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Published on: February 9, 2016
Assessment of coronary microcirculation in a swine animal model
Zhang Zhang1, Shigeho Takarada, Sabee Molloi
1Department of Radiological Sciences, University of California-Irvine, Irvine, California 92697, USA.
Insights
Normalized microvascular resistance (NMR) is a more reliable index than coronary flow reserve (CFR) and zero-flow pressure (Pzf) for assessing coronary microcirculation, especially in the presence of stenosis.
Area of Science:
- Cardiovascular Physiology
- Diagnostic Imaging
- Medical Device Technology
Background:
- Coronary microvascular dysfunction significantly impacts patient prognosis.
- Current indices like coronary flow reserve (CFR) and zero-flow pressure (Pzf) have limitations in assessing microcirculation.
- Accurate assessment of coronary microcirculation is crucial for diagnosing and managing cardiovascular diseases.
Purpose of the Study:
- To compare the reliability of different hemodynamic indices in assessing coronary microcirculation.
- To determine the most accurate index for detecting microvascular dysfunction, particularly in the presence of epicardial stenosis.
- To evaluate the potential of normalized microvascular resistance (NMR) as a superior diagnostic tool.
Main Methods:
- Fifteen swine underwent instrumentation with a flow probe and pressure wire.
- Maximal hyperemia was induced using adenosine infusion.
- Microvascular dysfunction was created using microspheres, and stenosis was induced using an occluder.
- Flow probe-based (NMR(qh)) and angiographic (NMR(ah)) normalized microvascular resistance were calculated and compared with CFR and Pzf using receiver operating characteristic curves.
Main Results:
- Normalized microvascular resistance (NMR(qh) and NMR(ah)) demonstrated significantly higher reliability in detecting microvascular deterioration compared to CFR and Pzf.
- NMR provided a more accurate assessment of coronary microcirculation, with improved accuracy observed in the presence of stenosis.
- Angiographic normalized microvascular resistance (NMR(ah)) emerged as a potentially less invasive method for assessing coronary microcirculation.
Conclusions:
- Normalized microvascular resistance is a more reliable hemodynamic index for assessing coronary microcirculation than CFR and Pzf.
- NMR offers superior accuracy in detecting microvascular dysfunction, especially when epicardial stenosis is present.
- Angiographic NMR (NMR(ah)) represents a promising, less invasive approach for evaluating coronary microcirculation.
Abstract:
Coronary microvascular dysfunction has important prognostic implications. Several hemodynamic indexes, such as coronary flow reserve (CFR), microvascular resistance, and zero-flow pressure (P(zf)), were used to establish the most reliable index to assess coronary microcirculation. Fifteen swine were instrumented with a flow probe, and a pressure wire was advanced into the distal left anterior descending artery. Adenosine was used to produce maximum hyperemia. Microspheres were used to create microvascular dysfunction. An occluder was used to produce stenosis. Blood flow from the probe (Q(p)), aortic pressure, distal coronary pressure, and right atrium pressure were recorded. Angiographic flow (Q(a)) was calculated using a time-density curve. Flow probe-based CFR and angiographic CFR were calculated using Q(p) and Q(a), respectively. Flow probe-based (NMR(qh)) and angiographic normalized microvascular resistance (NMR(ah)) were determined using Q(p) and Q(a), respectively, during hyperemia. P(zf) was calculated using Q(p) and distal coronary pressure. Two series of receiver operating characteristic curves were generated: normal epicardial artery model (N model) and stenosis model (S model). The areas under the receiver operating characteristic curves for flow probe-based CFR, angiographic CFR, NMR(qh), NMR(ah), and P(zf) were 0.855, 0.836, 0.976, 0.956, and 0.855 in N model and 0.737, 0.700, 0.935, 0.889, and 0.698 in S model. Both NMR(qh) and NMR(ah) were significantly more reliable than CFR and P(zf) in detecting the microvascular deterioration. Compared with CFR and P(zf), NMR provided a more accurate assessment of microcirculation. This improved accuracy was more prevalent when stenosis existed. Moreover, NMR(ah) is potentially a less invasive method for assessing coronary microcirculation.
