Danish study of Non-Invasive testing in Coronary Artery Disease 2 (Dan-NICAD 2): Study design for a controlled study of diagnostic accuracy.

BACKGROUND: Coronary computed tomography angiography (CTA) is the preferred primary diagnostic modality when examining patients with low to intermediate pre-test probability of coronary artery disease (CAD). Only 20-30% of these have potentially obstructive CAD. Because of the relatively poor positive predictive value of coronary CTA, unnecessary invasive coronary angiographies (ICAs) are conducted with the costs and risks associated with the procedure. Hence, an optimized diagnostic CAD algorithm may reduce the numbers of ICAs not followed by revascularization. The Dan-NICAD 2 study has 3 equivalent main aims: (1) To examine the diagnostic precision of a sound-based diagnostic algorithm, The CADScor®System (Acarix A/S, Denmark), in patients with a low to intermediate pre-test risk of CAD referred to a primary examination by coronary CTA. We hypothesize that the CADScor®System provides better stratification prior to coronary CTA than clinical risk stratification scores alone. (2) To compare the diagnostic accuracy of 3T cardiac magnetic resonance imaging (3T CMRI), 82rubidium positron emission tomography (82Rb-PET), and CT-derived fractional flow reserve (FFRCT) in patients where obstructive CAD cannot be ruled out by coronary CTA using ICA fractional flow reserve (FFR) as reference standard. (3) To compare the diagnostic performance of quantitative flow ratio (QFR) and ICA-FFR in patients with low to intermediate pre-test probability of CAD using 82Rb-PET as reference standard. METHODS: Dan-NICAD 2 is a prospective, multicenter, cross-sectional study including approximately 2,000 patients with low to intermediate pre-test probability of CAD and without previous history of CAD. Patients are referred to coronary CTA because of symptoms suggestive of CAD, as evaluated by a cardiologist. Patient interviews, sound recordings, and blood samples are obtained in connection with the coronary CTA. If coronary CTA does not rule out obstructive CAD, patients will be examined by 3T CMRI 82Rb-PET, FFRCT, ICA, and FFR. Reference standard is ICA-FFR. Obstructive CAD is defined as an FFR ≤0.80 or as high-grade stenosis (>90% diameter stenosis) by visual assessment. Diagnostic performance will be evaluated as sensitivity, specificity, predictive values, likelihood ratios, calibration, and discrimination. Enrolment started January 2018 and is expected to be completed by June 2020. Patients are followed for 10 years after inclusion. DISCUSSION: The results of the Dan-NICAD 2 study are expected to contribute to the improvement of diagnostic strategies for patients suspected of CAD in 3 different steps: risk stratification prior to coronary CTA, diagnostic strategy after coronary CTA, and invasive wireless QFR analysis as an alternative to ICA-FFR.

Coronary Artery Disease Detected by Low Frequency Heart Sounds.

OBJECTIVES: Previous studies have observed an increase in low frequency diastolic heart sounds in patients with coronary artery disease (CAD). The aim was to develop and validate a diagnostic, computerized acoustic CAD-score based on heart sounds for the non-invasive detection of CAD. METHODS: Prospective study enrolling 463 patients referred for elective coronary angiography. Pre-procedure non-invasive recordings of heart sounds were obtained using a novel acoustic sensor. A CAD-score was defined as the power ratio between the 10-90 Hz frequency spectrum and the 90-300 Hz frequency spectrum of the mid-diastolic heart sound. Quantitative coronary angiography analysis was performed by a blinded core laboratory and patients grouped according to the results: obstructive CAD defined by the presence of at least one ≥ 50% stenosis, non-obstructive CAD as patients with a maximal stenosis in the 25-50% interval and non-CAD as no coronary lesions exceeding 25%. We excluded patients with potential confounders or incomplete data (n = 245). To avoid over-fitting the final cohort of 218 patients was randomly divided into to a training group for development (n = 127) and a validation group (n = 91). RESULTS: In both the training and the validation group the CAD-score was significantly increased in CAD patients compared to non-CAD patients (p < 0.0001). In the validation group the area under the receiver-operating curve was 77% (95% CI 63-91%). Sensitivity was 71% (95% CI 59-82%) and specificity 64% (95% CI 45-83%). CONCLUSION: The acoustic CAD-score is a new, inexpensive, non-invasive method to detect CAD, which may supplement clinical risk stratification and reduce the need for subsequent non-invasive and invasive testing.

Troponin I degradation in serum of patients with acute ischemic stroke.

BACKGROUND: Although troponin is a cornerstone biomarker in the assessment and management of patients with acute coronary syndrome, much remains to be learned about the biology of this widely used biomarker, including its post-release modification. Degradation of troponin following release in patients with acute coronary syndrome has been described; however whether such post-release modification occurs in other non-acute coronary syndrome states remains unknown. The aim of this study was to define troponin degradation in patients with acute ischemic stroke. MATERIALS AND METHODS: Troponin I (cTnI) was measured daily during the first 5 days of admission in 244 patients with acute ischemic stroke. Western blot analysis was performed using anti-cTnI antibodies and compared with serum concentrations of cTnI in seven patients and one patient with myocardial infarction (positive control). RESULTS: Elevated levels of troponin were detected in 25 (10%) patients; in all, both intact cTnI and cTnI degradation products were detected, with up to seven degradation fragments found. Samples with the highest total cTnI levels gave the strongest and most numerous western-blotting bands. All fragments were comparable with the degradation pattern of the positive control in terms of position. CONCLUSIONS: Immunoblotting of blood samples from patients with acute ischemic stroke reveals similar degradation patterns of cTnI as has been described in patients with acute myocardial infarction. The biological ramification and potential clinical impact of this finding bears further scrutiny.

Validation and update of the minimal risk tool in patients suspected of chronic coronary syndrome.

Risk stratification in patients with suspected coronary artery disease (CAD) is important. Recently, the minimal-risk-tool (MRT) was developed to identify individuals with low CAD risk despite symptoms in order to avoid unnecessary testing. We aimed to validate and update the MRT-model in a contemporary cohort. The Dan-NICAD trial cohort, consisting of 1675 consecutive patients referred for coronary computed tomography angiography (CTA), was used to calculate the MRT-score based on the published fitted variable coefficients from the PROMISE and SCOT-HEART trials. Minimal risk was defined as zero calcium score, no coronary atherosclerosis at coronary CTA, and no cardiovascular events in the follow-up period. We tested an updated MRT-model by pooling the fitted variable coefficients from all three trials. A total of 1544 patients fulfilling the inclusion criteria were followed for 3.1 [2.7-3.4] years. In 710 (46%) patients, the criteria for minimal risk were fulfilled. Despite substantial coefficient variation, the MRTs based on the PROMISE, the SCOT-HEART and the updated MRT variables showed similar moderate to high discriminative performance for minimal risk estimation. Although all three models tended to underestimate minimal risk, the updated MRT had the best performance. Using a 75% minimal risk cut-off, the updated MRT showed a sensitivity of 11.6% (95% CI 9.3-14.2%) and specificity of 99.3% (95% CI 98.6-99.8%). An updated MRT model based on three large studies increased calibration compared to the existing MRT models, whereas discrimination was similar despite substantial coefficient variation. The updated MRT might supplement currently recommended pre-test probability models.

Advanced heart sound analysis as a new prognostic marker in stable coronary artery disease.

Aims: Recent technological advances enable diagnosing of obstructive coronary artery disease (CAD) from heart sound analysis with a high negative predictive value. However, the prognostic impact of this approach remains unknown. To investigate the prognostic value of heart sound analysis as two scores, the Acoustic-score and the CAD-score, in patients with suspected CAD which is treated according to standard of care. Methods and results: Consecutive patients with angina symptoms referred for coronary computed tomography angiography (CTA) were enrolled. The Acoustic-score was developed from eight acoustic CAD-related features. This score was combined with risk factors to generate the CAD-score. A cut-off score >20 was pre-specified for both scores to indicate disease. If coronary CTA raised suspicion of obstructive CAD, patients were referred to invasive angiography and revascularized when indicated. Of 1675 enrolled patients, 1464 (87.4%) were included in this substudy. The combined primary endpoint was all-cause mortality and myocardial infarction (n = 26). Follow-up was 3.1 (2.7-3.4) years. Of patients with primary endpoints, the Acoustic-score was >20 in 25 (96%); the CAD-score was >20 in 22 (85%). In an unadjusted Cox analysis of the primary endpoints, the hazard ratio for scores >20 under current standard clinical care was 12.6 (1.7-93.2) for the Acoustic-score and 5.4 (1.9-15.7) for the CAD-score. The CAD-score contained prognostic information even after adjusting for lipid-lowering therapy initiation, stenosis at CTA, and early revascularization. Conclusion: Heart sound analysis seems to carry prognostic information and may improve initial risk stratification of patients with suspected CAD. Clinicaltrialsorg ID: NCT02264717.

Pre-test probability prediction in patients with a low to intermediate probability of coronary artery disease: a prospective study with a fractional flow reserve endpoint.

AIMS: European and North American guidelines currently recommend pre-test probability (PTP) stratification based on simple probability models in patients with suspected coronary artery disease (CAD). However, no unequivocal recommendation has yet been established. We aimed to compare the ability of risk factors and different PTP stratification models to predict haemodynamically obstructive CAD with fractional flow reserve (FFR) as reference in low to intermediate probability patients. METHODS AND RESULTS: We prospectively included 1675 patients with low to intermediate risk who had been referred to coronary computed tomography angiography (CTA). Patients with coronary stenosis were subsequently investigated by invasive coronary angiography (ICA) with FFR measurement if indicated. Discrimination and calibration were assessed for four models: the updated Diamond-Forrester (UDF), the CAD Consortium Basic, the Clinical, and the Clinical + Coronary artery calcium score (CACS). At coronary CTA, 24% of patients were diagnosed with a suspected stenosis and 10% had haemodynamically obstructive CAD at the ICA. Calibration for all CAD Consortium models increased compared with the UDF score. However, all models overestimated the probability of haemodynamically obstructive CAD. Discrimination increased by area under the receiver operating curve from 67% to 86% for UDF vs. CAD Consortium Clinical + CACS. The proportion of low-probability patients (pre-test score < 15%) was for the UDF, CAD Consortium Basic, Clinical, and Clinical + CACS: 14%, 58%, 51%, and 66%, respectively. The corresponding negative predictive values were 97%, 94%, 95%, and 98%, respectively. CONCLUSION: CAD Consortium models improve PTP stratification compared with the UDF score, mainly due to superior calibration in low to intermediate probability patients. Adding the coronary calcium score to the models substantially increases discrimination. CLINICAL TRIALS. GOV IDENTIFIER: NCT02264717.

Diagnostic performance of an acoustic-based system for coronary artery disease risk stratification.

OBJECTIVE: Diagnosing coronary artery disease (CAD) continues to require substantial healthcare resources. Acoustic analysis of transcutaneous heart sounds of cardiac movement and intracoronary turbulence due to obstructive coronary disease could potentially change this. The aim of this study was thus to test the diagnostic accuracy of a new portable acoustic device for detection of CAD. METHODS: We included 1675 patients consecutively with low to intermediate likelihood of CAD who had been referred for cardiac CT angiography. If significant obstruction was suspected in any coronary segment, patients were referred to invasive angiography and fractional flow reserve (FFR) assessment. Heart sound analysis was performed in all patients. A predefined acoustic CAD-score algorithm was evaluated; subsequently, we developed and validated an updated CAD-score algorithm that included both acoustic features and clinical risk factors. Low risk is indicated by a CAD-score value ≤20. RESULTS: Haemodynamically significant CAD assessed from FFR was present in 145 (10.0%) patients. In the entire cohort, the predefined CAD-score had a sensitivity of 63% and a specificity of 44%. In total, 50% had an updated CAD-score value ≤20. At this cut-off, sensitivity was 81% (95% CI 73% to 87%), specificity 53% (95% CI 50% to 56%), positive predictive value 16% (95% CI 13% to 18%) and negative predictive value 96% (95% CI 95% to 98%) for diagnosing haemodynamically significant CAD. CONCLUSION: Sound-based detection of CAD enables risk stratification superior to clinical risk scores. With a negative predictive value of 96%, this new acoustic rule-out system could potentially supplement clinical assessment to guide decisions on the need for further diagnostic investigation. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier NCT02264717; Results.

Danish study of Non-Invasive testing in Coronary Artery Disease (Dan-NICAD): study protocol for a randomised controlled trial.

BACKGROUND: Coronary computed tomography angiography (CCTA) is an established method for ruling out coronary artery disease (CAD). Most patients referred for CCTA do not have CAD and only approximately 20-30 % of patients are subsequently referred to further testing by invasive coronary angiography (ICA) or non-invasive perfusion evaluation due to suspected obstructive CAD. In cases with severe calcifications, a discrepancy between CCTA and ICA often occurs, leading to the well-described, low-diagnostic specificity of CCTA. As ICA is cost consuming and involves a risk of complications, an optimized algorithm would be valuable and could decrease the number of ICAs that do not lead to revascularization. The primary objective of the Dan-NICAD study is to determine the diagnostic accuracy of cardiac magnetic resonance imaging (CMRI) and myocardial perfusion scintigraphy (MPS) as secondary tests after a primary CCTA where CAD could not be ruled out. The secondary objective includes an evaluation of the diagnostic precision of an acoustic technology that analyses the sound of coronary blood flow. It may potentially provide better stratification prior to CCTA than clinical risk stratification scores alone. METHODS/DESIGN: Dan-NICAD is a multi-centre, randomised, cross-sectional trial, which will include approximately 2,000 patients without known CAD, who were referred to CCTA due to a history of symptoms suggestive of CAD and a low-risk to intermediate-risk profile, as evaluated by a cardiologist. Patient interview, sound recordings, and blood samples are obtained in connection with the CCTA. All patients with suspected obstructive CAD by CCTA are randomised to either stress CMRI or stress MPS, followed by ICA with fractional flow reserve (FFR) measurements. Obstructive CAD is defined as an FFR below 0.80 or as high-grade stenosis (>90 % diameter stenosis) by visual assessment. Diagnostic performance is evaluated as sensitivity, specificity, predictive values, likelihood ratios, and C statistics. Enrolment commenced in September 2014 and is expected to be complete in May 2016. DISCUSSION: Dan-NICAD is designed to assess whether a secondary perfusion examination after CCTA could safely reduce the number of ICAs where revascularization is not required. The results are expected to add knowledge about the optimal algorithm for diagnosing CAD. TRIAL REGISTRATION: Clinicaltrials.gov identifier, NCT02264717 . Registered on 26 September 2014.

[Molecular modifications of troponin I and T detected in serum from patients with acute myocardial infarction]. / Molekylaere forandringer af troponin I og T påvist i serum hos patienter med akut myokardieinfarkt.

INTRODUCTION: Cardiac troponin I and T (cTnI and cTnT) are specific biochemical serum markers for acute myocardial infarction (AMI). However, cTnI diagnostic assays are plagued by difficulties, resulting in > 20-fold differences in measured values. These discrepancies may result from the release of the numerous cTnI modification products that are present in ischaemic myocardium. The resolution of these discrepancies requires an investigation of the exact forms of the troponins present in the bloodstream of patients after myocardial injury. MATERIAL AND METHODS: A Westernblot direct serum analysis protocol was developed that allowed us to detect intact cTnI and a spectrum of up to 11 modified products in the serum from patients with AMI. RESULTS: We document both a cTnI degradation pattern and the existence of phosphorylated cTnI in serum. The number and extent of these modifications reflect patterns similar to the time profiles of the routine clinical serum markers of total creatine kinase, creatine kinase-MB, and cTnI (determined by ELISA). Data from in vitro experiments, which were undertaken to study the degradation of human recombinant cTnI and cTnT when spiked in serum, indicate that some modification products present in patient serum existed in the myocardium. DISCUSSION: This pilot study defines, for the first time, what forms of cTnI and cTnT appear in the bloodstream of AMI patients, and it clarifies the lack of standardization between different cTnI diagnostic assays.

Effect of atrial fibrillation on plasma NT-proBNP in chronic heart failure.

BACKGROUND: Brain natriuretic peptides are elevated in patients with systolic heart failure (HF) as well as in patients with atrial fibrillation (AF) and normal left ventricular ejection fraction (LVEF) and are strong predictors of death in HF patients. The aim of our study was to examine the levels of N-terminal pro brain natriuretic peptide (NT-proBNP) in patients with HF and AF versus HF and sinus rhythm (SR) and if NT-proBNP has prognostic influence in patients with AF. METHODS: We included 245 patients (72% men, 70 years) with HF referred to a HF clinic. NT-proBNP was measured at referral (baseline). RESULTS: At baseline, 26% had AF and at follow-up 35% of the surviving patients. Patients with AF were older than patients with SR (p=0.009), but LVEF and NYHA distribution were similar. Median NT-proBNP levels were higher: 2528 vs. 899 pg/ml (p<0.001). NT-proBNP was significantly correlated with AF at baseline (p<0.001), age (p=0.001), P-creatinine (p<0.001) and reduced LVEF (p=0.002). NT-proBNP was an independent predictor of death in patients with AF, adjusted HR 4.0 (95% CI 1.6-10.2) (p=0.003). CONCLUSION: NT-proBNP levels are higher in HF patients with AF than in HF patients with SR and has prognostic value despite the presence of AF.