Fumihiko Utsu

Quantitative evaluation of regional myocardial blood flow by videodensitometric analysis of digital subtraction coronary arteriography in humans.

Videodensitometric analysis of digital subtraction coronary arteriography, a new approach for calculating contrast disappearance half-life (T1/2), was assessed in determining regional myocardial blood flow quantitatively. Forty-one patients with coronary artery disease and 12 with angiographically normal coronary arteries underwent digital subtraction coronary arteriography by manual injection of contrast medium into the left main coronary artery. The T1/2 was calculated from a time-density curve generated in the four sectors of the myocardium perfused by the left anterior descending coronary artery. The mean T1/2 value of the four sectors correlated inversely with the great cardiac vein flow measured by the thermodilution method (r = -0.89), and appeared to be a reliable index of myocardial blood flow. The relation of mean T1/2 with percent stenosis of the left anterior descending coronary artery was curvilinear (r = 0.88) and an abnormally high T1/2 occurred in patients with coronary stenosis greater than 75%. In patients with comparable stenosis of the left anterior descending artery, the apical T1/2 was significantly increased in those with impaired apical wall motion, while it was significantly decreased in those with coronary collateral vessels. These findings suggest that regional myocardial blood flow begins to decrease in vessels with greater than 75% stenosis, and that myocardial contraction and collateral flow are additional factors that modify regional myocardial blood flow. Thus, the contrast disappearance half-life (T1/2) derived by computerized washout analysis of digital subtraction coronary arteriograms proved useful as an index for quantitative evaluation of regional myocardial blood flow.

Termination of Ventricular Tachycardia by an Implantable Atrial Pacemaker and External Pacemaker Activator

An atrial pacemaker was implanted in a patient who had dilated cardiomyopathy, sinus node dysfunction, and drug‐resistant ventricular tachycardia (VT). VT episodes were terminated by atrial overdrive pacing using an implanted pacmaker and a newly developed handheld external programmer/transmitter. Although successful cases of termination of intractable VT by ventricular pacing have recently been reported, the ventricular method might increase the risk of accelerating VT. Atrial overdrive pacing is a safer method since it minimizes the possibility of tachycardia acceleration and, combined with antiarrhythmic drugs, it appeared to be a unique and useful approach for the treatment of drug‐resistant VT.

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

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