We found a strong correlation between myocardial velocities measured with PW-TDI and CC-TDI in wide range of patients with and without left ventricular systolic and diastolic dysfunction and with and without symptoms. This indicates that although both methodologies are different, they represent the same velocity increase and decrease profile. However, the actual values that are obtained are markedly different. As a consequence, a significant difference in calculated E/E′ values was found, which has important implications for the classification of patients with diastolic heart failure. Evaluation of diastolic function has become increasingly important, since it has been well established that nearly half of the patients that are hospitalized for acute decompensated heart failure have a relatively preserved systolic function, and diastolic dysfunction is considered to be the main cause of heart failure in these patients. Well-defined criteria for the diagnosis of diastolic heart failure are therefore important. A major step forward has been made with the consensus statement on the diagnosis of heart failure with normal left ventricular ejection fraction by the European Society of Cardiology . One of the main measurements proposed to assess diastolic function is tissue velocity E (E′), and cut-off values have been agreed upon for classification of diastolic function using in particular the E/E′ ratio. It is important to realize that the proposed E/E′ cut-off values are based on pulsed Doppler measurements (PW-TDI). CC-TDI is routinely used in many clinics, and if they apply the same criteria for diastolic dysfunction as suggested in the ESC consensus statement, there will be a considerable overestimation of patients with diastolic dysfunction.
Previous studies comparing PW-TDI and CC-TDI have shown comparable results in phantoms, smaller cohorts of healthy volunteers and patients [14–16]. Kukulski et al.  investigated phantoms and 23 healthy volunteers (mean age 33 years), and found a good correlation between both methods but with unsatisfactory limits of agreement. McCulloch et al.  investigated 31 patients and showed significant correlations between myocardial velocities measured with PW-TDI and CC-TDI, with a significant underestimation of CC-TDI and consequently an overestimation of E/E′. In their analysis of E′ values, they found a relation which could be described by the following formula: E′ (PW-TDI) = 1.46 + 1.14 × E′ (CC-TDI). However, as they stated, a numeric uniform correction calculating PW-TDI-derived E′ from CC-TDI-derived E′ was hampered by the variable relationship (~10–90% difference between values) as was shown in their Bland and Altmann analysis. Our Bland and Altmann analysis shows a better relationship (~10–50% difference between values).
Tartiere et al.  compared PW-TDI and CC-TDI in 52 patients. They also found a similar difference between the two methods. Their Bland and Altman plot showed results comparable to our data for E′ values between 3 and 11 cm/s. Values above 11 cm/s in their group were sparse (four patients) compared to our population, and therefore our study gives more insight in the differences between both methods for a larger range of values. This leads to a more complete insight in the relation between PW-TDI and CC-TDI, showing increased differences with an increasing value of E′.
The differences between the E′ measurements can be partially explained by the different methodologies used for the estimation of myocardial velocities. PW-TDI is computed with a fast Fourier transformation (FFT) technique which will result in a peak velocity measured, while CC-TDI uses autocorrelation methodology resulting in peak-mean velocity. These limitations and differences in methodology were described in detail by Kukulski et al. . A second explanation for the observed difference might be the placement of the sample within the myocardium. However, this explanation is less likely to account for the structural difference in TDI values since roughly the same myocardial region was sampled. Still slightly different transducer angulation and evaluation of different heart cycle may account for some of the differences. Other explanations might be related to the use of filters to reduce noise.
Technical disadvantages are more or less the same in both methodologies; however, CC-TDI has less spatial resolution and the advantage of offline measurements. Another advantage of CC-TDI methodology are other applications that can be performed on these tissue filtered images like tissue tracking and strain rate imaging.