Effects Of Changes In Blood Pressure Research Articles

Relationship between changes in late-life blood pressure and the risk of frailty and mortality among older population in China: a cohort study based on CLHLS.

The evidence regarding the effects of blood pressure changes on older individuals remains inconclusive, and the impact of frailty throughout the life course is not known. We investigated the associations of different change patterns of blood pressure during 3-year intervals with frailty and mortality. Participants included 7335 persons from 2008 to 2014 of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Change in blood pressure was calculated as the difference between follow-up and baseline. Frailty was evaluated using a 40-item frailty index. Mortality status was ascertained up to December 31, 2014. The mean age of participants was 82.6 ± 10.7 years. The optimal blood pressure level (SBP, 130-150 mmHg; DBP, 70-90 mmHg) was associated with the lowest risk of frailty while decreasing follow-up SBP and DBP were significantly correlated with frailty. Lower baseline blood pressure levels (SBP < 130 mmHg; DBP < 70 mmHg) were associated with decreased mortality risk when participants increased their blood pressure to optimal levels during follow-up SBP and DBP (0.78, 0.63-0.98), compared to maintaining a steady low SBP (< 130 mmHg) and DBP (< 70 mmHg). For those with DBP around 70-90 mmHg, decreasing follow-up DBP (< 70 mmHg) was associated with higher mortality (1.23, 1.07-1.42) compared to maintaining stable follow-up DBP (70-90 mmHg). These results remain significant after adjusting for frailty. Optimal blood pressure levels were associated with the lowest risk of frailty. The association between lower blood pressure and increased mortality risk persisted even after accounting for frailty. We used a nationally representative longitudinal cohort study by using 2008-2014 of the Chinese Longitudinal Healthy Longevity in China. Change in blood pressure was calculated as the difference between follow-up and baseline. We investigated the associations of different change patterns of blood pressure during 3-year intervals with frailty and mortality.

Impact of blood pressure changes on myocardial work indices in hypertensive patients in a day.

Evaluating left ventricular function through instantaneous left ventricular deformation parameters might not always be accurate for patients with high fluctuations in blood pressure value due to afterload dependence. Myocardial work (MW) is a more advanced tool that combines global myocardial longitudinal strain (GLS) with LV (left ventricular) systolic pressure. The purpose of this study was to investigate the effect of blood pressure changes on MW indices in the population with normal blood pressure and hypertension in a day. A total of 117 participants (34 control subjects and 83 hypertensive patients) underwent echocardiographic measurements at rest, twice a day. Simultaneously, the brachial blood pressure was also measured. LV pressure‐strain loop (PSL) was used to calculate global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE). The differences in the GLS and MW indices between the groups were compared, and the correlation of blood pressure changes with the changes in GLS and MW indices were evaluated. Compared to the control group, the hypertensive group showed higher GWI, GCW, and GWW but lower GLS and GWE. Absolute changes in blood pressure, GLS, and MW indices in hypertensive patients were significantly higher than that of the control subjects. Blood pressure changes had significant univariate correlation with changes in GLS and MW indices. In conclusion, significant fluctuations in blood pressure could induce changes in MW indices to preserve left ventricular systolic function. Repeated assessment of MW indices is necessary for hypertensive patients with large blood pressure fluctuations.

Blood Pressure Changes in a Chinese Population Have a Greater Impact on Short-Term Outcomes Rather Than Long-Term Outcomes of Major Adverse Cardiovascular Events.

The purpose of our study was to explore the association of blood pressure (BP) changes on short-and long-term outcomes of major adverse cardiovascular events (MACEs) in rural China. This study was designed to learn the effects of BP changes (2004-2008) on short-term (2008-2010, within 2 years of the initial examination) and long-term (2008-2017) outcomes of MACE, including 24 285 and 27 290 participants, respectively. In this study, 423 (short-term) and 1952 (long-term) MACEs were identified. For prehypertension to hypertension, the risk of long-term stroke was increased (hazard ratio [HR] = 1.18 [1.00-1.39]). For hypertension to prehypertension, the short-term MACE risk (0.65 [0.47-0.90]), short-term stroke risk (0.45 [0.26-0.76]), and long-term stroke risk (0.83 [0.70-0.99]) all decreased. Short-term outcomes conferred a stronger impact than long-term outcomes (Fisher Z test, measured as the difference of β coefficients, all P < .05).

Short-term blood pressure changes have a more strong impact on stroke and its subtypes than long-term blood pressure changes.

BackgroundElevated blood pressure (BP) is closely related to stroke and its subtypes. However, different time periods changes in BP may result in differential risk of stroke.HypothesisShort‐term blood pressure changes have a more strong impact on stroke and its subtypes than long‐term blood pressure changes.MethodsWe designed the study on the effects of short‐ (2008‐2010) and long‐term (2004‐2010) BP changes on stroke events (2011‐2017), including 22 842 and 28 456 subjects, respectively. The difference in β coefficients between short‐ and long‐term BP changes on the effects of stroke were examined using the Fisher Z test.ResultsDuring a median 12.5‐year follow‐up period, 1014 and 1505 strokes occurred in short‐ and long‐term groups. In short‐term group, going from prehypertension to hypertension, the risk of stroke events increased (stroke: hazard ratio [HR] = 1.537 [1.248‐1.894], ischemic stroke: 1.456 [1.134‐1.870] and hemorrhagic stroke: 1.630 [1.099‐2.415]); going from hypertension to prehypertension, the risk of stroke events decreased (stroke:0.757 [0.619‐0.927] and hemorrhagic stroke:0.569 [0.388‐0.835]). Similarly, in long‐term group, going from prehypertension to hypertension, individuals had an increased risk of stroke (1.291, 1.062‐1.569) and hemorrhagic stroke (1.818, 1.261‐2.623); going from hypertension to prehypertension, participants had a decreased risk of stroke (0.825, 0.707‐0.963) and hemorrhagic stroke (0.777, 0.575‐0.949). Furthermore, the effects of BP changes during short‐term period on stroke events were greater than that in long‐term period.ConclusionsShort‐ and long‐terms BP changes were both associated with the risk of stroke events. Furthermore, short‐term BP changes had a stronger impact than did long‐term changes on risk of stroke events.

Blood Pressure Changes Have a More Strong Impact on Short- than Long-Term Outcomes of Major Adverse Cardiovascular Events

Background: Whether blood pressure (BP) changes have a different impact on short- and long-term outcomes of major adverse cardiovascular events (MACE) remains unclear. Therefore, we aimed to investigate and compare the effects of BP changes on short- and long-term outcomes of MACE. Methods: We conducted a prospective cohort study, which consisted of four examinations: baseline, 2008, 2010, and 2017 follow-up. BP changes were measured from baseline to 2008, short- and long-term outcomes were defined by incident events occurred from 2008 to 2010 and 2008 to 2017, respectively. The final analysis was restricted to 24,495 and 27,522 participants in short- and long-term analysis. Adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs). The difference of β coefficients between short- and long-term outcomes were examined using Fisher Z test. Findings: During a median follow-up of 12·5-years, 451 (216 stroke, 33 myocardial infarction, 219 CVD deaths) and 2,025 (1,532 stroke, 371 myocardial infarction, 991 CVD deaths) MACE were identified during short- and longterms, respectively. For prehypertension to hypertension, the HR (95% CI) were 1·36 (1·00-1·84) for short-term MACE, 1·19 (1·01-1·40) for long-term stroke. For hypertension to prehypertension, 0·66 (0·49-0·91) for short-term MACE, 0·46 (0·27-0·78) for short-term stroke, 0·82 (0·69-0·97) for long-term stroke. Furthermore, short-term outcomes conferred a stronger impact than long-terms (measured as β coefficients, all P<0·05). Interpretation: BP changes were significantly associated with MACE and its subtypes for the short- and long-terms, and short-term outcomes conferred a strong impact than long-terms. Funding Statement: This research was partly supported by funds from National Nature Science Foundation of China (No. 81773510), Nature Science Foundation of Liaoning Province (No. 20170541048), National Key R&D Program of China (Grant #2017YFC1307600), and National Key R&D Program of China (Grant #2018YFC1311600). Declaration of Interests: The authors state: none. Ethics Approval Statement: The research protocol was approved by the China Medical University Research Ethics Committee, and written informed consent was formally obtained from all the participants or their guardians

Blood pressure and age-related GFR decline in the general population

BackgroundHypertension is one of the most important causes of end-stage renal disease, but it is unclear whether elevated blood pressure (BP) also accelerates the gradual decline in the glomerular filtration rate (GFR) seen in the general population with increasing age. The reason may be that most studies have considered only baseline BP and not the effects of changes in BP, antihypertensive treatment and other determinants of GFR during follow-up. Additionally, the use of GFR estimated from creatinine or cystatin C instead of measurements of GFR may have biased the results because of influence from non-GFR related confounders. We studied the relationship between BP and GFR decline using time-varying variables in a cohort representative of the general population using measurements of GFR as iohexol clearance.MethodsWe included 1594 subjects aged 50 to 62 years without baseline diabetes, kidney-, or cardiovascular disease in the Renal Iohexol-clearance Survey in Tromsø 6 (RENIS-T6). GFR, BP, antihypertensive medication and all adjustment variables were ascertained at baseline, and at follow-up after a median observation time of 5.6 years in 1299 persons (81%). The relationship between GFR decline and BP was analyzed in linear mixed models.ResultsThe mean (standard deviation) GFR decline rate was 0.95 (2.23) mL/min/year. The percentage of persons with hypertension (systolic BP ≥ 140 mmHg, diastolic BP ≥ 90 mmHg or antihypertensive medication) increased from 42 to 52% between baseline and follow-up. In multivariable adjusted linear mixed models using time-varying independent variables measured at baseline and follow-up, higher systolic and diastolic BP were associated with slower GFR decline rates by 0.10 and 0.20 mL/min/year/10 mmHg, respectively (p < 0.05). The association was stronger in persons on antihypertensive medication than in others (p < 0.05 for the interaction between BP and antihypertensive medication).ConclusionsIn the medium-term, elevated BP is not associated with accelerated GFR decline in the general middle-aged population. In persons using antihypertensive medication, elevated BP is associated with a paradoxical slower GFR decline. Studies with even longer observation periods are needed to evaluate the ultimate effect of BP on kidney function.

The impact of an experimentally induced increase in arterial blood pressure on left ventricular twist mechanics.

The effects of isometric hand-grip exercise (IHG) coupled with a period of postexercise circulatory occlusion (OCC; known to sustain exercise-induced increases in blood pressure while facilitating a decrease in heart rate) on left ventricular (LV) twist mechanics was examined. Two-dimensional speckle-tracking echocardiography was used to assess LV apical and basal rotation and LV twist in 19 healthy participants (23 ± 2 years old) at rest, during 3 min of IHG (performed at 40% maximal voluntary contraction) and 3 min of OCC immediately following IHG. The IHG elicited significant (P < 0.001) increases in mean arterial pressure (rest, 91 ± 1 mmHg; IHG, 122 ± 2 mmHg) and heart rate (rest, 65 ± 2 beats min(-1); IHG, 91 ± 4 beats min(-1)). Mean arterial pressure remained elevated during OCC (116 ± 2 mmHg; P < 0.001 versus rest), whereas heart rate returned to resting levels (68 ± 3 beats min(-1); P = 0.159 versus rest). Apical rotation decreased significantly (P < 0.01) by 10 ± 5% during IHG and 21 ± 4% during OCC, whereas basal rotation remained unchanged from rest. Left ventricular twist decreased from rest to IHG (12 ± 5%; P = 0.015) and OCC (21 ± 4%; P = 0.001), whereas a decrease in LV untwist rate was observed only during OCC. An increase in blood pressure generated by IHG, and maintained by a period of OCC, impairs aspects of LV twist mechanics. Postexercise circulatory occlusion isolated the effect of the arterial blood pressure rise (from heart rate), magnifying the impairment of LV twist mechanics when compared with IHG, whilst also negatively impacting LV relaxation. We propose that a protocol using isometric exercise followed by circulatory occlusion provides a method for studying the effects of blood pressure changes on LV twist mechanics.

The Effect of Nocturnal Blood Pressure Changes on the Cognitive State of Patients With Parkinson’s Disease

This article has been retracted by the authors. Background: Recent data have revealed that cognitive involvement occurs, more or less, in every stage of idiopathic Parkinson’s disease (IPD), which is definitely going to cause radical changes in this traditional understanding. The effects of blood pressure changes during the night on the cognitive states of patients with IPD are not known for sure. The purpose of this study was to research the effects of blood pressure changes during the night on cognitive state of patients with IPD. Methods: A total of 30 patients, 14 females and 16 males, were followed with a diagnosis of IPD. Cognitive functions were assessed with an extensive neuropsychological test battery. Results: The fifth stage of Stroop test, test of line direction, test of face recognition and Hooper test were significantly different in dipper group when compared with the non-dipper group. Conclusion: Not having nocturnal blood pressure decrease in IPD can be accepted as a risk factor in terms of cognitive function disorders. J Neurol Res. 2015;5(3):207-212 doi: http://dx.doi.org/10.14740/jnr324w

The Effect of Nocturnal Blood Pressure Changes on the Cognitive State of Patients With Parkinson’s Disease

This article has been retracted by the authors. Background: Recent data have revealed that cognitive involvement occurs, more or less, in every stage of idiopathic Parkinson’s disease (IPD), which is definitely going to cause radical changes in this traditional understanding. The effects of blood pressure changes during the night on the cognitive states of patients with IPD are not known for sure. The purpose of this study was to research the effects of blood pressure changes during the night on cognitive state of patients with IPD. Methods: A total of 30 patients, 14 females and 16 males, were followed with a diagnosis of IPD. Cognitive functions were assessed with an extensive neuropsychological test battery. Results: The fifth stage of Stroop test, test of line direction, test of face recognition and Hooper test were significantly different in dipper group when compared with the non-dipper group. Conclusion: Not having nocturnal blood pressure decrease in IPD can be accepted as a risk factor in terms of cognitive function disorders. J Neurol Res. 2015;5(3):207-212 doi: http://dx.doi.org/10.14740/jnr324w

Systolic and diastolic blood pressure changes in relation with myocardial infarction and stroke in patients with coronary artery disease.

Excessively high and low achieved blood pressure (BP) may be associated with a bad outcome in patients with coronary artery disease, the J curve phenomenon. The effect of BP changes from baseline in relation with the subsequent risk of stroke and myocardial infarction (MI) is unknown. Of the 25 620 patients randomized in the Ongoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET) study, we selected 19 102 patients with coronary artery disease at baseline. BP at entry was 141/82 mm Hg, and its average decrease during follow-up was 7/6 mm Hg. BP entered the analysis as time-varying variable modeled with restricted cubic splines. After adjustment for several potential determinants of reverse causality, a change in BP from baseline by -34/-21 mm Hg (10th percentile) was associated with a lesser risk of stroke without any significant increase in the risk of MI. A rise in systolic/diastolic BP from baseline by 20/10 mm Hg (90th percentile) was associated with an increased risk of stroke, whereas the risk of MI increased with systolic BP and not with diastolic BP. In conclusion, in patients with coronary artery disease and initially free from congestive heart failure, a BP reduction from baseline over the examined BP range had little effect on the risk of MI and predicted a lower risk of stroke. An increase in systolic BP from baseline increased the risk of stroke and MI. The relationships of BP with risk were much steeper for stroke than for MI. A treatment-induced BP reduction over the explored range seems to be safe in patients with coronary artery disease. http://www.clinicaltrials.gov. Unique identifier: NCT00153101.

Ocular pulse amplitude and retrobulbar blood flow change in dipper and non-dipper individuals

To evaluate ocular pulse amplitude (OPA), IOP values, and hemodynamic changes in the ophthalmic artery, central retinal artery, and short posterior ciliary artery in dipper and non-dipper patients. A total of 59 right eye measurements of healthy subjects with normotensive were included to the study. Ambulatory blood pressure (BP) monitoring measurement (ABPM), Doppler imaging, and OPA measurements were performed in the same day. The patients in which systolic BP decreased during the nocturnal time by 10% of the diurnal BP or more were called dippers. A patient whose nocturnal systolic BP fell by <10% or even rose was defined as non-dipper. Color Doppler imaging was used for blood flow velocity assessment of ophthalmic, central retinal, and posterior ciliary arteries. For each artery, peak systolic and end-diastolic velocities (PSV and EDV, respectively), resistive index (RI), and pulsalite index (PI) were automatically calculated by the machine. Mean IOP and OPA values were calculated after three consecutive measurements. The mean OPA in non-dipper patients was significantly lower compared with that of dipper patients (P=0.011). There was no significant difference in IOP levels between groups. There was no significant difference in the PSV, EDV, RI, and PI in the ophthalmic, posterior ciliary, and central retinal arteries between the groups. Our study demonstrated that OPA level in non-dippers is lower than dippers. This may give additional information about the effect of BP changes on OPA values.

Pressure autoregulation, intracranial pressure, and brain tissue oxygenation in children with severe traumatic brain injury

Cerebral pressure autoregulation is an important neuroprotective mechanism that stabilizes cerebral blood flow when blood pressure (BP) changes. In this study the authors examined the association between autoregulation and clinical factors, BP, intracranial pressure (ICP), brain tissue oxygen tension (PbtO(2)), and outcome after pediatric severe traumatic brain injury (TBI). In particular we examined how the status of autoregulation influenced the effect of BP changes on ICP and PbtO(2). In this prospective observational study, 52 autoregulation tests were performed in 24 patients with severe TBI. The patients had a mean age of 6.3 +/- 3.2 years, and a postresuscitation Glasgow Coma Scale score of 6 (range 3-8). All patients underwent continuous ICP and PbtO(2) monitoring, and transcranial Doppler ultrasonography was used to examine the autoregulatory index (ARI) based on blood flow velocity of the middle cerebral artery after increasing mean arterial pressure by 20% of the baseline value. Impaired autoregulation was defined as an ARI < 0.4 and intact autoregulation as an ARI >or= 0.4. The relationships between autoregulation (measured as both a continuous and dichotomous variable), outcome, and clinical and physiological variables were examined using multiple logistic regression analysis. Autoregulation was impaired (ARI < 0.4) in 29% of patients (7 patients). The initial Glasgow Coma Scale score was significantly associated with the ARI (p = 0.02, r = 0.32) but no other clinical factors were associated with autoregulation status. Baseline values at the time of testing for ICP, PbtO(2), the ratio of PbtO(2)/PaO(2), mean arterial pressure, and middle cerebral artery blood flow velocity were similar in the patients with impaired or intact autoregulation. There was an inverse relationship between ARI (continuous and dichotomous) with a change in ICP (continuous ARI, p = 0.005; dichotomous ARI, p = 0.02); that is, ICP increased with the BP increase when ARI was low (weak autoregulation). The ARI (continuous and dichotomous) was also inversely associated with a change in PbtO(2) (continuous ARI, p = 0.002; dichotomous ARI, p = 0.02). The PbtO(2) increased when BP was increased in most patients, even when the ARI was relatively high (stronger autoregulation), but the magnitude of this response was still associated with the ARI. There was no relationship between the ARI and outcome. These data demonstrate the influence of the strength of autoregulation on the response of ICP and PbtO(2) to BP changes and the variability of this response between individuals. The findings suggest that autoregulation testing may assist clinical decision-making in pediatric severe TBI and help better define optimal BP or cerebral perfusion pressure targets for individual patients.

Clinical Significance and Reproducibility of New Arterial Distensibility Index

The brachial-ankle pulse wave velocity (baPWV) is used to evaluate the degree of atherosclerosis and arterial distensibility, but its major limitation is that it is affected by changes in blood pressure (BP) during measurement. Recently, a new atherosclerotic index, the cardio-ankle vascular index (CAVI), has been developed by measuring PWV and BP. CAVI is adjusted for BP based on the stiffness parameter beta and should measure arterial stiffness independent of BP. The purpose of this study was to evaluate the validity of CAVI compared with baPWV, the reproducibility of the measurement of CAVI, and the effect of BP changes on CAVI and baPWV. One thousand and thirty-three consecutive subjects undergoing health checkups were studied. CAVI was automatically calculated from the pulse volume record, BP, and the vascular length from heart to ankle. In this general population, both baPWV and CAVI demonstrated a positive correlation with age and systolic BP (SBP). CAVI showed a weaker correlation with SBP than baPWV. The measurement of CAVI demonstrated good reproducibility and was not affected by the increase in BP during measurement. CAVI is a useful index of arterial distensibility and is not influenced by BP changes during measurement.

Association between course of blood pressure within the first 24 hours and functional recovery after acute ischemic stroke

Study objective The relation between course of blood pressure within the first 24 hours after acute stroke and early neurologic outcome remains a matter of dispute. We investigate this relation with adjustment for other influencing variables. Methods Three hundred seventy-two patients with the diagnosis of ischemic stroke were included to evaluate the relation between blood pressure course and early neurologic outcome. The following data were collected: age; sex; history of hypertension, diabetes mellitus, hyperlipidemia, coronary heart disease, peripheral vascular disease, and stroke; smoking habits; preadmission blood pressure, blood pressure on admission, and blood pressure 24 hours later; antihypertensive treatment; and stroke localization. We assessed outcome at day 5 after admission as dependent or independent (Rankin Scale score ≤2) and applied multivariate logistic regression analysis to investigate the effect of blood pressure changes on outcome, with adjustment for other baseline variables. Results Relative changes of systolic and diastolic blood pressure within hospital admission to 24 hours after admission revealed significant differences of patients' neurologic outcome only for diastolic blood pressure changes from admission to 24 hours. A diastolic blood pressure decrease more than 25% from admission until 24 hours after admission was associated with a 3.8-fold increased adjusted odds (95% confidence interval 1.2 to 12.1) for poor neurologic outcome on day 5 (Rankin Scale score 3 to 5). Conclusion Excessive diastolic blood pressure reduction was associated with an increased risk for an impaired neurologic outcome in patients with ischemic stroke. The association between both characteristics was independent from concomitant risk factors, stroke localization, and possible antihypertensive treatment.

Hypoperfusion and Its Augmentation in Patients with Brain Ischemia.

Control of hypertension is a well-established goal of the primary and secondary prevention of stroke. However, management of blood pressure in the setting of acute brain ischemia is complicated by the possible effect of blood pressure changes on cerebral perfusion. In acute stroke, patients may have an ischemic penumbra of brain tissue, which has impaired perfusion but which is not irreversibly damaged. The ischemic penumbra may be salvaged with reperfusion. Lowering of blood pressure in this setting, however, would hasten the progression of the penumbra to infarction. With the exception of patients treated with thrombolytic agents, blood pressure reduction is not recommended in acute ischemic stroke for this reason. Preliminary studies suggest that there may be a role for interventions to elevate blood pressure as a treatment for acute stroke patients. Despite interest in induced hypertension as a treatment of stroke dating back to the 1950s, this practice has not achieved widespread use owing to concerns about potential adverse effects such as intracerebral hemorrhage, cerebral edema, and myocardial ischemia. It is commonly used, however, to treat patients with threatened cerebral ischemia due to vasospasm after subarachnoid hemorrhage. Until future studies clarify the effectiveness of induced hypertension in stroke treatment, maintaining adequate blood pressure and fluid volume is recommended for patients with acute ischemic stroke, particularly if the neurologic deficits are fluctuating or the patient has persistent large-vessel occlusive disease.

Blood pressure elevation after phenylephrine infusion may adversely affect myocardial perfusion in patients with coronary artery disease

Background: Although blood pressure is a major determinant of myocardial oxygen-demand, little information is currently available regarding the changes in blood pressure (BP) during myocardial ischemia. Since BP elevation may cause left ventricular (LV) wall stress and an increase in oxygen demand, infusion of an α-adrenergic agonist, such as phenylephrine (PH), may provoke changes in myocardial perfusion in coronary artery disease (CAD) patients. As the effects of BP changes alone on myocardial perfusion have never been assessed by thallium-201 (Tl) scintigraphy, we investigated the effects of BP elevation after PH infusion, in order to study the hypothesis that pressure loading alone without increases in heart rate, may provoke transient impairment of regional myocardial perfusion, in CAD patients. Patients and methods: Forty-one (41) patients with angiographically documented CAD, aged 54±8 years, were included in our study. Each patient was given, without any complications, a PH (0.1 mg/ml) dose infused at a rate of 0.8 ml/mm, determined by a standardisation procedure and producing a mean blood pressure elevation of approximately 30% above baseline levels and a heart rate response to levels of no less than 50 bpm. One minute after the desired blood pressure and heart rate responses were reached, 2 mCi of Tl were injected and the PH infusion continued until the termination of the test. Tl scintigraphy was performed both 2 min after Tl injection and 4 h later, while the results were correlated to coronary angiography findings. Results: PH scintigraphy produced 152 total defects. The mean perfusion defect size (%) was 14±12 and was directly related to the number of diseased vessels, i.e., 2% for one-vessel disease, 15% for two-vessel disease and 25% for three-vessel disease ( P<0.05). The lowest percentage Tl activity values were 56±14 and were inversely related to the number of diseased vessels ( P<0.01). The mean Tl lung counts/pixel values were 25±8 while it increased as the number of diseased vessels increased ( P<0.01). The mean lung/heart ratio values were 0.31±0.08 while it increased as the number of diseased vessels increased ( P<0.01). Conclusion: BP elevation after PH loading, produces a significant impairment of myocardial perfusion, that correlates well with the extend of angiographic findings.

Noradrenaline Release in the Rat Subfornical Organ Area to Blood Pressure Changes

To verify whether noradrenergic inputs to the subfornical organ (SFO) are involved in the control system of arterial pressure, we investigated the effects of blood pressure changes on noradrealine (NA) release in the SFO and its surrounding sites using microdialysis techniques in rats. Hemorrhage (5 or 10 ml/kg) significantly increased the NA concentration in the region of the SFO, but did not cause significant changes in the sites away from the SFO. An elevation in arterial pressure following intravenous administration of the α-agonist metaraminol slightly decreased the NA level in the region of the SFO. These results imply that the noradrenergic neural inputs to the SFO area may be involved in the control of cardiovascular function.

Cardiac sympathetic premotor neurons.

To locate premotor neurons controlling the cardiac sympathetic supply and to determine their relation to brain stem vasomotor pathways, the rostral ventrolateral medulla (RVLM) was mapped in seven chloralose-anesthetized cats, with the use of microinjections of sodium glutamate (5-10 nl, 0.1 M) to excite neuronal cell bodies. Cardiac sympathetic responses were recorded from the ipsilateral inferior cardiac nerve, while recordings were made simultaneously from postganglionic vasoconstrictor fibers to skeletal muscle (ipsilateral peroneal nerve). Baroreceptors were denervated to eliminate the reflex effects of blood pressure changes. Most of the 115 injected RVLM sites excited both sympathetic nerves. Inferior cardiac nerve activity increased by up to 395% (mean 105 +/- 86%, SD), and muscle vasoconstrictor activity increased by up to 487% (110 +/- 107%). Their relative response varied with injection site, however. For 16 of the most rostromedial injections, the inferior cardiac nerve-to-muscle vasoconstrictor response ratio exceeded that expected by two- to sevenfold; for 9 very caudolateral injections that ratio was strongly reversed, favoring muscle vasoconstrictors by two to fivefold. Intervening sites gave more equal responses. Overall, the response ratio varied systematically with injection site. These findings demonstrate that neurons with preferential or selective actions on the cardiac sympathetic outflow are present in the RVLM and are organized topographically. The simplest interpretation is that a population of selective cardiac sympathetic premotor neurons occupies a territory substantially overlapping, but centered rostromedially to, the population controlling vasoconstriction in muscle.

The influence of blood pressure on intracellular Ca2+ content in erythrocytes: effects of cadmium chloride and nifedipine.

Cellular abnormalities associated with elevated Ca2+ concentrations have been postulated to be involved in the pathogenesis of hypertension. The present study was undertaken to investigate the effects of blood pressure changes on cytosolic Ca2+ levels in erythrocytes. Cadmium, which has been implicated in the etiology of hypertension was used as the hypertensive agent and the classical blocker of voltage-operated calcium channels nifedipine was used to treat hypertension. 10 weeks old male rats were divided into four groups; control, CdCl2, CdCl2 and nifedipine, nifedipine groups. CdCl2 caused elevations in blood pressure and in the cytosolic erythrocyte Ca2+ levels both of which were reduced after nifedipine administration. After nifedipine alone, cytosolic Ca2+ levels were increased. These findings suggest that cytosolic Ca2+ content decreasing action of nifedipine in the CdCl2 and nifedipine applied group could be secondary to the antihypertensive action.

Effect of Blood Pressure Changes on Air Flow Dynamics in the Upper Airway of the Decerebrate Cat

Previous studies suggest that upper airway neuromuscular activity can be affected by changes in blood pressure via a baroreceptor-mediated mechanism. It was hypothesized that increases in blood pressure would increase upper airway collapsibility predisposing to airway obstruction at a flow-limiting site in the hypopharynx. To examine the effect of blood pressure on upper airway function, maximal inspiratory air flow was determined through the isolated feline upper airway before, during, and after intravenous infusion of phenylephrine (10-20 micrograms.kg-1.min) in six decerebrate, tracheotomized cats. Inspiratory flow, hypopharyngeal pressure, and pressure at the site of pharyngeal collapse were recorded as hypopharyngeal pressure was rapidly decreased to achieve inspiratory flow limitation in the isolated upper airway. Pressure-flow relationships were used to determine maximal inspiratory air flow and its mechanical determinants, the upper airway critical pressure (a measure of pharyngeal collapsibility), and the nasal resistance upstream to the site of flow limitation. An increased mean arterial blood pressure of 71 +/- 16 mmHg (mean +/- SD) was associated with significant decrease in maximal inspiratory air flow from 147 +/- 38 ml/s to 115 +/- 27 ml.sec-1 (P < 0.01). The decrease in maximal inspiratory air flow was associated with an increase in upper airway critical pressure from -8.1 +/- 3.8 to -5.7 +/- 3.7 cm H2O (p < 0.02), with no significant change in nasal resistance. When blood pressure was decreased to baseline by discontinuing the phenylephrine infusion, maximal inspiratory air flow and upper airway critical pressure returned to their baseline values. Increased blood pressure increased the severity of upper airway air flow obstruction by increasing pharyngeal collapsibility. Previous studies relating baroreceptor activity to neuromuscular regulation of upper airway tone, are consistent with this effect being mediated by afferent activity from baroreceptors. These findings warrant further study because they suggest the possibility that upper airway obstruction in postoperative patients could either be caused or exacerbated by an increase in blood pressure.