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Blood pressure elevation after phenylephrine infusion may adversely affect myocardial perfusion in patients with
Athanassios Antonopoulos1, Dimitrios Nikolopoulos, Evangelos K Georgiou
1Cardiology Branch of Ygeias Melathron Clinic, Athens, Greece. omfalos@cc.uoa.gr
Insights
Elevating blood pressure with phenylephrine (PH) in coronary artery disease (CAD) patients impairs myocardial perfusion. This impairment correlates with the extent of coronary artery disease, as shown by thallium-201 (Tl) scintigraphy.
Area of Science:
- Cardiology
- Nuclear Medicine
- Cardiovascular Physiology
Background:
- Blood pressure significantly impacts myocardial oxygen demand.
- Limited data exists on blood pressure changes during myocardial ischemia.
- Phenylephrine (PH), an alpha-adrenergic agonist, may alter myocardial perfusion in coronary artery disease (CAD) patients due to increased left ventricular (LV) wall stress.
Purpose of the Study:
- To investigate the effects of blood pressure elevation on myocardial perfusion using thallium-201 (Tl) scintigraphy.
- To test the hypothesis that pressure loading alone, without increased heart rate, can provoke transient impairment of regional myocardial perfusion in CAD patients.
Main Methods:
- 41 patients with documented CAD underwent PH infusion to increase mean blood pressure by ~30% without significant heart rate increase.
- Thallium-201 (Tl) was injected after achieving target blood pressure and heart rate.
- Tl scintigraphy was performed, and results were correlated with coronary angiography findings.
Main Results:
- Phenylephrine (PH) scintigraphy revealed perfusion defects, with defect size directly correlating with the number of diseased coronary vessels.
- Lower thallium-201 (Tl) activity and increased lung Tl uptake/lung-to-heart ratio were observed with increasing severity of coronary artery disease.
- These findings indicate impaired myocardial perfusion proportional to the extent of CAD.
Conclusions:
- Elevating blood pressure through PH loading significantly impairs myocardial perfusion in CAD patients.
- The degree of perfusion impairment correlates strongly with the extent of coronary artery disease found in angiography.
- This study highlights the impact of blood pressure changes on myocardial perfusion independent of heart rate changes.
Background:
Although blood pressure is a major determinant of myocardial oxygen-demand, little information is currently available regarding the changes in blood pressure (BP) during myocardial ischemia. Since BP elevation may cause left ventricular (LV) wall stress and an increase in oxygen demand, infusion of an alpha-adrenergic agonist, such as phenylephrine (PH), may provoke changes in myocardial perfusion in coronary artery disease (CAD) patients. As the effects of BP changes alone on myocardial perfusion have never been assessed by thallium-201 (Tl) scintigraphy, we investigated the effects of BP elevation after PH infusion, in order to study the hypothesis that pressure loading alone without increases in heart rate, may provoke transient impairment of regional myocardial perfusion, in CAD patients.
Patients And Methods:
Forty-one (41) patients with angiographically documented CAD, aged 54+/-8 years, were included in our study. Each patient was given, without any complications, a PH (0.1 mg/ml) dose infused at a rate of 0.8 ml/mm, determined by a standardisation procedure and producing a mean blood pressure elevation of approximately 30% above baseline levels and a heart rate response to levels of no less than 50 bpm. One minute after the desired blood pressure and heart rate responses were reached, 2 mCi of Tl were injected and the PH infusion continued until the termination of the test. Tl scintigraphy was performed both 2 min after Tl injection and 4 h later, while the results were correlated to coronary angiography findings.
Results:
PH scintigraphy produced 152 total defects. The mean perfusion defect size (%) was 14+/-12 and was directly related to the number of diseased vessels, i.e., 2% for one-vessel disease, 15% for two-vessel disease and 25% for three-vessel disease (P<0.05). The lowest percentage Tl activity values were 56+/-14 and were inversely related to the number of diseased vessels (P<0.01). The mean Tl lung counts/pixel values were 25+/-8 while it increased as the number of diseased vessels increased (P<0.01). The mean lung/heart ratio values were 0.31+/-0.08 while it increased as the number of diseased vessels increased (P<0.01).
Conclusion:
BP elevation after PH loading, produces a significant impairment of myocardial perfusion, that correlates well with the extend of angiographic findings.
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