performed two-sided t-tests to analyze differences in numerical baseline covariates.

Results We analyzed the echocardiograms of 94 AHF patients (72 ± 10 years; 36% female). 46 patients (49%) had an LVEF &lt;40%, while 48 patients (51%) presented with LVEF ≥50%. HFrEF patients were younger, less often female, and hat lower blood pressure (table). Consistent with lower LVEF, HFrEF patients had less negative global longitudinal strain and lower global constructive work, when compared to HFpEF patients. Since HFrEF patients also had higher global wasted work, this yielded a lower myocardial work efficiency compared to HFpEF patients (table).

Conclusions This analysis in patients with AHF exhibited marked differences in MyW indices according to subgroups with HFrEF and HFpEF, thus adding information to the classical measures of LV function. Future research has to determine whether constructive and/or wasted MyW are valuable diagnostic or therapeutic targets in patients with AHF.

Abstract P803 Figure.

Chromosomal imbalances, 11q21 rearrangement and MECT1-MAML2 fusion transcript in mucoepidermoid carcinomas of the salivary gland

The aim of this study was to determine genetic alterations in mucoepidermoid carcinomas of the salivary gland in association with clinical and histopathological parameters. Nineteen formalin-fixed, paraffin-embedded tumors were analysed by using comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH) on interphase nuclei and reverse transcriptase-polymerase chain reaction (RT-PCR) for detection of MECT1-MAML2 fusion transcript. The CGH analysis showed an overrepresentation of chromosome X and losses of entire chromosomes or regions on chromosome 1, 2, and 15 as the most frequent copy number changes. In 37% of the analysed tumors a MAML2-rearrangement by interphase FISH was detected, whereas 58% of the samples showed expression of MECT1-MAML2 fusion transcript. We conclude that the presence of MAML2-rearrangement as well as of MECT1-MAML2 fusion transcript may reflect a more favourable prognosis and may be a useful marker for clinical prediction of the biological behavior of these tumors as previously reported.

Outcome prediction in critical care: physicians' prognoses vs. scoring systems

BACKGROUND AND OBJECTIVE

To compare the accuracy of prognoses made by intensive care physicians with the performance of two indicators, the original Simplified Acute Physiology Score (SAPS) II and a modified version optimized to the patient sample.

METHODS

Data from 412 patients consecutively admitted to intensive care units of Göttingen University Hospital, Germany, were collected according to the original score criteria. Information necessary for the computation of SAPS II and the vital status on hospital discharge was recorded. To customize the original SAPS II in our cohort, the database was randomly divided into two subgroups. Logistic regression analysis with physiological values as explanatory variables was used. A bootstrap procedure completed the process. Furthermore, physicians were asked to indicate their prognostic judgement concerning the patients' hospital mortality.

RESULTS

Discrimination analysis showed the following areas under receiver operating characteristic curves: physicians' prognoses 0.84 (confidence interval (CI): 0.79-89), SAPS II 0.75 (CI: 0.69-0.80) and customized SAPS 0.72 (CI: 0.66-0.78). The physician's forecast was significantly better, while the customized and the original SAPS were not substantially different as regards their accuracy.

CONCLUSIONS

Prognoses made by physicians are superior to objective models. This may result from more extensive knowledge and other kinds of information available to clinicians. A clinician's action also depends on his/her prognosis at the beginning of the treatment, giving raise to a possible correlation between medical outcome and the clinician's prognosis. Our findings indicate that physicians do not limit their prognosis to the objective factors at their disposal, but indicate that they base their decisions on experience and individual observations.

Chronic effects of vapour phase di-n-butyl phthalate (DBP) on six plant species

A fumigation experiment was performed in which six plant species representing the European flora were exposed to a range of DBP concentrations. Controlled amounts of DBP-saturated air were injected into the ingoing air-streams of plant fumigation chambers, maintaining constant concentrations there for a period of up to 76 days. The target concentrations were a control, 0.8, 1.5, 3.5, and 10.0 microg m(-3). The variation in sensitivity between plant species to atmospheric DBP was quantified on the basis of whole plant biomass in order to derive no-observed-effect-concentrations (NOECs). Significant dose-response relationships, based on realised concentrations, were thus derived using non-linear regression, resulting in NOECs of 0.51 microg m(-3) for Trifolium repens, 0.96 microg m(-3) for Brassica campestris, 1.87 microg m(-3) for Phaseolus vulgaris and 2.21 microg m(-3) for Plantago major. A significant effect was also observed for Holcus lanatus at 12.4 microg m(-3) DBP, but due to the variation at lower levels of DBP exposure, no dose-response relationship could be derived. No significant effect on growth of current year needles in Picea abies was observed, even at the highest level of DBP, 13.7 microg m(-3). Based on statistical extrapolation according to Aldenberg and Slob [Ecotox. Environ. Safety, 25 (1993) 48], an overall predicted no-effect concentration (PNEC) for the plant-atmosphere compartment of 0.33 microg m(-3) DBP was calculated. The PNEC was calculated using the mean and standard deviation of the NOEC for four of the tested species and an extrapolation factor. In addition to changes in leaf colour, leaf crinkling and growth reduction, a number of not quantified observations are described, indicating that DBP affects the physiology as well as the morphology of these species.

[Evaluation of the public health service law of the Saxony-Anhalt region--community affairs, transfer of power and loss of control]

AIM

In the state of Saxony-Anhalt, a new Public Health Service law came into force in 1998. Our study investigated whether this new legislation has led to an extension of duties performed by regional health departments and to a subsequent increase in expenditure.

METHODS

Guided interviews at all administrative levels of the public health system were conducted. The catalogue of duties was systematized and a questionnaire was developed and distributed to all regional health departments (response rate: 17 out of 24). Data concerning revenues and expenditures of the regional health departments were analysed on the basis of the administrative districts' budget data.

RESULTS

Regional health departments stated that there had been practically no change in their activities over the last few years. When questioned about the coverage of 58 specific duties, a considerable disparity was evident between departments. A core group of "classical" duties comprising environmental health and hygiene, child health protection, individual health appraisal, and public health supervision are carried out on an established basis. Some duties were handled by external institutions, others, mostly community health duties, were not performed on an extensive scale. When asked about the desired model for their health department, most departments preferred the model of being an executor of sovereign duties, however a corporate model was deemed to be almost as acceptable. The following fields will gain increasing significance in the future: environmental medicine, health reporting, preventive medicine, co-ordination of regional health care, and health promotion. Since 1995, staff has been reduced in all regional health departments (-10.4%; 1999: 2.92 employees per 10,000 inhabitants). In 1999, expenditures amounted to an average of 24.64 German Marks per capita (range 14.20-44.58 DM). The number of inhabitants and the revenue of the regional districts were determinants of their health budgets.

CONCLUSION

Our results showed that no uncompensated additional expenditure by regional authorities resulted from this law. So far, most districts have not perceived regional health as a community affair offering possible competitive advantages. The federal state lost considerable influence at the regional level. Recommended are regional health priorities, conjoint staff development, and state guidance by a head agency providing leadership and support, while leaving responsibility with the districts.

Effect of long-term dietary protein intake on glucose metabolism in humans

AIMS/HYPOTHESIS

A meal rich in protein stimulates insulin secretion. Long-term effects of dietary protein on insulin release and glucose metabolism are, however, still not known. Our study focussed on the effect of different protein intake on pancreatic insulin secretion capacity, glycogen turnover and gluconeogenesis.

METHODS

Subjects with constant (6 months) dietary protein of 1.87 +/- 0.26 g kg(-1) day(-1) (1.25-2.41) named high protein group and with 0.74 +/- 0.08 (0.57-0.80), normal protein group, were identified by a food questionnaire and were matched (n = 9) according to sex, age and calorie intake. They underwent an intravenous glucose tolerance test and a euglycaemic hyperinsulinaemic clamp with infusion of [6,6-2H2]-glucose combined with indirect calorimetry. To estimate net gluconeogenesis the usual diet was enriched by deuterated water or U-[13C6]-glucose and breath and plasma were sampled.

RESULTS

Glucose-stimulated insulin secretion was increased in the high protein group (516 +/- 45 pmol/l vs 305 +/- 32, p = 0.012) due to reduced glucose threshold of the endocrine beta cells (4.2 +/- 0.5 mmol/l vs 4.9 +/- 0.3, p = 0.031). Endogeneous glucose output was increased by 12% (p = 0.009) at 40 pmol/l plasma insulin in the high protein group, but not at higher insulin concentration whereas overall glucose disposal was reduced. Fasting plasma glucagon was 34% increased in the high protein group (p = 0.038). Fractional gluconeogenesis was increased by 40% in subjects receiving a high protein diet as determined by both methods.

CONCLUSION/INTERPRETATION

High protein diet is accompanied by increased stimulation of glucagon and insulin within the endocrine pancreas, high glycogen turnover and stimulation of gluconeogenesis.

Use of administrative personnel in hospitals: a three nation comparison

Differences in the costs of health care systems among industrialized countries has been the focus of several studies. Labor costs, specifically the amount of resources used for administration, are considered to contribute to differences in overall health care costs. To determine differences in the use of labor resources, especially administrative and managerial, among American, Austrian and German hospitals, we use a convenience sample of one Austrian, one German and two United States (US) tertiary care centers. In our analysis we used payroll data of the four hospitals. First, we categorized job titles and created job categories. Subsequently, we calculated full time equivalents (FTEs) per job category and compared them across countries. Adjustments were made for differences in health systems. The main outcome measures were FTEs per patient day and per discharge in each job category. In the US hospitals > 19% of FTEs were in administrative categories as compared with < 8% in the European hospitals. For administrative managers, US hospitals used > 11 times the labor per patient day of the European institutions. Among administrative areas, the largest absolute FTE difference was in financial operations. US hospitals used > 5 FTEs of personnel per 10,000 patient days versus < 1.0 FTE in the European hospitals. Given the kinds of administrative work done in US hospitals compared to Austria and Germany, differences in the organization and financing of these countries' health care systems may account for an important part of the higher number of US personnel.

Plasma concentrations of ketanserin in chronic hemodialysed patients

Six patients on chronic hemodialysis received 20 mg ketanserin p.o. twice daily for 3 days. Plasma levels were measured daily 2 hours after application of the morning dose; however, on the third day, plasma levels were taken before, during and after dialysis. On the 4th day elimination was measured after a single dose of 20 mg ketanserin for 24 hours. Mean plasma levels ranged from 19 to 31 ng/ml. Both ketanserin and reduced ketanserin were not eliminated by dialysis. Elimination half-life was about 12 hours.

[Miconazole-benzoyl peroxide: a new combination for extending the topical therapy of acne]

In a randomized double blind study on acne the efficacy and tolerance of a combination preparation of benzoyl peroxide and miconazole as a cream formulation was compared with those of benzoyl peroxide and oral tetracyclin. For this study, we selected patients mainly suffering from papulopustular acne of medium to high degree of severity. Efficacy and tolerance were satisfactory in both groups, and there was no statistically significant difference.

Reaction of glutathione with conjugated carbonyls

1. GSH reacts with conjugated carbonyls according to the equation: GSH+R-CH=CH-COR in equilibrium R-CH(SG)-CH2-COR. The forward reaction follows second order, the reverse reaction first order kinetics. It is assumed that this reaction reflects best the ability of conjugated carbonyls to inactivate SH groups in biological systems. 2. The rate of forward reaction increases with pH approx. parallel with alphaSH. Besides OH- ions also proton donors (e.g. buffers) increase the rate. The catalytic effect of pH and buffer is interpreted in view of the reaction mechanism. 3. The equilibrium constants as well as the rate constants for forward (k1) and reverse reaction show an extreme variation depending on the carbonyl structure. Acrolein and methyl vinyl ketone (k1 = 120 and 32 mol-1 sec-1, resp.) react more rapidly than any other carbonyl to give very stable adducts (half-lives for reverse reaction 4.6 and 60.7 days, resp). Somewhat less reactive are 4-hydroxy-2-alkenals and 4-ketopentenoic acid (k1 between 1 and 3 mol-1 sec-1), but they also form very stable adducts showing half-lives between 3.4 and 19 days. All other carbonyl studied react either very slowly (e.g. citral, ethly crotonate, mesityl oxide, acrylic acid) or form very labile adducts (crotonal, pentenal, hexenal, 3-methyl-butenone). Comparing biological activities of conjugated carbonyls their reactivity towards HS (k1) and the stability of the adducts must be considered.