Late Gadolinium Enhancement on Cardiac MRI Correlates with QT Dynamicity Represented by QT/RR Relationship in Patients with Ventricular Arrhythmias

Abstract

Background: The distribution of late gadolinium enhancement (LGE) on the cardiac MRI (CMR) indicates myocardial fibrosis and provides information of possible reentry substrates. QT dynamicity reflecting repolarization abnormalities has gained attention as a potential prognostic predictive factor.

Objective: To clarify the correlation between the LGE distribution on CMR and QT dynamicity represented by the QT/RR relationship.

Methods: CMR and QT/RR analyses using Holter monitoring were performed in 34 patients (24 males, 60 ± 11 years) with ventricular tachycardia (VT) and/or ventricular fibrillation (VF). The LGE on CMR was scored using a 4-point score in 17 left ventricular segments. The sum of the LGE scores was calculated for each patient. The QT/RR slope and daytime/nighttime QT/RR ratio (day/night ratio) were calculated. The correlation between the slope or the day/night QT/RR ratio and late enhancement findings was analyzed.

Results: All patients were divided into 23 LGE positive (LGE(+)) and 11 LGE negative (LGE(-)) patients. The slopes of the QTe/RR and QTa /RR were significantly steeper in the LGE(+) than in LGE(-) patients (0.21 ± 0.03 vs 0.13 ± 0.02; P < 0.001, 0.19 ± 0.03 vs 0.13 ± 0.02; P < 0.001, respectively), and both slopes were significantly correlated with the total LGE scores (r = 0.83, P < 0.001; r = 0.71, P < 0.001, respectively). In the LGE(+) patients, the QTe day/night (1.37 ± 0.38 vs 0.91 ± 0.33; P = 0.002) and QTa day/night ratios (1.33 ± 0.26 vs 1.06 ± 0.30; P = 0.011) were significantly greater than those in the LGE(-) patients.

Conclusion: The LGE distribution was closely related to the QT dynamicity, suggesting that a combination of these markers can be a powerful tool for understanding the background pathophysiology.

Keywords: QT dynamicity; cardiac MRI; late gadolinium enhancement; sudden cardiac death; ventricular fibrillation; ventricular tachycardia.

© 2015 Wiley Periodicals, Inc.

Figures

Figure 1

The myocardial segments and late gadolinium enhancement (LGE) score on cardiac MRI are illustrated.

Figure 2

Correlation between the QTe/RR slope or QTa/RR slope and the total LGE score.

Figure 3

A representative example of the cardiac MRI (CMR) and QT/RR analysis in a 67‐year‐old woman who was referred to our department due to ventricular fibrillation. She was diagnosed with sarcoidosis. The contrast image (A) from a basal short axial slice was divided into six segments. The endocardial (red) and epicardial (green) borders were manually traced. A computer‐assisted algorithm applied signal‐intensity thresholds of >4 SDs above the normal myocardial segment to delineate the scar (red region). The average transmural extent of the enhancement in each segment was scored using a 4‐point score. The total LGE score was 38. Both the QTa/RR slope and QTe/RR slope had large values (B) and the QT/RR day/night ratio in this patient was high (C).

Figure 4

A representative example of the CMR and QT/RR analysis in a 54‐year‐old man who was referred to our department due to ventricular fibrillation. He was diagnosed with idiopathic ventricular fibrillation. The contrast image (A) from a basal short axial slice was divided into six segments and the total LGE score was zero. Both the QTa/RR slope and QTe/RR slope had small values (B) and the QT/RR day/night ratio in this patient was low (C).

Figure 5

A representative example of the cardiac MRI (CMR) and QT/RR analysis in a 62‐year‐old man who was referred to our department due to sustained ventricular tachycardia. He was diagnosed with hypertrophic cardiomyopathy. The contrast image (A) from a basal short axial slice was divided into six segments and the total LGE score was 18. Both the QTa/RR slope and QTe/RR slope had large values (B) and the QT/RR day/night ratio in this patient was high (C).