In 20 open-chest dogs intramyocardial pressure was measured simultaneously in two regions: a) in the normal myocardium (IMPsp) b) in a controlled perfused area of the myocardium, supplied by a cannulated coronary artery (IMPp). The preparation permitted the study of the influence of contractility, ventricular pressure and coronary blood flow on IMP. 1. A 47% change in coronary flow with a 26% change in coronary perfusion pressure results in changes of systolic and diastolic IMPp of 14% and 29% respectively. These effects can be explained by variations of intramural fluid content and, hence, of diastolic fiber length. 2. Changes of systolic ventricular pressure (mean 27%) by preload variations result in a mean change of systolic IMPsp of 19% and of systolic IMPp of 11%. 3. Changes of systolic ventricular pressure (mean 33%) by afterload variations augment IMPsp by 30% and IMPp by 13%. 4. The increases of IMPsp and IMPp induced by instantaneous changes of afterload are equal. The most important determinants of IMP are myocardial contractility, coronary perfusion and intraventricular pressure. The influence of coronary perfusion and ventricular pressure on IMP is of the same order of magnitude.

Animals↗

PubMedDate not supplied

[Problems of angiographic determination of diastolic pressure-volume relationship of the left ventricle (author's transl)].

The problems of determination of the left ventricular diastolic pressure-volume relationship were demonstrated by analysis of post-extrasystolic beats and of two consecutive normal beats. Quantitative high-speed left ventriculography with simultaneous pressure recording was performed in 16 patients with reduced left ventricular function. The diastolic pressure-volume relationship was evaluated using the formula of Diamond and Forrester (p = b . e(a) V + c) (formula [1]) and a simplified expression (p = b' . e(a') . V) (formula [2]), usually used. The parameters b, a and c of formula (1) showed significant but nonuniform alterations. The parameters b' and a' of formula (2) did not change significantly. The residual sums of squares of the approximation using formula (1) were about 8% less than those of formula (2); i.e.: the measured left ventricular pressures and volumes could be fitted more exactly by formula (1). Two pressure-volume-curves with identical slopes but different operating pressure-levels could not be described by formula (2), because in this case the computed slope of the pressure-volume curve was influenced by shifts of the operating pressure-level. The results show that the diastolic pressure-volume relationship cannot exactly be described by formula (2). The application of formula (1) proved the angiographic determination of left ventricular volumes to be insufficient for the evaluation of the diastolic pressure-volume relationship.

Angiography↗

PubMedDate not supplied

Assessment of left ventricular function by a power index: an intraoperative study.

To investigate whether left ventricular performance can be described independent of loading conditions, twelve patients underwent intraoperatively two cineangiographies of the left ventricle with simultaneous pressure recordings. The first ventriculography was performed with ejecting left ventricle without assistance by the extracorporeal circulation. The second one was performed with ejecting left ventricle partially unloaded by the extracorporeal circulation. Myocardial perfusion pressure (mean aortic pressure) was held constant. Due to this procedure marked decreases in preload (end-diastolic wall stress: -54%) and modest changes in afterload (mean systolic wall stress: -23%) were achieved. End-diastolic volume index was reduced from 84 ml/m2 to 57 ml/m2, whereas end-systolic volume index decreased slightly from 33 ml/m2 to 29 ml/m2. Left ventricular end-diastolic pressure decreased from 12 mm Hg to 7 mm Hg, while peak pressure remained nearly unchanged. Usual parameters of ejection phase (EF, Vmw) as well as power per wall volume (PW) were markedly affected by unloading. In contrast to these parameters, the power index (PI), i.e., the ratio of power per wall volume and end-diastolic wall stress, remained unchanged when left ventricular preload was reduced: PI under control: 5.2 +/- 1.8 sec-1; PI under unloading: 5.2 +/- 1.5 sec-1. This power index can easily be determined from routine angiographies. It may provide a new approach to the assessment of left ventricular function in man.

Adult↗

PubMedDate not supplied

Measurement of flow velocity in the model circulation by videodensitometry. Methodological investigations.

The relation between videodensitometrically measured front velocity and electromagnetically assessed flow was examined in a circulatory model with continuous as well as pulsatile flow (89 experiments). The diameter of the tubes in the videodensitometric measuring section was 0.305 to 0.518 cm. A linear correlation was proved in flow velocities up to Reynold's number Re = 225. The exact flow, measured electromagnetically, was overestimated in continuous flow by 21% (r = 0.99, Syx = +/- 14.5 ml/min) and in pulsatile flow by 24% (r = 0.98, Syx = +/- 20.8 ml/min). In view of these results the phasic and average flow can be calculated accurately using videodensitometric techniques.

Blood Flow Velocity↗

PubMedDate not supplied

Reliability of intraoperative flow measurements to determine early graft patency with simultaneous introduction of a new method for distal coronary artery run-off capacity.

Intraoperative measurements of blood flow were made in 44 patients in whom a total of 112 venous bypass grafts were inserted. Blood flow through the graft was measured by a standard electromagnetic device as well as by a new method, consisting of a roller pump run-off system. At an average of 5 months after operation all patients underwent control coronaro-angiography. Overall patency-rate was 86.6%. Using the standard method mean flow in the patent grafts was 78 ml/min and 39 ml/min in the occluded grafts. Using the new run-off method mean flow in the patent grafts was 142 ml/min and 78 ml/min in the occluded grafts. It is concluded that measuring distal coronary artery run-off capacity provides a reliable index for predicting patency rate. For several reasons roller-pump run-off measurement has advantages over the generally used electromagnetic measurements.

Adult↗