Keigo Shibao

Impaired myocardial perfusion in patients with hypertrophic cardiomyopathy: assessment with digital subtraction coronary arteriography.

SummaryTo study the clinical significance of abnormal myocardial perfusion in patients with hypertrophic cardiomyopathy (HCM), we performed a computerized washout analysis of digital subtraction coronary arteriograms in 28 patients with HCM and 16 control subjects. The contrast disappearance half-life (T 1/2) was calculated from a time-density curve generated in the four sectors of the myocardium perfused by the left anterior descending coronary artery and the mean T 1/2 was calculated by averaging T 1/2 values for these four sectors. Patients with HCM demonstrated longer T 1/2 in the ventricular septal region than control subjects. Thirteen (46%) of the patients with HCM presented abnormally longer mean T 1/2 values, suggesting impaired myocardial perfusion. Family histories of HCM were more frequent in patients with abnormal mean T 1/2 values (92% vs 47%;p<0.05). On the exercise stress test, patients with abnormal T 1/2 values presented significantly lower exercise tolerance with more frequent exercise-induced ST segment depression (62% vs 13%;p<0.05). However, there were no significant differences between the two groups with regard to ventricular wall thickness, left ventricular end-diastolic pressure, or the severity of systolic narrowing of the coronary arteries.These findings suggest that 13 (46%) of the patients with HCM have impaired myocardial perfusion, which may be a manifestation of intramural coronary artery disease in addition to left ventricular hypertrophy, elevated left ventricular end-diastolic pressure, or systolic narrowing of the coronary arteries. Additionally, significant association of the prolonged T 1/2 with a familial occurrence of HCM and depressed exercise tolerance with ST segment depression imply that impaired myocardial perfusion could be an important inherent pathophysiological state leading to myocardial ischemia during exercise.

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