Impact of patient selection on performance of an early rule-out pathway for myocardial infarction: from research to the real world

Background

Early rule-out pathways for myocardial infarction using high-sensitivity cardiac troponin are widely recommended in the assessment of patients with suspected acute coronary syndrome. Although developed in selected patients participating in research studies, these pathways are applied more widely in clinical practice where the diagnostic performance and effectiveness of these pathways may differ.

Purpose

To evaluate the performance of an early rule-out pathway for myocardial infarction using high-sensitivity cardiac troponin in selected and consecutive unselected patients with suspected acute coronary syndrome.

Methods

Presentation and serial high-sensitivity cardiac troponin I concentrations were measured in two cohorts of patients with suspected acute coronary syndrome presenting to the Emergency Departments across three acute care hospitals in Scotland. In the unselected cohort, electronic health record data were collected on consecutive patients in whom the usual care clinician measured cardiac troponin for suspected acute coronary syndrome. In the selected cohort, patients with suspected acute coronary syndrome were approached between 8am and 8pm by research staff and written informed consent obtained. In both cohorts, the performance of the High-STEACS early rule-out pathway was evaluated for an adjudicated diagnosis of myocardial infarction (type 1, type 4b or type 4c) during the index hospital admission.

Results

The unselected and selected patient cohorts comprised of 1,242 (median age 60 [interquartile range 47–75] years, 46% women) and 1,695 (median age 61 [52–73] years, 40% women) patients respectively. Myocardial infarction was diagnosed in 6% (74/1,242) and 14% (232/1,695) of patients in the unselected and selected patient cohorts respectively. More patients had myocardial infarction ruled-out in the unselected (74% [828/1,112] versus 66% [1,102/1,678]; P<0.001), with similar negative predictive value (99.9% [95% CI 99.7%-100%] versus 99.7% [95% CI 99.4%-99.0%) and sensitivity (99.3% [95% CI 97.4%-100%] versus 98.9% [95% CI 97.6%-99.9%]; Figure 1). In the selected cohort, more patients had intermediate troponin concentrations requiring serial testing (36% versus 29%) or had myocardial infarction diagnosed (34% versus 26%; P<0.001 for both). In contrast, the positive predictive value for myocardial infarction was lower in unselected patients (26.1% [95% CI 21.2%-31.4%] versus 39.9% [95% CI 35.9%-44.0%]).

Conclusion

The prevalence of myocardial infarction is lower in patients with suspected acute coronary syndrome evaluated in routine practice compared to those selected to participate in a research study. Whilst more patients have myocardial infarction accurately ruled out, the positive-predictive value in those ruled in is lower resulting in more hospital admissions with elevated cardiac troponin due to other conditions.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): British Heart FoundationMedical Research Council

Trajectories of high-sensitivity cardiac troponin I in the two decades before cardiovascular death in Whitehall II

Background

High-sensitivity cardiac troponin may be a promising biomarker that could be used for personalised cardiovascular risk prediction and monitoring in the general population. Temporal changes in high-sensitivity cardiac troponin before cardiovascular death are largely unexplored.

Purpose

Using the longitudinal Whitehall II cohort, we evaluated whether three serial high-sensitivity cardiac troponin I measurements over 15 years improved prediction of cardiovascular death when compared to a single time point at baseline.

Methods

Whitehall II is an ongoing longitudinal observation cohort study of 10,308 civil servants, and we included participants who had at least one cardiac troponin measurement and outcome data available. We constructed time trajectories to evaluate the temporal pattern of cardiac troponin I in those who died from cardiovascular disease as compared to those who did not. Cox regression and joint models were used to investigate the association of cardiac troponin I in relation to cardiovascular death using single time point (at baseline) and repeated measurements (at baseline, 10 and 15 years), respectively. The discriminative ability was assessed by the concordance index.

Results

In total, we included 7,293 individuals (mean age of 58 years [SD 7] at baseline, 29.4% women). Of these, 5,818 (79.8%) and 4,045 (55.5%) individuals had a second and third cardiac troponin I concentration measured, respectively. Cardiovascular death occurred in 281 (3.9%) individuals during a median follow-up of 21.4 [IQR, 15.8 to 21.8] years. In the 21-year trajectories of cardiac troponin I, we observed higher baseline concentrations in those who died due to cardiovascular disease as compared to those who did not (median 5 [IQR, 2 to 9] ng/L versus 3 [IQR, 2 to 5] ng/L respectively, Figure). Cardiac troponin I was an independent predictor of cardiovascular death, and the hazard ratio (HR) derived from the joint model that included serial cardiac troponin measurements was higher than the HR derived from the single time point model (single time point model: adjusted HR 1.53, 95% Confidence Interval [CI] 1.37 to 1.70 per naturally log transformed unit of cardiac troponin I, versus repeated measurements model: adjusted HR 1.79, 95% CI 1.58 to 2.02). The discriminative ability of the cardiac troponin model improved when using repeated measurements (concordance index of unadjusted cardiac troponin models, single time point: 0.668 versus repeated measurements: 0.724).

Conclusions

Our study shows that cardiac troponin I trajectories were persistently higher among individuals who died from cardiovascular disease. Cardiac troponin I is a strong independent predictor of cardiovascular death, and incorporating repeated measurements of cardiac troponin improves cardiovascular risk prediction in the general population.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Cardiac troponin I measurements and analysis were supported by were supported by Siemens Healthineers. The study was supported by Health Data Research UK which receives its funding from HDR UK Ltd (HDR-5012) funded by the UK Medical Research Council, Engineering and Physical Sciences Research Council, Economic and Social Research Council, Department of Health and Social Care (England), Chief Scientist Office of the Scottish Government Health and Social Care Directorates, Health and Social Care Research and Development Division (Welsh Government), Public Health Agency (Northern Ireland), British Heart Foundation and the Wellcome Trust. NLM is supported by the British Heart Foundation through a Senior Clinical Research Fellowship (FS/16/14/32023), Programme Grant (RG/20/10/34966) and a Research Excellence Award (RE/18/5/34216). The funders had no role in the study and the decision to submit this work to be considered for publication.

Physiological circadian rhythm of cardiac myosin-binding protein C (cMyC) and cardiac troponin

Introduction

Cardiac myosin-binding protein C (cMyC) is a novel protein biomarker of myocardial injury, with a promising role in the triage and risk stratification of patients with cardiac disease. Understanding the physiological diurnal oscillation of cMyC and cardiac troponin is important for the interpretation of single and serial measurements within the biomarker-assisted triage and risk stratification algorithms.

Purpose

In this study, we aim to assess and compare the physiological diurnal oscillation of cMyC and cardiac troponin cTnT and cTnI.

Method

Twenty-six consecutive hourly blood samples were drawn between 08.30 am and 09.30 am (+1 day) from normotensive 24 individuals without a recent history of acute myocardial infarction, for the measurement of cMyC, cardiac troponin T (Roche hs-cTnT) and I (Abbott hs-cTnI).

Fitted cosinor sine regression model (with R, version 3.6.1) was used to assess the presence and significance of circadian oscillation of the biomarker, and to estimate the respective amplitude and acrophase (the time of peak activity).

Amplitude and acrophase were compared across the biomarkers that exhibited significant circadian rhythm.

Results

Mean age was 72±7. 79% of participants (n=19) were men. All participants were free from renal disease.

On population-mean cosinor analysis, hs-cTnI exhibited random diurnal oscillation, whereas significant circadian rhythm was detected for cMyC and hs-cTnT (p=0.015 and <0.001, respectively) (Figure 1).

The circadian rhythm of cMyC is characterised by gradually increasing concentrations from early afternoon until early morning (acrophase 03:03 am, 95% CI 01:54–04:26 am) compared to hs-cTnT concentrations which exhibits delayed increase and a later peak (acrophase, 08:01, 95% CI 07:10–08:51 am), p=0.028 for acrophase difference (Figure 1).

Diurnal rhythm remained significant after correction for possible posture-induced changes in plasma volume.

To allow direct comparison between amplitudes, the measurements of cMyC and hs-TnT were normalised to the respective 08:30 am value, re-fitted cosinor model did not show significant difference between the amplitudes (amplitude ng/L, 0.12, 95% CI 0.07–0.15 vs 0.11, 95% CI 0.08–0.12, for normalised cMyC vs hs-cTnT, respectively; p=0.67).

Conclusion

Significant circadian rhythm exists for cMyC and hs-cTnT, with 5-hours phase difference between the two biomarkers (cMyC ahead of hs-cTnT). The cause of this rhythmic variation is unknown, but the phase difference is consistent with the previously described disparity in the release of cMyC and cTnT after iatrogenic myocardial injury, raising the possibility of an underlying diurnal variation in myocardial vulnerability. Studies are required to assess the impact of this physiological phenomenon on the performance of the biomarkers within unadjused diagnostic algorithms

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart FoundationStichting de Weijerhorst

Role of sFlt-1 and PlGF in the screening of small-for-gestational age neonates during pregnancy: A systematic review

Background

Fetal growth restriction, i.e. the restriction of genetically predetermined growth potential due to placental dysfunction, is a major cause of neonatal morbidity and mortality. The consequences of inadequate fetal growth can be life-long, but the risks can be reduced substantially if the condition is identified prenatally. Currently, screening strategies are based on ultrasound detection of a small-for-gestational age fetus and do not take into account the underlying vascular pathology in the placenta. Measurement of maternal circulating angiogenic biomarkers placental growth factor, sFlt-1 (soluble FMS-like tyrosine kinase-1) are increasingly used in studies on fetal growth restriction as they reflect the pathophysiological process in the placenta. However, interpretation of the role of angiogenic biomarkers in prediction of fetal growth restriction is hampered by the varying design, population, timing, assay technique and cut-off values used in these studies.

Methods

We conducted a systematic-review in PubMed (MEDLINE), EMBASE (Ovid) and Cochrane to explore the predictive performance of maternal concentrations of placental growth factor, sFlt-1 and their ratio for fetal growth restriction and small-for-gestational age, at different gestational ages, and describe the longitudinal changes in biomarker concentrations and optimal discriminatory cut-off values.

Results

We included 26 studies with 2514 cases with small-for-gestational age, 27 cases of fetal growth restriction, 582 cases mixed small-for-gestational age/fetal growth restriction and 29,374 reference. The largest mean differences for the two biomarkers and their ratio were found after 26 weeks of gestational age and not in the first trimester. The ROC-AUC varied between 0.60 and 0.89 with sensitivity and specificity matching the different cut-off values or a preset false-positive rate of 10%.

Conclusions

Most of the studies did not make a distinction between small-for-gestational age and fetal growth restriction, and therefore the small-for-gestational age group consists of fetuses with growth restriction and fetuses that are constitutionally normal. The biomarkers can be a valuable screening tool for small-for-gestational age pregnancies, but unfortunately, there is not yet a clear cut-off value to use for screening. More research is needed to see if these biomarkers are sufficiently able to differentiate growth restriction on their own and how these biomarkers in combination with other relevant clinical and ultrasound parameters can be used in clinical routine diagnostics.

Effect of the colloids gelatin and HES 130/0.4 on blood coagulation in cardiac surgery patients: a randomized controlled trial

Objective:

The choice of the prime solution for cardiopulmonary bypass can play an important role in limiting the effect on blood coagulation, but it is still unclear what the effect of colloids on blood coagulation is. The aim of this study was to investigate the effect of synthetic colloids on blood loss and blood coagulation in patients after on-pump coronary artery bypass graft (CABG) procedures.

Methods:

Sixty elective, on-pump CABG patients were randomly assigned to receive the prime solutions lactated Ringer’s solution combined with hydroxyethyl starch 130/0.4 (HES, 6% Volulyte, Fresenius Kabi Nederland BV, Zeist, the Netherlands) (HES group) or gelatin (Gelofusin®, B Braun Melsung AG, Melsungen, Germany) (Gelo group). Blood loss was assessed using post-operative chest tube output; secondary endpoints were number of blood component transfusions, routine coagulation test values and rotation thromboelastometry values (Rotem® delta, Pentapharm GmbH, Munich, Germany).

Results:

Total post-operative chest tube output was 500 ± 420 ml in the HES group versus 465 ± 390 ml in the Gelo group ( p = 0.48). No significant differences were observed in any of the routine coagulation tests values, thromboelastometry parameters or number of blood component transfusions between the groups.

Conclusions:

In this randomized, controlled trial of adults after on-pump CABG procedures, there was no significant difference in blood loss or blood coagulation between the HES group and the Gelo group.