Pressure- and 3D-derived coronary Flow Reserve with Hydrostatic Pressure Correction - A Validation by Intracoronary Doppler Measurements

Purpose: To develop a method of coronary flow reserve (CFR) calculation derived from threedimensional (3D) coronary angiographic parameters and intracoronary pressure data during fractional flow reserve (FFR) measurement. Methods: Altogether 19 coronary arteries of 16 native and 3 stented vessels were reconstructed in 3D. The measured distal intracoronary pressures were corrected to the hydrostatic pressure based on the height differences between the levels of the vessel orifice and the sensor position. Classical fluid dynamic equations were applied to calculate the flow during the resting state and vasodilatation on the basis of morphological data and intracoronary pressure values. 3D-derived coronary flow reserve (CFR p-3D ) was defined as the ratio between the calculated hyperemic and the resting flow and was compared to the CFR values simultaneously measured by the Doppler sensor (CFR Doppler ). Results: Haemodynamic calculations using the distal coronary pressures corrected for hydrostatic pressures showed a strong correlation between the individual CFR p-3D values and the CFR Doppler measurements (r=0.89, p<0.0001). Hydrostatic pressure correction increased the specificity of the method from 46.1% to 92.3% for predicting an abnormal CFR Doppler <2. Conclusions : CFR p-3D calculation with hydrostatic pressure correction during FFR measurement facilitates a comprehensive haemodynamic assessment, supporting the complex evaluation of macro- and microvascular coronary artery disease.

Does Coronary Microvascular Spasm Exist? Objective Evidence from Intracoronary Doppler Flow Measurements During Acetylcholine Testing

A 43-year-old woman with recurrent atypical angina underwent invasive coronary angiography including intracoronary Doppler blood flow assessment and coronary spasm provocation testing. While obstructive epicardial disease could be ruled-out angiographically, the patient experienced reproduction of her angina symptoms after intracoronary administration of acetylcholine (100 µg) during spasm provocation testing. Simultaneously, the ECG showed new-onset ST-segment depression in the absence of epicardial spasm. In addition, coronary flow velocity was significantly reduced after acetylcholine compared to the baseline condition. Following intracoronary administration of nitroglycerine (200 µg), the patient’s symptoms as well as the ECG changes and coronary flow reduction were reversed. Considering the ongoing challenges in appropriate evaluation of the pathophysiological mechanisms of coronary microvascular dysfunction, simultaneous intracoronary Doppler flow measurement during spasm testing ‐ as shown in this case ‐ may provide objective evidence for microvascular spasm in addition to the standardized diagnostic criteria, especially if they are ambiguous.

P5618Coronary flow capacity to identify stenosis associated with coronary flow improvement after coronary revascularization

Background Coronary flow capacity (CFC) has recently been introduced as a comprehensive assessment of the coronary circulation by combining coronary flow reserve (CFR) and maximal coronary flow velocity to overcome the limitations of using CFR alone, and was reported to provide enhanced risk stratification compared with CFR. However, its potential to identify stenosis that would be associated with clinically relevant flow coronary flow improvement after revascularization has not been investigated. Aims The aim of this study is to quantify coronary flow changes after revascularization in relation to CFC and CFR. Methods and results Using a combined dataset of DEFINE FLOW and the Amsterdam UMC prospective ComboWire database, a total of 133 patients (135 vessels) with intermediate coronary artery lesions who underwent intracoronary physiologic assessment including intracoronary Doppler flow measurement before and after PCI were analyzed. The median values of fractional flow reserve (FFR) and CFR before PCI were 0.70 (Q1–3: 0.56–0.80) and 1.64 (Q1–3: 1.30–2.06). The number of lesions classified by CFC before PCI were 14 for normal CFC, 40 for mildly reduced CFC, 33 for moderately reduced CFC and 48 for severely reduced CFC. The lesions with larger impairment of CFC showed greater increase in coronary flow, and vice versa (median percent increase in coronary flow by revascularization: 4.2% for normal CFC; 25.9% for mildly reduced; 50.1% for moderately reduced; 145.5% for severely reduced, P<0.0001). Using the same CFR distribution based on CFC criteria showed that only lesions with severely reduced CFR showed a significantly higher coronary flow increase after PCI (−2.6% for CFR in the normal zone; 26.6% for CFR in the mildly reduced zone; 33.3% for CFR in the moderately reduced zone; 81.7% for CFR in the severely reduced zone, P=0.0007). Compared with the established CFR cut-off value of 2.0, moderate to severely reduced CFC showed higher specificity and positive predictive value (PPV) to predict at least 20% increase in coronary flow after PCI (specificity and PPV: 86.4% and 72.5% for ischemic CFC vs. 75.8% and 40% for CFR cut-off value 2.0). Multivariate logistic regression analysis revealed that the lesions with moderately or severely reduced CFC (odd ratio [OR] = 7.606 95%interconfidence interval [CI]: 2.834–20.412, P<0.001) and pre-PCI FFR (OR=0.0002, 95% CI: 0.0002–0.0204, P<0.001) were the independent predictors of coronary flow increase after PCI. Conclusion CFC showed a higher diagnostic efficiency for identification of lesions which benefit from revascularization compared to CFR with respect to coronary flow improvement. This study provides the physiological rational of revascularization for the lesions with moderately to severely reduced CFC from the perspective of coronary flow increase. Acknowledgement/Funding Philips Volcano

Diagnostic Approach to Patients with Stable Angina and No Obstructive Coronary Arteries

The diagnosis of microvascular angina (MVA) is usually considered in patients presenting with angina symptoms and evidence of MI on non-invasive stress tests but normal coronary arteries at angiography. A definitive diagnosis of MVA, however, would require the presence of coronary microvascular dysfunction. Several invasive (e.g. intracoronary Doppler wire recording and thermodilution) and non-invasive (e.g. PET, cardiac MRI, transthoracic Doppler echocardiography) methods can be applied to obtain a diagnosis. Both endothelium- dependent and -independent coronary microvascular dilator function, as well as increased microvascular constrictor activity, should be investigated. The main issues in the assessment of clinical and diagnostic findings in patients with suspected MVA are discussed and a diagnostic approach is suggested.

Diastolic-systolic velocity ratio to detect coronary stenoses under physiological resting conditions: a mechanistic study

ObjectiveDiastolic-systolic velocity ratio (DSVR) is a resting index to assess stenoses in the left anterior descending artery (LAD). DSVR can be measured by echocardiographic or intracoronary Doppler flow velocity. The objective of this cohort study was to elucidate the fundamental rationale underlying the decreased DSVR in coronary stenoses.MethodsIn cohort 1, simultaneous measurements of intracoronary Doppler flow velocity and pressure were acquired in the LAD of 228 stable patients. Phasic stenosis resistance, microvascular resistance and total vascular resistance (defined as stenosis and microvascular resistance combined) were studied during physiological resting conditions. Stenoses were classified according to severity by strata of 0.10 fractional flow reserve (FFR) units.ResultsDSVR was decreased in stenoses with lower FFR. Stenosis resistance was equal in systole and diastole for every FFR stratum. Microvascular resistance was consistently higher during systole than diastole. In lower FFR strata, stenosis resistance as a percentage of the total vascular resistance increases both during systole and diastole. The difference between the stenosis resistance as a percentage of total vascular resistance during systole and diastole increases for lower FFR strata, with an accompanying rise in diastolic-systolic resistance ratio. A significant inverse correlation was observed between DSVR and the diastolic-systolic resistance ratio (r=0.91, p<0.001). In cohort 2 (n=23), DSVR was measured both invasively and non-invasively by transthoracic echocardiography, yielding a good correlation (r=0.82, p<0.001).ConclusionsThe rationale by which DSVR is decreased distal to coronary stenoses is dependent on a comparatively higher influence of the increased stenosis resistance on total vascular resistance during diastole than systole.

Physiologic Functional Evaluation of Left Internal Mammary Artery Graft to Left Anterior Descending Coronary Artery Steal due to Unligated First Thoracic Branch in a Case of Refractory Angina

Unligated side branches of the left internal mammary artery (LIMA) have been described in the literature as a cause of coronary steal resulting in angina. Despite a number of studies reporting successful side branch embolization to relieve symptoms, this phenomenon remains controversial. Hemodynamic evidence of coronary steal using angiographic and intravascular Doppler techniques has been supported by some and rejected by others. In this case study using an intracoronary Doppler wire with adenosine, we demonstrate that a trial occlusion of the LIMA thoracic side branch with selective balloon inflation can confirm physiologic significant steal and whether coil embolization of the side branch is indicated.

Abstract 20670: Coronary Microembolization During Transfemoral Transcatheter Aortic Valve Implantation: An Intracoronary Doppler Study

Background: A postprocedural increase of the serum troponin I concentration (TnI) reflects myocardial injury and occurs frequently during transcatheter aortic valve implantation (TAVI). Periprocedural coronary microembolization is a potential cause of such injury. We therefore evaluated each step of the transfemoral TAVI procedure for coronary embolization using intracoronary Doppler (ICD) in the left anterior descending (LAD) artery. Methods: 15 high-risk patients with severe, symptomatic aortic valve stenosis (age 79 ± 45 yrs; EuroScore 17 ± 4%) who underwent transfemoral TAVI using the balloon-expandable Edwards bioprosthesis were included. ICD examinations were recorded and evaluated off-line for high-intensity transient signals (HITS). Perioperative concentrations of TnI were serially measured within the first 72 h after TAVI, and a cardiac MRI with late gadolinium-enhancement (LGE) was performed within 7 days. Results: HITS were detected in all patients (figure 1), mostly during the initial crossing of the native valve and positioning of the prosthesis with subsequent implantation. TnI peaked at 24 h after TAVI (3.17 ng/ml), and LGE was observed in only one single case. There was no correlation between amount of HITS and TnI area under the curve in the first 72 h after TAVI. Conclusions: Procedural HITS were detected by ICD in all patients undergoing transfemoral TAVI. The highest amount of HITS was observed during initial valve passage and positioning of the prosthesis with subsequent implantation. However, no association was found between the number of HITS and myocardial injury, as reflected by increased serum TnI concentrations or LGE on cardiac MRI.