Cerebral emboli detection and autonomous neuromonitoring using robotic transcranial Doppler with artificial intelligence for transcatheter aortic valve replacement with and without embolic protection devices: a pilot study.

BACKGROUND: Periprocedural ischemic stroke remains a serious complication in patients undergoing transcatheter aortic valve replacement (TAVR). We used a novel robotic transcranial Doppler (TCD) system equipped with artificial intelligence (AI) for real-time continuous intraoperative neuromonitoring during TAVR to establish the safety and potential validity of this tool in detecting cerebral emboli, report the quantity and distribution of high intensity transient signals (HITS) with and without cerebral protection, and correlate HITS occurrence with various procedural steps. METHODS: Consecutive patients undergoing TAVR procedures during which the robotic system was used between October 2021 and May 2022 were prospectively enrolled in this pilot study. The robotic TCD system included autonomous adjustment of the TCD probes and AI-assisted post-processing of HITS and other cerebral flow parameters. Basic demographics and procedural details were recorded. Continuous variables were analyzed by a two-sample Mann-Whitney t-test and categorical variables by a χ2 or Fisher test. RESULTS: Thirty-one patients were prospectively enrolled (mean age 79.9±7.6 years; 16 men (51.6%)). Mean aortic valve stenotic area was 0.7 cm2 and mean aortic-ventricular gradient was 43 mmHg (IQR 31.5-50 mmHg). Cerebral protection was used in 16 cases (51.6%). Significantly fewer emboli were observed in the protection group than in the non-protection group (mean 470.38 vs 693.33; p=0.01). Emboli counts during valve positioning and implantation were significantly different in the protection and non-protection groups (mean 249.92 and 387.5, respectively; p=0.01). One (4%) transient ischemic attack occurred post-procedurally in the non-protection group. CONCLUSION: We describe a novel real-time intraoperative neuromonitoring tool used in patients undergoing TAVR. Significantly fewer HITS were detected with protection. Valve positioning-implantation was the most significant stage for intraprocedural HITS.

A Case of Unintentional Release of the Watchman FLX Device During Implantation: A Cautionary Tale.

Atrial fibrillation (AF) is a common heart rhythm disorder that increases the risk of stroke and other cardiovascular complications. The Watchman FLX device is a percutaneous device used for the closure of the left atrial appendage in patients with atrial fibrillation and prevents blood clots from forming, thereby decreasing the risk of stroke. However, device dislodgement during the procedure can occur and compromise the effectiveness of the device. In this case report, we present the experience of an 86-year-old man with a history of atrial fibrillation, coronary artery disease, hypertension, and recent gastrointestinal bleeding due to diverticulosis. During the procedure, the device became dislodged prior to the planned release from the shaft due to the difficult anatomy of the appendage, which caused the operator to over-torque and kink the delivery sheath. The kinked sheath prevented the transmission of torque to the appropriate region of the sheath and caused the device to unscrew prematurely. Fortunately, the device was self-deployed in a satisfactory position, and no further intervention was required. The patient did not experience any complications prior to discharge and follow-up echocardiography showed proper positioning of the device. This case highlights the importance of careful technique during the Watchman FLX procedure and the need to replace the delivery sheath if kinking is noted to prevent unintentional dislodgement of the device. In addition, the case was written with the aid of the artificial intelligence-powered language model ChatGPT and demonstrates its benefits as well as calls for caution while using it for medical writing.

Coronary Obstruction From TAVR in Native Aortic Stenosis: Development and Validation of Multivariate Prediction Model.

BACKGROUND: Transcatheter aortic valve replacement (TAVR)-related coronary artery obstruction prediction remains unsatisfactory despite high mortality and novel preventive therapies. OBJECTIVES: This study sought to develop a predictive model for TAVR-related coronary obstruction in native aortic stenosis. METHODS: Preprocedure computed tomography and fluoroscopy images of patients in whom TAVR caused coronary artery obstruction were collected. Central laboratories made measurements, which were compared with unobstructed patients from a single-center database. A multivariate model was developed and validated against a 1:1 propensity-matched subselection of the unobstructed cohort. RESULTS: Sixty patients with angiographically confirmed coronary obstruction and 1,381 without obstruction were included. In-hospital death was higher in the obstruction cohort (26.7% vs 0.7%; P < 0.001). Annular area and perimeter, coronary height, sinus width, and sinotubular junction height and width were all significantly smaller in the obstructed cohort. Obstruction was most common on the left side (78.3%) and at the level of the coronary artery ostium (92.1%). Coronary artery height and sinus width, but not annulus area, were significant risk factors for obstruction by logistic regression but performed poorly in predicting obstruction. The new multivariate model (coronary obstruction IF cusp height > coronary height, AND virtual valve-to-coronary distance ≤4 mm OR culprit leaflet calcium volume >600 mm3) performed well, with an area under the curve of 0.93 (sensitivity = 0.93, specificity = 0.84) for the left coronary artery and 0.94 (sensitivity = 0.92, specificity = 0.96) for the right. CONCLUSIONS: A novel computed tomography-based multivariate prediction model that can be implemented routinely in real-world practice predicted coronary artery obstruction from TAVR in native aortic stenosis.

Long-term Outcomes of Transcatheter Aortic Valve Replacement With the Lotus Valve vs CoreValve/EvolutR: A Secondary Analysis of the REPRISE III Randomized Clinical Trial.

Importance: Long-term follow-up after transcatheter aortic valve replacement (TAVR) is of interest given that longitudinal data on mortality and durability of transcatheter heart valves are limited. The REPRISE III (Repositionable Percutaneous Replacement of Stenotic Aortic Valve Through Implantation of Lotus Valve System-Randomized Clinical Evaluation) randomized clinical trial compared the mechanically expanded Lotus valve with the self-expanding CoreValve/EvolutR TAVR platforms. Objective: To describe the final 5-year outcomes of the REPRISE III trial. Design, Setting, and Participants: This prespecified secondary analysis assessed the final 5-year clinical, functional, and echocardiographic outcomes of 912 patients from the REPRISE III trial, which was conducted at 55 centers in North America, Europe, and Australia between September 22, 2014, and December 24, 2015. Patients had high risk for aortic stenosis or severe or symptomatic aortic stenosis. Data were analyzed from September 22, 2014, to May 21, 2021. Intervention: Lotus valve or CoreValve/EvolutR TAVR platforms. Main Outcomes and Measures: Valve Academic Research Consortium-2 end points, hemodynamic measures, functional status, and health status were examined through the 5-year follow-up. Results: A total of 912 patients (mean [SD] age, 82.8 [7.3] years; 463 women [50.8%]) were randomized to either the Lotus valve group (n = 607) or CoreValve/EvolutR group (n = 305), with a baseline Society of Thoracic Surgeons risk score of 6.8%. Clinical follow-up data from the REPRISE III trial were available for 581 patients (95.7%) in the Lotus valve group and 285 patients (93.4%) in the CoreValve/EvolutR group. At 5 years, the cumulative event rate for all-cause mortality was 50.9% in the Lotus valve group vs 52.8% in the CoreValve/EvolutR group (P = .59). Disabling stroke was less frequent with the Lotus valve vs CoreValve/EvolutR (cumulative event rates, 8.3% vs 12.2%; P = .04), whereas the cumulative event rates for overall stroke were similar in both groups (14.1% vs 15.3%; P = .38). Insertion of a new permanent pacemaker (38.9% vs 27.3%; P < .001) and detection of prosthetic aortic valve thrombosis (5.8% vs 1.8%; P = .007) were more common in the Lotus valve group than in the CoreValve/EvolutR group. A smaller proportion of patients who received the Lotus valve experienced valve malpositioning (0% vs 2.6%; P < .001) and required the use of a second valve (1.0% vs 3.8%; P < .001) during the procedure compared with those who received the CoreValve/EvolutR. Compared with the Lotus valve group, the CoreValve/EvolutR group had a significantly lower mean (SD) aortic gradient (7.8 [4.2] mm Hg vs 12.6 [6.7] mm Hg; P < .001) and larger valve areas (1.57 [0.56] cm2 vs 1.42 [0.42] cm2; P = .10). After 5 years, the proportion of patients with moderate or greater paravalvular leak was not significantly higher with the CoreValve/EvolutR than with the Lotus valve (1.9% vs 0%; P = .31); however, the proportion of patients with mild paravalvular leak was higher in the CoreValve/EvolutR group compared with the Lotus valve group (23.1% vs 7.8%; P = .006). Long-term, similar improvements in New York Heart Association class and Kansas City Cardiomyopathy Questionnaire score were observed in both groups. Conclusions and Relevance: The REPRISE III trial found that, at 5 years, the clinical outcomes of the Lotus valve were comparable to those of the CoreValve/EvolutR and that the Lotus valve was safe and effective. Trial Registration: ClinicalTrials.gov Identifier: NCT02202434.

A discrepancy between CT angiography and transesophageal echocardiographic measurements of the annular size affect long-term survival following trans-catheter aortic valve replacement.

Introduction: Accurate measurement of the aortic valve annulus is critical for proper valve sizing for the transcatheter aortic valve replacement (TAVR) procedure. While computed tomography angiography (CTA) is the widely-accepted standard, two-dimensional (2D) and three-dimensional(3D) transesophageal echocardiography (TEE) is commonly performed to measure the size of the aortic valve and to verify appropriate seating of prostheses. Methods: Patients undergoing TAVR between 2013-2015 were examined. 2D- and 3D-TEEmeasurements were compared to CTA taken as standard. Patients were followed for at least one year. The presence and effect of discrepancy (defined as a difference of more than 10%) between CTA and TEE measurements on survival were examined. Results: One hundred eighty-five patients (70 men) were included. 2D- and 3D-TEE measurements underestimated the annulus size by -1.49 and -1.32 mm, respectively. Discrepancies > 10% between TEE and CTA methods in estimating the aortic annulus size were associated with a decrease in post implant survival. The peak pressure gradient across the aortic prosthesis measured one year after the implant was higher in patients with an initial discrepancy between 3D-TEE and CTA measurements. In a multivariate cox-regression model, the discrepancy between CTA and 2D-TEE readings and the smaller size of the aortic annular area were the predictors of long-term survival. Conclusion: Both 2D and 3D-TEE underestimate the aortic annulus measurements compared to CTA, with 2D-TEE being relatively more precise than 3D-TEE technology. The presence of a discrepancy between echocardiographic and CTA measurements of the aortic annulus is associated with a lower survival rate.

Complete flow control using transient concurrent rapid ventricular pacing or intravenous adenosine and afferent arterial balloon occlusion during transvenous embolization of cerebral arteriovenous malformations: case series.

BACKGROUND: There are no reports that describe complete flow control using concurrent transient rapid ventricular pacing or intravenous (IV) adenosine and afferent arterial balloon flow arrest to aid transvenous embolization of cerebral arteriovenous malformations (AVM). We describe our experience with the use of this technique in patients undergoing transvenous AVM embolization. METHODS: Consecutive patients in whom transvenous embolization was attempted at our institute between January 2017 and July 2019 were included. Anatomical AVM features, number of embolization stages, technique of concurrent transient rapid ventricular pacing and afferent arterial balloon flow arrest, complications, and clinical and radiological outcomes were recorded and tabulated. RESULTS: Transvenous AVM embolization was attempted in 12 patients but abandoned in two patients for technical reasons. Complete embolization was achieved in 10 patients, five of whom had infratentorial AVMs. All 10 had a single primary draining vein. Rapid ventricular pacing was used in nine cases; IV adenosine injection was used in one case to achieve cardiac standstill. Complete AVM nidus obliteration was achieved with excellent neurologic outcome in nine cases, with transvenous embolization alone in two cases, and with staged transarterial followed by transvenous embolization in the others. Two patients developed hemorrhagic complications intraprocedurally. One patient was managed conservatively and the other operatively with AVM excision and hematoma evacuation; both made an excellent recovery without any neurologic deficits at 3 months. CONCLUSION: Complete flow control using concurrent transient rapid ventricular pacing with afferent arterial balloon flow arrest technique is safe and feasible for transvenous embolization of select AVMs.

Pacemaker Implantation and Dependency After Transcatheter Aortic Valve Replacement in the REPRISE III Trial.

Background As transcatheter aortic valve replacement expands to younger and/or lower risk patients, the long-term consequences of permanent pacemaker implantation are a concern. Pacemaker dependency and impact have not been methodically assessed in transcatheter aortic valve replacement trials. We report the incidence and predictors of pacemaker implantation and pacemaker dependency after transcatheter aortic valve replacement with the Lotus valve. Methods and Results A total of 912 patients with high/extreme surgical risk and symptomatic aortic stenosis were randomized 2:1 (Lotus:CoreValve) in REPRISE III (The Repositionable Percutaneous Replacement of Stenotic Aortic Valve through Implantation of Lotus Valve System-Randomized Clinical Evaluation) trial. Systematic assessment of pacemaker dependency was pre-specified in the trial design. Pacemaker implantation within 30 days was more frequent with Lotus than CoreValve. By multivariable analysis, predictors of pacemaker implantation included baseline right bundle branch block and depth of implantation; diabetes mellitus was also a predictor with Lotus. No association between new pacemaker implantation and clinical outcomes was found. Pacemaker dependency was dynamic (30 days: 43%; 1 year: 50%) and not consistent for individual patients over time. Predictors of pacemaker dependency at 30 days included baseline right bundle branch block, female sex, and depth of implantation. No differences in mortality or stroke were found between patients who were pacemaker dependent or not at 30 days. Rehospitalization was higher in patients who were not pacemaker dependent versus patients without a pacemaker or those who were dependent. Conclusions Pacemaker implantation was not associated with adverse clinical outcomes. Most patients with a new pacemaker at 30 days were not dependent at 1 year. Mortality and stroke were similar between patients with or without pacemaker dependency and patients without a pacemaker. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier NCT02202434.

Two-Year Outcomes After Transcatheter Aortic Valve Replacement With Mechanical vs Self-expanding Valves: The REPRISE III Randomized Clinical Trial.

Importance: To our knowledge, REPRISE III is the first large randomized comparison of 2 different transcatheter aortic valve replacement platforms: the mechanically expanded Lotus valve (Boston Scientific) and self-expanding CoreValve (Medtronic). Objective: To evaluate outcomes of Lotus vs CoreValve after 2 years. Design, Setting, and Participants: A total of 912 patients with high/extreme risk and severe, symptomatic aortic stenosis enrolled between September 22, 2014, and December 24, 2015, were randomized 2:1 to receive Lotus (607 [66.6%]) or CoreValve (305 [33.4%] at 55 centers in North America, Europe, and Australia. The first 2-year visit occurred on October 17, 2016, and the last was conducted on April 12, 2018. Clinical and echocardiographic assessments are complete through 2 years and will continue annually through 5 years. Main Outcomes and Measures: All-cause mortality and all-cause mortality or disabling stroke at 2 years. Other clinical factors included overall stroke, disabling stroke, repeated procedures, rehospitalization, valve thrombosis, and pacemaker implantation. Echocardiographic analyses included effective orifice area, mean gradient, and paravalvular leaks (PVLs). Results: Of 912 participants, the mean (SD) age was 82.8 (7.3) years, 465 (51%) were women, and the mean (SD) Society of Thoracic Surgeons predicted risk of mortality was 6.8% (4.0%). At 2 years, all-cause death was 21.3% with Lotus vs 22.5% with CoreValve (hazard ratio [HR], 0.94; 95% CI, 0.69-1.26; P = .67) and all-cause mortality or disabling stroke was 22.8% with Lotus and 27.0% with CoreValve (HR, 0.81; 95% CI, 0.61-1.07; P = .14). Overall stroke was 8.4% vs 11.4% (HR, 0.75; 95% CI, 0.48-1.17; P = .21); disabling stroke was more frequent with CoreValve vs Lotus (4.7% Lotus vs 8.6% CoreValve; HR, 0.53; 95% CI, 0.31-0.93; P = .02). More Lotus patients received a new permanent pacemaker (41.7% vs 26.1%; HR, 1.87; 95% CI, 1.41-2.49; P < .01) or had a valve thrombosis (3.0% vs 0.0%; P < .01) compared with CoreValve. More patients who received CoreValve experienced a repeated procedure (0.6% Lotus vs 2.9% CoreValve; HR, 0.19; 95% CI, 0.05-0.70; P < .01), valve migration (0.0% vs 0.7%; P = .05), or embolization (0.0% vs 2.0%; P < .01) than Lotus. Valve areas remained significantly larger and the mean gradient was lower with CoreValve than Lotus (valve area, mean [SD]: Lotus, 1.53 [0.49] cm2 vs CoreValve, 1.76 [0.51] cm2; P < .01; valve gradient, mean [SD]: Lotus, 13.0 [6.7] mm Hg vs 8.1 [3.7] mm Hg; P < .01). Moderate or greater PVL was more frequent with CoreValve (0.3% Lotus vs 3.8% CoreValve; P < .01) at 2 years. Larger improvements in New York Heart Association (NYHA) functional class were observed with Lotus compared with CoreValve (improved by ≥1 NYHA class: Lotus, 338 of 402 [84.1%] vs CoreValve, 143 of 189 [75.7%]; P = .01; improved by ≥2 NYHA classes: 122 of 402 [37.3%] vs 65 of 305 [21.3%]). Conclusions and Relevance: After 2 years, all-cause mortality rates, mortality or disabling stroke were similar between Lotus and CoreValve. Disabling stroke, functional class, valve migration, and PVL favored the Lotus arm whereas valve hemodynamics, thrombosis, and new pacemaker implantation favored the CoreValve arm. Trial Registration: clinicaltrials.gov Identifier: NCT02202434.

Unloading the Left Ventricle Before Reperfusion in Patients With Anterior ST-Segment-Elevation Myocardial Infarction.

BACKGROUND: In ST-segment-elevation myocardial infarction (STEMI), infarct size correlates directly with heart failure and mortality. Preclinical testing has shown that, in comparison with reperfusion alone, mechanically unloading the left ventricle (LV) before reperfusion reduces infarct size and that 30 minutes of unloading activates a cardioprotective program that limits reperfusion injury. The DTU-STEMI pilot trial (Door-To-Unload in STEMI Pilot Trial) represents the first exploratory study testing whether LV unloading and delayed reperfusion in patients with STEMI without cardiogenic shock is safe and feasible. METHODS: In a multicenter, prospective, randomized exploratory safety and feasibility trial, we assigned 50 patients with anterior STEMI to LV unloading by using the Impella CP followed by immediate reperfusion (U-IR) versus delayed reperfusion after 30 minutes of unloading (U-DR). The primary safety outcome was a composite of major adverse cardiovascular and cerebrovascular events at 30 days. Efficacy parameters included the assessment of infarct size by using cardiac magnetic resonance imaging. RESULTS: All patients completed the U-IR (n=25) or U-DR (n=25) protocols with respective mean door-to-balloon times of 72 versus 97 minutes. Major adverse cardiovascular and cerebrovascular event rates were not statistically different between the U-IR versus U-DR groups (8% versus 12%, respectively, P=0.99). In comparison with the U-IR group, delaying reperfusion in the U-DR group did not affect 30-day mean infarct size measured as a percentage of LV mass (15±12% versus 13±11%, U-IR versus U-DR, P=0.53). CONCLUSIONS: We report that LV unloading using the Impella CP device with a 30-minute delay before reperfusion is feasible within a relatively short time period in anterior STEMI. The DTU-STEMI pilot trial did not identify prohibitive safety signals that would preclude proceeding to a larger pivotal study of LV unloading before reperfusion. An appropriately powered pivotal trial comparing LV unloading before reperfusion to the current standard of care is required. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT03000270.

Effect of Mechanically Expanded vs Self-Expanding Transcatheter Aortic Valve Replacement on Mortality and Major Adverse Clinical Events in High-Risk Patients With Aortic Stenosis: The REPRISE III Randomized Clinical Trial.

Importance: Transcatheter aortic valve replacement (TAVR) is established for selected patients with severe aortic stenosis. However, limitations such as suboptimal deployment, conduction disturbances, and paravalvular leak occur. Objective: To evaluate if a mechanically expanded valve (MEV) is noninferior to an approved self-expanding valve (SEV) in high-risk patients with aortic stenosis undergoing TAVR. Design, Setting, and Participants: The REPRISE III trial was conducted in 912 patients with high or extreme risk and severe, symptomatic aortic stenosis at 55 centers in North America, Europe, and Australia between September 22, 2014, and December 24, 2015, with final follow-up on March 8, 2017. Interventions: Participants were randomized in a 2:1 ratio to receive either an MEV (n = 607) or an SEV (n = 305). Main Outcomes and Measures: The primary safety end point was the 30-day composite of all-cause mortality, stroke, life-threatening or major bleeding, stage 2/3 acute kidney injury, and major vascular complications tested for noninferiority (margin, 10.5%). The primary effectiveness end point was the 1-year composite of all-cause mortality, disabling stroke, and moderate or greater paravalvular leak tested for noninferiority (margin, 9.5%). If noninferiority criteria were met, the secondary end point of 1-year moderate or greater paravalvular leak was tested for superiority in the full analysis data set. Results: Among 912 randomized patients (mean age, 82.8 [SD, 7.3] years; 463 [51%] women; predicted risk of mortality, 6.8%), 874 (96%) were evaluable at 1 year. The primary safety composite end point at 30 days occurred in 20.3% of MEV patients and 17.2% of SEV patients (difference, 3.1%; Farrington-Manning 97.5% CI, -∞ to 8.3%; P = .003 for noninferiority). At 1 year, the primary effectiveness composite end point occurred in 15.4% with the MEV and 25.5% with the SEV (difference, -10.1%; Farrington-Manning 97.5% CI, -∞ to -4.4%; P<.001 for noninferiority). The 1-year rates of moderate or severe paravalvular leak were 0.9% for the MEV and 6.8% for the SEV (difference, -6.1%; 95% CI, -9.6% to -2.6%; P < .001). The superiority analysis for primary effectiveness was statistically significant (difference, -10.2%; 95% CI, -16.3% to -4.0%; P < .001). The MEV had higher rates of new pacemaker implants (35.5% vs 19.6%; P < .001) and valve thrombosis (1.5% vs 0%) but lower rates of repeat procedures (0.2% vs 2.0%), valve-in-valve deployments (0% vs 3.7%), and valve malpositioning (0% vs 2.7%). Conclusions and Relevance: Among high-risk patients with aortic stenosis, use of the MEV compared with the SEV did not result in inferior outcomes for the primary safety end point or the primary effectiveness end point. These findings suggest that the MEV may be a useful addition for TAVR in high-risk patients. Trial Registration: ClinicalTrials.gov Identifier: NCT02202434.

Assessment of a nuclear affinity labeling method for tracking implanted mesenchymal stem cells.

Therapeutic implantation of mesenchymal stem cells (MSCs) is entering the realm of clinical trials for several human diseases, and yet much remains uncertain regarding their dynamic distribution and cell fate after in vivo application. Discrepancies in the literature can be attributed in part to the use of different cell labeling/tracking methods and cell administration protocols. To identify a stem cell detection method suitable for myocardial implantation in a large animal model, we experimented on three different MSC labeling methods: adenovirus-mediated expression of enhanced green fluorescence protein (EGFP) and beta-galactosidase (LacZ), and nuclear staining with DAPI. Intramuscular and intracoronary administrations of labeled porcine MSCs identified the nuclear affinity dye to be a reliable stem cell tracking marker. Stem cell identification is facilitated by an optimized live cell labeling condition generating bright blue fluorescence sharply confined to the nucleus. DAPI-labeled MSCs retained full viability, ceased proliferation, and exhibited an increased differentiation potential. The labeled MSCs remained fully active in expressing key growth factor and cytokine genes, and notably exhibited enhanced expression of the chemokine receptor CXCR4 and its ligand SDF1, indicating their competency in response to tissue injury. Histological analysis revealed that approximately half a million MSCs or approximately 2% of the administered MSCs remained localized in the normal pig heart 2 weeks after coronary infusion. That the vast majority of these identified MSCs were interstitial indicated the ability of MSCs to migrate across the coronary endothelium. No evidence was obtained indicating MSC differentiation to cardiomyocyte.

Regional desensitization of beta-adrenergic receptor signaling in swine with chronic hibernating myocardium.

Contractile reserve during submaximal beta-adrenergic stimulation is attenuated in patients and swine with hibernating myocardium. We tested the hypothesis that this arises as a regional adaptive response in beta-adrenergic adenylyl cyclase coupling. Pigs (n=8) were studied 3 months after instrumentation with a left anterior descending artery (LAD) stenosis when flow (LAD, 0.7+/-0.2 versus 1.2+/-0.1 mL/min per gram in normal remote; P<0.05) and wall thickening (LAD, 15.5 [corrected]+/-3.2% versus 40.0+/-5.5% in remote; P<0.05) were reduced in the absence of infarction. Whereas basal cAMP production was normal (LAD, 87+/-18 versus 91+/-19 pmol/mg per minute; P=NS), responses to isoproterenol were blunted (LAD, 83+/-6 versus 146+/-25 pmol/mg per minute in remote; P<0.05). beta-receptor density and subtype were unchanged, but there was a reduction in the number of high-affinity binding sites (LAD, 40+/-4% versus 53+/-7% in normal remote; P<0.05). The Gialpha2/Gsalpha ratio increased (LAD, 1.8+/-0.3 versus 0.99+/-0.3 in remote myocardium; P<0.05), although GppNHp-stimulated cAMP production was equivocally reduced. Forskolin responses were unchanged and similar to shams. These data indicate regional attenuation of beta-receptor adenylyl cyclase signaling in hibernating myocardium. This blunts the local contractile response to beta-adrenergic stimulation and may serve to protect against a myocardial supply/demand imbalance when external determinants of myocardial workload increase during sympathetic activation.