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Demonstration of value of optimizing ECG triggering for cardiovascular magnetic resonance in patients with congenital heart disease

Thomas Knesewitsch1, Christian Meierhofer1, Henrike Rieger1, Jürgen Rößler2, Michael Frank2, Stefan Martinoff3, John Hess1, Heiko Stern1 and Sohrab Fratz1*

Author Affiliations

1 Department of Pediatric Cardiology and Congenital Heart Disease, Deutsches Herzzentrum München, Klinikum an der Technischen Universität München, Lazarettstr. 36, 80636, Munich, Germany

2 Siemens AG, Healthcare, Imaging & Therapy Systems, Magnetic Resonance, Erlangen, Germany

3 Department of Radiology, Deutsches Herzzentrum München, Klinikum an der Technischen Universität München, Munich, Germany

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Journal of Cardiovascular Magnetic Resonance 2013, 15:3  doi:10.1186/1532-429X-15-3

Published: 16 January 2013



Optimal ECG triggering is of paramount importance for correct blood flow quantification during cardiovascular magnetic resonance (CMR). However, optimal ECG triggering and therefore blood flow quantification is impaired in many patients with congenital heart disease (CHD) due to complex QRS patterns. Therefore, a new ECG-trigger algorithm was developed to address triggering problems due to complex QRS patterns.

The aim of this study was to test this new ECG-trigger algorithm in routine patients with CHD and its impact on blood flow quantification.


35 consecutive routine patients with CHD undergoing CMR were included in the study. (40% Fallot’s Tetralogy, 20% aortic arch pathology, 14% transposition of the great arteries, 26% others; age 26+/−11 yrs).

In all patients, blood flow in the ascending aorta was quantified using the old ECG-trigger algorithm and the new ECG-trigger algorithm in random order. Blood flow quantified using the old or new ECG-trigger algorithm was compared by Bland-Altman analysis.

Three blinded investigators evaluated the vector clouds and trigger points of both ECG-trigger methods. Evaluation criteria were false positive and false negative triggered QRS complexes (specificity and sensitivity), and accuracy of detection. Accuracy of detection was defined as time scatter of the trigger around the correct trigger point.


Specificity, sensitivity, and accuracy of detection significantly increased using the new ECG-trigger algorithm compared to the old ECG-trigger algorithm.

Blood flow quantification using the old or new ECG-trigger algorithm differed more than 5% in 31% of the cases.


Our results suggest that optimizing ECG triggering during CMR using our new algorithm can avoid errors of >5% in approximately 1/3 of routine patients with congenital heart disease (CHD). We furthermore suggest that incorrect ECG triggering appears to be problematic for blood flow quantification of many patients with CHD undergoing routine CMR.

ECG triggering; Congenital heart disease; Blood flow quantification; Vectorcardiography (VCG)