Assessment of intraventricular mechanical dyssynchrony and prediction of response to cardiac resynchronization therapy: comparison between tissue Doppler imaging and real-time three-dimensional echocardiography.
OBJECTIVE
We studied the comparability of left ventricular (LV) mechanical dyssynchrony assessment by tissue Doppler imaging (TDI) and real-time three-dimensional echocardiography (RT3DE) in patients with a wide range of LV ejection fractions and different causes of cardiomyopathy. In addition, we evaluated the ability of both techniques to predict response to cardiac resynchronization therapy (CRT).


METHODS
A total of 90 patients and 30 healthy volunteers underwent both TDI and RT3DE. A subgroup of 27 patients underwent CRT and were evaluated before and 6 months after implantation. Mechanical dyssynchrony was measured with TDI using the standard deviation of time to peak systolic tissue velocity of 12 LV myocardial segments. With RT3DE, the standard deviation of time from QRS onset to minimal volume of 16 LV subvolumes was assessed. Indicators of response to CRT were a clinical improvement of >or= 1 New York Heart Association functional class, and reverse remodeling defined as a reduction of >or= 15% in LV end-systolic volume at 6 months.


RESULTS
A moderate correlation (r = 0.581, P < .001) was observed between TDI and RT3DE. No significant difference in the presence of mechanical dyssynchrony by TDI and RT3DE was observed (53% vs 48%, respectively). Agreement between techniques was comparable between patients with ischemic and nonischemic cardiomyopathy. However, up to 30% nonagreement between the 2 techniques was found, depending on the severity of LV dysfunction. Of the 27 patients undergoing CRT, clinical response was observed in 70% of patients, whereas reverse remodeling occurred in 63% of patients. All baseline characteristics were similar between responders and nonresponders, except for mechanical dyssynchrony assessed by RT3DE, which was significantly higher in responders compared with nonresponders (10.1% +/- 2.6% vs 5.1% +/- 1.2% for clinical response, P < .001; 10.0% +/- 2.8% vs 6.3% +/- 2.3% for reverse remodeling, P = .001). By applying previously defined cutoff values, receiver operating characteristic curve analysis demonstrated a sensitivity of 58% with a specificity of 50% for TDI and a sensitivity of 95% with a specificity of 87% for RT3DE to predict clinical response to CRT. For prediction of reverse remodeling after CRT, sensitivity and specificity were 59% and 50% for TDI, and 88% and 60% for RT3DE, respectively. The optimal cutoff value for systolic dyssynchrony index by RT3DE of 6.7% yielded a sensitivity of 90% with a specificity of 87% to predict clinical response, and a sensitivity of 88% with a specificity of 70% to predict reverse remodeling.


CONCLUSION
Marked differences between techniques are found for the presence of mechanical dyssynchrony when current cutoff values are applied, making interchangeability of these techniques uncertain. Assessment of mechanical dyssynchrony by RT3DE might be an appropriate alternative to TDI for accurate prediction of response to CRT.