Angiographic and physiologic assessment of coronary flow and myocardial perfusion in the cardiac catheterization laboratory

A High De Ritis Ratio Predicts Poor Myocardial Reperfusion in Patients With ST-Segment Elevation Myocardial Infarction

Successful reperfusion of myocardial tissue is the goal of primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI). We aimed to investigate the association between the De Ritis ratio (AST/ALT) and myocardial reperfusion in patients with STEMI who underwent pPCI. We retrospectively investigated 1236 consecutive patients who were hospitalized for STEMI and underwent pPCI. ST-segment resolution (STR) was defined as the return of the deviated ST-segment to baseline; poor myocardial reperfusion was defined as <70% STR. Patients were divided into 2 groups according to the median De Ritis ratio (.921); 618 patients (50%) were assigned to the De Ritis low group while 618 patients (50%) were assigned to the De Ritis high group. Stent size, neutrophil-to lymphocyte ratio (NLR), and the De Ritis ratio found to be associated with poor myocardial reperfusion (Odds ratio (OR) 1.45, 95% CI 1.07-1.98, P = .01, OR 1.22, 95% CI 1.01-1.48, P = .03 and OR 10.9, 95% CI 7.9-15, P < .001, respectively). A high De Ritis ratio was associated with poor myocardial reperfusion in STEMI patients who underwent pPCI. As an easily obtainable test in clinical practice, the De Ritis ratio may help identify patients at major risk for impaired myocardial perfusion.

The index of microcirculatory resistance in the physiologic assessment of the coronary microcirculation

The coronary microcirculation plays a critical role in normal cardiac physiology as well as in many disease states. However, methods to evaluate the function of the coronary microvessels have been limited by technical and theoretical issues. Recently, the index of microcirculatory resistance (IMR) has been proposed and validated as a simple and specific invasive method of assessing the coronary microcirculation. By relying on the thermodilution theory and using a pressure-temperature sensor guidewire, IMR provides a measurement of the minimum achievable microcirculatory resistance in a target coronary artery territory, enabling a quantitative assessment of the microvascular integrity. Unlike indices such as coronary flow reserve, IMR is highly reproducible and independent of hemodynamic changes. In ST-elevation myocardial infarction, IMR predicts myocardial recovery and long-term mortality, whereas in patients with stable coronary artery disease, preintervention IMR predicts the occurrence of periprocedural myocardial infarction. Increasingly, research has focused on IMR-guided interventions of the microcirculation, with the aim of preventing and/or treating the microcirculatory dysfunction that commonly accompanies the epicardial coronary disease. In the present review, we will discuss the theoretical and practical basis for IMR, the clinical studies supporting it, and the future lines of research using this novel tool.

Quantification of coronary microvascular resistance using angiographic images for volumetric blood flow measurement: in vivo validation

Structural coronary microcirculation abnormalities are important prognostic determinants in clinical settings. However, an assessment of microvascular resistance (MR) requires a velocity wire. A first-pass distribution analysis technique to measure volumetric blood flow has been previously validated. The aim of this study was the in vivo validation of the MR measurement technique using first-pass distribution analysis. Twelve anesthetized swine were instrumented with a transit-time ultrasound flow probe on the proximal segment of the left anterior descending coronary artery (LAD). Microspheres were injected into the LAD to create a model of microvascular dysfunction. Adenosine (400 μg·kg(-1)·min(-1)) was used to produce maximum hyperemia. A region of interest in the LAD arterial bed was drawn to generate time-density curves using angiographic images. Volumetric blood flow measurements (Q(a)) were made using a time-density curve and the assumption that blood was momentarily replaced with contrast agent during the injection. Blood flow from the flow probe (Q(p)), coronary pressure (P(a)), and right atrium pressure (P(v)) were continuously recorded. Flow probe-based normalized MR (NMR(p)) and angiography-based normalized MR (NMR(a)) were calculated using Q(p) and Q(a), respectively. In 258 measurements, Q(a) showed a strong correlation with the gold standard Q(p) (Q(a) = 0.90 Q(p) + 6.6 ml/min, r(2) = 0.91, P < 0.0001). NMR(a) correlated linearly with NMR(p) (NMR(a) = 0.90 NMR(p) + 0.02 mmHg·ml(-1)·min(-1), r(2) = 0.91, P < 0.0001). Additionally, the Bland-Altman analysis showed a close agreement between NMR(a) and NMR(p). In conclusion, a technique based on angiographic image data for quantifying NMR was validated using a swine model. This study provides a method to measure NMR without using a velocity wire, which can potentially be used to evaluate microvascular conditions during coronary arteriography.