Sex Differences in pLVAD-Assisted High-Risk Percutaneous Coronary Intervention: Insights From the PROTECT III Study.

BACKGROUND: Prior studies have found that female patients have worse outcomes following high-risk percutaneous coronary intervention (HRPCI). OBJECTIVES: The authors sought to evaluate sex-based differences in patient and procedural characteristics, clinical outcomes, and safety of Impella-supported HRPCI in the PROTECT III study. METHODS: We evaluated sex-based differences in the PROTECT III study; a prospective, multicenter, observational study of patients undergoing Impella-supported HRPCI. The primary outcome was 90-day major adverse cardiac and cerebrovascular events (MACCE)-the composite of all-cause death, myocardial infarction, stroke/transient ischemic attack, and repeat revascularization. RESULTS: From March 2017 to March 2020, 1,237 patients (27% female) were enrolled. Female patients were older, more often Black, more often anemic, and had more prior strokes and worse renal function, but higher ejection fractions compared to male patients. Preprocedural SYNTAX score was similar between sexes (28.0 ± 12.3). Female patients were more likely to present with acute myocardial infarction (40.7% vs 33.2%; P = 0.02) and more often had femoral access used for PCI and nonfemoral access used for Impella device implantation. Female patients had higher rates of immediate PCI-related coronary complications (4.2% vs 2.1%; P = 0.004) and a greater drop in SYNTAX score post-procedure (-22.6 vs -21.0; P = 0.04). There were no sex differences in 90-day MACCE, vascular complications requiring surgery, major bleeding, or acute limb ischemia. After adjustment using propensity matching and multivariable regression, immediate PCI-related complications was the only safety or clinical outcome that was significantly different by sex. CONCLUSIONS: In this study, rates of 90-day MACCE compared favorably to prior cohorts of HRPCI patients and there was no significant sex differences. (The PROTECT III Study is a substudy of The Global cVAD Study [cVAD]; NCT04136392).

Development of a Novel Score to Predict Urgent Mechanical Circulatory Support in Chronic Total Occlusion Percutaneous Coronary Intervention.

Estimating the likelihood of urgent mechanical circulatory support (MCS) can facilitate procedural planning and clinical decision-making in chronic total occlusion (CTO) percutaneous coronary intervention (PCI). We analyzed 2,784 CTO PCIs performed between 2012 and 2021 at 12 centers. The variable importance was estimated by a bootstrap applying a random forest algorithm to a propensity-matched sample (a ratio of 1:5 matching cases with controls on center). The identified variables were used to predict the risk of urgent MCS. The performance of the risk model was assessed in-sample and on 2,411 out-of-sample procedures that did not require urgent MCS. Urgent MCS was used in 62 (2.2%) of cases. Patients who required urgent MCS were older (70 [63 to 77] vs 66 [58 to 73] years, p = 0.003) compared with those who did not require urgent MCS. Technical (68% vs 87%, p <0.001) and procedural success (40% vs 85%, p <0.001) was lower in the urgent MCS group compared with cases that did not require urgent MCS. The risk model for urgent MCS use included retrograde crossing strategy, left ventricular ejection fraction, and lesion length. The resulting model demonstrated good calibration and discriminatory capacity with the area under the curve (95% confidence interval) of 0.79 (0.73 to 0.86) and specificity and sensitivity of 86% and 52%, respectively. In the out-of-sample set, the specificity of the model was 87%. The Prospective Global Registry for the Study of Chronic Total Occlusion Intervention CTO MCS score can help estimate the risk of urgent MCS use during CTO PCI.

Angiographic Features and Clinical Outcomes of Balloon Uncrossable Lesions during Chronic Total Occlusion Percutaneous Coronary Intervention.

Background: Balloon uncrossable lesions are defined as lesions that cannot be crossed with a balloon after successful guidewire crossing. Methods: We analyzed the association between balloon uncrossable lesions and procedural outcomes of 8671 chronic total occlusions (CTOs) percutaneous coronary interventions (PCIs) performed between 2012 and 2022 at 41 centers. Results: The prevalence of balloon uncrossable lesions was 9.2%. The mean patient age was 64.2 ± 10 years and 80% were men. Patients with balloon uncrossable lesions were older (67.3 ± 9 vs. 63.9 ± 10, p < 0.001) and more likely to have prior coronary artery bypass graft surgery (40% vs. 25%, p < 0.001) and diabetes mellitus (50% vs. 42%, p < 0.001) compared with patients who had balloon crossable lesions. In-stent restenosis (23% vs. 16%. p < 0.001), moderate/severe calcification (68% vs. 40%, p < 0.001), and moderate/severe proximal vessel tortuosity (36% vs. 25%, p < 0.001) were more common in balloon uncrossable lesions. Procedure time (132 (90, 197) vs. 109 (71, 160) min, p < 0.001) was longer and the air kerma radiation dose (2.55 (1.41, 4.23) vs. 1.97 (1.10, 3.40) min, p < 0.001) was higher in balloon uncrossable lesions, while these lesions displayed lower technical (91% vs. 99%, p < 0.001) and procedural (88% vs. 96%, p < 0.001) success rates and higher major adverse cardiac event (MACE) rates (3.14% vs. 1.49%, p < 0.001). Several techniques were required for balloon uncrossable lesions. Conclusion: In a contemporary, multicenter registry, 9.2% of the successfully crossed CTOs were initially balloon uncrossable. Balloon uncrossable lesions exhibited lower technical and procedural success rates and a higher risk of complications compared with balloon crossable lesions.

Use of Mechanical Circulatory Support in Chronic Total Occlusion Percutaneous Coronary Intervention.

The use of mechanical circulatory support (MCS) in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) has received limited study. We analyzed the clinical and angiographic characteristics, and procedural outcomes of 7,171 CTO PCIs performed between 2012 and 2021 at 35 international centers. Mean age was 64.5 ± 10 years, mean left ventricular ejection fraction was 50 ± 13%. MCS was used in 4.5%, prophylactically in 78.7%, and urgently in 21.3%. The most common type of MCS overall was Impella CP (Abiomed) (55.5%), followed by intra-aortic balloon pump (14.8%) and TandemHeart (LivaNova Inc.) (10.0%). Prophylactic MCS patients were more likely to have diabetes mellitus (55% vs 42%, p <0.001) and had more complex lesions compared with cases without prophylactic MCS (Japan-CTO score: 2.80 ± 1.22 vs 2.39 ± 1.27, p <0.001). Cases with prophylactic MCS had similar technical (86% vs 87%, p = 0.643) but lower procedural (80% vs 86%, p = 0.028) success rates and higher rates of periprocedural major cardiac adverse events compared with no prophylactic MCS use (6.55% vs 1.68%, p <0.001). Urgent MCS use was associated with lower technical (68% vs 87%, p <0.001) and procedural (39% vs 86%, p <0.001) success rates and higher major cardiac adverse events compared with no-MCS use (32.26% vs 1.68%, p <0.001). The differences persisted in multivariable analyses. In summary, in this contemporary multicenter registry, MCS was used in 4.5% of CTO PCIs, mostly prophylactically (78.7%). Elective MCS cases had similar technical success but a higher risk of complications. Urgent MCS cases had lower technical and procedural success and higher periprocedural major complication rates.

Decision-Making During Percutaneous Coronary Intervention Guided by Optical Coherence Tomography: Insights From the LightLab Initiative.

BACKGROUND: Use of intracoronary imaging is associated with improved outcomes in patients undergoing percutaneous coronary intervention (PCI). Yet, the impact of intracoronary imaging on real-time physician decision-making during PCI is not fully known. METHODS: The LightLab Initiative is a multicenter, prospective, observational study designed to characterize the use of a standardized optical coherence tomography (OCT) workflow during PCI. Participating physicians performed pre-PCI and post-PCI OCT in accordance with this workflow and operator assessments of lesion characteristics and treatment plan were recorded for each lesion based on angiography alone and following OCT. Physicians were categorized as having low (n=15), intermediate (n=13), or high (n=14) OCT use in the year preceding participation. RESULTS: Among 925 patients with 1328 lesions undergoing PCI, the prescribed OCT workflow was followed in 773 (84%) of patients with 836 lesions. Operator lesion assessment and decision-making during PCI changed with OCT use in 86% (721/836) of lesions. Pre-PCI OCT use changed operator decision-making in 80% of lesions, including lesion assessment (45%), vessel preparation strategy (27%), stent diameter (37%), and stent length (36%). Post-PCI OCT changed stent optimization decision-making in 31% of lesions. These findings were consistent across strata of physician prior OCT experience. CONCLUSIONS: A standardized OCT workflow impacted PCI decision-making in 86% of lesions, with a predominant effect on pre-PCI lesion assessment and planning of treatment strategy. This finding was consistent regardless of operator experience level and provides insight into mechanisms by which intravascular imaging might improve PCI outcomes.

Single-access for Impella-supported percutaneous coronary intervention using a sheathless technique with an 8 Fr guide.

Complex and higher-risk indicated percutaneous coronary interventions at times require mechanical circulatory support, most often with Impella devices. The use of such devices traditionally required additional arterial access site(s), increasing risk of vascular complications. The Single-access for Hi-risk percutaneous coronary intervention (SHiP) technique was described to overcome this issue but was limited to the use of 7F guides. Larger 8F guides often provide incremental support and space compared to 7F guides, sometimes needed in complex procedures. We described a modified SHiP technique using an 8 Fr guide delivered sheathless using Rotaglide.

Practice Patterns in the Interventional Treatment of Coronary Bifurcation Lesions: A Global Survey.

OBJECTIVES: The study aim was to assess current procedural strategies and perceptions for percutaneous coronary intervention (PCI) involving bifurcations. METHODS: We distributed an online survey via email (8050 invitations) and social media. RESULTS: Among 440 responders, median annual PCI volumes were 15 cases (interquartile range [IQR], 10-29 cases) for left main (LM) and 50 cases (IQR, 27-73 cases) for non-LM (nLM) bifurcation lesions. Radial access use was reported in 51% of LM and 82% of nLM cases. An upfront 2-stent strategy, most commonly double-kissing (DK) crush, was reported in 49% of LM and 29% of nLM lesions. Bailout stenting during provisional stenting was reported in 26% of LM-PCIs, usually using the T and protrusion technique. In provisional stenting cases, most operators (<35%) did not report predilating the side branch, but routinely postdilated after successful provisional stenting (>85%), most often using both kissing-balloon inflation and the proximal optimization technique. Intravascular imaging was used in 80% of LM and 46% of nLM cases. CONCLUSIONS: Among the survey responders, the DK crush technique was the most frequently used 2-stent strategy for bifurcation PCIs. For LM lesions, bailout stenting was performed after provisional strategy in approximately 25% of cases. For nLM lesions, use of intravascular imaging and coronary physiology was lower than for LM lesions.

Strategies for Reducing Vascular and Bleeding Risk for Percutaneous Left Ventricular Assist Device-supported High-risk Percutaneous Coronary Intervention.

In patients at high risk for haemodynamic instability during percutaneous coronary intervention (PCI), practitioners are increasingly opting for prophylactic mechanical circulatory support, such as the Impella® heart pump (Abiomed, Danvers, MA, USA). Though Impella-supported high-risk PCI (HRPCI) ensures haemodynamic stability during the PCI procedure, access-related complication rates have varied significantly in published studies. Reported variability in complication rates relates to many factors, including anticoagulation practices, access and closure strategy, post-procedure care and variations in event definitions. This article aims to outline optimal strategies to minimize vascular and bleeding complications during Impella-supported HRPCI based on previously identified clinical, procedural and postprocedural risk factors. Practices to reduce complications include femoral skills training, standardized protocols to optimize access, closure, anticoagulation management and post-procedural care, as well as the application of techniques and technological advances. Protocols integrating these strategies to mitigate access-related bleeding and vascular complications for Impella-supported procedures can markedly limit vascular access risk as a barrier to appropriate large-bore mechanical circulatory support use in HRPCI.

Dry Field Closure of Large-Bore Access With Iliac Artery Angioplasty Through the Ipsilateral Sheath: The Single-Access Dry-Closure Technique.

The use of large-bore sheaths has risen exponentially in the last decade partly due to the growth of structural heart interventions and various mechanical circulatory support options. Meanwhile, the interventional community has gradually shifted from an open surgical to endovascular closure. However, vascular access complications and bleeding still remain a significant risk. Various techniques involving an additional access site have been described to allow for endovascular bailout of potential complications. However, these by themselves create an additional burden to procedural morbidity. Furthermore, the weight of additional procedural time, contrast, radiation and the need for advanced peripheral endovascular skills constitute considerable downsides to the "second arterial access" strategy. For that reason, we propose an alternative strategy, the "single-access dry-closure" technique, which provides vascular access control without the additional burden and risk of a second arterial access. This involves the use of low-pressure iliac artery occlusive angioplasty, delivered through the ipsilateral sheath during the endovascular closure. We hereby describe the steps, advantages and disadvantages of this novel technique. We also include the description of multiple technical variations depending on the use of one or two preclosed Proglide devices. This novel approach seems to be a safe, effective, simple, fast and economical technique that has the potential to decrease procedural morbidity by avoiding an additional arterial access. It also lowers contrast volume and radiation exposure while improving the overall set-up and operator ergonomics.

An algorithmic approach to balloon-uncrossable coronary lesions.

Balloon uncrossable coronary lesions are lesions that cannot be crossed with a balloon after successful guidewire crossing. The strategies used to facilitate the treatment of such lesions can be classified into strategies that provide lesion modification and strategies that increase support. We describe a systematic, algorithmic approach to treat balloon uncrossable lesions, starting with use of small balloons, followed by increase in guide catheter support, use of microcatheters, wire cutting or puncture techniques, laser, atherectomy, and subintimal modification techniques. Sequential and simultaneous application of the aforementioned techniques can result in successful treatment of these challenging lesions.

The Single-access for Hi-risk PCI (SHiP) technique.

Currently, the Impella CP (Abiomed, Danvers, Massachusetts) percutaneous ventricular assist catheter requires implantation through a 14 French sheath. Additional arterial access is commonly obtained to perform therapeutic or diagnostic procedures. Multiple arterial access requires time and results in increased risk for vascular complications. Some patients may have limited arterial access. We describe the Single-access for Hi-risk PCI (SHiP) technique to allow for rapid and safer single access utilizing only the Impella access site. After the Impella catheter is placed in the standard fashion, a micropuncture needle is used to pierce the hemostasis valve of the Impella insertion sheath. After dilating the hemostasis valve and exchanging for a 0.035″ wire, up to a 7 French sheath can be inserted for PCI within the 14 French access sheath and alongside the 9 French portion of the Impella catheter. After PCI, the sheath is removed. We report on a case series of 17 patients using this technique. There were no instances of bleeding during the procedure or after removal of the PCI sheath, and no evidence of disruption of the Impella sheath.

Myocardial viability mapping by magnetic resonance-based multiparametric systolic strain analysis.

BACKGROUND: Regional myocardial contractility can be characterized by three-dimensional left ventricular (LV) multiparametric strain maps generated from sequential magnetic resonance imaging of radiofrequency tissue-tagging grid point displacements. METHODS: Normal average and standard deviation values for each of three strain indices at 15,300 LV points were determined from a normal volunteer human strain database (n = 50) by application of magnetic resonance-based three-dimensional strain analysis. Patient-specific multiparametric strain data from each ischemic cardiomyopathy patient (n = 20) were then submitted to a point-by-point comparison (n = 15,300 LV points) to the normal strain database. The resulting 15,300 composite multiparametric Z-score values (standard deviation from normal average) were color-contour mapped over patient-specific three-dimensional LV geometry to detect the abnormal contractile patterns associated with myocardial infarction and nonviable myocardium. RESULTS: The average multiparametric strain composite Z-score from each LV region (n = 120) was compared with the respective clinical standard viability testing result and used to construct a receiver-operator characteristic curve. The area under the curve was 0.941 (p < 0.001; 95% confidence interval: 0.897 to 0.985). A regional average Z-score threshold of 1.525 (> 1.525 being nonviable) resulted in a sensitivity of 90% and a specificity of 90%. Corresponding positive and negative predictive values were 84% and 95%, respectively. CONCLUSIONS: The clinical application of magnetic resonance-based multiparametric strain analysis allowed accurate regional characterization and visualization of LV myocardial viability.

From randomized trials to routine clinical practice: an evidence-based approach for the use of drug-eluting stents.

The availability of drug-eluting stents has resulted in a paradigm shift in the management of patients with coronary artery disease with a substantial increase in the percentage of patients being revascularized percutaneously rather than surgically. Since its introduction, there has been a tremendous increase in the use of drug-eluting stents with nearly 90% of patients in the US who undergo percutaneous interventions receiving drug-eluting stents. The promising results of several randomized trials that demonstrated a profound reduction in restenosis rates compared with bare-metal stents, underscores the unprecedented enthusiasm among the cardiology community to adopt this new technology swiftly. Data regarding the safety and superiority of drug-eluting stents abound, and it is imperative for the practicing clinician to review and apply them in appropriate clinical settings. In this review, we present general concepts of drug-eluting stents, and attempt to summarize the available data on the approved drug-eluting stents in a variety of patient and lesion subsets. In addition, we share some insights regarding the potential limitations, and issues specific to drug-eluting stents.

Left ventricular wall stress in patients with severe aortic insufficiency with finite element analysis.

BACKGROUND: Severe aortic insufficiency (AI) with preserved left ventricular (LV) function may be associated with a long asymptomatic period and unpredictable course on medical therapy. Since myocardial wall stress is closely related to both pathologic cardiac remodeling and ultimately to LV decompensation, a more accurate description of regional wall stress may improve our ability to appropriately manage these patients. The objective of this study was to define differences in instantaneous global and regional three-dimensional end-systolic maximum principal stress (ESS) between normal patients and patients with AI, both before and after aortic valve replacement (AVR) using magnetic resonance imaging (MRI) and finite element analysis (FEA). METHODS: Magnetic resonance imaging was performed on 20 normal volunteers and 14 patients with moderate to severe AI with normal systolic function (ejection fraction: 57 +/- 0.6) before and after AVR. Finite element analysis was utilized to estimate global and regional ESS. RESULTS: Both global (p < 0.001) and regional (p < 0.001 in all segments) ESS were significantly higher in the preoperative AI patients when compared with their postoperative values and normal controls. Postoperative ESS was significantly lower than the normal controls (p = 0.002). CONCLUSIONS: Three-dimensional regional and global end-systolic LV wall stress can be determined by MRI and finite element analysis. Values of ESS in patients with chronic AI were elevated prior to AVR and normalized after AVR. This method may have considerable potential as a noninvasive, clinically applicable index of regional LV geometry and function that may help with the serial evaluation of patients with AI.

Low-dose dobutamine tissue-tagged magnetic resonance imaging with 3-dimensional strain analysis allows assessment of myocardial viability in patients with ischemic cardiomyopathy.

BACKGROUND: Tissue-tagged magnetic resonance imaging (MRI) with 3-dimensional (3D) myocardial strain analysis allows quantitative assessment of myocardial contractility. We assessed the hypothesis that 3D strain determination at rest and with low-dose dobutamine would discriminate between viable and nonviable myocardium in patients with ischemic cardiomyopathy (ICM). METHODS AND RESULTS: MRI with radiofrequency tissue-tagging at rest and with low-dose dobutamine was performed in 16 normal volunteers and 14 patients with ICM. Three-dimensional global and regional circumferential strains (Ecc) were computed for all subjects at rest and with dobutamine. Results were compared with clinically indicated conventional viability studies. Compared with normal volunteers, global left ventricular Ecc was significantly decreased in patients with ICM at rest (-0.15+/-0.06 versus -0.27+/-0.03; P<0.001) and with dobutamine (-0.17+/-0.08 versus -0.37+/-0.10; P<0.001). Ecc was significantly decreased in nonviable regions compared with viable segments at rest (-0.08+/-0.06 versus -0.17+/-0.10; P<0.001) and with dobutamine (-0.07+/-0.06 versus -0.21+/-0.11; P<0.001). Ecc in viable segments increased significantly in response to dobutamine (P=0.04), whereas Ecc did not change in nonviable segments (P=0.50). Normal controls (96 segments) had increased Ecc at rest (-0.27+/-0.07) and with dobutamine (-0.37+/-0.15) compared with both viable and nonviable regions in ICM patients (P<0.001). CONCLUSIONS: Noninvasive dobutamine tissue-tagged MRI with calculation of 3D strain allows the identification, quantification and display of regionally varying ventricular function. The response of systolic strain to low-dose dobutamine has significant promise in discriminating between viable and nonviable myocardium.

Aortic valve replacement for aortic insufficiency: valve type as a determinant of systolic strain recovery.

BACKGROUND AND AIM: Left ventricular (LV) 3D systolic strain decreases in absolute value postoperatively and does not recover in patients who undergo aortic valve replacement (AVR) for chronic aortic insufficiency (AI). We investigated whether choice of valve prosthesis (mechanical [St. Jude], bioprosthetic [bovine pericardial], Ross procedure) had a significant impact on strain recovery in this surgical population. METHODS: MRI with tissue-tagging was performed on 14 patients with chronic AI both before and 28 +/- 13 months after AVR. Average values of LV systolic strain and end-systolic stress (ESS) were computed from MRI data for the LV. Three types of prosthetic valve were examined (Ross procedure n = 4, bovine pericardial n = 5, and St. Jude n = 5). RESULTS: Overall, systolic strain, ESS, LV volumes, ejection fraction, and LV mass all changed significantly following AVR. Comparisons between individual valve types revealed no differences in any of these measurements. Patients who received a mechanical valve had a greater decrease in the absolute value of systolic strain following surgery compared to patients from the nonmechanical group (Ross procedure and bioprosthetic valve). Comparisons between the Ross group and the prosthetic group (St. Jude and bioprosthetic) produced no significant differences in strain, ESS, LV volume, and mass. CONCLUSIONS: These early results suggest that valve prosthetic type may be a factor in efforts to improve strain recovery after AVR for AI, although further investigation is warranted. MRI with tissue-tagging may be a useful tool for comparing the impact of prosthetic valve choice on incompletely recovered systolic strain following AVR for chronic AI.

Myocardial systolic strain is decreased after aortic valve replacement in patients with aortic insufficiency.

BACKGROUND: Left ventricular three-dimensional nonlinear systolic strain determinations have potential to detect small decrements in ventricular function in patients with aortic insufficiency before and after aortic valve replacement. METHODS: Magnetic resonance imaging with tissue-tagging was performed on 42 normal volunteers and 14 patients with chronic aortic insufficiency both before and 28 +/- 11 months after aortic valve replacement. Preoperative and postoperative left ventricular volume, dimensions and ejection fraction were determined for all subjects. Left ventricular systolic radial, circumferential, longitudinal, and minimum principal strain were calculated for six left ventricular regions. RESULTS: After aortic valve replacement, left ventricular volume and dimensions decreased significantly (p < 0.001) and ejection fraction increased nonsignificantly (p = 0.096). Strain values in preoperative aortic insufficiency patients did not differ significantly from controls. At an average of 28 +/- 11 months postoperatively, however, regional three-dimensional minimum principal and longitudinal strain was decreased in all six ventricular regions as well as globally (p < 0.03) compared with normal control values. Circumferential strain was significantly decreased globally and in all but two regions (p < 0.03). CONCLUSIONS: These magnetic resonance imaging-based techniques are sensitive enough to detect a previously unrecognized, significant decrease in both global and regional three-dimensional left ventricular systolic strain 2 years after aortic valve replacement for minimally symptomatic chronic aortic insufficiency despite improvement in ejection fraction and a decrease in left ventricular size. The reasons for a significant decline in left ventricular systolic strain after successful aortic valve replacement in minimally symptomatic chronic aortic insufficiency patients are not clear and warrant further investigation.

Angiotensin subtype 1 rReceptor (AT1) blockade improves vasorelaxation in heart failure by up-regulation of endothelial nitric-oxide synthase via activation of the AT2 receptor.

To determine whether angiotensin receptor blockade decreases vascular tone in heart failure by improving endothelial-dependent vasorelaxation and increasing nitric oxide (NO) bioavailability, we treated infarcted adult male Sprague-Dawley rats with candesartan for 7 days or 8 weeks (10 mg/kg/day in drinking water). Candesartan, at both time points, lowered left ventricular (LV) systolic pressure (P < 0.05) (122 +/- 22 versus 74 +/- 16 and 73 +/- 10 mm Hg) and LV dP/dt (5914 +/- 1294 versus 2857 +/- 1672 versus 3175 +/- 769 mm Hg/s), but lowered LV end-diastolic pressure only at 8 weeks (16.9 +/- 9.7 versus 11.2 +/- 5.7 versus 6.9 +/- 5.3 mm Hg). The vasorelaxation response to acetylcholine (ACh) in thoracic aortic segments was decreased with infarction (P < 0.05), remained unchanged with 1 week of candesartan, but increased 84 and 86% at 10-4 and 10-5 M ACh (P < 0.05) at 8 weeks. The enhanced candesartan-induced vasorelaxation at 8 weeks was abolished with NG-nitro-l-arginine methyl ester (200 microM). In bovine pulmonary endothelial cells, 20 microM candesartan increased endothelial nitric-oxide synthase (eNOS) protein levels (P < 0.05) (28.9 +/- 2.6 versus 16.1 +/- 3.7 intensity units/microg of protein); the increased eNOS was abolished by a specific angiotensin subtype 2 (AT2) receptor antagonist, PD 123319. These data suggest that AT1 receptor blockade enhances vasorelaxation in heart failure by increasing NO bioavailability, in part via an AT2 receptor-mediated up-regulation of eNOS protein.