Mitochondrial uncoupling reduces exercise capacity despite several skeletal muscle metabolic adaptations

The effects of mitochondrial uncoupling on skeletal muscle mitochondrial adaptation and maximal exercise capacity are unknown. In this study, rats were divided into a control group (CTL, n = 8) and a group treated with 2,4-dinitrophenol, a mitochondrial uncoupler, for 28 days (DNP, 30 mg·kg−1·day−1in drinking water, n = 8). The DNP group had a significantly lower body mass ( P < 0.05) and a higher resting oxygen uptake (V̇o2, P < 0.005). The incremental treadmill test showed that maximal running speed and running economy ( P < 0.01) were impaired but that maximal V̇o2(V̇o2max) was higher in the DNP-treated rats ( P < 0.05). In skinned gastrocnemius fibers, basal respiration (V0) was higher ( P < 0.01) in the DNP-treated animals, whereas the acceptor control ratio (ACR, Vmax/V0) was significantly lower ( P < 0.05), indicating a reduction in OXPHOS efficiency. In skeletal muscle, DNP activated the mitochondrial biogenesis pathway, as indicated by changes in the mRNA expression of PGC1-α and -β, NRF-1 and −2, and TFAM, and increased the mRNA expression of cytochrome oxidase 1 ( P < 0.01). The expression of two mitochondrial proteins (prohibitin and Ndufs 3) was higher after DNP treatment. Mitochondrial fission 1 protein (Fis-1) was increased in the DNP group ( P < 0.01), but mitofusin-1 and -2 were unchanged. Histochemical staining for NADH dehydrogenase and succinate dehydrogenase activity in the gastrocnemius muscle revealed an increase in the proportion of oxidative fibers after DNP treatment. Our study shows that mitochondrial uncoupling induces several skeletal muscle adaptations, highlighting the role of mitochondrial coupling as a critical factor for maximal exercise capacities. These results emphasize the importance of investigating the qualitative aspects of mitochondrial function in addition to the amount of mitochondria.

Methylene blue protects liver oxidative capacity after gut ischaemia-reperfusion in the rat

OBJECTIVES

Mesenteric ischaemia/reperfusion (IR) may lead to liver mitochondrial dysfunction and multiple organ failure. We determined whether gut IR induces early impairment of liver mitochondrial oxidative activity and whether methylene blue (MB) might afford protection.

DESIGN

Controlled animal study.

MATERIALS AND METHODS

Rats were randomised into three groups: controls (n = 18), gut IR group (mesenteric ischaemia (60 min)/reperfusion (60 min)) (n = 18) and gut IR + MB group (15 mg kg(-1) MB intra-peritoneally) (n = 16). Study parameters were: serum liver function markers, blood lactate, standard histology and DNA fragmentation (apoptosis) on intestinal and liver tissue, maximal oxidative capacity of liver mitochondria (state 3) and activity of complexes II, III and IV of the respiratory chain measured using a Clark oxygen electrode.

RESULTS

Gut IR increased lactate deshydrogenase (+982%), aspartate and alanine aminotransferases (+43% and +74%, respectively) and lactate levels (+271%). It induced segmental loss of intestinal villi and cryptic apoptosis. It reduced liver state 3 respiration by 30% from 50.1 ± 3 to 35.2 ± 3.5 μM O(2) min(-1) g(-1) (P < 0.01) and the activity of complexes II, III and IV of the mitochondrial respiratory chain. Early impairment of liver mitochondrial respiration was related to blood lactate levels (r(2) = 0.45). MB restored liver mitochondrial function.

CONCLUSIONS

MB protected against gut IR-induced liver mitochondria dysfunction.

Safety of a new transpulmonary echocontrast agent (Albunex) in repeated echocardiographic studies in patients

BACKGROUND AND HYPOTHESIS

Multiple contrast-enhanced echocardiographic studies are to be expected in patients with cardiac ischemic disease, but the sonication process used to produce the echocontrast agent Albunex may result in new epitopes that could cause an immunogenic response.

METHODS

Repeated exposures to intravenous Albunex over a period of time long enough to allow development of an eventual immune reaction were performed in 12 patients while monitoring for lymphocyte transformation, microsphere specific IgE and IgG antibodies, and systemic, pulmonary artery, capillary wedge, and right atrial pressures, as well as cardiac output, left ventricular fractional shortening, and blood gases.

RESULTS

No significant 3H-thymidine incorporation and thus no specific blastic transformation of the patients' lymphocytes were observed either for high or low Albunex concentrations, corresponding to the expected hepatic and plasma concentrations of microspheres. No formation of microsphere-specific IgE and IgG antibodies was observed after the first or second Albunex exposure. Furthermore, no clinically significant hemodynamic or respiratory adverse reactions were observed in any patient.

CONCLUSION

These results suggest that repeated exposures to intravenous Albunex induce no adverse effect on the cellular and humoral immune systems and on left and right heart hemodynamics in patients.

Does circulating BNP normalize after heart transplantation in patients with normal hemodynamic and right and left heart functions?

BACKGROUND

Increased brain natriuretic peptide (BNP) in cardiovascular disease is thought to be a compensatory protective mechanism allowing to delay the occurrence of terminal heart failure. Heart transplantation should normalize the neuroendocrine balance but BNP remains elevated in stable heart-transplant recipients (Htx). Such increase has been related to persistent endothelial and cardiac dysfunctions. The purpose of this study was to determine whether selected Htx, presenting with normal hemodynamic and cardiac systolic and diastolic functions on both side of the heart, show a normalization of their BNP plasma values.

METHODS

Of a cohort of well-being 26 Htx, we selected 12 patients with normal hemodynamics and left and right heart systolic and diastolic functions and compared their circulating BNP, cyclic guanosine monophosphate (cGMP) (the BNP second messenger) and endothelin-1 (ET) values with that of 12 age-, body mass index- and mean arterial pressure-matched controls. Cardiac function determination by echodoppler included cardiac filling pressures assessment using tissue Doppler imaging. Blood samples for biological and hormonal determinations were drawn at rest, within 15 min before echocardiography.

RESULTS

As selected, hemodynamic and left and right heart systolic and diastolic functions were located in the normal range in Htx. Plasma ET value was also similar in Htx and controls (20.7 +/- 0.9 vs. 19.6 +/- 0.9 fmol/mL). However, circulating BNP, like cGMP, was still significantly increased after heart transplantation, when compared with controls (33.8 +/- 8.5 vs. 4.0 +/- 0.9 pg/mL, p = 0.002 and 8.2 +/- 1.1 vs. 4.4 +/- 0.3 nmol/L, p = 0.003) for BNP and cGMP, respectively, in Htx and controls. Interestingly, the sole correlation observed was between BNP and cGMP (r = 0.85, p < 0.0001) after heart transplantation.

CONCLUSIONS

After heart transplantation, BNP remained increased despite the normalization of hemodynamic and cardiac systolic and diastolic functions. This suggests that such endocrine heart stimulation should not be viewed only as a hemodynamic marker in Htx. Further studies will be useful to investigate the role of pro-inflammatory cytokines and whether elevated BNP still possesses antifibrotic properties, further supporting the interest of enhancing its activity after heart transplantation.

Relationship Between Very High Physical Activity Energy Expenditure, Heart Rate Variability and Self-Estimate of Health Status in Middle-Aged Individuals

In middle-aged persons, moderate physical activity energy expenditure (PAEE) has been shown to be associated with increased vagal-related heart rate variability (HRV) indexes and better health status. The purpose of this study was to determine whether a very high PAEE has greater effect on vagal-related HRV indexes and self-estimates of well-being in middle-aged subjects having distinct long-term physical activity profiles. Forty-four subjects were divided into three groups on the basis of the sport score of the Modified Baecke Questionnaire for Older Adults: sedentary (SED, n = 15), moderately-trained (MT, n = 16), and highly-trained subjects (HT, n = 13). PAEE was estimated by triaxial accelerometry during one week. Time and frequency domain HRV indexes were determined during quiet periods in the morning on 5-min R-R interval segments under controlled breathing. Quality of life was evaluated using the SF-36 health survey questionnaire. PAEE was significantly different for each group (374.5 +/- 13.8, 616.8 +/- 22.4, and 1086.6 +/- 43.2 kcal . day (-1) for SED, MT, and HT, respectively, p < 0.001). MT presented significantly higher vagal-related HRV indexes than SED and HT (p < 0.05). None of the HRV indexes was significantly greater in HT than in SED. MT and HT had similar health status scores, which were significantly higher than for SED. These results indicate that in middle-aged subjects, habitual moderate PAEE is associated with greater vagal tone and self-estimates of well-being compared to low PAEE. In contrast, very high PAEE is associated with similar vagal-related indexes as low PAEE, despite better overall health status.

Chronic L-Arginine Supplementation Enhances Endurance Exercise Tolerance in Heart Failure Patients

The purpose of the study was to determine the potential beneficial effect of six weeks oral L-arginine supplementation (LAS) on endurance exercise, an important determinant of daily-life activity in patients with chronic stable heart failure (CHF). After an initial incremental maximal exercise test, CHF patients performed an identical thirty-minute interval endurance exercise test before and after six weeks with (L-arginine group; ARG) or without LAS (control group; CTL). Hemodynamic, respiratory, and metabolic parameters were determined at rest, during exercise, and during recovery. Mean heart rate decreased throughout exercise and recovery after LAS (- 8.2 +/- 1.4 b x min(-1); p = 0.003 and - 6.7 +/- 1.6 b x min(-1); p < 0.001, respectively), systemic blood pressure and respiratory parameters remaining unchanged. Resting L-argininaemia increased from 102 +/- 11 to 181 +/- 37 micromol x l(-1) (p < 0.004) and exercise-induced peak increase in plasma lactate was blunted after LAS (4.13 +/- 0.75 vs. 3.13 +/- 0.39 mmol x l(-1); p = 0.02). No significant change was observed in the control group. In heart failure patients, six weeks oral LAS enhances endurance exercise tolerance, reducing both heart rate and circulating lactates. This suggests that chronic LAS might be useful as a therapeutic adjuvant in order to improve the patient's physical fitness.

Acute myocardial ischaemia induces specific alterations of ventricular mitochondrial function in experimental pigs

AIMS

As cardiac metabolic flexibility is crucial, this study examined whether acute ischaemia can induce specific qualitative alterations of the mitochondrial metabolic pathways as well as energy transfer systems.

METHODS

Left descending coronary artery ligation was performed after sternotomy in eight pigs and the heart was excised after 45 min of ischaemia. Maximal O2 uptake (V(max), micromol O2 min(-1) g(-1) dry weight) of saponin-skinned myofibres were measured from ischaemic and non-ischaemic area of ventricular myocardium.

RESULTS

V(max) decreased by approximately 20% in ischaemic myocardium with both glutamate-malate (18.1 +/- 1.3 vs. 22.1 +/- 1.7 in control, P < 0.05) and pyruvate substrates (19.3 +/- 1.0 vs. 23.3 +/- 2.0 in control, P < 0.05) whereas no difference was observed with palmitoyl carnitine (15.6 +/- 1.8 vs. 16.6 +/- 0.9 in control). The K(m) of mitochondrial respiration for ADP decreased in ischaemic heart by 24% (679 +/- 79 vs. 899 +/- 84 microm of ADP in control, P < 0.05). Moreover, the mitochondrial creatine kinase efficacy (K(m) without creatine/K(m) with creatine), representative of the coupling of oxidative phosphorylation process with the mitochondrial creatine kinase, was reduced in ischaemic heart (11.6 +/- 2.5 in ischaemic vs. 18.0 +/- 2.2 in control, P < 0.05).

CONCLUSIONS

These findings argue for specific mitochondrial impairments at the level of pyruvate oxidation and creatine kinase channelling system after an acute period of in vivo ischaemia, whereas the lipid mitochondrial oxidation pathway seems to be preserved. Such a loss of metabolic flexibility following acute ischaemia could become an early feature of metabolic dysregulation of the heart.

Effects of increased training load on vagal-related indexes of heart rate variability: a novel sleep approach

There is little doubt that moderate training improves cardiac vagal activity and thus has a cardioprotective effect against lethal arrhythmias. Our purpose was to learn whether a higher training load would further increase this beneficial effect. Cardiac autonomic control was inferred from heart rate variability (HRV) and analyzed in three groups of young subjects (24.5 ± 3.0 yr) with different training states in a period free of stressful stimuli or overload. HRV was analyzed in 5-min segments during slow-wave sleep (SWS, a parasympathetic state that offers high electrocardiographic stationarity) and compared with data collected during quiet waking periods in the morning. Sleep parameters, fatigue, and stress levels checked by questionnaire were identical for all three groups with no signs of overtraining in the highly trained (HT) participants. During SWS, a significant ( P < 0.05) increase in absolute and normalized vagal-related HRV indexes was observed in moderately trained (MT) individuals compared with sedentary (Sed) subjects; this increase did not persist in HT athletes. During waking periods, most of the absolute HRV indexes indistinctly increased in MT individuals compared with controls ( P < 0.05) but did not increase in HT athletes. Normalized spectral HRV indexes did not change significantly among the three groups. Heart rate was similar for MT and Sed subjects but was significantly ( P < 0.05) lower in HT athletes under both recording conditions. These results indicate that SWS discriminates the state of sympathovagal balance better than waking periods. A moderate training load is sufficient to increase vagal-related HRV indexes. However, in HT individuals, despite lower heart rate, vagal-related HRV indexes return to Sed values even in the absence of competition, fatigue, or overload.

Abnormal heart rate variability in a subject with second degree atrioventricular blocks during sleep

OBJECTIVE

We compare the profiles of heart rate variability (HRV) during sleep stages in 9 healthy controls and one subject with second degree atrioventricular blocks (AVB), investigating the role of sympathovagal balance in such pathology.

METHOD

Sleep and cardiac records were taken for one night in 9 male subjects from 21:00 to 07:00 h and for two nights in a male subject with AVB. Time and frequency domain indexes of HRV were calculated over 5 min-periods.

RESULTS

In one subject without any daytime heart disease, 253 and 318 AVB of type 2 (Mobitz 2) were observed during the two experimental nights, predominantly during rapid eye movement (REM) sleep and the surrounding sleep stage 2 in the second half of the night. In the 9 control subjects, absolute HRV indexes and low frequency (LF)/(LF+high frequency, HF) (where LF and HF are low frequency and high frequency power) were low during slow wave sleep, and significantly increased during REM sleep and the preceding sleep stage 2. In the subject with AVB, these HRV indexes were abnormally low during all sleep stages, with a predominant increase in parasympathetic activity as inferred from low LF/(LF+HF). During wake, however, LF/(LF+HF) normally increased, and the tachycardia observed with the arousal that terminates SWS was preserved in the subject with AVB.

CONCLUSION

These results suggest that in the subject with second degree atrioventricular blocks, sleep processes, particularly during REM sleep, create a specific neurological background that prevents an increase in sympathetic tone and triggers cardiac pauses.

Mechanisms of renal hyporesponsiveness to ANP in heart failure

The atrial natriuretic peptide (ANP) plays an important role in chronic heart failure (CHF), delaying the progression of the disease. However, despite high ANP levels, natriuresis falls when CHF progresses from a compensated to a decompensated state, suggesting emergence of renal resistance to ANP. Several mechanisms have been proposed to explain renal hyporesponsiveness, including decreased renal ANP availability, down-regulation of natriuretic peptide receptors and altered ANP intracellular transduction signal. It has been demonstrated that the activity of neutral endopeptidase (NEP) is increased in CHF, and that its inhibition enhances renal cGMP production and renal sodium excretion. In vitro as well as in vivo studies have provided strong evidence of an increased degradation of intracellular cGMP by phosphodiesterase in CHF. In experimental models, ANP-dependent natriuresis is improved by phosphodiesterase inhibitors, which may arise as new therapeutic agents in CHF. Sodium-retaining systems likely contribute to renal hyporesponsiveness to ANP through different mechanisms. Among these systems, the renin-angiotensin-aldosterone system has received particular attention, as angiotensin II and ANP have renal actions at the same sites and inhibition of angiotensin-converting enzyme and angiotensin-receptor blockade improve ANP hyporesponsiveness. Less is known about the interactions between the sympathetic nervous system, endothelin or vasopressin and ANP, which may also blunt ANP-induced natriuresis. To summarize, renal hyporesponsiveness to ANP is probably multifactorial. New treatments designed to restore renal ANP efficiency should limit sodium retention in CHF patients and thus delay the progression to overt heart failure.

L-arginine reduces exercise-induced increase in plasma lactate and ammonia

To investigate the effect of L-arginine supplementation (L-ARG) on physiological and metabolic changes during exercise, we determined in a double-blind study the cardiorespiratory (heart rate, oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) and the metabolic (lactate and ammonia) responses to maximal exercise after either an intravenous L-ARG hydrochloride salt or placebo load in 8 healthy subjects. Exercise-induced increases in heart rate, VO(2) and VCO(2) were not significantly different after L-ARG or placebo. By contrast, peak plasma ammonia and lactate were significantly decreased after L-ARG load (60.6 +/- 8.2 vs. 73.1 +/- 9.1 micro mol x l(-1), p < 0.01 and 7.1 +/- 0.7 vs. 8.2 +/- 1.1 mmol x l(-1), p < 0.01, for ammonia and lactate, respectively). Plasma L-citrulline increased significantly during exercise only after L-ARG load, despite a concomitant decrease in plasma L-ARG. Furthermore, a significant inverse relationship was observed between changes in lactate and L-citrulline concentrations after L-ARG load (r = -0.84, p = 0.009). These results demonstrate that intravenous L-ARG reduces significantly exercise-induced increase in plasma lactate and ammonia. Taken together, the specific L-citrulline increase and the inverse relationship observed between L-citrulline and plasma lactate after L-ARG might support that L-ARG supplementation enhances the L-arginine-nitric oxide (NO) pathway during exercise.

Time-courses in renin and blood pressure during sleep in humans

We previously described a strong concordance between nocturnal oscillations in plasma renin activity (PRA) and the rapid eye movement (REM) and non-REM (NREM) sleep cycles, but the mechanisms inducing PRA oscillations remain to be identified. This study was designed to examine whether they are linked to sleep stage-related changes in arterial blood pressure (ABP). Analysis of sleep electroencephalographic (EEG) activity in the delta frequency band, intra-arterial pressure, and PRA measured every 10 min was performed in eight healthy subjects. Simultaneously, the ratio of low frequency power to low frequency power + high frequency power [LF/(LF + HF)] was calculated using spectral analysis of R--R intervals. The cascade of physiological events that led to increased renin release during NREM sleep could be characterized. First, the LF/(LF + HF) ratio significantly (P < 10(-4) decreased, indicating a reduction in sympathetic tone, concomitantly to a significant (P < 10(- 3) decrease in mean arterial pressure (MAP). Delta wave activity increased (P < 10(-4) 10-20 min later and was associated with a lag of 0-10 min with a significant rise in PRA (P < 10(-4) . Rapid eye movement sleep was characterized by a significant increase (P < 10(-4) in the LF/(LF + HF) ratio and a decrease (P < 10(-4) in delta wave activity and PRA, whereas MAP levels were highly variable. Overnight cross-correlation analysis revealed that MAP was inversely correlated with delta wave activity and with PRA (P < 0.01 in all subjects but one). These results suggest that pressure-dependent mechanisms elicit the nocturnal PRA oscillations rather than common central processes controlling both the generation of slow waves and the release of renin from the kidney.

Inverse coupling between ultradian oscillations in delta wave activity and heart rate variability during sleep

OBJECTIVE

We investigate the relationship between changes in heart rate variability and electroencephalographic (EEG) activity during sleep.

METHOD

Nine male subjects with regular non-rapid-eye movement-rapid-eye movement (NREM-REM) sleep cycles were included in the study. They underwent EEG and cardiac recordings during one experimental night. Heart rate variability was determined over 5-min periods by the ratio of low frequency to low frequency plus high frequency power [LF/(LF+HF)] calculated using spectral analysis of R-R intervals. EEG spectra were analyzed using a fast Fourier transform algorithm.

RESULTS

We found an ultradian 80-120 min rhythm in the LF/(LF+HF) ratio, with high levels during rapid eye movement (REM) sleep and low levels during slow wave sleep (SWS). During sleep stage 2 there was a progressive decrease in the transition from REM sleep to SWS, and an abrupt increase from SWS to REM sleep. These oscillations were significantly coupled in a 'mirror-image' to the overnight oscillations in delta wave activity, which reflect sleep deepening and lightening. Cardiac changes preceded EEG changes by about 5 min.

CONCLUSIONS

These findings demonstrate the existence of an inverse coupling between oscillations in delta wave activity and heart rate variability. They indicate a non-uniformity in sleep stage 2 that underlies ultradian sleep regulation.

Sleep deprivation blunts the night time increase in aldosterone release in humans

The aim of this study was to determine the effect of sleep deprivation on the 24-h profile of aldosterone and its consequences on renal function. Aldosterone and its main hormonal regulatory factors, ACTH (evaluated by cortisol measurement) and the renin-angiotensin system [RAS, evaluated by plasma renin activity (PRA) measurement] were determined every 10 min for 24 h in eight healthy subjects in the supine position, once with nocturnal sleep and once during total 24-h sleep deprivation. Plasma Na(+) and K(+) were measured every 10 min in four of these subjects. In an additional group of 13 subjects under enteral nutrition, diuresis, natriuresis and kaliuresis were measured once during the sleep period (23.00--07.00 h) and once during a 23.00--07.00 hours sleep deprivation period. During sleep deprivation, aldosterone displayed lower plasma levels and pulse amplitude in the 23.00--07.00-hour period than during sleep. Similarly, PRA showed reduced levels and lower pulse frequency and amplitude. Plasma cortisol levels were slightly enhanced during sleep deprivation. Overnight profiles of plasma K(+) and Na(+) were not affected. Diuresis and kaliuresis were not influenced by sleep deprivation. In contrast, natriuresis significantly increased during sleep deprivation. This study demonstrates that sleep deprivation modifies the 24-h aldosterone profile by preventing the nocturnal increase in aldosterone release and leads to altered overnight hydromineral balance.

Effect of sleep deprivation on overall 24 h growth-hormone secretion

After sleep deprivation, the blunting of the normal sleep-related growth-hormone (GH) pulse is compensated during the day. Consequently, the amount of GH secreted during a 24 h period is similar whether or not a person has slept during the night. These results argue against the belief that sleep disorders in children can inhibit growth through a daily GH deficit.

Exercise-induced increase in circulating adrenomedullin is related to mean blood pressure in heart transplant recipients

Adrenomedullin (ADM) is a newly discovered potent vasorelaxing and natriuretic peptide that recently has been shown to be increased after heart transplantation. To investigate the hemodynamic factors modulating its release and the eventual role of ADM in blood pressure regulation after heart transplantation, seven matched heart-transplant recipients (Htx) and seven normal subjects performed a maximal bicycle exercise test while monitoring for heart rate, blood pressure, and circulating ADM. Baseline heart rate and systemic blood pressure were higher in Htx; left ventricular mass index and ADM tended to be higher after heart transplantation and correlated positively in Htx (r = 0.79, P = 0.03). As expected, exercise-induced increase in heart rate was lower in Htx than in controls (60 +/- 11 % vs. 121 +/- 14 %, respectively) and blood pressure increase was similar in both groups. Maximal exercise increased significantly plasma ADM in both groups (from 25.3 +/- 3.1 to 30.7 +/- 3.5 pmol/L, P < 0.05 and from 15.2 +/- 1.4 to 29.1 +/- 4.4 pmol/L, P = 0.02 in Htx and controls, respectively), the hypotensive peptide level remaining elevated until the 30th min of recovery. A significant inverse relationship was observed between peak mean blood pressure and circulating ADM in Htx (r = -0.86, P < 0.02). Besides showing that circulating ADM is increased after heart transplantation, the present study demonstrates a positive relationship between baseline ADM and left ventricular mass index. Furthermore, maximal exercise-induced increase in ADM is inversely related to mean blood pressure in Htx, suggesting that ADM might participate in blood pressure regulation during exercise after heart transplantation.

Lack of acute cyclosporine nephrotoxicity in late heart-transplant recipients

BACKGROUND

Cyclosporine induces daily renal hypoperfusion in subjects with normal atrial natriuretic peptide (ANP) levels, but its acute effects in heart transplant patients with increased ANP remain to be determined.

METHODS

Cyclosporinemia and creatinine clearance were monitored during 7 hours following cyclosporine administration in 6 heart transplant patients.

RESULTS

CONCLUSIONS

No acute cyclosporine-induced decrease in creatinine clearance was observed after heart transplantation. These data suggest that maintenance cyclosporine dose may be less nephrotoxic than suspected and that increased ANP might protect the renal function late after heart transplantation.

VO(2) kinetics reveal a central limitation at the onset of subthreshold exercise in heart transplant recipients

Because the cardiocirculatory response of heart transplant recipients (HTR) to exercise is delayed, we hypothesized that their O(2) uptake (VO(2)) kinetics at the onset of subthreshold exercise are slowed because of an impaired early "cardiodynamic" phase 1, rather than an abnormal subsequent "metabolic" phase 2. Thus we compared the VO(2) kinetics in 10 HTR submitted to six identical 10-min square-wave exercises set at 75% (36 +/- 5 W) of the load at their ventilatory threshold (VT) to those of 10 controls (C) similarly exercising at the same absolute (40 W; C40W group) and relative load (67 +/- 14 W; C67W group). Time-averaged heart rate, breath-by-breath VO(2), and O(2) pulse (O(2)p) data yielded monoexponential time constants of the VO(2) (s) and O(2)p increase. Separating phase 1 and 2 data permitted assessment of the phase 1 duration and phase 2 VO(2) time constant (). The VO(2) time constant was higher in HTR (38.4 +/- 7.5) than in C40W (22.9 +/- 9.6; P < or = 0. 002) or C67W (30.8 +/- 8.2; P < or = 0.05), as was the O(2)p time constant, resulting from a lower phase 1 VO(2) increase (287 +/- 59 vs. 349 +/- 66 ml/min; P < or = 0.05), O(2)p increase (2.8 +/- 0.6 vs. 3.6 +/- 1.0 ml/beat; P < or = 0.0001), and a longer phase 1 duration (36.7 +/- 12.3 vs. 26.8 +/- 6.0 s; P < or = 0.05), whereas the was similar in HTR and C (31.4 +/- 9.6 vs. 29.9 +/- 5.6 s; P = 0.85). Thus the HTR have slower subthreshold VO(2) kinetics due to an abnormal phase 1, suggesting that the heart is unable to increase its output abruptly when exercise begins. We expected a faster in HTR because of their prolonged phase 1 duration. Because this was not the case, their muscular metabolism may also be impaired at the onset of subthreshold exercise.

Neuroendocrine processes underlying ultradian sleep regulation in man

Sleep is not a uniform state but is characterized by the cyclic alternation between rapid eye movement (REM) and non-REM sleep with a periodicity of 90-110 min. This cycle length corresponds to one of the oscillations in electroencephalographic (EEG) activity in the delta frequency band (0.5-3.5 Hz), which reflect the depth of sleep. To demonstrate the intimate link between EEG and neuroendocrine rhythmic activities in man, we adopted a procedure permitting simultaneous analysis of sleep EEG activity in the delta band and of two activating systems: the adrenocorticotropic system and the autonomic nervous system. Adrenocorticotropic activity was evaluated by calculating the cortisol secretory rate in blood samples taken at 10-min intervals. Autonomic activity was estimated by two measures of heart rate variability: 1) by the ratio of low-frequency (LF) to high-frequency (HF) power from spectral analysis of R-R intervals; and 2) by the interbeat autocorrelation coefficient of R-R intervals (rRR intervals between two successive cardiac beats). The results revealed that oscillations in delta wave activity, adrenocorticotropic activity, and autonomic activity are linked in a well-defined manner. Delta wave activity developed when cortisol secretory rates had returned to low levels and sympathetic tone was low or decreasing, as reflected by a low LF/HF ratio and by low levels in rRR. Conversely, the decrease in delta wave activity occurred together with an increase in the LF/HF ratio and in rRR. REM sleep was associated with a decrease in cortisol secretory rates preceding REM sleep onset, whereas the LF/HF ratio and rRR remained high. These results demonstrate a close coupling of adrenocorticotropic, autonomic, and EEG ultradian rhythms during sleep in man. They suggest that low neuroendocrine activity is a prerequisite for the increase in slow wave activity.

Enhanced natriuretic response to neutral endopeptidase inhibition in heart-transplant recipients

Heart-transplant recipients (Htx) generally present with body fluid and sodium handling abnormalities and hypertension. To investigate whether neutral endopeptidase inhibition (NEP-I) increases endogenous atrial natriuretic peptide (ANP) and enhances natriuresis and diuresis after heart transplantation, ecadotril was given orally to 8 control subjects and 8 matched Htx, and levels of volume-regulating hormones and renal water, electrolyte, and cyclic guanosine monophosphate (cGMP) excretions were monitored for 210 minutes. Baseline plasma ANP, brain natriuretic peptide (BNP), and cGMP were elevated in Htx, but renin and aldosterone, like urinary parameters, did not differ between groups. NEP-I increased plasma ANP (Htx, 20.6+/-2.3 to 33.2+/-5.9 pmol/L, P<0.01; controls, 7.7+/-1. 2 to 10.6+/-2.6 pmol/L) and cGMP, but not BNP. Renin decreased similarly in both groups, whereas aldosterone decreased significantly only in Htx. Enhanced urinary sodium (1650+/-370% versus 450+/-150%, P=0.01), cGMP, and water excretions were observed in Htx and urinary cGMP positively correlated with natriuresis in 6 of the Htx subjects. Consistent with a normal circadian rhythm of blood pressure, without excluding a possible effect of NEP-I, mean systemic blood pressure increased similarly in both groups at the end of the study (6.9+/-2.0% versus 7.4+/-2.8% in controls and Htx). Thus, systemic hypertension, mild renal impairment, and raised plasma ANP levels are possible contributory factors in the enhanced natriuresis and diuresis with NEP-I in Htx. These results support a physiological role for the cardiac hormone after heart transplantation and suggest that long-term studies may be useful to determine the potential of NEP-I in the treatment of sodium retention and water retention after heart transplantation.

Circulating adrenomedullin is increased after heart transplantation

OBJECTIVE

Adrenomedullin (ADM), secreted by the failing human heart, is a newly discovered potent endogenous vasorelaxing and natriuretic peptide that may play a role in cardiorenal regulation. No data are available on ADM in heart-transplant recipients (Htx) and the aim of this study was to determine the short- and long-term responses of ADM after heart transplantation.

METHODS

Circulating ADM and its relationship with parameters of cardiovascular hemodynamics, humoral factors and renal function were determined in normal subjects and Htx early (1, 2, 4, 8, 15 and 30 days) and late (32 +/- 16 months) after transplantation. Additionally, ADM was obtained in matched hypertensive and renal-transplant patients (n = 9 in each group).

RESULTS

Plasma ADM, elevated in heart failure patients, further increased transiently at day 1 after transplantation (from 37.9 +/- 15.9 to 125.8 +/- 15.3 pmol/l, P < 0.01) and, although decreasing thereafter, remained elevated until the 30th day after transplantation (52.1 +/- 25.2 pmol/l). Late after transplantation. ADM concentrations were still increased compared to normal values (31.3 +/- 5.3 vs. 19.4 +/- 2.7 pmol/l, P < 0.001). ADM positively correlated with endothelin, atrial natriuretic peptide (ANP) and cyclosporine. ADM was also correlated with increased diastolic (r = 0.68, P < 0.04) and systolic (r = 0.66, P < 0.05) blood pressure in late Htx. No relationship was observed between ADM and left ventricular mass index, aldosterone and creatinine. ADM elevation was similar in hypertensive, renal-transplant patients and in Htx.

CONCLUSIONS

Circulating ADM is increased after heart transplantation, in relation to hypertension, endothelin, cyclosporine and ANP. In view of ADM's biological properties, these results might suggest a compensatory role for ADM against further development of vasoconstriction and fluid retention states after heart transplantation.

Lung membrane diffusing capacity, heart failure, and heart transplantation

The pulmonary diffusing capacity for carbon monoxide (DLCO) is reduced in chronic heart failure and remains decreased after heart transplantation. This decrease in DLCO may depend on a permanent alteration after transplantation of one or the other of its components: diffusion of the alveolar capillary membrane or the pulmonary capillary blood volume (Vc). Therefore, we measured DLCO, the membrane conductance, and Vc before and after heart transplantation. At the time of hemodynamic measurements, the Roughton and Forster method of measuring DLCO at varying alveolar oxygen concentrations was used to determine the membrane conductance, Vc, DLCO/alveolar volume (VA), the membrane conductance/VA and thetaVc/VA (theta = carbon monoxide conductance of blood, VA = alveolar volume) in 21 patients with class III to IV heart failure before and after transplantation, and in 21 healthy controls. Transplantation normalized pulmonary capillary pressure and increased cardiac index. DLCO was decreased before transplantation (7.11 vs 10.0 mmol/min/kPa in controls), but DLCO/VA was normal (1.67+/-0.44 vs 1.71+/-0.26 mmol/min/kPa/L in controls). DLCO/VA remained unchanged after transplantation, because the decrease in Vc (82+/-30 vs 65+/-18 ml before and after transplantation) and thetaVc/VA was not compensated by the changes in membrane conductance (11+/-4 vs 12+/-5 mmol/min/kPa before and after transplantation, respectively) and membrane conductance/VA. We conclude that the decrease in DLCO in patients with chronic heart failure is due to a restrictive ventilatory pattern because their DLCO/VA remains normal; the decrease in the membrane conductance is compensated by the increase in Vc. After transplantation, the decrease in Vc due to normalization of pulmonary hemodynamics is not completely compensated for by an increase in membrane conductance. Because the membrane conductances, measured before and after transplantation, are negatively correlated with duration of heart failure, its abnormal pulmonary hemodynamics may have irreversibly altered the alveolar capillary membrane.

Aldosterone release during the sleep-wake cycle in humans

The aim of this study was to assess the relative influence on the 24-h aldosterone profile of the adrenocorticotropic system, primarily modulated by a circadian rhythmicity, and the renin-angiotensin system, which is influenced by sleep. Cortisol, plasma renin activity (PRA), and aldosterone were measured for 24 h in healthy subjects under basal conditions, once with nocturnal sleep and once with a night of sleep deprivation followed by 8 h of daytime sleep. The sleep period displayed high mean aldosterone levels, pulse amplitude, and frequency that were reduced during waking periods. During sleep, aldosterone pulses were mainly related to PRA oscillations, whereas they were mainly associated with cortisol pulses during waking periods. Cross-correlation analysis between sleep electroencephalographic activity in the delta band and aldosterone levels yielded significant results, aldosterone following delta waves by approximately 30 min. This study demonstrates that the 24-h aldosterone profile is strongly influenced by sleep processes. A dual influence, by the renin-angiotensin system during sleep and by the adrenocorticotropic system during wakefulness, is exerted on aldosterone pulses throughout the 24-h period.

Enhanced brain natriuretic peptide response to peak exercise in heart transplant recipients

We investigated the atrial (ANP) and brain natriuretic peptides (BNP), catecholamines, heart rate, and blood pressure responses to graded upright maximal cycling exercise of eight matched healthy subjects and cardiac-denervated heart transplant recipients (HTR). Baseline heart rate and diastolic blood pressure, together with ANP (15.2 +/- 3.7 vs. 4.4 +/- 0.8 pmol/l; P < 0.01) and BNP (14.3 +/- 2. 6 vs. 7.4 +/- 0.6 pmol/l; P < 0.01), were elevated in HTR, but catecholamine levels were similar in both groups. Peak exercise O2 uptake and heart rate were lower in HTR. Exercise-induced maximal ANP increase was similar in both groups (167 +/- 34 vs. 216 +/- 47%). Enhanced BNP increase was significant only in HTR (37 +/- 8 vs. 16 +/- 8%; P < 0.05). Similar norepinephrine but lower peak epinephrine levels were observed in HTR. ANP and heart rate changes from rest to 75% peak exercise were negatively correlated (r = -0.76, P < 0.05), and BNP increase was correlated with left ventricular mass index (r = 0.83, P < 0.01) after heart transplantation. Although ANP increase was not exaggerated, these data support the idea that the chronotropic limitation secondary to sinus node denervation might stimulate ANP release during early exercise in HTR. Furthermore, the BNP response to maximal exercise, which is related to the left ventricular mass index of HTR, is enhanced after heart transplantation.

Normal short-term renal response to acute volume expansion in heart transplant recipients: a role for atrial natriuretic peptide?

BACKGROUND

The breakdown of blood pressure and body fluid homeostasis observed in heart transplant (Htx) recipients may partly be due, as in heart failure, to a blunted renal response to elevated atrial natriuretic peptide (ANP).

METHOD

This possibility was addressed through determination of the relationship between ANP, the urinary cyclic guanosine monophosphate (cGMP), a biologic marker of ANP renal activity, and the early renal responses to 10 mL/kg isotonic saline infusion over 30 minutes in 8 control subjects and 8 matched Htx recipients.

RESULTS

Urine flow, natriuresis, and urinary cGMP excretion increased similarly in both groups, resulting in elimination of, respectively, 1/2 and 2/3 of the sodium and the water load during the experiment that lasted 4 hours and 30 minutes. Plasma renin and aldosterone decreases were similar in both groups. Elevated ANP further increased in Htx after saline infusion (from 19.5 +/- 3.7 to 33.8 +/- 5.6 pmol/L, P < .001). Plasma cGMP paralleled ANP in both groups (r = 0.81; P < .001). Significant correlations were observed between plasma ANP and urinary cGMP excretion (r = 0.48, P < .025 and r = 0.43, P < .05 in Htx recipients and control subjects) and between plasma ANP and urinary sodium excretion (r = 0.64, P < .001 in Htx recipients).

CONCLUSION

In spite of a relative renal hyporesponsiveness to the cardiac hormone, with higher plasma ANP being not associated with increased renal excretions in Htx recipients, ANP is likely to participate in the appropriate short-term renal response to acute volume expansion in Htx recipients.

Erythrocytes participate significantly in blood transport of amino acids during the post absorptive state in normal humans

To investigate the participation of erythrocytes in the blood transport of amino acids during the course of intestinal absorption in humans, erythrocyte and plasma amino-acid concentrations were determined following ingestion of an oral load of amino acids. In addition to baseline plasma and erythrocyte amino acid concentrations in 18 subjects, plasma and erythrocyte amino acids kinetics during the 125 min following an oral amino acid load were further determined in 9 of the 18 subjects. The results showed that human erythrocytes contained most amino acids at similar or higher concentrations than plasma. Furthermore, the correlations observed between plasma and erythrocyte contents clearly indicated that erythrocytes were involved in the transport of amino acids by the blood. For some amino acids erythrocyte transport sometimes exceeded that of plasma. Significant correlation coefficients showed that strong plasma-erythrocyte relationships existed for alanine, valine, methionine, isoleucine, leucine, phenylalanine, and ornithine. In conclusion, our data supported the hypothesis that both blood compartments, plasma and erythrocytes, are involved significantly in the blood transport of amino acids in humans during the postabsorptive state.

Dynamic heart rate variability: a tool for exploring sympathovagal balance continuously during sleep in men

We have recently demonstrated that the overnight profiles of cardiac interbeat autocorrelation coefficient of R-R intervals (rRR) calculated at 1-min intervals are related to the changes in sleep electroencephalographic (EEG) mean frequency, which reflect depth of sleep. Other quantitative measures of the Poincaré plots, i.e., the standard deviation of normal R-R intervals (SDNN) and the root mean square difference among successive R-R normal intervals (RMSSD), are commonly used to evaluate heart rate variability. The present study was designed to compare the nocturnal profiles of rRR, SDNN, and RMSSD with the R-R spectral power components: high-frequency (HF) power, reflecting parasympathetic activity; low-frequency (LF) power, reflecting a predominance of sympathetic activity with a parasympathetic component; and the LF-to-HF ratio (LF/HF), regarded as an index of sympathovagal balance. rRR, SDNN, RMSSD, and the spectral power components were calculated every 5 min during sleep in 15 healthy subjects. The overnight profiles of rRR and LF/HF showed coordinate variations with highly significant correlation coefficients (P < 0.001 in all subjects). SDNN correlated with LF power (P < 0.001), and RMSSD correlated with HF power (P < 0.001). The overnight profiles of rRR and EEG mean frequency were found to be closely related with highly cross-correlated coefficients (P < 0. 001). SDNN and EEG mean frequency were also highly cross correlated (P < 0.001 in all subjects but 1). No systematic relationship was found between RMSSD and EEG mean frequency. In conclusion, rRR appears to be a new tool for evaluating the dynamic beat-to-beat interval behavior and the sympathovagal balance continuously during sleep. This nonlinear method may provide new insight into autonomic disorders.

Effect of the shift of the sleep-wake cycle on three robust endocrine markers of the circadian clock

To determine the effect of a phase shift in sleep on the circadian clock, thyroid-stimulating hormone (TSH), cortisol, and melatonin, three robust markers of the circadian clock, were analyzed using a 10-min blood sampling procedure. In an initial experiment eight subjects were studied during two experimental sessions: once under baseline conditions with normal nighttime sleep from 2300 to 0700 (baseline) and once after a night of sleep deprivation followed by daytime sleep from 0700 to 1500 (day 1). In a second experiment, carried out on seven subjects, the 24-h hormone profiles of the first day (day 1) were compared with those of the second day (day 2) of the sleep shift. During the night of sleep deprivation (day 1) the TSH surge was higher than during baseline conditions, whereas melatonin and cortisol rhythms remained unaffected. On day 2 the amplitude of the nocturnal TSH surge was reduced in comparison to day 1, whereas the amplitudes of melatonin and cortisol rhythms were unchanged. There was a clear phase shift in the three endocrine rhythms. Triiodothyronine levels were slightly higher in the morning after the first night of sleep deprivation. These results demonstrate that 2 consecutive days of sleep shift are sufficient to affect the timing of the commonly accepted circadian markers, suggesting the existence of a rapid resetting effect on the circadian clock. TSH reacts in a distinctive manner to the sleep-wake cycle manipulation by modulating the amplitude of the nocturnal surge. This amplitude modulation is probably an integral part of the phase-shifting mechanisms controlled by the circadian clock.

Pulsatile cortisol secretion and EEG delta waves are controlled by two independent but synchronized generators

We have previously described a temporal relationship between plasma cortisol pulses and slow-wave sleep and, more recently, an inverse significant cross-correlation between cortisol secretory rates and delta wave activity of the sleep electroencephalogram (EEG). The aim of this study was to observe ACTH, cortisol, and sleep delta wave activity variations throughout 24 h to get a better insight into their initiating mechanisms. Two groups of 10 subjects participated in a 24-h study, one group with a night sleep (2300-0700) and the other with a day sleep (0700-1500). Cortisol secretory rates were calculated by a deconvolution procedure from plasma levels measured at 10-min intervals. Delta wave activity was computed during sleep by spectral analysis of the sleep EEG. When delta waves and cortisol were present at the same time at the end of the night sleep as well as during the daytime sleep, they were negatively correlated, cortisol changes preceding variations in delta wave activity by approximately 10 min. Increases in delta wave activity occurred in the absence of cortisol pulses, as observed at the beginning of the night. Cortisol pulses occurred without any concomitant variations of sleep delta wave activity, as observed during wakefulness and intrasleep awakenings. In no case did delta wave activity increase together with an increase in cortisol secretory rates. In conclusion, cortisol secretion and delta wave activity have independent generators. They can oscillate independently from each other, but when they are present at the same time, they are oscillating in phase opposition.

Oscillations in sympatho-vagal balance oppose variations in delta-wave activity and the associated renin release

To determine the potential role of the sympathetic nervous system in the generation of the oscillations in PRA over the 24-h period, we used the autocorrelation coefficient of RR interval (rRR), a new tool to evaluate the sympatho-vagal balance continuously. We determined the influence of the sympathetic nervous system both on the nocturnal PRA oscillations associated to increases in delta-wave activity and on the daytime oscillations that occur randomly in awake subjects. PRA and rRR were determined every 10 min during 24 h in nine healthy subjects under continuous bed rest. Electroencephalographic spectral analysis was used to establish the variations in delta-wave activity during sleep, from 2300-0700 h. The overnight profiles in PRA, rRR and delta-wave activity were analyzed using a modified version of the pulse detection program ULTRA. The temporal link among the profiles of rRR, PRA, and delta-wave activity was quantified using cross-correlation analysis. During sleep, large oscillations in PRA were strongly linked to variations in delta-wave activity. They were preceded by opposite oscillations in rRR, decreases in rRR reflecting predominant vagal activity, and increases in rRR reflecting sympathetic dominance. During the waking periods, the levels of rRR were higher, with smaller variations. The daytime PRA oscillations were not associated with any significant changes in rRR, and conversely, significant oscillations in rRR were not followed by any significant changes in PRA. In conclusion, the sympathetic nervous system is not directly involved in the generation of renin oscillations observed under basal conditions. During sleep, the oscillations in sympatho-vagal balance are inversely related to the variations in delta-wave activity and the associated renin release. The processes that give the intermittent signal for concomitant increases in slow wave activity and renin release from the kidney remain to be identified.

Role of the plasma and erythrocytes in veno-arterial portal changes during post prandial state in the rat

The determination of plasma and whole blood free amino acid concentrations in arterial and portal venous blood during post prandial state in the rat was used to estimate the role of the erythrocytes in amino acid exchanges. The erythrocyte contents were calculated from plasma, whole blood concentrations and the hematocrit. The veno-arterial concentration differences in plasma were significant for all amino acids except a-aminobutyrate and ornithine whereas in the erythrocytes only 8 amino acids exhibit significant differences (ASP, ALA, VAL, MET, ILE, LEU, TYR, PHE). For 6 amino acids, a significant correlation between the plasma and the erythrocyte concentration has been found (VAL, ILE, LEU, TYR, PHE, HIS). These data suggest that in vivo during the time of contact between blood and organ tissues, some amino acids but not all are significantly taken up by the erythrocytes. Thus, it may be concluded that erythrocyte amino acid blood transport in arterio-venous portal exchanges, concerns particularly tyrosine and essential amino acids. The erythrocyte amino acid transport represents quantitatively about 20 per cent of the total blood transport.

Endothelin participates in increased circulating atrial natriuretic peptide early after human heart transplantation

BACKGROUND

Hemodynamic improvement after heart transplantation is expected to normalize the neuroendocrine balance, but circulating atrial natriuretic peptide (ANP) remains elevated. Endothelin stimulates ANP secretion and its concentration increases after heart transplantation, suggesting a role for this peptide in the cardiovascular adaptative response to heart transplantation.

METHODS

To investigate whether endothelin may induce ANP increase in heart transplant recipients, we monitored daily ANP, endothelin, and related hormonal, biologic, and hemodynamic parameters before and during the first week after either heart transplantation (n = 15) or coronary artery bypass grafting (n = 10).

RESULTS

Surgery induced a transient secretory peak of arginine vasopressin and endothelin in both groups at day 1. Bypass grafting did not modify normal ANP (11.8 +/- 2.1 pmol/L), endothelin (2.4 +/- 0.3 pmol/L), renin activity (0.11 +/- 0.04 pmol/L/sec), or aldosterone (492 +/- 122 pmol/L) values. Heart transplantation normalized the renin-aldosterone axis, but the early decrease observed for ANP (from 27.2 +/- 4.8 to 21.14 +/- 1.4 pmol/L) was only partial and transient. Endothelin further increased (from 4.4 +/- 0.8 to 9.14 +/- 1.8 pmol/L; p < 0.01) after transplantation. Positive correlations were observed between endothelin, isoproterenol dose, creatinine, right atrial pressure, and ANP, but multiple correlation analysis showed the important role of endothelin (r = 0.69, p < 0.001). Cyclic guanosine monophosphate correlated with ANP (r = 0.65, p < 0.001).

CONCLUSIONS

Elevated endothelin, suggesting vascular dysfunction, likely contributes to the ANP increase observed early after heart transplantation. Furthermore, ANP, through a cardiac endothelium feedback, may act in the maintenance of circulatory homeostasis in heart transplant recipients.

Contrast echocardiography in coronary artery diseased patients: effect of systemic and pulmonary artery pressures on left heart opacification after intravenous injection of Albunex

BACKGROUND

Contrast echocardiography is a useful tool for assessing repeatedly patients with coronary artery disease. Nevertheless, elevated pulmonary artery and systemic blood pressures likely to be associated with cardiac ischemia may limit the left ventricular opacification (LVO) because of the microspheres' sensitivity to pressure.

OBJECTIVE

To determine the effects of systemic and pulmonary artery blood pressures on LVO.

METHODS

We performed 55 intravenous injections (0.08 and 0.22 ml/kg) of a new transpulmonary contrast agent (Albunex), during two separated exposures, into 20 cardiac ischemic patients while monitoring invasively their cardiac indexes, and intracardiac, systemic, and pulmonary artery blood pressures. LVO was graded qualitatively from faint to full.

RESULTS

A logistic model with the grade of LVO as the dependent variable and a selection from among the dose, exposure, right and left atrial blood pressures, systolic systemic and pulmonary artery blood pressures (ranges 94-208 and 14-45 mmHg, respectively), cardiac index, stroke index, and pulmonary and systemic vascular resistances as the explanatory variables demonstrated that increasing the dose gives an increasing probability of LVO (P = 0.02) and that increasing the pulmonary artery pressure reduces that probability (P = 0.006). A decreased cardiac index tended also to be associated with decreased LVO. The systemic blood pressure and the pulmonary and systemic vascular resistances had no statistically significant effect on the grade of LVO.

CONCLUSIONS

LVO after intravenous administration of Albunex is dose-dependent and limited by an elevated pulmonary artery pressure. These data suggest that one should use higher doses for cardiac ischemic patients with elevated pulmonary artery pressures and that use of Albunex has the potential to detect pulmonary hypertension in patients.