2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy" provides recommendations to guide clinicians in the management of patients with hypertrophic cardiomyopathy.

METHODS

A comprehensive literature search was conducted from September 14, 2022, to November 22, 2022, encompassing studies, reviews, and other evidence on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through May 23, 2023, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Hypertrophic cardiomyopathy remains a common genetic heart disease reported in populations globally. Recommendations from the "2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy" have been updated with new evidence to guide clinicians.

A Randomized Comparison of Radial Artery Intimal Hyperplasia Following Distal Versus Proximal Transradial Access for Coronary Angiography: PRESERVE RADIAL

BACKGROUND

Distal transradial access (dTRA) is an alternative to conventional forearm transradial access (fTRA) for coronary angiography (CAG). Differences in healing of the radial artery (RA) in the forearm have not been evaluated between these 2 access strategies. We sought to compare the mean difference in forearm RA intimal-medial thickening (IMT) in patients randomized to dTRA versus fTRA.

METHODS AND RESULTS

In this single-center randomized clinical trial, 64 patients undergoing nonemergent CAG were randomized (1:1) to dTRA versus fTRA. Ultra-high-resolution (55-MHz) vascular ultrasound of the forearm and distal RA was performed pre-CAG and at 90 days. The primary end point was the mean change in forearm RA IMT. Secondary end points included procedural characteristics, vascular injury, RA occlusion, and ipsilateral hand pain and function. Baseline demographics and clinical characteristics, mean forearm RA IMT, and procedural specifics were similar between the dTRA and fTRA cohorts. There was no difference in mean change in forearm RA IMT between the 2 cohorts (0.07 versus 0.07 mm; P=0.37). No RA occlusions or signs of major vascular injury were observed at 90 days. Ipsilateral hand pain and function (Borg pain scale score: 12 versus 11; P=0.24; Disabilities of the Arm, Shoulders, and Hand scale score: 6 versus 8; P=0.46) were comparable.

CONCLUSIONS

Following CAG, dTRA was associated with no differences in mean change of forearm RA IMT, hand pain, and function versus fTRA for CAG. Further investigation is warranted to elucidate mechanisms and predictors of RA healing and identify effective strategies to preserving RA integrity for repeated procedures.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04801901.

Sex-Related Differences in Patient Characteristics, Hemodynamics, and Outcomes of Cardiogenic Shock: INOVA-SHOCK Registry

Background

Little is known about sex-related differences in outcomes of patients with cardiogenic shock (CS) treated within a standardized team-based approach (STBA).

Methods

We evaluated 520 consecutive patients (151 women and 369 men) with CS due to acute myocardial infarction (AMI) and heart failure (HF) in a single-center registry (January 2017-December 2019) and examined outcomes according to sex and CS phenotype. The primary outcome was in-hospital mortality. Secondary outcomes included major adverse cardiac events, 30-day mortality, major bleeding, vascular complications, and stroke.

Results

Women with AMI-CS had higher baseline acuity (CardShock score: female [F]: 5.5 vs male [M]: 4.0; P = .04). Women with HF-CS more often presented with cardiac arrest (F: 12.4% vs M: 2.4%; P< .01) and had higher rates of vasopressor use (F: 70.8% vs M: 58.0%; P = .04) and mechanical circulatory support (F: 46.1% vs M: 32.5%; P = .04). There were no sex-related differences in in-hospital mortality for AMI-CS (F: 45.2% vs M: 36.9%; P = .28) and HF-CS (F: 28.1% vs M: 24.5%; P = .56). Women with HF-CS experienced higher rates of major bleeding (F: 25.8% vs M: 13.7%; P = .02) and vascular complications (F: 15.7% vs M: 6.1%; P = .01). However, female sex was not an independent predictor of these complications. No sex differences in survival were noted at 1 year.

Conclusions

Within an STBA, although women with AMI-CS and HF-CS presented with higher acuity, they experienced similar in-hospital mortality, major adverse cardiac events, 30-day mortality, stroke, and 30-day readmissions as men. Further research is needed to better understand the extent to which historical differences in CS outcomes can be mitigated by an STBA.

A Randomized Comparison of Radial Artery Intimal Hyperplasia Following Distal vs. Proximal Transradial Access for Coronary Angiography: PRESERVE RADIAL Trial

Background

Distal transradial access (dTRA) is an alternative to conventional forearm transradial access (fTRA) for coronary angiography (CAG). Differences in healing of the radial artery in the forearm (FRA) have not been evaluated between these 2 access strategies. We sought to compare FRA intimal-medial thickening (IMT) in patients randomized to dTRA vs. fTRA for CAG.

Methods and Results

Sixty-four consecutive patients undergoing non-emergent CAG were randomized (1:1) to dTRA vs. fTRA. Ultrahigh resolution (55 MHz) vascular ultrasound) of the FRA and distal RA was performed pre-CAG and at 90 days. Primary endpoint was 90-day FRA IMT. Secondary endpoints included procedural characteristics, vascular injury, RA occlusion and ipsilateral hand pain and function. Baseline demographics and clinical characteristics, mean FRA IMT, time to RA access, procedure time, and radiation exposure were similar between the dTRA and fTRA cohorts. There were no between group differences in 90-day FRA IMT (0.37 mm vs 0.38 mm, respectively; p =0.73). No RA occlusions or signs of major vascular injury were observed at 90 days. Ipsilateral hand pain and function (Borg pain scale:12 vs 11, p =0.24; DASH scores: 6 vs 8, p =0.46) were comparable.

Conclusions

In this single center randomized clinical trial, similar patterns of FRA vascular healing at 90 days, procedural results as well as hand pain and function were observed following dTRA vs. fTRA for CAG. Further investigation is warranted to better understand the mechanistics and predictors of RA healing and to identify strategies aimed at preserving RA integrity for future procedures.

What is New?

DTRA has been proposed as an alternative to traditional fTRA in the wrist for CAG and PCI because of ergonomic and post-procedural recovery benefits to the patient, as well as potential reductions in occlusion of the FRA.There are gaps in knowledge, however, regarding potential differences in remodeling of the FRA in patients undergoing dTRA versus fTRA.In this randomized clinical trial, there were no differences in IMT and patterns of vascular injury and healing, using ultrahigh resolution (55 MHz) ultrasound, at 90 days in patients randomized to dTRA or FTRA for elective and non-emergent CAG and PCI.

What Are the Clinical Implications

Our findings highlight the need for further inquiry through large multicenter randomized clinical trials to better the understand the mechanistics and predictors of IMT and to identify strategies to mitigate the adverse effects of vessel remodeling in patients undergoing TRA across the entire severity spectrum of cardiovascular disease.

A Standardized and Regionalized Network of Care for Cardiogenic Shock

BACKGROUND

The benefits of standardized care for cardiogenic shock (CS) across regional care networks are poorly understood.

OBJECTIVES

The authors compared the management and outcomes of CS patients initially presenting to hub versus spoke hospitals within a regional care network.

METHODS

The authors stratified consecutive patients enrolled in their CS registry (January 2017 to December 2019) by presentation to a spoke versus the hub hospital. The primary endpoint was 30-day mortality. Secondary endpoints included bleeding, stroke, or major adverse cardiovascular and cerebrovascular events.

RESULTS

Of 520 CS patients, 286 (55%) initially presented to 34 spoke hospitals. No difference in mean age (62 years vs 61 years; P = 0.38), sex (25% vs 32% women; P = 0.10), and race (54% vs 52% white; P = 0.82) between spoke and hub patients was noted. Spoke patients more often presented with acute myocardial infarction (50% vs 32%; P < 0.01), received vasopressors (74% vs 66%; P = 0.04), and intra-aortic balloon pumps (88% vs 37%; P < 0.01). Hub patients were more often supported with percutaneous ventricular assist devices (44% vs 11%; P < 0.01) and veno-arterial extracorporeal membrane oxygenation (13% vs 0%; P < 0.01). Initial presentation to a spoke was not associated with increased risk-adjusted 30-day mortality (adjusted OR: 0.87 [95% CI: 0.49-1.55]; P = 0.64), bleeding (adjusted OR: 0.89 [95% CI: 0.49-1.62]; P = 0.70), stroke (adjusted OR: 0.74 [95% CI: 0.31-1.75]; P = 0.49), or major adverse cardiovascular and cerebrovascular events (adjusted OR 0.83 [95% CI: 0.50-1.35]; P = 0.44).

CONCLUSIONS

Spoke and hub patients experienced similar short-term outcomes within a regionalized CS network. The optimal strategy to promote standardized care and improved outcomes across regional CS networks merits further investigation.

Cardiogenic Shock From Heart Failure Versus Acute Myocardial Infarction: Clinical Characteristics, Hospital Course, and 1-Year Outcomes

BACKGROUND

Little is known about clinical characteristics, hospital course, and longitudinal outcomes of patients with cardiogenic shock (CS) related to heart failure (HF-CS) compared to acute myocardial infarction (AMI; CS related to AMI [AMI-CS]).

METHODS

We examined in-hospital and 1-year outcomes of 520 (219 AMI-CS, 301 HF-CS) consecutive patients with CS (January 3, 2017-December 31, 2019) in a single-center registry.

RESULTS

Mean age was 61.5±13.5 years, 71% were male, 22% were Black patients, and 63% had chronic kidney disease. The HF-CS cohort was younger (58.5 versus 65.6 years, P<0.001), had fewer cardiac arrests (15.9% versus 35.2%, P<0.001), less vasopressor utilization (61.8% versus 82.2%, P<0.001), higher pulmonary artery pulsatility index (2.14 versus 1.51, P<0.01), lower cardiac power output (0.64 versus 0.77 W, P<0.01) and higher pulmonary capillary wedge pressure (25.4 versus 22.2 mm Hg, P<0.001) than patients with AMI-CS. Patients with HF-CS received less temporary mechanical circulatory support (34.9% versus 76.3% P<0.001) and experienced lower rates of major bleeding (17.3% versus 26.0%, P=0.02) and in-hospital mortality (23.9% versus 39.3%, P<0.001). Postdischarge, 133 AMI-CS and 229 patients with HF-CS experienced similar rates of 30-day readmission (19.5% versus 24.5%, P=0.30) and major adverse cardiac and cerebrovascular events (23.3% versus 28.8%, P=0.45). Patients with HF-CS had lower 1-year mortality (n=123, 42.6%) compared to the patients with AMI-CS (n=110, 52.9%, P=0.03). Cumulative 1-year mortality was also lower in patients with HF-CS (log-rank test, P=0.04).

CONCLUSIONS

Patients with HF-CS were younger, and despite lower cardiac power output and higher pulmonary capillary wedge pressure, less likely to receive vasopressors or temporary mechanical circulatory support. Although patients with HF-CS had lower in-hospital and 1-year mortality, both cohorts experienced similarly high rates of postdischarge major adverse cardiovascular and cerebrovascular events and 30-day readmission, highlighting that both cohorts warrant careful long-term follow-up.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03378739.

Socioeconomic Determinants of Health and Cardiovascular Outcomes in Women: JACC Review Topic of the Week

Socioeconomic disparities in cardiovascular risk factors and outcomes exist among women, particularly those of minority racial or ethnic backgrounds. Barriers to optimal cardiovascular health begin early in life-with inadequate access to effective contraception, postpartum follow-up, and maternity leave-and result in excess rates of myocardial infarction, stroke, and cardiovascular death in at-risk populations. Contributing factors include reduced access to care, low levels of income and social support, and lack of diversity among cardiology clinicians and within clinical trials. These barriers can be mitigated by optimizing care access via policy change and improving physical access to care in women with geographic or transportation limitations. Addressing structural racism through policy change and bolstering structured community support systems will be key to reducing adverse cardiovascular outcomes among women of racial and ethnic minorities. Diversification of the cardiology workforce to more closely represent the patients we serve will be beneficial to all women.

Transradial access in acute myocardial infarction complicated by cardiogenic shock: Stratified analysis by shock severity

BACKGROUND

Transradial access (TRA) is associated with improved survival and reduced vascular complications in acute myocardial infarction (AMI). Limited data exist regarding TRA utilization and outcomes for AMI complicated by cardiogenic shock (CS). We sought to assess the safety, feasibility, and clinical outcomes of TRA in AMI-CS.

METHODS

One-hundred and fifty-three patients with AMI-CS were stratified into tertiles of disease severity using the CardShock score. The primary endpoint was successful percutaneous coronary intervention (PCI), defined as Thrombolysis in Myocardial Infarction III flow with survival to 30 days.

RESULTS

Mean age was 66 years, 72% were men, and 47% had diabetes. TRA was the preferred access site in patients with low and intermediate disease severity. Overall, 50 (32%) patients experienced major adverse cardiac and cerebrovascular events; most events (78%) occurred in patients undergoing transfemoral access (TFA) in the intermediate-high tertiles of CS severity. Of the 41 (27%) total bleeding events, 32% occurred at the coronary angiography access site, of which 92% were in the TFA group. The use of ultrasound (US) guidance for TFA resulted in reduced coronary access-site bleeding (8.5 vs. 33.0%, p = .01). In a hierarchical logistic regression model, utilizing TRA did not result in lower odds of successful PCI (Odds ratio [OR]: 1.36; 95% confidence interval [CI]: 0.54-3.40).

CONCLUSION

This study suggests that TRA is feasible across the entire spectrum of AMI-CS and is associated with reduced coronary access-site bleeding. In addition, US-guided TFA is associated with reductions in access-site bleeding and vascular complications. Concerted efforts should be made to incorporate vascular access protocols into existing CS algorithms in dedicated shock care centers.

Does study subject diversity influence cardiology research site performance?: Insights from 2 U.S. National Coronary Stent Registries

BACKGROUND

Minorities and women are underrepresented in cardiovascular research. Whether their higher enrollment can be predicted or influences research site performance is unclear.

METHODS

We evaluated 104 sites that enrolled 4,184 patients in the U.S. Platinum Diversity (PD) and Promus Element Plus (PE Plus) studies (2012 to 2016). Research sites were ranked from lowest to highest minority and female enrollment, respectively. United States Census Bureau division and core-based statistical area (CBSA) populations were determined for each site and the following study performance metrics compared across quartiles of minority and female enrollment, respectively: (1) study subject enrollment rate (SER), (2) time to first patient enrolled, (3) rate of follow-up visits not done, (4) rate of follow-up visits out of window, and (5) protocol deviation rate (PDR). Multivariable regression was used to predict SER and PDR.

RESULTS

Minority enrollment varied by region (P = .025) and population (P = .024) with highest recruitment noted in the Pacific, West South Central, South Atlantic, Mid-Atlantic and East North Central divisions. Female enrollment bore no relationship to region (P = .67) or population (P = .40). Median SER was similar in sites withi the highest vs lowest quartile of minority enrollment (SER of 4 vs 5 patients per month, respectively, P =0.78) and highest vs. lowest female enrollment (SER of 4 vs 4, respectively, P = .21). Median PDR was lower in sites within the highest vs lowest minority enrollment (0.23 vs 0.50 PDs per patient per month, respectively, P = .01) and highest vs. lowest female enrollment (0.28 vs. 0.37 PDs per patient per month, respectively, P = .04). However, this relationship did not persist after multivariable adjustment. All other site performance metrics were comparable across quartiles of minority and female enrollment.

CONCLUSIONS

Minority, but not female enrollment, correlated with research site geographic region and surrounding population. High enrollment of minorities and women did not influence study performance metrics. These findings help inform future strategies aimed at increasing clinical trial diversity.

TRIAL REGISTRATION

The PD and PE Plus studies are registered at www.clinicaltrials.gov under identifiers NCT02240810 and NCT01589978, respectively.

KEY POINTS

Question: Does the enrollment of more Blacks, Hispanics and women in US cardiovascular research studies influence the overall rate of study subject enrollment and/or other key study site performance metrics and can diverse enrollment be predicted?

FINDINGS

In this pooled analysis of 104 sites that enrolled 4,184 patients in the Platinum Diversity and Promus Element Plus Post-Approval Studies, we found that the enrollment of higher proportions of underrepresented minorities and women was univariately associated with lower protocol deviation rates while having no effect on other site performance metrics. A site's geographic location and surrounding population predicted minority, but not female enrollment. Meaning: These findings suggest that cardiovascular research subject diversity may be predicted from site characteristics and enhanced without compromising key study performance metrics. These insights help inform future strategies aimed at improving clinical trial diversity.

Spontaneous Coronary Artery Dissection in Females With the Fragile X FMR1 Premutation

This paper reports 2 cases of female carriers of the FMR1 premutation for developing spontaneous coronary artery dissection (SCAD). These women had classical presentations of premutation symptoms, including anxiety, depression, and connective tissue problems, all of which can contribute to SCAD. These cases suggest a possible connection between the fragile X premutation and a predisposition to SCAD.

Sex Differences in Outcomes Following Percutaneous Coronary Intervention According to Age

BACKGROUND

Women <50 years of age with coronary artery disease may represent a group at higher risk for recurrent ischemic events after percutaneous coronary intervention (PCI); however, no long-term, multicenter outcomes assessment exists in this population.

METHODS AND RESULTS

Using the National Heart, Lung, and Blood Institute Dynamic Registry, we evaluated the association of sex and age on cardiovascular-related outcomes in 10,963 patients (3797 women, 394 <50 years) undergoing PCI and followed for 5 years. Death, myocardial infarction, coronary artery bypass graft surgery, and repeat PCI were primary outcomes comprising major adverse cardiovascular events. Although procedural success rates were similar by sex, the cumulative rate of major adverse cardiovascular events at 1 year was higher in young women (27.8 versus 19.9%; P=0.003), driven largely by higher rates of repeat revascularizations for target vessel or target lesion failure (coronary artery bypass graft surgery: 8.9% versus 3.9%, P<0.001, adjusted hazard ratio 2.4, 95% confidence interval 1.5-4.0; PCI: 19.0% versus 13.0%, P=0.005, adjusted hazard ratio 1.6, 95% confidence interval 1.2-2.2). At 5 years, young women remained at higher risk for repeat procedures (coronary artery bypass graft surgery: 10.7% versus 6.8%, P=0.04, adjusted hazard ratio 1.71, 95% confidence interval 1.01-2.88; repeat PCI [target vessel]: 19.7% versus 11.8%, P=0.002, adjusted hazard ratio 1.8, 95% confidence interval 1.24-2.82). Compared with older women, younger women remained at increased risk of major adverse cardiovascular events, whereas all outcome rates were similar in older women and men.

CONCLUSIONS

Young women, despite having less severe angiographic coronary artery disease, have an increased risk of target vessel and target lesion failure. The causes of this difference deserve further investigation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00005677.

Cardiac catheterization in patients with ascending aortic aneurysms: safety, success, and prevalence of coronary artery disease

BACKGROUND

Evaluation for coronary artery disease (CAD) is recommended prior to surgery for ascending aortic aneurysms. Concerns regarding the use of coronary angiography in this population include safety and the ability to successfully selectively engage the coronary arteries. Additionally, the prevalence of CAD is not well described.

METHODS

We retrospectively reviewed all patients referred for cardiac catheterization prior to elective surgery for an ascending aortic aneurysm at our institution over a 4-year period. Catheter selection was based on knowledge of the aneurysm size. Images were screened for whether selective coronary engagement was achieved and for the presence of significant coronary disease.

RESULTS

A total of 205 patients met the inclusion criteria. The mean age was 61 years and 63% were male. There were no adverse events related to catheterization. The left coronary artery was selectively engaged in 98% of patients, and the right coronary in 92%. On average, 3.1 catheters were used for angiography per patient. Coronary artery disease was present in 19% of patients (n = 39). Increasing age was the only risk factor significantly associated with the presence of disease. Coronary bypass was required in 15% of patients at the time of aortic aneurysm surgery.

CONCLUSIONS

Coronary angiography can be performed safely and the coronary arteries can be successfully selectively engaged in patients with ascending aortic aneurysms. The findings frequently impact the surgical approach. We believe that coronary angiography should be part of the routine preoperative evaluation in appropriate patients.

Five-year follow-up of patients treated for coronary artery disease in the face of an increasing burden of co-morbidity and disease complexity (from the NHLBI Dynamic Registry)

Management of coronary artery disease (CAD) has evolved over the past decade, but there are few prospective studies evaluating long-term outcomes in a real-world setting of evolving technical approaches and secondary prevention. The aim of this study was to determine how the mortality and morbidity of CAD has changed in patients who have undergone percutaneous coronary intervention (PCI), in the setting of co-morbidities and evolving management. The National Heart, Lung, and Blood Institute Dynamic Registry was a cohort study of patients undergoing PCI at various time points. Cohorts were enrolled in 1999 (cohort 2, n = 2,105), 2004 (cohort 4, n = 2,112), and 2006 (cohort 5, n = 2,176), and each was followed out to 5 years. Primary outcomes were death, myocardial infarction (MI), coronary artery bypass grafting, repeat PCI, and repeat revascularization. Secondary outcomes were PCI for new obstructive lesions at 5 years, 5-year rates of death and MI stratified by the severity of coronary artery and co-morbid disease. Over time, patients were more likely to have multiple co-morbidities and more severe CAD. Despite greater disease severity, there was no significant difference in death (16.5% vs 17.6%, adjusted hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.74 to 1.08), MI (11.0% vs 10.6%, adjusted HR 0.87, 95% CI 0.70 to 1.08), or repeat PCI (20.4% vs 22.2%, adjusted HR 0.98, 95% CI 0.85 to 1.17) at 5-year follow-up, but there was a significant decrease in coronary artery bypass grafting (9.1% vs 4.3%, adjusted HR 0.44, 95% CI 0.32 to 0.59). Patients with 5 co-morbidities had a 40% to 60% death rate at 5 years. There was a modestly high rate of repeat PCI for new lesions, indicating a potential failure of secondary prevention for this population in the face of increasing co-morbidity. Overall 5-year rates of death, MI, repeat PCI, and repeat PCI for new lesions did not change significantly in the context of increased co-morbidities and complex disease.

Lp-PLA₂- a novel risk factor for high-risk coronary and carotid artery disease

Lipoprotein-associated phospholipase A2 (Lp-PLA₂) is at the crossroads of lipid metabolism and the inflammatory response. It is produced by inflammatory cells, bound to LDL and other lipoproteins, and once in the arterial wall facilitates hydrolysis of phospholipids. Elevated serum levels of Lp-PLA₂ have been associated with increased cardiovascular risk in healthy populations and in patients with known vascular disease. Here, we review the role of Lp-PLA₂ in the development of atherosclerosis and progression to unstable disease, the utility of Lp-PLA₂ as a risk predictor for coronary and carotid events and the potential clinical benefit of pharmacologic inhibition of Lp-PLA₂.

Correlation of transthoracic echocardiography and right heart catheterization in pregnancy

OBJECTIVES

To correlate estimated pulmonary artery pressures (PAP) by echocardiography with right heart catheterization (RHC) measurements and to correlate estimated left ventricular ejection fraction (EF) by echocardiography with cardiac output (CO) measurements by RHC.

STUDY DESIGN

All women who had echocardiography at a single institution during a 6-year period and underwent RHC during pregnancy were included. Echocardiography estimates of right ventricular systolic pressure (RVSP) and EF were correlated with measured RHC PAP and CO, respectively.

RESULTS

Eighteen patients underwent 21 RHCs, 10 antepartum at the catheterization laboratory and the remaining 11 intrapartum, performed with the use of a pulmonary artery catheter placed prior to the onset or induction of labor. Correlation between RVSP and PAP was good (rho=0.79, P<0.0001); nonetheless, in 30% of cases RHC eliminated the concern for pulmonary hypertension (PHTN). There was minimal correlation between EF and CO.

CONCLUSION

Despite good statistical correlation between echocardiography and RHC for determining pulmonary artery pressure, RHC should be considered for major decisions such as pregnancy interruption or preterm delivery given the proportion of cases where concern for PHTN was excluded by RHC. EF provides a poor proxy for CO.