Drugs 42 (Suppl. 2): 38-42, 1991 0012-6667/91/0200-0038/$2.50/0 © Adis International Limited. All rights reserved. DRSUP2174
Myocardial Infarction
Secondary Prevention with Nifedipine
W. Rafflenbeul and F. Ebner Hannover Medical School, Hannover, Federal Republic of Germany
Summary
The rationale for the use of nifedipine in patients with acute myocardial infarction (MI) is based on the various cardiovascular actions of the compound: reduction ofmyocardial oxygen consumption by attenuation of cardiac and vascular smooth muscle tension; augmentation of oxygen and substrate supply after increased coronary blood flow with dilatation of epicardial coronary arteries (particularly in coronary obstructions) and dilatation of coronary resistance and collateral vessels; myocardial 'protection', i.e. reduction of myocardial damage via a complex intracellular mechanism, the primary outcome of which is the maintenance of an energy level sufficient to preserve the ionic homeostasis of the myocyte. The effect of nifedipine on reinfarction and mortality rates was evaluated in 6 well designed studies involving 8670 patients with evolving or established acute MI. Compared with placebo, short term therapy (for up to 6 months) with nifedipine 30 to 120 mg/day initiated, in some patients, as early as 3 hours after the onset of symptoms did not reduce either reinfarction rate or mortality. In one study (SPRINT I) [Israeli Sprint Study Group 1988], where a regimen of nifedipine 30 mgjday was only started 7 to 21 days after infarction, the exceptionally low mortality rate (5.7%) over 10 months in the placebo group precluded the demonstration of a beneficial effect of nifedipine. These results collectively suggest that nifedipine does not prevent the 'secondary' coronary events of plaque rupture and thrombus formation associated with MI and sudden cardiac death. However, the suppression of early lesions by nifedipine (as demonstrated in the INTACT study [LichtIen et al. 1990]) might reduce 'primary' progression and improve the long term survival after MI.
The powerful cardiovascular properties of calcium antagonists, particularly the reduction in tension of vascular smooth muscle and cardiac muscle as well as the cardioprotective effects, as outlined in the paper in this supplement by Dr Nayler (Nayler 1991), provide the rationale for the use of calcium antagonists in preventing secondary complications after acute myocardial infarction (MI).
1. Overview 0/ the Major Clinical Trials 0/ Nijedipine in Secondary Prevention Six major randomised, double-blind, placebocontrolled clinical trials involving nifedipine have been highlighted in this review, because they exemplify the neutral effects of calcium antagonists in patients with acute MI (table I). The Norwegian Nifedipine Multicenter Trial
39
Nifedipine in Myocardial Infarction
Table I. Major placebo (P)-controlled trials of nifedipine (N) in patients at risk of or with confirmed myocardial infarction (MI) References
Study details No. of patients
Sirnes et al. (1984)
Muller et al. (1984)
227
66
+
1053
Wilcox et al. (1986)
Gottlieb et al. (1988)
Israeli Sprint Study Group (1988)
Sprint II Study Group (1988)
4491
132
2276
1373 (828)b
Time to intervention
< 12h
< 6h
< 16h
Myocardial Infarction
Secondary Prevention with Nifedipine
W. Rafflenbeul and F. Ebner Hannover Medical School, Hannover, Federal Republic of Germany
Summary
The rationale for the use of nifedipine in patients with acute myocardial infarction (MI) is based on the various cardiovascular actions of the compound: reduction ofmyocardial oxygen consumption by attenuation of cardiac and vascular smooth muscle tension; augmentation of oxygen and substrate supply after increased coronary blood flow with dilatation of epicardial coronary arteries (particularly in coronary obstructions) and dilatation of coronary resistance and collateral vessels; myocardial 'protection', i.e. reduction of myocardial damage via a complex intracellular mechanism, the primary outcome of which is the maintenance of an energy level sufficient to preserve the ionic homeostasis of the myocyte. The effect of nifedipine on reinfarction and mortality rates was evaluated in 6 well designed studies involving 8670 patients with evolving or established acute MI. Compared with placebo, short term therapy (for up to 6 months) with nifedipine 30 to 120 mg/day initiated, in some patients, as early as 3 hours after the onset of symptoms did not reduce either reinfarction rate or mortality. In one study (SPRINT I) [Israeli Sprint Study Group 1988], where a regimen of nifedipine 30 mgjday was only started 7 to 21 days after infarction, the exceptionally low mortality rate (5.7%) over 10 months in the placebo group precluded the demonstration of a beneficial effect of nifedipine. These results collectively suggest that nifedipine does not prevent the 'secondary' coronary events of plaque rupture and thrombus formation associated with MI and sudden cardiac death. However, the suppression of early lesions by nifedipine (as demonstrated in the INTACT study [LichtIen et al. 1990]) might reduce 'primary' progression and improve the long term survival after MI.
The powerful cardiovascular properties of calcium antagonists, particularly the reduction in tension of vascular smooth muscle and cardiac muscle as well as the cardioprotective effects, as outlined in the paper in this supplement by Dr Nayler (Nayler 1991), provide the rationale for the use of calcium antagonists in preventing secondary complications after acute myocardial infarction (MI).
1. Overview 0/ the Major Clinical Trials 0/ Nijedipine in Secondary Prevention Six major randomised, double-blind, placebocontrolled clinical trials involving nifedipine have been highlighted in this review, because they exemplify the neutral effects of calcium antagonists in patients with acute MI (table I). The Norwegian Nifedipine Multicenter Trial
39
Nifedipine in Myocardial Infarction
Table I. Major placebo (P)-controlled trials of nifedipine (N) in patients at risk of or with confirmed myocardial infarction (MI) References
Study details No. of patients
Sirnes et al. (1984)
Muller et al. (1984)
227
66
+
1053
Wilcox et al. (1986)
Gottlieb et al. (1988)
Israeli Sprint Study Group (1988)
Sprint II Study Group (1988)
4491
132
2276
1373 (828)b
Time to intervention
< 12h
< 6h
< 16h
