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Background--Small observational studies demonstrate the feasibility of transradial approach for chronic total occlusion (CTO) percutaneous coronary intervention. The aim of the current study is to assess technical success, complication rates, and procedural efficiency in fully transradial approach (fTRA) and transfemoral approach (TFA) in a large prospective European registry adopting the hybrid algorithm for CTO percutaneous coronary intervention (Registry of CrossBoss and Hybrid Procedures in France, the Netherlands, Belgium and United Kingdom, RECHARGE registry). Methods and Results--We analyzed 1253 CTO percutaneous coronary intervention procedures performed according to the hybrid protocol in 17 European centers, comparing fTRA (single or biradial access) and TFA (single or bifemoral or combined radial and femoral access). fTRA was applied in 306 (24%) and TFA in 947 (76%) cases. The average Japanese CTO score was 2.1±1.2 in fTRA and 2.3±1.1 in TFA (P=0.06). Technical success was achieved in 85% in fTRA and 86% in TFA (P=0.51). Technical success was comparable for fTRA and TFA in different Japanese CTO score subgroups after multivariable analysis and after propensity adjustment. In-hospital major adverse cardiac and cerebral events occurred in 2.0% in fTRA and 2.9% in TFA (P=0.40). Major access site bleeding occurred in 0.3% in fTRA and 0.5% in TFA (P=0.66). fTRA compared with TFA had similar procedural duration (80 minutes [54-120 minutes] versus 90 minutes [60-121 minutes]; P=0.07), similar radiation dose (dose area product 89 Gray×cm² [52-163 Gray×cm²] versus 101 Gray×cm² [59-171 Gray×cm²]; P=0.06), and lower contrast agent use (200 mL [150-310 mL] versus 250 mL [200-350 mL]; P<0.01). Conclusions--fTRA CTO percutaneous coronary intervention is a valid alternative to TFA with a high rate of success, low complication rates, and no decrease in procedural efficiency. [ABSTRACT FROM AUTHOR]

Background--Development of the CrossBoss and Stingray devices for antegrade dissection and reentry (ADR) of chronic total occlusions has improved historically suboptimal outcomes. However, the outcomes, safety, and failure modes of the technique have to be studied in a larger patient cohort. This preplanned substudy of the RECHARGE registry (Registry of CrossBoss and Hybrid Procedures in France, the Netherlands, Belgium and United Kingdom) aims to evaluate the value and use of ADR and determine its future position in contemporary chronic total occlusion intervention. Methods and Results--Patients were selected if an ADR strategy was applied. Outcomes, safety, and failure modes of the technique were assessed. The ADR technique was used in 23% (n=292/1253) of the RECHARGE registry and was mainly applied for complex lesions (Japanese chronic total occlusion score=2.7±1.1). ADR was the primary strategy in 30% (n=88/292), of which 67% were successful. Bail-out ADR strategies were successful in 63% (n=133/210). The Controlled ADR (ie, combined CrossBoss-Stingray) subtype was applied most frequently (32%; n=93/292) and successfully (81%; n=75/93). Overall perlesion success rate was 78% (n=229/292), after use of additional bail-out strategies. The inability to reach the distal target zone (n=48/100) or to reenter (n=43/100) most commonly led to failure. ADR-associated major events occurred in 3.4% (n=10/292). Conclusions--Although mostly applied as a bail-out strategy for complex lesions, the frequency, outcomes, and low complication rate of the ADR technique and its subtypes confirm the benefit and value of the technique in hybrid chronic total occlusion percutaneous coronary intervention, especially when antegrade wiring or retrograde approaches are not feasible. [ABSTRACT FROM AUTHOR]

Early identification and treatment of the vulnerable plaque, that is, a coronary artery lesion with a high likelihood of rupture leading to an acute coronary syndrome, have gained great interest in the cardiovascular research field. Postmortem studies have identified clear morphological characteristics associated with plaque rupture. Recent advances in invasive and noninvasive coronary imaging techniques have empowered the clinician to identify suspected vulnerable plaques in vivo and paved the way for the evaluation of therapeutic agents targeted at reducing plaque vulnerability. Local treatment of vulnerable plaques by percutaneous coronary intervention and systemic treatment with anti-inflammatory and low-density lipoprotein–lowering drugs are currently being investigated in large randomized clinical trials to assess their therapeutic potential for reducing adverse coronary events. Results from these studies may enable a more patient-tailored strategy for the treatment of coronary artery disease. [ABSTRACT FROM AUTHOR]

Background—Reduced myocardial efficiency represents a target for therapy in hypertrophic cardiomyopathy although therapeutic benefit may depend on disease stage. Here, we determined disease stage–dependent changes in myocardial efficiency and effects of myectomy surgery.Methods and Results—Myocardial external efficiency (MEE) was determined in 27 asymptomatic mutation carriers (genotype positive/phenotype negative), 10 patients with hypertrophic obstructive cardiomyopathy (HOCM), 10 patients with aortic valve stenosis, and 14 healthy individuals using [11C]-acetate positron emission tomography and cardiovascular magnetic resonance imaging. Follow-up measurements were performed in HOCM and aortic valve stenosis patients 4 months after surgery. External work did not differ in HOCM compared with controls, whereas myocardial oxygen consumption was lower in HOCM. Because of a higher cardiac mass, total cardiac oxygen consumption was significantly higher in HOCM than in controls and genotype positive/phenotype negative. MEE was significantly lower in genotype positive/phenotype negative than in controls (28±6% versus 42±6%) and was further decreased in HOCM (22±5%). In contrast to patients with aortic valve stenosis, MEE was not improved in patients with HOCM after surgery, which was explained by opposite changes in the septum (decrease) and lateral (increase) wall.Conclusions—Different mechanisms underlie reduced MEE at the early and advanced stage of hypertrophic cardiomyopathy. The initial increase and subsequent reduction in myocardial oxygen consumption during disease progression indicates that energy deficiency is a primary mutation-related event, whereas mechanisms secondary to disease remodeling underlie low MEE in HOCM. Our data highlight that the benefit of therapies to improve energetic status of the heart may vary depending on the disease stage and that treatment should be initiated before cardiac remodeling. [ABSTRACT FROM AUTHOR]

Risk stratification for ventricular arrhythmias (VAs) is important to refine selection criteria for primary prevention implantable cardioverter defibrillator therapy. Impaired hyperemic myocardial blood flow (MBF) is associated with increased mortality rate in ischemic and nonischemic cardiomyopathy, which may be attributed to electric instability inducing VAs. The aim of this pilot study was to assess whether hyperemic MBF impairment may be related with VA inducibility in patients with ischemic cardiomyopathy.Thirty patients with ischemic cardiomyopathy referred for primary prevention implantable cardioverter defibrillator implantation were prospectively included (26 men; 65±8 years old; left ventricular ejection fraction, 29±6%). [15O]H2O positron-emission tomography was performed to quantify resting MBF, hyperemic MBF, and coronary flow reserve. Left ventricular dimensions, function, and scar burden were assessed with cardiovascular magnetic resonance imaging. An electrophysiological study was performed to test VA inducibility. Positive electrophysiological study patients (n=12) showed reduced hyperemic MBF (1.25±0.30 versus 1.66±0.38 mL·min-1·g-1; P<0.01) and coronary flow reserve (1.59±0.49 versus 2.12±0.48; P<0.01) compared with electrophysiological study negative patients (n=18). In electrophysiological study positive patients, the number of scar segments >75% transmurality was higher (P<0.05), although scar size and border zone did not differ. Receiver-operating characteristic curve analysis indicated that impaired hyperemic MBF (area under the curve, 0.84; 95% confidence intervals [0.69-0.99]) and coronary flow reserve (area under the curve, 0.77; 95% confidence intervals [0.57-0.96]) were associated with VA inducibility.In this pilot study, impaired hyperemic MBF and coronary flow reserve were associated with VA inducibility in patients with ischemic cardiomyopathy. These results are hypothesis generating for a potential role of quantitative positron-emission tomography perfusion imaging in risk stratification for VAs. [ABSTRACT FROM AUTHOR]

The article discusses a study on the association between right ventricular (RV) failure in idiopathic pulmonary arterial hypertension (IPAH) and reduced efficiency of myocardial oxygen utilization. The study involved patients in the New York Heart Association (NYHA) class II and class III. The patients underwent right heart catheterization and positron emission tomography (PET). Both groups had similar RV power and oxygen supply. Class II had lower RV oxygen extraction compared with class III.

Supplemental Digital Content is available in the text. Background: Multiple crossing techniques in chronic total occlusion (CTO) percutaneous coronary intervention have been developed. This study compared recovery of quantitative myocardial blood flow (MBF) after different CTO percutaneous coronary intervention techniques. Methods: Consecutive patients with [15O]H2O positron emission tomography perfusion imaging before and 3 months after successful CTO percutaneous coronary intervention between 2013 and 2018 were included. Changes in hyperemic MBF, coronary flow reserve, and perfusion defect size were compared between antegrade wire escalation, retrograde wire escalation, antegrade dissection and reentry (ADR), and retrograde dissection and reentry. Results: One hundred ninety-three patients were treated with antegrade wire escalation (N=90), retrograde wire escalation (N=24), ADR (N=35), and retrograde dissection and reentry (N=44). Increase in hyperemic MBF (1.19±0.77, 0.94±0.65, 1.09±0.63, and 1.02±0.75 mL·min-1·g-1, respectively; P =0.40) and coronary flow reserve (1.34±1.08, 1.14±1.09, 1.31±0.96, and 1.24±0.99, respectively; P =0.84) and decrease in defect size (3.2±2.1, 3.0±2.2, 2.7±2.1, and 2.9±1.9 segments, respectively; P =0.77) were comparable between the 4 approaches. In addition, recovery of hyperemic MBF was less pronounced after subintimal crossing with knuckle-wire-technique compared with CrossBoss in controlled ADR and retrograde dissection and reentry (0.93±0.69 versus 1.54±0.65 mL·min-1·g-1, P =0.02), and less after reentry using subintimal tracking and reentry in ADR compared with controlled ADR (Stingray) or limited antegrade subintimal tracking (0.60±0.53 versus 1.18±0.54 [ P =0.04] and versus 1.49±0.57 mL·min-1·g-1, [ P <0.01]). Conclusions: Recovery of hyperemic MBF, coronary flow reserve, and perfusion defect size after CTO percutaneous coronary intervention was comparable between different approaches. Although sometimes necessary to cross a complex CTO lesion, subintimal knuckle wiring and subintimal tracking and reentry resulted in less hyperemic MBF improvement compared with other subintimal crossing and reentry techniques. [ABSTRACT FROM AUTHOR]

Background: The main goal of coronary revascularization is to restore myocardial perfusion in case of ischemia, causing coronary artery disease. Yet, little is known on the effect of revascularization on absolute myocardial blood flow (MBF). Therefore, the present prospective study assesses the impact of coronary revascularization on absolute MBF as measured by [15O]H2O positron emission tomography and fractional flow reserve (FFR) in patients with stable coronary artery disease. Methods and Results: Fifty-three patients (87% men, mean age 58.7±9.0 years) with suspected coronary artery disease were included prospectively. All patients underwent serial [15O]H2O positron emission tomography perfusion imaging at baseline and after revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. FFR was routinely measured at baseline and directly post-PCI. After revascularization, regional rest and stress MBF improved from 0.77±0.16 to 0.86±0.25 mL/min/g and from 1.57±0.59 to 2.48±0.91 mL/min/g, respectively, yielding an increase in coronary flow reserve from 2.02±0.69 to 2.94±0.94 (P<0.01 for all). Mean FFR at baseline improved post-PCI from 0.61±0.17 to 0.89±0.08 (P<0.01). After PCI, an increase in FFR paralleled improvement in absolute myocardial perfusion as reflected by stress MBF and coronary flow reserve (r = 0.74 and r = 0.71, respectively, P<0.01 for both). PCI demonstrated a greater improvement of regional stress MBF as compared with coronary artery bypass graft surgery (1.14±1.11 versus 0.66±0.69 mL/min/g, respectively, P=0.02). However, patients undergoing bypass grafting had a more advanced stage of coronary artery disease and more incomplete revascularizations. Conclusion: Successful coronary revascularization has a significant and positive impact on absolute myocardial perfusion as assessed by serial quantitative [15O]H2O positron emission tomography. Notably, improvement of FFR after PCI was directly related to the increase in hyperemic MBF. [ABSTRACT FROM AUTHOR]

Background: Coronary flow capacity (CFC) is a measure that integrates hyperemic myocardial blood flow and coronary flow reserve to quantify the pathophysiological impact of coronary artery disease on vasodilator capacity. This study explores the prognostic value of modified CFC derived from [ 15 O]H 2 O positron emission tomography perfusion imaging., Methods: Quantitative rest/stress perfusion measurements were obtained from 1300 patients with known or suspected coronary artery disease. Patients were classified as having myocardial steal (n=38), severely reduced CFC (n=141), moderately reduced CFC (n=394), minimally reduced CFC (n=245), or normal flow (n=482) using previously defined thresholds. The end point was a composite of death and nonfatal myocardial infarction., Results: During a median follow-up of 5.5 (interquartile range, 3.7-7.8) years, the end point occurred in 153 (12%) patients. Myocardial steal (hazard ratio [HR], 6.70 [95% CI, 3.21-13.99]; P <0.001), severely reduced CFC (HR, 2.35 [95% CI, 1.16-4.78]; P =0.018), and moderately reduced CFC (HR, 1.95 [95% CI, 1.11-3.41]; P =0.020) were associated with worse prognosis compared with normal flow, after adjusting for clinical characteristics. Similarly, in the overall population, increased resting myocardial blood flow (HR, 3.05 [95% CI, 1.68-5.54]; P <0.001), decreased hyperemic myocardial blood flow (HR, 0.68 [95% CI, 0.52-0.90]; P =0.007) and decreased coronary flow reserve (HR, 0.55 [95% CI, 0.42-0.71]; P <0.001) were independently associated with adverse outcome. In a model adjusted for the combined use of perfusion metrics, modified CFC demonstrated independent prognostic value (overall P =0.017)., Conclusions: [ 15 O]H 2 O positron emission tomography-derived resting myocardial blood flow, hyperemic myocardial blood flow, coronary flow reserve, and CFC are prognostic factors for death and nonfatal myocardial infarction in patients with known or suspected coronary artery disease. Importantly, after adjustment for clinical characteristics and the combined use of [ 15 O]H 2 O positron emission tomography perfusion metrics, modified CFC remained independently associated with adverse outcome., Competing Interests: Disclosures None.

Background: A pathophysiological interplay exists between plaque morphology and coronary physiology. Machine learning (ML) is increasingly being applied to coronary computed tomography angiography (CCTA) for cardiovascular risk stratification. We sought to assess the performance of a ML score integrating CCTA-based quantitative plaque features for predicting vessel-specific ischemia by invasive fractional flow reserve (FFR) and impaired myocardial blood flow (MBF) by positron emission tomography (PET)., Methods: This post-hoc analysis of the PACIFIC trial (Prospective Comparison of Cardiac Positron Emission Tomography/Computed Tomography [CT]' Single Photon Emission Computed Tomography/CT Perfusion Imaging and CT Coronary Angiography with Invasive Coronary Angiography) included 208 patients with suspected coronary artery disease who prospectively underwent CCTA' [ 15 O]H 2 O PET, and invasive FFR. Plaque quantification from CCTA was performed using semiautomated software. An ML algorithm trained on the prospective NXT trial (484 vessels) was used to develop a ML score for the prediction of ischemia (FFR≤0.80), which was then evaluated in 581 vessels from the PACIFIC trial. Thereafter, the ML score was applied for predicting impaired hyperemic MBF (≤2.30 mL/min per g) from corresponding PET scans. The performance of the ML score was compared with CCTA reads and noninvasive FFR derived from CCTA (FFR CT )., Results: One hundred thirty-nine (23.9%) vessels had FFR-defined ischemia, and 195 (33.6%) vessels had impaired hyperemic MBF. For the prediction of FFR-defined ischemia, the ML score yielded an area under the receiver-operating characteristic curve of 0.92, which was significantly higher than that of visual stenosis grade (0.84; P <0.001) and comparable with that of FFR CT (0.93; P =0.34). Quantitative percent diameter stenosis and low-density noncalcified plaque volume had the greatest ML feature importance for predicting FFR-defined ischemia. When applied for impaired MBF prediction, the ML score exhibited an area under the receiver-operating characteristic curve of 0.80; significantly higher than visual stenosis grade (area under the receiver-operating characteristic curve 0.74; P =0.02) and comparable with FFR CT (area under the receiver-operating characteristic curve 0.77; P =0.16)., Conclusions: An externally validated ML score integrating CCTA-based quantitative plaque features accurately predicts FFR-defined ischemia and impaired MBF by PET, performing superiorly to standard CCTA stenosis evaluation and comparably to FFR CT .

Background: Coronary pressure indices such as fractional flow reserve are the standard for guiding elective revascularization. However, considering additional coronary flow parameters could further individualize and optimize the decision on revascularization. We aimed to investigate the potentially differential prognostic associations of elective percutaneous coronary intervention (PCI) according to coronary flow properties represented by coronary flow reserve (CFR), coronary flow capacity (CFC), and baseline CFC (bCFC)., Methods: From the ILIAS Registry (Inclusive Invasive Physiological Assessment in Angina Syndromes) composed of 16 hospitals globally from 7 countries, patients with obstructive coronary artery disease who underwent invasive coronary physiological assessment were included (N=2370 vessels). We assessed effect measure modifications of the association of PCI and 5-year target vessel failure according to CFR, CFC, and bCFC either assessed by Doppler-technique or thermodilution-method., Results: The mean age of the population was 63.3 years, and there were 1322 (73.6%) males. Median fractional flow reserve was 0.85, and PCI was performed in 600 (25.3%) vessels. Reduced CFR, CFC, and abnormal bCFC were defined in 988 (41.7%), 542 (22.9%), and 600 (25.3%) vessels, respectively. Significant effect measure modifications were observed by CFC either in odds ratio ( P =0.0018), additive ( P =0.029), and hazard ratio scale ( P =0.0002). The absolute risk of 5-year target-vessel failure was higher if treated by PCI in vessels with normal CFC by 1.8 (-1.7 to 5.3) percent, while that was lower by -5.9 (-12 to -0.1) percent in those with reduced CFC. CFR and bCFC were not significant effect modifiers in any scales. Similar associations were observed in per-patient analyses, whereas the findings were less robust., Conclusions: We observed qualitative effect measure modification of PCI and 5-year clinical outcomes according to CFC status in additive scale. CFR and bCFC were not robust effect modifiers. Therefore, CFC could be potentially used to optimize the patient selection for elective PCI treatment combined with fractional flow reserve.

Outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI) have improved because of advancements in equipment and techniques. With global collaboration and knowledge sharing, we have identified 7 common principles that are widely accepted as best practices for CTO-PCI.  1. Ischemic symptom improvement is the primary indication for CTO-PCI.  2. Dual coronary angiography and in-depth and structured review of the angiogram (and, if available, coronary computed tomography angiography) are key for planning and safely performing CTO-PCI.  3. Use of a microcatheter is essential for optimal guidewire manipulation and exchanges.  4. Antegrade wiring, antegrade dissection and reentry, and the retrograde approach are all complementary and necessary crossing strategies. Antegrade wiring is the most common initial technique, whereas retrograde and antegrade dissection and reentry are often required for more complex CTOs.  5. If the initially selected crossing strategy fails, efficient change to an alternative crossing technique increases the likelihood of eventual PCI success, shortens procedure time, and lowers radiation and contrast use.  6. Specific CTO-PCI expertise and volume and the availability of specialized equipment will increase the likelihood of crossing success and facilitate prevention and management of complications, such as perforation.  7. Meticulous attention to lesion preparation and stenting technique, often requiring intracoronary imaging, is required to ensure optimum stent expansion and minimize the risk of short- and long-term adverse events. These principles have been widely adopted by experienced CTO-PCI operators and centers currently achieving high success and acceptable complication rates. Outcomes are less optimal at less experienced centers, highlighting the need for broader adoption of the aforementioned 7 guiding principles along with the development of additional simple and safe CTO crossing and revascularization strategies through ongoing research, education, and training.

Background: The main goal of coronary revascularization is to restore myocardial perfusion in case of ischemia, causing coronary artery disease. Yet, little is known on the effect of revascularization on absolute myocardial blood flow (MBF). Therefore, the present prospective study assesses the impact of coronary revascularization on absolute MBF as measured by [ 15 O]H 2 O positron emission tomography and fractional flow reserve (FFR) in patients with stable coronary artery disease., Methods and Results: Fifty-three patients (87% men, mean age 58.7±9.0 years) with suspected coronary artery disease were included prospectively. All patients underwent serial [ 15 O]H 2 O positron emission tomography perfusion imaging at baseline and after revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. FFR was routinely measured at baseline and directly post-PCI. After revascularization, regional rest and stress MBF improved from 0.77±0.16 to 0.86±0.25 mL/min/g and from 1.57±0.59 to 2.48±0.91 mL/min/g, respectively, yielding an increase in coronary flow reserve from 2.02±0.69 to 2.94±0.94 ( P <0.01 for all). Mean FFR at baseline improved post-PCI from 0.61±0.17 to 0.89±0.08 ( P <0.01). After PCI, an increase in FFR paralleled improvement in absolute myocardial perfusion as reflected by stress MBF and coronary flow reserve ( r = 0.74 and r = 0.71, respectively, P <0.01 for both). PCI demonstrated a greater improvement of regional stress MBF as compared with coronary artery bypass graft surgery (1.14±1.11 versus 0.66±0.69 mL/min/g, respectively, P =0.02). However, patients undergoing bypass grafting had a more advanced stage of coronary artery disease and more incomplete revascularizations., Conclusion: Successful coronary revascularization has a significant and positive impact on absolute myocardial perfusion as assessed by serial quantitative [ 15 O]H 2 O positron emission tomography. Notably, improvement of FFR after PCI was directly related to the increase in hyperemic MBF., (© 2018 American Heart Association, Inc.)

Background: A total of 40% to 50% of patients with ST-segment-elevation myocardial infarction develop microvascular injury (MVI) despite angiographically successful primary percutaneous coronary intervention (PCI). We investigated whether hyperemic microvascular resistance (HMR) immediately after angiographically successful PCI predicts MVI at cardiovascular magnetic resonance and reduced myocardial blood flow at positron emission tomography (PET)., Methods and Results: Sixty patients with ST-segment-elevation myocardial infarction were included in this prospective study. Immediately after successful PCI, intracoronary pressure-flow measurements were performed and analyzed off-line to calculate HMR and indices derived from the pressure-velocity loops, including pressure at zero flow. Cardiovascular magnetic resonance and H2 (15)O PET imaging were performed 4 to 6 days after PCI. Using cardiovascular magnetic resonance, MVI was defined as a subendocardial recess of myocardium with low signal intensity within a gadolinium-enhanced area. Myocardial perfusion was quantified using H2 (15)O PET. Reference HMR values were obtained in 16 stable patients undergoing coronary angiography. Complete data sets were available in 48 patients of which 24 developed MVI. Adequate pressure-velocity loops were obtained in 29 patients. HMR in the culprit artery in patients with MVI was significantly higher than in patients without MVI (MVI, 3.33±1.50 mm Hg/cm per second versus no MVI, 2.41±1.26 mm Hg/cm per second; P=0.03). MVI was associated with higher pressure at zero flow (45.68±13.16 versus 32.01±14.98 mm Hg; P=0.015). Multivariable analysis showed HMR to independently predict MVI (P=0.04). The optimal cutoff value for HMR was 2.5 mm Hg/cm per second. High HMR was associated with decreased myocardial blood flow on PET (myocardial perfusion reserve <2.0, 3.18±1.42 mm Hg/cm per second versus myocardial perfusion reserve ≥2.0, 2.24±1.19 mm Hg/cm per second; P=0.04)., Conclusions: Doppler-flow-derived physiological indices of coronary resistance (HMR) and extravascular compression (pressure at zero flow) obtained immediately after successful primary PCI predict MVI and decreased PET myocardial blood flow., Clinical Trial Registration Url: http://www.trialregister.nl. Unique identifier: NTR3164., (© 2015 American Heart Association, Inc.)

Background: In idiopathic pulmonary arterial hypertension (IPAH), increased right ventricular (RV) power is required to maintain cardiac output. For this, RV O2 consumption (MVO2) must increase by augmentation of O2 supply and/or improvement of mechanical efficiency-ratio of power output to MVO2. In IPAH with overt RV failure, however, there is evidence that O2 supply (perfusion) reserve is reduced, leaving only increase in either O2 extraction or mechanical efficiency as compensatory mechanisms. We related RV mechanical efficiency to clinical and hemodynamic parameters of RV function in patients with IPAH and associated it with glucose metabolism., Methods and Results: The patients included were in New York Heart Association (NYHA) class II (n=8) and class III (n=8). They underwent right heart catheterization, MRI, and H2(15)O-, (15)O2-, C(15)O-, and 18FDG-PET. RV power and O2 supply were similar in both groups (NYHA class II versus class III: 0.54±0.14 versus 0.47±0.12 J/s and 0.109±0.022 versus 0.128±0.026 mL O2/min per gram, respectively). RV O2 extraction was near-significantly lower in NYHA class II compared with NYHA class III (63±17% versus 75±16%, respectively, P=0.10). As a result, MVO2 was significantly lower (0.066±0.012 versus 0.092±0.010 mL O2/min per gram, respectively, P=0.006). RV efficiency was reduced in NYHA class III (13.9±3.8%) compared with NYHA class II (27.8±7.6%, P=0.001). Septal bowing, measured by MRI, correlated with RV efficiency (r = -0.59, P=0.020). No relation was found between RV efficiency and glucose uptake rate. RV mechanical efficiency and ejection fraction were closely related (r=0.81, P<0.001)., Conclusions: RV failure in IPAH was associated with reduced mechanical efficiency that was partially explained by RV mechanical dysfunction but not by a metabolic shift.

Background: Myocardial washout kinetics of carbon-11 labelled acetate ([11C]acetate) by positron emission tomography (PET) closely correlate with myocardial oxygen consumption (MVO2). Analysis of the tissue time activity curve by conventional monoexponential curve fitting, however, does not account for spillover effects and recirculating 11C activity. In theory, a compartment model considering variations of the arterial input function and metabolic 11C contamination, could improve consistency of MVO2 estimations. The objective of the study was to investigate this hypothesis., Methods: Nineteen healthy volunteers were studied under resting conditions with [11C]acetate PET. Time activity curves were analysed by automated monoexponential curve fitting and a single-tissue compartment model to obtain Kmono and k2, as noninvasive indices of MVO2. Subsequently, Kmono and k2 were related to the rate-pressure product, as an indirect marker of MVO2., Results: The rate-pressure product was significantly correlated to Kmono (r=0.46, P=0.047) and k2 (r=0.75, P<0.001)., Conclusion: The results of this study suggest that a single-tissue compartment model yields more accurate noninvasive estimates of MVO2 by the use of [11C]acetate PET in humans, in comparison with monoexponential curve fitting.