Abstract
BackgroundCardiac resynchronization therapy (CRT) has been shown to decrease mortality in 60-70% of advanced heart failure patients with left bundle branch block (LBBB) and QRS duration > 120 ms. There have been intense efforts to find reproducible non-invasive parameters to predict CRT response. We hypothesized that different left ventricular contraction patterns may exist in LBBB patients with depressed systolic function and applied tagged cardiovascular magnetic resonance (CMR) to assess circumferential strain in this population.MethodsWe determined myocardial circumferential strain at the basal, mid, and apical ventricular level in 35 subjects (10 with ischemic cardiomyopathy, 15 with non-ischemic cardiomyopathy, and 10 healthy controls). Patterns of circumferential strain were analyzed. Time to peak systolic circumferential strain in each of the 6 segments in all three ventricular slices and the standard deviation of time to peak strain in the basal and mid ventricular slices were determined.ResultsDyskinesis of the anterior septum and the inferior septum in at least two ventricular levels was seen in 50% (5 out of 10) of LBBB patients while 30% had isolated dyskinesis of the anteroseptum, and 20% had no dyskinesis in any segments, similar to all of the non-LBBB patients and healthy controls. Peak circumferential strain shortening was significantly reduced in all cardiomyopathy patients at the mid-ventricular level (LBBB 9 ± 6%, non-LBBB 10 ± 4% vs. healthy 19 ± 4%; both p < 0.0001 compared to healthy), but was similar among the LBBB and non-LBBB groups (p = 0.20). The LBBB group had significantly greater dyssynchrony compared to the non-LBBB group and healthy controls assessed by opposing wall delays and 12-segment standard deviation (LBBB 164 ± 30 ms vs. non-LBBB 70 ± 17 ms (p < 0.0001), non-LBBB vs. healthy 65 ± 17 ms (p = 0.47)).ConclusionsSeptal dyskinesis exists in some patients with LBBB. Myocardial circumferential strain analysis enables detailed characterization of contraction patterns, strengths, and timing in cardiomyopathy patients with and without LBBB.
Highlights
Cardiac resynchronization therapy (CRT) has been shown to improve symptoms, increase exercise capacity, decrease heart failure (HF) hospitalizations, and decrease mortality in patients with New York Heart Association (NYHA) Class III/IV HF with depressed systolic function, and a prolonged QRS in left bundle branch block (LBBB) morphology [1,2,3]
Patient cohort We studied twenty-five patients with systolic dysfunction referred for assessment of left ventricular (LV) function and imaged between June 2006 and August 2009, including 10 patients with chronic ischemic cardiomyopathy (ICM) (age 64 ± 8 years, 90% male, LV ejection fraction (EF) 30 ± 6%) and 15 patients with non-ischemic dilated cardiomyopathy
Some patients with LBBB had severe mechanical dyssynchrony manifested as a specific contractile pattern with initial presystolic septal contraction during isovolumic contraction period followed by dyskinesis of the interventricular septum during the entire systole
Summary
Cardiac resynchronization therapy (CRT) has been shown to improve symptoms, increase exercise capacity, decrease heart failure (HF) hospitalizations, and decrease mortality in patients with New York Heart Association (NYHA) Class III/IV HF with depressed systolic function, and a prolonged QRS in left bundle branch block (LBBB) morphology [1,2,3]. Tagged cardiovascular magnetic resonance (CMR) is a noninvasive technique for measuring local deformation of the myocardium and quantitative assessment of mechanical dyssynchrony [12,13,14]. Cardiac resynchronization therapy (CRT) has been shown to decrease mortality in 60-70% of advanced heart failure patients with left bundle branch block (LBBB) and QRS duration > 120 ms. We hypothesized that different left ventricular contraction patterns may exist in LBBB patients with depressed systolic function and applied tagged cardiovascular magnetic resonance (CMR) to assess circumferential strain in this population
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