Temporal fluctuations in regional myocardial flows

King, Richard B.; Bassingthwaighte, James B.

doi:10.1007/bf00584480

Cited by 57 publications

(40 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to the finding in dog lungs (6), temporal heterogeneity of blood flow has been found in other organs including the brain, myocardium and skeletal muscle (23)(24)(25). The lower CV temporal results contradict our hypothesis that due to greater pulmonary vasoreactivity (2,3,6,8) temporal heterogeneity would be greater in piglets than in adult animals.…”

Section: Diverse Pulmonary Blood Flow In Pigletscontrasting

confidence: 56%

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

et al. 2007

View full text Add to dashboard Cite

ABSTRACT:Regional pulmonary blood flow (PBF) in adult animals varies over space and time, following a fractal pattern. We hypothesized that PBF would follow a fractal pattern in young animals. Five, two-week old piglets were sedated and mechanically ventilated. After stabilization, fluorescent microspheres were injected via the right atrium at baseline and then again at 5, 20, 20.5, 40 and 60 min. The lungs were subsequently excised, dried, inflated, and cored into 0.12-cm 3 pieces (mean n ϭ 561 Ϯ 106 per animal) with the spatial coordinates recorded for each piece. Regional PBF was spatially and temporally heterogeneous with a spatial coefficient of variation of 43.3 Ϯ 7.9% and a temporal coefficient of variation of 14.3 Ϯ 0.4%. PBF followed a fractal pattern with a fractal dimension of 1.20 Ϯ 0.06 at 20 min, remaining stable throughout the experiment. PBF decreased with distance from the hilum but did not follow a lobar pattern. Temporal heterogeneity did not significantly increase with time but low flow regions demonstrated the greatest temporal variability throughout the study. Hence, PBF in young piglets was characterized both spatial and temporal heterogeneity. A considerable amount of information describing the structural and functional characteristics of the pulmonary circulation during postnatal lung development exists. Features such as vascular reactivity, pulmonary capillary recruitment, and metabolic capabilities of the microvasculature appear to differ between adult and immature animals (1-8). Recently, the fractal spatial distribution and isogravitational heterogeneity of pulmonary blood flow (PBF) have been delineated in adult animals using injectable microspheres that achieved greater resolution than earlier studies (9,10). The results of these studies diverge from the findings of homogeneous gravitational zones described by West et al. (11). Temporal heterogeneity also occurs in the pulmonary circulation, which may subserve the conservation of energetics rather than ventilation-perfusion relationships (12).Hitherto, these physiologic characteristics remain unstudied in newborn or very young animals. Speculation suggests that the fractal nature of PBF is based on the pulmonary anatomy, particularly of the precapillary bed (13). If true, the spatial distribution of PBF in young animals should be similar to that in adults. Furthermore, the presence of temporal heterogeneity of PBF in young animals has not been reported. Previous studies suggest a higher degree of pulmonary vascular reactivity in neonatal animals (2,3,6) compared with adults, and hence temporal heterogeneity should be greater than that previously described in adult animals.We measured spatial and temporal heterogeneity in piglets because morphometric studies of pulmonary development in the piglet suggest that the vascular and alveolar changes during the first 3 months of life are similar to those seen in humans (14,15). We hypothesized that under normoxic conditions the pulmonary blood flow would demonstrate greater spatial heteroge...

show abstract

Section: Diverse Pulmonary Blood Flow In Pigletscontrasting

confidence: 56%

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

et al. 2007

View full text Add to dashboard Cite

show abstract

“…King et al (52) established the general perspective that at this spatial resolution the standard deviation of the flows is 20 -30% of the mean. Later analysis of these same studies (53) showed that the regional flows were stable over long periods of time, from a few hours up to a day, in four to six repeated observations. This observation challenged the notion that large temporal fluctuations in regional flows occurred normally, thus provoking a search for an explanation for the stable spatial variation.…”

Section: Microsphere Methodsmentioning

confidence: 94%

“…Arguing against this was the fact that most users of the microsphere technique made prolonged injections, of the order of thirty seconds to one minute, so that any "snapshot" effect would be averaged over at least the duration of the injection: this is another way of saying that any regional fluctuations in flow would have to be very slow with respect to the injection duration for vasomotion to be the explanation. However, the clinching argument was really provided by King and Bassingthwaighte (53) who showed that the same regions remained stable in their relative flows during rest and moderate exercise over periods of hours and up to one day. Deussen et al (35) confirmed these observations and extended them by showing that adrenergic stimulation caused proportional increases in flow regionally, so that the same patterns of flow were observed in the stimulated state as in the resting state.…”

Section: Vasomotor Influencesmentioning

confidence: 99%

The mechanical and metabolic basis of myocardial blood flow heterogeneity

Bassingthwaighte

Beard

2001

Basic Research in Cardiology

View full text Add to dashboard 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.

show abstract

“…Second, even in the absence of hypoxia, airways and vasculature and alveolar surfactant are pH sensitive and respond very rapidly to changes in ambient [H+] and [CO2] (15)(16)(17)(18)(19). Third, recent data suggest that the lung, heart, and skeletal muscle display temporal fluctuations in regional perfusion (20)(21)(22)(23)(24). With short-term temporal fluctuations in regional perfusion and ventilation, the amount of CO2 delivered to or eliminated from a region and in parallel the amount of 02 taken up from or delivered to a region will vary and set new prevailing local CO2 and 02 tensions.…”

Section: Introductionmentioning

confidence: 99%

Effects of carbonic anhydrase inhibition on ventilation-perfusion matching in the dog lung.

Swenson¹,

Robertson²,

Hlastala³

1993

J. Clin. Invest.

View full text Add to dashboard Cite

Lung carbonic anhydrase (CA) permits rapid pH responses when changes in regional ventilation or perfusion alter airway and alveolar Pco2. These pH changes affect airway and vascular resistances and lung compliance to optimize the balance of regional ventilation (VA) and perfusion (Q) in the lung. To test the hypothesis that these or other CA-dependent mechanisms contribute to VA/Q matching, we administered acetazolamide (25 mg/kg intravenously) to six anesthetized and paralyzed dogs and measured VA/Q relationships before and after CA inhibition by the multiple inert gas elimination technique. Four other groups of dogs were studied to control for possible confounding effects of time under anesthesia and nonselective CA inhibition by acetazolamide: (a) saline placebo as a control for duration of anesthesia, (b) 4% CO2 inhalation to mimic systemic CO2 retention, (c) 1 mg/kg benzolamide (a selective renal CA inhibitor) or 0.5 meq /kg HCO to mimic systemic metabolic acidosis, and (d) 500 mg/kg 4,4'-dinitrostilbene-2,2'-disulfonate (an inhibitor of red cell band 3 protein) to mimic the respiratory acidosis arising from an intracapillary block to rapid mobilization ofplasma HCO3 in CO2 exchange. Acetazolamide increased VA/Q mismatch and reduced arterial Po2 measured at equilibrium but these did not occur in the control group. There was no deterioration in VA/Q matching when systemic respiratory acidosis produced either by CO2 inhalation or 4,4'-dinitrostilbene-2,2'-disulfonate or metabolic acidosis (benzolamide or HCl) were imposed to mimic the effects of acetazolamide apart from its inhibition of lung CA. These results support the concept that lung CA subserves VA /Q matching in the normal lung. (J. Clin. Invest. 1993.92:702-709.)

show abstract

Temporal fluctuations in regional myocardial flows

Cited by 57 publications

References 25 publications

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

Spatial and Temporal Heterogeneity of Regional Pulmonary Blood Flow in Piglets

The mechanical and metabolic basis of myocardial blood flow heterogeneity

Effects of carbonic anhydrase inhibition on ventilation-perfusion matching in the dog lung.

Contact Info

Product

Resources

About