Reductions In Regional Perfusion Research Articles

Cerebral blood flow responses to hyperoxia: exploring sex differences

Background: The administration of oxygen-rich gas (hyperoxia), is a common treatment in clinical medicine and various military occupations. Hyperoxia reduces cerebral blood flow (CBF), however, there exists substantial variability in the magnitude of its effect (0-33%), as well as an uncertainty regarding the role that hypocapnia may play in this vasoconstriction. Interestingly, hyperoxic vasoconstriction appears to be mediated by excessive reactive oxygen species (ROS) signaling. To our knowledge, no studies have directly assessed whether CBF regulation during hyperoxia is sex-specific. This is important since young females are broadly predicted to exhibit lower ROS stress and/or greater antioxidant capacity than males. Therefore, men and women may be differentially impacted. This led us to hypothesize hyperoxia will decrease CBF less in females than males. Methods: Healthy, young adults (n= 17; 7 F; 20 ± 6 yr; BMI: 20.7 ± 5) were studied after an 8 hour fast and 24 hours without caffeine or alcohol. Women were studied on days 1-5 of menstrual cycle. Subjects completed a single magnetic resonance imaging (MRI) visit. 2D phase contrast (2D PC) MRI was conducted to quantify flow through both internal carotid and vertebral arteries during normoxia, and then repeated during steady-state hyperoxia with subjects breathing 100% O 2 . Carbon dioxide (CO 2 ) was supplemented to maintain end-tidal CO 2 (ETCO 2 ) during hyperoxia. CBF was analyzed as absolute flow (mL/min), total change (ΔmL/min), and percent change (% ΔmL/min). In a subset (n=10; 3 F), arterial spin labeling (ASL) MRI was added to explore regional effects on perfusion (mL/100g/min) for an additional 5 mins of hyperoxia. The CAT12 toolbox extension for SPM12 was used to process ASL data. Significance was determined using a two-factor repeated measures ANOVA and was set at p≤0.05. Results: Results are mean±SD. Heart rate, mean arterial pressure, and ETCO 2 were similar between sexes and did not change between normoxia and hyperoxia (p>0.05). When analyzing neck arteries using 2D PC MRI, hyperoxia did not have a significant effect on CBF (p>0.1), and there was no differential effect between sexes (p>0.1). In contrast, ASL data indicated hyperoxia significantly reduced perfusion in both sexes in all regions analyzed (gray matter, white matter, middle frontal gyrus, frontal operculum, anterior orbital gyrus, superior frontal gyrus, medial frontal cortex, accumbens area, and medial orbital gyrus (p≤0.013)). There was a trend towards a significantly smaller reduction in females in all regions (p≤0.101) except the anterior orbital gyrus (p=0.329). Conclusion: Contrary to our hypothesis, the CBF response to hyperoxia did not differ between men and women when examining the macrovasculature that supply blood to the brain. However, the smaller hyperoxic reductions in regional perfusion in females indicate that hyperoxia constriction may be sex-specific at the microvasculature level. NIH R01 HL150361 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Time and dose-related changes in lung perfusion after definitive radiotherapy for NSCLC

Background and purposeTo examine radiation-induced changes in regional lung perfusion per dose level in 58 non-small-cell lung cancer (NSCLC) patients treated with intensity-modulated radiotherapy (IMRT). Material and methodsNSCLC patients receiving chemo-radiotherapy (RT) of minimum 60 Gy were included prospectively in the study. Lung perfusion single-photon emission computed tomography (SPECT/CT) was performed before and serially after RT. Changes (relative to baseline, %) in regional lung perfusion were correlated with regional dose. Toxicity outcome was radiation pneumonitis (RP) CTC grades 2–5. ResultsPerfusion changes were associated with dose. Dose-dependent reduction in regional perfusion was observed at 3, 6 and 12 months of follow-up. Relative perfusion loss per dose bin was 4% at 1 month, 14% at 3 months, 13% at 6 months and 21% at 12 months after RT. In patients with RP, perfusion reduction was larger in high dose lung regions, compared to those without RP. Low dose regions, on the contrary, revealed perfusion gain in the patients with RP. ConclusionProgressive dose dependent perfusion loss is manifested on SPECT up to 12 months following IMRT. These findings suggest that the dynamic change in perfusion may have prognostic value in predicting radiation pneumonitis in NSCLC patients treated with IMRT.

Loss of lung function after chemo-radiotherapy for NSCLC measured by perfusion SPECT/CT: Correlation with radiation dose and clinical morbidity

ABSTRACTBackground. The purpose of the study was to assess dose and time dependence of radiotherapy (RT)-induced changes in regional lung function measured with single photon emission computed tomography (SPECT) of the lung and relate these changes to the symptomatic endpoint of radiation pneumonitis (RP) in patients treated for non-small cell lung cancer (NSCLC).Material and methods. NSCLC patients scheduled to receive curative RT of minimum 60 Gy were included prospectively in the study. Lung perfusion SPECT/CT was performed before and three months after RT. Reconstructed SPECT/CT data were registered to treatment planning CT. Dose to the lung was segmented into regions corresponding to 0–5, 6–20, 21–40, 41–60 and > 60 Gy. Changes (%) in regional lung perfusion before and after RT were correlated with regional dose and symptomatic RP (CTC grade 2–5) outcome.Results. A total of 58 patients were included, of which 45 had three-month follow-up SPECT/CT scans. Analysis showed a statistically significant dose-dependent reduction in regional perfusion at three-month follow-up. The largest population composite perfusion loss was in 41–60 Gy (42.2%) and > 60 Gy (41.7%) dose bins. Lung regions receiving low dose of 0–5 Gy and 6–20 Gy had corresponding perfusion increase (-7.2% and -6.1%, respectively). Regional perfusion reduction was different in patients with and without RP with the largest difference in 21–40 Gy bin (p = 0.02), while for other bins the difference did not reach statistical significance. The risk of symptomatic RP was higher for the patients with perfusion reduction after RT (p = 0.02), with the relative risk estimate of 3.6 (95% CI 1.1–12).Conclusion. Perfusion lung function changes in a dose-dependent manner after RT. The severity of radiation-induced lung symptoms is significantly correlated with SPECT perfusion changes. Perfusion reduction early after RT is associated with a high risk of later development of symptomatic RP.

TU‐G‐BRA‐01: Assessing Radiation‐Induced Reductions in Regional Lung Perfusion Following Stereotactic Radiotherapy for Lung Cancer

Purpose:The dose‐dependent nature of radiation therapy (RT)‐induced lung injury following hypo‐fractionated stereotactic RT is unclear. We herein report preliminary results of a prospective study assessing the magnitude of RT‐induced reductions in regional lung perfusion following hypo‐fractionated stereotactic RT.Methods:Four patients undergoing hypo‐fractionated stereotactic lung RT (SBRT: 12 Gy × 4 fractions or 10 Gy × 5 fractions) had a pre‐treatment SPECT (single‐photon emission computed tomography) perfusion scan providing a 3D map of regional lung perfusion. Scans were repeated 3–6 months post‐treatment. Pre‐ and post SPECT scans were registered to the planning CT scan (and hence the 3D dose data). Changes in regional perfusion (counts per cc on the pre‐post scans) were computed in regions of the lung exposed to different doses of radiation (in 5 Gy intervals), thus defining a dose‐response function. SPECT scans were internally normalized to the regions receiving <5 Gy.Results:At 3 months post‐RT, the changes in perfusion are highly variable. At 6 months, there is a consistent dose‐dependent reduction in regional perfusion. The average percent decline in regional perfusion was 10% at 15–20 Gy, 20% at 20–25 Gy, and 30% at 25–30 Gy representing a relatively linear dose response with an approximate 2% reduction per Gray for doses in excess of 10 Gy. There was a subtle increase in perfusion in the lung receiving <10 Gy.Conclusion:Hypo‐fractionated stereotactic RT appears to cause a dose‐dependent reduction in regional lung perfusion. There appears to be a threshold effect with no apparent perfusion loss at doses <10 Gy, though this might be in part due to the normalization technique used. Additional data is needed from a larger number of patients to better assess this issue. This sort of data can be used to assist optimizing RT treatment plans that minimize the risk of lung injury.Partly supported by the NIH (CA69579) and the Lance Armstrong Foundation

Breast Cancer Radiotherapy and Coronary Artery Stenosis: Location, Location, Location

Breast Cancer Radiotherapy and Coronary Artery Stenosis: Location, Location, Location

SYSTEMIC AND REGIONAL HEMODYNAMIC EFFECTS OF HIGH-DOSE EPINEPHRINE INFUSION IN HYPOXIC PIGLETS RESUSCITATED WITH 100% OXYGEN

Shock and poor regional perfusion are common in asphyxiated neonates. We compared the systemic and regional hemodynamic effects of high-dose epinephrine (E) with those of dopamine combined with low-dose epinephrine (DE) infusions in a neonatal model of hypoxia-reoxygenation. Neonatal piglets (1-3 days, 1.5-2.5 kg) were acutely instrumented to continuously monitor systemic arterial pressure (SAP), pulmonary artery pressure, cardiac index (CI), and blood flows at the left common carotid, superior mesenteric, and renal arteries. Either epinephrine (1 microg.kg(-1).min(-1)) or dopamine (10 microg.kg(-1).min(-1)) and epinephrine (0.2 microg.kg(-1).min(-1)) were given for 2 h in hypoxic piglets resuscitated with 100% oxygen (n = 8 per group) in a randomized blinded fashion. Control piglets received hypoxia and reoxygenation but no catecholamine infusion (n = 7). Alveolar hypoxia (PaO2, 33-37 mmHg) caused reduced CI (89-92 vs. 171-186 mL.kg(-1).min(-1) of baseline, P < 0.05), hypotension (SAP, 28-32 mmHg) with pH 7.05 to 7.10, and decreased regional flows. Upon reoxygenation, CI and SAP improved but gradually deteriorated to 131 to 136 mL.kg(-1).min(-1) and 41 to 49 mmHg at 2 h of reoxygenation, respectively. E and DE administration similarly improved CI (167 +/- 60 and 166 +/- 55 vs. 121 +/- 35 mL.kg(-1).min(-1) of controls) and SAP (53 +/- 7 and 56 +/- 10 vs. 39 +/- 8 mmHg of controls), respectively, and the pulmonary vascular resistance (vs. controls, all P < 0.05). Heart rate and pulmonary artery pressure were not different between groups. Systemic oxygen delivery and consumption were increased in E- and DE-treated groups with no difference in extraction ratio between groups. There were no differences in regional blood flows and oxygen delivery between groups. After hyperlactatemia with hypoxia, plasma lactate levels decreased with no difference between groups. Epinephrine given as the sole agent is as effective as dopamine and low-dose epinephrine combined in treating shock and hypotension that follow the resuscitation of hypoxic neonatal piglets, with no reduction in regional perfusion.

1047: The Time Course of Radiation Therapy-Induced Reductions in Regional Perfusion: A Prospective Study With >10 Years of Follow-up

1047: The Time Course of Radiation Therapy-Induced Reductions in Regional Perfusion: A Prospective Study With >10 Years of Follow-up

Brain Blood Flow SPET Imaging in Heroin Abusers

To assess whether chronic heroin abuse may generate vascular central nervous deficits, we studied the profile of vascular alterations in 17 heroin addicts (14 males mean age 31 years, range 23-39 years and 3 females mean age 33 years, range 30-35 years) before and, in one of them, 10 weeks after an ultra-rapid heroin detoxification. Using the functional technique of single-photon emission tomography (SPET) with 740 MBq of (99m)Tc-hexametazine (HMPAO) and computational brain-mapping techniques by means of a Talairach analysis, we determined the pattern of vascular brain alterations associated with chronic heroin abuse. Compared with controls, subjects who had used heroin chronically showed a decrease of global brain perfusion that was more significant in the frontal cortex-mainly in orbito-frontal regions, as well as in the occipital and temporal lobes. All patients showed marked asymmetric perfusion of the basal ganglia and the majority of them showed also an asymmetric perfusion of cerebellum. In addition, there were small activated areas dispersed in the occipital lobe (3 of 17) and apex region (4 of 17). In conclusion, decreased perfusion in heroin addicts was found in regions involved in the control of attention, motor speed, memory and visual-spatial processing. The prefrontal cortex is involved in decision making and inhibitory control, processes disturbed in heroin addicts who have stopped heroin consumption. A reduction in regional perfusion may reflect ongoing subtle neurocognitive deficits, which are consistent with the maintenance of asymmetry of the basal nuclei.

SU‐FF‐T‐465: Relating Changes in Pulmonary Functin Tests (PFTs) to Changes in Radiation‐Induced Regional Lung Perfusion

Purpose: To further assess if RT‐induced changes in pulmonary function tests (PFTs) can be prospectively predicted based on the sum of predicted RT‐induced changes in regional lung perfusion. Method and Materials: Between 1991 and 2005, 123 evaluable patients with lung cancer underwent pre‐ and post‐RT PFTs (forced volume capacity [FVC], forced expiratory volume in one second [FEV1] and diffusion capacity for carbon monoxide [DLCO]) as part of a prospective trial. Patients with recurrence or death within 6‐month post‐RT were excluded. The maximal declines in PFTs were noted. The anticipated decline in PFTs was computed by summing the predicted reductions in regional perfusion, throughout the lung, based on a previously‐defined population dose‐response model [DRC] and the patient's pre‐RT SPECT (single photon emission computed tomography) lung perfusion scan. This “integrated response” is also termed the overall response parameter (ORP): urn:x-wiley:0094-2405:media:mp1379:mp1379-math-0001 where Vd is the percentage volume of lung irradiated to dose d, and Rd is the predicted reduction in regional perfusion at dose d based on a population DRC. Correlations between predicted and measured changes in PFTs were evaluated using 2‐tailed Pearson test. Results: There was a statistically‐significant association between the reduction in PFTs (i.e. FVC and DLCO) and ORP, p&lt;0.01; however, correlation coefficients were low (range: 0.24–0.35). Correlations were better in the subgroup of patients without large central tumors (i.e. those often with associated hypoperfusion of adjacent lung on the pre‐RT SPECT) and with more than 2 follow‐up PFTs post‐RT (range: 0.41–0.62). Conclusion: The sum of predicted RT‐induced changes in regional perfusion is related to RT‐induced changes in PFTs, however, correlations are relatively weak. These findings are consistent with our prior analysis involving fewer patients and continue to illustrate that predicting changes in PFTs is extremely challenging.Supported partly, by NIH grant R01‐CA69579. Thanks to UNC for PLUNC planning software.

Cerebral Perfusion Response to Hyperoxia

Graded levels of supplemental inspired oxygen were investigated for their viability as a noninvasive method of obtaining intravascular magnetic resonance image contrast. Administered hyperoxia has been shown to be effective as a blood oxygenation level-dependent contrast agent for magnetic resonance imaging (MRI); however, it is known that high levels of inspired fraction of oxygen result in regionally decreased perfusion in the brain potentially confounding the possibility of using hyperoxia as a means of measuring blood flow and volume. Although the effects of hypoxia on blood flow have been extensively studied, the hyperoxic regime between normoxia and 100% inspired oxygen has been only intermittently studied. Subjects were studied at four levels of hyperoxia induced during a single session while perfusion was measured using arterial spin labelling MRI. Reductions in regional perfusion of grey matter were found to occur even at moderate levels of hyperoxia; however, perfusion changes at all oxygen levels were relatively mild (less than 10%) supporting the viability of hyperoxia-induced contrast.

Estimation of the α/β Ratio for Lung Injury Based on Direct Measurements of Radiotherapy (RT)-Induced Reduction in Regional Perfusion in Human Patients

Estimation of the α/β Ratio for Lung Injury Based on Direct Measurements of Radiotherapy (RT)-Induced Reduction in Regional Perfusion in Human Patients

Cerebral perfusion SPET correlated with Braak pathological stage in Alzheimer's disease.

Reductions in regional cerebral perfusion, particularly in the posterior temporo-parietal lobes, are well recognized in Alzheimer's disease. We set out to correlate perfusion changes, using (99m)Tc-HMPAO single photon emission tomography (SPET), with the pathological stage of Alzheimer's disease. The 'Braak stage' of the distribution of neurofibrillary pathology in post-mortem brains was used to classify SPET scans taken in life from a mixed (dementia and control) elderly population into the entorhinal stage (n = 23 subjects), limbic stage (n = 30 subjects) and neocortical stage (n = 36 subjects) Alzheimer's disease pathology. The SPET scans were then registered to a common, standard Talaraich space, and single template scans produced for each pathological stage. Comparison of these templates revealed an evolution in the pattern of reduction in regional perfusion. Additional comparisons were performed using earlier SPET scans obtained 5 years before death. For comparisons between templates, a threshold of 10% perfusion change was chosen so as to be clinically relevant as well as statistically significant. Reduced perfusion appears between the entorhinal and limbic stages in the anterior medial temporal lobe, subcallosal area, posterior cingulate cortex, precuneus and possibly the supero-anterior aspects of the cerebellar hemispheres. Large posterior temporo-parietal perfusion defects then appear between the limbic and neocortical stages, before finally large frontal lobe perfusion defects. The time course of these perfusion defects appears relatively long, suggesting that perfusion changes may have scope to be a diagnostic aid in staging Alzheimer's disease in life. The reduction in anterior medial temporal lobe perfusion may have future relevance on modern high resolution SPET and PET systems and also perfusion-type MRI sequences.

THE time course of radiation therapy-induced reductions in regional perfusion: a prospective study with >5 years of follow-up

Purpose : To assess the time-dependence of radiation therapy (RT)-induced reductions in regional lung perfusion, as measured by single photon emission computed tomography (SPECT) lung perfusion scans. Methods and Materials : Between 1991 and 1999, 79 patients had SPECT lung perfusion scans before and serially after RT. Changes in regional perfusion were correlated with regional dose using 3D planning tools and image fusion (PLUNC-Plan UNC). Multiple post-RT follow-up scans were evaluated to determine the temporal nature of RT-induced regional perfusion changes. To facilitate the comparison of dose-response curves (DRCs) at different post-RT intervals, each DRC was fit to a linear model and thus described by its slope. Results : There was a dose-dependent reduction in regional perfusion at nearly all time points post-RT ( p = 0.0001). The slope of the DRCs for RT-induced reductions in regional perfusion became steeper at essentially each successive follow-up interval ( p = 0.0001). However, the increases in slope became progressively smaller at later follow-up intervals. Overall, about 80% of the long-term RT-induced regional perfusion injury was manifest within 12 months post-RT. Conclusion : There is a progression of RT-induced reductions in regional perfusion, with most of this injury manifest within 12 months post-RT. Additional regional injury appears to evolve for years.

Can we predict radiation-induced changes in pulmonary function based on the sum of predicted regional dysfunction?

To determine whether changes in whole-lung pulmonary function test (PFT) values are related to the sum of predicted radiation therapy (RT)-induced changes in regional lung perfusion. Between 1991 and 1998, 96 patients (61% with lung cancer) who were receiving incidental partial lung irradiation were studied prospectively. The patients were assessed with pre- and post-RT PFTs (forced expiratory volume in one second [FEV1] and diffusion capacity for carbon monoxide [DLCO]) for at least a 6-month follow-up period, and patients were excluded if it was determined that intrathoracic recurrence had an impact on lung function. The maximal declines in PFT values were noted. A dose-response model based on RT-induced reduction in regional perfusion (function) was used to predict regional dysfunction. The predicted decline in pulmonary function was calculated as the weighted sum of the predicted regional injuries: equation [see text] where Vd is the volume of lung irradiated to dose d, and Rd is the reduction in regional perfusion anticipated at dose d. The relationship between the predicted and measured reduction in PFT values was significant for uncorrected DLCO (P = .005) and borderline significant for DLCO (P = .06) and FEV1 (P = .08). However, the correlation coefficients were small (range,.18 to.30). In patients with lung cancer, the correlation coefficients improved as the number of follow-up evaluations increased (range,.43 to.60), especially when patients with hypoperfusion in the lung adjacent to a central mediastinal/hilar thoracic mass were excluded (range,.59 to.91). The sum of predicted RT-induced changes in regional perfusion is related to RT-induced changes in pulmonary function. In many patients, however, the percentage of variation explained is small, which renders accurate predictions difficult.

Radiation-induced pulmonary injury: symptomatic versus subclinical endpoints

Purpose : To assess the relationship between radiation (RT)induced pulmonary symptoms and subclinical changes in pulmonary functions tests (PFT) and radiographs. Materials and methods : A total of 184 patients irradiated between 1992 and 1998 were prospectively evaluated for RT-induced pulmonary symptoms, changes in computed tomography (CT) density, reductions in single photon emission CT (SPECT) perfusion, and changes in pulmonary functions tests (forced expiratory volume in 1s [FEV 1 ] and diffusion capacity to carbon monoxide [DLCO]). Comparisons between the evaluable patients with (N = 34) and without (N = 106) RT-induced pulmonary symptoms were made. Results : Within 6 months of RT, 80% of the RT-induced symptoms were noted. There was no association between the presence or absence of RT-induced pulmonary symptoms and the frequency of RT-induced radiographic changes (p = 0.53), or in the dose–response curve for RT-induced reductions in regional perfusion. Overall, RT-induced changes in SPECT images were more commonly seen than increased density changes on CT (p < 0.001). Most patients with pulmonary symptoms had relatively low pre-RT PFTs and experienced further declines following RT. Conclusions : Regional radiographic changes in CT-defined tissue density or SPECT-defined tissue perfusion are similar in patients with and without RT-induced pulmonary symptoms because these endpoints do not consider the volume of lung affected. RT-induced pulmonary symptoms are better related to post-RT PFT because they are an assessment of whole lung function. Additional studies are necessary to better define models that can predict the degree of radiation-induced changes in whole lung function.

The time course of radiation therapy-induced reductions in regional perfusion: A prospective study > 5 years of follow up

The time course of radiation therapy-induced reductions in regional perfusion: A prospective study > 5 years of follow up

Impaired matching of perfusion and ventilation in heart failure detected by 133xenon.

In severe chronic heart failure (CHF) the ventilatory cost of CO2 elimination during exercise (VE/VCO2) is increased, suggesting ventilation/perfusion (V/Q) mismatch. The relationship of exercise VE/VCO2 regression slope m to deadspace ventilation was studied in 15 patients with CHF who underwent cardiopulmonary exercise testing and arterial blood gas monitoring. Regional lung ventilation and perfusion was studied, using 133xenon, at rest and peak exercise in a further group of 10 CHF patients and in five normal subjects. VE/VCO2 slope m correlated well with deadspace ventilation at peak exercise in the 15 patients with CHF. We therefore used exercise VE/VCO2 slope m to categorize CHF patients undergoing 133xenon imaging into groups with increased (slope m > 36) or normal (slope m < 36) exercise deadspace ventilation. In normals, resting V/Q determined by 133xenon showed a gravitational gradient, which improved on exercise as a result of relative increases and of relative reductions in regional perfusion; no significant changes in regional ventilation distribution were detected. In patients with CHF who had normal slope m (n = 5), rest and exercise V/Q were similar to the normal subjects. In CHF patients with increased slope m (n = 5) however, the resting gravitational gradient of V/Q was lost, and there were no significant changes in relative perfusion distribution on exercise. These findings suggest that the increased ventilatory cost of CO2 elimination found in certain patients with CHF is related to inability to coordinate and optimise the relative distribution of lung perfusion with respect to ventilation during exercise.

Regional perfusion, glucose metabolism, and wall motion in patients with chronic electrocardiographic Q wave infarctions: evidence for persistence of viable tissue in some infarct regions by positron emission tomography.

Positron-emission tomography with 13N-ammonia and 18F-2-deoxyglucose was used to assess regional perfusion and glucose utilization in 31 chronic electrocardiographic Q wave regions in 20 patients. With previously published criteria, regions of infarction were identified by a concordant reduction in regional perfusion and glucose utilization, and regions of ischemia were identified by preservation of glucose utilization in regions of diminished perfusion. Only 10 of the 31 regions (32%) exhibited myocardial infarction tomographically. In contrast, positron tomography revealed ischemia in six regions (20%) and was normal in 15 regions (48%). Even when Q wave regions were reassigned and consolidated to enhance the specificity of the electrocardiogram, uptake of 18F-2-deoxyglucose was noted in the majority (54%) of the regions. Neither electrocardiographic ST-T changes nor severity of associated wall motion abnormality reliably distinguished tomographically identified regions of ischemia from infarction. Thus positron tomography reveals evidence of persistent tissue metabolism in a high proportion of chronic electrocardiographic Q wave regions, and commonly used clinical tests do not reliably distinguish hypoperfused but viable regions from tomographically defined regions of myocardial infarction.

Rate of enzyme release from infarcted myocardium depends on reductionof regional perfusion

Rate of enzyme release from infarcted myocardium depends on reductionof regional perfusion

Sequence of events in angina at rest: primary reduction in coronary flow.

To investigate the events that lead to acute myocardial ischemia we monitored continuously the ECG, the left ventricular (four patients) or aortic (two patients) pressure and the great cardiac vein oxygen saturation (CSO2S) by a fiberoptic catheter in six patients with frequent anginal attacks at rest. We recorded 137 transient ischemic episodes (10 with chest pain) characterized by ST-segment elevation in 28 episodes, depression in three episodes and by pseudonormalization of previously inverted or flat T waves in 106 episodes. The onset of electrocardiographic and hemodynamic changes was preceded by a large drop in CSO2S in all 135 episodes with ST-T changes in the anterior leads but not in two episodes with ST elevation on inferior leads. The fall in CSO2S, consistently followed by signs of left ventricular function impairment and never preceded by any detectable increase in the hemodynamic determinants of myocardial oxygen consumption, probably reflects a reduction in regional perfusion. Thus, a reduction in coronary flow may cause transient ischemia in patients with angina at rest. These episodes may be associated with variable, often minor electrocardiographic changes and occasionally with anginal pain.