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Metabolic risk markers and relative survival in patients with aortic stenosis requiring surgery
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Aortic stenosis (AS) is the most common valve disorder requiring surgery in developed countries. The etiology of AS is only partly known.  Identification of new biomarkers in prospective studies could lead to novel insights in the etiology of AS, and possibly lead to improved clinical management. Long term observed survival after aortic valve surgery has improved over the last decades despite an ageing population presenting with more comorbidities. Whether this is reflected in improved relative survival is not known. We evaluated if biomarkers associated prospectively with AS requiring surgery, and if these associations differed between genders, time to surgery and the presence of coronary artery disease (CAD). We also assessed long term observed and relative survival after aortic valve surgery with and without concomitant coronary artery by-pass surgery (CABG).

Methods and results: Study I: We prospectively studied the impact of lipoprotein (a)(Lp[a]) and apolipoproteins (Apo) in subgroups of AS. During a 20-year period, 336 patients with prior participation in large population-based surveys in northern Sweden were operated due to AS plus CABG when indicated. For each case two referents were matched. Data from the baseline survey were collected and included data on cardiovascular risk factors, health history, measurements of anthropometry, blood pressure, blood glucose and blood lipid levels were retrieved. Data from pre- and perioperative assessments were also collected. The presence of CAD was determined from the coronary angiogram. Elevated levels of Lp(a) and an elevated Apo B/Apo A 1 ratio were independently associated with future surgery for AS, but only in patients with concomitant CAD (OR 1.29, 95 % CI 1.07-1.55 and 1.43, 95 % CI 1.16-1.76 respectively). Study II: The same patient cohort as in study I was used. A panel of 92 cardiovascular candidate proteins were analysed with the multiplex proximity extension assay in samples obtained at baseline. Six circulating proteins (growth differentiation factor 15[GDF-15], galectin-4, von Willebrand factor [vWF], interleukin 17 receptor A, transferrin receptor protein 1, and proprotein convertase subtilisin/kexin type 9, [PCSK9]) were associated with future surgery for AS in patients with concurrent CAD (ORs ranged from 1.25 to 1.37 per SD increase in the protein signal). In the validation study with 106 additional cases, the association of all but one, (interleukin 17 receptor A), of these proteins were replicated in patients with AS and concurrent CAD but not in those without concurrent CAD. Study III: In the same patient cohort as in study I and II we evaluated if troponin T (TnT) and C-reactive protein (CRP) associated prospectively with future surgery for AS. TnT was independently associated with surgery for AS in patients both with (OR 1.22, 95 % CI 1.02-1.46) and without concomitant CAD (1.39, 95% CI 1.05-1.84). CRP was not associated with surgery for AS (OR 1.06, 95 % CI 0.92-1.23). Study IV: 4970 patients between 2005 and 2016 from three Swedish heart surgery centres, undergoing aortic valve replacement (AVR) due to either AS or aortic regurgitation in conjunction with CABG when indicated, were followed up. All-cause mortality, as well as both observed and relative survival, was analysed with focus on age, sex, type of valve prosthesis and the impact of concomitant CABG. Median follow-up was 4.7 years (2.3-7.6). 30-day mortality was 2.3 %. Long-term survival with 30-day mortality excluded was 96.6 %, 82.7 %, 57.6 % after 1, 5 and 10 years respectively. Relative survival rates (adjusting for the background mortality in the general Swedish population based on age, sex and year) were 99.6 %, 99.5 % and 90.6 % after 1, 5 and 10 years respectively. Age had a negative influence on observed survival (p<0.001) but was associated with better relative survival (relative mortality rate [RMR] 0.74, 95 % CI 0.71 - 0.77). Women had a lower observed mortality than men (p<0.001) but a lower relative survival (RMR 1.17, 95 % CI 1.02-1.35). Combined surgery (AVR+CABG) was not significantly associated with higher mortality (p=0.43) in a multivariable adjusted analysis. The presence of bicuspid morphology was associated with lower observed mortality compared with tricuspid valve, and a relative survival matching that in the general population.

Conclusion: I. Plasma levels of Lp(a) and the Apo B/Apo A 1 ratio were independently associated with future surgery for AS but only in patients with concomitant CAD. This finding suggests that patients with AS have different phenotypes and may open a new avenue of research on targeted risk factor interventions in this population. II. Five circulating proteins – GDF-15, galectin-4, vWF, transferrin receptor protein 1, and PCSK9 – were associated with the need for aortic valve surgery several years later. The role of these proteins should be investigated in future studies. III. Elevated plasma levels of TnT were independently associated with future surgery for AS, irrespective of the presence of concomitant CAD, which could indicate that the myocardium is subject to mechanical stress already in the subclinical stage of AS. This may be used as a clinical tool for identification of patients with subclinical AS who could benefit from early intervention. Elevated CRP levels did not associate with future AVR. IV. Relative survival following AVR was particularly good in the elderly matching that in the general population underlining the benefits of aortic valve surgery in properly selected patients. Women had decreased relative survival compared to men. This should be explored in future studies. Adding CABG to an AVR procedure was not associated with increased risk. Bicuspid valve morphology was associated with lower observed mortality compared with tricuspid valve morphology, and with a relative survival matching that of the general population.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2019. , p. 85
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2028
Keywords [en]
aortic stenosis, aortic valve surgery, coronary artery disease, prospective cohort study, risk markers, lipoprotein (a), apolipoproteins, proteomics, troponin T, C-reactive protein, relative survival, observed survival
National Category
Cardiac and Cardiovascular Systems
Research subject
Cardiology
Identifiers
URN: urn:nbn:se:umu:diva-159032ISBN: 978-91-7855-051-7 (print)OAI: oai:DiVA.org:umu-159032DiVA, id: diva2:1316216
Public defence
2019-06-14, Sal B, Unod T, 9 tr, Norrlands Universitetssjukhus, 13:00 (English)
Opponent
Supervisors
Available from: 2019-05-24 Created: 2019-05-16 Last updated: 2019-05-24Bibliographically approved
List of papers
1. Lipoprotein(a) and the Apolipoprotein B/A1 Ratio Independently Associate With Surgery for Aortic Stenosis Only in Patients With Concomitant Coronary Artery Disease
Open this publication in new window or tab >>Lipoprotein(a) and the Apolipoprotein B/A1 Ratio Independently Associate With Surgery for Aortic Stenosis Only in Patients With Concomitant Coronary Artery Disease
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2017 (English)In: Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease, ISSN 2047-9980, E-ISSN 2047-9980, Vol. 6, no 12, article id e007160Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Aortic stenosis (AS) has different clinical phenotypes, including AS with or without concomitant coronary artery disease (CAD). It is unknown whether these phenotypes share the same risk factors. In particular, lipoprotein(a) [Lp(a)] and apolipoproteins (Apo) are associated with AS, but it is unknown whether these associations differ among phenotypes. In this prospective analysis we examined the impact of Lp(a) and Apo in subgroups of patients with AS.

METHODS AND RESULTS: We identified 336 patients (mean age at survey 56.7 years, 48% female) who underwent surgery for AS after a median 10.9 years (interquartile range 9.3 years), participants in 1 of 3 large population surveys. For each patient, 2 matched referents were allocated. Lp(a) and Apo were analyzed in the baseline samples. Uni- and multivariable logistic regression analyses were used to estimate risks related to a 1 (ln) standard deviation increase in Lp(a) and the ratio of Apo B to Apo A1 (Apo B/A1 ratio). High levels of Lp(a) predicted surgery for AS in 203 patients with concomitant CAD (odds ratio [95% confidence intervals]) (1.29 [1.07-1.55]), but not in 132 patients without CAD (1.04 [0.83-1.29]) in the fully adjusted model. Similarly, a high Apo B/A1 ratio predicted surgery in patients with concomitant CAD (1.43 [1.16-1.76]) but not in those without CAD (0.87 [0.69-1.10]).

CONCLUSIONS: High levels of Lp(a) and a high Apo B/A1 ratio were associated with surgery for AS in patients with concomitant CAD but not in those with isolated AS. This finding may lead to a new avenue of research for targeted risk factor interventions in this population.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
aortic stenosis, aortic valve surgery, apolipoproteins, lipoprotein(a), prospective cohort study, risk markers
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:umu:diva-143323 (URN)10.1161/JAHA.117.007160 (DOI)000418951100046 ()29246959 (PubMedID)
Available from: 2017-12-20 Created: 2017-12-20 Last updated: 2019-05-21Bibliographically approved
2. Proteomic Biomarkers for Incident Aortic Stenosis Requiring Valvular Replacement
Open this publication in new window or tab >>Proteomic Biomarkers for Incident Aortic Stenosis Requiring Valvular Replacement
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2018 (English)In: Circulation, ISSN 0009-7322, E-ISSN 1524-4539, Vol. 138, no 6Article in journal (Refereed) Published
Abstract [en]

Background: Aortic valve stenosis (AS) is the most common indication for cardiac valve surgery; untreated AS is linked to high mortality. The etiological background of AS is unknown. Previous human studies were typically based on case-control studies. Biomarkers identified in prospective studies could lead to novel mechanistic insights. Methods: Within a large population survey with blood samples obtained at baseline, 334 patients were identified who later underwent surgery for AS (median age [interquartile range], 59.9 [10.4] years at survey and 68.3 [12.7] at surgery; 48% female). For each case, 2 matched referents were allocated. Plasma was analyzed with the multiplex proximity extension assay for screening of 92 cardiovascular candidate proteins. Conditional logistic regression models were used to assess associations between each protein and AS, with correction for multiple testing. A separate set of 106 additional cases with 212 matched referents was used in a validation study. Results: Six proteins (growth differentiation factor 15, galectin-4, von Willebrand factor, interleukin 17 receptor A, transferrin receptor protein 1, and proprotein convertase subtilisin/kexin type 9) were associated with case status in the discovery cohort; odds ratios ranged from 1.25 to 1.37 per SD increase in the protein signal. Adjusting the multivariable models for classical cardiovascular risk factors at baseline yielded similar results. Subanalyses of case-referent triplets (n=133) who showed no visible coronary artery disease at the time of surgery in the index person supported associations between AS and growth differentiation factor 15 (odds ratio, 1.40; 95% confidence interval, 1.10-1.78) and galectin-4 (odds ratio, 1.27; 95% confidence interval, 1.02-1.59), but these associations were attenuated after excluding individuals who donated blood samples within 5 years before surgery. In triplets (n=201), which included index individuals with concurrent coronary artery disease at the time of surgery, all 6 proteins were robustly associated with case status in all sensitivity analyses. In the validation study, the association of all but 1 (interleukin 17 receptor A) of these proteins were replicated in patients with AS with concurrent coronary artery disease but not in patients with AS without coronary artery disease. Conclusions: We provide evidence that 5 proteins were altered years before AS surgery and that the associations seem to be driven by concurrent atherosclerotic disease.

Keywords
aortic stenosis, aortic valve surgery, prospective study, proteomics, risk markers
National Category
Cardiac and Cardiovascular Systems
Research subject
Cardiology
Identifiers
urn:nbn:se:umu:diva-145712 (URN)10.1161/CIRCULATIONAHA.117.030414 (DOI)000440866500011 ()29487139 (PubMedID)
Available from: 2018-04-09 Created: 2018-04-09 Last updated: 2019-05-24Bibliographically approved
3. TroponinT but not C-reactive protein is associated with future surgery for aortic stenosis - a population based nested case-refeent study.
Open this publication in new window or tab >>TroponinT but not C-reactive protein is associated with future surgery for aortic stenosis - a population based nested case-refeent study.
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(English)Manuscript (preprint) (Other academic)
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:umu:diva-159019 (URN)
Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-05-22
4. Results of surgical aortic valve replacement in a Swedish population: relative survival vs. observed mortality
Open this publication in new window or tab >>Results of surgical aortic valve replacement in a Swedish population: relative survival vs. observed mortality
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(English)Manuscript (preprint) (Other academic)
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:umu:diva-159017 (URN)
Available from: 2019-05-16 Created: 2019-05-16 Last updated: 2019-05-24

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