Author + information
- Bushra S. Rana, MD,
- Martyn R. Thomas, MD,
- Patrick A. Calvert, MD (, )
- Mark J. Monaghan, PhD⁎ and
- David Hildick-Smith, MD
- ↵⁎Research and Development, Papworth Hospital NHS Foundation Trust, Papworth Everard, Cambridge CB23 3RE, United Kingdom
We thank Dr. Sharma and colleagues for raising the importance of transcranial Doppler ultrasound (TCD). The clinical significance of a patent foramen ovale (PFO) is based not simply on shunt size, but on multiple factors, such as the clinical scenario (e.g., Valsalva-type maneuver at the time of the event) and the presence of high-risk anatomy (atrial septal aneurysm and a persistently open PFO).
Both transthoracic echocardiography (TTE) and TCD are comparable in the diagnosis of a shunt (1,2). Body positioning and maneuvers can be performed adequately by the former and is our preferred method for assessing the presence of a PFO, rather than transesophageal echocardiography due to the reasons highlighted by Dr. Sharma and colleagues. TCD may be useful where TTE acoustic windows are limited, but, crucially, TCD cannot differentiate the level of the shunt (cardiac or pulmonary). The issues with contrast behavior and bubble destruction hold true whether TTE or TCD is used. Unlike TCD, where the operator remains oblivious, these issues can be detected and overcome during TTE. Direct visualization of the heart by TTE permits: 1) confirmation of opacification of the right atrium with contrast before Valsalva release; 2) confirmation of an adequate Valsalva maneuver (bowing of atrial septum toward the left atrium); 3) timing of the appearance of contrast passage with direct visualization into the left atrium on release of Valsalva (or other maneuvers); 4) detection of any late contrast appearance suggesting transpulmonary passage; and 5) identification of an extensive Eustachian valve that may impede contrast filling of the lower right atrium, preventing passage across a PFO. All these factors make TTE with bubble contrast a superior choice, in our opinion, for the diagnosis of PFO.
Thus, although TCD remains a sensitive tool to identify the presence of a shunt, we believe that TTE represents a superior imaging modality in the diagnosis of PFO.
- American College of Cardiology Foundation