Abstract
In a series of recent articles 1 , 2 , 3 the blood flow from moment to moment in the various branches of the coronary arteries has been established by constructing differential pressure curves from a combination of the central and peripheral coronary pressure curves (after the latter had been raised to their proper ordinate value). The method, however, is time consuming and what is more important, may miss altogether very rapid and transient changes in coronary flow such as, for example, might follow nerve stimulation, since the necessary data for constructing a flow curve can not be obtained in less than 10–20 heart beats.
To offset these drawbacks, a simple method (requiring the registration of only 1–2 heart beats) is suggested for determining changes in diastolic resistance and in most cases this can be used as an index of qualitative changes in coronary diastolic blood flow.
The experimental setup and method are as follows: After opening the chest and pericardium of an anesthetized dog, optical records of aortic and coronary pressures are taken by inserting manometers of adequate frequency into the aorta through the subclavian artery and into a suitable side branch of a coronary artery. An electromagnetic clamp is placed on the coronary artery central to its recording manometer. The heart is driven by an artificial pacemaker connected to the right auricle. The clamp and pacemaker are so synchronized (by a device to be described later) that the artery is clamped in successive beats only during the latter part of diastole. Since it has already been established (1) that the diastolic coronary resistance remains unchanged during the latter portion of diastole, then the rate of pressure drop in the artery (obtained by drawing a tangent to the recorded pressure curve at an arbitrary pressure point) can be utilized as an index of the prevailing diastolic resistance.
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