Mechanical Left Ventricular Dyssynchrony in Heart Failure Patients With Narrow QRS Duration as Assessed by Three-Dimensional Speckle Area Tracking Strain

The aim of this study was to assess whether heart failure (HF) patients with narrow QRS durations have mechanical left ventricular (LV) dyssynchrony compared to those with wide QRS durations and with normal subjects. The strain dyssynchrony index with 3-dimensional area tracking (ASDI) was used, which represents mechanical LV dyssynchrony and residual endomyocardial function from circumferential as well as longitudinal directions. The study included 79 subjects: 32 HF patients with ejection fractions ≤35% and narrow QRS durations (<120 ms) and 22 with ejection fractions ≤35% and wide QRS durations (≥120 ms), all candidates for cardiac resynchronization therapy, and 25 normal controls. ASDI was calculated as the average difference between peak and end-systolic area strain of LV endocardium obtained using 3-dimensional speckle-tracking imaging using 16 LV segments (≥3.8% predefined as significant). ASDI in HF patients with narrow QRS durations was lower than in their counterparts with wide QRS durations (2.5 ± 1.3% vs 4.2 ± 1.2%, p <0.001) but higher than in normal controls (2.5 ± 1.3% vs 0.73 ± 0.53%, p <0.001). Furthermore, the prevalence of significant ASDI in HF patients with narrow QRS durations was significantly higher than in normal controls (22% vs 0%, p = 0.01) but significantly lower than in HF patients with wide QRS durations (22% vs 59%, p <0.01). In conclusion, HF patients with narrow QRS durations have LV dyssynchrony. These observations suggest that the use of 3-dimensional speckle area tracking strain might be extended to HF patients with narrow QRS durations who are being considered as potential candidates for cardiac resynchronization therapy.