human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background and Purpose — The purpose of this study was to investigate the effect of the angiotensin-converting enzyme inhibitor perindopril on mean arterial blood pressure ( MABP ) , cerebral blood flow ( CBF ) , and glomerular filtration rate in hypertensive stroke patients with moderate to severe internal carotid artery ( ICA ) disease or ICA occlusion . Methods — Twenty-four nonacute ischemic stroke patients who had MABP readings > 100 mm Hg and moderate to severe ICA stenosis or occlusion were r and omized to receive perindopril 4 mg daily or placebo for 14 days . MABP , ICA flow , and both middle cerebral artery ( MCA ) velocity and resistance index were measured before dose , at 5 time points over the subsequent 24 hours , and finally at 2 weeks . Brain hexamethyl propylene amine oxide single photon emission computed tomography scans were performed before drug administration and at time of peak drug effect ( 6 to 8 hours ) after the first dose . Glomerular filtration rate was measured with 51Cr EDTA before medication and at 14 days . Results — A placebo-corrected BP fall of 17/10 mm Hg was seen ( P = 0.017 ) , which was maximal at 5.5 hours . No significant change in ICA flow or MCA velocity was seen between groups . No significant change in hemispheric CBF was seen . The mean change from baseline in the treated group was −0.79 mL · 100 g−1 · min−1 ( 95 % confidence interval [ CI ] , 1.65 to −3.23 ) ; mean change in the placebo group was −1.9 mL · 100 g−1 · min−1 ( 95%CI , 3.02 to −6.92 ) . Peri-infa rct CBF was similarly unaffected . One of the treated patients developed transient acute renal impairment and was withdrawn from the study on day 4 . Conclusions — Perindopril lowers BP without lowering CBF in hypertensive stroke patients with moderate to severe ICA stenosis or occlusion ; monitoring of this patient population for the complications of renal artery stenosis should be considered Abstract Purpose : The aim of the study was to compare effect of perindopril ( 4 mg once a day ) versus acebutolol ( 400 mg once a day ) on cerebral hemodynamics in hypertensive patients . Methods : Thirty untreated patients with mild-to-mode-rate hypertension were studied . Drug influences on Doppler-derived parameters from the cerebral blood flow ( CBF ) velocity wave form were evaluated in a r and omized , double blind , cross-over , placebo controlled study . The mean CBF velocity , pulsatility index ( PI ) , cerebrovascular resistance and index of CBF were calculated from concomitant transcranial Doppler measurements and systemic blood pressure . Results : Acebutolol and perindopril significantly decreased systolic , diastolic and mean blood pressure in relation to placebo . The mean value of CBF velocity increased to a comparable level after both drugs ( 54.9 ± 9.1 cm/s on placebo vs 62.8 ± 14.5 cm/s on perindopril p < 0.01 and 61.4 ± 9.2 cm/s on acebutolol , p < 0.01 ) . Also , the cerebrovascular resistance index decreased similarly after both drugs ( 2.26 ± 0.35 on placebo vs 1.68 ± 0.42 on perindopril p < 0.01 and 1.7 ± 0.36 on acebutolol p < 0.01 ) . The calculated CBF index increased significantly after each drug ( 25.23 ± 7.99 on placebo vs 33.98 ± 11.23 p < 0.01 on perindopril and 30.90 ± 8.04 on acebutolol p < 0.01 ) . However , perindopril augmented the CBF index more effectively than acebutolol ( p < 0.05 ) . Conclusions : Among patients with mild-to-moderate hypertension  both acebutolol and perindopril beneficially decreased cerebrovascular resistance and increased the CBF index in comparison with placebo . The increase of CBF index was greater after perindopril than acebutolol , which suggests a more significant improvement in cerebral perfusion by perindopril . The non-invasive transcranial Doppler ultrasonography method of CBF velocity measurement may contribute to choosing optimal antihypertensive therapies and to monitor their effect OBJECTIVE To determine if previously hypertensive patients with acute ischemic stroke should be treated with antihypertensive medication in the immediate poststroke period . DESIGN R and omized double-blind , placebo-controlled trial . SETTING Sixteen consecutive hypertensive patients ( four men and 12 women ; mean age , 66 years [ age range , 46 to 83 years ] ) with middle cerebral artery infa rct ion within 72 hours of onset and blood pressure between 170 and 220 mm Hg(systolic ) and 95 and 120 mm Hg ( diastolic ) . INTERVENTION Placebo ( n = 6 ) , nicardipine hydrochloride ( 20 mg [ n = 5 ] ) , captopril ( 12.5 mg [ n = 3 ] ) , or clonidine hydrochloride ( 0.1 mg [ n = 2 ] ) given every 8 hours for 3 days . MAIN OUTCOME MEASURES Decline in blood pressure , change in cerebral blood flow as measured by single photon emission computed tomography , and clinical change as determined by the National Institutes of Health Stroke Scale . RESULTS Blood pressure fell significantly in both the drug-treated group as a whole and in those patients receiving placebo ( P < .001 ) . There was no difference in blood pressure levels between these two groups throughout the study period . Patients receiving nicardipine had a consistently lower pressure than the other groups . A significant negative relationship was noted between the maximum blood pressure fall and improvement in cerebral blood flow . There were four patients whose blood pressure dropped by more than 16 % of the baseline value on any 24 hours in the first 3 days . All either failed to increase or actually decreased their cerebral blood flow to the affected area . Three of these patients were treated with nicardipine . There was no significant difference in clinical course between the placebo- and drug-treated groups as a whole . CONCLUSIONS Hypertensive ischemic stroke patients with a moderate elevation of blood pressure in the first few days may not require antihypertensive therapy . Nicardipine and possibly other calcium channel blockers may cause an excessive fall in blood pressure and impair cerebral blood flow in these patients and should therefore be used with caution Background and Purpose — Angiotensin-converting enzyme ( ACE ) inhibitor – based therapy reduces the recurrence of stroke . The present study assessed the effects of long-term ACE inhibitor therapy on cerebral circulation in patients with previous minor stroke . Methods — After a run-in period , 19 patients were r and omized to ACE inhibitor therapy ( n=9 ; 4 mg of perindopril daily ; mean age , 64±8 years ; mean systolic/diastolic blood pressure [BP]±SD , 133±12/77±9 mm Hg ) or placebo therapy ( n=10 ; mean age , 66±9 years ; mean BP , 139±10/78±8 mm Hg ) . Cerebral blood flow ( CBF ) was measured during hypercapnia , normocapnia , and hypocapnia using a positron emission tomography with H215O at entry into the study and after 3 to 12 months . Cerebral perfusion reserve ( CPR ) was defined as percent CBF response to a 1 mm Hg change in arterial partial pressure of CO2 between hypercapnia and hypocapnia . Results — Systolic/diastolic BP and CBF during normocapnia showed no significant changes between entry and completion of the trial in the perindopril and placebo groups . Mean value of CPR showed a significant increase in the perindopril group ( from 3.7±1.7%/mm Hg to 4.8±1.7%/mm Hg ; P < 0.05 ) but not in the placebo group ( from 4.1±0.8%/mm Hg to 4.2±0.6%/mm Hg ; NS ) . Statistical parametric mapping analysis also showed global and significant increase ( P < 0.01 , uncorrected ) in CPR in the perindopril group alone . Conclusions — Long-term ACE inhibitor – based therapy had a beneficial effect on the cerebral circulation by improving CPR in patients with previous minor stroke Objectives : Prevalence studies of the association between blood pressure and headache have shown conflicting results . The aim was to analyse the relation between blood pressure and risk of headache in a prospect i ve study . Methods : A total of 22 685 adults not likely to have headache , had their baseline blood pressure measured in 1984–6 , and responded to a headache question naire at follow up 11 years later ( 1995–7 ) . The relative risk of headache ( migraine or non-migrainous headache ) was estimated in relation to blood pressure at baseline . Results : Those with a systolic blood pressure of 150 mm Hg or higher had 30 % lower risk ( risk ratio (RR)=0.7 , 95 % CI 0.6–0.8 ) of having non-migrainous headache at follow up compared with those with systolic pressure lower than 140 mm Hg . For diastolic blood pressure , the risk of non-migrainous headache decreased with increasing values , and these findings were similar for both sexes , and were not influenced by use of antihypertensive medication . For migraine , there was no clear association with blood pressure . Conclusion : In the first prospect i ve study of blood pressure and the risk of headache , high systolic and diastolic pressures were associated with reduced risk of non-migrainous headache . One possible explanation may be the phenomenon of hypertension associated hypalgesia , which probably involves the baroreflex system influencing nociception in the brain stem or spinal cord The effects of angiotensin II receptor blockers on cerebral hemodynamics in humans have not been well eluci date d. The present study evaluated the effects of losartan on cerebral hemodynamics in hypertensive patients using positron emission tomography . Ten patients with essential hypertension ( mean age , 60.8 years ) were examined . In each patient , regional cerebral blood flow was measured by [ O-15 ] labeled water positron emission tomography before and after the oral administration of losartan for 8 to 23 weeks . In 8 patients , the baseline regional cerebral blood flow measurement was followed by 1,000 mg of acetazolamide challenge to measure the cerebral perfusion reserve . Systemic blood pressures before and after treatment were 153.8±10.8/96.0±6.5 mmHg ( systolic mean±SD/diastolic mean±SD ) and 133.4±11.2/83.6±6.5 mmHg , respectively ; this difference was significant . The baseline global cerebral blood flow values before and after treatment were 38.4±6.9 ml/min/100 g and 38.2±8.2 ml/min/100 g , respectively ; this difference was not significant . The results of the global cerebral blood flow response to the acetazolamide challenges were not statistically different before and after treatment . A regional analysis showed no statistical difference in regional cerebral blood flow or cerebral perfusion reserve throughout the brain before and after treatment . Losartan 's effect on reducing the blood pressure did not affect either the baseline regional cerebral blood flow or the cerebral perfusion reserve in patients with mild to moderate hypertension . The inclusion of losartan in anti-hypertensive regimens could be advantageous for cerebral circulation in patients with essential hypertension We undertook a double-blind , placebo-controlled study to determine the effectiveness of verapamil hydrochloride for the prophylaxis of  migraine . Twelve patients were given either verapamil hydrochloride  , 80 mg four times daily , or placebo in r and om order during two consecutive three-month periods . Migraine frequency , severity , and duration were quantified by daily logs and monthly question naires . Ten of the 12 patients had fewer migraines during verapamil therapy . Migraine frequency decreased from 6.7 to 3.8 migraines per patient per month , for a mean decrease of 49 % . Headache unit index fell from an average of 0.61 to 0.44 . We conclude that verapamil is effective in the prophylaxis of migraine and that verapamil might be considered one alternative in the development of a regimen for the prophylaxis of migraine The aim of this study was to evaluate changes in cerebral hemodynamics in young patients with uncomplicated hypertension before and after effective antihypertensive treatment with a beta-blocker drug . Changes in mean flow velocity in the middle cerebral artery from normal condition to hypercapnia were evaluated by means of a transcranial Doppler in 42 hypertensive patients and 21 healthy subjects comparable for age and sex distribution . We obtained hypercapnia with breath-holding and evaluated cerebrovascular reactivity with the breath-holding index ( BHI ) . After a baseline evaluation ( time 0 ) , patients were r and omly assigned to a placebo ( group 1 ) or atenolol ( group 2 ) therapy . The evaluation was repeated after 30 ( time  
    Output:
    
agent
Antihypertensive drugs reduce headache but it is unclear whether there are differences between drug classes .
Calcium channel blockers ( CCBs ) decrease variability in systolic blood pressure ( SBPV ) and stroke risk more than other classes , possibly due to decreased vascular tone .
If so , there might be a correlation between drug-class effects on variability in SBP and on headache .
Antihypertensive drugs reduce headache but the effect differs between classes , corresponding to their effects on SBPV and the risk of stroke .
This may partly be explained by consistent antihypertensive class effects on vascular tone in the peripheral ( variability ) and cerebrovascular circulations ( headache )
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background and Purpose — The purpose of this study was to investigate the effect of the angiotensin-converting enzyme inhibitor perindopril on mean arterial blood pressure ( MABP ) , cerebral blood flow ( CBF ) , and glomerular filtration rate in hypertensive stroke patients with moderate to severe internal carotid artery ( ICA ) disease or ICA occlusion . Methods — Twenty-four nonacute ischemic stroke patients who had MABP readings > 100 mm Hg and moderate to severe ICA stenosis or occlusion were r and omized to receive perindopril 4 mg daily or placebo for 14 days . MABP , ICA flow , and both middle cerebral artery ( MCA ) velocity and resistance index were measured before dose , at 5 time points over the subsequent 24 hours , and finally at 2 weeks . Brain hexamethyl propylene amine oxide single photon emission computed tomography scans were performed before drug administration and at time of peak drug effect ( 6 to 8 hours ) after the first dose . Glomerular filtration rate was measured with 51Cr EDTA before medication and at 14 days . Results — A placebo-corrected BP fall of 17/10 mm Hg was seen ( P = 0.017 ) , which was maximal at 5.5 hours . No significant change in ICA flow or MCA velocity was seen between groups . No significant change in hemispheric CBF was seen . The mean change from baseline in the treated group was −0.79 mL · 100 g−1 · min−1 ( 95 % confidence interval [ CI ] , 1.65 to −3.23 ) ; mean change in the placebo group was −1.9 mL · 100 g−1 · min−1 ( 95%CI , 3.02 to −6.92 ) . Peri-infa rct CBF was similarly unaffected . One of the treated patients developed transient acute renal impairment and was withdrawn from the study on day 4 . Conclusions — Perindopril lowers BP without lowering CBF in hypertensive stroke patients with moderate to severe ICA stenosis or occlusion ; monitoring of this patient population for the complications of renal artery stenosis should be considered Abstract Purpose : The aim of the study was to compare effect of perindopril ( 4 mg once a day ) versus acebutolol ( 400 mg once a day ) on cerebral hemodynamics in hypertensive patients . Methods : Thirty untreated patients with mild-to-mode-rate hypertension were studied . Drug influences on Doppler-derived parameters from the cerebral blood flow ( CBF ) velocity wave form were evaluated in a r and omized , double blind , cross-over , placebo controlled study . The mean CBF velocity , pulsatility index ( PI ) , cerebrovascular resistance and index of CBF were calculated from concomitant transcranial Doppler measurements and systemic blood pressure . Results : Acebutolol and perindopril significantly decreased systolic , diastolic and mean blood pressure in relation to placebo . The mean value of CBF velocity increased to a comparable level after both drugs ( 54.9 ± 9.1 cm/s on placebo vs 62.8 ± 14.5 cm/s on perindopril p < 0.01 and 61.4 ± 9.2 cm/s on acebutolol , p < 0.01 ) . Also , the cerebrovascular resistance index decreased similarly after both drugs ( 2.26 ± 0.35 on placebo vs 1.68 ± 0.42 on perindopril p < 0.01 and 1.7 ± 0.36 on acebutolol p < 0.01 ) . The calculated CBF index increased significantly after each drug ( 25.23 ± 7.99 on placebo vs 33.98 ± 11.23 p < 0.01 on perindopril and 30.90 ± 8.04 on acebutolol p < 0.01 ) . However , perindopril augmented the CBF index more effectively than acebutolol ( p < 0.05 ) . Conclusions : Among patients with mild-to-moderate hypertension  both acebutolol and perindopril beneficially decreased cerebrovascular resistance and increased the CBF index in comparison with placebo . The increase of CBF index was greater after perindopril than acebutolol , which suggests a more significant improvement in cerebral perfusion by perindopril . The non-invasive transcranial Doppler ultrasonography method of CBF velocity measurement may contribute to choosing optimal antihypertensive therapies and to monitor their effect OBJECTIVE To determine if previously hypertensive patients with acute ischemic stroke should be treated with antihypertensive medication in the immediate poststroke period . DESIGN R and omized double-blind , placebo-controlled trial . SETTING Sixteen consecutive hypertensive patients ( four men and 12 women ; mean age , 66 years [ age range , 46 to 83 years ] ) with middle cerebral artery infa rct ion within 72 hours of onset and blood pressure between 170 and 220 mm Hg(systolic ) and 95 and 120 mm Hg ( diastolic ) . INTERVENTION Placebo ( n = 6 ) , nicardipine hydrochloride ( 20 mg [ n = 5 ] ) , captopril ( 12.5 mg [ n = 3 ] ) , or clonidine hydrochloride ( 0.1 mg [ n = 2 ] ) given every 8 hours for 3 days . MAIN OUTCOME MEASURES Decline in blood pressure , change in cerebral blood flow as measured by single photon emission computed tomography , and clinical change as determined by the National Institutes of Health Stroke Scale . RESULTS Blood pressure fell significantly in both the drug-treated group as a whole and in those patients receiving placebo ( P < .001 ) . There was no difference in blood pressure levels between these two groups throughout the study period . Patients receiving nicardipine had a consistently lower pressure than the other groups . A significant negative relationship was noted between the maximum blood pressure fall and improvement in cerebral blood flow . There were four patients whose blood pressure dropped by more than 16 % of the baseline value on any 24 hours in the first 3 days . All either failed to increase or actually decreased their cerebral blood flow to the affected area . Three of these patients were treated with nicardipine . There was no significant difference in clinical course between the placebo- and drug-treated groups as a whole . CONCLUSIONS Hypertensive ischemic stroke patients with a moderate elevation of blood pressure in the first few days may not require antihypertensive therapy . Nicardipine and possibly other calcium channel blockers may cause an excessive fall in blood pressure and impair cerebral blood flow in these patients and should therefore be used with caution Background and Purpose — Angiotensin-converting enzyme ( ACE ) inhibitor – based therapy reduces the recurrence of stroke . The present study assessed the effects of long-term ACE inhibitor therapy on cerebral circulation in patients with previous minor stroke . Methods — After a run-in period , 19 patients were r and omized to ACE inhibitor therapy ( n=9 ; 4 mg of perindopril daily ; mean age , 64±8 years ; mean systolic/diastolic blood pressure [BP]±SD , 133±12/77±9 mm Hg ) or placebo therapy ( n=10 ; mean age , 66±9 years ; mean BP , 139±10/78±8 mm Hg ) . Cerebral blood flow ( CBF ) was measured during hypercapnia , normocapnia , and hypocapnia using a positron emission tomography with H215O at entry into the study and after 3 to 12 months . Cerebral perfusion reserve ( CPR ) was defined as percent CBF response to a 1 mm Hg change in arterial partial pressure of CO2 between hypercapnia and hypocapnia . Results — Systolic/diastolic BP and CBF during normocapnia showed no significant changes between entry and completion of the trial in the perindopril and placebo groups . Mean value of CPR showed a significant increase in the perindopril group ( from 3.7±1.7%/mm Hg to 4.8±1.7%/mm Hg ; P < 0.05 ) but not in the placebo group ( from 4.1±0.8%/mm Hg to 4.2±0.6%/mm Hg ; NS ) . Statistical parametric mapping analysis also showed global and significant increase ( P < 0.01 , uncorrected ) in CPR in the perindopril group alone . Conclusions — Long-term ACE inhibitor – based therapy had a beneficial effect on the cerebral circulation by improving CPR in patients with previous minor stroke Objectives : Prevalence studies of the association between blood pressure and headache have shown conflicting results . The aim was to analyse the relation between blood pressure and risk of headache in a prospect i ve study . Methods : A total of 22 685 adults not likely to have headache , had their baseline blood pressure measured in 1984–6 , and responded to a headache question naire at follow up 11 years later ( 1995–7 ) . The relative risk of headache ( migraine or non-migrainous headache ) was estimated in relation to blood pressure at baseline . Results : Those with a systolic blood pressure of 150 mm Hg or higher had 30 % lower risk ( risk ratio (RR)=0.7 , 95 % CI 0.6–0.8 ) of having non-migrainous headache at follow up compared with those with systolic pressure lower than 140 mm Hg . For diastolic blood pressure , the risk of non-migrainous headache decreased with increasing values , and these findings were similar for both sexes , and were not influenced by use of antihypertensive medication . For migraine , there was no clear association with blood pressure . Conclusion : In the first prospect i ve study of blood pressure and the risk of headache , high systolic and diastolic pressures were associated with reduced risk of non-migrainous headache . One possible explanation may be the phenomenon of hypertension associated hypalgesia , which probably involves the baroreflex system influencing nociception in the brain stem or spinal cord The effects of angiotensin II receptor blockers on cerebral hemodynamics in humans have not been well eluci date d. The present study evaluated the effects of losartan on cerebral hemodynamics in hypertensive patients using positron emission tomography . Ten patients with essential hypertension ( mean age , 60.8 years ) were examined . In each patient , regional cerebral blood flow was measured by [ O-15 ] labeled water positron emission tomography before and after the oral administration of losartan for 8 to 23 weeks . In 8 patients , the baseline regional cerebral blood flow measurement was followed by 1,000 mg of acetazolamide challenge to measure the cerebral perfusion reserve . Systemic blood pressures before and after treatment were 153.8±10.8/96.0±6.5 mmHg ( systolic mean±SD/diastolic mean±SD ) and 133.4±11.2/83.6±6.5 mmHg , respectively ; this difference was significant . The baseline global cerebral blood flow values before and after treatment were 38.4±6.9 ml/min/100 g and 38.2±8.2 ml/min/100 g , respectively ; this difference was not significant . The results of the global cerebral blood flow response to the acetazolamide challenges were not statistically different before and after treatment . A regional analysis showed no statistical difference in regional cerebral blood flow or cerebral perfusion reserve throughout the brain before and after treatment . Losartan 's effect on reducing the blood pressure did not affect either the baseline regional cerebral blood flow or the cerebral perfusion reserve in patients with mild to moderate hypertension . The inclusion of losartan in anti-hypertensive regimens could be advantageous for cerebral circulation in patients with essential hypertension We undertook a double-blind , placebo-controlled study to determine the effectiveness of verapamil hydrochloride for the prophylaxis of  migraine . Twelve patients were given either verapamil hydrochloride  , 80 mg four times daily , or placebo in r and om order during two consecutive three-month periods . Migraine frequency , severity , and duration were quantified by daily logs and monthly question naires . Ten of the 12 patients had fewer migraines during verapamil therapy . Migraine frequency decreased from 6.7 to 3.8 migraines per patient per month , for a mean decrease of 49 % . Headache unit index fell from an average of 0.61 to 0.44 . We conclude that verapamil is effective in the prophylaxis of migraine and that verapamil might be considered one alternative in the development of a regimen for the prophylaxis of migraine The aim of this study was to evaluate changes in cerebral hemodynamics in young patients with uncomplicated hypertension before and after effective antihypertensive treatment with a beta-blocker drug . Changes in mean flow velocity in the middle cerebral artery from normal condition to hypercapnia were evaluated by means of a transcranial Doppler in 42 hypertensive patients and 21 healthy subjects comparable for age and sex distribution . We obtained hypercapnia with breath-holding and evaluated cerebrovascular reactivity with the breath-holding index ( BHI ) . After a baseline evaluation ( time 0 ) , patients were r and omly assigned to a placebo ( group 1 ) or atenolol ( group 2 ) therapy . The evaluation was repeated after 30 ( time  
    Output:
    