Abstract 1921: Quantification of Intersegmental Variations in Time to Peak Wall Thickening and Motion Using Cardiac Magnetic Resonance: A Novel Method for Assessing Cardiac Dyssynchrony
Background: Although echocardiography provides excellent temporal resolution, approaching 10 ms, it is limited to imaging only a portion of the left ventricle(LV). A considerable overlap of the echocardiographic markers of dyssynchrony between patients with heart failure(HF) and healthy controls is also seen. Cardiac magnetic resonance(CMR) imaging provides less temporal resolution, approximately 25 to 40 ms, but has a superior spatial resolution. We hypothesised that by quantifying the intersegmental variations in time to peak wall thickening and motion using CMR, dyssynchrony can be demonstrated in patients with heart failure irrespective of their QRS durations
Methods: 104 patients were studied by CMR (Group A: 53 with HF and QRS < 120 ms; group B: 29 with HF and QRS ≥ 120 ms; group C: 22 healthy controls). The standard deviations of the time-to peak segmental wall thickening (CMR-TthickSD) and wall motion (CMR-TwmSD) for up to 60 myocardial segments (from base to apex) were used as dyssynchrony scores. The ability of these scores to discriminate between HF and C, was explored using receiver operator characteristic curves (ROC).
Results: CMR-TthickSD was higher in A (186.0 ± 8.5 ms, p < 0.0001) and B (166.0 ± 9.5 ms, p < 0.0001) than in C (50.0 ± 1.7 ms). CMR-TwmSD was also higher in A (141.6 ± 7.5 ms, p < 0.0001) and B (105.5 ± 5.9 ms, p < 0.0001) than in C (45.1 ± 1.9 ms). Area under ROC for the discrimination between HF and controls increased from 0.92 to 1.00 for CMR-TthickSD and from 0.86 to 1.0 for CMR-TwmSD as the number of segments increased from 4 to all segments. Cut off values of 90.8ms for CMR-TthickSD and 65.4 ms for CMR-TwmSD achieved absolute discrimination between controls and patients with heart failure (sensitivity and specificity of 100 %). There were, however, strong positive correlations between QRS duration and both CMR-TthickSD (r = 0.33, p = 0.0032) and CMR-TwmSD (r = 0.59, p < 0.0001).
Conclusions LV dyssynchrony is observed in all patients with HF, regardless of QRS duration. In contrast to echocardiographic measures, CMR-TthickSD and CMR-TwmSD provide absolute discrimination between HF and C. QRS duration is a good surrogate measure of LV dyssynchrony.