Kimmo Porthan

University of Helsinki, Helsinki, Uusimaa, Finland

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Publications (31)196.86 Total impact

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    ABSTRACT: Background: Heterogeneity of depolarization and repolarization underlies the development of lethal arrhythmias. Objective: We investigated whether quantification of spatial depolarization and repolarization heterogeneity identifies individuals at risk for sudden cardiac death (SCD). Methods: Spatial R-, J-, and T-wave heterogeneities (RWH, JWH, and TWH, respectively) were automatically analyzed with second central moment technique from standard digital 12-lead ECGs in 5,618 adults (46% men; age [mean±SEM] 50.9±0.2 years) who took part in Health 2000 Survey, an epidemiological survey representative of the entire Finnish adult population. Results: During follow-up of 7.7±0.2 years, a total of 72 SCDs occurred (1.3%), with an average yearly incidence rate of 0.17%. Increased RWH, JWH, and TWH in left precordial leads (V4-V6) were univariately associated with SCD (P<0.001, each). When adjusted with standard clinical risk markers, JWH and TWH remained independent predictors of SCD. Increased TWH (≥102 µV) was associated with a 1.7-fold adjusted relative risk (95% confidence interval [CI]: 1.0-2.9; P=0.048) and increased JWH (≥123µV) with a 2.0-fold adjusted relative risk for SCD (95% CI: 1.2-3.3; P=0.006). When both TWH and JWH were above threshold, the adjusted relative risk for SCD was 2.9-fold (95% CI: 1.5-5.7; P=0.002). When RWH (≥470µV), JWH, and TWH were all above threshold, the risk for SCD was 3.2-fold (95% CI: 1.4-7.1; P=0.009). Conclusion: Second central moment analysis of standard resting 12-lead ECG morphology provides an ultra-rapid means for automated measurement of spatial R-, J-, and T-wave heterogeneity, enabling analysis of high subject volumes and screening for SCD risk in the general population.
    No preview · Article · Nov 2015 · Heart rhythm: the official journal of the Heart Rhythm Society
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    ABSTRACT: The identification of patients at risk for sudden cardiac death (SCD) is still a significant challenge to clinicians and scientists. Noninvasive identification of high-risk patients has been of great interest, and several ventricular depolarization and repolarization abnormalities in the standard 12-lead electrocardiogram (ECG) have been associated with increased vulnerability to lethal ventricular arrhythmias. Several benign and pathological conditions can induce changes in repolarization detected as alteration of the ST segment or T wave. Changes in the ST segment and T waves can be early markers of an underlying cardiovascular disease, and even minor ST-T abnormalities have predicted reduced survival and increased risk of SCD in the adult population. In this review, we will discuss the current knowledge of the SCD risk with standard 12-lead ECG T wave abnormalities in the general population, and possible T wave changes in various cardiac conditions predisposing to SCD.
    No preview · Article · Sep 2015 · Annals of Noninvasive Electrocardiology
  • Article: PP.04.06
    T. Niiranen · K. Porthan · I. Kantola · A. Jula
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    ABSTRACT: Objective: Left ventricular hypertrophy (LVH) is a strong risk factor for cardiovascular events. ECG is the most widely used method for LVH detection. Despite the abundance of ECG LVH criteria, their prognostic values have been compared in only a few studies, and little has been known about how gender modifies the prognostic value LVH. We assessed the relationship between ECG LVH and incident cardiovascular events in the general population. Design and method: Several ECG LVH criteria were measured in 3059 women and 2456 men participating in the Health 2000 Study, a national general population survey. Association between ECG LVH and cardiovascular events were analyzed with Cox proportional hazards models adjusted for age, body mass index, systolic blood pressure, current smoking, use of antihypertensive medication, history of hypercholesterolemia and history of diabetes mellitus. We used a composite end point that included cardiovascular mortality, nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, percutaneous coronary intervention, and coronary artery bypass surgery. Results: ECG LVH was more prevalent in women than in men when measured with Cornell-based criteria but less prevalent or non-different when measured with other criteria. 334 women suffered a cardiovascular event during a follow-up of 10.6 +/- 2.3 years while 328 men had a cardiovascular event during a follow-up of 10.4 +/- 2.6 years. The association between ECG LVH and events showed higher hazard ratios for women than in men (Table). Gender x LVH interaction terms were statistically significant in part of the LVH criteria. In adjusted Cox models, Sokolow-Lyon voltage performed the best (Table). The composite of Sokolow-Lyon voltage and Cornell voltage was statistically significantly associated with events in women (P = 0.001) and in men (P = 0.02). Copyright
    No preview · Article · Jun 2015 · Journal of Hypertension
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    ABSTRACT: Left ventricular hypertrophy (LVH) is a strong risk factor for cardiovascular events. ECG is the most widely used method for LVH detection. Despite the abundance of ECG LVH criteria, their prognostic values have been compared in only a few studies, and little has been known about how sex modifies the prognostic value of LVH. We assessed the relationship between ECG LVH and incident cardiovascular events in the general population. Several ECG LVH criteria were measured in 3059 women and 2456 men participating in the Health 2000 Study - a national general population survey. Association between ECG LVH and cardiovascular events were analyzed with Cox proportional-hazards models. ECG LVH was more prevalent in women than in men when measured with Cornell-based criteria, but less prevalent or nondifferent when measured with other criteria. The association between ECG LVH and events showed higher hazard ratios for women than in men. Sex × LVH interaction terms were statistically significant in part of the LVH criteria. In adjusted Cox models, Sokolow-Lyon voltage performed the best. The composite of Sokolow-Lyon voltage and Cornell voltage was statistically significantly associated with events in both sexes. Sex affects both the prevalence rates and prognostic values of ECG LVH criteria in the general population, while showing higher prognostic value of ECG LVH in women than in men. For clinical use, the composite of the Sokolow-Lyon voltage and the Cornell voltage seems to be a good option.
    No preview · Article · Mar 2015 · Journal of Hypertension
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    ABSTRACT: The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD.
    Full-text · Article · Dec 2014 · Nature Genetics
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    ABSTRACT: Background Early repolarization (ER) is defined as an elevation of the QRS-ST junction in at least two inferior or lateral leads of the standard 12-lead electrocardiogram (ECG). Our purpose was to create an algorithm for the automated detection and classification of ER.MethodsA total of 6,047 electrocardiograms were manually graded for ER by two experienced readers. The automated detection of ER was based on quantification of the characteristic slurring or notching in ER-positive leads. The ER detection algorithm was tested and its results were compared with manual grading, which served as the reference.ResultsReaders graded 183 ECGs (3.0%) as ER positive, of which the algorithm detected 176 recordings, resulting in sensitivity of 96.2%. Of the 5,864 ER-negative recordings, the algorithm classified 5,281 as negative, resulting in 90.1% specificity. Positive and negative predictive values for the algorithm were 23.2% and 99.9%, respectively, and its accuracy was 90.2%. Inferior ER was correctly detected in 84.6% and lateral ER in 98.6% of the cases.Conclusions As the automatic algorithm has high sensitivity, it could be used as a prescreening tool for ER; only the electrocardiograms graded positive by the algorithm would be reviewed manually. This would reduce the need for manual labor by 90%.
    No preview · Article · Nov 2014 · Annals of Noninvasive Electrocardiology
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    ABSTRACT: Background: QRS transition zone is related to the electrical axis of the heart in the horizontal plane and is easily determined from the precordial leads of a standard 12-lead ECG. However, whether delayed QRS transition, or clockwise rotation of the heart, carries prognostic implications and predicts sudden cardiac death (SCD) is unclear. Objective: The purpose of this study was to study whether delayed transition is associated with mortality and SCD. Methods: We evaluated 12-lead ECGs of 10,815 Finnish middle-aged subjects from the general population (52% men, mean age 44 ± 8.5 years) and followed them for 30 ± 11 years. Main end-points were mortality and SCD. Results: Delayed QRS transition at lead V4 or later occurred in 1770 subjects (16.4%) and markedly delayed transition at lead V5 or later in 146 subjects (1.3%). Delayed transition zone was associated with older age, male gender, higher body mass index, hypertension, baseline cardiovascular disease, leftward shift of the frontal QRS axis, wider QRS-T angle, and ECG left ventricular hypertrophy. After adjusting for several clinical and ECG variables, delayed transition was associated with overall mortality (hazard ratio [HR] 1.15, 95% confidence interval [CI] 1.07-1.22, P < .001) and SCD (HR 1.23, 95% CI 1.03-1.47, P = .029). Markedly delayed transition at V5 or later predicted significantly SCD (HR 1.89, 95% CI 1.18-3.03, P = .008) and all-cause mortality (HR 1.30, 95% CI 1.07-1.58, P = .01). However, further adjustments for repolarization abnormalities attenuated this effect. Conclusion: Delayed QRS transition in the precordial leads of an ECG seems to be a novel ECG risk marker for SCD. In particular, markedly delayed transition was associated with significantly increased risk of SCD, independent of confounding factors.
    No preview · Article · Aug 2014 · Heart rhythm: the official journal of the Heart Rhythm Society
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    ABSTRACT: BACKGROUND Early repolarization (ER) in the inferior/lateral leads predicts mortality, but whether ER is a specific sign of increased risk for arrhythmic events is not known. OBJECTIVE The purpose of this study was to study the association of ER and arrhythmic events and nonarrhythmic morbidity and mortality. METHODS We assessed the prognostic significance of ER in a community-based general population of 10,846 middle-aged subjects (mean age 44 8 years). The end-points were sustained ventricular tachycardia or resuscitated ventricular fibrillation (VT-VF), arrhythmic death, nonarrhythmic cardiac death, new-onset atrial fibrillation (AF), hospitalization for congestive heart failure, or coronary artery disease during mean follow-up of 30 11 years. ER was defined as >0.1-mV elevation of 3 point in either inferior or lateral leads. RESULTS After including all risk factors of cardiac mortality and morbidity in Cox regression analysis, inferior ER (prevalence 3.5%) predicted VF-VT events (n = 108 [1.0%]) with a hazard ratio (HR) of 2,2 (95% confidence interval [CI] 1.1-4.5, P =.03) but not nonarrhythmic cardiac death (n = 1235 [12.2%]), AF (n = 1659 [15.2%]), congestive heart failure (n = 1752 [16.1%]), or coronary artery disease (n = 3592 [32.9%]) (P = NS for all). Inferior ER predicted arrhythmic death in cases without other QRS complex abnormalities (multivariate HR 1.68, 95 % CI 1.10-2.58, P =.02) but not in those with ER and other coexisting abnormalities in QRS morphology (HR 1.30, 95% CI 0.86-1.96, P =.22). CONCLUSION ER in the inferior leads, especially in cases without other QRS complex abnormalities, predicts the occurrence of VT-VF but not nonarrhythmic cardiac events, suggesting that ER is a specific sign of increased vulnerability to ventricular tachyarrhythmias.
    No preview · Article · May 2014 · Heart rhythm: the official journal of the Heart Rhythm Society

  • No preview · Article · Feb 2014 · Journal of Emergency Medicine
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    ABSTRACT: Background Early repolarization (ER) in the inferior/lateral leads predicts mortality, but it is not known whether ER is a specific sign of increased risk for arrhythmic events. Objectives We studied the association of ER and arrhythmic events and non-arrhythmic morbidity and mortality. Methods We assessed the prognostic significance of ER in a community-based general population of 10,846 middle-aged subjects (mean age 44±8 years). The endpoints were sustained ventricular tachycardia or resuscitated ventricular fibrillation (VT-VF), arrhythmic death, non-arrhythmic cardiac death, new onset atrial fibrillation (AF), hospitalization for congestive heart failure (CHF) or coronary artery disease (CAD) during a mean follow-up of 30±11 years. ER was defined as ≥0.1 mV elevation of J-point in either inferior or lateral leads. Results After including all risk factors of cardiac mortality and morbidity in Cox regression analysis, inferior ER (prevalence 3.5%) predicted VF-VT events (n=108, 1.0%) with a hazard ratio (HR) of 2.2 (95% CI; 1.1-4.5, p=0.03), but not the non-arrhythmic cardiac death (n=1235, 12.2%), AF (n=1659,15.2%), CHF (n=1752, 16.1%) or CAD (n=3592, 32.9%) (NS for all). Inferior ER predicted arrhythmic death in cases without other QRS complex abnormalities (multivariate HR 1.68, 95 % CI; 1.10-2.58, p=0.02) but not in those with ER and other co-existing abnormalities in the QRS morphology (HR 1.30, 95% CI; 0.86-1.96, p=0.22) Conclusions ER in the inferior leads, especially in cases without other QRS complex abnormalities, predicts the occurrence of VT-VF but not non-arrhythmic cardiac events, suggesting that ER is a specific sign of increased vulnerability to ventricular tachyarrhythmias.
    No preview · Article · Jan 2014
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    ABSTRACT: -Previous population studies have found an association between electrocardiographic (ECG) T-wave morphology parameters and cardiovascular mortality but their relationship to sudden cardiac death (SCD) is not clear. To our knowledge, there are no follow-up studies assessing the association between ECG T-wave peak to T-wave end interval (TPE) and SCD. We assessed the predictive value of ECG T-wave morphology parameters and TPE for SCD in an adult general population sample. -A total of four T-wave morphology parameters (principal component analysis ratio, T-wave morphology dispersion, total cosine R-to-T, T-wave residuum) as well as TPE were measured from digital standard 12-lead ECGs in 5,618 adults (46% men; mean age 50.9±12.5 years) participating in the Finnish population-based Health 2000 Study. After a mean follow-up time of 7.7±1.4 years, 72 SCDs had occurred. In univariable analyses, all T-wave morphology parameters were associated with an increased SCD risk. In multivariable Cox models, T-wave morphology dispersion and total cosine R-to-T remained as predictors of SCD, with T-wave morphology dispersion showing the highest SCD risk (hazard ratio of 1.4 [95% confidence interval 1.1-1.7, P=0.001] per 1-standard deviation increase in the loge TMD). In contrast, TPE was not associated with SCD in univariable or multivariable analyses. -ECG T-wave morphology parameters describing the three-dimensional shape of the T wave stratify SCD risk in the general population but we did not find an association between TPE and SCD.
    Preview · Article · Jul 2013 · Circulation Arrhythmia and Electrophysiology

  • No preview · Article · Jul 2013 · Journal of the American College of Cardiology
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    ABSTRACT: Variability in response to drug use is common and heritable, suggesting that genome-wide pharmacogenomics studies may help explain the 'missing heritability' of complex traits. Here, we describe four independent analyses in 33 781 participants of European ancestry from 10 cohorts that were designed to identify genetic variants modifying the effects of drugs on QT interval duration (QT). Each analysis cross-sectionally examined four therapeutic classes: thiazide diuretics (prevalence of use=13.0%), tri/tetracyclic antidepressants (2.6%), sulfonylurea hypoglycemic agents (2.9%) and QT-prolonging drugs as classified by the University of Arizona Center for Education and Research on Therapeutics (4.4%). Drug-gene interactions were estimated using covariable-adjusted linear regression and results were combined with fixed-effects meta-analysis. Although drug-single-nucleotide polymorphism (SNP) interactions were biologically plausible and variables were well-measured, findings from the four cross-sectional meta-analyses were null (Pinteraction>5.0 × 10-8). Simulations suggested that additional efforts, including longitudinal modeling to increase statistical power, are likely needed to identify potentially important pharmacogenomic effects.The Pharmacogenomics Journal advance online publication, 5 March 2013; doi:10.1038/tpj.2013.4.
    Full-text · Article · Mar 2013 · The Pharmacogenomics Journal
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    Full-text · Article · Oct 2012 · Annals of Emergency Medicine
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    ABSTRACT: The early repolarization pattern (ERP) is common and associated with risk of sudden cardiac death. ERP is heritable, and mutations have been described in syndromatic cases. To conduct a meta-analysis of genome-wide association studies to identify common genetic variants influencing ERP. We ascertained ERP on the basis of electrocardiograms in 3 large community-based cohorts from Europe and the United States: the Framingham Heart Study, the Health 2000 Study, and the KORA F4 Study. We analyzed genome-wide association studies in participants with and without ERP by logistic regression assuming an additive genetic model and meta-analyzed individual cohort results. We then sought to strengthen support for findings that reached P ≤ 1 × 10(-5) in independent individuals by direct genotyping or in-silico analysis of genome-wide data. We meta-analyzed the results from both stages. Of 7482 individuals in the discovery stage, 452 showed ERP (ERP positive: mean age 46.9 ± 8.9 years, 30.3% women; ERP negative: 47.5 ± 9.4 years, 54.2% women). After meta-analysis, 8 single nucleotide polymorphisms reached P ≤ 1 × 10(-5): The most significant finding was intergenic rs11653989 (odds ratio 0.47; 95% confidence interval 0.36-0.61; P = 6.9 × 10(-9)). The most biologically relevant finding was intronic to KCND3: rs17029069 (odds ratio 1.46; 95% confidence interval 1.25-1.69; P = 8.5 × 10(-7)). In the replication step (7151 individuals), none of the 8 variants replicated, and combined meta-analysis results failed to reach genome-wide significance. In a genome-wide association study, we were not able to reliably identify genetic variants predisposing to ERP, presumably due to insufficient statistical power and phenotype heterogeneity. The reported heritability of ERP warrants continued investigation in larger well-phenotyped populations.
    No preview · Article · Jun 2012 · Heart rhythm: the official journal of the Heart Rhythm Society
  • Article: Reply.
    T Vainionpää · K Peräjoki · K Porthan · M Kuisma

    No preview · Article · Jun 2012 · Acta Anaesthesiologica Scandinavica
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    ABSTRACT: T-peak to T-end (TPE) interval on the electrocardiogram is a measure of myocardial dispersion of repolarization and is associated with an increased risk of ventricular arrhythmias. The genetic factors affecting the TPE interval are largely unknown. To identify common genetic variants that affect the duration of the TPE interval in the general population. We performed a genome-wide association study on 1870 individuals of Finnish origin participating in the Health 2000 Study. The TPE interval was measured from T-peak to T-wave end in leads II, V(2), and V(5) on resting electrocardiograms, and the mean of these TPE intervals was adjusted for age, sex, and Cornell voltage-duration product. We sought replication for a genome-wide significant result in the 3745 subjects from the Framingham Heart Study. We identified a locus on 17q24 that was associated with the TPE interval. The minor allele of the common variant rs7219669 was associated with a 1.8-ms shortening of the TPE interval (P = 1.1 × 10(-10)). The association was replicated in the Framingham Heart Study (-1.5 ms; P = 1.3 × 10(-4)). The overall effect estimate of rs7219669 in the 2 studies was -1.7 ms (P = 5.7 × 10(-14)). The common variant rs7219669 maps downstream of the KCNJ2 gene, in which rare mutations cause congenital long and short QT syndromes. The common variant rs7219669 is associated with the TPE interval and is thus a candidate to modify repolarization-related arrhythmia susceptibility in individuals carrying the major allele of this polymorphism.
    No preview · Article · Feb 2012 · Heart rhythm: the official journal of the Heart Rhythm Society
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    ABSTRACT: Various models for organising tactical emergency medicine support (TEMS) in law enforcement operations exist. In Helsinki, TEMS is organised as an integral part of emergency medical service (EMS) and applied in hostage, siege, bomb threat and crowd control situations and in other tactical situations after police request. Our aim was to analyse TEMS operations, patient profile, and the level of on-site care provided. We conducted a retrospective cohort study of TEMS operations in Helsinki from 2004 to 2009. Data were retrieved from EMS, hospital and dispatching centre files and from TEMS reports. One hundred twenty TEMS operations were analysed. Median time from dispatching to arrival on scene was 10 min [Interquartile Range (IQR) 7-14]. Median duration of operations was 41 min (IQR 19-63). Standby was the only activity in 72 operations, four patients were dead on arrival, 16 requests were called off en route and patient examination or care was needed in 28 operations. Twenty-eight patients (records retrieved) were alive on arrival and were classified as trauma (n = 12) or medical (n = 16). Of traumas, two sustained a gunshot wound, one sustained a penetrating abdominal wound, three sustained medium severity injuries and nine sustained minor injuries. There was neither on-scene nor in-hospital mortality among patients who were alive on arrival. The level of on-site care performed was basic life support in all cases. The results showed that TEMS integrated to daily EMS services including safe zone working only was a feasible, rapid and efficient way to provide medical support to law enforcement operations.
    Full-text · Article · Oct 2011 · Acta Anaesthesiologica Scandinavica
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    Full-text · Article · Oct 2011 · Journal of the American College of Cardiology
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    ABSTRACT: Although sudden cardiac death (SCD) is heritable, its genetic underpinnings are poorly characterized. The QT interval appears to have a graded relationship to SCD, and 35% to 45% of its variation is heritable. We examined the relationship among recently reported common genetic variants, QT interval, and SCD. We genotyped 15 common (minor allele frequency >1%) candidate single nucleotide polymorphisms (SNPs), based on association with the QT interval in prior studies, in individuals in 2 cohort studies (Health 2000, n = 6597; Mini-Finland, n = 801). After exclusions, we identified 116 incident SCDs from the remaining sample (n = 6808). We constructed a QT genotype score (QT(score)) using the allele copy number and previously reported effect estimates for each SNP. Cox proportional hazards models adjusting for age, sex, and geographical area were used for time to SCD analyses. The QT(score) was a continuous independent predictor of the heart rate-corrected QT interval (P<10(-107)). Comparing the top with the bottom quintile of QT(score), there was a 15.6-ms higher group mean QT interval (P<10(-84)). A 10-ms increase in the observed QT interval was associated with an increased risk of SCD (hazard ratio, 1.19; 95% confidence interval, 1.07 to 1.32; P = 0.002). There was no linear relationship between QT(score) and SCD risk; although in post hoc secondary analysis there was increased risk in the top compared with the middle QT(score) quintile (hazard ratio, 1.92; 95% confidence interval, 1.05 to 3.58; P = 0.04). Our study strongly replicates the relationship between common genetic variants and the QT interval and confirms the relationship between the QT interval and SCD but does not show evidence for a linear relationship between QT(score) and SCD risk.
    Full-text · Article · Jun 2011 · Circulation Cardiovascular Genetics

Publication Stats

350 Citations
196.86 Total Impact Points

Institutions

  • 2008-2015
    • University of Helsinki
      • • Department of Oral Medicine
      • • Division of Cardiology
      Helsinki, Uusimaa, Finland
  • 2007-2014
    • Helsinki University Central Hospital
      • Division of Cardiology (Heart and Lung Center)
      Helsinki, Southern Finland Province, Finland
  • 2010
    • City of Helsinki
      Helsinki, Southern Finland Province, Finland