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Global alteration in perfusion response to increasing oxygen consumption in patients with single-vessel coronary
G Sambuceti1, P Marzullo, A Giorgetti
1CNR Institute of Clinical Physiology, Pisa, Italy.
Insights
Coronary artery disease (CAD) patients exhibit abnormal myocardial blood flow (MBF) regulation, even in areas with normal arteries. This study reveals impaired MBF response to increased metabolic demand in CAD, suggesting factors beyond epicardial stenosis influence coronary reserve.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Medical Imaging
Background:
- Coronary artery disease (CAD) is associated with abnormal regulation of myocardial blood flow (MBF) in regions with apparently normal coronary arteries.
- The relationship between this altered MBF regulation and the response to increasing metabolic demand in CAD remains unclear.
Purpose of the Study:
- To investigate the myocardial blood flow (MBF) response to increasing metabolic demand in patients with coronary artery disease (CAD).
- To compare MBF regulation in normally supplied and poststenotic regions of CAD patients versus healthy subjects.
Main Methods:
- Myocardial blood flow (MBF) was assessed using positron emission tomography ([13N]ammonia) in 9 normal subjects and 24 CAD patients.
- Measurements were taken at rest, during atrial pacing tachycardia, and after dipyridamole administration.
- MBF was evaluated in both poststenotic (S) and normally supplied (N) territories in CAD patients.
Main Results:
- CAD patients demonstrated significantly lower MBF in both S and N territories compared to normal subjects at rest, during pacing, and after dipyridamole.
- While normal subjects showed a strong correlation between MBF changes and rate-pressure product, this correlation was absent in both S and N regions of CAD patients.
- These findings indicate impaired flow regulation in CAD, irrespective of epicardial stenosis severity.
Conclusions:
- Factors beyond epicardial stenosis significantly impact the flow response to increased metabolic demand and coronary reserve in CAD patients.
- Abnormalities in MBF regulation exist even in coronary artery segments without significant stenosis.
- Further research is needed to identify these additional factors affecting coronary flow reserve in CAD.
Background:
Recent evidence suggests that, in coronary artery disease (CAD), myocardial blood flow (MBF) regulation is abnormal in regions supplied by apparently normal coronary arteries. However, the relation between this alteration and MBF response to increasing metabolic demand has not been fully elucidated.
Methods And Results:
MBF was assessed at baseline, during atrial pacing tachycardia, and after dipyridamole (0.56 mg/kg IV over 4 minutes) in 9 normal subjects and in 24 patients with ischemia on effort, no myocardial infarction, and isolated left anterior descending (n = 19) or left circumflex (n = 5) coronary artery stenosis (> or = 50% diameter narrowing). Perfusion of both poststenotic (S) and normally supplied (N) areas was measured off therapy by positron emission tomography and [13N]ammonia. Normal subjects and CAD patients showed similar rate-pressure products at baseline, during pacing, and after dipyridamole. In CAD patients, MBF was lower in S than in N territories at rest (0.68 +/- 0.14 versus 0.74 +/- 0.18 mL.min-1.g-1, respectively, P < .05), during pacing (0.92 +/- 0.29 versus 1.16 +/- 0.40 mL.min-1.g-1, respectively, P < .01), and after dipyridamole (1.18 +/- 0.34 versus 1.77 +/- 0.71 mL.min-1.g-1, respectively, P < .01). However, normal subjects showed significantly higher values of MBF both at rest (0.92 +/- 0.13 mL.min-1.g-1, P < .05 versus both S and N areas), during pacing tachycardia (1.95 +/- 0.64 mL.min-1.g-1, P < .01 versus both S and N areas), and after dipyridamole (3.59 +/- 0.71 mL.min-1.g-1, P < .01 versus both S and N areas). The percent change in flow was strictly correlated with the corresponding change in rate-pressure product in normal subjects (r = .85, P < .01) but not in either S (r = .04, P = NS) or N regions (r = .08, P = NS) of CAD patients.
Conclusions:
Besides epicardial stenosis, further factors may affect flow response to increasing metabolic demand and coronary reserve in patients with CAD.