Hypertrophic cardiomyopathy (HCM) may be associated with very narrow QRS while left ventricular hypertrophy (LVH) may increase QRS duration.

To determine the correlations between left myocardial mass (LVM) and QRS duration in HCM, left ventricular non-compaction (LVNC), post-hypertensive hypertrophy (LVH) and a control population.

HCM, LVNC, LVH and controls with healthy hearts from Toulouse and Bordeaux University Hospitals were retrospectively studied. Indexed automatic measurement of left ventricular mass (LVM) on MRI was correlated to automatic measurement of QRS duration on surface ECG. Potential confounding factors that can modify intraventricular conduction were listed and included in analysis.

Two hundred and twenty-one HCM, 28 LVNC, 16 LVH and 40 controls were retrospectively included. Mean QRS duration was 92ms for HCM, 104 for LVNC, 110 for LVH and 92 for controls (P<0.01). Mean LVM was 100, 90, 108 and 68g/m² respectively (P<0.01). A negative correlation was found between LVM and QRS duration in the HCM group (P=0.03). The relationship was reverse in LVNC (P=0.01), although not significant in LVH and controls. Multivariate analysis confirms these trends with significant correlations within each group and significant difference between HCM and LVH+LVNC. A regression formula including QRS duration, LVM, maximal wall thickness and myocardial fibrosis was tested to predict the diagnosis of HCM vs. LVH in 54 additional patients, yielding sensitivity, specificity, negative and positive predictive value of around 80%.

QRS duration significantly and independently increases with LVM in LVNC, LVH or in healthy hearts while reverse relationship is present in HCM. These results could be used as additional diagnosis criteria for borderline cases in the future.