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Coronary microvascular reactivity to sympathetic stimulation in patients with idiopathic dilated cardiomyopathy
A E Drzezga1, R Blasini, S I Ziegler
1Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
Insights
Idiopathic dilated cardiomyopathy (IDC) patients show impaired microvascular reactivity to sympathetic stimulation compared to healthy individuals. This suggests a potential exhaustion of coronary microvasculature dilation in IDC, explaining their reduced blood flow response.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Medical Imaging
Background:
- Idiopathic dilated cardiomyopathy (IDC) is a condition affecting heart muscle function.
- Assessing microvascular reactivity is crucial for understanding cardiovascular health.
- Noninvasive assessment methods are valuable for patient evaluation.
Purpose of the Study:
- To noninvasively assess microvascular reactivity to sympathetic stimulation in IDC patients versus healthy volunteers.
- To investigate the role of coronary microvasculature in IDC.
- To evaluate the utility of 13N-ammonia PET and cold pressor testing (CPT) in assessing this reactivity.
Main Methods:
- Utilized 13N-ammonia Positron Emission Tomography (PET) and tracer kinetic modeling.
- Quantified myocardial blood flow and myocardial vascular resistance (MVR) at rest and during CPT.
- Included 10 healthy volunteers and 10 IDC patients matched for age and sex.
Main Results:
- IDC patients had significantly lower MVR at rest compared to healthy volunteers.
- Healthy volunteers showed a significant decrease in MVR during CPT (22%), while IDC patients did not (9%).
- The increase in myocardial blood flow in response to CPT was significantly lower in IDC patients (20%) versus healthy volunteers (52%).
Conclusions:
- 13N PET imaging combined with CPT is effective for noninvasively assessing coronary microvascular response to sympathetic stimulation in IDC.
- Lower resting coronary vascular resistance in IDC patients suggests potential exhaustion of sympathetically induced vasodilation.
- This microvascular dysfunction may explain the impaired blood flow response observed in IDC patients during sympathetic stimulation.
Unlabelled:
The objective of this study was to assess noninvasively the microvascular reactivity to sympathetic stimulation in patients with idiopathic dilated cardiomyopathy (IDC) and in healthy volunteers, who underwent cardiac catheterization for exclusion of coronary artery disease.
Methods:
Myocardial flow was quantified with 13N-ammonia PET and tracer kinetic modeling at rest and in response to cold pressor testing (CPT). Ten healthy volunteers (8 men, 2 women; mean age +/- SD, 50.7 +/- 15 y) and 10 matched patients (8 men, 2 women; mean age, 52.5 +/- 14 y) with IDC (mean left ventricular ejection fraction, 0.30 +/- 0.12) were included in the study.
Results:
Myocardial perfusion at rest was not significantly different between the groups. However, myocardial vascular resistance (MVR) was significantly lower in IDC patients at rest than in healthy volunteers. In response to CPT a significant decrease in MVR was found in healthy volunteers (1.9 +/- 0.4 to 1.5 +/- 0.4 mm Hg x 100 g/mL; 22% decrease) but not in IDC patients (1.5 +/- 0.4 to 1.4 +/- 0.3 mm Hg x 100 g/mL; 9% decrease). Consequently, the increase of the myocardial blood flow in response to CPT was significantly lower (P < 0.008) in IDC patients (56 +/- 17 to 66 +/- 18 mL/100g/min; 20% increase) compared with healthy volunteers (52 +/- 12 to 80 +/- 30 mL/100 g/min; 52% increase), whereas both showed comparable hemodynamic reactions.
Conclusion:
The data indicate that CPT in combination with 13N PET imaging is a valuable noninvasive tool for assessment of coronary microvascular reaction to sympathetic stimulation in IDC patients. Lower coronary vascular resistance was found in IDC patients at rest compared with healthy volunteers, suggesting possible exhaustion of sympathetically induced dilation of the coronary microvasculature in IDC patients at rest. This mechanism may explain the impaired flow response to cold in IDC patients in the present study.