Genetic and Phenotypic Characterization of Community Hospital Patients With QT Prolongation.

Background-Congenital long-QT syndrome (LQTS) is a genetic disorder characterized by prolongation of the corrected QT interval (QTc) on an ECG. The aim of the present study was to estimate the prevalence of pathogenic and likely pathogenic sequence variants in patients who had at least 1 ECG with a QTc >= 500 ms. Methods and Results-Telemark Hospital Trust is a community hospital within the Norwegian national health system, serving approximate to 173 000 inhabitants. We searched the ECG database at Telemark Hospital Trust, Norway, from January 2004 to December 2014, and identified 1531 patients with at least 1 ECG with a QTc >= 500 ms. At the time of inclusion in this study (2015), 766 patients were alive. A total of 733 patients were invited to participate, and 475 accepted. The 17 genes that have been reported to cause monogenic LQTS were sequenced among the patients. Pro-QTc score was calculated for each patient. A molecular genetic cause of LQTS was detected in 31 (6.5%) of 475 patients. These patients had a lower pro-QTc score than those without pathogenic or likely pathogenic variants (1.7 +/- 1.0 versus 2.8 +/- 1.6; P<0.001). Conclusions-Compared with the general population, hospitalized patients with a QTc >= 500 ms in at least 1 ECG recording had an increased likelihood for pathogenic and likely pathogenic variants in LQTS genes. We recommend increased awareness of the possibility of LQTS in patients with at least 1 ECG with a QTc >= 500 ms.