Physiology and theory of tracer washout techniques for the estimation of myocardial blood flow: Flow estimation from tracer washout

Hales

et al. 1985

Circulation Research

238

171

SUMMARYRegional myocardial blood flow has been thought to be relatively uniform, in accord with the singular function of myocardial cells. However, considerable spatial heterogeneity has been observed in the hearts of anesthetized animals and in isolated hearts. Studies were undertaken in a total of 13 baboons. Eleven were awake, healthy animals sitting in chairs at rest or feeding, some performed mild leg exercise (wheel turning), and others were subjected to whole body heating; two were anesthetized, methodological controls. Microspheres (15 ± 3 μm diameter, 0.5 × 10 6 /kg body weight) were injected via a catheter into the apex of the left ventricle while arterial blood was sampled at a constant rate for calculating cardiac output. Microspheres with different labels were injected at six intervals of 20 minutes to several hours. On sacrifice, the hearts were sectioned into 204 locatable pieces (left ventricle, 168; right ventricle, 27; and atria, 9). Average resting myocardial flow was 2.1 ± 0.2 ml/g per min (mean ± SD, n = 11). Left and right ventricles and atria comprised 70 ± 2% (n = 13), 20 ± 2%, and 10 ± 2% respectively of the total heart mass while receiving 80 ± 3%, 16 ± 2%, and 4 ± 2% of the total myocardial flow. Thus, mean left ventricular flow was 114 ± 5% of the average for the whole heart, right ventricular flow was 81 ± 13%, and atrial flow was 41 ± 13%. Myocardial flow heterogeneity was marked; in left ventricle, regional flows ranged from one-third to two times the mean, the relative dispersion (= standard deviation/mean) of regional flows, corrected for methodological scatter and temporal variation, was 0.33 ± 0.06 (n = 67) in the whole heart, 0.26 ± 0.07 in left ventricle, 0.32 ± 0.11 in right ventricle, and 0.22 ± 0.19 in the atria. The pattern of regional flows in each heart tended to remain stable with time. In each piece averaged over time, the relative dispersion due to temporal heterogeneity was 0.11 ± 0.03 (n = 2040) in the whole heart, 0.09 ± 0.03 in the left ventricle, 0.15 ± 0.05 in the right ventricle, and 0.23 ± 0.06 in the atria. The conclusion is that the degree of spatial heterogeneity of local myocardial flows in conscious primates is similar to that of anesthetized animals and isolated hearts, and is much greater than that due to temporal fluctuations. KeywordsFlow distribution; Coronary arteries; Septal perfusion; Tracer-labeled microspheres; Awake primates; Spatial variation in flow; Temporal variation in flowWith the increasing refinement of biochemical and physiological observations, the variations that occur throughout the myocardium in rates of metabolism (Griggs et al., 1972) We appreciate the help of G. Crookcr in the preparation of the manuscript, and of H. Nurk with the illustrations. Presented in part at FASEB, Fed. P.roc. 37: 875, 1978. NIH Public Access (Gamble et al., 1974;Schubert et al., 1978;Weiss and Sinha, 1978), and in flow (Domenech et al., 1969;Yipintsoi et al., 1973) have become quite evident. It is no longer sufficient either in concept or in practi...

Section: Discussionmentioning

confidence: 99%

Stability of heterogeneity of myocardial blood flow in normal awake baboons.

King

Hales

et al. 1985

Circulation Research

238

171

“…Because the PS's used for these solutions are so high, the tracer is virtually flow-limited in its exchange. This means that they will be almost superimposed on each other by time scaling each relative to its own mean transit time [25,26], which is a simple but revealing test for flowlimited blood-tissue exchange.…”

Section: Applicationsmentioning

confidence: 99%

A computational model of oxygen transport from red blood cells to mitochondria

Beyer¹,

Computer Methods and Programs in Biomedicine

Deußen

2002

Self Cite

A computational model of oxygen transport from red blood cells to mitochondria with subsequent reaction to water is presented. This computational model consists of a five region convectiondiffusion-reaction mathematical model which is solved using a standard numerical time-split method. The unique feature of this mathematical model is the treatment of the red blood cells and the plasma as two separate flows. The numerical method is second order accurate overall. This computational model is useful for analyzing residue data from positron emission tomography or data from multiple indicator dilution curves.

“…The water content of a normal heart is relatively precisely known being 0.78 ± 0.01 ml/g (110), although it can go up as high as 83 -84% in edematous tissue. The exchanges of 15 O-water and 3 HHO are completely flow-limited in the heart, there being no effective barrier between the blood and the myocyte water space (10,19,109). The great advantage of methods where information is obtained by external detection (PET, MRI, and ultrasound) is that they are noninvasive and can be repeated.…”

Section: Imaging For Regional Blood Flowsmentioning

confidence: 99%

The mechanical and metabolic basis of myocardial blood flow heterogeneity

Basic Research in Cardiology

Beard

2001

Self Cite

Precise measurements of regional myocardial blood flow heterogeneity had to be developed before one could seek causation for the heterogeneity. Deposition techniques (particles or molecular microspheres) are the most precise, but imaging techniques have begun to provide high enough resolution to allow in vivo studies. Assigning causation has been difficult. There is no apparent association with the regional concentrations of energy-related enzymes or substrates, but these are measures of status, not of metabolism. There is statistical correlation between flow and regional substrate uptake and utilization. Attribution of regional flow variation to vascular anatomy or to vasomotor control appears not to be causative on a long-term basis. The closest relationships appear to be with mechanical function, but one cannot say for sure whether this is related to ATP hydrolysis at the crossbridge or associated metabolic reactions such as calcium uptake by the sarcoplasmic reticulum.