BACKGROUND: Long QT syndrome (LQTS) is associated with potentially fatal arrhythmias. Treatment is very effective, but its diagnosis may be challenging. Importantly, different methods are used to assess the QT interval, which makes its recognition difficult. QT experts advocate manual measurements with the tangent or threshold method. However, differences between these methods and their performance in LQTS diagnosis have not been established. We aimed to assess similarities and differences between these 2 methods for QT interval analysis to aid in accurate QT assessment for LQTS. METHODS: Patients with a confirmed pathogenic variant in KCNQ1(LQT1), KCNH2(LQT2), or SCN5A(LQT3) genes and their family members were included. Genotype-positive patients were identified as LQTS cases and genotype-negative family members as controls. ECGs were analyzed with both methods, providing inter-and intrareader validity and diagnostic accuracy. Cutoff values based on control population's 95th and 99th percentiles, and LQTS-patients' 1st and 5th percentiles were established based on the method to correct for heart rate, age, and sex. RESULTS: We included 1484 individuals from 265 families, aged 33±21 years and 55% females. In the total cohort, QT Tangent was 10.4 ms shorter compared with QT Threshold (95% limits of agreement±20.5 ms, P<0.0001). For all genotypes, QT Tangent was shorter than QT Threshold (P<0.0001), but this was less pronounced in LQT2. Both methods yielded a high interand intrareader validity (intraclass correlation coefficient >0.96), and a high diagnostic accuracy (area under the curve >0.84). Using the current guideline cutoff (QTc interval 480 ms), both methods had similar specificity but yielded a different sensitivity. QTc interval cutoff values of QT Tangent were lower compared with QT Threshold and different depending on the correction for heart rate, age, and sex. CONCLUSION: The QT interval varies depending on the method used for its assessment, yet both methods have a high validity and can both be used in diagnosing LQTS. However, for diagnostic purposes current guideline cutoff values yield different results for these 2 methods and could result in inappropriate reassurance or treatment. Adjusted cutoff values are therefore specified for method, correction formula, age, and sex. In addition, a freely accessible online probability calculator for LQTS (www.QTcalculator.org) has been made available as an aid in the interpretation of the QT interval.

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Introduction Infective endocarditis (IE) is associated with a high in-hospital and long term mortality. Although progress has been made in diagnostic approach and management of IE, morbidity and mortality of IE remain high. In the latest European guidelines, the importance of the multi-modality imaging in diagnosis and follow up of IE is emphasized. Aim The aim was to provide information regarding mortality and adverse events of IE, to determine IE characteristics and to assess current use of imaging in the diagnostic workup of IE. Methods This is a prospective observational cohort study. We used data from the EURO-ENDO registry. Seven hospitals in the Netherlands have participated and included patients with IE between April 2016 and April 2018. Results A total of 139 IE patients were included. Prosthetic valve endocarditis constituted 32.4% of the cases, cardiac device related IE 7.2% and aortic root prosthesis IE 3.6%. In-hospital mortality was 14.4% (20 patients) and one-year mortality was 21.6% (30 patients). The incidence of embolic events under treatment was 16.5%, while congestive heart failure or cardiogenic shock occurred in 15.1% of the patients. Transthoracic and transoesophageal echocardiography were performed most frequently (97.8%; 81.3%) and within 3 days after IE suspicion, followed by 18F‑fluorodeoxyglucose positron emission tomography/computed tomography (45.3%) within 6 days and multi-slice computed tomography (42.4%) within 7 days. Conclusion We observed a high percentage of prosthetic valve endocarditis, rapid and extensive use of imaging and a relatively low in-hospital and one-year mortality of IE in the Netherlands. Limitations include possible selection bias.

Background: Long QT syndrome (LQTS) is associated with malignant arrhythmias and sudden death at young age. Diagnosis is primarily based on prolongation of the QT interval on the electrocardiogram (ECG). However, different methods are used to measure the QT interval. The effect of this practice on diagnosing LQTS is unknown and could result in inappropriate reassurance or treatment. Purpose: To assess possible differences between different methods of QT interval measurements in distinguishing LQTS patients from controls. Methods: Confirmed carriers of a pathogenic mutation in the KCNQ1 (LQTS1), KCNH2 (LQTS2) and SCN5A (LQTS3) genes were included as cases and their genotype-negative family members as controls. Three complexes on the baseline ECG were first marked and then analyzed applying both the tangent (QT-tangent) and threshold method (QT-threshold) in two separate sessions. Measurements were done blinded for subject characteristics. The measured complexes were averaged and corrected for HR with the Bazett formula (QTc). ECGs with a ventricular paced rhythm, complete bundle branch block and atrial-/ventricular arrhythmias were excluded. Sensitivity and specificity were determined for arbitrary cut-offs of 450 milliseconds (ms) in males and 460 ms in females, and for optimal cut-off values based on receiver-operating characteristic analyses. Results: We included 1363 individuals (294 LQTS1, 357 LQTS2, 131 LQTS3 and 581 controls); aged 34 years (standard deviation 21 years); 55% female, median HR 70 (interquartiles 61-83) beats per minute. Compared to controls, LQTS patients were younger (29 years versus 40 years, p<0.001), and more likely to be female (58% versus 52%, p=0.04). There was no difference in HR between the two groups (p=0.40). In LQTS1, LQTS3 and controls, measurements by QTtangent were significantly shorter compared to QT-threshold (absolute difference 7-12ms, p<0.0001). The table summarizes the performance of cut-off values using different methods. Conclusion:The length of the QT interval is different depending on the method used for determination. Particularly, the number of false positives is influenced by the method chosen to distinguish LQTS patients from controls, possibly resulting in inappropriate therapy in these patients. Background: Systemic Sclerosis (SSc) is a connective tissue disease characterized by vascular dysfunction and excessive fibrosis involving the skin and visceral organs. Visceral involvement, including cardiac manifestations, interstitial lung disease (ILD) and pulmonary hypertension (PH) can lead to severe clinical complications. We hypothesized that fragmented QRS complex (fQRS) in 12-lead ECG is potentially attributed to cardiac involvement in SSc patients. Purpose: The aim of the study was to investigate the frequency of fQRS in SSc patients, in relationship to other complications. Methods: The present study enrolled 69 consecutive SSc patients (56 females, 62±14 years) without obvious cardiac disease and 69 healthy control subjects whose age, gender, left ventricul...