to the editor: We thank Marabotti and colleagues (1) for their letter addressing the use of subcostal echocardiographic imaging to assess right ventricular systolic function in our recent work regarding glossopharyngeal insufflation. The major concerns raised in the letter were twofold: that radionuclide ventriculography, rather than echocardiography, is the most accurate assessment of right ventricular volume, and that the volumes obtained in our calculations were significantly discordant from those obtained in the left ventricle and much smaller than expected in healthy persons.
We considered several factors before selecting echocardiography to evaluate ventricular function in the elite divers. First, our primary interest was the change of ventricular function induced by glossopharyngeal insufflation, rather than a true measure of ventricular size and volume. In this respect, each diver at rest acted as his/her own control, and ventricular volume calculations were strictly used to demonstrate the degree of change in ventricular function. Second, subcostal echocardiographic assessment of right ventricular function has shown good correlation with radionuclide angiography in the past (2). Third, echocardiography allowed rapid, real-time imaging of cardiac function before, during, and after glossopharyngeal insufflation. In our hypothesis-generating investigation, it was the only noninvasive modality that achieves appropriate temporal and visual resolution for the requisite analysis while sparing participating divers ionizing radiation. Despite the known shortcomings of subcostal echocardiographic imaging when studying the geometrically complex right ventricle, it was still a strong modality to detect marked changes in ventricular function, and we firmly believe in the validity of the observed decline in right and left ventricular function during glossopharyngeal insufflation.
The principal message in our study was that, for the first time, decrease in biventricular function due to glossopharyngeal insufflation has been demonstrated by direct cardiac imaging. We agree with Marabotti and colleagues that pursuing confirmation of our findings with “gold-standard” evaluation of right ventricular function is worthwhile. Perhaps more importantly, we believe, are future investigations to clarify the underlying mechanisms by which glossopharyngeal insufflation compromises cardiac performance.
- Copyright © 2008 the American Physiological Society