Download Ultrasound and Imaging: Are we crossing borders?

“ULTRASOUND AND IMAGING:ARE WE CROSSING BORDERS”
Dr. Chirojit Mukherjee M.D.
Senior Consultant and Fellowship Program Director
Department of Anesthesiology and Intensive Care Medicine II
Heartcenter, University Leipzig,
GERMANY
A: INTRACARDIAC ULTRASOUND
Intracardiac echo(ICE) has been in practice since late 1970s.However with the advent of phased array
transducers with steering capability ICE has undergone major modifications since late 80s(1,2).
ICE, presently in use , has 5 variants(3).
1 Boston Scientific Corp,San Jose,CA,USA: 9 French catheter with 9MHz frequency.
2 AcuNav,Biosense Webster, Inc, Diamond Bar, CA, USA: 8-10 French catheter with four way
manoueverability of catheter tip.
3 St. Jude Medical, St. Paul, MN, USA: Clear ICE Hockey stick catheter with steerable capacity.
4 St. Jude Medical, St. Paul, MN, USA: EP View has a flexi tip with 2-8MHz frequency for better
penetration
5 Biosense Webster,CA,USA : 10 French catheter with phased array transducer and the tip of the
catheter has a magnetic sensor.
Figure showing AcuNav 10F,Acunav 8F and Soundstar 10F catheters.
The newest addition is the ACUSON AcuNav V: It is a real time three dimensional volume
intracardiac imaging armamentarium. It is not commercially available in Europe and USA and is in
experimental phase.
The potential benefits of ACUSON AcuNav V:
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
ix)
10F catheter with 90cm insertable length
22 x 90 degree real-time volume
Upto 40 vps acquired in 3D B-mode
Upto 20 vps acquired in 3D Color –mode
Pulsed wave and Color wave Doppler
Real time color with 3D possible in the same window
On line “cutting and cropping” possible with real time loops
Catheters being experimented for both intrafemoral and intrajugular access with varying
lengths.
Although in experimental stage , using only analgo-sedation may be an added
advantage for performing interventional procedures.
The visualization of both the anatomical and physiological changes during any procedure can be well
documented. The data obtained can be “on-line” imaged with possible cropping facility using
Siemens SC 2000 ultrasound platform.
SC 2000 Ultrasound platform from Siemens AG ,Erlangen,Germany.
Figure demonstrating catheter tip being placed in right ventricle using femoral access.
Figure demonstrating the “position of orientation” showing right atrium, right ventricle and tricuspid
valve using ICE.
The advantages presently associated with using ICE:
i Able to use a “flashlight” inside the heart
ii The anatomy of the heart is visualized in a “real-time” status
iii Real time 3D ICE is expanding its horizon in interventional procedure
iv Less exposure to radiation and contrast medium specially in trans-catheter procedures (4)
Limitations:
i Presently limited to electrophysiological and cardiology intervention procedure
ii Vascular complications at the site of puncture (5)
iii Incidence of arrhythmias and thrombus formation at the catheter tip can be minimized by
manipulation of catheter tip and reduction in procedure time.
B: IMAGING BEYOND BORDERS
The anesthetist is being challenged in the Hybrid operating room or modernized/modified cath lab
for understanding the basics of imaging. The routine work of an anesthetist is to provide anesthesia
,sometimes pain management and in specialized centers to provide echocardiographic services.
Working in image based interventions has opened a new horizon for the anesthetist to comprehend
the fluoroscopic imaging and to interpret the images, putting knowledge into routine clinical
practice.
Therefore “imaging beyond borders” is imperative for an anesthetist working in interventional
procedures for eg. Intraoperative multi detector computerized tomographic scan (MDCT) for
transcatheter procedures gives a detailed information of the structure and function of the aortic root
(6). It not only gives information about the size of the aortic annulus but also provides measurements
of the distance of the coronary ostium from the annulus of the aorta. Real time 3D echocardiography
is an armamentarium which a cardiac anesthetist is accustomed for using in the operating room. The
acquisition of the fluoroscopic images and cardiac MDCT is being merged into the same platform,
using an overlay technique, to provide accurate information of the cardiac structure . The future of
imaging is to combine all the 3 modalities of fluoroscopy, MDCT and real time 3D TEE and project it
into the same platform.
The 2nd generation intraoperative CT scan provides:
i 3D reconstruction of the aortic root using automatic segmentation
ii Identification of coronary arteries
iii Identification of basal attachments of leaflets along with lowest portion of sinuses
iv Relation to left ventricular outflow tract
The concept of a dynamic heart model is on it´s evolution. The principle behind it is the development
of a patient specific valve model based on volumetric sequences obtained from different phases of
cardiac cycles. These are obtained from imaging modalities of MDCT and TEE . The dynamic motion
of the valves is learned through detection of anatomical landmarks, using an algorithm. This dynamic,
rapid , complex and physiological motion of the valves is then transported to the physiological valve
model and is further enhanced using automated boundary technique (7).The end result is an exact
replica of the native valve imaged through a patient specific model obtained through volumetric
sequences of the cardiac cycles. The morphological and physiological quantification of the
healthy/diseased valve will provide a long term follow-up with accurate diagnosis of the disease
process. The future of “image-guided” procedures in hybrid suite and the drawbacks associated with
limited imaging is expected to overcome using this concept. Designing a valve for percutaneous
intervention, planning a surgical procedure or the shortcomings of a long term follow-up of an
ongoing disease process can be dealt, by integrating such imaging modalities in routine clinical
practice.
Figure showing physiological model of the heart (takes into account both the anatomy and
hemodynamic state )
Figure showing model based valve assessment and quantification of mitral valve.
References:
1. Kort S: Intracardiac echocardiography: Evolution, recentadvances, and current applications. J Am
Soc Echocardiogr 2006;19:1192–1201.
2. Maloney JD, Burnett JM, Dala-Krishna P, et al: New directionsin intracardiac echocardiography. J
Interv Card Electrophysiol 2005;13(Suppl 1):23–29.
3 Ali S, George LK, Das P, Koshy SK. Intracardiac echocardiography:clinical utility and application
Echocardiography. 2011 May;28(5):582-90
4 .Bartel T, Bonaros N, Müller L, Friedrich G, Grimm M, Velik-Salchner C, Feuchtner G, Pedross F,
Müller S. Intracardiac echocardiography: a new guiding tool for transcatheter aortic valve
replacement. J Am Soc Echocardiogr. 2011 Sep;24(9):966-75.
5 Hijazi ZM, Shivkumar K, Sahn DJ: Intracardiac echocardiography during interventional and
electrophysiological cardiac catheterization. Circulation 2009;119:587–596.
6. Kempfert J, Falk V, Schuler G, Linke A, Merk D, Mohr FW, Walther T. Dyna-CT during
minimally invasive off-pump transapical aortic valve implantation.Ann Thorac Surg. 2009
Dec;88(6):2041.
7 Ionasec RI, Voigt I, Georgescu B, Wang Y, Houle H, Vega-Higuera F, Navab N, Comaniciu D.
Patient-specific modeling and quantification of the aortic and mitral valves from 4-D cardiac CT and
TEE.IEEE Trans Med Imaging. 2010 Sep;29(9):1636-51