Plasma lipids and lipoproteins in subtypes of stroke Lindgren A, Nilsson-Ehle P, Norrving B, Johansson BB. Plasma lipids and lipoproteins in subtypes of stroke. Acta Neurol Scand 1992: 86: 572-578. 0 Munksgaard 1992.
I
We determined plasma lipid and lipoprotein concentrations in 131 patients (95 males, 36 females, mean age 71 years) 6 months after acute stroke onset. Compared to a reference population, the alterations of plasma lipid concentrations in stroke patients were moderate. However, the stroke patients had higher levels of triglyceride and lipoprotein (a) and lower concentrations of cholesterol, high density lipoprotein cholesterol and low density lipoprotein cholesterol. Patients with different subtypes of stroke showed significant differences when compared with each other by analysis of covariance (with adjustment for age, sex, smoking, hypertension and diabetes). Patients with carotid or vertebral artery disease had the higher levels of cholesterol, triglyceride and apolipoprotein B, whereas high density lipoprotein triglyceride concentrations were higher in patients with cardioembolic infarcts.
Whereas hypercholesterolemia is recognized as a major risk factor for coronary heart disease (1-3), the relationship between plasma lipoprotein disorders and stroke has not been firmly established (2, 4, 5). However, stroke is a heterogeneous condition of different etiologic origins; it is therefore possible that plasma lipid abnorkalities may be of importance for some subtype(s) of stroke, but not for others. Earlier studies, performed mainly in younger patients, indicate that lipoprotein alterations may occur specifically in some subtypes of stroke (e.g. 6, 7), but a more comprehensive comparison of the various stroke subgroups encountered in clinical practice is lacking. We therefore determined plasma lipid and lipoprotein concentrations in 131 stroke patients, collected during a one year period. Blood samples were taken approximately 6 months after the acute stroke event, to eliminate the transient influence of the acute phase on plasma lipids (8, 9). In addition to the more traditional lipid analyses, e.g. cholesterol and triglyceride, we evaluated the possible additional information of several lipoprotein components and apolipoproteins. Patients and methods
One hundred and thirty-one patients (95 men and 36 women, age 38 to 90 years, mean 71 years, SD 10, median age 73 years), were included in the study approximately 6 months after they had suffered from an acute stroke. They were all living in the local 512
A. Lindgren I , P. Nilsson-Ehle2, B. Norrving B. B. Johansson
’
’
Departments of Neurology, Clinical Chemistry, University Hospital, Lund, Sweden
Key words: lipoproteins; cholesterol; triglyceride; stroke; subtypes Arne Lindgren. Department of Neurology. University Hospital, S-221 85 Lund, Sweden Accepted for publication June 22, 1992
catchment area of Lund University Hospital, Sweden, and admitted with acute stroke between September 1st 1987 and August 31st 1988. The inclusion criteria were: acute stroke in all ages; no new episode of stroke before the blood sample, as described below was taken; no acute illness or stress when the blood sample was taken. We did not include patients with subarachnoidal bleeding or uncommon stroke subtypes and patients unable to come to the hospital for the blood sample examination (generally due to high age and severe handicap). All patients were examined in the acute phase by an experienced neurologist and classified into 5 subgroups of different etiology, according to the following criteria: 1) Intracerebral haemorrhage: diagnosed by CT scan of the brain. 2) Embolic stroke presumably due to cardiac embolisation (cardioembolic infarction): patients with signs of an acute ischemic stroke and a heart disease such as electrocardiography verified atrial fibrillation, myocardial infarction within the last 2 weeks before the acute stroke, mitral valve disease, ventricular aneurysm or other echocardiographic findings of a probable embolic source. 3) Lacunar infarction: patients with one of the following syndromes: pure motor stroke, pure sensory stroke, clumsy hand-dysarthria, or ataxic hemiparesis. 4) Ischemic stroke due to stenosis or occlusion of the internal carotid or vertebral arteries, (precerebral artery disease): diagnosed by angiography or
Lipoproteins in subtypes of stroke continuous-wave doppler examination and clinical findings coherent with the abnormalities found in these examinations. 5) Cerebral infarction of undetermined cause. CT-scan of the brain was performed in the majority of the cases (Table 1). Angiography or continuous wave doppler examinations of carotid and vertebral arteries were performed when clinically indicated at the discretion of the case physician. Data on smoking habits, hypertension and diabetes mellitus were collected by means of a questionnaire which was completed by the patients or their relatives. 159 healthy individuals (87 men and 72 women, age 40-80 years, 4 individuals from each age cohort), not taking any drugs, were examined for plasma cholesterol, plasma triglyceride, high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) cholesterol, as described earlier (10) and served as reference group. Although the mean age of this group is somewhat lower than that of the patient group, we consider the reference subjects as representative for comparison with the patients, since there were no significant age variations of plasma lipids or plasma lipoproteins among the reference group. As lipoprotein (a) (Lp(a)) concentrations had not been examined in this reference group, the Lp(a) values of the patients were instead compared with another reference group of 52 persons without cardiovascular disease, described earlier (1 1). Chemical analyses
Approximately 6 nfonths (183-227 days, mean 214 days) after the acute stroke, a venous blood sample was taken from the patients in the morning after 10 hours fasting. The patients had taken their morning medications as usual. They had abstained from excess intake of alcohol one week before the examination. The blood samples were taken in evacuated tubes, containing K,EDTA (4 mmol/l blood) as anticoagulant. After centrifugation, plasma samples
Table 1. Number of patients with CT-scan of the brain. CT/total lntracerebral haemorrhage Cardioembolic infraction Lacunar infarction Precerebral artery disease Infarction of undetermied cause
12/12 24/33 36/41 9/10 28/35 109/131
were stored at - 70°C until analysis. Plasma cholesterol and plasma triglyceride were analyzed with enzymatic methods using reagents from Boehringer Mannheim GmbH. HDL components were measured after precipitation of very low density lipoprotein and LDL with dextran sulfate and magnesium chloride, as described earlier (12). HDL cholesterol and HDL triglyceride (HDL TG) were measured with enzymatic methods from Boehringer Mannheim, HDL phospholipid (HDL PL) was measured with an enzymatic technique from Waco, Tokyo, Japan. LDL cholesterol was calculated as described by Friedewald et al. (13): LDL cholesterol = plasma cholesterol - HDL cholesterol - 0.45”plasma triglyceride. Apolipoproteins A1 (Apo AI) and B (ApoB) were measured with electroimmunoassays ( 14),using antisera from Dacopatts, Copenhagen, Denmark and Atlantic Antibodies, Scaresbury, Maine respectively. Lp(a) was measured with a radioimmunoassay kit from Pharmacia, Uppsala, Sweden. Statistics
The Department of Statistics, University of Lund processed the data, using Biomedical Data Processing statistical software (15) on a Sirius Vax computer from Digital Equipment Corporation. Data are given as mean standard deviation for the lipid and lipoprotein concentrations, except for Lp(a) which is not uniformly distributed (16), where median and values of 25th and 75th percentiles are given. Z-test was performed to compare the stroke patients as a group with the reference group, except for Lp(a) where Mann-Whitney U-test was used. P-values < 0.05 were considered significant. The same tests were used to compare the individual subgroups with the reference group. The means of the subgroups were adjusted for possible influence of hypertension, diabetes, smoking, age and sex. The equality of the adjusted means of the subgroups was then tested with one way analysis of covariance. If a significant (p70 years) patients in the stroke group as a whole, and in the stroke subgroups. The study was approved of by the Ethic’s Committee of the University of Lund.
573
Lindgren et al. ApoAI, HDL PL and Lp(a). The group with precerebral artery disease had the highest means for cholesterol, triglyceride and ApoB (Table 3). These adjusted mean concentrations of cholesterol, triglyceride and ApoB that were highest in the group of patients with precerebral artery disease were compared with the other individual stroke subtypes with T-test and there was a significant difference when compared with intracerebral haemorrhage (p = 0.006), cardioembolic infarction (p = 0.008) and infarction of undetermined cause (p = 0.009) (but not for lacunar infarction) for cholesterol; but only for infarction of undetermined cause for triglyceride (p = 0.001) and ApoB (p = 0.006). However, there was a significant difference in adjusted mean concentrations for cholesterol (p = 0.004), triglyceride (p = 0.001) and ApoB (p = 0.002) when a contrast T-test was performed to compare the group with precerebral artery disease with the other stroke subgroups, taken together. HDL T G mean values were highest in cardioembolic infarction. This was confirmed with contrast T-test (p = 0.0001). When compared with other individual stroke groups, patients with cardioembolic infarction had significantly higher HDL T G concentrations than patients with lacunar infarction and infarction of undetermined cause (p < 0.005, p < 0.001 respectively), but no significant difference was seen when compared with intracerebral haemorrhage (p = 0.01) and precerebral artery disease (p = 0.08). In order to demonstrate a possible age difference, patients were divided into a “younger group” (
I
We determined plasma lipid and lipoprotein concentrations in 131 patients (95 males, 36 females, mean age 71 years) 6 months after acute stroke onset. Compared to a reference population, the alterations of plasma lipid concentrations in stroke patients were moderate. However, the stroke patients had higher levels of triglyceride and lipoprotein (a) and lower concentrations of cholesterol, high density lipoprotein cholesterol and low density lipoprotein cholesterol. Patients with different subtypes of stroke showed significant differences when compared with each other by analysis of covariance (with adjustment for age, sex, smoking, hypertension and diabetes). Patients with carotid or vertebral artery disease had the higher levels of cholesterol, triglyceride and apolipoprotein B, whereas high density lipoprotein triglyceride concentrations were higher in patients with cardioembolic infarcts.
Whereas hypercholesterolemia is recognized as a major risk factor for coronary heart disease (1-3), the relationship between plasma lipoprotein disorders and stroke has not been firmly established (2, 4, 5). However, stroke is a heterogeneous condition of different etiologic origins; it is therefore possible that plasma lipid abnorkalities may be of importance for some subtype(s) of stroke, but not for others. Earlier studies, performed mainly in younger patients, indicate that lipoprotein alterations may occur specifically in some subtypes of stroke (e.g. 6, 7), but a more comprehensive comparison of the various stroke subgroups encountered in clinical practice is lacking. We therefore determined plasma lipid and lipoprotein concentrations in 131 stroke patients, collected during a one year period. Blood samples were taken approximately 6 months after the acute stroke event, to eliminate the transient influence of the acute phase on plasma lipids (8, 9). In addition to the more traditional lipid analyses, e.g. cholesterol and triglyceride, we evaluated the possible additional information of several lipoprotein components and apolipoproteins. Patients and methods
One hundred and thirty-one patients (95 men and 36 women, age 38 to 90 years, mean 71 years, SD 10, median age 73 years), were included in the study approximately 6 months after they had suffered from an acute stroke. They were all living in the local 512
A. Lindgren I , P. Nilsson-Ehle2, B. Norrving B. B. Johansson
’
’
Departments of Neurology, Clinical Chemistry, University Hospital, Lund, Sweden
Key words: lipoproteins; cholesterol; triglyceride; stroke; subtypes Arne Lindgren. Department of Neurology. University Hospital, S-221 85 Lund, Sweden Accepted for publication June 22, 1992
catchment area of Lund University Hospital, Sweden, and admitted with acute stroke between September 1st 1987 and August 31st 1988. The inclusion criteria were: acute stroke in all ages; no new episode of stroke before the blood sample, as described below was taken; no acute illness or stress when the blood sample was taken. We did not include patients with subarachnoidal bleeding or uncommon stroke subtypes and patients unable to come to the hospital for the blood sample examination (generally due to high age and severe handicap). All patients were examined in the acute phase by an experienced neurologist and classified into 5 subgroups of different etiology, according to the following criteria: 1) Intracerebral haemorrhage: diagnosed by CT scan of the brain. 2) Embolic stroke presumably due to cardiac embolisation (cardioembolic infarction): patients with signs of an acute ischemic stroke and a heart disease such as electrocardiography verified atrial fibrillation, myocardial infarction within the last 2 weeks before the acute stroke, mitral valve disease, ventricular aneurysm or other echocardiographic findings of a probable embolic source. 3) Lacunar infarction: patients with one of the following syndromes: pure motor stroke, pure sensory stroke, clumsy hand-dysarthria, or ataxic hemiparesis. 4) Ischemic stroke due to stenosis or occlusion of the internal carotid or vertebral arteries, (precerebral artery disease): diagnosed by angiography or
Lipoproteins in subtypes of stroke continuous-wave doppler examination and clinical findings coherent with the abnormalities found in these examinations. 5) Cerebral infarction of undetermined cause. CT-scan of the brain was performed in the majority of the cases (Table 1). Angiography or continuous wave doppler examinations of carotid and vertebral arteries were performed when clinically indicated at the discretion of the case physician. Data on smoking habits, hypertension and diabetes mellitus were collected by means of a questionnaire which was completed by the patients or their relatives. 159 healthy individuals (87 men and 72 women, age 40-80 years, 4 individuals from each age cohort), not taking any drugs, were examined for plasma cholesterol, plasma triglyceride, high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) cholesterol, as described earlier (10) and served as reference group. Although the mean age of this group is somewhat lower than that of the patient group, we consider the reference subjects as representative for comparison with the patients, since there were no significant age variations of plasma lipids or plasma lipoproteins among the reference group. As lipoprotein (a) (Lp(a)) concentrations had not been examined in this reference group, the Lp(a) values of the patients were instead compared with another reference group of 52 persons without cardiovascular disease, described earlier (1 1). Chemical analyses
Approximately 6 nfonths (183-227 days, mean 214 days) after the acute stroke, a venous blood sample was taken from the patients in the morning after 10 hours fasting. The patients had taken their morning medications as usual. They had abstained from excess intake of alcohol one week before the examination. The blood samples were taken in evacuated tubes, containing K,EDTA (4 mmol/l blood) as anticoagulant. After centrifugation, plasma samples
Table 1. Number of patients with CT-scan of the brain. CT/total lntracerebral haemorrhage Cardioembolic infraction Lacunar infarction Precerebral artery disease Infarction of undetermied cause
12/12 24/33 36/41 9/10 28/35 109/131
were stored at - 70°C until analysis. Plasma cholesterol and plasma triglyceride were analyzed with enzymatic methods using reagents from Boehringer Mannheim GmbH. HDL components were measured after precipitation of very low density lipoprotein and LDL with dextran sulfate and magnesium chloride, as described earlier (12). HDL cholesterol and HDL triglyceride (HDL TG) were measured with enzymatic methods from Boehringer Mannheim, HDL phospholipid (HDL PL) was measured with an enzymatic technique from Waco, Tokyo, Japan. LDL cholesterol was calculated as described by Friedewald et al. (13): LDL cholesterol = plasma cholesterol - HDL cholesterol - 0.45”plasma triglyceride. Apolipoproteins A1 (Apo AI) and B (ApoB) were measured with electroimmunoassays ( 14),using antisera from Dacopatts, Copenhagen, Denmark and Atlantic Antibodies, Scaresbury, Maine respectively. Lp(a) was measured with a radioimmunoassay kit from Pharmacia, Uppsala, Sweden. Statistics
The Department of Statistics, University of Lund processed the data, using Biomedical Data Processing statistical software (15) on a Sirius Vax computer from Digital Equipment Corporation. Data are given as mean standard deviation for the lipid and lipoprotein concentrations, except for Lp(a) which is not uniformly distributed (16), where median and values of 25th and 75th percentiles are given. Z-test was performed to compare the stroke patients as a group with the reference group, except for Lp(a) where Mann-Whitney U-test was used. P-values < 0.05 were considered significant. The same tests were used to compare the individual subgroups with the reference group. The means of the subgroups were adjusted for possible influence of hypertension, diabetes, smoking, age and sex. The equality of the adjusted means of the subgroups was then tested with one way analysis of covariance. If a significant (p70 years) patients in the stroke group as a whole, and in the stroke subgroups. The study was approved of by the Ethic’s Committee of the University of Lund.
573
Lindgren et al. ApoAI, HDL PL and Lp(a). The group with precerebral artery disease had the highest means for cholesterol, triglyceride and ApoB (Table 3). These adjusted mean concentrations of cholesterol, triglyceride and ApoB that were highest in the group of patients with precerebral artery disease were compared with the other individual stroke subtypes with T-test and there was a significant difference when compared with intracerebral haemorrhage (p = 0.006), cardioembolic infarction (p = 0.008) and infarction of undetermined cause (p = 0.009) (but not for lacunar infarction) for cholesterol; but only for infarction of undetermined cause for triglyceride (p = 0.001) and ApoB (p = 0.006). However, there was a significant difference in adjusted mean concentrations for cholesterol (p = 0.004), triglyceride (p = 0.001) and ApoB (p = 0.002) when a contrast T-test was performed to compare the group with precerebral artery disease with the other stroke subgroups, taken together. HDL T G mean values were highest in cardioembolic infarction. This was confirmed with contrast T-test (p = 0.0001). When compared with other individual stroke groups, patients with cardioembolic infarction had significantly higher HDL T G concentrations than patients with lacunar infarction and infarction of undetermined cause (p < 0.005, p < 0.001 respectively), but no significant difference was seen when compared with intracerebral haemorrhage (p = 0.01) and precerebral artery disease (p = 0.08). In order to demonstrate a possible age difference, patients were divided into a “younger group” (
