Masayoshi Yoh

Assessment of regional wall motion abnormality without contrast medium by digital subtraction angiography using Fourier analysis.

Digital subtraction angiography (DSA) offers an image which is linearly amplified and logarithmically subtracted. Therefore, the method makes it possible to evaluate a small difference in X-ray absorption by the cardiac silhouette during one cardiac cycle, even without using contrast medium. Utilizing this advantage, we have developed a new approach to evaluate regional left ventricutar (LV) function by DSA without contrast medium [1]. Digital subtraction images of the left ventricle with and without contrast medium were obtained in the right anterior oblique projection with a Toshiba Digiformer-X. Using an image-processing computer (Toshiba GMS-55A), LV time-density curves were constructed for one cardiac cycle. Phase analysis was performed using Fourier analysis [2] in order to determine regional LV wall motion abnormality. The pattern of the time-density curve for one cardiac cycle without contrast medium was nearly identical to the LV volume curve with contrast medium (Fig. I). The phase image without contrast medium was comparable to that with contrast medium (Fig. 2). Compared with conventional cineangiography, the diagnostic accuracy of regional wall motion abnormality by phase analysis without contrast medium

Abnormal Throughput Coronary Flow in Syndrome X

To elucidate the mechanism of ST segment depression in patients with syndrome X, myocardial blood flow and myocardial O2 and lactate uptake were evaluated in 25 patients who had exhibited chest pain but had normal coronary arteriograms. Fourteen of the patients had chest pain and ST segment depression in an exercise stress test (SX), while the remaining 11 did not exhibit either of these symptoms (control). Atrial pacing induced significant ST segment depression in all patients with SX and did not do so in controls. There was no evidence of coronary artery spasm produced by intravenous administration of ergometrine maleate in any patients. Myocardial blood flow was measured with a Webster’s thermodilution catheter. Coronary flow reserve was defined as the increase occurring in coronary flow after the administration of intravenous dipyridamole (0.56 mg/kg), divided by coronary flow at rest. After the administration of dipyridamole, the coronary flow reserve was 2.70 in the SX group and 2.90 in the controls; this difference was not significant. During atrial pacing, there was a reduction of myocardial lactate uptake and a rise in left ventricular end-diastolic pressure in the SX group, but not in the controls. Oxygen saturation in coronary sinus blood did not change significantly in the controls, while it rose significantly in SX patients.

Functional myocardial perfusion imaging by digital subtraction coronary arteriography: Comparison of contrast decay rates in normal and ischemic myocardium

Recent advances in computer technology have enabled the generation of time-density curves of myocardial contrast medium after injection into the coronary artery, using digital subtraction angiography (DSA). Utilizing this advantage, we have described a new technique to assess regional myocardial blood flow in computerized washout analysis of the timedensity curve [1, 2]. T~/2, the contrast decay half-life derived by this technique, showed a good linear correlation with great cardiac vein flow measured by the thermodilution method and a curvilinear relationship with percentage stenosis of the left anterior descending coronary artery (LAD), as shown in Fig. 1. Therefore, T~/2 values proved to be a valuable index of regional myocardial blood flow. In the present study, we have further developed a functional imaging of T~/2 values to visualize the regional myocardial blood flow. After injecting the contrast medium into the LAD, a serial myocardial image was obtained for 20 s in the right anterior oblique projection and this image was then enhanced digitally with the DSA apparatus (TOSHIBA Digiformer X). It was then transmitted to the image-processing computer (TOSHIBA GMS-55A) and was sequentially digitized into a 64 x 64 pixel matrix window. The epicardial outline was drawn by an observer using a computer-aided outlining technique, and a time-density curve of each pixel was generated in the myocardium perfused by the LAD. The descending slope of the time-density curve was fitted to a monoexponential function with a standard least-square method (Fig. 2). The functional image was constructed to present the absolute value of the exponential decay rate constant of the respective pixel in one of four different colors--red, yellow, green, and blue. The exponential decay rates