The effects of intravenous administration of nitroglycerin or dipyridamole on distribution of myocardial blood flow in the heart after coronary underperfusion were investigated. In 18 open chest, anesthetized dogs, flow of the tubing supplying the left circumflex coronary artery (LCA) was reduced and kept constant, and then the drug was given intravenously. Before and after an administration of saline, nitroglycerin (0.04 mg/kg) and dipyridamole (0.2 mg/kg), myocardial blood flow was measured by tracer microspheres (TM). The first and second carbonized 15 mu spheres (TM1 and TM2) were injected into the left atrium and the cannulated LCA perfusion system respectively before medication. Similarly, the third and fourth spheres were given after drug. Thus, by using four different TMs (141Ce, 51Cr, 85Sr, 46Sc) regional myocardial blood flow from the LCA perfusion route (TM2 and TM4) was measured separately from that of the other normally perfused coronary route (TM1 and TM3). The effect of drugs on flow distribution of these two independent routes was measured. The LCA underperfusion produced a significant diminution of regional flow and its end/epi ratio in the LCA territory. Nitroglycerin increased end/epi ratio in the ischemic myocardium in the LCA perfusion route, but dipyridamole increased the normally perfused coronary flow but caused a shift of flow from the ischemic left ventricle to the atria and right ventricle within the LCA territory.

Animals↗

PubMedDate not supplied

The microsphere method facilitates statistical assessment of regional blood flow.

When microspheres are injected into the circulation, they are trapped in the arteriolar or capillary system within various organs. It has been confirmed in animal experiments that the number of microspheres in a myocardial sample approximately follows a Poisson distribution, under adequate experimental conditions. On the basis of this result, we arrived at the following hypothesis: When regional blood flow is measured under a steady state by the reference sample method, the 95% relative error can be approximated by +/- 196 square root 1/v + 1/w, where v and w represent the number of microspheres in blood sample and myocardial sample, respectively. The equation is valid if v and w are greater than 400 and 49, respectively. We obtained an expression of the relation among the percent of increase or decrease in regional blood flow being verified, the probability of increase or decrease, as a statistically significant variation and the number of microspheres in a myocardial sample. An investigator can work out an approximate experimental design using this expression. For instance, when the increase in regional blood flow required for verification is expected to be 20% and he wants this increase to be verified by 90%-probability and as a statistically significant increase, he can predict from this expression that the number of microspheres in a myocardial sample should be 472 and 567 before and after the experimental intervention on the coronary circulation, respectively. The expression is useful as index for experiments involving use of the microsphere method.

Animals↗

PubMedDate not supplied

Effects of collateral circulation on regional myocardial blood flow and left ventricular wall motion (A preliminary note).

The effect of collateral circulation on regional myocardial flow and wall motion of left ventricle was studied on 5 anesthetized dogs with a surgically implanted constrictor on the left circumflex coronary artery (LC). The grade of LC stenosis and wall motion of left ventricle (LV) were determined by cineangiography of the coronary artery and LV at the period of acute and chronic occlusion. Regional myocardial flow was determined by tracer microspheres (TM), labeled with four different isotopes, Sr85, Cr51, Sc46, Ce141. The first TM1 was infused after LC stenosis, TM2 during a temporary complete LC occlusion at the period of acute occlusion; TM3 and TM4 in a similar way 3 to 4 weeks after the acute LC stenosis. Three to four weeks after LC stenosis, i.e. chronic period of occlusion, the degree of LC stenosis progressed from 70--80% to 100% occlusion, but collateral flow and collateral vessels to the ischemic LC area were increased together with an improvement of wall motion of the ischemic LC area. The results may support the idea that collaterals may be an effective compensatory mechanism for ischemia. In contrast to an increase of collateral flow to the ischemic LV free wall in all five dogs, an increase to the posterior papillary muscle was found only in two out of five dogs.

Animals↗

PubMedDate not supplied

Precordial electrocardiographic map using the IBM-Bonner program.

The precordial electrocardiographic map may be useful for non-invasive assessment of the extent of the acutely infarcted myocardium. Rapid and serial precordial electrocardiographic maps also may be useful to evaluate the effects of intervensions of drugs and efforts on the ischemic myocardium. In this study, the IBM-Bonner program was applied to produce a system for the precordial electrocardiographic map. Six electrodes at one intercostal space were moved in parallel from the second to the seventh intercostal space. Thus electrocardiograms (ECGs) could be recorded from 36 precordial sites, 6 x 6 matrix, and analyzed using the IBM-Bonner program. The measured values of the ECG waveform make feasible the automatic procurement of the precordial electrocardiographic map. Our mapping program can be used readily and anywhere the IBM-Bonner program is in use.

Computers↗

PubMedDate not supplied

A computer program for detection of segmental contraction abnormalities by the left ventricular cineangiogram.

A computer program which enables detection of segmental abnormalities of the left ventricular contraction was developed using the principles of Leighton et al. [Circulation 50 (1974) 121-127]. A film projector, a digitizer, a graphic display and a mini-computer are used. The end-diastolic (ED) and end-systolic (ES) left ventricular silhouettes are traced from 30 degrees right anterior oblique cineangiograms projected on a screen of the film projector. The program determines semi-automatically both apexes and longitudinal axes of the left ventricle. Lines [(N-1) less than or equal to 60] are drawn perpendicular to longitudinal axes, dividing longitudinal axes into equal N segments, respectively. These perpendicular lines are extended to intersect ED and ES silhouettes at 2(N-1) points, respectively. The distances along each of 2(N-1) hemiaxes are defined as short axes [S-EDi and S-ESi, i = 1-2(N-1)]. Segmental wall contractions are expressed as a percentage of the distance from S-EDi to S-ESi, and displayed as a graph with normal values (mean +/- 2 SD). The presence and extent of segmental contraction abnormalities can be evaluated quantitatively by observing a percentage of segmental wall contractions. This program greatly facilitates a correct diagnosis in clinical use.

Cineangiography↗

PubMedDate not supplied

Analysis of low density lipoprotein apheresis: post-treatment rebound using mathematical models.

Double membrane low density lipoprotein (LDL) apheresis (thermofiltration) was applied to treat six hyperlipidaemic patients and five controls 14 and 5 times, respectively, and post-treatment plasma LDL cholesterol (LDLc) concentration rebound was measured. To simulate the rebound, a nonlinear model (NLM) was developed. It consists of two compartments representing plasma and liver. LDLc uptake by the liver is described by receptor-independent and by receptor-mediated transport as controlled by the liver cholesterol concentration. NLM analysis of patient data resulted in pre-treatment fractional catabolic rate (FCR) for LDLc of 0.19 day-1 and the maximum FCR for LDLc of 0.26 day-1 on the 4th day. NLM showed that in patients and controls the post-treatment LDL synthesis rate rose by 6% to 15%. The steady-state (kinetic) version of this model was used to develop a formula describing the relationship between the FCR for LDLc and blood plasma LDLc concentration which agrees well with published data.

Adult↗