Katsuhiko Tsujioka

Multivariate analysis of risk factors for stroke eight-year follow-up study of farming villages in Akita, Japan

Akita Prefecture has an especially high mortality rate from stroke, and its age-adjusted death rate from stroke is the highest in Japan. We have carried out an epidemiological survey of cardio- and cerebrovascular diseases (CVD) in farming villages in this prefecture since 1963, with a response rate of 84%. During our 8-year follow-up, 94 new stroke cases were observed among 1,814 subjects. Multiple logistic function analysis was carried out on nonstroke and stroke cases from subjects aged 40 to 69 years at time of initial examination, in order to clarify the risk factors for stroke. The analysis used eight variables: age, sex, systolic blood pressure, obesity index, urinary sugar, urinary protein, serum total cholesterol, and total protein. The results showed that hypertension was the most important risk factor for stroke. However, regarding cholesterol, multivariate analysis showed that among men and women aged 40 to 69 years at entry, subjects with low serum total cholesterol levels were more prone to cerebral hemorrhage, but that serum cholesterol level had no weight as a risk factor for cerebral infarction. These results correspond well with the observed fact that stroke incidence or death rate in Japan is higher in populations with high prevalence of hypertension and low concentration of cholesterol, and also with the fact that death rate from hemorrhage declines with the increment of serum total cholesterol and the westernization of diet.

Functional Characteristics of Intramyocardial Capacitance Vessels and Their Effects on Coronary Arterial Inflow and Venous Outflow

The intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. The estimated value of unstressed volume was about 5% of the left ventricular mass, and the time constant in relation to ordinary capacitance was about 1 s, although both are pressure-dependent. The coronary venous outflow was closely related to the total displaceable blood volume stored in the intramyocardial capacitance vessels, i.e., the more intramyocardial blood volume, the more coronary venous outflow. On the other hand, the diastolic coronary arterial inflow was decreased when the blood volume in the intramyocardial vessels increased above the unstressed volume. This may be important as a mechanical control of the coronary circulation system.

Blood Flow in Coronary Vessels

The anatomical characteristics of the coronary circulation are summarized (Gregg and Fisher 1963; Berne and Rubio 1979; Marcus 1983) as follows: Two major coronary arteries (Fig. 6.1), a right and left, arise respectively from the right anterior and left anterior aortic sinuses of Valsalva. The left main coronary artery in adult humans is about 4–5 mm in diameter, and the mean length of this artery is 1.3 cm. The right coronary artery as its origin is about 3–4 mm in diameter. The left anterior descending coronary artery and its diagonal branches in humans perfuse most of the left ventricular myocardium. The septal perforating branches from the left anterior descending artery supply the interventricular septum. The left circumflex coronary artery follows the respective auriculoventricular groove to the left and terminates at a variable distance from the posterior longitudinal sulcus. In contrast to humans, the circumflex coronary artery in the dog supplies the largest area of cardiac muscle. The right coronary artery follows the respective auriculoventricular groove to the right. In man it usually (in about 80%) reaches the posterior sulcus and becomes the posterior descending artery.

Characteristics and Possible Cause of Instantaneous Velocity Waveforms in Small Coronary Arteries and Veins

Instantaneous blood flow velocities were measured in coronary arteries and veins of both the left and right ventricles and the left atrium by our laser Doppler velocimeter (LDV) with an optical fiber. The phase opposition of velocity waveforms between coronary arteries and veins was observed consistently in all coronary arteries and veins if the velocity waveform reflected an intramyocardial velocity waveform by minimizing the effect of capacitance of large epicardial vessels. The systolic component of the velocity waveform in the right coronary artery was slightly larger than that in the left coronary artery. A sharp decrease in atrial arterial flow was observed during atrial contraction and atrial vein flow was systolic predominant. The nature of force of myocardial contraction may be closely related to myocardial contractility, as the velocity waveforms are similar despite large differences in cavity pressure.