Gender differences in cognitive and neural correlates of remembrance of emotional words

Studies suggest that men and women have important differences in specific cognitive functions. Men show superior spatial memory and women demonstrate superior verbal memory, and women rely on emotional content to a greater degree in the processing of information. In spite of extensive research in neural correlates of human cognition, little is known about possible gender differences or the role of emotional content in the mediation of cognition. Two sets of lists of word pairs were developed, one with neutral (e.g., school-grocery) and the other with emotional (e.g., mutilate-beat) content. Male and female subjects were asked to rate emotions related to the words on several dimensions (e.g., nervous, fearful, happy). In a second experiment, men and women underwent positron emission tomographic (PET) measurement of brain blood flow during retrieval of word pairs. Words in the "emotional" category were rated more highly on the emotional dimensions, and women rated them as having more emotional impact than did the men. During retrieval of emotional words (but not neutral words) there was a different pattern of activation among the women compared with the men, with greater activation in bilateral posterior hippocampus and cerebellum, and decreased activity in medial prefrontal cortex, which are brain areas previously implicated in emotion. There were no significant differences in retrieval of emotional versus neutral words, or in differences in memory performance between men and women. The findings suggest differences in cognitive appraisal and involvement of a broader network of brain regions mediating emotion during remembrance of emotional words in women compared with men.

Reproducibility of in vivo brain measures of 5-HT2A receptors with PET and

The test/retest reproducibility of brain measures of 5-HT2A receptors with positron emission tomography (PET) and [18F]deuteroaltanserin was examined in a group of eight healthy human subjects. PET measures of 5-HT2A receptors were obtained under an equilibrium paradigm, with a 40-min PET acquisition starting approximately at 300 min (308+/-11 min) after bolus plus constant infusion of the radiotracer. Three brain outcome measures were obtained at equilibrium, V(3) (ratio of specific brain uptake to free parent plasma concentration of radiotracer), V(3)' (ratio of specific brain uptake to total parent plasma concentration) and RT (ratio of specific to non-displaceable brain uptakes). V(3)' and RT had high test/retest reproducibility, as measured by mean intra-subject% change for cortical brain areas of 14.1 and 11.0%, respectively. They also had high reliability, as measured by mean intra-class correlation coefficients (ICC) for cortical brain areas of 0.86 and 0.88, respectively. V(3) had low test/retest reproducibility, due to high variability in the measures of free parent tracer in plasma. This study supports the feasibility of equilibrium imaging of 5-HT2A receptors with PET and [18F]deuteroaltanserin. The equilibrium imaging method with [18F]deuteroaltanserin allows a single acquisition and blood measurement to provide an image whose pixel values equal a receptor volume of distribution. Since the single image pixel values are proportional to receptor densities, the images can be used in pixel-by-pixel statistical methods, such as SPM, to assess the distribution and density of 5-HT2A receptors in neuropsychiatric disorders.

Comparison of [(18)F]altanserin and [(18)F]deuteroaltanserin for PET imaging of serotonin(2A) receptors in baboon brain: pharmacological studies

The regional distribution in brain, distribution volumes, and pharmacological specificity of the PET 5-HT(2A) receptor radiotracer [(18)F]deuteroaltanserin were evaluated and compared to those of its non-deuterated derivative [(18)F]altanserin. Both radiotracers were administered to baboons by bolus plus constant infusion and PET images were acquired up to 8 h. The time-activity curves for both tracers stabilized between 4 and 6 h. The ratio of total and free parent to metabolites was not significantly different between radiotracers; nevertheless, total cortical R(T) (equilibrium ratio of specific to nondisplaceable brain uptake) was significantly higher (34-78%) for [(18)F]deuteroaltanserin than for [(18)F]altanserin. In contrast, the binding potential (Bmax/K(D)) was similar between radiotracers. [(18)F]Deuteroaltanserin cortical activity was displaced by the 5-HT(2A) receptor antagonist SR 46349B but was not altered by changes in endogenous 5-HT induced by fenfluramine. These findings suggest that [(18)F]deuteroaltanserin is essentially equivalent to [(18)F]altanserin for 5-HT(2A) receptor imaging in the baboon.

Myocardial blood-flow response during mental stress in patients with coronary artery disease

Positron emission tomography was used to quantify changes in myocardial blood flow during mental stress in patients with and without coronary artery disease. Blunted augmentation of myocardial blood flow during mental stress was observed in regions without significant epicardial stenosis.

Persistent changes in myocardial glucose metabolism in vivo during reperfusion of a limited-duration coronary occlusion

BACKGROUND

Rapid reperfusion of an occluded coronary artery salvages regional mechanical function, but this benefit may not be realized for hours or days because of postischemic stunning. Recovery from stunning is incompletely understood but may involve adaptive changes in heart glucose metabolism.

METHODS AND RESULTS

To examine whether reversible coronary occlusion produces sustained changes in regional glucose metabolism in vivo, we performed a 20-minute left coronary artery occlusion followed by 24 hours of open-artery reperfusion in intact rats. Coronary occlusion produced stunning of the anterolateral left ventricle that resolved over 24 hours. When examined at 24 hours, reperfused regions were fully contractile and viable by vital staining and microscopy but demonstrated 25% reduction in blood flow and 50% increased uptake of circulating glucose, as estimated by in vivo [(13)N]NH(3) and [(18)F]fluorodeoxyglucose (FDG) tracer uptake. Reperfused regions had largely inactive glycogen synthase, low rates of glycogen synthesis, and persistent 50% glycogen depletion but increased flux of plasma [1-(13)C]glucose into myocardial [3-(13)C]alanine, indicating preferential shunting of imported glucose away from storage and into glycolysis.

CONCLUSIONS

Sustained increases in regional glycolytic consumption of circulating glucose occur during reperfusion of a limited-duration coronary occlusion. This suggests a role for glycolytic ATP in the recovery from postischemic stunning in vivo. Furthermore, [(13)N]NH(3) /FDG regional mismatch may constitute a clinically accessible late metabolic signature of regional myocardial ischemia.

PET quantification of 5-HT2A receptors in the human brain: a constant infusion paradigm with [18F]altanserin

[18F]altanserin has been used to label serotonin 5-HT2A receptors, which are believed to be important in the pathophysiology of schizophrenia and depression. The purpose of this study was to test the feasibility of a constant infusion paradigm for equilibrium modeling of [18F]altanserin with PET. Kinetic modeling with [18F]altanserin may be hampered by the presence of lipophilic radiometabolites observed in plasma after intravenous administration.

METHODS

Eight healthy volunteers were injected with [18F]altanserin as a bolus (208+/-9 MBq [5.62+/-0.25 mCi]) plus constant infusion (65+/-3 MBq/h [1.76+/-0.08 mCi/h]) ranging from 555 to 626 min (615+/-24 min) after injection. PET acquisitions (10-20 min) and venous blood sampling were performed every 30-60 min throughout the infusion period.

RESULTS

Linear regression analysis revealed that time-activity curves for both brain activity and plasma [18F]altanserin and metabolite concentrations stabilized after about 6 h. This permitted equilibrium modeling and estimation of V3' (ratio of specific uptake [cortical-cerebellar] to total plasma parent concentration after 6 h). Values of V3' ranged from 1.57+/-0.38 for anterior cingulate cortex to 1.02+/-0.39 for frontal cortex. The binding potential V3 (ratio of specific uptake to free plasma parent concentration after 6 h, using group mean f1) was also calculated and ranged from 169+/-41 for anterior cingulate cortex to 110+/-42 for frontal cortex. From 6 h onward, the rate of change for V3' and V3 was only 1.11+/-1.69 %/h.

CONCLUSION

These results demonstrate the feasibility of equilibrium imaging with [18F]altanserin over more than 5 radioactive half-lives and suggest a method to overcome difficulties associated with lipophilic radiolabeled metabolites. The stability in V3 and V3' once equilibrium is achieved suggests that a single PET acquisition obtained at 6 h may provide a reasonable measure of 5-HT2A receptor density.

Kinetic modeling of benzodiazepine receptor binding with PET and high specific activity [(11)C]Iomazenil in healthy human subjects

Quantitation of the PET benzodiazepine receptor antagonist, [(11)C]Iomazenil, using low specific activity radioligand was recently described. The purpose of this study was to quantitate benzodiazepine receptor binding in human subjects using PET and high specific activity [(11)C]Iomazenil. Six healthy human subjects underwent PET imaging following a bolus injection of high specific activity (>100 Ci/mmol) [(11)C]iomazenil. Arterial samples were collected at multiple time points after injection for measurement of unmetabolized total and nonprotein-bound parent compound in plasma. Time activity curves of radioligand concentration in brain and plasma were analyzed using two and three compartment model. Kinetic rate constants of transfer of radioligand between plasma, nonspecifically bound brain tissue, and specifically bound brain tissue compartments were fitted to the model. Values for fitted kinetic rate constants were used in the calculation of measures of benzodiazepine receptor binding, including binding potential (the ratio of receptor density to affinity), and product of BP and the fraction of free nonprotein-bound parent compound (V(3)'). Use of the three compartment model improved the goodness of fit in comparison to the two compartment model. Values for kinetic rate constants and measures of benzodiazepine receptor binding, including BP and V(3)', were similar to results obtained with the SPECT radioligand [(123)I]iomazenil, and a prior report with low specific activity [(11)C]Iomazenil. Kinetic modeling using the three compartment model with PET and high specific activity [(11)C]Iomazenil provides a reliable measure of benzodiazepine receptor binding. Synapse 35:68-77, 2000. Published 2000 Wiley-Liss, Inc.

Quantitation of benzodiazepine receptor binding with PET [11C]iomazenil and SPECT [123I]iomazenil: preliminary results of a direct comparison in healthy human subjects

Although positron emission tomography (PET) and single photon emission computed tomography (SPECT) are increasingly used for quantitation of neuroreceptor binding, almost no studies to date have involved a direct comparison of the two. One study found a high level of agreement between the two techniques, although there was a systematic 30% increase in measures of benzodiazepine receptor binding in SPECT compared with PET. The purpose of the current study was to directly compare quantitation of benzodiazepine receptor binding in the same human subjects using PET and SPECT with high specific activity [11C]iomazenil and [123I]iomazenil, respectively. All subjects were administered a single bolus of high specific activity iomazenil labeled with 11C or 123I followed by dynamic PET or SPECT imaging of the brain. Arterial blood samples were obtained for measurement of metabolite-corrected radioligand in plasma. Compartmental modeling was used to fit values for kinetic rate constants of transfer of radioligand between plasma and brain compartments. These values were used for calculation of binding potential (BP = Bmax/Kd) and product of BP and the fraction of free non-protein-bound parent compound (V3'). Mean values for V3' in PET and SPECT were as follows: temporal cortex 23+/-5 and 22+/-3 ml/g, frontal cortex23+/-6 and 22+/-3 ml/g, occipital cortex 28+/-3 and 31+/-5 ml/g, and striatum 4+/-4 and 7+/-4 ml/g. These preliminary findings indicate that PET and SPECT provide comparable results in quantitation of neuroreceptor binding in the human brain.

A complete remote-control system for reliable preparation of [18F]altanserin

A complete remote control system was constructed for production of the PET 5-HT2A ligand [18F]altanserin by nitro-for-fluoro exchange. Comparing with published methods, the key features include (1) conducting azeotropic distillation and nucleophilic displacement in an open vessel heated by a commercial microwave oven; (2) purifying the product by a single HPLC procedure and (3) removing HPLC solvent by solid phase extraction. The preparation took 114 min with 23% yield and high quality.

Neural correlates of exposure to traumatic pictures and sound in Vietnam combat veterans with and without posttraumatic stress disorder: a positron emission tomography study

BACKGROUND

Patients with posttraumatic stress disorder (PTSD) show a reliable increase in PTSD symptoms and physiological reactivity following exposure to traumatic pictures and sounds. In this study neural correlates of exposure to traumatic pictures and sounds were measured in PTSD.

METHODS

Positron emission tomography and H2[15O] were used to measure cerebral blood flow during exposure to combat-related and neutral pictures and sounds in Vietnam combat veterans with and without PTSD.

RESULTS

Exposure to traumatic material in PTSD (but not non-PTSD) subjects resulted in a decrease in blood flow in medial prefrontal cortex (area 25), an area postulated to play a role in emotion through inhibition of amygdala responsiveness. Non-PTSD subjects activated anterior cingulate (area 24) to a greater degree than PTSD patients. There were also differences in cerebral blood flow response in areas involved in memory and visuospatial processing (and by extension response to threat), including posterior cingulate (area 23), precentral (motor) and inferior parietal cortex, and lingual gyrus. There was a pattern of increases in PTSD and decreases in non-PTSD subjects in these areas.

CONCLUSIONS

The findings suggest that functional alternations in specific cortical and subcortical brain areas involved in memory, visuospatial processing, and emotion underlie the symptoms of patients with PTSD.

Cerebral cortical hyperactivation in response to mental stress in patients with coronary artery disease

The central nervous system (CNS) effects of mental stress in patients with coronary artery disease (CAD) are unexplored. The present study used positron emission tomography (PET) to measure brain correlates of mental stress induced by an arithmetic serial subtraction task in CAD and healthy subjects. Mental stress resulted in hyperactivation in CAD patients compared with healthy subjects in several brain areas including the left parietal cortex [angular gyrus/parallel sulcus (area 39)], left anterior cingulate (area 32), right visual association cortex (area 18), left fusiform gyrus, and cerebellum. These same regions were activated within the CAD patient group during mental stress versus control conditions. In the group of healthy subjects, activation was significant only in the left inferior frontal gyrus during mental stress compared with counting control. Decreases in blood flow also were produced by mental stress in CAD versus healthy subjects in right thalamus (lateral dorsal, lateral posterior), right superior frontal gyrus (areas 32, 24, and 10), and right middle temporal gyrus (area 21) (in the region of the auditory association cortex). Of particular interest, a subgroup of CAD patients that developed painless myocardial ischemia during mental stress had hyperactivation in the left hippocampus and inferior parietal lobule (area 40), left middle (area 10) and superior frontal gyrus (area 8), temporal pole, and visual association cortex (area 18), and a concomitant decrease in activation observed in the anterior cingulate bilaterally, right middle and superior frontal gyri, and right visual association cortex (area 18) compared with CAD patients without myocardial ischemia. These findings demonstrate an exaggerated cerebral cortical response and exaggerated asymmetry to mental stress in individuals with CAD.

Effects of mental stress on left ventricular and peripheral vascular performance in patients with coronary artery disease

OBJECTIVES

We sought to investigate the mechanism of a mental stress-induced fall in left ventricular ejection fraction (LVEF) in patients with coronary artery disease.

BACKGROUND

Mental stress induces a fall in LVEF in a significant proportion of patients with coronary artery disease. This is accompanied by an increase in heart rate, blood pressure and rate-pressure product. Whether the mental stress-induced fall in LVEF is due to myocardial ischemia, altered loading conditions or a combination of both is not clear.

METHODS

Left ventricular (LV) function was studied noninvasively by serial equilibrium radionuclide angiocardiography and simultaneous measurement of peak power, a relatively afterload-independent index of LV contractility, in 21 patients with coronary artery disease (17 men, 4 women) and 9 normal subjects (6 men, 3 women) at baseline, during mental stress and during exercise. Peripheral vascular resistance (PVR), cardiac output (CO), arterial and end-systolic ventricular elastance (Ea, Ees,) and ventriculoarterial coupling (V/AC) were also calculated. Patients underwent two types of mental stress-mental arithmetic and anger recall-as well as symptom-limited semisupine bicycle exercise.

RESULTS

Nine patients (43%) had an absolute fall in LVEF of > or = 5% (Group I) in response to at least one of the mental stressors, whereas the remaining patients did not (Group II). Group I and Group II patients were similar in terms of baseline characteristics. Both groups showed a significant but comparable increase in systolic blood pressure (15+/-7 vs. 9+/-10 mm Hg, p=0.12) and a slight increase in heart rate (7+/-4 vs. 8+/-7 beats/min, p=0.6) and a comparable increase in rate-pressure product (2.2+/-0.9 vs. 1.9+/-1.2 beats/min x mm Hg, p=0.6) with mental stress. However, PVR increased in Group I and decreased in Group II (252+/-205 vs. -42+/-230 dynes x s x cm(-5), p=0.006), and CO decreased in Group I and increased in Group II (-0.2+/-0.4 vs. 0.6+/-0.7 liters/min, p=0.02) with mental stress. There was no difference in the change in peak power (p=0.4) with mental stress. With exercise, an increase in systolic blood pressure, heart rate, rate-pressure product and CO and a fall in PVR were similar in both groups. Of the two mental stressors, anger recall resulted in a greater fall in LVEF and a greater increase in diastolic blood pressure. Exercise resulted in a fall in LVEF in 7 patients (33%). However, exercise-induced changes in LVEF and hemodynamic variables were not predictive of mental stress-induced changes in LVEF and hemodynamic variables. Conclusions. Abnormal PVR and Ea responses to mental stress and exercise are observed in patients with a mental stress-induced fall in LVEF. Peripheral vasoconstrictive responses to mental stress contribute significantly toward a mental stress-induced fall in LVEF.

Effect of hyperinsulinemia on myocardial fluorine-18-FDG uptake

This study was performed to evaluate the effect of insulin on myocardial kinetics of 18F-fluorodeoxyglucose (FDG) and glucose in patients with ischemic heart disease.

METHODS

Twelve male patients (age range 54-79 yr; mean age 69 +/- 8 yr) were studied during the fasting awake state. Patients with diabetes and previous myocardial infarction of the left anterior descending vascular bed were excluded from the study. Patients were injected with a 185-MBq (5-mCi) bolus of FDG during arterial and coronary sinus catheterization. Thirty minutes after FDG injection, paired basal arterial and coronary sinus blood samples were taken for the measurement of FDG and glucose uptake. Thereafter, a primed (100 mU x m(-2) x min(-1) for 10 min) continuous (50 mU x m(-2) x min(-1) infusion of insulin was administered for 60 min using the euglycemic clamp technique, and blood samples were repeated. Blood samples also were taken periodically for the measurement of arterial free fatty acids and insulin.

RESULTS

Euglycemic insulin infusion lowered arterial concentrations of free fatty acids, reducing myocardial extraction of free fatty acids by 85% and stimulated uptake of glucose and FDG. Myocardial glucose and FDG extraction fractions (%) increased from 1 +/- 1 and 2 +/- 2 at baseline to 8 +/- 2 and 10 +/- 3 during insulin infusion, respectively. The lumped constant value was estimated to be 1.44 +/- 0.14 (r = 0.87) for the fasted state, 0.99 +/- 0.07 (r = 0.74) during insulin infusion and 1.00 +/- 0.05 (r = 0.92) when both groups of data were pooled together.

CONCLUSION

The data obtained in this study show that FDG uptake quantitatively traces glucose uptake during physiological hyperinsulinemia in patients with ischemic heart disease.

Effect of left ventricular function on the assessment of myocardial viability by technectium-99m sestamibi and correlation with positron emission tomography in patients with healed myocardial infarcts or stable angina pectoris, or both

The accuracy of technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) for the assessment of myocardial viability in patients with coronary artery disease and left ventricular (LV) dysfunction is not defined completely. This study determines whether the performance of Tc-99m sestamibi SPECT for viability detection differs between patients with mild-to-moderate coronary artery disease. Patients with regional and/or global LV dysfunction were separated into 2 groups on the basis of LV ejection fraction (EF) at rest: group 1 (LVEF > 25%, mean 36 +/- 6%, n = 9), and group 2 (LVEF < or = 25%, mean 17 +/- 5%, n = 11). All patients underwent semiquantitative Tc-99m sestamibi SPECT and positron emission tomography (PET) at rest with N-13 ammonia and F-18 fluorodeoxyglucose. The overall regional concordance of SPECT and PET for viability detection was 89% in group 1 and 78% in group 2 (p = 0.002). Discordance in group 2 was almost exclusively due to PET viable and/or SPECT nonviable regions. In regions with hypoperfusion at rest by PET, concordance was 78% in group 1 and only 64% in group 2 (p = 0.0015). In regions with reduced perfusion and relatively increased metabolic activity ("flow: metabolism mismatch"), Tc-99m sestamibi SPECT identified 88% of regions in group 1 as viable, but only 42% of regions in group 2 (p = 0.002). Thus, while Tc-99m sestamibi semiquantitative SPECT at rest shows a good concordance with PET for the detection of myocardial viability in patients with coronary artery disease with mild-to-moderate LV dysfunction, it may underestimate myocardial viability in patients with severe LV dysfunction, particularly in those patients with hypoperfusion at rest as assessed by PET.

Radiosynthesis and PET imaging of [N-methyl-11C]LY257327 as a tracer for 5-HT transporters

No-carrier-added [N-methyl-11C]LY257327 was synthesized by methylation of the free base of the desmethyl precursor LY214281 with [11C]methyl iodide in anhydrous acetonitrile. Synthesis time was 52 +/- 3 min, radiochemical yield (based on [11C]methyl iodide) was 35 +/- 8%, radiochemical purity was 99 +/- 1%, and specific activity at EOB was 3900 +/- 1300 mCi/mumol. Two in vivo studies in baboon were carried out before and after pretreatment with the selective serotonin reuptake inhibitor citalopram. The first experiment showed high accumulation of radioactivity in midbrain, striatum, and thalamus, with slightly lower accumulation in the occipital and cerebellum regions. The radioactivity concentration peaked 5 min postinjection, decreasing steadily for the rest of the scanning time. The second experiment (blocked with citalopram) showed only partial inhibition of incorporation in all of the same brain regions. Although [N-methyl-11C]LY257327 displayed high brain uptake (5% of injected dose at 5 min postinjection) and localized in serotonergic areas of the brain, its target-to-nontarget ratio and its insensitivity to citalopram blocking suggest that its accumulation is dominated by nonspecific uptake. Therefore, [N-methyl-11C]LY257327 is not a useful agent for measuring serotonin reuptake sites in vivo by positron emission tomography.

Positron emission tomography measurement of cerebral metabolic correlates of tryptophan depletion-induced depressive relapse

BACKGROUND

Short-term depletion of plasma tryptophan has been shown to result in depressive relapse in patients with remission of major depression. Positron emission tomography and single photon emission computed tomography studies implicated the dorsolateral prefrontal cortex, orbitofrontal cortex, thalamus, and caudate nucleus in the pathogenesis of depression. The purpose of this study was to measure cerebral metabolic correlates of tryptophan depletion-induced depressive relapse.

METHODS

Patients diagnosed as having major depression (N = 21) who clinically improved with serotonin reuptake inhibitors underwent 2 test days involving tryptophan depletion or placebo, followed 6 hours later by positron emission tomography scanning with fludeoxy-glucose F18. Brain metabolism was compared in patients with (n = 7) and without (n = 14) a tryptophan depletion-induced depressive relapse.

RESULTS

Tryptophan depletion resulted in a decrease in brain metabolism in the middle frontal gyrus (dorsolateral prefrontal cortex), thalamus, and orbitofrontal cortex in patients with a depletion-induced depressive relapse (but not in patients without depletion-induced relapse). Decreased brain metabolism in these regions correlated with increased depressive symptoms. Baseline metabolism was increased in prefrontal and limbic regions in relapse-prone patients.

CONCLUSION

Specific brain regions, including the middle frontal gyrus, thalamus, and orbitofrontal cortex, may mediate the symptoms of patients with major depression.

Positron emission tomography measurement of cerebral metabolic correlates of yohimbine administration in combat-related posttraumatic stress disorder

BACKGROUND

We have previously reported an increase in symptoms of anxiety in patients with posttraumatic stress disorder (PTSD) following administration of the beta 2-antagonist yohimbine, which stimulates brain norepinephrine release. Preclinical studies show decreased metabolism in the neocortex and the caudate nucleus with high-dose yohimbine-induced norepinephrine release, but low levels of norepinephrine release result in an increase in metabolism in these areas.

METHODS

We used positron emission tomography and fludeoxyglucose F 18 to measure brain metabolism in Vietnam combat veterans with PTSD (n = 10) and healthy age-matched control subjects (n = 10), following administration of yohimbine (0.4 mg/kg) or placebo in a randomized, double-blind fashion.

RESULTS

Yohimbine resulted in a significant increase in anxiety in the patients with PTSD, but not in healthy subjects. There was a significant difference in brain metabolic response to yohimbine in patients with PTSD compared with healthy subjects in prefrontal, temporal, parietal, and orbitofrontal cortexes. Metabolism tended to decrease in patients with PTSD and increase in healthy subjects following administration of yohimbine.

CONCLUSION

These findings are consistent with our previous hypothesis of enhanced norepinephrine release in the brain with yohimbine in patients with PTSD.

Diagnosis of pedal osteomyelitis with Tc-99m HMPAO labeled leukocytes

The diagnosis of pedal osteomyelitis is often complicated by the presence of pre-existing bony abnormalities. In this study, the utility of radiolabeled white blood cell imaging for the detection of complicated pedal osteomyelitis was evaluated. Twenty-seven men and women were prospectively enrolled and underwent plain film radiography, three-phase bone scan, and Tc-99m hexamethylpropylamine oxine white blood cell scintigraphy of their feet. The presence or absence of osteomyelitis was confirmed in all subjects by microbiologic and histopatholigic analysis of resected bone tissue. The results indicated that white blood cell imaging was more sensitive (90%) and specific (86%) for infection than either bone scan (75% sensitive, 29% specific) or plain film radiography (55% sensitive, 57% specific). This preliminary study suggests that Tc-99m hexamethylpropylamine oxine-labeled white blood cell scintigraphy is a simple, accurate test for the detection of pedal osteomyelitis.

Autoregulation of myocardial glycogen concentration during intermittent hypoxia

During hypoxia, the heart consumes glycogen to generate ATP. Tolerance of repetitive hypoxia logically requires prompt replenishment of glycogen, a process whose regulation is not fully understood. To examine this, we imposed a defined hypoxic stimulus on the rat heart while varying its workload. In intact rats, hypoxia reduced myocardial glycogen approximately 30% and increased both the fraction of glycogen synthase in its physiologically active (GS I) form (from 0.24 +/- 0.06 to 0.82 +/- 0.07; P < 0.005) and glycogen synthesis (from 0.087 +/- 0.011 to 0.375 +/- 0.046 mumol.g-1.min-1; P < 0.005). Reducing cardiac work (with propranolol or heterotopic transplantation) reduced glycogen breakdown, glycogen synthase activation, and glycogen synthesis in parallel, stepwise fashion in intact rats. Correspondingly, hypoxia increased GS I activity in the perfused heart in vitro, but only under conditions where glycogen was consumed. This suggests myocardial glycogen synthase is activated by systemic hypoxia and catalyzes rapid posthypoxic glycogen synthesis. Hypoxic glycogen synthase activation appears to be a proportionate, wholly intrinsic response to local glycogenolysis, operating to preserve myocardial glycogen stores independent of any extracardiac mediator of carbohydrate metabolism.

Comparison of nifedipine GITS and hydrochlorothiazide in the management of elderly patients with stage I-III diastolic hypertension

A randomized, double blind, parallel study was performed to compare the effects of nifedipine gastrointestinal therapeutic system (GITS) to hydrochlorothiazide (HCTZ) in the management of the elderly hypertensive. Eighteen patients, mean age 65 +/- 5 years, with Stage I-III diastolic hypertension (sitting diastolic BP between 90 and 115 mm HG) were included in each treatment group. Following a 2 to 8 week placebo washout phase, patients received either nifedipine GITS or HCTZ and were titrated over 5 weeks to achieve a goal diastolic blood pressure less than 90 mm Hg. Patients were then continued on medication during an 8 week maintenance phase. Treatment effect on systolic and diastolic blood pressure was assessed. Serum electrolytes, lipids, blood urea nitrogen, and creatinine were measured before and after treatment. Posttreatment changes in renal and cardiovascular function, as well as left ventricular mass were evaluated. The results showed significant reductions in systolic and diastolic blood pressure with both drugs; no treatment difference was found, although goal blood pressure was achieved more rapidly with nifedipine GITS (28 v 34 days, P < .05). BUN was significantly increased only after diuretic therapy (P < .01) and serum potassium fell to a greater degree with HCTZ (0.3 mEq/L v 0.1 mEq/L) than with nifedipine GITS. No statistically significant changes in left ventricular mass, ejection fraction, glomerular filtration rate, or renal blood flow were seen after therapy with either drug. However, the time peak LV diastolic filling rate decreased with nifedipine GITS (197 to 164 msec) and increased with HCTZ (172 to 198 msec). This treatment difference approached statistical significance (P = .07). Adverse side effects of treatment were reported by 50% of nifedipine GITS patients and 28% of patients treated with HCTZ. This treatment difference was not statistically significant. We conclude that both nifedipine GITS and HCTZ monotherapy provide significant blood pressure reduction in older hypertensives with Stage I-III diastolic hypertension. Both drugs are well tolerated with no significant adverse effect on renal or cardiovascular function after short term therapy.

Left ventricular diastolic function: physiology, methods of assessment, and clinical significance

Diastole, that portion of the cardiac cycle that begins with isovolumic relaxation and ends with mitral valve closure, results in ventricular filling and involves both active (energy-dependent) and passive processes. The interactions between active processes (myocardial relaxation) that primarily influence early ventricular filling and passive processes, such as loading conditions, myocardial compliance, and valvular disease, are complex. Clinical methods to assess ventricular filling include cardiac catheterization, radionuclide angiography, and echocardiography. Any measurements of diastolic function must be made with an understanding of the determinants of ventricular filling and the limitations of the diagnostic test. Many cardiac disorders are characterized by elevated pulmonary venous pressures in the face of normal systolic ventricular function, which suggests a primary abnormality of diastolic function. Abnormalities in diastolic function have been observed in coronary artery disease, congestive heart failure (with and without systolic dysfunction), hypertrophic cardiomyopathy, hypertension, and in healthy elderly subjects. Identification of these abnormalities may be useful clinically, particularly in patients with symptoms of heart failure and normal systolic function. Data are not available to determine the optimal therapy for such patients, although evidence suggests that calcium channel blockers, beta blockers, and agents that reverse myocardial hypertrophy may be useful. This review briefly summarizes the physiology of diastole, the methods of clinical assessment of diastolic function, and the role of diastolic function in cardiovascular disease.

Kinetic analysis of technetium-99m-labeled nitroimidazole (BMS-181321) as a tracer of myocardial hypoxia

BACKGROUND

Experimental data have indicated that [99mTc]-nitroimidazole (BMS-181321) is preferentially taken up in hypoxic tissue; its kinetics, however, has not been fully investigated. The purpose of this study was to address the relation between perfusate oxygen level and myocardial retention of [99mTc]nitroimidazole.

METHODS AND RESULTS

Bolus injection and constant infusion experiments were performed in Langendorff buffer-perfused rat hearts in normoxic and hypoxic conditions. Data were acquired with a pair of NaI detectors. The initial clearance rate of [99mTc]nitroimidazole was approximately 20 seconds and independent of perfusate oxygen level. The slow clearance rate was greater than 3 hours in all perfusion conditions. The tissue retention of [99mTc]nitroimidazole varied from 0.61 +/- 0.14% in normoxic conditions to 5.94 +/- 1.16% in the most severe hypoxic conditions. In addition, tissue retention was inversely proportional to perfusate oxygen level in a sigmoidal manner. The constant infusion experiments established that the binding rate at 25% oxygen level (1.94 +/- 0.38 mL of perfusate/min-g dry wt) was twofold of that at 40% and sevenfold at 100%. The binding rate of [99mTc]nitroimidazole was independent of the perfusion sequence, suggesting irreversible binding.

CONCLUSIONS

These data indicate that [99mTc]nitroimidazole may be a useful tracer for the identification of myocardial hypoxia. A sigmoidal relation was demonstrated for the uptake of the tracer, which suggests that a threshold level of hypoxia is necessary for the uptake of the tracer.

Synthesis and PET imaging of the benzodiazepine receptor tracer [N-methyl-11C]iomazenil

The central benzodiazepine receptor tracer [N-methyl-11C]iomazenil (Ro 16-0154) was synthesized by alkylation of the desmethyl precursor noriomazenil with [11C]methyl iodide. The [11C]CH3I (prepared by reduction of [11C]CO2 with LiA1H4 followed by reaction with HI) was reacted with noriomazenil in N,N-dimethylformamide and Bu4N+OH- for 1 min at 80 degrees C and purified by HPLC (C18, 34% CH3CN/H2O 7 mL/min). The product was obtained with synthesis time 35 +/- 5 min (mean +/- SD, n = 7), radiochemical yield (EOB) 36 +/- 16%, radiochemical purity 99 +/- 1%, and specific activity 5100 +/- 2800 mCi/mumol. Absorbed radiation doses were calculated from previously acquired human biodistribution data. The urinary bladder wall received the highest dose (0.099 mGy/MBq) for 4.8 h voiding interval and the effective dose equivalent was 0.015 mSv/MBq. After i.v. injection of [11C]iomazenil in an adult baboon or healthy human volunteer, radioactivity accumulated in the cortex with time-activity curves in agreement with results obtained with [11C]flumazenil PET and [123I]iomazenil SPECT studies. The count rate was sufficient to obtain quantitative images up to 2 h post-injection with a 14 mCi injection. These results suggest that [11C]iomazenil will be a useful agent for measuring benzodiazepine receptors in vivo by positron emission tomography.

Prognostic implications of mental stress-induced silent left ventricular dysfunction in patients with stable angina pectoris

Thirty patients with stable angina pectoris and ischemia on stress perfusion imaging underwent continuous ambulatory left ventricular (LV) function monitoring. Mental stress was induced by mental arithmetic. Fifteen patients developed transient LV dysfunction during mental arithmetic. Patients were followed for 2 years for adverse cardiac events. Twelve patients had cardiac events over 1 year (myocardial infarction in 4, and unstable angina in 8). Nine of 15 patients (60%) with and only 3 of 15 (20%) without mental stress-induced LV dysfunction developed cardiac events (p = 0.025). A higher proportion of patients with cardiac events were taking beta blockers (p = 0.01) and had lower resting heart rates (p = 0.002) than those without cardiac events. There was no difference in the baseline characteristics between the groups of patients with and without cardiac events. At 2-year follow-up, 10 of 15 patients (67%) with mental stress-induced LV dysfunction had adverse events compared with only 4 of 15 (27%) with no mental stress-induced LV dysfunction (p = 0.025). Thus, in this cohort of patients with stable angina pectoris, mental stress-induced LV dysfunction was associated with higher cardiac events on follow-up. The exact mechanism of this association is not clear. Mental stress may be a trigger for adverse cardiac events in these patients. Transient LV dysfunction in response to mental stress may be a marker of abnormal cardiovascular reactivity to emotional and psychological stimuli in patients with coronary artery disease and may be useful for risk stratification.

Comparison of sestamibi single-photon emission computed tomography with positron emission tomography for estimating left ventricular myocardial viability

Technetium-99m methoxyisobutyl isonitrile (technetium-99m sestamibi [MIBI]) is distributed in the myocardium according to blood flow. Reports comparing stress rest sestamibi protocols with reinjection thallium or resting fluorodeoxyglucose (FDG), or both, in patients with coronary artery disease have shown appreciable discordance regarding myocardial viability in these settings. We performed this analysis with regard to regional comparisons within discordant segments and made comparisons in a subset of patients who underwent revascularization. Thirty-seven patients with coronary artery disease had single-photon emission computed tomography MIBI, N-13 ammonia/18FDG positron emission tomography (PET), and radionuclide ventriculography performed at rest. One hundred two segments were viable and 29 were nonviable by both MIBI and FDG. The concordance was 71%. In MIBI nonviable/FDG viable segments, most of the discordance was in the inferior wall. In MIBI nonviable discordant segments, FDG accurately predicted an increase in percent regional ejection fraction (preoperative 36% [+/- 5 SE] to postoperative 48% [+/- 5.5 SE][p < 0.0006]). MIBI underestimates myocardial viability as assessed by PET. Seventy-one percent of myocardial segments were concordant by both quantitative sestamibi single-photon emission computed tomography and FDG PET. Discordance in MIBI nonviable segments was predominantly in the inferior wall. PET can be helpful in detecting myocardial viability in patients suspected of having had MIBI nonviability in the inferior wall.

Reverse redistribution on planar thallium scintigraphy: relationship to resting thallium uptake and long-term outcome

Reverse redistribution (RR) of thallium-201 has been associated with both acute and healed myocardial infarction, and with recent thrombolysis. The physiologic basis for RR in coronary artery disease (CAD) is unclear but may be related to an admixture of viable and scarred myocardium within the RR segment. We performed thallium reinjection imaging at rest to better characterize RR defects in patients with chronic CAD. We found enhanced uptake of 201Tl in 52% of RR segments after reinjection, consistent with significant regional viability that was not evident on redistribution images. We then used a logistic multiple regression analysis to determine whether RR alone or in combination with other scintigraphic findings could predict patient outcome. The results showed that severe RR was an independent predictor of patient outcome. We conclude that RR may have prognostic significance in chronic CAD.

Relationship between reverse redistribution on planar thallium scintigraphy and regional myocardial viability: a correlative PET study

The purpose of this study was to assess myocardial metabolic activity in the area of reverse redistribution and determine the prognostic value of reverse redistribution and PET imaging. Reverse redistribution is thought to be a manifestation of reperfusion therapy and associated with a favorable clinical outcome. Preliminary observations from the Thrombolysis and Myocardial Infarction (TIMI) trial suggest that reverse redistribution is associated with higher incidence of future cardiac events.

METHODS

Thirty-two patients with chronic coronary artery disease and reverse redistribution on planar thallium scintigraphy had PET 13NH3/18FDG imaging. Radionuclide angiocardiography was performed in 23 patients.

RESULTS

Fifty segments showed reverse redistribution on planar thallium images; 19 segments had normal 13NH3 and 18FDG uptake and 17 were ischemic by PET criteria. Thus, a total of 72% (36 of 50) of reverse redistribution segments were PET viable. Sixty-one percent of segments with abnormal regional wall motion and reverse redistribution were PET scar. On follow-up, 31% (10/32) had a cardiac event (nine unstable angina and one myocardial infarction). Fifty percent of patients (5/10) with cardiac events had severe reverse redistribution and PET viability versus 9% (2/22) without cardiac events (p = 0.01).

CONCLUSIONS

The majority of thallium reverse redistribution segments was PET viable as judged by 18FDG uptake. Viability in areas of reverse redistribution is not inferred by regional wall motion analysis. Regional PET viability identifies patients with reverse redistribution with a higher likelihood of future cardiovascular events. PET viability assessment may be helpful with the impact of reverse redistribution on planar thallium scintigraphy.

Role of behavioral and psychological factors in mental stress-induced silent left ventricular dysfunction in coronary artery disease

OBJECTIVES

We examined the relationship of the psychological profile to left ventricular dysfunction induced during mental stress.

BACKGROUND

The contribution of psychological factors to mental stress-provoked silent myocardial ischemia has not been explored.

METHODS

Thirty patients with chronic stable coronary artery disease and a reversible defect on stress thallium-201 imaging completed a psychological assessment by questionnaire and Structured Interview, serially administered mental stress and brief walking exercise. Blood pressure, electrocardiogram (ECG) and left ventricular indexes were obtained by ambulatory serial radionuclide ventriculography. Silent ventricular dysfunction was defined by a decrease > or = 0.05 in ejection fraction or > or = 1 mm in ST segment on the ECG in the absence of symptoms.

RESULTS

Of the 30 patients, 15 (Group I) had evidence of silent left ventricular dysfunction during mental arithmetic. The other 15 (Group II) showed no change. In addition, 18 of 30 patients had this dysfunction during the Structured Interview. Both ischemic and nonischemic groups developed comparable and significant increases in heart rate and blood pressure. Group I patients were distinguished by higher scores on measures of aggressive responding (p < 0.001), trait anger (p < 0.0001), hostile affect (p < 0.003) and an index of behavioral reactivity (p < 0.003) and a lower score on anger control (p < 0.001). No other variables, including historical and clinical indexes, discriminated between the two groups.

CONCLUSIONS

Patients with coronary artery disease and mental stress-provoked silent ventricular dysfunction were distinguished by a psychological profile consistent with emotional reactivity to social interaction and mental provocation, with anger as the predominant affective state. Patients with such a profile may be at risk of frequent silent left ventricular dysfunction.

The radionuclide assessment of left ventricular diastolic filling: methodology and clinical significance

The radionuclide measurement of diastolic performance may provide a rapid noninvasive index available in the clinical setting. These measurements may be used to detect coronary artery disease, manifestations of hypertensive heart disease, isolated diastolic heart failure, and hypertrophic cardiomyopathy. The various radionuclide methods to measure diastolic filling are influenced by technological considerations, as well as applying the results in the appropriate clinical context. The importance of these derived measurements and how they correspond to various pathophysiological presentations will be discussed.

Long-term outcome in patients with congestive heart failure and intact systolic left ventricular performance

Congestive heart failure (CHF) is typically associated with impaired left ventricular (LV) systolic performance. Few reports exist describing the long-term outcome in patients with CHF and normal LV systolic function. Fifty-two patients initially hospitalized with CHF and intact LV function (ejection fraction greater than or equal to 45%) were followed for 7 years. Mean age when initially identified was 71 +/- 11 years (range 36 to 96), and average LV ejection fraction was 61 +/- 11%. CHF was graded by a clinicoradiographic index, with a mean of 7.0 +/- 2.3 (range 3 to 12, 13 indicates worst CHF). A third heart sound was present in 19 patients (37%), and 17 (33%) had presented with acute pulmonary edema. Principal cardiovascular diagnoses were coronary artery disease in 27 (52%), hypertensive heart disease in 16 (31%) and restrictive cardiomyopathy in 7 (13%). At 7 years, cardiovascular mortality was 46% (24 of 52), and noncardiovascular mortality was 10% (5 of 52). Survival was not correlated with age, principal diagnosis, third heart sound, pulmonary edema at presentation, LV ejection fraction, or presence or degree of LV diastolic dysfunction. Cardiovascular morbidity, consisting of nonfatal recurrent CHF, myocardial infarction, unstable angina or other cardiovascular events occurred in 29% (15 of 52). Combined cardiovascular mortality and morbidity was 75% (39 of 52). In patients with CHF, intact LV systolic function does not confer the same favorable prognosis it defines in other clinical situations. For such patients, the risk of future cardiovascular events is high, a finding that should be considered when designing therapeutic strategies in this group.

Left ventricular diastolic function during positive end-expiratory pressure. Impact of right ventricular ischemia and ventricular interaction

The individual and additive effects of positive end-expiratory pressure (PEEP) and right coronary artery (RCA) occlusion on left ventricular end-diastolic pressure-volume relations (LVEDPVR) were examined in six anesthetized dogs. Right ventricular (RV) and left ventricular (LV) ejection fractions (EF), end-diastolic volume (EDV) and end-systolic volumes (ESV) were measured by thermodilution as PEEP was added before and after RCA occlusion. PEEP alone caused a decline in cardiac output, transmural left atrial pressure (LAP) (6.0 +/- 0.6 to 3.2 +/- 1.4 mm Hg, p less than 0.05), and LVEDV (49 +/- 3 to 36 +/- 4 ml, p less than 0.05). RVEDV, the mean slope (+/- SD) of the LVEDPVR (0.37 +/- 0.16 to 0.30 +/- 0.19) and LAP at a common LV volume (35 ml, V35) did not change with PEEP. RCA occlusion caused cardiac output and RVEF (38 +/- 5 to 27 +/- 5%, p less than 0.05) to decline and RVESV (25 +/- 4 to 33 +/- 6 ml, p less than 0.05) to increase. RVEDV, the slope of the LVEDPVR, and LAP at V35 were unchanged from baseline. The addition of PEEP after RCA occlusion caused cardiac output to decline further. However, unlike before occlusion, there was no change in LAP (6.5 +/- 1.3 to 5.0 +/- 1.4 mm Hg) despite a decline in LVEDV (47 +/- 3 to 29 +/- 6 ml, p less than 0.05). RVESV and RVEDV increased with PEEP after RCA occlusion as did LAP at V35. The slope of the mean LVEDPVR tended to increase (0.98 +/- 1.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Thallium-201 for assessment of myocardial viability: quantitative comparison of 24-hour redistribution imaging with imaging after reinjection at rest

Redistribution thallium-201 imaging 2 to 4 h after exercise may be incomplete and therefore may be inadequate to fully assess myocardial variability. Late redistribution imaging 24 h after exercise has been proposed to overcome this limitation of thallium stress imaging. However, because of poor count density the image quality on these studies is often suboptimal. In the present study the diagnostic information on 24-h planar thallium redistribution images was compared with that on images obtained after a reinjection of thallium at rest. Eighty-four patients with a stress thallium-201 defect had delayed redistribution imaging after 2 to 4 h and 24 h later, and again after an injection of thallium at rest. Defect reversibility on 24-h redistribution images was compared quantitatively with that on images after injection of thallium at rest. The quality of thallium images at rest was consistently better than that of 24-h redistribution images. Poor quality studies occurred in 13% of 24-h redistribution images compared with 0.4% of the studies at rest. Significantly more defect reversibility was detected on images after the reinjection at rest. Of 41 patients who appeared to have a fixed defect at 2- to 4-h redistribution imaging, 11 (27%) had a reversible defect by 24-h redistribution imaging compared with 29 (71%) after thallium-201 reinjection. No clinical variables at the time of stress testing were predictive of late defect reversibility. It is concluded that in patients with fixed a thallium defect at 2 to 4 h after exercise, reimaging after a reinjection at rest provides better diagnostic information than does 24-h late redistribution imaging.

Reproducibility of quantitative planar thallium-201 scintigraphy: quantitative criteria for reversibility of myocardial perfusion defects

Fifty-two paired stress/delayed planar 201TI studies (27 exercise studies, 25 dipyridamole studies) were processed twice by seven technologists to assess inter- and intraobserver variability. The reproducibility was inversely related to the size of 201TI perfusion abnormalities. Intraobserver variability was not different between exercise and dipyridamole studies for lesions of similar size. Based upon intraobserver variability, objective quantitative criteria for reversibility of perfusion abnormalities were defined. These objective criteria were tested prospectively in a separate group of 35 201TI studies and compared with the subjective interpretation of quantitative circumferential profiles. Overall, exact agreement existed in 78% of images (kappa statistic k = 0.66). We conclude that quantification of planar 201TI scans is highly reproducible, with acceptable inter- and intraobserver variability. Objective criteria for lesion reversibility correlated well with analysis by experienced observers.

Usefulness of verapamil for congestive heart failure associated with abnormal left ventricular diastolic filling and normal left ventricular systolic performance

Normal left ventricular systolic performance with impaired left ventricular diastolic filling may be present in a substantial number of patients with congestive heart failure (CHF). To evaluate the effect of oral verapamil in this subset, 20 men (mean age 68 +/- 5 years) with CHF, intact left ventricular function (ejection fraction greater than 45%) and abnormal diastolic filling (peak filling rate less than 2.5 end-diastolic volumes per second [edv/s]) were studied in a placebo-controlled, double-blind 5-week crossover trial. All patients underwent echocardiography to rule out significant valvular disease, and thallium-201 stress scintigraphy to exclude major active ischemia. Compared to baseline values, verapamil significantly improved exercise capacity by 33% (13.9 +/- 4.3 vs 10.7 +/- 3.4 minutes at baseline) and peak filling rate by 30% (2.29 +/- 0.54 vs 1.85 +/- 0.45 edv/s at baseline) (all p less than 0.05). Placebo values were 12.3 +/- 4.0 minutes and 2.16 +/- 0.48 edv/s, respectively (difference not significant for both). Improvement from baseline in an objective clinico-radiographic heart failure score (scale 0 to 13) was significantly greater with verapamil compared to placebo (median improvement in score: 3 vs 1, p less than 0.01). Mean ejection fraction and systolic blood pressure were unchanged from baseline; diastolic blood pressure and heart rate decreased to a small degree. Verapamil may have therapeutic efficacy in patients with CHF, preserved systolic function and impaired diastolic filling.

Coronary flow limits right ventricular performance during positive end-expiratory pressure

The effect of positive end-expiratory pressure (PEEP) on right ventricular performance and myocardial blood flow was determined in 16 dogs before and after right coronary artery (RCA) occlusion. Right ventricular ejection fraction (RVEF), end-diastolic volume (EDV) and end-ejection volume were measured by thermodilution. Right ventricular end-ejection pressure-volume relations (RVEEPVR) were determined at baseline and at 20 cm H2O PEEP, both before and after RCA occlusion. In four of the dogs, RVEEPVR were also determined at 10 cm H2O PEEP after RCA occlusion. With intact RCA flow, RVEF declined with PEEP (37 +/- 5 to 19 +/- 6%) with no significant change in EDV (50 +/- 11 to 42 +/- 11 ml) or end-ejection volume (31 +/- 7 to 36 +/- 9 ml). RVEEPVR and right ventricular myocardial blood flow were also unchanged with PEEP. After RCA occlusion, RVEF declined with PEEP (27 +/- 4 to 15 +/- 5%) in association with a significant increase in end-ejection volume (39 +/- 8 to 49 +/- 10 ml), but no change in EDV (53 to 55 ml). In addition, RVEEPVR and myocardial blood flow declined with RCA occlusion, and declined further with 20 cm H2O, but not with 10 cm H2O PEEP, after RCA occlusion. Therefore, in this experimental model, right ventricular performance was adversely affected during PEEP when right coronary blood flow was limited.

Differing responses in right and left ventricular filling, loading and volumes during positive end-expiratory pressure

Using a combined hemodynamic and radionuclide technique, 20 patients with varied ventricular function were evaluated during positive end-expiratory pressure (PEEP) application. Left ventricular (LV) and right ventricular (RV) ejection fractions and cardiac output were measured, and ventricular volumes were derived. Seven patients (group 1) who had an increase in LV end-diastolic volume with PEEP and 13 patients (group 2) who had the more typical response, a decrease in LV end-diastolic volume with PEEP, were identified. Compared with group 2, group 1 patients had a higher incidence of coronary artery disease (5 of 7 vs 1 of 13, p less than 0.005) and lower cardiac output (3.9 +/- 1.6 vs 9.1 +/- 3.2 liters/min, p less than 0.005), LV ejection fraction (27 +/- 13 vs 51 +/- 21%, p less than 0.05), RV ejection fraction (15 +/- 6 vs 32 +/- 8%, p less than 0.005) and peak filling rate (1.32 +/- 0.43 vs 3.51 +/- 1.70 end-diastolic volumes/s, p less than 0.05). LV and RV volumes increased and peak filling rate decreased with PEEP in group 1, whereas in group 2 LV volume decreased and RV volume and peak filling rate remained unchanged. Using stepwise regression analysis, the change in LV volume with PEEP was related directly to baseline systemic vascular resistance and inversely to baseline blood pressure. Similarly, the change in peak filling rate with PEEP was inversely related to the change in RV end-diastolic volume. Thus, the hemodynamic response to PEEP is heterogeneous and may be related to LV ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of incremental positive end-expiratory pressure on right ventricular hemodynamics and ejection fraction

The effects of incremental positive end-expiratory pressure (PEEP) on right ventricular (RV) function were evaluated in 36 (n = 36) ventilated patients. Positive end-expiratory pressure was increased from 0 (baseline) to 20 cm H2O in 5-cm H2O increments and RV hemodynamics and thermally derived right ventricular ejection fraction (RVEF), right ventricular end-diastolic volume index (RVEDVI), and right ventricular end-systolic volume index (RVESVI) were computed. Right ventricular contractility was determined from the analysis of RV systolic pressure-volume relations. Right ventricular ejection fraction declined from 42 +/- 8% at baseline to 30 +/- 9% at 20 cm H2O PEEP. Right ventricular end-diastolic volume index declined between 0 and 5 cm H2O PEEP (103 +/- 42 to 92 +/- 34 ml.m-2) and then increased to 113 +/- 40 at 20 cm H2O PEEP. Right ventricular end-systolic volume index increased from 60 +/- 31 ml.m-2 at baseline to 79 +/- 34 ml.m-2 at 20 cm H2O PEEP. The slope (E) of the relation of RV peak systolic pressure to RV end-systolic volume index decreased from 0.26 mm Hg.m2.ml-1 between PEEP of 0-15 cm H2O to 0.05 mm Hg.m2.m-1 at PEEP greater than 15 cm H2O. It is concluded that low levels of PEEP have a predominant preload reducing effect on the RV. Above 15 cm H2O PEEP, RV volumes increase and E decreases, consistent with increased RV afterload and a decline in RV contractility.

Effect of positive end-expiratory pressure on right ventricular performance. Importance of baseline right ventricular function

Thirty-six patients with diverse baseline right ventricular function were evaluated during incremental positive end-expiratory pressure (PEEP) application. Right heart pressures, cardiac output, right ventricular ejection fractions, and ventricular volumes were obtained at each PEEP level. Right ventricular peak systolic pressure-end-systolic volume relations were analyzed as an index of contractile function. Patients with severely depressed baseline right ventricular ejection fractions (30 percent or less) had an increase in end-diastolic (270 +/- 74 to 391 +/- 76 ml, 0 to 20 cm water (H2O) PEEP, p less than 0.05) and end-systolic volumes (210 +/- 70 to 321 +/- 70 ml, 0 to 20 cm H2O PEEP, p less than 0.05). These patients also had a decline in estimated right ventricular contractile function at 20 cm H2O PEEP as estimated by the slope of systolic pressure-volume relations (0.12 to 0.04 mm Hg/ml, 0 to 15 and 15 to 20 cm H2O PEEP, respectively, p less than 0.05). Patients with normal (40 percent or more) or moderately depressed (31 to 40 percent) baseline right ventricular ejection fractions had no change in right ventricular volumes or estimated contractile function. Therefore, the effect of PEEP on right ventricular function differs depending on the baseline right ventricular ejection fraction.

Intact systolic left ventricular function in clinical congestive heart failure

Clinical congestive heart failure (CHF) is traditionally associated wtih significant left ventricular (LV) systolic dysfunction. Over a 1-year period, 58 patients with CHF and intact systolic function (LV ejection fraction [EF] 62 +/- 11%) were identified. An objective clinical-radiographic CHF score was used to document the clinical impression. Based on radionuclide evaluation of peak filling rate, 38% of these patients were found to have a significant abnormality in diastolic function as measured by peak filling rate (less than 2.50 end-diastolic volume/s). An additional 24% of the patients had probable diastolic dysfunction with borderline abnormal peak filling rate measurements (2.5 to 3.0 end-diastolic volume/s). The disease states most frequently associated with CHF and intact systolic function were coronary artery disease and systemic hypertension. During a 3-month sampling period 42% of patients with clinical diagnosis of CHF referred to the nuclear cardiology laboratory were found to have intact systolic function; thus, intact systolic function is not uncommon in patients with clinical CHF. Abnormal diastolic function is the most frequently encountered mechanism for the occurrence of CHF. Definition of systolic and diastolic function appears relevant for development of optimal therapeutic strategies for the treatment of patients with CHF.