Baggrund: Alvorlige tilfælde af venstresidig grenblok (LBBB) behandles med cardiac resynchronisation therapy (CRT), dog responderer mere end 30% af patienterne ikke på behandlingen, hvilket potentielt skyldes manglende elektrisk dyssynkroni. For at forbedre udvælgelsen af patienter til CRT implantation, kan ventrikel dyssynkroni potentielt kvantificeres ved at løse det inverse EKG-problem. Eksisterende løsninger baserer sig på >100 overflademålinger samt patientspecifikke modeller, hvilket begrænser anvendeligheden i klinisk praksis. Dette studie forsøger at bestemme den elektriske aktivering af ventriklerne ud fra 12-aflednings EKG målinger og en generisk hjerte-torso model, samt at kvantificere den interventrikulære elektriske dyssynkroni.Metode: Standard 12-aflednings EKG målinger fra 100 normale, 100 LBBB subjekter og 135 subjekter inden implantation af CRT, var inkluderet. Ved at løse det inverse EKG problem kunne ventrikelaktiveringen bestemmes i seks dipoler. Præcision og robusthed ved Gaussisk og Tikhonov regularisering med regulariseringsparameter λ=0 og λ=30 blev sammenlignet. Interventrikulær dyssynkroni blev målt som venstre-højre venkrikulær dyssynkroni (LRVU), og blev sammenlignet med QRS varighed, QRS areal og Q-LV. Resultater: Tikhonov λ=0 havde den mest akkurate EKG rekonstruktion i både normale og LBBB subjekter. LRVU var højere i LBBB subjekter sammenlignet med normale subjekter. Korrelationen af LRVU med QRS varighed og QRS areal var højere for LBBB(r^2=0.359, 0.791) og CRT subjekter(r^2=0.328, 0.630) sammenlignet med normale subjekter(r^2=0.178, 0.093). Yderligere var LRVU korreleret med Q-LV i CRT subjekter(r^2=0.441). Konklusion: Interventrikulær dyssynkroni kan kvantificeres ved at løse det inverse EKG problem ved standard 12-aflednings EKG og en generisk hjerte-torso model.Background: Severe left bundle branch block (LBBB) is treated with cardiac resynchronisation therapy (CRT), however more than 30% treated with CRT are non-responders, likely due to absence of electrical dyssynchrony. In order to improve patient selection, interventricular dyssynchrony can potentially be quantified by solving the inverse electrocardiography (ECG) problem. Existing solutions are based on >100 body surface measurements and patient specific geometries, which limits the clinical applicability. This study aims to determine the electrical activation of the ventricles from standard 12-lead ECG recordings and a generic heart-torso model, and quantify the interventricular electrical dyssynchrony. Method: Standard 12-lead ECG recordings from 100 normal subjects, 100 LBBB subjects, and 135 subjects admitted to CRT were included. The ventricular myocardial activation was determined in six dipoles. The accuracy and robustness of Gaussian regularisation and Tikhonov regularisation with regularisation parameter λ=0 and λ=30 was compared. Interventricular dyssynchrony was determined as the left-right ventricular uncoupling (LRVU) and compared to QRS duration, QRS area and Q-LV. Results: Tikhonov λ=0 yielded the most accurate ECG reconstruction in both normal and LBBB subjects. LRVU was higher in LBBB subjects compared to normal subjects. The correlation of LRVU with QRS duration and QRS area was higher in LBBB(r^2 =0.359, 0.791) and CRT subjects(r^2=0.328, 0.630) compared to normal subjects(r^2=0.178, 0.093). Furthermore LRVU was correlated with Q-LV in CRT subjects (r^2=0.441). Conclusion: Interventricular dyssynchrony can be quantified by solving the inverse ECG problem by standard 12-lead ECG and a generic heart-torso model.