3-D Evaluation of Dyssynchrony

The relationship between left ventricular dyssynchrony and heart failure has been well demonstrated in recent medical literature.⁷ Dyssynchrony contributes to heart failure by causing blood to undulate between earlyand late-contracting regions of the left ventricle rather than contributing to cardiac output, which decreases ventricular efficiency and performance. Cardiac resynchronization therapy targets ventricular dyssynchrony and has been shown to improve symptoms and quality of life.⁸ A recent multicenter study found that congenital heart disease patients undergoing resynchronization exhibited a significant increase in mean ejection fraction; however, long-term results regarding percentage of responders and degree of benefit are not yet available. ⁹

Echocardiography has emerged as the modality of choice for assessment of dyssynchrony. Using FV-3-DE data sets, dyssynchrony can be assessed at the bedside with sophisticated 3-D software, which allows for temporal analysis of dispersion in segmental ventricular volumes. The process involves calculating the time from end-diastole to the minimal systolic volume for each ventricular segment. The dispersion of these times can be used to create an index of dyssynchrony.¹⁰ A recent study found that adult patients with dilated cardiomyopathy had significantly higher 3-DE indices of dyssynchrony compared with healthy controls and that 3-DE dyssynchrony indices had a strong negative correlation with ejection fraction.¹¹

3-D Color Doppler

Another promising aspect of 3-DE is 3-D color Doppler. As with 3-DE imaging of cardiac structures, the ability to acquire 3-D color Doppler information has the potential to significantly enhance quantitative assessment of blood flow through cardiac structures. Jets of valvular insufficiency can be captured in their entirety, rather than in sequential 2-D sweeps. Their direction, orifice size, and extension can be easily appreciated. Moreover, the regurgitant orifice area can be measured directly and the flow through the orifice can be calculated, providing the regurgitant volume.¹² With this same technology, the flow through the aortic or pulmonary valve can be measured providing a direct, non-invasive measurement of cardiac output.¹³ A portable, rapid, non-invasive method for quantifying cardiac output could have a profound effect on the care of critically ill patients and improve our ability to follow patients with cardiac failure.

Future Considerations

There is no doubt that 3-DE has become an important part of the echocardiographer’s imaging armamentarium and is quickly finding mainstream clinical acceptance. It is likely that the rate of technological advancement will play an important role in determining the timeline over which 3-DE is completely integrated into daily practice. Current quantitative chamber analysis is somewhat limited for abnormal ventricular morphology, which is not uncommon in congenital heart disease. This represents a hurdle for widespread application of quantitative 3-DE to our patient population.

The advent of a reasonably sized, affordable holographic display will also be an exciting addition to 3-DE technology. This would allow the cardiac surgeon and invasive cardiologist to navigate the heart using a realtime 3-D holographic display. In the catheterization laboratory, this could lead to a significant decrease in fluoroscopy use and improved visualization of device implantation. There is also the potential to guide intracardiac surgery and lessen the need for cardiopulmonary bypass. These and other exciting developments will allow us to fully exploit the power of this unique modality and improve patient care.