Echocardiography vs MRI in Evaluating the Athlete's Heart
Echocardiography vs MRI in Evaluating the Athlete's Heart
The present study shows that compared with echocardiography, cardiac MRI ventricular and atrial dimensions and ventricular volumes are larger, and wall thickness and wall mass are smaller.
Although there was a good linear correlation of obtained dimensions with the actual volume on cardiac MRI, the difference in volume and wall mass measurements between echocardiography and cardiac MRI was large. We have provided a possible correction factor on the echocardiographic formulas to facilitate better intertechnique comparability.
Although echocardiographic image quality has improved greatly in recent years, cardiac MRI still provides a higher LV and RV volume and wall mass measurement reproducibility and accuracy owing to its high spatial resolution. Several studies confirm that RV and LV volumes and dimensions on 2D echocardiography are significantly lower, and LV wall mass and wall thickness higher as compared with cardiac MRI measurements, with moderate agreement per measurement in healthy subjects, as well as in patients. In particular, the large differences between LV volumes and wall mass on cardiac MRI compared with those derived from M-mode echocardiography show the limited accuracy of the ASE and Teichholz formulas.
To our knowledge, this is the first paper using a large cohort of healthy athletic and non-athletic persons, containing both men and women, to compare echocardiographic and cardiac MRI data in a head-to-head fashion. Previous studies comparing echocardiography results with cardiac MRI in athletic subjects included only a small group of either athletic males or females and allowed for much larger time windows between the two examinations.
Even though we minimised the methodological difference for individual variations by performing both examinations consecutively during one session, our results showed larger mean differences between echocardiographic measurements and cardiac MRI than mostly reported in the literature. One explanation is that the ventricular trabecularisation is recognised better on cardiac MRI and is therefore included in the ventricular volume diameter instead of inclusion in the LV wall thickness as partly occurs on echocardiography (figure 1). Another explanation is the use of different cardiac MRI contour tracing protocols, including or excluding the papillary muscles and trabecularisations as ventricular wall mass, as well as the option to include the RVOT or LVOT in the blood volume on cardiac MRI or not.
A reliable assessment of ventricular dimensions by non-invasive imaging is paramount to rule out potentially lethal cardiomyopathies. To this end, a large body of evidence has been published producing specific cut-off values specifically for echocardiography. Using these echocardiographic cut-off values for cardiac MRI is unjustified without establishing the difference between the modalities. Our results suggest that unmodified implementation of echocardiographic absolute reference values and cut-off values for cardiac pathology on cardiac MRI measurements is not recommended. In athletic persons, there is additional concern because of the sport-heart-related larger ventricular volumes and wall mass, especially in elite athletic men.
For example, in elite athletic men, the absolute RVIT exceeded a 50 mm threshold, sometimes used for arrhythmogenic RV cardiomyopathy more frequently on cardiac MRI (81%) compared with echocardiography (5%). The absolute LVIDd exceeded a 60 mm threshold, a commonly used echocardiographic cut-off for dilated cardiomyopathy more frequently in cardiac MRI (54%) versus echocardiography (7%). These differences suggest that the cut-off value should be adjusted for cardiac MRI (using the 95th percentile). A septal wall thickness of >12 mm on echocardiography has generally been regarded as a cut-off value to indicate LV hypertrophy. The difficulty in recognising the trabecularisation border on echocardiography is illustrated by the similar measurements between echocardiography and cardiac MRI in septal wall thickness (26% vs 23% above 12 mm cut-off) and large variation in PWd (61% vs 14% above 10 mm cut-off).
In clinical practice, a single dimension is often used to get an impression of a three-dimensional parameter. Our results indicate that most of these commonly applied measurements do provide a good insight into the volume and wall mass as calculated on cardiac MRI in both echocardiography and cardiac MRI. The difference between these two modalities seems to be systematic, not influenced by the value of the measure itself, as indicated by the comparable difference in the controls (normal dimensions and LV wall thickness) and athletic persons (ventricular enlargement and LV hypertrophy). Echocardiographic estimation of the LV wall mass and LV volumes using commonly applied formulas do, however, show an increasing difference as the absolute values increased. Although this is to be expected owing to the exponential contributions of the 2D measurements in the different formulas, the relationship was linear (figure 2C). This problem might be overcome using 3D echocardiography, which is free from geometrical assumptions.
Several factors, other than the dissimilarity in spatial resolution, could have provided additional variation to the observed difference between the two techniques. First, the measurements were performed by two different observers. Although we checked all measurements for overall consistency with the guidelines, this could have resulted in a systematic difference in the application of the ASE guidelines, and explain the variation in difference between RA (−1.9 mm) and LA (+10.1 mm) where the exclusion of the pulmonary vein ostia could have been performed differently. Second, some reference points used for echocardiographic measurements were less clear on cardiac MRI, such as the tips of the atrio-ventricular valves. This could have resulted in a slightly different measurement location within the heart, which was the case for the LVIT and RVIT. Third, image planes were probably not identical during acquisition. While cardiac MRI follows a protocolised image acquisition sequence, echocardiography is a more user-dependent method, where different cardiac compartments could be recorded separately to obtain the optimal image. Nevertheless, the observed differences between echocardiography and cardiac MRI are too large to be solely attributed to these limitations and showed a typical systematic difference with a Gaussian distribution, suggesting a relevant clinical difference.
Discussion
The present study shows that compared with echocardiography, cardiac MRI ventricular and atrial dimensions and ventricular volumes are larger, and wall thickness and wall mass are smaller.
Although there was a good linear correlation of obtained dimensions with the actual volume on cardiac MRI, the difference in volume and wall mass measurements between echocardiography and cardiac MRI was large. We have provided a possible correction factor on the echocardiographic formulas to facilitate better intertechnique comparability.
Comparison to Previous Literature
Although echocardiographic image quality has improved greatly in recent years, cardiac MRI still provides a higher LV and RV volume and wall mass measurement reproducibility and accuracy owing to its high spatial resolution. Several studies confirm that RV and LV volumes and dimensions on 2D echocardiography are significantly lower, and LV wall mass and wall thickness higher as compared with cardiac MRI measurements, with moderate agreement per measurement in healthy subjects, as well as in patients. In particular, the large differences between LV volumes and wall mass on cardiac MRI compared with those derived from M-mode echocardiography show the limited accuracy of the ASE and Teichholz formulas.
To our knowledge, this is the first paper using a large cohort of healthy athletic and non-athletic persons, containing both men and women, to compare echocardiographic and cardiac MRI data in a head-to-head fashion. Previous studies comparing echocardiography results with cardiac MRI in athletic subjects included only a small group of either athletic males or females and allowed for much larger time windows between the two examinations.
Even though we minimised the methodological difference for individual variations by performing both examinations consecutively during one session, our results showed larger mean differences between echocardiographic measurements and cardiac MRI than mostly reported in the literature. One explanation is that the ventricular trabecularisation is recognised better on cardiac MRI and is therefore included in the ventricular volume diameter instead of inclusion in the LV wall thickness as partly occurs on echocardiography (figure 1). Another explanation is the use of different cardiac MRI contour tracing protocols, including or excluding the papillary muscles and trabecularisations as ventricular wall mass, as well as the option to include the RVOT or LVOT in the blood volume on cardiac MRI or not.
Clinical Relevance
A reliable assessment of ventricular dimensions by non-invasive imaging is paramount to rule out potentially lethal cardiomyopathies. To this end, a large body of evidence has been published producing specific cut-off values specifically for echocardiography. Using these echocardiographic cut-off values for cardiac MRI is unjustified without establishing the difference between the modalities. Our results suggest that unmodified implementation of echocardiographic absolute reference values and cut-off values for cardiac pathology on cardiac MRI measurements is not recommended. In athletic persons, there is additional concern because of the sport-heart-related larger ventricular volumes and wall mass, especially in elite athletic men.
For example, in elite athletic men, the absolute RVIT exceeded a 50 mm threshold, sometimes used for arrhythmogenic RV cardiomyopathy more frequently on cardiac MRI (81%) compared with echocardiography (5%). The absolute LVIDd exceeded a 60 mm threshold, a commonly used echocardiographic cut-off for dilated cardiomyopathy more frequently in cardiac MRI (54%) versus echocardiography (7%). These differences suggest that the cut-off value should be adjusted for cardiac MRI (using the 95th percentile). A septal wall thickness of >12 mm on echocardiography has generally been regarded as a cut-off value to indicate LV hypertrophy. The difficulty in recognising the trabecularisation border on echocardiography is illustrated by the similar measurements between echocardiography and cardiac MRI in septal wall thickness (26% vs 23% above 12 mm cut-off) and large variation in PWd (61% vs 14% above 10 mm cut-off).
In clinical practice, a single dimension is often used to get an impression of a three-dimensional parameter. Our results indicate that most of these commonly applied measurements do provide a good insight into the volume and wall mass as calculated on cardiac MRI in both echocardiography and cardiac MRI. The difference between these two modalities seems to be systematic, not influenced by the value of the measure itself, as indicated by the comparable difference in the controls (normal dimensions and LV wall thickness) and athletic persons (ventricular enlargement and LV hypertrophy). Echocardiographic estimation of the LV wall mass and LV volumes using commonly applied formulas do, however, show an increasing difference as the absolute values increased. Although this is to be expected owing to the exponential contributions of the 2D measurements in the different formulas, the relationship was linear (figure 2C). This problem might be overcome using 3D echocardiography, which is free from geometrical assumptions.
Limitations
Several factors, other than the dissimilarity in spatial resolution, could have provided additional variation to the observed difference between the two techniques. First, the measurements were performed by two different observers. Although we checked all measurements for overall consistency with the guidelines, this could have resulted in a systematic difference in the application of the ASE guidelines, and explain the variation in difference between RA (−1.9 mm) and LA (+10.1 mm) where the exclusion of the pulmonary vein ostia could have been performed differently. Second, some reference points used for echocardiographic measurements were less clear on cardiac MRI, such as the tips of the atrio-ventricular valves. This could have resulted in a slightly different measurement location within the heart, which was the case for the LVIT and RVIT. Third, image planes were probably not identical during acquisition. While cardiac MRI follows a protocolised image acquisition sequence, echocardiography is a more user-dependent method, where different cardiac compartments could be recorded separately to obtain the optimal image. Nevertheless, the observed differences between echocardiography and cardiac MRI are too large to be solely attributed to these limitations and showed a typical systematic difference with a Gaussian distribution, suggesting a relevant clinical difference.
Source...