Blood Pressure Changes During the Initial Week After Different Subtypes of Ischemic Stroke
Background and Purpose— The purpose of this study was to clarify the differences in the acute blood pressure course among different ischemic stroke subtypes.
Methods— We divided 588 consecutive patients with acute brain infarction into four clinical subgroups to study the blood pressure levels during the initial 6 hospital days.
Results— During the 6 days, systolic blood pressure of lacunar and atherothrombotic patients was higher (P=0.0001) and diastolic blood pressure of lacunar patients was higher (P=0.0371) than of patients with the other subtypes. Preexisting hypertension was associated with elevated acute systolic blood pressure in all patients and in each subtype and with elevated acute diastolic blood pressure in all patients, cardioembolic patients, and patients with stroke of other etiology. After adjustment by preexisting hypertension, diabetes mellitus with a hemoglobin A1c >7.0% was associated with elevated systolic blood pressure in all, lacunar, and cardioembolic patients and with diastolic blood pressure in all patients.
Conclusions— Blood pressure course of patients sustaining acute stroke varied widely according to stroke subtypes. Poorly controlled diabetes mellitus, as well as preexisting hypertension, appeared to influence blood pressure during the initial week of stroke.
Whether to lower elevated blood pressure (BP) in patients with acute ischemic stroke is a matter of debate.1 BP-lowering may impair salvage of the ischemic penumbra and lead to progressive worsening. Because the extent of the penumbra appears to depend on cerebrovascular pathology, one should consider the ischemic stroke subtype when deciding on the management of acute BP. We determined the acute BP course among patients with different stroke subtypes and analyzed which baseline characteristics contribute to the course.
Patients and Methods
We registered 588 consecutive Japanese patients with a brain infarction proven on diffusion-weighted MRI who were hospitalized within 24 hours after stroke onset between January 2001 and December 2004 and did not die within a week. Based on neurologic, radiologic, cardiologic, and hematologic profiles, but without information of acute BP course, the stroke subtype was determined by a consensus of stroke neurologists according to the TOAST subtype classification system2: lacune, large-artery atherothrombosis, cardioembolism, and stroke of other determined and undetermined etiology.
Preexisting hypertension was defined as systolic BP (SBP) ≥140 mm Hg, diastolic BP (DBP) ≥90 mm Hg before the stroke, or a history of antihypertensive medication. Underlying risk factors and comorbidities, including poorly controlled diabetes mellitus (hemoglobin A1c on admission ≥7.0%) and renal insufficiency (serum creatinine ≥1.3 mg/dL) were examined.
The following six BP values were used for analysis: BP on admission, the mean of at least two measurements between 6 and 12 hours, between 12 and 24 hours, and between 24 and 36 hours after admission; the mean of the morning BP on the third and fourth hospital days, and that on the fifth and sixth hospital days. BP was measured by trained nurses after the patients had rested in a supine position with a mercury sphygmomanometer; the average of two consecutive measurements was used for analysis. Antihypertensive agents were given intravenously for patients sustaining acute stroke with an extremely high BP according to the guidelines1; nicardipine, diltiazem, or nitroglycerine was primarily used.
Comparisons among groups with different stroke subtypes were performed using χ2, Kruskal-Wallis test, one-way repeated-measures and factorial analysis of variance (ANOVA) with Fisher post hoc analysis, and two-way repeated-measures ANOVA with Fisher analysis as appropriate. A probability value <0.05 was considered to be significant.
Preexistent hypertension was most often found in lacunar patients followed by atherothrombotic patients (P<0.0001, Table). There were significant differences among the four groups in age, frequencies of diabetes mellitus, poorly controlled diabetes mellitus, hypercholesterolemia, atrial fibrillation, and ischemic heart disease; the National Institutes of Health Stroke Scale score on admission; and infarct location.
On admission, SBP of cardioembolic patients was lower than that of lacunar (P<0.0001) and atherothrombotic (P=0.0031) patients, whereas DBP did not differ among the four groups. Both SBP and DBP decreased during the initial 6 days in all patients regardless of subtype (P<0.0001 for each, Figure). ANOVA shows a group×time interaction for SBP (P=0.0001) with intergroup differences between patients with lacune and cardioembolism (P=0.0005), lacune and stroke of other etiology (P=0.0263), atherothrombosis and cardioembolism (P=0.0002), and atherothrombosis and stroke of other etiology (P=0.0088). ANOVA also shows an interaction for DBP (P=0.0371) with intergroup differences between lacunar patients and patients with atherothrombosis (P=0.0466), cardioembolism (P=0.0086), and stroke of other etiology (P=0.0346).
Cardioembolic patients were most often given intravenous antihypertensives during the acute phase as a result of a very high acute BP or special reasons, including thrombolysis and congestive heart failure (P<0.0001, Table). Cardioembolic patients were also most often given antihypertensives or coronary vasodilators (intravenously, orally, or transdermally, P=0.0079). Peroral agents were principally the same with those used before the stroke onset. Patients who received antihypertensive therapy still had higher SBP and DBP values throughout 6 days than those without antihypertensive therapy (P<0.0001 for each).
In all patients and in patients of each stroke subtype, preexisting hypertension was found to be significantly associated with the acute SBP course (P=0.0051 for atherothrombosis and P<0.0001 for others). After adjusting for preexisting hypertension, diabetes mellitus (P=0.0074), poorly controlled diabetes mellitus (P=0.0003), and renal insufficiency (P=0.0497) affected SBP of all patients; poorly controlled diabetes mellitus affected SBP of lacunar (P=0.0344) and cardioembolic patients (P=0.0159); atrial fibrillation inversely affected SBP of lacunar patients (P=0.0384); and smoking inversely affected SBP of cardioembolic patients (P=0.0115). Preexisting hypertension was significantly associated with the 6-day DBP course in all patients, cardioembolic patients, and patients with stroke of other etiology (P<0.0001 for each). After adjustment for preexisting hypertension, poorly controlled diabetes mellitus positively affected (P=0.0215) and advanced age (P=0.0041) and ischemic heart disease (P=0.0467) inversely affected DBP of all patients; a high National Institutes of Health Stroke Scale score affected DBP of cardioembolic patients (P=0.0478); and advanced age inversely affected DBP of patients sustaining a stroke of other etiology (P=0.0142).
Based on a relatively small patient population, lacunar patients have been previously reported to have higher admission BP than patients with other subtypes3,4; however, during 24 hours after admission, this difference disappeared.4 The reasons that high acute BP was found in our lacunar and atherothrombotic patients could be a high frequency of preexisting hypertension and low frequency of acute antihypertensive therapy in these patients.
Poorly controlled diabetes mellitus was associated with acute high BP in all stroke patients as well as in lacune and cardioembolism. Compensation for impaired endothelium-dependent vasodilation and cerebrovascular reserve resulting from chronic diabetes may account for acute high BP in diabetic patients.5,6 In all patients in this study, renal insufficiency was positively associated with acute SBP, and advanced age and ischemic heart disease were negatively associated with acute DBP. Hypertension seen in renal patients is predominantly systolic. Age-related increases in aortic stiffness and pulse wave velocity might result in an increase in pulse pressure and decrease in DBP.
Encouraged by the success of the ACCESS study,7 several studies dealing with antihypertensive therapy for acute ischemic stroke are ongoing, including COSSACS, CHHIPS, ENOS, and SCAST. Based on the present results, lacunar and atherothrombotic patients have a high chance of being included in such studies. Because lacune does not have a large ischemic penumbra, a high acute BP does not appear to be necessary to maintain cerebral perfusion. As well, the coexistence of preexisting hypertension and poorly controlled diabetes mellitus, both of which appeared to be associated with high acute BP of lacunar patients, synergistically increases the risk of brain and cardiovascular damage.6 Angiotensin type 1 receptor blockers given for acute stroke might be protective against such organ damage.7
In conclusion, during the initial 6 days of hospitalization, compared with the patients with the other stroke subtypes, lacunar and atherothrombotic patients had higher SBP, and lacunar patients had higher DBP. Preexisting hypertension and poorly controlled diabetes mellitus were associated with the acute SBP and DBP courses.
We thank Drs Kotaro Yasumori and Tooru Inoue for their valuable advice and Rie Tominaga and Terumi Hara for their technical assistance.
Sources of Funding
This study was partially supported by the Research Grant for Cardiovascular Diseases (15C-1) from the Japanese Ministry of Health, Labor and Welfare and the Mitsubishi Pharma Research Foundation.
- Received July 19, 2006.
- Accepted July 25, 2006.
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