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Increased plasma levels of B-type natriuretic peptide in patients with unstable angina
Increased plasma levels of B-type natriuretic peptide in patients with unstable angina Koichi K i k u t a , MD, a H i r o f u m i Yasue, MD, a Michihiro Y o s h i m u r a , MD, a E t s u o Morita, MD, a H i t o s h i S u m i d a , MD, a Hideji Kato, MD, a K i y o t a k a K u g i y a m a , MD, a H i s a o Ogawa, MD, a K e n O k u m u r a , MD, a Yoshihiro Ogawa, MD, b a n d K a z u w a N a k a o , MD b Kumamoto
and Kyoto, Japan
This study was designed to examine the plasma levels of Btype or brain natriuretic peptide (BNP), as well as A-type or atrial natriuretic peptide (ANP) in patients with unstable angina as compared with those in patients with stable exertional angina and control subjects. We measured the plasma levels of BNP and ANP in 33 patients with unstable angina, 20 patients with stable exertional angina, and 20 control subjects. The plasma levels of BNP were significantly increased in patients with unstable angina compared with those in patients with stable exertional angina and control subjects, respectively (39.5 ± 29.4 pg/ml vs 15.1 ± 8.0 pg/ ml; ,o<0.01 and 39.5 ±29.4 pg/ml vs 10.3 ± 6 . 4 pg/ml; p < 0.01, respectively). On the other hand, there was no significant difference in the plasma levels of ANP among the three groups. Furthermore, in patients with unstable angina, the plasma levels of BNP decreased significantly after the medical treatment (from 39.5 ± 29.4 pg/ml to 15.8 ~ 11.0 pg/ ml; p< 0.01), whereas the plasma levels of ANP did not change. We conclude that the plasma levels of BNP are increased in the majority of patients with unstable angina and that the increased levels decrease toward normal after treatment. (Am Heart J 1996;132:101-7.)
B-type or b r a i n n a t r i u r e t i c peptide (BNP) f o r m s a peptide f a m i l y w i t h A-type or atrial n a t r i u r e t i c peptide (ANP) a n d m a y be involved in the r e g u l a t i o n of blood p r e s s u r e a n d fluid volumes. 1-3 We d e m o n s t r a t e d t h a t B N P is a novel cardiac h o r m o n e secreted p r e d o m i n a n t l y f r o m the ventricle, a n d its p l a s m a levels a r e m a r k e d l y i n c r e a s e d in p a t i e n t s w i t h chronic congestive h e a r t failure. 4-6 T h e p l a s m a levels of B N P w e r e m a r k e d l y increased, w h e r e a s the
From the aDivision of Cardiology, Kumamoto University School of Medicine, and the bSecond Division, bDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine. Supported in part by a grant from the Ministry of Education and Culture (04263104) and a grant from the Smoking Research Foundation. Received for publication May 22, 1995; accepted Nov. 27, 1995. Reprint requests: Hirofumi Yasue, MD, Division of Cardiology, Kumamoto UNiversity School of Medicine, Honjo 1-1-1, Kumamoto 860, Japan. Copyright © 1996 by Mosby-Year Book, Inc. 0002-8703/96/$5.00 + 0 4/1/72010
p l a s m a levels of A N P w e r e only mildly i n c r e a s e d in p a t i e n t s w i t h acute m y o c a r d i a l infarction. 7, 8 U n s t a b l e a n g i n a is i n t e r m e d i a t e in s e v e r i t y bet w e e n acute m y o c a r d i a l infarction a n d chronic stable a n g i n a a n d m a y h e r a l d acute m y o c a r d i a l infarction. 9-12 However, t h e p l a s m a levels of B N P a r e not k n o w n in p a t i e n t s w i t h u n s t a b l e angina. I n our study, we e x a m i n e d t h e p l a s m a levels of B N P a n d A N P in p a t i e n t s w i t h u n s t a b l e a n g i n a as c o m p a r e d w i t h those in p a t i e n t s w i t h stable exertional a n g i n a a n d control subjects. METHODS Patients. We studied 73 patients (49 men and 24 women,
mean age 60 _+ 8 years; range, 44 to 75 years). They consisted of three groups: unstable angina group, stable exertional angina group, and Control group. The unstable angina group consisted of 33 patients with unstable angina. Unstable angina was defined as an accelerating pattern of chest pain (recent increase in severity or frequency or both), lasting ->15 minutes on at least one occasion or occurring at rest or during minimal activity. Of the 33 patients with unstable angina, 16 had ST-segment elevation and 17 had ST-segment depression on the electrocardiogram (ECG) during the chest pain. There was no evidence of acute myocardial infarction, as documented by the absence of QRS change on the ECG and the absence of an elevation of serial serum creatine kinase MB isoenzyme levels greater than twice the upper limit of normals. Those from whom blood sampling for ANP and BNP could not be done within 24 hours after the last attack were excluded from this study. The stable exertional angina group consisted of 20 patients who had typical exertional angina associated with horizontal or downsloping ST-segment depression of >1.0 m m on an exercise test. The control group consisted of 20 patients with atypical chest pain who underwent coronary angiography and who were negative for myocardial ischemia on a treadmill exercise test and a hyperventilation test. Patients with previous myocardial infarction were excluded from this study because the plasma levels of BNP 101
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Table I. Characteristics of the study groups Control
Stable exertional angina
No. of patients 20 20 Age (yr) Mean +- SD 60 _+7 62 _+8 Range 44-72 46-74 Male/female ratio 12/8 14/6 Blood pressure 7 9 ->150/90 mra Hg (n) No. diseased vessels (>75% stenosis)* 0 vessel (n) 20 0 1 vessel (n) 0 10 2 vessel (n) 0 7 3 vessel (n) 0 3
Unstable angina
33 59 -+ 8 46-75 23/10 15 5 17 4 7
*There was no significant difference in the incidence of coronary artery disease between the stable exertional angina group and the unstable angina group.
in patients with acute myocardial infarction is still much higher in the fourth week from the onset than those in the controlsS; the plasma levels of BNP in patients with old myocardial infarction remain to be clarified. Patients also were excluded if they had congestive heart failure, valvular heart disease, cardiomyepathy, left ventricular hypertrophy, or renal failure. The clinical characteristics of the three groups are described in Table I. There were no significant differences in age, sex, and the prevalence of hypertension among the three groups. The study protocol was in agreement with the guidelines established by the ethics committee at our institution. Written informed consent was obtained from each patient and his or her family. Cardiac catheterization and blood sampling. Cardiac catheterization was done in all 73 patients. All drugs except sublingual nitroglycerin and aspirin were withdrawn at least 1 day before the catheterization except in 14 patients with unstable angina, for whom antianginal drugs such as nitrates, calcium antagonists, or both were indispensable because of inability to carry on any physical activity without discomfort. In the unstable angina group, initial blood sampling for ANP and BNP were done within 24 hours after the last attack. In 22 of the unstable angina group, cardiac catheterization together with blood sampling for ANP and BNP could also be done within 24 hours after the last attack. No attack occurred during blood sampling in the patients with unstable angina. The mean time between the last episode of chest pain and initial blood sampling in those patients was 12.6 ± 9.1 hours (range, 1 to 24 hours). After initial blood sampling from the peripheral vein, hemodynamic measurements, including pulmonary capillary wedge pressure (PCWP), mean right atrial pressure (RAP), and cardiac index (CI), were performed by using a Swan-Ganz catheter inserted into the femoral vein. Cardiac index was measured by thermodilution technique in triplicate. A Sones catheter was inserted into a brachial artery, and mean aortic pressure (AOP) and left ventricular end-diastolic pressure (LVEDP) were measured. After blood sampling and the hemodynamic study, coronary an-
Journal
giography and left ventriculography were per~brmed in all patients. Left ventricular ejection fraction (LVEF) and left ventricular end-systolic volume index (LVESVI) were determined by left ventriculography. In the unstable angina group, 28 patients had significant organic coronary artery stenosis >75% of luminal diameter in the major coronary arteries, and 10 had multivessel coronary artery spasm, demonstrated by the intracoronary injection of acetylcholine. 13 Five of 10 patients with multivessel coronary spasm had 75% organic stenosis in one major coronary artery, and the remaining 5 patients had no significant organic stenosis (2 with <25% stenosis and 3 without stenosis). All patients with stable exertional angina had coronary artery stenosis >75% of luminal diameter in the major coronary arteries. All control subjects had no significant organic stenosis in their coronary arteries (14 without stenosis and 6 with <25% stenosis), and no coronary spasm was demonstrated by the intracoronary injection of acetylcholine.13 The number of diseased vessels in the three groups is summarized in Table I. There was no significant difference in the incidence of coronary artery disease between the stable exertiona] angina group and the unstable angina group. All blood samples were placed into ethylenediaminetetraacetic acid (EDTA)-coated tubes containing 1000 IU/ml aprotinine. Thereafter, the plasma immediately was centrifuged at 4 ° C and then stored at -80 ° C until analysis. Treatment of unstable angina and stable exertional angina, All patients with unstable angina received calcium antagonists, nitrates, and aspirin with varying combinations of ~-blockers (8 patients), and the doses were maximized until chest pain was considered controlled. In the unstable angina group, the second blood sampling was performed when the attacks were controlled after the medical treatment. The attacks were considered controlled if the patients had become free of attacks for >1 week or returned to the previous pattern of chronic stable angina pectoris. The mean time between the initial blood sampling and the second blood sampling was 17 _+ 7 days (range, 10 to 32 days). All patients with stable exertional angina received calcium antagonists and aspirin with various combinations of ~-blockers (9 patients) and nitrates (17 patients), and the doses were maximized until chest pain did not occur during daily activity. In the stable exertional angina group, the second blood sampling also was performed after the medical treatment. The mean time between the initial blood sampling and the second blood sampling was 16 +_ 2 days (range, 12 to 30 days). Echocardiographic examination. Echocardiograms were recorded by using Toshiba 160A (Tokyo, Japan) twodimensional echocardiographic equipment with transducers ranging in frequency from 2.25 to 3.5 MHz. A complete two-dimensional echocardiogram was recorded in S-VHS videotape. In the unstable angina group, parasternal longand short-axis, as well as apical four- and two-chamber views, were recorded at the time of initial and second blood sampling for ANP and BNP. Images at the time of initial and second blood sampling were transferred online in digital form for display as continuous-loop images in quad-
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Fig. 1. Plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) in patients with unstable angina, in those with stable exertional angina, and in control subjects. Plasma levels of BNP were significantly higher in patients with unstable angina than in those with stable exertional angina and in control subjects. There was no significant difference in plasma levels of ANP among three groups. Bars, Mean -+ SD. screen format (Freeland Systems, Prism Imaging, Louisville, Colo.). The quadscreen format was transferred onto 3.5-inch disks for analysis. The videotape was analyzed for confirmation. Echocardiographic wall motion was graded as normokinetic, hypokinetic, akinetic, or dyskinetic. Holter monitoring. Twenty-four-hour Holter monitoring was performed at the time of initial and second blood sampling in all patients with unstable angina. An episode of ischemic ST-segment shift from baseline was considered to be present if->l mm (1 mm = 0.1 mV) ST elevation or horizontal or downsloping ST depression 80 msec from the J point was present for ->60 sec. Measurement of ANP and BNP concentrations. Plasma concentration of ANP was measured with a specific immunoradiometric assay for human ~-ANP (Shionoria ANP kit, Osaka, Japan) as reported previously. 6 The minimal detectable quantity of human a-ANP is 5 pg/ml. The intraassay and interassay coefficients of variation were 4.7% and 5.8%, respectively. The cross-reactivity with human BNP was <0.001% on a molar basis. Plasma concentration of BNP was measured with a new and specific immunoradiometric assay for human BNP, as reported previously, s The minimal detectable quantity of human BNP is 2 pg/ml. The intraassay and interassay coefficients of variation were 5.3% and 5.9%, respectively. Tile cross-reactivity with human c¢-ANP was <0.001% on a molar basis. The plasma samples frozen at -80°C were stable for the assays for >20 days after sampling, and all samples were measured within 2 weeks after sampling. Statistics. To evaluate significant differences in the
plasma levels of ANP and BNP, hemodynamic parameters, and age in the three groups, comparison of the three groups was obtained by one-way analysis of variance; if it was significant, pairwise comparisons were done by the Bonferroni criterion. The changes in the plasma levels of ANP and BNP and in the number of episodes of myocardial ischemia were estimated by a paired t test. Comparison of the plasma levels of BNP between two subgroups in patients with unstable angina was done by an unpaired t test. The clinical characteristics in Table I (except age) were compared by a chi-square test. Probability values were considered statistically significant at <0.05. Data were expressed as the mean _+ SD or counts. RESULTS Plasma levels of ANP and BNP. The p l a s m a levels of B N P were significantly increased in the u n s t a b l e a n g i n a group as c o m p a r e d with those in the stable exertional a n g i n a group a n d the control group (39.5 + 29.4 pg/ml vs 15.1 _+ 8.0 p g / m l ; p < 0.01; a n d 39.5 +_ 29.4 pg/ml vs 10.3 +_ 6.4 pg/ml; p < 0.01; respectively), as s h o w n in Fig. 1. I n 22 (67%) of the 33 patients with u n s t a b l e a n g i n a , the p l a s m a levels of B N P were elevated above the m e a n + 2 SD of the levels in the control group or 23 pg/ml at the initial blood s a m p l i n g before t r e a t m e n t . I n the u n s t a b l e a n g i n a group, t h e r e was no significant difference in the p l a s m a levels of B N P b e t w e e n the patients with
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Table II. Hemodynamic data Control
(n =2O) H R (beats/min) A O P (ram Hg) R A P (ram Hg) P C W P (ram Hg) CI (L/min/m 2) L V E D P ( m m Hg) L V E F (%) LVESVI (ml/m 2)
73 105 4.7 6.5 3.1 10.8 73 22
Stable exertional angina (n = 20)'
-+ 10 +- 13 +_ 1.5 -+ 2.5 +- 0.5 -+ 4.7 -+ 7 ± 4
69 104 5.0 7.0 3.0 10.5 70 23
± 9 ± 15 ± 2.0 +- 3.0 -+ 0.4 +- 4.6 ± 8 ± 7
Unstable angina (n = 22)* 65 102 4.7 6.8 2.9 10.9 67 26
+- 12 ± 12 +- 2.4 -+ 3.2 -+ 0.6 ± 5.6 ± 10 +- 7
p Value NS NS NS NS NS NS NS NS
Values are expressed as mean -+ SD, HR, Heart rate; NS, not significant. *Cardiac catheterization was performed at the initial blood sampling.
multivessel coronary spasm and those without (47.4 _+ 40.3 pg/ml vs 36.1 +- 23.5 pg/ml; NS). There was no significant difference in the plasma levels of BNP between the control group and the stable exertional angina group (Fig. 1). To examine the relation between the degree of myocardial ischemia and the increase in BNP in patients with unstable angina, we subdivided the patients with proximal left anterior descending (LAD) artery lesions, which may reflect a larger area ofischemic myocardium, with those with right coronary lesions, which may reflect a smaller area. Sixteen patients had proximal LAD lesions, and 9 patients had right coronary lesions. There was no significant difference in the plasma levels of BNP between the two subgroups (proximal LAD lesions, 43.8 + _ 24.9 pg/ml vs. right coronary lesions, 36.3 + 38.4 pg/ml, respectively; NS). Moreover, there was no significant difference in the plasma levels of BNP between the patients with ST-segment elevation and those with ST-segment depression during the attack (37.8 +- 32.2 pg/ml vs 41.2 +_ 27.3 pg/ml; NS). However, the plasma levels of BNP were significantly increased in the patients with regional wallmotion abnormalities, as assessed by echocardiography, as compared with the levels in those without (61.6 +- 35.7 pg/ml vs 31.3 -+ 22.3 pg/ml; p < 0.01). There was no significant difference in the plasma levels of AMP among the three groups (24.9 +- 11.4 pg/ml in the control group, 28.3 +_ 13,6 pg/ml in the stable exertional anginagroup, and 28.3 +- 11.2 pg/ml in the unstable angina group, respectively), as shown in Fig. 1. Comparison o f hemodynamic data. Table I I compares hemodynamic data among the three groups.
Cardiac catheterization was performed at the initial blood sampling in 22 of the 33 patients with unstable angina. There were no significant differences in
the hemodynamic parameters (including HR, AOP, RAP, PCWP, CI, LVEDP, LVEF, and LVESVI) among the three groups. Plasma ANP and BNP and echocardiographicfindings after treatment of unstable and stable angina. Twenty-
eight (85%) of the 33 patients with unstable angina had episodes of myocardial ischemia, including silent ischemia during the initial Holter monitoring, and the number of episodes of myocardial ischemia decreased significantly after the medical treatment (from 4.8 +_ 4.1 episodes/24 hours to 0.4 _+ 1.1 episodes/24 hours; p < 0.01) in these patients. The remaining 5 patients had no ECG evidence of ischemia during both the initial and second Holter monitorings. However, all of them had antianginal drugs during the initial Holter monitoring because of severity and frequency of attacks. In the patients with unstable angina, the plasma levels of BNP decreased significantly after the medical treatment (from 39.5 +- 29.4 pg/ml to 15.8 + 11.0 pg/ml; p < 0.01), whereas the plasma levels of ANP did not change significantly (from 28.3 +_ 11.2 pg/ml to 26.5 _+ 12.3 pg/ml; p = NS; Fig. 2). On the other hand, there were no significant changes in the plasma levels of ANP and BNP after medical treatment (ANP from 28.3 +_ 13.6 pg/ml to 29.0 +- 14.1 pg/ml; p = NS; BNP from 15.1 +_ 8.0 pg/ml to 16.3 +_ 10.1 pg/ml; p = NS) in the patients with stable exertional angina (Fig. 3). Angina was still uncontrollable in one patient with unstable angina, in whom the plasma level of BNP decreased but still remained high the fourth week after intensive medical treatment (from 66 to 50 pg/ml). In this patient, coronary artery bypass surgery was done to control the anginal attacks. Nine patients had regional wall-motion abnormalities assessed by ECG at the time of initial blood sampling in the unstable angina group, and all of
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Fig. 2. Changes in plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) after medical treatment in patients with unstable angina. Plasma levels of BNP decreased significantly after medical treatment. Plasma levels of ANP did not change significantly after treatment. Bars, Mean _+SD.
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Fig. 3. Changes in plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) after medical treatment in patients with stable exertional angina. Plasma levels of ANP and BNP did not change significantly after treatment. Bars, Mean _+SD.
them had elevated plasma BNP levels. These regional wall-motion abnormalities disappeared or were alleviated at the time of second blood sampling in all of these patients (8 patients from hypokinesis to normal motion; 1 patient from akinesis to hypokinesis) in parallel with normalization or decrease of plasma BNP levels. All of these patients were those who required the continued drug treatment at the time of the initial blood sampling. No left ventricular abnormalities were assessed by ECG, both before
and after the medical treatment, in the patients with stable exertional angina. DISCUSSION
BNP is a novel cardiac hormone secreted mainly from ventricles, 4-6 whereas ANP is secreted mainly from atria. 14"19We showed that the plasma levels of BNP are markedly increased in patients with congestive heart failure, in proportion to the severity of left ventricular dysfunction, and surpass those of
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ANP in severe cases. 4-6 We also showed that the plasma levels of BNP are markedly increased in patients with acute myocardial infarction, whereas the plasma levels of ANP are only mildly increased. 7, s Unstable angina is intermediate in severity between acute myocardial infarction and chronic stable angina and is often a precursor of acute myocardial infarction. 9"12In our study, the plasma levels of BNP were ~significantly higher in the unstable angina group than in the stable exertional angina group and the control group. However, the plasma BNP levels were increased only mildly (mean, 4 times the normal level) in patients with unstable angina, whereas the levels were increased markedly (mean, 100 times the normal level) in patients with acute myocardial infarction. 7, s The levels were comparable between the stable exertional angina group and the control group. Our study also showed that the plasma levels of BNP decreased toward normal when the attacks were controlled after the medical treatment in patients with unstable angina. Because the plasma levels of BNP did not change significantly after the same medical treatment in the patients with stable exertional angina, the decrease in the plasma levels of BNP after the attacks were controlled is not the result of the direct effect of the drugs on BNP but of the healing of the coronary lesions responsible for the attacks in patients with unstable angina. These results suggest that plasma levels of BNP may serve as a marker of a spectrum of severities in patients with angina pectoris. Coronary artery spasm has been implicated in the pathogenesis of unstable angina or acute myocardial infarction. 11 We previously reported that patients with multivessel spasm have severe and prolonged angina, and their coronary arteries are normal or almost normal. 2°, 21 This type of patient is not rare in the Japanese population. Therefore, in our study, 10 patients who had multivessel coronary spasm and severe and prolonged angina at rest were included in the unstable angina group. The precise mechanism(s) of the increased secretion of BNP in patients with unstable angina is (are) unclear. There is a positive linear relation between plasma levels of ANP and atrial pressure, indicating that atrial pressure or stretch plays an important role in regulating secretion of ANP. 5, 6, 18-i9 On the other hand, we recently showed that the plasma levels of BNP reflect mainly the degree of left ventricular overload in patients with chronic heart failure.5' 6 In our study, there were no abnormalities and no significant differences in hemodynamic parameters such as PCWP, LVEDP, and LVEF among the
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three groups at the time of blood sampling when no attack occurred. Thus both atrial and ventricular overloads as the stimuli for the secretion of ANP and BNP were assumed comparable among the three groups. Moreover, patients who may have increased plasma BNP levels, such as those with previous myocardial infarction, congestive heart failure, valvular heart disease, cardiomyopathy, left ventricular hypertrophy, or renal failure, were excluded from this study. Furthermore, the plasma levels of ANP were normal in all of the three groups, and there was no significant difference in the levels among them. The elevation of plasma BNP levels in the unstable angina group, therefore, cannot be explained by the global hemodynamic changes. As severe or frequent myocardial ischemia (or both) occurred in the patients with unstable angina, ischemic attacks may have augmented the regional ventricular wall stretch even in the presence of the normal global hemodynamic parameters and may have stimulated BNP secretion in these patients. That the plasma levels of BNP were higher in the patients with unstable angina who showed left ventricular regional wallmotion abnormalities than in those who had normal wall motion may support this line of thinking. The plasma levels of ANP were not elevated, even in the patients with unstable angina. This is probably because ANP is released mainly from granules in atria in response to atrial stretch, 14-19 and the atrial wall stress was not augmented in the patients with unstable angina at the time of blood sampling. If the severe ischemic attacks that increase the atrial wall stretch occur, the ANP secretion may be increased transiently in the patients with unstable angina, as in those with acute myocardial infarction, s, 22, 23 We previously showed that the plasma levels of BNP were markedly increased in patients with acute myocardial infarction. 7, 8 However, the levels did not have significant correlations with the hemodynamic parameters in the early phase of acute myocardial infarction,7, s as did the plasma levels of BNP in patients with unstable angina in this study. This is in contrast to the fact that the plasma levels of BNP are highly correlated with the hemodynamic parameters in patients with chronic congestive heart failure. 4-6 Thus there is a possibility that factor(s) other than mechanical stress may have stimulated the BNP secretion in acute myocardial infarction, s, 24, 25 We suggested that BNP may, in part, be increased as one of the acute-phase reactants that are released in response to acute tissue injuries in the early phase of acute myocardial infarction, s, 24, 25 Several studies suggested the presence of an inflammatory component in unstable angina. 26"31 Recently Mazzone et
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al. 32 showed that an inflammatory reaction takes place within the coronary tree in patients with unstable angina. We therefore think that BNP may be secreted as the acute-phase reactant also in patients with unstable angina. That the DNA of BNP has an adenosine adenine thymine-rich sequence in the 3'-untranslated region that is known to destabilize messenger RNA (mRNA), is associated with acute-phase reactants, and is not found in the DNA of A N P supports this line of thinking. 25, 33, 34 In some of the patients with unstable angina, the plasma levels of BNP were not or were only mildly increased before treatment. It is possible that the plasma levels of BNP may not be increased in a subset of patients with unstable angina, because the mechanisms of unstable angina may not be identical in all patients. 10-12 In conclusion, we showed that the plasma levels of BNP are increased in the majority of patients with unstable angina and that the levels decrease toward normal after treatment. REFERENCES 1. Itoh H, Nakao K, Yamada T, Shirakami G, Kangawa K, Minamino N, et al. Antidipsogenic action of a novel peptide "brain natriuretic peptide" in rats. Eur J Pharmacol 1988;150:193-6. 2. Yamada T, Nakao K, Itoh H, Shirakami G, Kangawa K, Minamino M, et al. Intracerebroventricular injection of brain natrinretic peptide irahibits vasopressin secretion in conscious rats. Neurosci Lett 1988;95: 223-8. 3. Shirakami G, Nakao K, Yamada T, Itoh H, Mori K, Kangawa K, et al. Inhibitory effect of brain natriuretic peptide on central angiotensin IIstimulated pressorresponse in consciousrats. Neurosci Lett 1988;91:7783. 4. Mukoyama M, Nakao K, Saito Y, Ogawa Y, Hosoda K, Suga S, et al. Brain natriuretic peptide (BNP) as a novel cardiac hormone in humans: evidence for an exquisite dual natriuretic peptide system, ANP and BNP. J Clin Invest 1991;87:1402-12. 5. YoshimtLra M, Yasue H, Okumura K, Ogawa H, Jougasaki M, Mukoyama M, et al. Different secretion patterns of atrial natriuretic peptide and brain natriuretic peptide in patients with congestive heart failure. Circulation 1993;87:464-9. 6. Yasue H, Yoshimura M, Sumida H, Kikuta K, Kugiyama K, Jougasaki M, et al. Localization and mechanism of secretion of B-type natriuretic peptide in comparison with those of A-type natriuretic peptide in normal subjects and patients with heart failure. Circulation 1994;90:195203. 7. Mukoyama M, Nakao K, Obata K, Jougasaki M, Yoshimura M, Morita E, et al. Augmented secretion of brain natriuretic peptide in acute myocardial infarction. Biochem Biophys Res Commun 1991;180:431-6. 8. Morita E, Yasue H, Yoshimura M, Ogawa H, Jougasaki M, Matsumura T, et al. Increased plasma levels of brain natriuretic peptide in patients with acute myocardial infarction. Circulation 1993;88:82-91. 9. Braunwald E. Unstable sngina: a classification. Circulation 1989;80: 410-14. 10. Willerson JT, Golino P, Eidt J, Campbell WB, Buja LM. Specific platelet mediators and unstable coronary artery lesions: experimental evidence and potential clinical implications. Circulation 1989;80:198-205. I1. Fuster V, Badimon L, Badimon JJ, Chesebro JH. The pathegenesis of coronary artery disease and the acute coronary syndromes. N Engl J Med 1992;326:242-50, 310-18. 12. Th~rouxP, WatersD. Diagn°sis and management °fpatientswithunstable angina. In: Schlant RC, Alexander RW, editors. Hurst's the heart: arteries and veins. 8th ed. New York: McGraw-Hill, 1994:10831106. 13. Yasue H, Horio Y, Nakamura N, Fujii H, Imoto N, Sonoda R, et al. In-
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duction of coronary artery spasm by acetylcholine in patients with variant angina: possible role of the parasympathetic nervous system in the pathogenesis of coronary artery spasm. Circulation 1986;74:955-63. 14. de Bold AJ, Borenstein HB, Veress AT, Sonnenberg H. A rapid and important natriuretic response to intravenous injection of atrial myocardial extracts in rats. Life Sci 1981;28:89-94. 15. Laragh JH. Atrial natriuretic hormone, the renin aldosterone axis, and blood pressure-electrolyte homeostasis. N Engl J Med 1985;313:133040. 16. Needleman P, Greenwald JE. Atriopeptin: a cardiac hormone intimately involved in fluid, electrolyte, and blood-pressure homeostasis. N Engl J Med 1986;314:828-34. 17. Buruett JC Jr, Kao PC, Hu DC, Heser DW, Heublein D, Granger JP, et al. Atrial natriuretic peptide elevation in congestive heart failure in the human. Science 1986;231:1145-7. :LB. Raine AEG, Erne P, B~rgisser E, Miiller FB, Bolli P, Burkart F, et al. Atrial natriuretic peptide and atrial pressure in patients with congestive heart failure. N Engl J Med 1986;315:533-7. 19. Edwards BS, Ackermann DM~ Lee ME, Reeder GS, Wold LE, Burnett JC Jr. Identification ofatrial natriuretic factor within ventricular tissue in hamsters and humans with congestive heart failure. J Clin Invest 1988;81:82-6. 20. Kugiyama K, Yasue H, Okumura K, Takaoka K, Matsuyama K, Kojima A, et al. Simultaneous multivessel coronary artery spasm demonstrated by quantitative analysis of thallium-201 single photon emission computed tomography. Am J Cardiol 1987;60:1009-14. 21. Okumura K, Yasue H, Horio Y, Takaoka K, Matsuyama K, Kugiyama K, et al. Mult~vessel coronary spasm in patients with variant angina: a study with intracoronary injection of acetylcholine. Circulation 1988;77:535-42. 22. Wencker M, Lechleitner P, Dienstl F, Hauptlorenz S, Puschendorf B. Early decrease in atrial natriuretic peptide in acute myocardial infarction. Lancet 1987;1:1369. 23. Tan ACITL, van Loenhout TT, Lamfers EJP, Hooghoudt TEH, Kloppenborg PWC, Benraad TJ. Atrial natriuretic peptide after myocardial infarction. Am Heart J 1989;118:490-4. 24. Hama N, Itoh H, Shirakami G, Nakagawa O, Suga S, Ogawa Y, et al. Rapid ventricular induction of brain natrinretic peptide gene expression in experimental acute myocardial infarction. Circulation 1995; 92:1558-64. 25. Nakagawa O, Ogawa Y, Itoh H, Suga S, Komatsu Y, Kishimoto I, et al. Rapid transcriptional activation and early mRNA turnover of brain natriuretic peptide in cardiocyte hypertrophy. J Clin Invest 1995;96: 1280-7. 26. Kohchi K, Takebayashi S, Hirold T, Nobuyoshi M. Significance of adventitial inflammation of the coronary artery in patients with unstable angina: results at autopsy. Circulation 1985;71:709-16. 27. Berk BC, Weintraub WS, Alexander RW. Elevation of C-reactive protein in "active" coronary artery disease. Am J Cardiol 1991;91:168-72. 28. Dinerman JL, Mehta JL, Saldeen TGP, Emerson S, Wallin R, Davda R, et al. Increased neutrophil elastase release in unstable angina pecteris and acute myocardial infarction. J Am Coil Cardio11990;15:155963. 29. van der Wal AC, Becket AE, van der Lees CM, Das FK. Site ofintimal rupture or erosion of thrombosed coronary atherosclcrotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology. Circulation 1994;89:36-44. 30. Buja LM, Willerson JT. Role of inflammation in coronary plaque disruption. Circulation 1994;89:503-5. 31. Lizzo G, Biasucci LM, Gallimore JR, Grille RL, Rebuzzi AG, Pepys MB, et al. The prognostic value of C-reactive protein and serum amyloid A protein in severe unstable angina. N Engl J Med 1994;331:417-24. 32. Mazzone A, De Servi S, Ricevuti G, Mazzucchelli I, Fossati G, Pasotti D, et al. Increased expression of neutrophil and monocyte adhesion molecules in unstable coronary artery disease. Circulation 1993;22:35863. 33. KojimaM, MinaminoN, KangawaK, Matsuo H. Cloningand sequence analysis ofcDNA encoding a precursor for rat brain natriuretic peptide. Biochem Biophys'Res Commun 1989;159:1420-6. 34. Shaw G, Kamen R. A conserved AU sequence from the 3' untranslated region of GM-CSF mRNA mediates selective mRNA degradation. Cell 1986;46:659-67.
and Kyoto, Japan
This study was designed to examine the plasma levels of Btype or brain natriuretic peptide (BNP), as well as A-type or atrial natriuretic peptide (ANP) in patients with unstable angina as compared with those in patients with stable exertional angina and control subjects. We measured the plasma levels of BNP and ANP in 33 patients with unstable angina, 20 patients with stable exertional angina, and 20 control subjects. The plasma levels of BNP were significantly increased in patients with unstable angina compared with those in patients with stable exertional angina and control subjects, respectively (39.5 ± 29.4 pg/ml vs 15.1 ± 8.0 pg/ ml; ,o<0.01 and 39.5 ±29.4 pg/ml vs 10.3 ± 6 . 4 pg/ml; p < 0.01, respectively). On the other hand, there was no significant difference in the plasma levels of ANP among the three groups. Furthermore, in patients with unstable angina, the plasma levels of BNP decreased significantly after the medical treatment (from 39.5 ± 29.4 pg/ml to 15.8 ~ 11.0 pg/ ml; p< 0.01), whereas the plasma levels of ANP did not change. We conclude that the plasma levels of BNP are increased in the majority of patients with unstable angina and that the increased levels decrease toward normal after treatment. (Am Heart J 1996;132:101-7.)
B-type or b r a i n n a t r i u r e t i c peptide (BNP) f o r m s a peptide f a m i l y w i t h A-type or atrial n a t r i u r e t i c peptide (ANP) a n d m a y be involved in the r e g u l a t i o n of blood p r e s s u r e a n d fluid volumes. 1-3 We d e m o n s t r a t e d t h a t B N P is a novel cardiac h o r m o n e secreted p r e d o m i n a n t l y f r o m the ventricle, a n d its p l a s m a levels a r e m a r k e d l y i n c r e a s e d in p a t i e n t s w i t h chronic congestive h e a r t failure. 4-6 T h e p l a s m a levels of B N P w e r e m a r k e d l y increased, w h e r e a s the
From the aDivision of Cardiology, Kumamoto University School of Medicine, and the bSecond Division, bDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine. Supported in part by a grant from the Ministry of Education and Culture (04263104) and a grant from the Smoking Research Foundation. Received for publication May 22, 1995; accepted Nov. 27, 1995. Reprint requests: Hirofumi Yasue, MD, Division of Cardiology, Kumamoto UNiversity School of Medicine, Honjo 1-1-1, Kumamoto 860, Japan. Copyright © 1996 by Mosby-Year Book, Inc. 0002-8703/96/$5.00 + 0 4/1/72010
p l a s m a levels of A N P w e r e only mildly i n c r e a s e d in p a t i e n t s w i t h acute m y o c a r d i a l infarction. 7, 8 U n s t a b l e a n g i n a is i n t e r m e d i a t e in s e v e r i t y bet w e e n acute m y o c a r d i a l infarction a n d chronic stable a n g i n a a n d m a y h e r a l d acute m y o c a r d i a l infarction. 9-12 However, t h e p l a s m a levels of B N P a r e not k n o w n in p a t i e n t s w i t h u n s t a b l e angina. I n our study, we e x a m i n e d t h e p l a s m a levels of B N P a n d A N P in p a t i e n t s w i t h u n s t a b l e a n g i n a as c o m p a r e d w i t h those in p a t i e n t s w i t h stable exertional a n g i n a a n d control subjects. METHODS Patients. We studied 73 patients (49 men and 24 women,
mean age 60 _+ 8 years; range, 44 to 75 years). They consisted of three groups: unstable angina group, stable exertional angina group, and Control group. The unstable angina group consisted of 33 patients with unstable angina. Unstable angina was defined as an accelerating pattern of chest pain (recent increase in severity or frequency or both), lasting ->15 minutes on at least one occasion or occurring at rest or during minimal activity. Of the 33 patients with unstable angina, 16 had ST-segment elevation and 17 had ST-segment depression on the electrocardiogram (ECG) during the chest pain. There was no evidence of acute myocardial infarction, as documented by the absence of QRS change on the ECG and the absence of an elevation of serial serum creatine kinase MB isoenzyme levels greater than twice the upper limit of normals. Those from whom blood sampling for ANP and BNP could not be done within 24 hours after the last attack were excluded from this study. The stable exertional angina group consisted of 20 patients who had typical exertional angina associated with horizontal or downsloping ST-segment depression of >1.0 m m on an exercise test. The control group consisted of 20 patients with atypical chest pain who underwent coronary angiography and who were negative for myocardial ischemia on a treadmill exercise test and a hyperventilation test. Patients with previous myocardial infarction were excluded from this study because the plasma levels of BNP 101
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Table I. Characteristics of the study groups Control
Stable exertional angina
No. of patients 20 20 Age (yr) Mean +- SD 60 _+7 62 _+8 Range 44-72 46-74 Male/female ratio 12/8 14/6 Blood pressure 7 9 ->150/90 mra Hg (n) No. diseased vessels (>75% stenosis)* 0 vessel (n) 20 0 1 vessel (n) 0 10 2 vessel (n) 0 7 3 vessel (n) 0 3
Unstable angina
33 59 -+ 8 46-75 23/10 15 5 17 4 7
*There was no significant difference in the incidence of coronary artery disease between the stable exertional angina group and the unstable angina group.
in patients with acute myocardial infarction is still much higher in the fourth week from the onset than those in the controlsS; the plasma levels of BNP in patients with old myocardial infarction remain to be clarified. Patients also were excluded if they had congestive heart failure, valvular heart disease, cardiomyepathy, left ventricular hypertrophy, or renal failure. The clinical characteristics of the three groups are described in Table I. There were no significant differences in age, sex, and the prevalence of hypertension among the three groups. The study protocol was in agreement with the guidelines established by the ethics committee at our institution. Written informed consent was obtained from each patient and his or her family. Cardiac catheterization and blood sampling. Cardiac catheterization was done in all 73 patients. All drugs except sublingual nitroglycerin and aspirin were withdrawn at least 1 day before the catheterization except in 14 patients with unstable angina, for whom antianginal drugs such as nitrates, calcium antagonists, or both were indispensable because of inability to carry on any physical activity without discomfort. In the unstable angina group, initial blood sampling for ANP and BNP were done within 24 hours after the last attack. In 22 of the unstable angina group, cardiac catheterization together with blood sampling for ANP and BNP could also be done within 24 hours after the last attack. No attack occurred during blood sampling in the patients with unstable angina. The mean time between the last episode of chest pain and initial blood sampling in those patients was 12.6 ± 9.1 hours (range, 1 to 24 hours). After initial blood sampling from the peripheral vein, hemodynamic measurements, including pulmonary capillary wedge pressure (PCWP), mean right atrial pressure (RAP), and cardiac index (CI), were performed by using a Swan-Ganz catheter inserted into the femoral vein. Cardiac index was measured by thermodilution technique in triplicate. A Sones catheter was inserted into a brachial artery, and mean aortic pressure (AOP) and left ventricular end-diastolic pressure (LVEDP) were measured. After blood sampling and the hemodynamic study, coronary an-
Journal
giography and left ventriculography were per~brmed in all patients. Left ventricular ejection fraction (LVEF) and left ventricular end-systolic volume index (LVESVI) were determined by left ventriculography. In the unstable angina group, 28 patients had significant organic coronary artery stenosis >75% of luminal diameter in the major coronary arteries, and 10 had multivessel coronary artery spasm, demonstrated by the intracoronary injection of acetylcholine. 13 Five of 10 patients with multivessel coronary spasm had 75% organic stenosis in one major coronary artery, and the remaining 5 patients had no significant organic stenosis (2 with <25% stenosis and 3 without stenosis). All patients with stable exertional angina had coronary artery stenosis >75% of luminal diameter in the major coronary arteries. All control subjects had no significant organic stenosis in their coronary arteries (14 without stenosis and 6 with <25% stenosis), and no coronary spasm was demonstrated by the intracoronary injection of acetylcholine.13 The number of diseased vessels in the three groups is summarized in Table I. There was no significant difference in the incidence of coronary artery disease between the stable exertiona] angina group and the unstable angina group. All blood samples were placed into ethylenediaminetetraacetic acid (EDTA)-coated tubes containing 1000 IU/ml aprotinine. Thereafter, the plasma immediately was centrifuged at 4 ° C and then stored at -80 ° C until analysis. Treatment of unstable angina and stable exertional angina, All patients with unstable angina received calcium antagonists, nitrates, and aspirin with varying combinations of ~-blockers (8 patients), and the doses were maximized until chest pain was considered controlled. In the unstable angina group, the second blood sampling was performed when the attacks were controlled after the medical treatment. The attacks were considered controlled if the patients had become free of attacks for >1 week or returned to the previous pattern of chronic stable angina pectoris. The mean time between the initial blood sampling and the second blood sampling was 17 _+ 7 days (range, 10 to 32 days). All patients with stable exertional angina received calcium antagonists and aspirin with various combinations of ~-blockers (9 patients) and nitrates (17 patients), and the doses were maximized until chest pain did not occur during daily activity. In the stable exertional angina group, the second blood sampling also was performed after the medical treatment. The mean time between the initial blood sampling and the second blood sampling was 16 +_ 2 days (range, 12 to 30 days). Echocardiographic examination. Echocardiograms were recorded by using Toshiba 160A (Tokyo, Japan) twodimensional echocardiographic equipment with transducers ranging in frequency from 2.25 to 3.5 MHz. A complete two-dimensional echocardiogram was recorded in S-VHS videotape. In the unstable angina group, parasternal longand short-axis, as well as apical four- and two-chamber views, were recorded at the time of initial and second blood sampling for ANP and BNP. Images at the time of initial and second blood sampling were transferred online in digital form for display as continuous-loop images in quad-
Volume 132, Number 1, Part 1
Kikutc et al.
AmericanHeartJournal
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Fig. 1. Plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) in patients with unstable angina, in those with stable exertional angina, and in control subjects. Plasma levels of BNP were significantly higher in patients with unstable angina than in those with stable exertional angina and in control subjects. There was no significant difference in plasma levels of ANP among three groups. Bars, Mean -+ SD. screen format (Freeland Systems, Prism Imaging, Louisville, Colo.). The quadscreen format was transferred onto 3.5-inch disks for analysis. The videotape was analyzed for confirmation. Echocardiographic wall motion was graded as normokinetic, hypokinetic, akinetic, or dyskinetic. Holter monitoring. Twenty-four-hour Holter monitoring was performed at the time of initial and second blood sampling in all patients with unstable angina. An episode of ischemic ST-segment shift from baseline was considered to be present if->l mm (1 mm = 0.1 mV) ST elevation or horizontal or downsloping ST depression 80 msec from the J point was present for ->60 sec. Measurement of ANP and BNP concentrations. Plasma concentration of ANP was measured with a specific immunoradiometric assay for human ~-ANP (Shionoria ANP kit, Osaka, Japan) as reported previously. 6 The minimal detectable quantity of human a-ANP is 5 pg/ml. The intraassay and interassay coefficients of variation were 4.7% and 5.8%, respectively. The cross-reactivity with human BNP was <0.001% on a molar basis. Plasma concentration of BNP was measured with a new and specific immunoradiometric assay for human BNP, as reported previously, s The minimal detectable quantity of human BNP is 2 pg/ml. The intraassay and interassay coefficients of variation were 5.3% and 5.9%, respectively. Tile cross-reactivity with human c¢-ANP was <0.001% on a molar basis. The plasma samples frozen at -80°C were stable for the assays for >20 days after sampling, and all samples were measured within 2 weeks after sampling. Statistics. To evaluate significant differences in the
plasma levels of ANP and BNP, hemodynamic parameters, and age in the three groups, comparison of the three groups was obtained by one-way analysis of variance; if it was significant, pairwise comparisons were done by the Bonferroni criterion. The changes in the plasma levels of ANP and BNP and in the number of episodes of myocardial ischemia were estimated by a paired t test. Comparison of the plasma levels of BNP between two subgroups in patients with unstable angina was done by an unpaired t test. The clinical characteristics in Table I (except age) were compared by a chi-square test. Probability values were considered statistically significant at <0.05. Data were expressed as the mean _+ SD or counts. RESULTS Plasma levels of ANP and BNP. The p l a s m a levels of B N P were significantly increased in the u n s t a b l e a n g i n a group as c o m p a r e d with those in the stable exertional a n g i n a group a n d the control group (39.5 + 29.4 pg/ml vs 15.1 _+ 8.0 p g / m l ; p < 0.01; a n d 39.5 +_ 29.4 pg/ml vs 10.3 +_ 6.4 pg/ml; p < 0.01; respectively), as s h o w n in Fig. 1. I n 22 (67%) of the 33 patients with u n s t a b l e a n g i n a , the p l a s m a levels of B N P were elevated above the m e a n + 2 SD of the levels in the control group or 23 pg/ml at the initial blood s a m p l i n g before t r e a t m e n t . I n the u n s t a b l e a n g i n a group, t h e r e was no significant difference in the p l a s m a levels of B N P b e t w e e n the patients with
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Table II. Hemodynamic data Control
(n =2O) H R (beats/min) A O P (ram Hg) R A P (ram Hg) P C W P (ram Hg) CI (L/min/m 2) L V E D P ( m m Hg) L V E F (%) LVESVI (ml/m 2)
73 105 4.7 6.5 3.1 10.8 73 22
Stable exertional angina (n = 20)'
-+ 10 +- 13 +_ 1.5 -+ 2.5 +- 0.5 -+ 4.7 -+ 7 ± 4
69 104 5.0 7.0 3.0 10.5 70 23
± 9 ± 15 ± 2.0 +- 3.0 -+ 0.4 +- 4.6 ± 8 ± 7
Unstable angina (n = 22)* 65 102 4.7 6.8 2.9 10.9 67 26
+- 12 ± 12 +- 2.4 -+ 3.2 -+ 0.6 ± 5.6 ± 10 +- 7
p Value NS NS NS NS NS NS NS NS
Values are expressed as mean -+ SD, HR, Heart rate; NS, not significant. *Cardiac catheterization was performed at the initial blood sampling.
multivessel coronary spasm and those without (47.4 _+ 40.3 pg/ml vs 36.1 +- 23.5 pg/ml; NS). There was no significant difference in the plasma levels of BNP between the control group and the stable exertional angina group (Fig. 1). To examine the relation between the degree of myocardial ischemia and the increase in BNP in patients with unstable angina, we subdivided the patients with proximal left anterior descending (LAD) artery lesions, which may reflect a larger area ofischemic myocardium, with those with right coronary lesions, which may reflect a smaller area. Sixteen patients had proximal LAD lesions, and 9 patients had right coronary lesions. There was no significant difference in the plasma levels of BNP between the two subgroups (proximal LAD lesions, 43.8 + _ 24.9 pg/ml vs. right coronary lesions, 36.3 + 38.4 pg/ml, respectively; NS). Moreover, there was no significant difference in the plasma levels of BNP between the patients with ST-segment elevation and those with ST-segment depression during the attack (37.8 +- 32.2 pg/ml vs 41.2 +_ 27.3 pg/ml; NS). However, the plasma levels of BNP were significantly increased in the patients with regional wallmotion abnormalities, as assessed by echocardiography, as compared with the levels in those without (61.6 +- 35.7 pg/ml vs 31.3 -+ 22.3 pg/ml; p < 0.01). There was no significant difference in the plasma levels of AMP among the three groups (24.9 +- 11.4 pg/ml in the control group, 28.3 +_ 13,6 pg/ml in the stable exertional anginagroup, and 28.3 +- 11.2 pg/ml in the unstable angina group, respectively), as shown in Fig. 1. Comparison o f hemodynamic data. Table I I compares hemodynamic data among the three groups.
Cardiac catheterization was performed at the initial blood sampling in 22 of the 33 patients with unstable angina. There were no significant differences in
the hemodynamic parameters (including HR, AOP, RAP, PCWP, CI, LVEDP, LVEF, and LVESVI) among the three groups. Plasma ANP and BNP and echocardiographicfindings after treatment of unstable and stable angina. Twenty-
eight (85%) of the 33 patients with unstable angina had episodes of myocardial ischemia, including silent ischemia during the initial Holter monitoring, and the number of episodes of myocardial ischemia decreased significantly after the medical treatment (from 4.8 +_ 4.1 episodes/24 hours to 0.4 _+ 1.1 episodes/24 hours; p < 0.01) in these patients. The remaining 5 patients had no ECG evidence of ischemia during both the initial and second Holter monitorings. However, all of them had antianginal drugs during the initial Holter monitoring because of severity and frequency of attacks. In the patients with unstable angina, the plasma levels of BNP decreased significantly after the medical treatment (from 39.5 +- 29.4 pg/ml to 15.8 + 11.0 pg/ml; p < 0.01), whereas the plasma levels of ANP did not change significantly (from 28.3 +_ 11.2 pg/ml to 26.5 _+ 12.3 pg/ml; p = NS; Fig. 2). On the other hand, there were no significant changes in the plasma levels of ANP and BNP after medical treatment (ANP from 28.3 +_ 13.6 pg/ml to 29.0 +- 14.1 pg/ml; p = NS; BNP from 15.1 +_ 8.0 pg/ml to 16.3 +_ 10.1 pg/ml; p = NS) in the patients with stable exertional angina (Fig. 3). Angina was still uncontrollable in one patient with unstable angina, in whom the plasma level of BNP decreased but still remained high the fourth week after intensive medical treatment (from 66 to 50 pg/ml). In this patient, coronary artery bypass surgery was done to control the anginal attacks. Nine patients had regional wall-motion abnormalities assessed by ECG at the time of initial blood sampling in the unstable angina group, and all of
Volume 132, Number 1, Part 1
Kikuta et al.
AmericanHeartJournal
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Fig. 2. Changes in plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) after medical treatment in patients with unstable angina. Plasma levels of BNP decreased significantly after medical treatment. Plasma levels of ANP did not change significantly after treatment. Bars, Mean _+SD.
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Fig. 3. Changes in plasma levels of A-type natriuretic peptide (ANP; left) and B-type natriuretic peptide (BNP; right) after medical treatment in patients with stable exertional angina. Plasma levels of ANP and BNP did not change significantly after treatment. Bars, Mean _+SD.
them had elevated plasma BNP levels. These regional wall-motion abnormalities disappeared or were alleviated at the time of second blood sampling in all of these patients (8 patients from hypokinesis to normal motion; 1 patient from akinesis to hypokinesis) in parallel with normalization or decrease of plasma BNP levels. All of these patients were those who required the continued drug treatment at the time of the initial blood sampling. No left ventricular abnormalities were assessed by ECG, both before
and after the medical treatment, in the patients with stable exertional angina. DISCUSSION
BNP is a novel cardiac hormone secreted mainly from ventricles, 4-6 whereas ANP is secreted mainly from atria. 14"19We showed that the plasma levels of BNP are markedly increased in patients with congestive heart failure, in proportion to the severity of left ventricular dysfunction, and surpass those of
106
Kikuta et al.
ANP in severe cases. 4-6 We also showed that the plasma levels of BNP are markedly increased in patients with acute myocardial infarction, whereas the plasma levels of ANP are only mildly increased. 7, s Unstable angina is intermediate in severity between acute myocardial infarction and chronic stable angina and is often a precursor of acute myocardial infarction. 9"12In our study, the plasma levels of BNP were ~significantly higher in the unstable angina group than in the stable exertional angina group and the control group. However, the plasma BNP levels were increased only mildly (mean, 4 times the normal level) in patients with unstable angina, whereas the levels were increased markedly (mean, 100 times the normal level) in patients with acute myocardial infarction. 7, s The levels were comparable between the stable exertional angina group and the control group. Our study also showed that the plasma levels of BNP decreased toward normal when the attacks were controlled after the medical treatment in patients with unstable angina. Because the plasma levels of BNP did not change significantly after the same medical treatment in the patients with stable exertional angina, the decrease in the plasma levels of BNP after the attacks were controlled is not the result of the direct effect of the drugs on BNP but of the healing of the coronary lesions responsible for the attacks in patients with unstable angina. These results suggest that plasma levels of BNP may serve as a marker of a spectrum of severities in patients with angina pectoris. Coronary artery spasm has been implicated in the pathogenesis of unstable angina or acute myocardial infarction. 11 We previously reported that patients with multivessel spasm have severe and prolonged angina, and their coronary arteries are normal or almost normal. 2°, 21 This type of patient is not rare in the Japanese population. Therefore, in our study, 10 patients who had multivessel coronary spasm and severe and prolonged angina at rest were included in the unstable angina group. The precise mechanism(s) of the increased secretion of BNP in patients with unstable angina is (are) unclear. There is a positive linear relation between plasma levels of ANP and atrial pressure, indicating that atrial pressure or stretch plays an important role in regulating secretion of ANP. 5, 6, 18-i9 On the other hand, we recently showed that the plasma levels of BNP reflect mainly the degree of left ventricular overload in patients with chronic heart failure.5' 6 In our study, there were no abnormalities and no significant differences in hemodynamic parameters such as PCWP, LVEDP, and LVEF among the
July 1996 American Heart Journal
three groups at the time of blood sampling when no attack occurred. Thus both atrial and ventricular overloads as the stimuli for the secretion of ANP and BNP were assumed comparable among the three groups. Moreover, patients who may have increased plasma BNP levels, such as those with previous myocardial infarction, congestive heart failure, valvular heart disease, cardiomyopathy, left ventricular hypertrophy, or renal failure, were excluded from this study. Furthermore, the plasma levels of ANP were normal in all of the three groups, and there was no significant difference in the levels among them. The elevation of plasma BNP levels in the unstable angina group, therefore, cannot be explained by the global hemodynamic changes. As severe or frequent myocardial ischemia (or both) occurred in the patients with unstable angina, ischemic attacks may have augmented the regional ventricular wall stretch even in the presence of the normal global hemodynamic parameters and may have stimulated BNP secretion in these patients. That the plasma levels of BNP were higher in the patients with unstable angina who showed left ventricular regional wallmotion abnormalities than in those who had normal wall motion may support this line of thinking. The plasma levels of ANP were not elevated, even in the patients with unstable angina. This is probably because ANP is released mainly from granules in atria in response to atrial stretch, 14-19 and the atrial wall stress was not augmented in the patients with unstable angina at the time of blood sampling. If the severe ischemic attacks that increase the atrial wall stretch occur, the ANP secretion may be increased transiently in the patients with unstable angina, as in those with acute myocardial infarction, s, 22, 23 We previously showed that the plasma levels of BNP were markedly increased in patients with acute myocardial infarction. 7, 8 However, the levels did not have significant correlations with the hemodynamic parameters in the early phase of acute myocardial infarction,7, s as did the plasma levels of BNP in patients with unstable angina in this study. This is in contrast to the fact that the plasma levels of BNP are highly correlated with the hemodynamic parameters in patients with chronic congestive heart failure. 4-6 Thus there is a possibility that factor(s) other than mechanical stress may have stimulated the BNP secretion in acute myocardial infarction, s, 24, 25 We suggested that BNP may, in part, be increased as one of the acute-phase reactants that are released in response to acute tissue injuries in the early phase of acute myocardial infarction, s, 24, 25 Several studies suggested the presence of an inflammatory component in unstable angina. 26"31 Recently Mazzone et
Volume 132, Number 1, Part 1 American Heart Journal
al. 32 showed that an inflammatory reaction takes place within the coronary tree in patients with unstable angina. We therefore think that BNP may be secreted as the acute-phase reactant also in patients with unstable angina. That the DNA of BNP has an adenosine adenine thymine-rich sequence in the 3'-untranslated region that is known to destabilize messenger RNA (mRNA), is associated with acute-phase reactants, and is not found in the DNA of A N P supports this line of thinking. 25, 33, 34 In some of the patients with unstable angina, the plasma levels of BNP were not or were only mildly increased before treatment. It is possible that the plasma levels of BNP may not be increased in a subset of patients with unstable angina, because the mechanisms of unstable angina may not be identical in all patients. 10-12 In conclusion, we showed that the plasma levels of BNP are increased in the majority of patients with unstable angina and that the levels decrease toward normal after treatment. REFERENCES 1. Itoh H, Nakao K, Yamada T, Shirakami G, Kangawa K, Minamino N, et al. Antidipsogenic action of a novel peptide "brain natriuretic peptide" in rats. Eur J Pharmacol 1988;150:193-6. 2. Yamada T, Nakao K, Itoh H, Shirakami G, Kangawa K, Minamino M, et al. Intracerebroventricular injection of brain natrinretic peptide irahibits vasopressin secretion in conscious rats. Neurosci Lett 1988;95: 223-8. 3. Shirakami G, Nakao K, Yamada T, Itoh H, Mori K, Kangawa K, et al. Inhibitory effect of brain natriuretic peptide on central angiotensin IIstimulated pressorresponse in consciousrats. Neurosci Lett 1988;91:7783. 4. Mukoyama M, Nakao K, Saito Y, Ogawa Y, Hosoda K, Suga S, et al. Brain natriuretic peptide (BNP) as a novel cardiac hormone in humans: evidence for an exquisite dual natriuretic peptide system, ANP and BNP. J Clin Invest 1991;87:1402-12. 5. YoshimtLra M, Yasue H, Okumura K, Ogawa H, Jougasaki M, Mukoyama M, et al. Different secretion patterns of atrial natriuretic peptide and brain natriuretic peptide in patients with congestive heart failure. Circulation 1993;87:464-9. 6. Yasue H, Yoshimura M, Sumida H, Kikuta K, Kugiyama K, Jougasaki M, et al. Localization and mechanism of secretion of B-type natriuretic peptide in comparison with those of A-type natriuretic peptide in normal subjects and patients with heart failure. Circulation 1994;90:195203. 7. Mukoyama M, Nakao K, Obata K, Jougasaki M, Yoshimura M, Morita E, et al. Augmented secretion of brain natriuretic peptide in acute myocardial infarction. Biochem Biophys Res Commun 1991;180:431-6. 8. Morita E, Yasue H, Yoshimura M, Ogawa H, Jougasaki M, Matsumura T, et al. Increased plasma levels of brain natriuretic peptide in patients with acute myocardial infarction. Circulation 1993;88:82-91. 9. Braunwald E. Unstable sngina: a classification. Circulation 1989;80: 410-14. 10. Willerson JT, Golino P, Eidt J, Campbell WB, Buja LM. Specific platelet mediators and unstable coronary artery lesions: experimental evidence and potential clinical implications. Circulation 1989;80:198-205. I1. Fuster V, Badimon L, Badimon JJ, Chesebro JH. The pathegenesis of coronary artery disease and the acute coronary syndromes. N Engl J Med 1992;326:242-50, 310-18. 12. Th~rouxP, WatersD. Diagn°sis and management °fpatientswithunstable angina. In: Schlant RC, Alexander RW, editors. Hurst's the heart: arteries and veins. 8th ed. New York: McGraw-Hill, 1994:10831106. 13. Yasue H, Horio Y, Nakamura N, Fujii H, Imoto N, Sonoda R, et al. In-
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