Background—: Most methods for assessing microvascular function are not readily available in the cardiac catheterization laboratory. The aim of this study is to determine whether the Index of Microcirculatory Resistance (IMR), measured at the time of primary percutaneous coronary intervention, is predictive of death and rehospitalization for heart failure. Methods and Results—: IMR was measured immediately after primary percutaneous coronary intervention in 253 patients from 3 institutions with the use of a pressure–temperature sensor wire. The primary end point was the rate of death or rehospitalization for heart failure. The prognostic value of IMR was compared with coronary flow reserve, TIMI myocardial perfusion grade, and clinical variables. The mean IMR was 40.3±32.5. Patients with an IMR >40 had a higher rate of the primary end point at 1 year than patients with an IMR ≤40 (17.1% versus 6.6%; P =0.027). During a median follow-up period of 2.8 years, 13.8% experienced the primary end point and 4.3% died. An IMR >40 was associated with an increased risk of death or rehospitalization for heart failure (hazard ratio [HR], 2.1; P =0.034) and of death alone (HR, 3.95; P =0.028). On multivariable analysis, independent predictors of death or rehospitalization for heart failure included IMR >40 (HR, 2.2; P =0.026), fractional flow reserve ≤0.8 (HR, 3.24; P =0.008), and diabetes mellitus (HR, 4.4; P 40 was the only independent predictor of death alone (HR, 4.3; P =0.02). Conclusions—: An elevated IMR at the time of primary percutaneous coronary intervention predicts poor long-term outcomes.

Background—: More than 20% of patients presenting to the cardiac catheterization laboratory with angina have no angiographic evidence of coronary artery disease. Despite a “normal” angiogram, these patients often have persistent symptoms, recurrent hospitalizations, a poor functional status, and adverse cardiovascular outcomes, without a clear diagnosis. Methods and Results—: In 139 patients with angina in the absence of obstructive coronary artery disease (no diameter stenosis >50%), endothelial function was assessed; the index of microcirculatory resistance, coronary flow reserve, and fractional flow reserve were measured; and intravascular ultrasound was performed. There were no complications. The average age was 54.0±11.4 years, and 107 (77%) were women. All patients had at least some evidence of atherosclerosis based on an intravascular ultrasound examination of the left anterior descending artery. Endothelial dysfunction (a decrease in luminal diameter of >20% after intracoronary acetylcholine) was present in 61 patients (44%). Microvascular impairment (an index of microcirculatory resistance ≥25) was present in 29 patients (21%). Seven patients (5%) had a fractional flow reserve ≤0.80. A myocardial bridge was present in 70 patients (58%). Overall, only 32 patients (23%) had no coronary explanation for their angina, with normal endothelial function, normal coronary physiological assessment, and no myocardial bridging. Conclusions—: The majority of patients with angina in the absence of obstructive coronary artery disease have occult coronary abnormalities. A comprehensive invasive assessment of these patients at the time of coronary angiography can be performed safely and provides important diagnostic information that may affect treatment and outcomes.

Background—: There are currently no guidelines advising long-term surveillance of patients following an acute pulmonary embolism (PE), because long-term outcome studies are rare. We investigated the long-term cardiovascular and all-cause mortality of a large patient cohort with confirmed PE in relation to baseline cardiovascular disease (CVD). Methods and Results—: Clinical details of all patients presenting with acute PE to a tertiary hospital were retrieved from medical records, and their survival tracked from a statewide death registry. There were 1023 (45% males) patients admitted with confirmed PE from 2000 to 2007. During a mean follow-up of 3.8±2.6 years, 363 patients died (35.5%), of whom only 31 (3.0%) died in-hospital during the index PE admission. The 3-month, 6-month, 1-year, 3-year, and 5-year cumulative mortality rates were 8.3%, 11.1%, 16.3%, 26.7%, and 31.6% respectively. Annual mortality did not improve over the 7-year period. The postdischarge mortality of 8.5%/patient-year was 2.5-fold that of an age- and sex-matched general population, being 12.6-fold in the youngest quintile (<55 years) and 1.9-fold in the oldest quintile (≥83 years). Patients with known CVD at baseline had 2.2-fold greater all-cause mortality than those without CVD, and this effect, although at a lower level of risk, remained significant after multivariate analysis. Of the 332 deaths occurring postdischarge, 40% were attributed to cardiovascular causes. Conclusions—: In a contemporary adult population, PE is associated with a substantially increased long-term mortality, of which nearly half is cardiovascular. Our study highlights the urgent need to develop long-term surveillance strategies in this population.

Aims We investigated whether three-dimensional (3D) and two-dimensional quantitative coronary angiography (2D-QCA) measurements differed in their accuracy in predicting reduced fractional flow reserve (FFR), and how this varied with stenosis severity and the FFR cut-off used. Methods and results Three-dimensional and 2D-QCA were compared in their measurements of minimum luminal area (MLA), percentage area stenosis, lesion length, minimum luminal diameter (MLD) and percentage diameter stenosis, and in their prediction of functionally significant FFR. In total, 63 target lesions were interrogated in 63 patients undergoing elective percutaneous coronary intervention. Of all measurements of lesion severity obtained by 3D-QCA, MLA best correlated with FFR (R = 0.63, P< 0.001), and was the most accurate predictor of FFR <0.75 (C statistic 0.86, P< 0.001). Of 2D-QCA measurements, MLD correlated best with FFR (R = 0.58, P< 0.001), and best predicted FFR <0.75 (C statistic 0.80, P<0.001). Overall, 3D-QCA showed a non-significant trend towards more accurate prediction of FFR than 2D-QCA, especially in intermediate lesions. The relationship between FFR and apparent stenosis severity was found to be curvilinear. Both 3D- and 2D-QCA were less accurate in intermediate lesions, and in predicting FFR ≤0.80 than in predicting FFR <0.75. Conclusions The accuracy of QCA in predicting functionally significant FFR is limited and is dependent on FFR cut-off used and lesion severity. Where FFR is not available or contraindicated, 3D-QCA may assist in the evaluation of coronary lesions of intermediate severity.

Ligand-induced ectodomain shedding of glycoprotein VI (GPVI) is a metalloproteinase-dependent event. We examined whether shear force, in the absence of GPVI ligand, was sufficient to induce shedding of GPVI. Human-citrated platelet-rich plasma or washed platelets were subjected to increasing shear rates in a cone-plate viscometer, and levels of intact and cleaved GPVI were examined by Western blot and ELISA. Pathophysiologic shear rates (3000-10 000 seconds⁻¹) induced platelet aggregation and metalloproteinase-dependent appearance of soluble GPVI ectodomain, and GPVI platelet remnant. Shedding of GPVI continued after transient exposure to shear. Blockade of α_IIbβ₃, GPIbα, or intracellular signaling inhibited shear-induced platelet aggregation but minimally affected shear-induced shedding of GPVI. Shear-induced GPVI shedding also occurred in platelet-rich plasma or washed platelets isolated from a von Willebrand disease type 3 patient with no detectable VWF, implying that shear-induced activation of platelet metalloproteinases can occur in the absence of GPVI and GPIbα ligands. Significantly elevated levels of sGPVI were observed in 10 patients with stable angina pectoris, with well-defined single vessel coronary artery disease and mean intracoronary shear estimates at 2935 seconds⁻¹ (peak shear, 19 224 seconds⁻¹). Loss of GPVI in platelets exposed to shear has potential implications for the stability of a forming thrombus at arterial shear rates.