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Association Between Serial Measures of Systemic Blood Pressure and Early Coronary Arterial Perfusion Status Following
1Department of Internal Medicine, University of Massachusetts Medical School, Worcester, Massachusetts.
Insights
Systemic blood pressure is not a key factor in the success of thrombolytic therapy for myocardial infarction (MI). Treatment timing and the specific drug used are more important predictors of coronary reperfusion.
Area of Science:
- Cardiology
- Pharmacology
- Medical Research
Background:
- Systemic hypotension is common in myocardial infarction (MI), advanced heart failure, and cardiogenic shock.
- Thrombolytic therapy has shown limited success in improving outcomes for these high-mortality patient groups.
- The direct link between systemic blood pressure and thrombolytic therapy efficacy in humans remains unclear.
Purpose of the Study:
- To investigate the relationship between systemic blood pressure and coronary perfusion following thrombolytic therapy in MI patients.
- To identify independent predictors of coronary reperfusion in patients receiving intravenous thrombolytic agents.
Main Methods:
- A study of 127 MI patients receiving intravenous thrombolytic therapy (tPA or streptokinase) within 6 hours of symptom onset.
- Serial systemic blood pressure measurements were taken before, during, and after thrombolytic infusion.
- Coronary angiography was performed within 120 minutes of treatment initiation; patients also received heparin and aspirin.
Main Results:
- Univariate analysis showed diastolic blood pressure below 80 mmHg was associated with reduced coronary perfusion (TIMI flow grade).
- In tPA-treated patients, a greater change in diastolic blood pressure correlated inversely with coronary perfusion.
- Multivariate regression identified shorter time to treatment and tPA use as independent predictors of coronary perfusion grade.
Conclusions:
- Systemic blood pressure within the studied ranges is not an independent predictor of coronary reperfusion after thrombolytic therapy.
- Intrinsic factors of the ruptured plaque, occlusive thrombus, and local metabolic environment likely determine thrombolytic success.
- Further research is needed to explore factors influencing thrombolysis efficacy beyond systemic blood pressure.
Abstract:
Background: Systemic hypotension, at times transient while in other instances more prolonged, is common among patients with myocardial infarction (MI). It also is a characteristic feature for patients experiencing either advanced congestive heart failure or cardiogenic shock. In this group of patients, thrombolytic therapy has failed to exert. favorable impact on their high in-hospital mortality. Although it has been postulated that the success of thrombolytic therapy is directly linked to systemic blood pressure' there is little information available in human subjects. Methods and Results: In a University of Massachusetts Thrombolysis Data Bank Study, 127 patients with MI who were given intravenous thrombolytic therapy (tPA or streptokinase) within 6 hours from symptom onset (4.2 +/- 1.5 hours) had serial systemic blood pressure measurements (at the time of hospital arrival, treatment initiation, and every 30 minutes during the thrombolytic infusion) and underwent coronary angiography within 120 minutes of treatment initiation. All patients received intravenous heparin and oral aspirin. By univariate analysis, disastolic blood pressure below 80 mmHg at the time of treatment initiation was associated with a reduced angiographic coronary perfusion grade [Thrombolysis in Myocardial Infarction (TIMI) flow grade; p + 0.02]. A correlation analysis of tPA-treated patients indicated that a greater maximum change in diastolic blood pressure during treatment correlated inversely with coronary perfusion (r +.24, p < 0.05). By multivariate regression analysis, however, only shorter time to treatment (p + 0.001) and thrombolysis with tPA (p + 0.02) were independent predictors of coronary arterial perfusion grade. Conclusion: Systemic blood pressure (and presumably proximal coronary arterial perfusion pressure) in the ranges investigated in this study is not an independent predictor of coronary reperfusion following intravenous thrombolytic therapy with either tPA or streptokinase. It seems likely, therefore, that properties intrinsic to the ruptured plaque and occlusive thrombus, and potentially the local metabolic environment, either alone or acting synergistically with perfusion pressure, are determinants of thrombolytic success. Further investigation of factors influencing the efficacy of thrombolysis should be undertaken.