Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal medicine. School of medicine, University of South Dakota.
Transesophageal Doppler echocardiography was first reported by Side and Gosling in 1971, they used a dual element construction mounted on a standard gastroscope to obtain continuous wave Doppler information about the velocity of cardiac blood flow (Side and Gosling 1971).
It was also reported by Daigle et al. in 1975 who described pulsed wave Doppler interrogation from within the esophagus (Daigle et al., 1975).
In 1976, Frazin et al. reported transesophageals M-mode echocardiography as a means of assessing ventricular function. Their work did not attract clinicians because of the problems associated with swallowing of the probe in conscious patients (Frazin et al., 1976).
Since this was not a problem in unconscious patients, further research was directed towards intra-operative monitoring of left ventricular function. This was mainly undertaken by Japanese investigators and particularly by Matsumoto and his colleagues (Matsumoto et al., 1980).
In 1977, Hisanaga et al. reported cross section real time imaging using a scanning device that consisted of a rotating single element in an oil-filled balloon mounted at the tip of a gastroscope (Hisanaga et al., 1977).
One year after their first report, Hisanaga et al. also described a linear mechanical scanner that was suitable for transesophageal echocardiographic studies but its applications were limited due to rigidity of the mechanical sector scanning device (Hisanaga et al., 1978).
To overcome the logistical difficulties of introducing a rigid endoscope, transducers were subsequently mounted on flexible endoscopes. In 1980 DiMagno et al. first reported the use of a linear phased array flexible endoscope. This instrument had a frequency of 10 MHz and was intended to be used for ultrasonic detection of gastrointestinal disorders such as diseases of the pancreas (DiMagno et al., 1980).
In 1982, Souquet et al. first produced a clinically usable flexible endoscope mounted on a sector phased array two-dimensional echocardiographic transducer that a frequency of 2.25 MHz ? a frequency equal to that of the standard precordial transducer. This represented the definitive breakthrough for the transesophageal approach (Souquet et al., 1982).
The initial applications studied by investigators were outpatient clinic use (Schl?/span>ter et al. in 1982), intra-operative monitoring of air embolism in upright neurosurgical operations (Cucchiara et al. in 1984) and intra-operative monitoring of left ventricular function (Kremer et al. in 1982).
In 1989, Currie reported that introduction of high resolution TEE probes with color flow Doppler capability received much interest and established the beginning of the era of ?invasive echocardiography? (Currie 1989). Currently, between 7-10% of all precordial examinations are completed by TEE examination (Seward 1994).
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