In isolated ejecting cat hearts, the pumping ability of the left heart was described quantitatively by the relationship between mean left ventricular pressure and mean left ventricular output. This relationship was determined by making the heart eject against a series of different loads on a beat-to-beat basis. Left ventricular mean pressure-mean output relationships of control and potentiated beats (at the same end-diastolic pressure) have a common intercept on the output axis but diverge toward the pressure axis. When the mean pressure values of the potentiated beats in a given experiment are multiplied by a single factor, superposition of the two relationships is obtained. A change in left ventricular end-diastolic pressure caused a more parallel shift of the left ventricular mean pressure-mean output relationship. Here, superposition could be obtained by using one multiplication factor for the mean pressure data and one for the mean output data of the relationship found after the change in end-diastolic pressure. We concluded that, using the left ventricular mean pressure-mean output relationship, changes in cardiac pumping ability caused by given changes in inotropic state and ventricular end-diastolic volume can be quantified by one or two multiplication factors, respectively.

Animals↗

PubMed1977

How does a change in end-diastolic volume alter pumping ability of the left heart [proceedings]?

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Animals↗

PubMed1976

Reflection in the systemic arterial system: effects of aortic and carotid occlusion.

Experiments were performed in seven closed-chest anaesthetized male dogs to determine the role of pulse wave reflection in the pattern of flow and pressure in the ascending aorta. Ten days after implantation of an electromagnetic flow transducer around the ascending aorta a balloon catheter was placed in the descending aorta via the femoral arteries. At the same time a tip manometer was introduced into the ascending aorta. Aortic occlusions at three different sites caused pressure pulses with secondary systolic rises and flow pulses with biphasic deceleration. Secondary rises occurred 45 +/- 9.0 ms after the initial pressure rise for high aortic occlusion; this time was 75 +/- 8.5 ms for occlusion at the level of the diaphragm and 114 +/- 16.5 ms for occlusion near the level of the renal arteries. These times approximate the times in which the pulse travels from the tip manometer to the inflated balloons and back. Forward and reflected pressure and flow waves were calculated from reflection coefficients. Aortic occlusion caused larger reflected waves and the recorded wave forms were caused by the summation of forward and backward waves, the latter contributing the secondary pressure rise and the increased flow deceleration. Occlusion of both carotid arteries showed no specific reflection site but reflected waves were larger. This increased reflection can probably be explained as the result of greater total reflection from distributed sites under increased peripheral resistance.

Animals↗

PubMed1976

The pumping ability of the left heart and the effect of coronary occlusion.

In an isolated preparation of cat heart we studied the pumping capacity of the left heart while left atrial filling pressure was kept constant. We used the source impedance concept to quantify the pumping capacity. In this source impedance concept the relation between left ventricular output and left ventricular pressure is given by the formula (see article) where Zs = source impedance, Plv = left ventricular pressure, Iao = flow in the ascending aorta, and omega = 2pif, f being frequency.. The pressure obtained at zero flow is called the hydromotive pressure (HMP). Only the mean values of pressure and flow were studied. We studied the behavior of 10 hearts in three different experimental situations and in the following sequence: (1) control conditions, (2) after ligating a part of the left coronary arterial system, and (3) after restoring left ventricular output to control level by raising left atrial filling pressure. It was found that source resistance was not significantly different in the three situations but that mean hydromotive pressure (HMP) was significantly lower after ligation of a part of the left coronary arterial system. It was concluded that the decrease in pumping capacity of the left heart after infarction can be compensated for almost completely by an increase in left atrial filling pressure. This compensating mechanism therefore seems to be very efficient.

Animals↗

PubMed1976