What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Hypertrophic cardiomyopathy (n=85). Intervention: Presence of late gadolinium enhancement (LGE) vs. Absence of LGE. Primary outcome: QT variability index (QTVI) (p=<0.0001).

January 1, 2014Open Access

Myocardial Repolarization Dispersion and Late Gadolinium Enhancement in Patients With Hypertrophic Cardiomyopathy

Q: What are the key findings of this study?

In patients with hypertrophic cardiomyopathy, the presence of late gadolinium enhancement on cardiac magnetic resonance was associated with significantly higher temporal myocardial repolarization dispersion (P<0.0001).

Key Result

In patients with hypertrophic cardiomyopathy, the presence of late gadolinium enhancement on cardiac magnetic resonance was associated with significantly higher temporal myocardial repolarization dispersion (P<0.0001).

Study Design

Type

Cross-Sectional (n=85)

Multicenter

Structured PICO

Does late gadolinium enhancement on cardiac magnetic resonance correlate with markers of myocardial repolarization dispersion in patients with hypertrophic cardiomyopathy?

Population

85 outpatients with hypertrophic cardiomyopathy (HCM)

Intervention

Cardiac magnetic resonance (CMR) to assess late gadolinium enhancement (LGE) and short-period electrocardiogram to assess repolarization dispersion

Comparator

Patients without late gadolinium enhancement (LGE)

Outcome

Temporal myocardial repolarization dispersion measured by QT variance normalized for QT mean (QTVN) and QT variability index (QTVI)surrogate

In patients with hypertrophic cardiomyopathy, the extent of late gadolinium enhancement on CMR correlates significantly with temporal myocardial repolarization dispersion, suggesting a link between myocardial fibrosis and arrhythmic substrate.

Main Result

Absolute Event Rate: -0.57% vs -0.865%

p-value: p=<0.0001

Limitations

Small study sample
Non-prospective study design
Lack of data on the prevalence and impact of sarcomere gene mutations
Technical difficulty in computing the end of the T wave
Lack of data on the possible relationship with midventricular obstruction

Abstract

BACKGROUND: Growing evidence suggests that late gadolinium enhancement (LGE) at cardiac magnetic resonance (CMR) is an additive marker of disease severity, and possibly of arrhythmic risk, in hypertrophic cardiomyopathy (HCM). We investigated the possible relationship between LGE and markers of myocardial repolarization dispersion in HCM. METHODS AND RESULTS: Eighty-five HCM outpatients underwent CMR and short-period electrocardiogram analysis to calculate the temporal myocardial repolarization dispersion through the QT variance normalized for QT mean (QTVN) and the QT variability index (QTVI). The QT dispersion in the spatial domain was also obtained. Patients with LGE (62%) had higher left atrial volume, maximum wall thickness, and left ventricular mass (P<0.0001), as well as a greater prevalence of non-sustained ventricular tachycardia (P<0.0001) and hypotensive blood pressure response (P=0.044). Both QTVN and QTVI were higher in the group with LGE (P<0.0001). At multivariate analysis, using QTVI as the dependent variable, %LGE (P<0.0001), age (P<0.0001), left ventricular outflow obstruction (P=0.038), and sudden cardiac death risk factor burden (P=0.020) reached statistical significance. Otherwise, only %LGE (P=0.005) and left ventricular mass index (P=0.015) remained associated with QTVN. CONCLUSIONS: Temporal myocardial repolarization dispersion correlates with LGE extent. Whether these variables could be useful in HCM clinical management warrants confirmation by larger prospective studies.

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