- Email: [email protected]
Antiheparin and antifibrinolytic activity of blood in patients with atherosclerosis
Antiheparin activity
and
anWrinolytic
of blood
in putients
with
atlmresdsrosis
A. L. Myasnikov” E. I. Chazov Moscow, U.S.S.R.
I
n recent years there have been many discoveries clarifying the causes of the tendency to thrombosis in atherosclerotic blood vessels. Professor Kudriashov, of Moscow University, showed that one of the major factors in the tendency to thrombosis is a disturbance in the “physiologic anticoagulant system.” Our work and that of our collaborators has shown that these disturbances appear initially in patients with atherosclerosis. The activities of heparin and active fibrinolysin are decreased in patients with atherosclerosis. In attempting to determine the mechanism of this decrease in activity, we have investigated the activity of inhibitors of heparin and fibrinolysin-antiheparin and antifibrinolysin. Materials
and
methods
Because of the observation that the anticoagulant action of heparin added to normal plasma is diminished by the addition of aged serum, Poller13studied the possible connection of this antiheparin activity and the appearance of thrombosis. This antiheparin activity does not depend on the activity of Factor VII or the Christmas factor, and is not diminished by therapy with phenindione. A correlation was thought to exist between the antiheparin activity of serum and the appearance of thrombosis. From the Institute of Therapy. Academy Received for publication Feb. 5, 1963. *Address: Institute of Therapy, Academy
18
Antiheparin activity was assayed by the following method. To 5 ml. of venous blood was added 0.21 ml. of a mixture of 1.6 per cent potassium oxalate and 2.4 per cent ammonium oxalate. From this, 0.2 ml. of plasma was placed in a water-bath at 37°C. and mixed with 0.1 ml. of heparin solution (2 units per milliliter) and 0.2 ml. of the serum to be tested. To this mixture was added 0.2 ml. of 0.18 per cent calcium solution, and the coagulation time was measured. It has been known that under certain conditions the blood of animals and man demonstrates inhibitory activity against fibrinolysin (plasmin). In recent years, the studies of Sandberg, Tsitouris and collaborators15J6 have demonstrated an increase in the antifibrinolytic activity of the blood of patients with acute thrombosesand myocardial infarction. The antifibrinolytic activity of blood can be determined by several methods. The method developed by Sandberg and associates15is based on the measurement of the time required for lysis of a fibrin clot by a standard solution of fibrinolysin with and without the addition of the plasma to be tested. The method of Biezenski’” is based on the determination of the inhibitory activity of increasing dilutions of the serum to be tested on a standard solution of fibrinolysin. The normal fibri-
uf Medical
Sciences.
Moscow.
of Medical
Sciences.
Petroverigsky
II.S.S.K. per. 10, Moscow,
center.
U.S.S.R
Volrrmc Ntcmbcr
67 1
Antiheparin
and antifibrinolytic
nolytic activity of serum by this method is 11/2O to l/210 dilution. We used the method of Sandberg and collaborators. A mixture of fibrinogen solution (1 per cent), 0.2 ml., human thrombin (20 units per milliliter), 0.2 ml., plasma, 0.2 ml., and thrombolysin, 0.4 ml., was incubated in a water-bath at 37”C., and the time required for lysis of the clot was measured. The thromboIysin was made up in dilutions of 1 :lO, 1:20, and 1:40 from a stock solution with activity of 2,000 units per milliliter, so that the final activity of thrombolysin in the mixture was 80, 40, and 20 units per milliliter. This preparation loses its activity quickly; therefore, utilization should be prompt. The subjects tested were a control group of 20 healthy male donors from 35 to 55 years old, a group of 30 men from 36 to 60 years old with early manifestations of atherosclerosis, and a group of 30 persons with advanced atherosclerosis. The persons in the latter group all had frequent attacks of angina pectoris and a past history of myocardial infarction. Results
Antiheparin activity. We observed a distinct increase in the antiheparin activity of blood in the patients with atherosclerosis. Table I shows the data from the control group. In patients in the early stage of coronary atherosclerosis manifested by angina pectoris of recent onset and no evidence of myocardial infarction, there was a tendency toward an increase in the activity of antiheparin. In the majority of patients in this group the activity varied within the range of 1’50” to 3’20”. In patients in the advanced stages of atherosclerosis, with a past history of myocardial infarction, and evidence on the electrocardiogram and ballistocardiogram of coronary insufficiency, a more pronounced increase in the antiheparin activity of blood was observed. All of them had levels of activity less than 2’10” (Table II). Thus, the development of the atherosclerotic process is accompanied by an increase in the antiheparin activity of blood. Antifibrinolytic activity. In the control group of healthy donors the results were
activity in atherosclerosis
19
comparable to those of Sandberg and activity associates. The antifibrinolytic in 80 units of thrombolysin was 200 f 60 seconds; in 40 units it was 460 f 110 seconds, and in 20 units it was 730 =t 150 seconds. In the group with early atherosclerosis there were no changes in the antifibrinolytic activity of blood, in contrast to the decrease in antiheparin activity which occurred in the same group (seeTable III). With 80 units of thrombolysin, the level of activity varied from 150 to 300 seconds, and with 40 units of thrombolysin it varied from 470 to 610 seconds. However, in the group with advanced atherosclerosis, changes in the level of antifibrinolytic activity were found. In most cases the activity was more than 260 seconds in 80 units of thrombolysin, and more than 470 seconds in 40 units of thrombolysin. The activity remained at a normal level in only 7 patients of this group. Thus, the development of the atherosclerotic process is also accompanied by an increase in the antifibrinolytic activity of blood, which, concomitant with a decrease in fibrinolytic activity, could be a factor in the predisposition to thrombosis. Recently, heparin and fibrinolysin have been used with great successin the therapy of acute thromboses. It was of interest to study the level of activity of antiheparin and antifibrinolysin in the blood of patients under such therapy. Fibrinolysin (obtained from Prof. B. A. Kudriashov, Moscow University) was used in 37 cases of vascular thromboses (Table IV). The agent was used in combination with small doses of heparin (20,000 to 30,000 units per day) administered by intravenous drip over a period of 3 to 4 hours, with repeated injections when necessary on the second and third days (Table IV). Therapy with heparin and fibrinolysin was not effective in one case of thromboembolism of the pulmonary artery, and in cases of myocardial infarction over 1 day old. In our opinion, this therapy is promising in the first few hours after myocardial infarction. The necessity of combined therapy with heparin and fibrinolysin should be stressed, since this combination mimics the physiologic anticoagulant reaction to thrombosis in the organism,
2’20” 2’30” 2’40” 2’50” 3’00’ 3’10” 3’20” 3’30” 3’40” 3’50” 4’00”
1 2 3 1 3 1 3 1 2 1 2
Table I I. Antiheparin activity patients with atherosclerosis
of blood of
Antiheparilt
Later
activity
Initial
stage
3’20”
4
3’10” 3’00” 2’50” 2’40”
4 5 2 4 2 3 2 2 2 -
2’30” 2’20” 2’10” 2’00” 1’50” 1’40” 1’30” 1’20” 1’10” 1’00” 50” 40” 30”
-
.-
1 1 2 3 5 4 3 7 2 1 1
-
Average
stage
~~lq)earc~cl during treatment. The effirac! of therapy is best demonstrated by the c.hta on the levels of transaminase in the serum. Fig. 1 demonstrates that the increase in the levels of transaminase was significantly less in the patients treated with fibrinolysin. We found that during therapy there was a significant decrease in the level of activity of antiheparin in the blood. When the blood was tested one-half hour after the administration of heparin and fibrinolysin, the levels of activity were greater than 30. The low levels of antiheparin remained OII the second day of therapy. The changes in the level of antifibrinolytic activity are more complicated. Tsitouris and associates noted that the level of activity usually decreased after therapy with fibrinolysin. He observed low levels of activity, varying from 120 to 200 seconds, in the first hour after therapy in 14 of 16 cases. However, Table III. Antifibrinolytic activity of blood of patients with atherosclerosis by 80 units of thrombolysin
Initial
stage
6 6 9 4 5
Antifibrinolytic activity (sec.)
I Later
1.50-180 180-210 21Ck-240 240-270 270-300 .100-330 330-360 360-390 420-450 450-480
stage
5 2 7 8 4 1 3
2’44”
Table IV Possibly, the lack of therapeutic effect reported by Richter14 and others resulted from the use of fibrinolysin alone. In our patients who were receiving fibrinolysin and heparin, even those with severe myocardial infarction with cardiovascular collapse experienced a less complicated postinfarction period than did patients who were not receiving these agents. In some cases we observed a disappearance of the electrocardiographic signs of coronary insufficiency. Usually, cardiac pain dis-
Type
of involvement
Thromboembolism of the arteries to the lower leg and foot Thromboohlebitis of the veins of the Delvis and-calf Thromboembolism of the pulmonary artery Thromboembolism of cerebral vessels Myocardial infarction on the first day Myocardial infarction on the second day
Number of cases
10 4 3 1 15 4
Volume
Number
67 1
Antiheparin
and antijibrinolytic
on the second day, after 18 to 20 hours, the levels increased to the range of 270 to 600 seconds, the range occurring in patients with advanced atherosclerosis. To clarify the nature of the influence of fibrinolysin on inhibitory factors in the blood, we conducted investigations in 10 rabbits in which lipoid deposits in the vessels had been produced by the feeding of cholesterol for 3 months. The levels of antifibrinolysin were determined before the administration of fibrinolysin, and on the second day after administration of fibrinolysin. The levels of activity of antifibrinolysin varied from 130 to 180 seconds (with 1 unit of fibrinolysin) before the administration of fibrinolysin and increased to 330 seconds on the second day after administration. These changes, unexplained at present, support the necessity of the simultaneous administration of heparin in therapy. Discussion
In addition to pathologic changes in the vessels, another factor producing thrombosis in atherosclerosis is the failure of function of the physiologic anticoagulant system, heparin and fibrinolysin.lJO A possible explanation for the tendency to thrombosis in atherosclerosis is the decrease in the content of heparin and fibri-
activity in atherosclerosis
21
The anatomic nolysin in the blood. 3.6,9.11,12 changes in the vessels may influence the production of anticoagulants and thrombolytic agents. It is known that the formation of heparin is accomplished by mast cells, and that the fibrinolytic activity of blood depends on the vascular wall. Our observations suggest that an increase in the activity of agents counteracting heparin and fibrinolysin may be another factor in the pathogenesis of thrombosis in atherosclerosis. There is a progressive increase in the activity of these inhibitory agents with progression of the disease. They may be connected with lipid metabolism, particularly the change in lipoprotein content, observed by Greig and Runde. De Leon and associates2and Tsitouris and associate9 attach great importance to the increase in antifibrinolytic activity of blood as a pathogenic factor in thrombosis. We do not consider this to be the only factor, but it may play a role in the complex pathogenic mechanism. The change in the activity of antifibrinolysin may alter the efficacy of therapy with fibrinolysin. The activity of antiheparin and antifibrinolysin decreases during therapy with heparin and librinolysin. However, on the second day the inhibitory activity increases, necessitating repeated administration of fibrinolysin.
Fig. 1. Transaminase level of blood in patientswith myocardial infarction.
22
JIyasnikov
and Chazov
Summary
1. The activity of antiheparin and antifibrinolysin is increased during the development of atherosclerosis. 2. The increase in activity is one of the factors producing thrombosis in atherosclerosis. REFERENCES 1. Bazazyan, G. G., Sytina, N. P., Andreenko, G. V., and Kudriashov, B. A.: Depression of physiological functions of the anticoagulation system as a consequence of nutrition with atherogenic diets, Bull. Exper. Biol. & Med. 10:26, 1961. 2. De Leon, A., Bellet, S., Tsitouri, G., Leeks, I.., and Sandberg, H.: The fibrinolytic system and use of fibrinolysin in myocardial infarction, Am. J. Cardiol. 5:574, 1960. 3. Astrup, T.: Neure Aspecte in der Blutgerinnung und der Fibrinolyse und ihren Beziehungen zur Koronarthrombose and Koronarsclerose, Wien. Ztschr. inn. Med. 39:373, 1958. 4. Greig, H. B. W., and Runde, I. A.. Studies on the inhibition of fibrinolysis by lipids, Lancet 6993:461, 1957. 5. Guest, M., Daly, B., Ware, A., and Seegers, W.. A study of antifibrinolysin activity in the plasma of various animal species, J. Clin. Invest. 27~785, 1948. 6. Koshevnikova, T. L.: The investigation of fibrinolytic activity and fibrinogen of blood in atherosclerosis of coronary arteries of the heart, myocardial infarction, and during fits of stenocardia, Therap. Arch. 3:97, 1961. 7. Kudrjiashov, B. A.: Problems of blood coagulation and thromboformation, Moscow, 1960, Ed. “High School.”
S.
9.
10.
1 I.
12.
13.
14.
15.
I
16.
17.
18.
and
anWrinolytic
of blood
in putients
with
atlmresdsrosis
A. L. Myasnikov” E. I. Chazov Moscow, U.S.S.R.
I
n recent years there have been many discoveries clarifying the causes of the tendency to thrombosis in atherosclerotic blood vessels. Professor Kudriashov, of Moscow University, showed that one of the major factors in the tendency to thrombosis is a disturbance in the “physiologic anticoagulant system.” Our work and that of our collaborators has shown that these disturbances appear initially in patients with atherosclerosis. The activities of heparin and active fibrinolysin are decreased in patients with atherosclerosis. In attempting to determine the mechanism of this decrease in activity, we have investigated the activity of inhibitors of heparin and fibrinolysin-antiheparin and antifibrinolysin. Materials
and
methods
Because of the observation that the anticoagulant action of heparin added to normal plasma is diminished by the addition of aged serum, Poller13studied the possible connection of this antiheparin activity and the appearance of thrombosis. This antiheparin activity does not depend on the activity of Factor VII or the Christmas factor, and is not diminished by therapy with phenindione. A correlation was thought to exist between the antiheparin activity of serum and the appearance of thrombosis. From the Institute of Therapy. Academy Received for publication Feb. 5, 1963. *Address: Institute of Therapy, Academy
18
Antiheparin activity was assayed by the following method. To 5 ml. of venous blood was added 0.21 ml. of a mixture of 1.6 per cent potassium oxalate and 2.4 per cent ammonium oxalate. From this, 0.2 ml. of plasma was placed in a water-bath at 37°C. and mixed with 0.1 ml. of heparin solution (2 units per milliliter) and 0.2 ml. of the serum to be tested. To this mixture was added 0.2 ml. of 0.18 per cent calcium solution, and the coagulation time was measured. It has been known that under certain conditions the blood of animals and man demonstrates inhibitory activity against fibrinolysin (plasmin). In recent years, the studies of Sandberg, Tsitouris and collaborators15J6 have demonstrated an increase in the antifibrinolytic activity of the blood of patients with acute thrombosesand myocardial infarction. The antifibrinolytic activity of blood can be determined by several methods. The method developed by Sandberg and associates15is based on the measurement of the time required for lysis of a fibrin clot by a standard solution of fibrinolysin with and without the addition of the plasma to be tested. The method of Biezenski’” is based on the determination of the inhibitory activity of increasing dilutions of the serum to be tested on a standard solution of fibrinolysin. The normal fibri-
uf Medical
Sciences.
Moscow.
of Medical
Sciences.
Petroverigsky
II.S.S.K. per. 10, Moscow,
center.
U.S.S.R
Volrrmc Ntcmbcr
67 1
Antiheparin
and antifibrinolytic
nolytic activity of serum by this method is 11/2O to l/210 dilution. We used the method of Sandberg and collaborators. A mixture of fibrinogen solution (1 per cent), 0.2 ml., human thrombin (20 units per milliliter), 0.2 ml., plasma, 0.2 ml., and thrombolysin, 0.4 ml., was incubated in a water-bath at 37”C., and the time required for lysis of the clot was measured. The thromboIysin was made up in dilutions of 1 :lO, 1:20, and 1:40 from a stock solution with activity of 2,000 units per milliliter, so that the final activity of thrombolysin in the mixture was 80, 40, and 20 units per milliliter. This preparation loses its activity quickly; therefore, utilization should be prompt. The subjects tested were a control group of 20 healthy male donors from 35 to 55 years old, a group of 30 men from 36 to 60 years old with early manifestations of atherosclerosis, and a group of 30 persons with advanced atherosclerosis. The persons in the latter group all had frequent attacks of angina pectoris and a past history of myocardial infarction. Results
Antiheparin activity. We observed a distinct increase in the antiheparin activity of blood in the patients with atherosclerosis. Table I shows the data from the control group. In patients in the early stage of coronary atherosclerosis manifested by angina pectoris of recent onset and no evidence of myocardial infarction, there was a tendency toward an increase in the activity of antiheparin. In the majority of patients in this group the activity varied within the range of 1’50” to 3’20”. In patients in the advanced stages of atherosclerosis, with a past history of myocardial infarction, and evidence on the electrocardiogram and ballistocardiogram of coronary insufficiency, a more pronounced increase in the antiheparin activity of blood was observed. All of them had levels of activity less than 2’10” (Table II). Thus, the development of the atherosclerotic process is accompanied by an increase in the antiheparin activity of blood. Antifibrinolytic activity. In the control group of healthy donors the results were
activity in atherosclerosis
19
comparable to those of Sandberg and activity associates. The antifibrinolytic in 80 units of thrombolysin was 200 f 60 seconds; in 40 units it was 460 f 110 seconds, and in 20 units it was 730 =t 150 seconds. In the group with early atherosclerosis there were no changes in the antifibrinolytic activity of blood, in contrast to the decrease in antiheparin activity which occurred in the same group (seeTable III). With 80 units of thrombolysin, the level of activity varied from 150 to 300 seconds, and with 40 units of thrombolysin it varied from 470 to 610 seconds. However, in the group with advanced atherosclerosis, changes in the level of antifibrinolytic activity were found. In most cases the activity was more than 260 seconds in 80 units of thrombolysin, and more than 470 seconds in 40 units of thrombolysin. The activity remained at a normal level in only 7 patients of this group. Thus, the development of the atherosclerotic process is also accompanied by an increase in the antifibrinolytic activity of blood, which, concomitant with a decrease in fibrinolytic activity, could be a factor in the predisposition to thrombosis. Recently, heparin and fibrinolysin have been used with great successin the therapy of acute thromboses. It was of interest to study the level of activity of antiheparin and antifibrinolysin in the blood of patients under such therapy. Fibrinolysin (obtained from Prof. B. A. Kudriashov, Moscow University) was used in 37 cases of vascular thromboses (Table IV). The agent was used in combination with small doses of heparin (20,000 to 30,000 units per day) administered by intravenous drip over a period of 3 to 4 hours, with repeated injections when necessary on the second and third days (Table IV). Therapy with heparin and fibrinolysin was not effective in one case of thromboembolism of the pulmonary artery, and in cases of myocardial infarction over 1 day old. In our opinion, this therapy is promising in the first few hours after myocardial infarction. The necessity of combined therapy with heparin and fibrinolysin should be stressed, since this combination mimics the physiologic anticoagulant reaction to thrombosis in the organism,
2’20” 2’30” 2’40” 2’50” 3’00’ 3’10” 3’20” 3’30” 3’40” 3’50” 4’00”
1 2 3 1 3 1 3 1 2 1 2
Table I I. Antiheparin activity patients with atherosclerosis
of blood of
Antiheparilt
Later
activity
Initial
stage
3’20”
4
3’10” 3’00” 2’50” 2’40”
4 5 2 4 2 3 2 2 2 -
2’30” 2’20” 2’10” 2’00” 1’50” 1’40” 1’30” 1’20” 1’10” 1’00” 50” 40” 30”
-
.-
1 1 2 3 5 4 3 7 2 1 1
-
Average
stage
~~lq)earc~cl during treatment. The effirac! of therapy is best demonstrated by the c.hta on the levels of transaminase in the serum. Fig. 1 demonstrates that the increase in the levels of transaminase was significantly less in the patients treated with fibrinolysin. We found that during therapy there was a significant decrease in the level of activity of antiheparin in the blood. When the blood was tested one-half hour after the administration of heparin and fibrinolysin, the levels of activity were greater than 30. The low levels of antiheparin remained OII the second day of therapy. The changes in the level of antifibrinolytic activity are more complicated. Tsitouris and associates noted that the level of activity usually decreased after therapy with fibrinolysin. He observed low levels of activity, varying from 120 to 200 seconds, in the first hour after therapy in 14 of 16 cases. However, Table III. Antifibrinolytic activity of blood of patients with atherosclerosis by 80 units of thrombolysin
Initial
stage
6 6 9 4 5
Antifibrinolytic activity (sec.)
I Later
1.50-180 180-210 21Ck-240 240-270 270-300 .100-330 330-360 360-390 420-450 450-480
stage
5 2 7 8 4 1 3
2’44”
Table IV Possibly, the lack of therapeutic effect reported by Richter14 and others resulted from the use of fibrinolysin alone. In our patients who were receiving fibrinolysin and heparin, even those with severe myocardial infarction with cardiovascular collapse experienced a less complicated postinfarction period than did patients who were not receiving these agents. In some cases we observed a disappearance of the electrocardiographic signs of coronary insufficiency. Usually, cardiac pain dis-
Type
of involvement
Thromboembolism of the arteries to the lower leg and foot Thromboohlebitis of the veins of the Delvis and-calf Thromboembolism of the pulmonary artery Thromboembolism of cerebral vessels Myocardial infarction on the first day Myocardial infarction on the second day
Number of cases
10 4 3 1 15 4
Volume
Number
67 1
Antiheparin
and antijibrinolytic
on the second day, after 18 to 20 hours, the levels increased to the range of 270 to 600 seconds, the range occurring in patients with advanced atherosclerosis. To clarify the nature of the influence of fibrinolysin on inhibitory factors in the blood, we conducted investigations in 10 rabbits in which lipoid deposits in the vessels had been produced by the feeding of cholesterol for 3 months. The levels of antifibrinolysin were determined before the administration of fibrinolysin, and on the second day after administration of fibrinolysin. The levels of activity of antifibrinolysin varied from 130 to 180 seconds (with 1 unit of fibrinolysin) before the administration of fibrinolysin and increased to 330 seconds on the second day after administration. These changes, unexplained at present, support the necessity of the simultaneous administration of heparin in therapy. Discussion
In addition to pathologic changes in the vessels, another factor producing thrombosis in atherosclerosis is the failure of function of the physiologic anticoagulant system, heparin and fibrinolysin.lJO A possible explanation for the tendency to thrombosis in atherosclerosis is the decrease in the content of heparin and fibri-
activity in atherosclerosis
21
The anatomic nolysin in the blood. 3.6,9.11,12 changes in the vessels may influence the production of anticoagulants and thrombolytic agents. It is known that the formation of heparin is accomplished by mast cells, and that the fibrinolytic activity of blood depends on the vascular wall. Our observations suggest that an increase in the activity of agents counteracting heparin and fibrinolysin may be another factor in the pathogenesis of thrombosis in atherosclerosis. There is a progressive increase in the activity of these inhibitory agents with progression of the disease. They may be connected with lipid metabolism, particularly the change in lipoprotein content, observed by Greig and Runde. De Leon and associates2and Tsitouris and associate9 attach great importance to the increase in antifibrinolytic activity of blood as a pathogenic factor in thrombosis. We do not consider this to be the only factor, but it may play a role in the complex pathogenic mechanism. The change in the activity of antifibrinolysin may alter the efficacy of therapy with fibrinolysin. The activity of antiheparin and antifibrinolysin decreases during therapy with heparin and librinolysin. However, on the second day the inhibitory activity increases, necessitating repeated administration of fibrinolysin.
Fig. 1. Transaminase level of blood in patientswith myocardial infarction.
22
JIyasnikov
and Chazov
Summary
1. The activity of antiheparin and antifibrinolysin is increased during the development of atherosclerosis. 2. The increase in activity is one of the factors producing thrombosis in atherosclerosis. REFERENCES 1. Bazazyan, G. G., Sytina, N. P., Andreenko, G. V., and Kudriashov, B. A.: Depression of physiological functions of the anticoagulation system as a consequence of nutrition with atherogenic diets, Bull. Exper. Biol. & Med. 10:26, 1961. 2. De Leon, A., Bellet, S., Tsitouri, G., Leeks, I.., and Sandberg, H.: The fibrinolytic system and use of fibrinolysin in myocardial infarction, Am. J. Cardiol. 5:574, 1960. 3. Astrup, T.: Neure Aspecte in der Blutgerinnung und der Fibrinolyse und ihren Beziehungen zur Koronarthrombose and Koronarsclerose, Wien. Ztschr. inn. Med. 39:373, 1958. 4. Greig, H. B. W., and Runde, I. A.. Studies on the inhibition of fibrinolysis by lipids, Lancet 6993:461, 1957. 5. Guest, M., Daly, B., Ware, A., and Seegers, W.. A study of antifibrinolysin activity in the plasma of various animal species, J. Clin. Invest. 27~785, 1948. 6. Koshevnikova, T. L.: The investigation of fibrinolytic activity and fibrinogen of blood in atherosclerosis of coronary arteries of the heart, myocardial infarction, and during fits of stenocardia, Therap. Arch. 3:97, 1961. 7. Kudrjiashov, B. A.: Problems of blood coagulation and thromboformation, Moscow, 1960, Ed. “High School.”
S.
9.
10.
1 I.
12.
13.
14.
15.
I
16.
17.
18.