[Natural harmonic echocardiography].

The acquisition of echocardiographic images in harmonic mode (a frequency double than the transmitted, or fundamental) improves imaging quality. We assessed whether harmonic imaging improves the detection of endocardial borders, evaluation of ventricular function and diagnostic confidence in the clinical arena. We have studied in fundamental and harmonic imaging 45 patients (age 20-89 years, mean 53 years) using a multifrequency transthoracic probe transmitting at 1.75 MHz and receiving at 3.5 MHz (Acuson Sequoia). In 34 low echogenic patients we assessed left ventricular function. The remaining 11 patients represented selected cases (i.e. atrial septal aneurysm, aortic dissection, endocarditis and atrial septal defect). The echocardiographic images were recorded on a magneto-optical disk and analyzed by two blinded observers. Endocardial definition has been semiquantitatively evaluated assigning a 0-4 score for each of the 16 segments of the left ventricle. A score of 0 was allotted to the non-visualizable segments and a score of 4 to the best detectable segments. Ejection fraction was calculated in each patient from the apical 4-chamber view. We compared endocardial border definition and ejection fraction at rest, in fundamental and harmonic mode, and assessed the interobserver agreement in the calculation of ejection fraction. Harmonic images always showed a better definition and lower noise compared to fundamental. Endocardial border definition was significantly improved in all segments (from 1.3 +/- 1.1 fundamental to 2.9 +/- 1.0 harmonic). Forty-two segments were non detectable in fundamental (score 0) compared to 5 in harmonic. Of these 42 segments, 37 were detectable in harmonic, with a score of 2.0 +/- 1.0. Conversely, none of the 5 segments non detectable in harmonic could be visualized in fundamental. The interobserver agreement in calculating ejection fraction was improved by harmonic imaging compared to fundamental (r = 0.91 and r = 0.67, respectively). In the selected clinical cases the diagnosis was easier and faster by harmonic imaging. The harmonic mode drastically improves echocardiographic imaging, it may be used routinely and reduce the need for more invasive techniques such as transesophageal echocardiography.