Oral
Anticoagulation for Secondary Prevention After Myocardial Infarction With Special Reference to the Warfarin Re-Infarction Study Syed M. Jafri, Mihai
In 1915, JamesHerrick described the clinical syndromeof a heart attack causedby the thrombotic occlusionof a coronary artery associatedwith survival of the patient.’ Thrombosisof the coronary artery was proposed as the mechanismby which the heart attack or myocardial infarction occurred. Theseobservationsled to the development of a numberof therapeutic interventions aimedat preventing thrombosis.Irving Wright was the first to test anticoagulanttreatment in acute myocardial infarction.* Data wascollected from 800 patients; 368 patients who were admitted on even days and received conventional therapy constituted the control group, and 432 patients who were admitted on odd days received heparin followed by dicumoral for at least 30 days. Using relatively primitive clinical trial methodology, this study suggesteda short-term mortality benefit and a lower incidence of thromboembolismassociatedwith anticoagulanttherapy. The pathophysiologicalimportance of coronary thrombosiswas seriously challengedin the late 1950sand 1960s basedprimarily on the lack of autopsy evidence of thrombi in patients dying of suddencardiac death? It was assumedthat all suddendeathswere due to myocardial infarction, and autopsy studiesin thesepatientsshowedsevere coronary atherosclerosisbut not coronary thrombi.4 A 1969 review of the methodologicaldefects, including patient selectionand lack of appropriate controlsof the earlier trials, alsoled to a lack of enthusiasmfor this mode of therapy? The seminalobservationsof DeWood and associatesin 1980,6providing angiographicevidenceof intracoronary thrombus coupled with recent advancesin the understandingof platelet activation and the clotting system,have reestablishedcoronary thrombosisas the most commoncauseof myocardial infarction. These developmentshave led, in turn, to the developmentof new Progress
in Cardiovascular
Diseases,
Vol XXXIV,
Gheorghiade,
and Sidney
Goldstein
therapeutic strategiesbasedon thrombolysisand anticoagulation. Death, reinfarction, andthromboembolism are three major complications in survivors of an acute myocardial infarction. Fibrin-containing mural thrombus is a commonfinding in autopsy studiesof patientsdying from an acute transmural myocardial infarction.’ The overall incidence of mural thrombusas detected on autopsy and by two-dimensionalechocardiography is between 17% and 20% in acute myocardial infarction.*-” Patientswith anterior and apicalinfarctions are at a particularly high risk of developingmural thrombi.“.I5 Most systemicemboli occurwithin the first 2 to 3 monthsand particularly within the first 10 days. Cerebral embolismoccurred in 2% to 4% of untreated patients following myocardial infarction. Approximately two thirds of theseembolicevents led to death or seriousmorbidity.
which the dose of oral anticoagulant did not increasethe prothrombin time. During a 3-year follow-up, mortality in the treatment group was 15%, compared with 21% in the control group. Recurrent myocardial infarction in the treated group was21% comparedwith 40% in controls.Thromboembolicepisodeswere also less frequent in patients who receivedtherapeutic anticoagulants (P < 0.001). Hemorrhagic complicationswere significantly more frequent and occurred in 41% of patients receiving therapeutic anticoagulants versus 5.3% in the controls (p < .OOl).Thus, in this study, potential benefit of oral anticoagulanttherapy wasoutweighedby the significant risk of bleedingcomplications. The Veterans Administration Cooperative Study (1965)of 878patients 60 yearsor older who hadreceivedanticoagulationafter myocardialinfarction’8*‘9 wasdesignedto discontinueanticoagulation in one half of the patients and place them on a placebo instead of LONG-TERM ANTICOAGULANT their anticoagulant. Mortality rate at THERAPY AFTER MYOCARDIAL the 3-year follow-up period was15% in INFARCTION patients maintained on anticoagulant The rationale for the long-term use therapy and 24% in the control group. of anticoagulantsin survivors of acute After this point, relatively similarmormyocardialinfarction is twofold: (1) to tality was noted, and at the end of 7 prevent recurrence of coronary artery years, mortality rates were similar. complications thrombosiswith the expectation that Thromboembolic this may prevent reinfarction and re- (P < .05) and recurrent myocardialinduce mortality and (2) to potentially farction (P = NS) were again lessfredecreasecatastrophicembolicevents. quent, whereasbleedingcomplications The role of anticoagulantsin the weremore frequent in the anticoagulalong-termmanagementof the postmyo- tion group (P < .OOl).This study also cardial infarction patient hasbeen ex- noted that therapy with anticoagulants amined in a number of studies. The wasmore effective in patientswho had results of 12 long-term randomized trials, each involving at least 200 paFrom the Heart and Vascular. Institute, tients since 1960, are summarizedin Medicine, Hemy Table 1. Details of seven large trials Division of Cardiovascular will be reviewedwith specialreference Ford Hospital, Detroit, MI. Address reprint requests to Syed M. Jajki, to the Warfarin Reinfarction Study.16 MD, Heart and Vascular Institute, Division of The Medical ResearchCouncil Trial Cardiovascular Medicine, Henry Ford Hospi(1964)randomized383 patients 4 to 6 tal, 2799 W Grand Blvd, Detroit, MI 48202. weeks after their myocardial infarcCopyright 0 1992 by WB. Saunders Comtion” to a high-dose anticoagulant wny group or a low-dosecontrol group in 0033-0620/92/3405-0002$5.002$5.00/0
No 5 (March/April),
1992:
pp 317-324
317
S/C heparin, small-dose phenpro-
Open
Open
German Austrian Trialm 1980 Lovell et alzJ 1967
1990
WARIS”
Placebo
(651
Abbreviations: I, intervention; C, controls; ASA, acetylsalicylic *All treated with anticoagulants before randomization. tNot including 78 patients who withdrew.
blind
Open
1982
EPSIM’9
Double
Placebo
Double
ASA
Placebo
Open
mg)
or placebo
coumon
Placebo
Sorensen et alz4 1969 Sixty Plus’* 1980
blind
ASA
Open
VA Cooperative Study’B 1969
1 mg phenindione
blind
Single
Medical Research Council Trial” 1964
Placebo
blind
Single
VA Cooperative Study” 1973 Loeliger et alz5 1967
Randomized
COlltrOl
Double
Placebo
Open
VA Cooperative Study’a 1965
blind
Placebo
Open
Placebo
1. Long-Term
et alzO
Harvald 1962
Trial
TVP~ of Blind
Table
t
lnlervention
(~296
phenpro-
Patients)
acid.
coagulants Warfarin
Alenocoumaxin, phenprocoumon Various oral
Dicourmarol
Phenprocoumon
Phenprocoumon
anti-
Bishydroxycoumadin, sodium watfarin
Phenindione
warfarin Phenprocoumon
Bishydroxycoumadin, sodium warfarin Heparin, sodium
Dicoumarol, coumon
Trials
1960
1,214
1,303
878 ( > 60 yrs)
278
412
946
747
326t
267
6 mos*
2 wks
27 d
11.4d
Before
42 d
21 d*
6 wks’
> 1 yr*
72 h
21 d*
747
1,037
Before discharge*
Entry Window
of Oral Anticoagulants
315
No. of Patients
Since
37 mos
15
10
7.6
2 yrs
29 mos
9.5
2 yrs
18.5
12.2
2 yrs 3 yrs
40
15
4.8
9.6
22
21
I
20
11
13.4
19
22
10.4
42
2.1
7.2
11.2
27
24
C
Surviving Mortality WI
7 yrs
3 yrs
16 mos
28 d
5 yrs
4 yrs
Follow-UD
in Patients
13
3
5.7
5.0
6.7
5.0
15.6
20.5
1.2
2
13
35
I
Reinfarciion (“4
Mvocardial
20
5
15.9
19
9.8
8.1
20.9
39.9
8.7
4
22
39
C
?
3
?
?
5.0
1.1
0.6
3.9
4.3
0
4
7
I
C
7
?
?
19
4.0
2.3
7.7
1.0
3.2
12
?
16
Embolic Events wd
Infarction
.05
events
only
.Ol
< .05
None
None
None
-
Only for embolic events
creased mortality during 1st year
< .OOl from reinfarction; de-
f
0.20
-
0.15
-
0.10
-
z a
0
200
400
600
600
1000
1200
1400
1600
1600
2000
Days
evidence for a salutary effect of warfarin on mortality and reinfarction in survivors of an acute myocardial infarction. The lower frequency of cerebrovascular events in the warfarin group suggests that the reduction in mortality may also be due to a decrease in the frequency of the fatal thromboembolic events. THEORETIC
CONSIDERATIONS
Antiplatelet and anticoagulanttherapy have separateand distinct effects on the hemostaticsystem.The effects of combined use of these agentsare theoretically additive, (in regards to) decreasingfatal and nonfatal cardiac eventsmediatedby platelet- or coagulation cascade-initiated thrombosis. However, given the potential for a higher incidenceof bleedingcomplications, combinationtherapy may not be suitable for all patients. It would be useful if indicesdefining the degreeof activation of platelet- and coagulation-
mediatedthrombosiscould be defined, thus permitting the development of “customized” therapeutic regimens basedon platelet and coagulationprofiles of individual patients. Antiplatelet and anticoagulanttherapy, both in the acute and long-term managementof patients with an acute myocardial infarction, have recently been reevaluatedin a numberof studies.Severalprevioustrials assessed the role of antiplatelet therapy for secondary prevention.““’ Recently, data from the ISIS-2 trial suggeststhat therapy with aspirin, when initiated early after the onsetof an acutemyocardialinfarction, hasboth an independentand an additive effect to thrombolysisin reducing mortality?3Meta-analysisof 31randomizedtrials of a variety of antiplatelet therapies that included almost 29,000 piltients indicated an overall decreasein vascular mortality of approximately 15%and of 30%for nonfatal vasculareventsincluding strokeand
0
400
Fig 1. Cumulative rates of death causes according to original treatment ment. (Reprinted with permission.‘*)
from all essign-
myocardial infarction.14Data from the recently published WARIS trial indicates it would be appropriate to consider the useof oral anticoagulationin all survivors of an acute myocardial infarction.13 However, it should be noted that the WARIS trial was conducted during a time period when the use of thrombolytic therapy was not widespreadand the efficacy of aspirin therapy wasnot well established.Thus, a well-designedcomparative study assessingaspirinversuswarfarin for secondary prevention after myocardialinfarction is needed to determine the relative efficacy and safety of these drugs in secondary prevention after myocardialinfarction. ANTICOAGULANT THERAPY THE POSTMYOCARDIAL INFARCTION PATIENT
IN
Anticoagulation in the postmyocardial infarction patient shouldbeconsidered becauseit potentially may limit
800
1200
Days
1800
2000
CLINICAL
TRIALS
REVIEW
both primary ischemic cardiac events and thromboembolic complications. Based on current information, routine use of oral anticoagulation should be considered for all survivors of a myocardial infarction. It should also be noted that the targeted therapeutic range for oral anticoagulant therapy in North America was not modified when the less-sensitive commercial thromboplastins were introduced, thus leading to an inadvertent increase in the degree of anticoagulation obtained?5 A lower incidence of bleeding complications should be expected with oral anticoagulant therapy when administered in dosages presently considered as being therapeutic. Despite the impressive results shown by the WARIS study and the lower rate of bleeding complications in this study due to the appropriate range of anticoagulation therapy, there continues to be resistance to use anticoagulant therapy in survivors of myocardial infarction. Appropriate use of oral anticoagulation can impact the natural history of postmyocardial infarction patients. According to the recommendations of the American College of Cardiology (ACC) and the American Heart Association (AHA), oral anticoagulant therapy is warranted in postmyocardial infarction patients at high risk of thromboembolic events, those with an anterior or apical infarct with or without a documented mural thrombus.j6 Therapy should be continued for at least 3 months after a myocardial infarction. Long-term oral anticoagulant therapy should be strongly considered in patients with a diffusely dilated and poorly contracting left ventricle. The target prothrombin time recommended by ACC and AHA guidelines is between 1.3 and 1.5 times control. For patients at high risk for thromboembolism and those with significant left ventricular dysfunction (left ventricular ejection fraction 35%, therapy with aspirin or warfarin can be used. Given the lower risk of bleeding complications, convenience of dosing, and follow-up, aspirin remains an attractive option for these low-risk patients.
321
REFERENCES 1. Herrick JB: Clinical features of sudden obstruction of the coronary arteries. JAMA 59:2015-2020,1912 2. Wright IS, Marple CD, Beth DF: Report of the Committee for the Evaluation of Anticoagulants in the Treatment of Coronary Thrombosis with Myocardial Infarction. Am Heart J 36:801-815,1948 3. Deykin D: Antithrombotic therapy in historical perspective. Am J Cardiol65:6:2C6C, 1990 4. Mitchell JRA: Clinical events resulting from thrombus formation. Br Med Bull 34:103-106,1978 5. Gifford RG, Feinstein AR: A critique of methodology in studies of anticoagulant therapy for acute myocardial infarction. N Engl J Med 280:351-357, 1969 6. DeWood ME, Spores J, Notske R: Prevalence of total coronary occlusion during the early hours of transmural myocardial infarction. N Engl J Med 303:897, 1980 7. Davis MJ, Woolf N, Robertson WB: Pathology of acute myocardial infarction with particular reference to occlusive coronary thrombi. Br Heart J 38:659-664,1976 8. Weinrich DJ, Burke JF, Pauletto FJ: Left ventricular mural thrombi complicating acute myocardial infarction: Long term follow-up; with serial echocardiography. Ann Intern Med 100:789-794,1984 9. AsingerRW, Mike11 FL, Elsperger T. et al: Incidence of left ventricular thrombosis after acute myocardial infarction. N Engl J Med 305:297-302, 1981 10. Jordan RA, Miller RD, Edwards JE, et al: Thromboembolism in acute and in healed myocardial infarction. 1. Intracardiac mural thrombosis. Circulation 6:1-6, 1952 11. Freidman MF, Carlson K, Marcus FI, et al: Clinical correlations in patients with acute myocardial infarction and left ventricular thrombus detected by two-dimension echocardiography. Am J Med 72:894-898, 1982 12. Keating EC, Gross SA, Schalmowitz RA, et al: Mural thrombi in myocardial infarction: Prospective evaluation of twodimensional echocardiography. Am J Med 74:989-9951983 13. Johannessen KA, Nordrehaug JE, von der Lippe G: Left ventricular thrombosis and cerebrovascular accident in acute myocardial infarction. Br Heart J 51553-556, 1984 14. Eshowitz MD, Kellerman DJ, Smith 0, et al: Detection of active left ventricular thrombosis during acute myocardial infarction using Indium-111 platelet scintigraphy. Chest 86:35-39,1984 15. Komrad MS, Coffey CE. Coffey KS, et al: Myocardial infarction and stroke. Neurology 34:1403-1409,1984 16. Smith P, Arnesen H, Holme I: The
effect of warfarin on mortality and reinfarc. tion after myocardial infarction. N Engl J Med 323:147-152, 1990 17. Second Report of the Working Party on Anticoagulant Therapy in Coronary Thrombosis to the Medical Research Council: An assessment on long-term anticoagu lation after myocardial infarction. Br Med. 2:837-843, 1964 18. United States Veterans Administra tion: Long term anticoagulant therapy afte, myocardial infarction. Final Report of the Veterans Administration Cooperative Study JAMA 193:157-162,1965 19. Elbert RV, Borden CW, Hipp HR Long term anticoagulant therapy after mYo cardial infarction. Final report of the Veter. ans Administration Cooperative Study JAMA 207:2263-2268,1969 20. Breddin K, Loew D, Lechner K, et aI The German-Austrian Trial: A comparisolof acetylsalicylic acid, placebo and phenprocoumon in secondary prevention of myocar. dial infarction. Circulation 62:63-72, 1981 (SUPPl5) 21. Sixty Plus Reinfarction Study Kc search Group: A double blind trial to asses’ long term oral anticoagulant therapy ir elderly patients after myocardial infarction Lancet 2:989-993, 1980 22. The EPSIM Research Group: A controlled comparison of aspirin and nral anticoagulants in prevention of death after myocardial infarction. N Engl J Med 307:71)1 708,1982 23. Harvald B, Hilden T, Lund E: Longterm anticoagulant therapy after myocardial infarction. Lancet 2:626-630. 1962 24. Veterans Administration Hospital Investigators: Anticoagulants in acute myoc,lir dial infarction. Results of a cooperative clinical trial. JAMA 225:7:724-730, 1973 25. Loeliger EA, Hansen A, Kroes F. et al: A double-blind trial of long-term anticoagulant treatment after myocardial infarction. Acta Med Stand 182:549-564, 1967 26. Love11 RRH, Denborough MA. Nestel PJ. et al: A controlled trial of long-term treatment with anticoagulants after mYocardial infarction in 412 male patients. Mrd J Aust 2:97-104, 1967 27. Sorensen OH, Friis T. Jorgensen W. et al: Anticoagulant treatment of acute coronary thrombosis. Acta Med Stand 185: 65-72,1969 28. Elwood PC. Cochrane AL, Burr ML, et al: A randomized controlled trial of acetY1 salicylic acid in the secondary prevention of mortality from myocardial infarctionBr Med J 1:436-440,1974 29. Elmwood PC, Sweetnam PM: AWin and secondary mortality after rny()~al~~ial infarction. Lancet 2:1313-1315, 1979 30. Aspirin Myocardial Infarction Study Research Group: A randomized. controlled trial of aspirin in persons recovered from
322
myocardial infarction. JAMA 243:661-669, 1980 31. The Persantine-Aspirin Reinfarction Trial Research Group: Persantine and aspirin in coronary heart disease. Circulation 62:449-462,198O 32. Klint CR, Rriatterud GL, Stamler J, et al: Persantine-Aspirin Reinfarction Study. Part II. Secondary coronary prevention with
JAFRI,
persantine and aspirin. J Am Co11 Cardiol 7:251-269,1986 33. ISIS-2 Collaborative Group: Randomized trial of IV streptokinase, oral aspirin, both or neither group among 17,187 cases of suspected acute myocardial infarction. Lancet 2:349-360,1988 34. Antiplatelet Trialists Collaboration: Secondary prevention of vascular disease by
GHEORGHIADE,
AND
GOLDSTEIN
prolonged antiplatelet therapy. Br Med J 296:320-331,1988 35. Hirsh J: Oral anticoagulant drugs. N Engl J Med 26:1865-18751991 36. ACC/AHA Guidelines for the Early Management of Patients With Acute Myocardial Infarction. Circulation 82:2:664-707, 1990
Anticoagulation for Secondary Prevention After Myocardial Infarction With Special Reference to the Warfarin Re-Infarction Study Syed M. Jafri, Mihai
In 1915, JamesHerrick described the clinical syndromeof a heart attack causedby the thrombotic occlusionof a coronary artery associatedwith survival of the patient.’ Thrombosisof the coronary artery was proposed as the mechanismby which the heart attack or myocardial infarction occurred. Theseobservationsled to the development of a numberof therapeutic interventions aimedat preventing thrombosis.Irving Wright was the first to test anticoagulanttreatment in acute myocardial infarction.* Data wascollected from 800 patients; 368 patients who were admitted on even days and received conventional therapy constituted the control group, and 432 patients who were admitted on odd days received heparin followed by dicumoral for at least 30 days. Using relatively primitive clinical trial methodology, this study suggesteda short-term mortality benefit and a lower incidence of thromboembolismassociatedwith anticoagulanttherapy. The pathophysiologicalimportance of coronary thrombosiswas seriously challengedin the late 1950sand 1960s basedprimarily on the lack of autopsy evidence of thrombi in patients dying of suddencardiac death? It was assumedthat all suddendeathswere due to myocardial infarction, and autopsy studiesin thesepatientsshowedsevere coronary atherosclerosisbut not coronary thrombi.4 A 1969 review of the methodologicaldefects, including patient selectionand lack of appropriate controlsof the earlier trials, alsoled to a lack of enthusiasmfor this mode of therapy? The seminalobservationsof DeWood and associatesin 1980,6providing angiographicevidenceof intracoronary thrombus coupled with recent advancesin the understandingof platelet activation and the clotting system,have reestablishedcoronary thrombosisas the most commoncauseof myocardial infarction. These developmentshave led, in turn, to the developmentof new Progress
in Cardiovascular
Diseases,
Vol XXXIV,
Gheorghiade,
and Sidney
Goldstein
therapeutic strategiesbasedon thrombolysisand anticoagulation. Death, reinfarction, andthromboembolism are three major complications in survivors of an acute myocardial infarction. Fibrin-containing mural thrombus is a commonfinding in autopsy studiesof patientsdying from an acute transmural myocardial infarction.’ The overall incidence of mural thrombusas detected on autopsy and by two-dimensionalechocardiography is between 17% and 20% in acute myocardial infarction.*-” Patientswith anterior and apicalinfarctions are at a particularly high risk of developingmural thrombi.“.I5 Most systemicemboli occurwithin the first 2 to 3 monthsand particularly within the first 10 days. Cerebral embolismoccurred in 2% to 4% of untreated patients following myocardial infarction. Approximately two thirds of theseembolicevents led to death or seriousmorbidity.
which the dose of oral anticoagulant did not increasethe prothrombin time. During a 3-year follow-up, mortality in the treatment group was 15%, compared with 21% in the control group. Recurrent myocardial infarction in the treated group was21% comparedwith 40% in controls.Thromboembolicepisodeswere also less frequent in patients who receivedtherapeutic anticoagulants (P < 0.001). Hemorrhagic complicationswere significantly more frequent and occurred in 41% of patients receiving therapeutic anticoagulants versus 5.3% in the controls (p < .OOl).Thus, in this study, potential benefit of oral anticoagulanttherapy wasoutweighedby the significant risk of bleedingcomplications. The Veterans Administration Cooperative Study (1965)of 878patients 60 yearsor older who hadreceivedanticoagulationafter myocardialinfarction’8*‘9 wasdesignedto discontinueanticoagulation in one half of the patients and place them on a placebo instead of LONG-TERM ANTICOAGULANT their anticoagulant. Mortality rate at THERAPY AFTER MYOCARDIAL the 3-year follow-up period was15% in INFARCTION patients maintained on anticoagulant The rationale for the long-term use therapy and 24% in the control group. of anticoagulantsin survivors of acute After this point, relatively similarmormyocardialinfarction is twofold: (1) to tality was noted, and at the end of 7 prevent recurrence of coronary artery years, mortality rates were similar. complications thrombosiswith the expectation that Thromboembolic this may prevent reinfarction and re- (P < .05) and recurrent myocardialinduce mortality and (2) to potentially farction (P = NS) were again lessfredecreasecatastrophicembolicevents. quent, whereasbleedingcomplications The role of anticoagulantsin the weremore frequent in the anticoagulalong-termmanagementof the postmyo- tion group (P < .OOl).This study also cardial infarction patient hasbeen ex- noted that therapy with anticoagulants amined in a number of studies. The wasmore effective in patientswho had results of 12 long-term randomized trials, each involving at least 200 paFrom the Heart and Vascular. Institute, tients since 1960, are summarizedin Medicine, Hemy Table 1. Details of seven large trials Division of Cardiovascular will be reviewedwith specialreference Ford Hospital, Detroit, MI. Address reprint requests to Syed M. Jajki, to the Warfarin Reinfarction Study.16 MD, Heart and Vascular Institute, Division of The Medical ResearchCouncil Trial Cardiovascular Medicine, Henry Ford Hospi(1964)randomized383 patients 4 to 6 tal, 2799 W Grand Blvd, Detroit, MI 48202. weeks after their myocardial infarcCopyright 0 1992 by WB. Saunders Comtion” to a high-dose anticoagulant wny group or a low-dosecontrol group in 0033-0620/92/3405-0002$5.002$5.00/0
No 5 (March/April),
1992:
pp 317-324
317
S/C heparin, small-dose phenpro-
Open
Open
German Austrian Trialm 1980 Lovell et alzJ 1967
1990
WARIS”
Placebo
(651
Abbreviations: I, intervention; C, controls; ASA, acetylsalicylic *All treated with anticoagulants before randomization. tNot including 78 patients who withdrew.
blind
Open
1982
EPSIM’9
Double
Placebo
Double
ASA
Placebo
Open
mg)
or placebo
coumon
Placebo
Sorensen et alz4 1969 Sixty Plus’* 1980
blind
ASA
Open
VA Cooperative Study’B 1969
1 mg phenindione
blind
Single
Medical Research Council Trial” 1964
Placebo
blind
Single
VA Cooperative Study” 1973 Loeliger et alz5 1967
Randomized
COlltrOl
Double
Placebo
Open
VA Cooperative Study’a 1965
blind
Placebo
Open
Placebo
1. Long-Term
et alzO
Harvald 1962
Trial
TVP~ of Blind
Table
t
lnlervention
(~296
phenpro-
Patients)
acid.
coagulants Warfarin
Alenocoumaxin, phenprocoumon Various oral
Dicourmarol
Phenprocoumon
Phenprocoumon
anti-
Bishydroxycoumadin, sodium watfarin
Phenindione
warfarin Phenprocoumon
Bishydroxycoumadin, sodium warfarin Heparin, sodium
Dicoumarol, coumon
Trials
1960
1,214
1,303
878 ( > 60 yrs)
278
412
946
747
326t
267
6 mos*
2 wks
27 d
11.4d
Before
42 d
21 d*
6 wks’
> 1 yr*
72 h
21 d*
747
1,037
Before discharge*
Entry Window
of Oral Anticoagulants
315
No. of Patients
Since
37 mos
15
10
7.6
2 yrs
29 mos
9.5
2 yrs
18.5
12.2
2 yrs 3 yrs
40
15
4.8
9.6
22
21
I
20
11
13.4
19
22
10.4
42
2.1
7.2
11.2
27
24
C
Surviving Mortality WI
7 yrs
3 yrs
16 mos
28 d
5 yrs
4 yrs
Follow-UD
in Patients
13
3
5.7
5.0
6.7
5.0
15.6
20.5
1.2
2
13
35
I
Reinfarciion (“4
Mvocardial
20
5
15.9
19
9.8
8.1
20.9
39.9
8.7
4
22
39
C
?
3
?
?
5.0
1.1
0.6
3.9
4.3
0
4
7
I
C
7
?
?
19
4.0
2.3
7.7
1.0
3.2
12
?
16
Embolic Events wd
Infarction
.05
events
only
.Ol
< .05
None
None
None
-
Only for embolic events
creased mortality during 1st year
< .OOl from reinfarction; de-
f
0.20
-
0.15
-
0.10
-
z a
0
200
400
600
600
1000
1200
1400
1600
1600
2000
Days
evidence for a salutary effect of warfarin on mortality and reinfarction in survivors of an acute myocardial infarction. The lower frequency of cerebrovascular events in the warfarin group suggests that the reduction in mortality may also be due to a decrease in the frequency of the fatal thromboembolic events. THEORETIC
CONSIDERATIONS
Antiplatelet and anticoagulanttherapy have separateand distinct effects on the hemostaticsystem.The effects of combined use of these agentsare theoretically additive, (in regards to) decreasingfatal and nonfatal cardiac eventsmediatedby platelet- or coagulation cascade-initiated thrombosis. However, given the potential for a higher incidenceof bleedingcomplications, combinationtherapy may not be suitable for all patients. It would be useful if indicesdefining the degreeof activation of platelet- and coagulation-
mediatedthrombosiscould be defined, thus permitting the development of “customized” therapeutic regimens basedon platelet and coagulationprofiles of individual patients. Antiplatelet and anticoagulanttherapy, both in the acute and long-term managementof patients with an acute myocardial infarction, have recently been reevaluatedin a numberof studies.Severalprevioustrials assessed the role of antiplatelet therapy for secondary prevention.““’ Recently, data from the ISIS-2 trial suggeststhat therapy with aspirin, when initiated early after the onsetof an acutemyocardialinfarction, hasboth an independentand an additive effect to thrombolysisin reducing mortality?3Meta-analysisof 31randomizedtrials of a variety of antiplatelet therapies that included almost 29,000 piltients indicated an overall decreasein vascular mortality of approximately 15%and of 30%for nonfatal vasculareventsincluding strokeand
0
400
Fig 1. Cumulative rates of death causes according to original treatment ment. (Reprinted with permission.‘*)
from all essign-
myocardial infarction.14Data from the recently published WARIS trial indicates it would be appropriate to consider the useof oral anticoagulationin all survivors of an acute myocardial infarction.13 However, it should be noted that the WARIS trial was conducted during a time period when the use of thrombolytic therapy was not widespreadand the efficacy of aspirin therapy wasnot well established.Thus, a well-designedcomparative study assessingaspirinversuswarfarin for secondary prevention after myocardialinfarction is needed to determine the relative efficacy and safety of these drugs in secondary prevention after myocardialinfarction. ANTICOAGULANT THERAPY THE POSTMYOCARDIAL INFARCTION PATIENT
IN
Anticoagulation in the postmyocardial infarction patient shouldbeconsidered becauseit potentially may limit
800
1200
Days
1800
2000
CLINICAL
TRIALS
REVIEW
both primary ischemic cardiac events and thromboembolic complications. Based on current information, routine use of oral anticoagulation should be considered for all survivors of a myocardial infarction. It should also be noted that the targeted therapeutic range for oral anticoagulant therapy in North America was not modified when the less-sensitive commercial thromboplastins were introduced, thus leading to an inadvertent increase in the degree of anticoagulation obtained?5 A lower incidence of bleeding complications should be expected with oral anticoagulant therapy when administered in dosages presently considered as being therapeutic. Despite the impressive results shown by the WARIS study and the lower rate of bleeding complications in this study due to the appropriate range of anticoagulation therapy, there continues to be resistance to use anticoagulant therapy in survivors of myocardial infarction. Appropriate use of oral anticoagulation can impact the natural history of postmyocardial infarction patients. According to the recommendations of the American College of Cardiology (ACC) and the American Heart Association (AHA), oral anticoagulant therapy is warranted in postmyocardial infarction patients at high risk of thromboembolic events, those with an anterior or apical infarct with or without a documented mural thrombus.j6 Therapy should be continued for at least 3 months after a myocardial infarction. Long-term oral anticoagulant therapy should be strongly considered in patients with a diffusely dilated and poorly contracting left ventricle. The target prothrombin time recommended by ACC and AHA guidelines is between 1.3 and 1.5 times control. For patients at high risk for thromboembolism and those with significant left ventricular dysfunction (left ventricular ejection fraction 35%, therapy with aspirin or warfarin can be used. Given the lower risk of bleeding complications, convenience of dosing, and follow-up, aspirin remains an attractive option for these low-risk patients.
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