Fibrillatory wave amplitude and thromboembolic risk in non-anticoagulated patients with atrial fibrillation

BACKGROUND

The benefit of oral anticoagulation in atrial fibrillation (AF) is well established for patients at elevated stroke risk, but less clear for those at intermediate risk. We investigated whether analysis of electrocardiogram (ECG) derived fibrillatory waves (F-waves) could help identify patients at risk for stroke and systemic embolism (SSE).

METHODS

The Finnish Cardioversion (FinCV) study included patients not on permanent anticoagulation therapy who underwent cardioversion for an acute AF episode. We identified 739 individuals with a valid ECG and complete follow-up data. The maximum amplitudes of the F-waves in leads II and V1 were manually measured from the pre-procedure ECG. Patients were categorized into fine and coarse F-wave groups. The optimal lead and amplitude threshold for grouping were found in an events per person-years analysis. SSE were identified from the patient medical records until either anticoagulation was prescribed, AF was deemed chronic, the patient had deceased, or the end of follow-up.

RESULTS

Overall 37 (5.0%) patients suffered SSE during the median follow-up time of 5.4 years (1.9-10.8). Measured from lead V1 the SSE rates per 100 person-years were 1.5 and 0.7 in fine and coarse F-wave groups, respectively. Fine F-waves were observed in 112 (15.2%). Baseline characteristics were similar between the groups. Fine F-wave predicted SSE in a competing risk analysis (SHR 2.34, 95%CI 1.12-4.87, p = .023). Analyses from lead II did not provide significant results.

CONCLUSION

Electrocardiographic F-wave amplitude may provide additional information on stroke risk in patients with paroxysmal AF and borderline indications or contraindications for anticoagulation.

Mechanocardiography detects improvement of systolic function caused by resynchronization pacing

Objective.Cardiac resynchronization therapy (CRT) is commonly used to manage heart failure with dyssynchronous ventricular contraction. CRT pacing resynchronizes the ventricular contraction, while AAI (single-chamber atrial) pacing does not affect the dyssynchronous function. This study compared waveform characteristics during CRT and AAI pacing at similar pacing rates using seismocardiogram (SCG) and gyrocardiogram (GCG), collectively known as mechanocardiogram (MCG).Approach.We included 10 patients with heart failure with reduced ejection fraction and previously implanted CRT pacemakers. ECG and MCG recordings were taken during AAI and CRT pacing at a heart rate of 80 bpm. Waveform characteristics, including energy, vertical range (amplitude) during systole and early diastole, electromechanical systole (QS2) and left ventricular ejection time (LVET), were derived by considering 6 MCG axes and 3 MCG vectors across frequency ranges of >1 Hz, 20-90 Hz, 6-90 Hz and 1-20 Hz.Main results.Significant differences were observed between CRT and AAI pacing. CRT pacing consistently exhibited higher energy and vertical range during systole compared to AAI pacing (p< 0.05). However, QS2, LVET and waveform characteristics around aortic valve closure did not differ between the pacing modes. Optimal differences were observed in SCG-Y, GCG-X, and GCG-Y axes within the frequency range of 6-90 Hz.Significance.The results demonstrate significant differences in MCG waveforms, reflecting improved mechanical cardiac function during CRT. This information has potential implications for predicting the clinical response to CRT. Further research is needed to explore the differences in signal characteristics between responders and non-responders to CRT.

High Bleeding Incidence in Unselected Hospitalized Suspected Non-ST-Segment Elevation Myocardial Infarction Patients Aged Under 65 Years

High bleeding risk (HBR) is commonly encountered among patients with acute coronary syndrome (ACS), and bleeding complications are associated with worse prognosis. Data on bleeding events of patients with ACS are based almost exclusively on percutaneous coronary intervention registries. Enrolling only patients suitable for invasive procedures might have skewed the observed bleeding incidence. We sought to investigate bleeding incidence in unselected patients with ACS. Patients were retrospectively enrolled between January and June 2019 from the emergency department of a tertiary hospital. All consecutive hospitalized adults with suspected non-ST-segment elevation myocardial infarction were included. Data was gathered by a database search and verified using electronic patient records. Bleeding risk was assessed according to the Academic Research Consortium for High Bleeding Risk (ARC-HBR) definition. The primary end point was a composite of post- discharge Bleeding Academic Research Consortium type 2, 3, and 5 bleeding during 1-year follow-up. Of the 209 included patients, 15 (7.2%) suffered a bleeding event. There were more bleeding events among dual antiplatelet therapy (DAPT) users as compared with those without DAPT (10.7% vs 3.1%, p = 0.033). Among HBR patients, 6.1% and in non-HBR patients 8.1% suffered a bleeding event (p = 0.579). Notably, major bleeding (Bleeding Academic Research Consortium type 3) incidence was highest in patients <65 years and without DAPT use. In conclusion, unselected suspected non-ST-segment elevation myocardial infarction patients aged <65 years had surprisingly high bleeding incidence, regardless of ARC-HBR status or DAPT use.

Processed fava bean as a substitute for rapeseed meal with or without rumen-protected methionine supplement in grass silage-based dairy cow diets

Fava bean offers a sustainable home-grown protein source for dairy cows, but fava bean protein is extensively degraded in the rumen and has low Met concentration. We studied the effects of protein supplementation and source on milk production, rumen fermentation, N use, and mammary AA utilization. The treatments were unsupplemented control diet, and isonitrogenously given rapeseed meal (RSM), processed (dehulled, flaked, and heated) fava bean without (TFB) or with rumen-protected (RP) Met (TFB+). All diets consisted of 50% grass silage and 50% cereal-based concentrate including studied protein supplement. The control diet had 15% of crude protein and protein-supplemented diets 18%. Rumen-protected Met in TFB+ corresponded to 15 g/d of Met absorbed in the small intestine. Experimental design was a replicated 4 × 4 Latin square with 3-wk periods. The experiment was conducted using 12 multiparous mid-lactation Nordic Red cows, of which 4 were rumen cannulated. Protein supplementation increased dry matter intake (DMI), and milk (31.9 vs. 30.7 kg/d) and milk component yields. Substituting RSM with TFB or TFB+ decreased DMI and AA intake but increased starch intake. There were no differences in milk yield or composition between RSM diet and TFB diets. Rumen-protected Met did not affect DMI, or milk or milk component yields but increased milk protein concentration in comparison to TFB. There were no differences in rumen fermentation except for increased ammonium-N concentration with the protein-supplemented diets. Nitrogen-use efficiency for milk production was lower for the supplemented diets versus control diet but tended to be greater for TFB and TFB+ versus RSM. Protein supplementation increased plasma essential AA concentration but there were no differences between TFB diets and RSM. Rumen-protected Met clearly increased plasma Met concentration (30.8 vs. 18.2 µmol/L) but did not affect other AA. Absence of differences between RSM and TFB in milk production together with limited effects of RP Met suggest that TFB is a potential alternative protein source for dairy cattle.

Mechanocardiography-Based Measurement System Indicating Changes in Heart Failure Patients during Hospital Admission and Discharge

Heart failure (HF) is a disease related to impaired performance of the heart and is a significant cause of mortality and treatment costs in the world. During its progression, HF causes worsening (decompensation) periods which generally require hospital care. In order to reduce the suffering of the patients and the treatment cost, avoiding unnecessary hospital visits is essential, as hospitalization can be prevented by medication. We have developed a data-collection device that includes a high-quality 3-axis accelerometer and 3-axis gyroscope and a single-lead ECG. This allows gathering ECG synchronized data utilizing seismo- and gyrocardiography (SCG, GCG, jointly mechanocardiography, MCG) and comparing the signals of HF patients in acute decompensation state (hospital admission) and compensated condition (hospital discharge). In the MECHANO-HF study, we gathered data from 20 patients, who each had admission and discharge measurements. In order to avoid overfitting, we used only features developed beforehand and selected features that were not outliers. As a result, we found three important signs indicating the worsening of the disease: an increase in signal RMS (root-mean-square) strength (across SCG and GCG), an increase in the strength of the third heart sound (S3), and a decrease in signal stability around the first heart sound (S1). The best individual feature (S3) alone was able to separate the recordings, giving 85.0% accuracy and 90.9% accuracy regarding all signals and signals with sinus rhythm only, respectively. These observations pave the way to implement solutions for patient self-screening of the HF using serial measurements.

Frequency of cardioversions as an additional risk factor for stroke in atrial fibrillation - the FinCV-4 study

BACKGROUND

Patients with atrial fibrillation (AF) are selected for oral anticoagulation based on individual patient characteristics. There is little information on how clinical AF burden associates with the risk of ischaemic stroke or systemic embolism (SSE). The aim of this study was to explore the association of the frequency of cardioversions (CV) as a measure of clinical AF burden on the long-term SSE risk, with a focus on patients at intermediate stroke risk based on CHA₂DS₂-VASc score. For these patients, additional SSE risk stratification by assessing CV frequency may aid in the decision on whether to initiate oral anticoagulation.

METHODS

This retrospective analysis of FinCV Study from years 2003-2010 included 2074 patients who were not using any oral anticoagulation (long term or temporary) after CVs and undergoing a total of 6534 CVs for AF from emergency departments of three hospitals. Two study groups were formed: high CV frequency (mean interval between CVs ≤12 months and low frequency (>12 months).

RESULTS

A total of 107 SSEs occurred during a mean follow-up of 5.4 years. The event rates per 100 patient-years were 1.82 and 0.67 in high versus low CV frequency groups, respectively. After adjustment for CHA₂DS₂-VASc score, CV frequency independently predicted SSE (HR, 2.87 [95% CI, 1.47 to 5.64]; p = .002) at 3 years. Competing risk analysis also identified CV frequency (sHR, 2.70 [95% CI, 1.38-5.31]; p = .004) as an independent predictor for SSE. In patients with CHA₂DS₂-VASc score 1 and low CV frequency, the SSE risk was only 0.08 per 100 patient-years.

CONCLUSIONS

Frequency of CVs for symptomatic AF episodes provides additional information on stroke risk in AF patients with CHA₂DS₂-VASc score 1.Key messagesThis retrospective study offers a unique opportunity to observe the natural course of AF patients with infrequent episodes of clinical arrhythmia when they were not using OAC (before introduction of CHA₂DS₂-VASc score).Stroke or systemic embolism rate was very low (0.08 per 100 patient-years) in patients with one CHA₂DS₂-VASc point who visited the emergency room for cardioversion less than once a year.Frequency of cardioversions can be used for additional risk stratification in patients at intermediate risk of stroke based on CHA₂DS₂-VASc score.

Association of CHA2DS2-VASc Score with Long-Term Incidence of New-Onset Atrial Fibrillation and Ischemic Stroke after Myocardial Infarction

The CHA2DS2-VASc score is a reliable tool used to estimate the risk of ischemic stroke (IS) in patients with atrial fibrillation (AF). Few tools exist for the prediction of new-onset AF (NOAF) after myocardial infarction (MI) and its relation to IS. We studied the usefulness of CHA2DS2-VASc in predicting NOAF and IS in a long-term follow-up after MI. Consecutive MI patients without baseline AF (n = 70,922; mean age: 68.2 years), discharged from 20 hospitals in Finland during 2005−2018, were retrospectively studied using national registries. The outcomes of interest after discharge were NOAF- and IS-assessed with competing risk analyses at one and ten years. The median follow-up was 4.2 years. The median baseline CHA2DS2-VASc score was 3 (IQR 2−5). The likelihood of both NOAF and NOAF-related IS increased stepwise with this score at one and ten years (all p < 0.0001). The one-year-adjusted subdistribution hazard ratio (sHR) was 4.03 (CI 3.68−4.42) for NOAF in patients with CHA2DS2-VASc scores ≥6 points. The cumulative incidence of IS was 15.2% in patients with NOAF vs. 6.2% in patients without AF at 10 years after MI (adj. sHR 2.12; CI 1.98−2.28; p < 0.0001). Coronary artery bypass surgery was associated with a higher NOAF incidence compared to percutaneous coronary intervention (adj. sHR 1.87; CI 1.65−2.13; p < 0.0001 one year after MI). The CHA2DS2-VASc score is a simple tool used to estimate the long-term risk of NOAF and IS after MI in patients without baseline AF. Coronary bypass surgery is associated with an increased NOAF incidence after MI.

Mechanocardiography in the Detection of Acute ST Elevation Myocardial Infarction: The MECHANO-STEMI Study

Novel means to minimize treatment delays in patients with ST elevation myocardial infarction (STEMI) are needed. Using an accelerometer and gyroscope on the chest yield mechanocardiographic (MCG) data. We investigated whether STEMI causes changes in MCG signals which could help to detect STEMI. The study group consisted of 41 STEMI patients and 49 control patients referred for elective coronary angiography and having normal left ventricular function and no valvular heart disease or arrhythmia. MCG signals were recorded on the upper sternum in supine position upon arrival to the catheterization laboratory. In this study, we used a dedicated wearable sensor equipped with 3-axis accelerometer, 3-axis gyroscope and 1-lead ECG in order to facilitate the detection of STEMI in a clinically meaningful way. A supervised machine learning approach was used. Stability of beat morphology, signal strength, maximum amplitude and its timing were calculated in six axes from each window with varying band-pass filters in 2-90 Hz range. In total, 613 features were investigated. Using logistic regression classifier and leave-one-person-out cross validation we obtained a sensitivity of 73.9%, specificity of 85.7% and AUC of 0.857 (SD = 0.005) using 150 best features. As a result, mechanical signals recorded on the upper chest wall with the accelerometers and gyroscopes differ significantly between STEMI patients and stable patients with normal left ventricular function. Future research will show whether MCG can be used for the early screening of STEMI.

Adherence to risk-assessment protocols to guide computed tomography pulmonary angiography in patients with suspected pulmonary embolism

AIMS

The use of computed tomography pulmonary angiography (CTPA) in the detection of pulmonary embolism (PE) has considerably increased due developing technology and better availability of imaging. The underuse of pre-test probability scores and overuse of CTPA has been previously reported. We sought to investigate the indications for CTPA at a University Hospital emergency clinic and seek for factors eliciting the potential overuse of CTPA.

METHODS AND RESULTS

Altogether 1001 patients were retrospectively collected and analysed from the medical records using a structured case report form. PE was diagnosed in 222/1001 (22.2%) of patients. Patients with PE had more often prior PE/deep vein thrombosis, bleeding/thrombotic diathesis and less often asthma, chronic obstructive pulmonary disease, coronary artery disease, or decompensated heart failure. Patients were divided into three groups based on Wells PE risk-stratification score and two groups based on the revised Geneva score. A total of 9/382 (2.4%), 166/527 (31.5%), and 47/92 (52.2%) patients had PE in the CTPA in the low, intermediate, and high pre-test likelihood groups according to Wells score, and 200/955 (20.9%) and 22/46 (47.8%) patients had PE in the CTPA in the low-intermediate and the high pre-test likelihood groups according to the revised Geneva score, respectively. D-dimer was only measured from 568/909 (62.5%) and 597/955 (62.5%) patients who were either in the low or the intermediate-risk group according to Wells score and the revised Geneva score. Noteworthy, 105/1001 (10.5%) and 107/1001 (10.7%) of the CTPAs were inappropriately ordered according to the Wells score and the revised Geneva score. Altogether 168/1001 (16.8%) could theoretically be avoided.

CONCLUSIONS

This study highlights scant utilization of guideline-recommended risk-stratification tools in CTPA use at the emergency department.

Minor troponin T elevation and mortality in patients with atrial fibrillation presenting to the emergency department

BACKGROUND

There are limited data on the association of minor troponin elevation in unselected patients with atrial fibrillation (AF) presenting to the emergency department (ED) with adverse events. In this study, we sought to assess the early and mid-term mortality of these patients.

METHODS

In this observational study, 2911 patients with AF were admitted to the ED. They were divided into 3 groups based on peak high-sensitivity troponin (TnT) levels: normal (<15 ng/L), 15-50 ng/L and 51-100 ng/L. The primary outcomes of this study were all-cause mortality at 30 days and 1 year.

RESULTS

All-cause mortality was 6.7% (n = 196) at 30 days and 22.2% (n = 646) at 1 year. Mortality rate increased along with increasing levels of TnT irrespective of baseline covariates, primary discharge diagnosis and type of AF. A significant association between TnT levels and all-cause mortality was observed. The adjusted hazard ratio (HR) at 30 days was 6.02 (95% CI 2.62-13.83) for TnT 15-50 ng/L and 11.28 (95% CI 4.87-26.12) for TnT 51-100 ng/L (P<.001 for both) compared to TnT <15 ng/L. At 1 year, the adjusted HRs were 3.08 (95% CI 2.15-4.40) and 5.07 (95% CI 3.49-7.35), respectively (P < .001). When patients with TnT <15 ng/L were divided into two groups at the median value, TnT elevation of 10 to 14 ng/L was also associated with increased 1-year mortality (HR 2.51; 95% CI 1.09-5.74; P = .03).

CONCLUSIONS

Among patients with AF admitted to the ED, increased TnT levels were associated with increased early and mid-term all-cause mortality irrespective of baseline covariates and type of AF.

Effects of faba bean, blue lupin and rapeseed meal supplementation on nitrogen digestion and utilization of dairy cows fed grass silage-based diets

There is increasing interest in using locally produced protein supplements in dairy cow feeding. The objective of this experiment was to compare rapeseed meal (RSM), faba beans (FBs) and blue lupin seeds (BL) at isonitrogenous amounts as supplements of grass silage and cereal based diets. A control diet (CON) without protein supplement was included in the experiment. Four lactating Nordic Red cows were used in a 4 × 4 Latin Square design with four 21 d periods. The milk production increased with protein supplementation but when expressed as energy corrected milk, the response disappeared due to substantially higher milk fat concentration with CON compared to protein supplemented diets. Milk protein output increased by 8.5, 4.4 and 2.7% when RSM, FB and BL were compared to CON. The main changes in rumen fermentation were the higher propionate and lower butyrate proportion of total rumen volatile fatty acids when the protein supplemented diets were compared to CON. Protein supplementation also clearly increased the ruminal ammonia N concentration. Protein supplementation improved diet organic matter and NDF digestibility but efficiency of microbial protein synthesis per kg organic matter truly digested was not affected. Flow of microbial N was greater when FB compared to BL was fed. All protein supplements decreased the efficiency of nitrogen use in milk production. The marginal efficiency (amount of additional feed protein captured in milk protein) was 0.110, 0.062 and 0.045 for RSM, FB and BL, respectively. The current study supports the evidence that RSM is a good protein supplement for dairy cows, and this effect was at least partly mediated by the lower rumen degradability of RSM protein compared to FB and BL. The relatively small production responses to protein supplementation with simultaneous decrease in nitrogen use efficiency in milk production suggest that economic and environmental consequences of protein feeding need to be carefully considered.

Subtype of atrial fibrillation and the outcome of transcatheter aortic valve replacement: The FinnValve Study

Whether the subtype of atrial fibrillation affects outcomes after transcatheter aortic valve replacement for aortic stenosis is unclear. The nationwide FinnValve registry included 2130 patients who underwent primary after transcatheter aortic valve replacement for aortic stenosis during 2008-2017. Altogether, 281 (13.2%) patients had pre-existing paroxysmal atrial fibrillation, 651 (30.6%) had pre-existing non-paroxysmal atrial fibrillation and 160 (7.5%) were diagnosed with new-onset atrial fibrillation during the index hospitalization. The median follow-up was 2.4 (interquartile range: 1.6-3.8) years. Paroxysmal atrial fibrillation did not affect 30-day or overall mortality (p-values >0.05). Non-paroxysmal atrial fibrillation demonstrated an increased risk of overall mortality (hazard ratio: 1.61, 95% confidence interval: 1.35-1.92; p<0.001), but not 30-day mortality (p = 0.084). New-onset atrial fibrillation demonstrated significantly increased 30-day mortality (hazard ratio: 2.76, 95% confidence interval: 1.25-6.09; p = 0.010) and overall mortality (hazard ratio: 1.68, 95% confidence interval: 1.29-2.19; p<0.001). The incidence of early or late stroke did not differ between atrial fibrillation subtypes (p-values >0.05). In conclusion, non-paroxysmal atrial fibrillation and new-onset atrial fibrillation are associated with increased mortality after transcatheter aortic valve replacement for aortic stenosis, whereas paroxysmal atrial fibrillation has no effect on mortality. These findings suggest that non-paroxysmal atrial fibrillation rather than paroxysmal atrial fibrillation may be associated with structural cardiac damage which is of prognostic significance in patients with aortic stenosis undergoing transcatheter aortic valve replacement.

Association of Heart Rate With Troponin Levels Among Patients With Symptomatic Atrial Fibrillation

This cohort study investigates heart rate and cardiac troponin levels in patients admitted to the emergency department with symptomatic atrial fibrillation.

Effectiveness of Only Aspirin or Clopidogrel Following Percutaneous Left Atrial Appendage Closure

Percutaneous left atrial appendage closure (LAAC) offers a feasible option for stroke prevention in patients with atrial fibrillation (AF), but the optimal antithrombotic treatment strategy for patients with strict contraindications to oral anticoagulation (OAC) remains uncertain. We sought to evaluate short- and long-term outcome after percutaneous LAAC in these very patients discharged on single antiplatelet therapy (SAPT) alone. All consenting AF patients who underwent LAAC from February 2009 to August 2018 in Turku University Hospital, Finland, were enrolled into a prospectively maintained registry. Only patients discharged on SAPT alone were considered for the present analysis. Patients were prospectively followed up to 5 years. The primary end points were thromboembolic event (stroke, transient ischemic attack, or systemic embolism) and intracranial bleeding. Of the 165 LAAC patients, 81 patients (mean age 75 ± 7 years; 44% women; CHA₂DS₂-VASc 4.8 ± 1.4; HAS-BLED 3.2 ± 0.8) were discharged on SAPT only (77 with aspirin 100 mg) after successful LAAC using Amplatzer devices. The duration of SAPT was ≤6 months in 61 (75%) patients. The most common contraindication to OAC was previous intracranial bleeding in 48 (59%) patients. During a mean follow-up of 2.9 years, there were 6 thromboembolic events (2.7 of 100 patient-years; 73% lower-than-predicted rate of thromboembolism). Eight patients (3.6 of 100 patient-years) had a major bleeding event after discharge, and 4 patients had intracerebral bleeding (1.7 of 100 patient-years). At 6-month landmark analysis, freedom from thromboembolism and intracranial bleeding at 3-year follow-up was similar in those with discontinued and life-long SAPT (95.1% vs 88.9% and 97.6% vs 91.7%, respectively). In conclusion, long-term outcome is satisfactory after LAAC in selected AF patients with strict contraindications to OAC receiving short-term SAPT. However, adverse events are not infrequent during early postoperative months.

Effects of different barley and oat varieties on methane production, digestibility, and fermentation pattern in vitro

The objective of this in vitro study was to determine the effects of different barley and oat varieties on CH₄ production, digestibility, and rumen fermentation patterns in dairy cows. Our hypothesis was that oat-based diets would decrease CH₄ production compared with barley-based diets, and that CH₄ production would differ between varieties within grain species. To evaluate this hypothesis, we conducted an in vitro experiment using a fully automated gas production technique, in which the total gas volume was automatically recorded by the system. The experiment consisted of triplicate 48-h incubations with 16 treatments, including 8 different varieties of each grain. The grain varieties were investigated as a mix with an early-cut grass silage (1:1 ratio of grain to silage on a dry matter basis) and mixed with buffered rumen fluid. We estimated predicted in vivo total gas production and CH₄ production by applying a set of models to the gas production data obtained by the in vitro system. We also evaluated in vitro digestibility and fermentation characteristics. The variety of grain species did not affect total gas production, CH₄ production, or fermentation patterns in vitro. However, in vitro-determined digestibility and pH were affected by variety of grain species. Grain species affected total gas and CH₄ production: compared with barley-based diets, oat-based diets decreased total gas production and CH₄ production by 8.2 and 8.9%, respectively, relative to dry matter intake. Grain species did not affect CH₄ production relative to in vitro true dry matter digestibility. Oat-based diets decreased digestibility and total volatile fatty acid production, and maintained a higher pH at 48 h of incubation compared with barley-based diets. Grain species did not affect fermentation patterns, except for decreased molar proportions of valerate with oat-based diets. These results suggest that replacing barley with oats in dairy cow diets could decrease enteric CH₄ production.

P4420Is exercise-induced cardiac troponin release caused by skeletal muscle injury?

Background

Cardiac troponins (cTn) are highly sensitive and specific markers for cardiac injury and a key element in the diagnosis of acute coronary syndrome. Strenuous exercise is known to induce increases in cTn, but the causative factors remain ambiguous. It is also equivocal whether exercise induced skeletal muscle injury is associated with cTn elevation.

Purpose

The aim of this study was to identify independent predictors for the rise in cardiac troponin T (cTnT) and I (cTnI) concentration and to focus on the relationship between skeletal muscle injury measured by skeletal troponin I (skTnI) and cTn elevations after a marathon race in a large group of male recreational runners.

Methods

A total of 40 recreational runners participating in the marathon in our city were recruited. The study included baseline visit (prerace) and immediate post-race sampling.

Results

The post-marathon cTnT concentration rose above the reference limit in 38 (95%) participants and the detection limit for cTnI was exceeded in 34 (85%) participants. Similarly, a 10-fold increase in skTnI concentration was observed and elevated post-race values were seen in all participants. There was no significant correlation between the post-race cTnT or cTnT change and post-race skTnI (Spearman's rho = 0.249, p=0.122, rho = 0.285, p=0.074). However, post-race cTnI and change in cTnI were associated with post-race skTnI (rho = 0.404, p=0.01, rho = 0.460, p=0.003) and creatine kinase (r=0.368, p=0.019) concentration. Subjective exertion or self-reported muscle symptoms did not correlate with post-race cTnT, cTnI or skTnI levels.

Post-Race cTnT <40 Post-Race cTnT ≥40 p-value n=18 n=22 Age, years 53.3±12.2 44.0±11.9 0.002 Active training, years 12.0 (9.3) 17.0 (15.8) 0.190 Muscle symptoms 7 (38.9) 11 (52.4) 0.523 Creatinine kinase, ug/l 406 (137) 399 (319) 0.163 N-terminal proBNP ng/l 137±168 158±277 0.783 Skeletal Troponin I, ng/ml 28.6 (41) 56.7 (143) 0.199

Figure 1

Conclusions

Cardiac troponin became abnormal in almost all runners after marathon race. The exercise-induced rise in cardiac troponin I is related to simultaneous release of skeletal troponin I. The mechanism of this association remains uncertain, but clinicians should be cautious when interpreting post-exercise troponin levels without clinical symptoms and signs of myocardial ischemia.

P3726Percutaneous left atrial appendage closure and conservative antithrombotic treatment in patients with atrial fibrillation and contraindication to oral anticoagulation: a 5-year follow-up study

Background

Patients with atrial fibrillation (AF) having high thromboembolic risk and either a history of major bleeding or very high bleeding risk form a treatment challenge. Percutaneous left atrial appendage closure (LAAC) offers a feasible option for stroke prevention in these patients. However, the optimal treatment strategy for AF patients with contraindications to oral anticoagulation (OAC) remains unclear.

Purpose

To study periprocedural and late events after LAAC in AF patients with contraindications to OAC therapy.

Methods

Data were collected into a prospective registry from all consenting AF patients who underwent LAAC from February 2009 to August 2018. Follow-up data was gathered during scheduled clinical visits, annual phone calls and by reviewing electronic patient records. Only AF patients with contraindications to OAC were considered for the present analysis.

Results

LAAC using mainly Amplatzer Cardiac Plugs (98.2%) was attempted in a total of 172 patients (mean age 74 years; 60 women). The mean CHA2DS2-VASc score was 3.8±1.5 and HAS-BLED score 4.0±1.0. Contraindications to OAC were prior intracranial bleeding in 112 (65.1%), other major bleeding in 33 (19.2%) and high bleeding risk in 27 patients (15.7%). Procedure was technically successful in 166 (96.5%) patients. Clinically significant in-hospital complications were as follows: two patients (1.2%) had cardiac tamponade, which was fatal in one case, one (0.6%) had device embolization and eight (4.7%) had major access site-related bleeding events. None of the patients had in-hospital thromboembolic complications. After successful implantation, 152 patients (91.6%) were discharged on aspirin. Single antiplatelet therapy was more common than dual or triple antiplatelet therapy (74.7% vs. 18.1% vs. 1.8%, respectively), while 8 patients (4.8%) received no antiplatelet therapy. The length of initial antiplatelet therapy ranged from 0.5 to 12 months and long-term antiplatelet therapy was prescribed in 53 patients (31.9%). After a median follow-up of 33 months (interquartile range 12–49) there were 29 deaths (17.5%), 16 thromboembolic events (9.6%), consisting of 11 strokes (6.6%) and 5 transient ischemic attacks (3.0%). At the time of thromboembolic event, 10 patients (62.5%) were on antithrombotic therapy. Eighteen patients (10.8%) had at least one major bleeding event after the index hospitalization. Intracranial bleeding occurred in 7 patients (4.2%) and 6 of them (85.7%) were on antithrombotic therapy when the event occurred. Most thromboembolic events (68.8%) and intracranial bleedings (57.1%) occurred after one year of follow-up. One patient (0.6%) had an asymptomatic device embolization detected at 3-month control visit. No predictive factors for thromboembolic or major bleeding events were identified.

Conclusion

The early outcome of this challenging patient group is good after LAAC, but thromboembolic and major bleeding events are not uncommon during later follow-up.

The effect of partial substitution of rapeseed meal and faba beans by Spirulina platensis microalgae on milk production, nitrogen utilization, and amino acid metabolism of lactating dairy cows

Alternative protein sources such as microalgae and faba beans may have environmental benefits over rapeseed. We studied the effects of rapeseed meal (RSM) or faba beans (FB) as a sole protein feed or as protein feeds partially substituted with Spirulina platensis (spirulina) microalgae on milk production, N utilization, and AA metabolism of dairy cows. Eight multiparous Finnish Ayrshire cows (113 ± 36.3 d in milk; mean ± SD) were used in a balanced, replicated 4 × 4 Latin square with 2 × 2 factorial arrangement of treatments and 21-d periods. Four cows in one Latin square were rumen cannulated. Treatments were 2 isonitrogenously fed protein sources, RSM or rolled FB, or one of these sources with half of its crude protein substituted by spirulina (RSM-SPI and FB-SPI). Cows had ad libitum access to total mixed rations consisting of grass silage, barley, sugar beet pulp, minerals, and experimental protein feed. The substitution of RSM with FB did not affect dry matter intake (DMI) but decreased neutral detergent fiber intake and increased the digestibility of other nutrients. Spirulina in the diet decreased DMI and His intake. Spirulina had no effect on Met intake in cows on RSM diets but increased it in those on FB diets. Energy-corrected milk (ECM) and protein yields were decreased when RSM was substituted by FB. Milk and lactose yields were decreased in cows on the RSM-SPI diet compared with the RSM diet but increased in those on FB-SPI compared with FB. The opposite was true for milk fat and protein concentrations; thus, spirulina in the diet did not affect ECM. Feed conversion efficiency (ECM:DMI) increased in cows on FB diets with spirulina, whereas little effect was observed for those on RSM diets. The substitution of RSM by FB decreased arterial concentration of Met and essential AA. Spirulina in the diet increased milk urea N and ruminal NH₄-N and decreased the efficiency of N utilization in cows on RSM diets, whereas those on FB diets showed opposite results. Met likely limited milk production in cows on the FB diet as evidenced by the decrease in arterial Met concentration and milk protein yield when RSM was substituted by FB. The results suggest the potential to improve milk production response to faba beans with supplementation of Met-rich feeds such as spirulina. This study also confirmed spirulina had poorer palatability than RSM and FB despite total mixed ration feeding and lower milk production when spirulina partially replaced RSM.

Clinical assessment of a non-invasive wearable MEMS pressure sensor array for monitoring of arterial pulse waveform, heart rate and detection of atrial fibrillation

There is an unmet clinical need for a low cost and easy to use wearable devices for continuous cardiovascular health monitoring. A flexible and wearable wristband, based on microelectromechanical sensor (MEMS) elements array was developed to support this need. The performance of the device in cardiovascular monitoring was investigated by (i) comparing the arterial pressure waveform recordings to the gold standard, invasive catheter recording (n = 18), (ii) analyzing the ability to detect irregularities of the rhythm (n = 7), and (iii) measuring the heartrate monitoring accuracy (n = 31). Arterial waveforms carry important physiological information and the comparison study revealed that the recordings made with the wearable device and with the gold standard device resulted in almost identical (r = 0.9–0.99) pulse waveforms. The device can measure the heart rhythm and possible irregularities in it. A clustering analysis demonstrates a perfect classification accuracy between atrial fibrillation (AF) and sinus rhythm. The heartrate monitoring study showed near perfect beat-to-beat accuracy (sensitivity = 99.1%, precision = 100%) on healthy subjects. In contrast, beat-to-beat detection from coronary artery disease patients was challenging, but the averaged heartrate was extracted successfully (95% CI: −1.2 to 1.1 bpm). In conclusion, the results indicate that the device could be useful in remote monitoring of cardiovascular diseases and personalized medicine.

CHA2DS2-VASc score predicts atrial fibrillation recurrence after cardioversion: Systematic review and individual patient pooled meta-analysis

BACKGROUND

Despite progresses in the treatment of the thromboembolic risk related to atrial fibrillation (AF), the management of recurrences remains a challenge.

HYPOTHESIS

To assess if congestive heart failure or left ventricular systolic dysfunction (CHA2 DS2 -VASc) score is predictive of early arrhythmia recurrence after AF cardioversion.

METHODS

Systematic review and individual patient pooled meta-analysis following Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines.

INCLUSION CRITERIA

observational trials in patients with AF undergoing cardioversion, available data on recurrence of AF and available data on CHA2 DS2 -VASc score. Clinical studies of interest were retrieved by PubMed, Cochrane Library, and Biomed Central. Seven authors were contacted for joining the patient level meta-analysis, and three shared data regarding anthropometric measurements, risk factors, major comorbidities, and CHA2 DS2 -VASc score. The primary outcome was the recurrence of AF after cardioversion in patients free from antiarrhythmic prophylaxis. Univariate and multivariate logistic regression was performed.

RESULTS

Overall, we collect data of 2889 patients: 61% were male, 50% with hypertension, 12% with diabetes, and 23% with history of ischemic heart disease. The median CHA2DS2-VASc score was 2.. At the multivariate analysis, chronic kidney disease (odds ratio [OR] 1.94; 95% confidence interval [CI] 1.12-3.27; P = 0.01), peripheral artery disease (OR 1.65; 95% CI 1.23-2.19; P < 0,0001), previous use of beta blockers (OR 1.5; 95% CI 1.19-1.88; P < 0.0001), and CHA2DS2-VASc score > 2 (OR 1.37; 95% CI 1.1-1.68; P = 0.002) were independent predictors of early recurrence of AF.

CONCLUSIONS

CHA2DS2-VASc score predicts early recurrence of AF in the first 30 days after electrical or pharmacological cardioversion. Protocol registration PROSPERO (CRD42017075107).

Hybrid coronary computed tomography angiography and positron emission tomography myocardial perfusion imaging in evaluation of recurrent symptoms after coronary artery bypass grafting

Aims

Recurrent chest pain after coronary artery bypass grafting (CABG) poses a diagnostic challenge. We hypothesized that combining anatomy of bypass grafts and native coronary arteries with ischaemia detection by hybrid imaging could be used to gain valuable and complementary information in patients with recurrent symptoms after CABG.

Methods and results

We analysed 36 consecutive patients (67 ± 9 years, 81% male) who had undergone hybrid imaging using coronary computed tomography angiography (CCTA) and [15O]H2O positron emission tomography (PET) myocardial perfusion imaging due to recurrent symptoms after CABG. Coronary tree and left ventricular myocardium were divided into three main territories, yielding a total of 108 coronary territories in 36 patients. The presence of obstructive (≥50%) stenosis and the patency of grafts were evaluated by CCTA, while myocardial ischaemia was assessed by quantitative adenosine-stress PET. Altogether 28 (78%) of the 36 study patients presented with matched PET/CCTA abnormalities. Forty-one coronary territories were supplied by non-obstructed bypass grafts or native coronary arteries (protected territory). However, 12 (29%) of these presented with a perfusion defect. In six cases, the perfusion defect involved myocardium distal to the graft-coronary anastomosis, as interpreted on the PET/CCTA fusion images. In turn, in 48 coronary territories the supplying artery was obstructed on CCTA (unprotected territory). Of these, 41 (85%, P < 0.001 vs. protected) presented with abnormal perfusion, involving myocardium distal to the anastomosis in 29 cases.

Conclusion

Hybrid imaging provides complementary information on the presence and localization of atherosclerotic lesions and myocardial perfusion abnormalities in symptomatic patients with previous CABG.

Cardioversion for atrial fibrillation - how to prevent thromboembolic complications?

Cardioversion is an essential component of rhythm control strategy for atrial fibrillation. The thromboembolic risk of cardioversion is well established and the mechanisms behind the phenomenon have been comprehensively described. There are several clinical aspects that are important to take into consideration when assessing the safety of cardioversion. Before proceeding to cardioversion, the probability of early treatment failure and antiarrhythmic treatment options to prevent recurrences should be carefully evaluated to avoid the risks of repeated futile cardioversions. Effective periprocedural anticoagulation is the mainstay in thromboembolic complication prevention and the first week after rhythm conversion is the most vulnerable period in this respect. Early timing of cardioversion appears to be another important measure to decrease the risk of thromboembolic complications. Transoesophageal echocardiography is useful in clinical scenarios where early cardioversion is desirable due to debilitating clinical symptoms and a short duration of arrhythmia or the adequacy of preceding anticoagulation is uncertain. However, it does not lessen the need for effective anticoagulation after cardioversion. This review summarizes the recent scientific discoveries to improve the safety of cardioversion for atrial fibrillation. Key messages Cardioversion for atrial fibrillation entails a significant risk of thromboembolic complications, especially during the first week after the procedure. The intensity of periprocedural anticoagulation and the timing of cardioversion appear to be significant determinants of the risk of thromboembolism. Awareness of the clinical aspects influencing cardioversion safety should be raised.

Usefulness of the CHA2DS2-VASc and HAS-BLED Scores in Predicting the Risk of Stroke Versus Intracranial Bleeding in Patients With Atrial Fibrillation (from the FibStroke Study)

CHA₂DS₂-VASc and HAS-BLED scores stratify the risk of thromboembolic and bleeding events respectively in patients with atrial fibrillation. There is only little information on how they differentiate which of the 2 clinically most important complications (ischemic stroke [IS] or an intracranial bleeding [IB]) the patient is more prone to suffer. We evaluated both scores in patients with either of these major complications. The FibStroke Study collected data on all patients with atrial fibrillation with either an IS or an IB event between 2003 and 2012 in 4 Finnish hospital districts. Individual electronic patient records were manually reviewed to collect the study data. To assess the relative risk of IS and IB, an IS/IB-ratio was calculated by dividing the absolute number of ISs with the absolute number of IBs within each score category. A total of 3,816 (82.7%) ISs and 798 (17.3%) IBs were detected in 3,909 patients. In general, ISs occurred more often than IBs in patients on oral anticoagulation in each score category (ratio 1.6 to 5.1). The ratio decreased below 1, however, only with very high HAS-BLED scores (>4). Moreover, 221 ISs and 53 IBs occurred in patients with HAS-BLED > CHA₂DS₂-VASc, of whom only 19.7% were on anticoagulation. In conclusion, IS was the predominant intracranial event irrespective of CHA₂DS₂-VASc score, HAS-BLED score ≤4, or use of oral anticoagulation, also in patients with low estimated thromboembolic risk (CHA₂DS₂-VASc 0 to 1). Furthermore, the HAS-BLED score predicted the excess of IBs over ISs only at very high-risk levels.

Clinical manifestations and outcomes of severe warfarin overanticoagulation: from the EWA study

INTRODUCTION

Severe warfarin overanticoagulation is a risk factor for bleeding, but there is little information on its manifestations, prognosis and factors affecting the outcome. We describe the manifestations and clinical outcomes of severe warfarin overanticoagulation in a large group of patients with atrial fibrillation (AF).

MATERIAL AND METHODS

All international normalized ratio (INR) samples (n = 961,431) in the Turku University Hospital region between 2003 and 2015 were screened. A total of 412 AF patients with INR ≥9 were compared to 405 patients with stable warfarin anticoagulation for AF. Electronic patient records were manually reviewed to collect comprehensive data.

RESULTS

Of the 412 patients with INR ≥9, bleeding was the primary manifestation in 105 (25.5%). Non-bleeding symptoms were recorded in 165 (40.0%) patients and 142 (34.5%) had no symptoms. A total of 17 (16.2%) patients with a bleed and 67 (21.8%) without bleeding died within 30 days after the event. Intracranial haemorrhage strongly predicted death within 30 days. Other significant predictors were non-bleeding symptoms, active malignancies, recent bleed, history of myocardial infarction, older age, renal dysfunction and a recent treatment episode.

CONCLUSIONS

Bleeds are not the major determinant of the poor prognosis in severe overanticoagulation, as coincidental INR ≥9 findings also associate with high mortality. KEY MESSAGES Only a quarter of AF patients with INR ≥9 suffered a bleeding event and the clinical manifestation of INR ≥9 had a significant impact on patient outcome. The 30-day mortality rate in patients with INR ≥9 was high ranging from 9.2 to 32.7%. Several significant predictors of 30-day mortality after INR ≥9 were identified.

Incidence and predictors of excessive warfarin anticoagulation in patients with atrial fibrillation-The EWA study

Vitamin K antagonist warfarin is widely used in clinical practice and excessive anticoagulation is a well-known complication of this therapy. Little is known about permanent and temporary predictors for severe overanticoagulation. The aim of this study was to investigate the occurrence and predicting factors for episodes with very high (≥9) international normalized ratio (INR) values in warfarin treated patients with atrial fibrillation (AF). Excessive Warfarin Anticoagulation (EWA) study screened all patients (n = 13618) in the Turku University Hospital region with an INR ≥2 between years 2003–2015. Patients using warfarin anticoagulation for AF with very high (≥9) INR values (EWA Group) were identified (n = 412 patients) and their characteristics were compared to a control group (n = 405) of AF patients with stable INR during long-term follow-up. Over 20% (n = 92) of the EWA patients had more than one event of very high INR and in 105 (25.5%) patients EWA led to a bleeding event. Of the several temporary and permanent EWA risk factors observed, strongest were excessive alcohol consumption in 9.6% of patients (OR 24.4, 95% CI 9.9–50.4, p<0.0001) and reduced renal function (OR 15.2, 95% CI 5.67–40.7, p<0.0001). Recent antibiotic or antifungal medication, recent hospitalization or outpatient clinic visit and the first 6 months of warfarin use were the most significant temporary risk factors for EWA. Excessive warfarin anticoagulation can be predicted with several permanent and temporary clinical risk factors, many of which are modifiable.

Predicting Unsuccessful Electrical Cardioversion for Acute Atrial Fibrillation (from the AF-CVS Score)

Electrical cardioversion (ECV) is the standard treatment for acute atrial fibrillation (AF), but identification of patients with increased risk of ECV failure or early AF recurrence is of importance for rational clinical decision-making. The objective of this study was to derive and validate a clinical risk stratification tool for identifying patients at high risk for unsuccessful outcome after ECV for acute AF. Data on 2,868 patients undergoing 5,713 ECVs of acute AF in 3 Finnish hospitals from 2003 through 2010 (the FinCV study data) were included in the analysis. Patients from western (n = 3,716 cardioversions) and eastern (n = 1,997 cardioversions) hospital regions were used as derivation and validation datasets. The composite of cardioversion failure and recurrence of AF within 30 days after ECV was recorded. A clinical scoring system was created using logistic regression analyses with a repeated-measures model in the derivation data set. A multivariate analysis for prediction of the composite end point resulted in identification of 5 clinical variables for increased risk: Age (odds ratio [OR] 1.31, confidence interval [CI] 1.13 to 1.52), not the First AF (OR 1.55, CI 1.19 to 2.02), Cardiac failure (OR 1.52, CI 1.08 to 2.13), Vascular disease (OR 1.38, CI 1.11 to 1.71), and Short interval from previous AF episode (within 1 month before ECV, OR 2.31, CI 1.83 to 2.91) [hence, the acronym, AF-CVS]. The c-index for the AF-CVS score was 0.67 (95% CI 0.65 to 0.69) with Hosmer-Lemeshow p value 0.84. With high (>5) scores (i.e., 12% to 16% of the patients), the rate of composite end point was ∼40% in both cohorts, and among low-risk patients (score <3), the composite end point rate was ∼10%. In conclusion, the risk of ECV failure and early recurrence of AF can be predicted with simple patient and disease characteristics.

Effect of incremental amounts of camelina oil on milk fatty acid composition in lactating cows fed diets based on a mixture of grass and red clover silage and concentrates containing camelina expeller

Camelina is an ancient oilseed crop that produces an oil rich in cis-9,cis-12 18:2 (linoleic acid, LA) and cis-9,cis-12,cis-15 18:3 (α-linolenic acid, ALA); however, reports on the use of camelina oil (CO) for ruminants are limited. The present study investigated the effects of incremental CO supplementation on animal performance, milk fatty acid (FA) composition, and milk sensory quality. Eight Finnish Ayrshire cows (91d in milk) were used in replicated 4×4 Latin squares with 21-d periods. Treatments comprised 4 concentrates (12kg/d on an air-dry basis) based on cereals and camelina expeller containing 0 (control), 2, 4, or 6% CO on an air-dry basis. Cows were offered a mixture of grass and red clover silage (RCS; 1:1 on a dry matter basis) ad libitum. Incremental CO supplementation linearly decreased silage and total dry matter intake, and linearly increased LA, ALA, and total FA intake. Treatments had no effect on whole-tract apparent organic matter or fiber digestibility and did not have a major influence on rumen fermentation. Supplements of CO quadratically decreased daily milk and lactose yields and linearly decreased milk protein yield and milk taste panel score from 4.2 to 3.6 [on a scale of 1 (poor) to 5 (excellent)], without altering milk fat yield. Inclusion of CO linearly decreased the proportions of saturated FA synthesized de novo (4:0 to 16:0), without altering milk fat 18:0, cis-9 18:1, LA, and ALA concentrations. Milk fat 18:0 was low (<5g/100g of FA) across all treatments. Increases in CO linearly decreased the proportions of total saturates from 58 to 45g/100g of FA and linearly enriched trans-11 18:1, cis-9,trans-11 18:2, and trans-11,cis-15 18:2 from 5.2, 2.6, and 1.7 to 11, 4.3, and 5.8g/100g of FA, respectively. Furthermore, CO quadratically decreased milk fat trans-10 18:1 and linearly decreased trans-10,cis-12 18:2 concentration. Overall, milk FA composition on all treatments suggested that one or more components in camelina seeds may inhibit the complete reduction of 18-carbon unsaturates in the rumen. In conclusion, CO decreased the secretion of saturated FA in milk and increased those of the trans-11 biohydrogenation pathway or their desaturation products. Despite increasing the intake of 18-carbon unsaturated FA, CO had no effect on the secretions of 18:0, cis-9 18:1, LA, or ALA in milk. Concentrates containing camelina expeller and 2% CO could be used for the commercial production of low-saturated milk from grass- and RCS-based diets without major adverse effects on animal performance.

Sense of coherence and health behaviour in adolescence

AIM

To explore associations of Sense of coherence (SOC) with health behaviour and social competence among 15-year-old adolescents.

METHODS

Study population is a prospective cohort of a randomized cluster sample of families and their first-born children from south-western Finland in 1986-1987. In this study, cross-sectional data of the 15-year-olds were used. The present data were based on mailed, pretested questionnaires. The outcome variable, SOC, was based on the 13-item scale of Antonovsky's Orientation to Life Questionnaire (OLQ). The principal explanatory variables were health behaviour, including experienced oral health, and social competence. The statistical analysis was performed using linear regression modelling.

RESULTS

Strong SOC of adolescents associated significantly with lighter use of alcohol, being a non-smoker, better care of oral health and better social competence compared with the others.

CONCLUSION

Sense of coherence is a useful tool for identifying adolescents in need of extra support and motivation for their health behaviour.

Dental fear: one single clinical question for measurement

A new dental fear measurement instrument, the Short Dental Fear Question (SDFQ), was developed and tested for clinical practice purposes. The correlations of the SDFQ with the Dental Anxiety Scale (DAS) and the Dental Fear Survey (DFS) were tested in 15-16-year-old adolescents. The Spearman correlations (rs) between the dental fear measurement instruments were: SDFQ – DFS: r_s = 0.79, n = 26; DFS – DAS: r_s = 0.72, n = 26; SDFQ– DAS: r_s = 0.69, n = 27. DAS and DFS mean scores were clearly higher in the SDFQ fear group than SDFQ in the relaxed group. The SDFQ is a short and compact instrument which might be convenient for the measurement of dental fear in clinical practice.

Screening and selection of lactic acid bacteria strains suitable for ensiling grass

AIM

Lactic acid bacteria (LAB) strains shown to have broad-spectrum antimicrobial activity were screened for potential as grass silage inoculants. The strains capable of rapidly lowering the pH of the grass matrix and with low proteolytic activity were assessed in laboratory-scale silos in a grass matrix containing natural microbial flora.

METHODS AND RESULTS

Screening of nine candidate strains was performed first in a grass extract medium. The four most promising strains were selected on the basis of growth rate in the medium, capacity to reduce pH and ability to limit the formation of ammonia-N. The efficiency of the selected strains was further assessed in a laboratory-scale ensiling experiment. Untreated (no additive) and formic acid served as controls. All tested inoculants improved silage quality compared with untreated. With one exception (Pediococcus parvulus E315) the fermentation losses in the inoculated silages were even lower than in the acid-treated control silage. Pure lactic acid fermentation was obtained in the timothy-meadow fescue silage with all inoculants. The results obtained in the ensiling experiments were consistent with those of the screening procedure, which appeared to predict correctly the potential of LAB as silage inoculants. The strains with a low ammonia production rate in the grass extract medium behaved similarly in the silage. Especially in this respect the strain Lactobacillus plantarum E76 was superior to the other candidates.

CONCLUSIONS

The screening method using grass extract proved to be useful in strain selection.

SIGNIFICANCE AND IMPACT OF THE STUDY

The rapid screening method developed for the LAB strains provides a useful tool for more systematic product development of commercial inoculant preparations. Time consuming and laborious ensiling experiments can be limited only to the most promising strains.

Effects of Replacing Grass Silage with Barley Silage in Dairy Cow Diets

This study examined the effects of gradually replacing grass silage with whole-crop barley silage on feed intake, ruminal and total tract digestibility, and milk yield in lactating dairy cows. Four dairy cows in early lactation, equipped with rumen cannulas, were fed 4 diets over four 21-d periods. The diets consisted of 4 forage mixtures of grass silage and whole-crop barley silage supplemented with 8.9 kg/d of concentrates [dry matter (DM) basis]. The proportion of barley silage in the forage was adjusted to 0, 0.20, 0.40, and 0.60 kg/ kg of DM. Ruminal nutrient metabolism was measured on the basis of digesta flow entering the omasal canal. Ammonia concentrations and volatile fatty acid profiles were determined in the rumen fluid. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Replacement of grass silage with barley silage had no effect on DM, digestible organic matter, or neutral detergent fiber (NDF) intake, but starch intake increased, whereas nitrogen and digestible NDF (dNDF) intake decreased. Increases in the proportion of barley silage linearly decreased milk yield, and the molar proportion of acetate in the rumen, and increased that of propionate, butyrate, and valerate. Decreases in milk yield due to inclusion of barley silage were attributed to decreases in diet digestibility and nutrient supply to the animal. Barley silage linearly decreased organic matter digestibility in the total tract and NDF and dNDF digestibility in the rumen and the total tract, and decreased nonammonia N flow entering the omasal canal. No significant differences between diets were noted in the digestion rate of dNDF or passage rate of indigestible NDF from the rumen. Decreases in organic matter and NDF digestibility were attributed to the higher indigestible NDF concentration of barley silage compared with that of grass silage and to the smaller pool size of dNDF in the rumen.

Electron-spin-resonance instability in two-dimensional atomic hydrogen gas

We study by electron-spin-resonance spin-polarized atomic hydrogen adsorbed on the surface of superfluid helium at temperatures T(S) from 50 to 110 mK. The average dipolar field in this 2D system shifts the electron-spin-resonance peak of the adsorbed atoms relative to that of bulk atoms. The shift is directly proportional to surface density. The role of longitudinal magnetization relaxation is played by particle exchange between the 2D and the 3D phases, which diminishes exponentially with decreasing T(S). Therefore at T(S) less, similar 80 mK an excitation field of 0.1 mG disturbs the equilibrium surface density and leads to a magnetization instability observed as sawtooth shaped resonance lines.

Digestive processes of dairy cows fed silages harvested at four stages of grass maturity

The objective of this experiment was to quantify ruminal digestive processes that could help to identify factors limiting DMI when silages differing in grass maturity were fed to dairy cows. Four silages were harvested at 1-wk intervals from a primary growth of a timothy-meadow fescue sward, resulting in feeds with digestible OM content in DM (D-value) of 739, 730, 707, and 639 g/kg in the order of succeeding harvest date. Four ruminally cannulated dairy cows were given ad libitum access to these silages supplemented with 7 kg concentrate per day in a 4 x 4 Latin square design. Rumen function was clearly affected by decreasing digestibility of silage fed. Passage rate of digestible NDF (DNDF) and indigestible NDF (INDF) increased, but it could not prevent the accumulation of DM, NDF, DNDF, and INDF into the rumen when silages of progressing grass maturity were fed. The greatest proportional increases in rumen pool were found in INDF and in medium particles (separated by wet sieving and measuring 315 to 2,500 microm). The passage of medium INDF particles decreased (P < 0.01) linearly (from 0.0365/h to 0.0281/h) with increasing maturity of grass ensiled, and it was slower than passage of small (80 to 315 microm) particles (on average 0.0524/h). Particle size reduction of large INDF particles to medium INDF particles was slower (P < 0.001) in the early cut silages (0.0216/h to 0.0484/h) but reduction of medium INDF particles to small INDF particles was faster (P < 0.001) in early cut silages (0.0436 to 0.0305). Passage of medium size particles and(or) rate of medium particle breakdown to small particles were potential intake-constraining properties of low digestibility forages, whereas large particle reduction to medium particles seemed not to be limiting. The increased feed intake of the early-cut silages was accompanied by decreased rumen fill, suggesting that rumen fill was not at least solely responsible for feed intake control.