Four-dimensional Virtual Catheter: Noninvasive Assessment of Intra-aortic Hemodynamics in Bicuspid Aortic Valve Disease

Background Four-dimensional (4D) flow MRI enables the evaluation of blood flow alterations in patients with congenital bicuspid aortic valve (BAV). However, current analysis methods are cumbersome and lack the use of the volumetric data from 4D MRI. Purpose To investigate the feasibility and reproducibility of a technique that uses a catheter-like mathematical model (virtual catheter) to assess volumetric intra-aortic hemodynamics from 4D flow MRI in patients with BAV. Materials and Methods In this retrospective study, data were collected from adult patients with BAV and healthy participants who underwent aortic 4D flow MRI from November 2011 through August 2014. Reproducibility was tested in healthy study participants who underwent test-retest examinations within 2 weeks. Patients were grouped on the basis of the severity of aortic valve regurgitation (AVR) and aortic valve stenosis (AVS). A 4D virtual catheter mathematical model for probing intra-aortic hemodynamic flow was constructed as a tube with an automatically derived radius along the entire thoracic aorta centerline. Volumetric intra-aortic hemodynamics were computed from 4D flow MRI only within the virtual catheter, and the following volume-normalized systolic peaks were derived: kinetic energy (KE), viscous energy loss rate (VELR), and vorticity. Hemodynamic data were presented as medians with interquartile ranges and compared by using Mann-Whitney U test and Kruskal-Wallis test. Results The study included 91 participants (57 patients [mean age, 46 years ± 12], 18 women; 34 healthy participants [mean age: 44 years ± 14], 12 women; 15 healthy participants underwent test-retest examinations). Patients showed higher VELR values compared with healthy participants (median, 31 W/m³ [interquartile range, 21-72] vs 23 W/m³ [interquartile range, 17-30], respectively; P < .001) and vorticity (69 sec^-1 [interquartile range, 59-87] vs 60 sec^-1 [interquartile range, 50-67], respectively; P < .001). Four-dimensional virtual catheter showed differences among different AVS and AVR grades with the highest VELR (120 W/m³; interquartile range, 99-166; P < .001) and vorticity (108 sec^-1; interquartile range, 84-151; P < .001) found in severe AVS. High test-retest reproducibility was found for all virtual catheter-derived metrics (intraclass correlation, 0.80 ± 0.07; coefficient of variation, 9% ± 3). Conclusion The proposed four-dimensional (4D) virtual catheter technique enabled reproducible automated evaluation of volumetric intra-aortic hemodynamics alterations from 4D flow MRI in patients with bicuspid aortic valve. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Mitsouras and Hope in this issue.

Open Access Publishing and Subsequent Citations Among Articles in Major Cardiovascular Journals

BACKGROUND

While open access publishing among cardiovascular journals has increased in scope over the last decade, the relationship between open access and article citation volume remains unclear.

METHODS

We evaluated the association between open access publishing and citation number in 2017 among 4 major cardiovascular journals. Articles indexed to PubMed with ≥5 citations were identified among the following journals: Circulation, European Heart Journal, Journal of the American College of Cardiology, and JAMA Cardiology. Multivariable Poisson regression models were adjusted for journal and article type.

RESULTS

Of the 916 articles published in 2017, original investigations accounted for most articles (66.7%), followed by reviews (14.5%), guideline/scientific statements (8.4%), research letters (3.7%), viewpoints (3.7%), and editorials (2.9%). Among all articles, 43% (n = 391) were open access. Citation number was higher among open access articles compared with those with subscription access (14 [25^th-75^th percentile: 9-23] vs 11 [25^th-75^th percentile: 7-17]; P < .001). Open access status was significantly associated with higher number of citations after multivariable adjustment (β coefficient: +0.42; 95% confidence interval, 0.38-0.45, P < .001). Open access articles had consistently higher citations compared with subscription access articles across the 3 most frequent article types.

CONCLUSION

Among contemporary articles published in major cardiovascular journals, open access publishing accounted for over 40% of articles and was significantly associated with increased short-term citations. Further research is required to assess the variation in long-term citation rates based on open access publishing status.

Myocardial Viability and Long-Term Outcomes in Ischemic Cardiomyopathy

BACKGROUND

The role of assessment of myocardial viability in identifying patients with ischemic cardiomyopathy who might benefit from surgical revascularization remains controversial. Furthermore, although improvement in left ventricular function is one of the goals of revascularization, its relationship to subsequent outcomes is unclear.

METHODS

Among 601 patients who had coronary artery disease that was amenable to coronary-artery bypass grafting (CABG) and who had a left ventricular ejection fraction of 35% or lower, we prospectively assessed myocardial viability using single-photon-emission computed tomography, dobutamine echocardiography, or both. Patients were randomly assigned to undergo CABG and receive medical therapy or to receive medical therapy alone. Left ventricular ejection fraction was measured at baseline and after 4 months of follow-up in 318 patients. The primary end point was death from any cause. The median duration of follow-up was 10.4 years.

RESULTS

CABG plus medical therapy was associated with a lower incidence of death from any cause than medical therapy alone (182 deaths among 298 patients in the CABG group vs. 209 deaths among 303 patients in the medical-therapy group; adjusted hazard ratio, 0.73; 95% confidence interval, 0.60 to 0.90). However, no significant interaction was observed between the presence or absence of myocardial viability and the beneficial effect of CABG plus medical therapy over medical therapy alone (P = 0.34 for interaction). An increase in left ventricular ejection fraction was observed only among patients with myocardial viability, irrespective of treatment assignment. There was no association between changes in left ventricular ejection fraction and subsequent death.

CONCLUSIONS

The findings of this study do not support the concept that myocardial viability is associated with a long-term benefit of CABG in patients with ischemic cardiomyopathy. The presence of viable myocardium was associated with improvement in left ventricular systolic function, irrespective of treatment, but such improvement was not related to long-term survival. (Funded by the National Institutes of Health; STICH ClinicalTrials.gov number, NCT00023595.).

Prevalence and Prognosis of Unrecognized Myocardial Infarction in Asymptomatic Patients With Diabetes: A Two-Center Study With Up to 5 Years of Follow-up

OBJECTIVE

To determine the prevalence and prognostic significance of unrecognized myocardial infarction (MI) by delayed-enhancement MRI (DE-MRI) in asymptomatic patients with diabetes.

RESEARCH DESIGN AND METHODS

In this prospective, two-center study of asymptomatic patients without known cardiac disease (n = 120), two prespecified cohorts underwent a research MRI: 1) a high-risk group with type 1 diabetes and chronic renal insufficiency (n = 50) and 2) an average-risk group with type 2 diabetes (n = 70). The primary end point was a composite of all-cause mortality and clinical MI.

RESULTS

Overall, the prevalence of unrecognized MI was 19% by DE-MRI (28% high-risk group and 13% average-risk group) and 5% by electrocardiography. During up to 5 years of follow-up with a total of 460 patient-years of follow-up, the rate of death/MI was markedly higher in patients with diabetes with (vs. without) unrecognized MI (all 44% vs. 7%, high-risk group 43% vs. 6%, and average-risk group 44% vs. 8%; all P < 0.01). After adjustment for Framingham risk score, left ventricular ejection fraction, and diabetes type, the presence of unrecognized MI by DE-MRI conferred an eightfold increase in risk of death/MI (95% CI 3.0-21.1, P < 0.0001). Addition of unrecognized MI to clinical indices significantly improved model discrimination for adverse events (integrated discrimination improvement = 0.156, P = 0.001).

CONCLUSIONS

Unrecognized MI is prevalent in asymptomatic patients with diabetes without a history of cardiac disease and confers a markedly increased risk of death and clinical MI.

Is mitral valve disease treated differently in men and women?

PURPOSE

This study was performed to determine if there is a sex-based bias in referral practices, complexity of disease, surgical treatment, or outcomes in patients undergoing mitral valve surgery at our institution.

METHODS

Data were collected from the Cardiovascular Research Database of the Clinical Trial Unit of the Bluhm Cardiovascular Institute at Northwestern Memorial Hospital and they were defined according to the Society of Thoracic Surgeons National Database ( www.sts.org ). All patients who had mitral valve replacement, mitral valve repair with annuloplasty ring placement, and mitral valve annuloplasty alone were evaluated, including patients who underwent concomitant tricuspid valve surgery, atrial fibrillation ablation, patent foramen ovale closure, and coronary artery bypass grafting. An unmatched comparison was made between the 836 men and 600 women in the entire cohort (N = 1436) and propensity score-matching was performed in 423 pairs of men and women. Additional propensity score-matching for 219 pairs of men and women with Type II mitral valve functional class and no coronary artery disease and for 68 pairs of men and women with Type 1 or Type IIIb mitral valve functional class. Propensity score matching was used to compare sex differences involving a greedy algorithm with a caliper of size 0.1 logit propensity score standard deviation units.

RESULTS

Between 1 April 2004 and 30 June 2017, 1436 patients (41.8% women, mean age 61.1 ± 12.6 years (men), 62.9 ± 13.3 years (women)) underwent mitral valve surgery. The unmatched comparison for the entire cohort showed that, on average, at the time of surgery, women had higher Society of Thoracic Surgery risk scores, were older and had more heart failure, coronary artery disease, and mitral stenosis than men. Women received proportionately fewer mitral repairs and more atrial fibrillation ablation, and tricuspid valve surgery. Women had longer intensive care unit and hospital stays, required more dialysis, and suffered more transient ischemic attacks and cardiac arrests postoperatively, and 30-day mortality rate was higher for women. However, propensity score-matching of 846 of the patients (423 men; 423 women) indicated that both the surgical approaches and surgical outcomes were comparable for men and women who had similar levels of disease and co-morbidities. Additional propensity score-matching of only those patients with degenerative mitral regurgitation (DMR) (219 men; 219 women) and those with Type 1 or Type III mitral valve disease showed no differences in the surgical procedures performed or in 30-day mortality rates.

CONCLUSIONS

Women appear to be referred for mitral valve surgery later in the course of their disease, which could possibly be on the basis of sex bias, but they may also have a more aggressive form of mitral valve disease than men. Regardless of the reasons for the later referral of women for mitral valve surgery, the clinical outcomes are dependent upon the severity of the mitral disease and associated co-morbidities at the time of surgery, not on the basis of sex bias.

Prognostic Value of Vasodilator Stress Cardiac Magnetic Resonance Imaging: A Multicenter Study With 48 000 Patient-Years of Follow-up

Importance

Stress cardiac magnetic resonance imaging (CMR) is not widely used in current clinical practice, and its ability to predict patient mortality is unknown.

Objective

To determine whether stress CMR is associated with patient mortality.

Design, Setting, and Participants

Real-world evidence from consecutive clinically ordered CMR examinations. Multicenter study of patients undergoing clinical evaluation of myocardial ischemia. Patients with known or suspected coronary artery disease (CAD) underwent clinical vasodilator stress CMR at 7 different hospitals. An automated process collected data from the finalized clinical reports, deidentified and aggregated the data, and assessed mortality using the US Social Security Death Index.

Main Outcomes and Measures

All-cause patient mortality.

Results

Of the 9151 patients, the median (interquartile range) patient age was 63 (51-70) years, 55% were men, and the median (interquartile range) body mass index was 29 (25-33) (calculated as weight in kilograms divided by height in meters squared). The multicenter automated process yielded 9151 consecutive patients undergoing stress CMR, with 48 615 patient-years of follow-up. Of these patients, 4408 had a normal stress CMR examination, 4743 had an abnormal examination, and 1517 died during a median follow-up time of 5.0 years. Using multivariable analysis, addition of stress CMR improved prediction of mortality in 2 different risk models (model 1 hazard ratio [HR], 1.83; 95% CI, 1.63-2.06; P < .001; model 2: HR, 1.80; 95% CI, 1.60-2.03; P < .001) and also improved risk reclassification (net improvement: 11.4%; 95% CI, 7.3-13.6; P < .001). After adjustment for patient age, sex, and cardiac risk factors, Kaplan-Meier survival analysis showed a strong association between an abnormal stress CMR and mortality in all patients (HR, 1.883; 95% CI, 1.680-2.112; P < .001), patients with (HR, 1.955; 95% CI, 1.712-2.233; P < .001) and without (HR, 1.578; 95% CI, 1.235-2.2018; P < .001) a history of CAD, and patients with normal (HR, 1.385; 95% CI, 1.194-1.606; P < .001) and abnormal left ventricular ejection fraction (HR, 1.836; 95% CI, 1.299-2.594; P < .001).

Conclusions and Relevance

Clinical vasodilator stress CMR is associated with patient mortality in a large, diverse population of patients with known or suspected CAD as well as in multiple subpopulations defined by history of CAD and left ventricular ejection fraction. These findings provide a foundational motivation to study the comparative effectiveness of stress CMR against other modalities.

Burden of medical co-morbidities and benefit from surgical revascularization in patients with ischaemic cardiomyopathy

AIMS

The landmark STICH trial found that surgical revascularization compared to medical therapy alone improved survival in patients with heart failure (HF) of ischaemic aetiology and an ejection fraction (EF) ≤ 35%. However, the interaction between the burden of medical co-morbidities and the benefit from surgical revascularization has not been previously described in patients with ischaemic cardiomyopathy.

METHODS AND RESULTS

The STICH trial (ClinicalTrials.gov Identifier: NCT00023595) enrolled patients ≥ 18 years of age with coronary artery disease amenable to coronary artery bypass grafting (CABG) and an EF ≤ 35%. Eligible participants were randomly assigned 1:1 to receive medical therapy (MED) (n = 602) or MED/CABG (n = 610). A modified Charlson co-morbidity index (CCI) based on the availability of data and study definitions was calculated by summing the weighted points for all co-morbid conditions. Patients were divided into mild/moderate (CCI 1-4) and severe (CCI ≥ 5) co-morbidity. Cox proportional hazards models were used to evaluate the association between CCI and outcomes and the interaction between severity of co-morbidity and treatment effect. The study population included 349 patients (29%) with a mild/moderate CCI score and 863 patients (71%) with a severe CCI score. Patients with a severe CCI score had greater functional limitations based on 6-min walk test and impairments in health-related quality of life as assessed by the Kansas City Cardiomyopathy Questionnaire. A total of 161 patients (Kaplan-Meier rate = 50%) with a mild/moderate CCI score and 579 patients (Kaplan-Meier rate = 69%) with a severe CCI score died over a median follow-up of 9.8 years. After adjusting for baseline confounders, patients with a severe CCI score were at higher risk for all-cause mortality (hazard ratio 1.44, 95% confidence interval 1.19-1.74; P < 0.001). There was no interaction between CCI score and treatment effect on survival (P = 0.756).

CONCLUSIONS

More than 70% of patients had a severe burden of medical co-morbidities at baseline, which was independently associated with increased risk of death. There was not a differential benefit of surgical revascularization with respect to survival based on severity of co-morbidity.

Limitations in the Assessment of Prosthesis-Patient Mismatch

Background Prosthesis-patient mismatch (PPM) after aortic valve replacement (AVR) may affect survival but data are conflicting. It is assessed by relating effective orifice area (EOA) to body surface area (EOAi). EOA is patient-specific as the result of flow-velocity times area at the individual patient's outflow tract levels (LVOTA) divided by trans-prosthetic flow velocity. However, some studies use projected EOAs (i.e., valve size associated EOAs from other patient populations) to assess how PPM affects outcome.

Methods We analyzed 76 studies addressing hemodynamic outcome and/or mortality after bioprosthetic AVR.

Results In 48 studies, projected or measured EOA for calculation of EOAi and PPM assessment was used (of which 25 demonstrated an effect on survival). We identified 28 additional studies providing measured EOA values and the corresponding Bernoulli's pressure gradients after AVR. Despite EOA being a patient-specific parameter, 77% of studies assessing a PPM impact on survival used projected EOAs. The 28 studies are providing measured EOA values and the corresponding Bernoulli's pressure gradients in patients after AVR showed a highly significant, linear relationship between EOA and Bernoulli's gradient. Considering this relationship, it is surprising that relating EOA to body surface area (BSA) (EOAi) is standard but relating pressure gradients to BSA is not.

Conclusion We conclude that the majority of studies assessing PPM have used false assumptions because EOA is a patient-specific parameter and cannot be transferred to other patients. In addition, the use of EOAi to assess PPM may not be appropriate and could explain the inconsistent relation between PPM and survival in previous studies.

Differential Impact of Mitral Valve Repair on Outcome of Coronary Artery Bypass Grafting With or Without Surgical Ventricular Reconstruction in the Surgical Treatment for Ischemic Heart Failure (STICH) Trial

Background

This study examined the impact of mitral valve repair (MVRe) on survival of patients with moderate or severe (≥2+) MR and ischemic cardiomyopathy randomized to coronary artery bypass grafting (CABG) versus CABG+surgical ventricular reconstruction (SVR) in the STICH trial.

Methods

Among patients with moderate or severe MR and ischemic cardiomyopathy undergoing CABG or CABG+SVR, the impact of MVRe on mortality between the two treatment arms was compared.

Results

Among 867 patients with assessment of baseline MR severity, 211 had moderate or severe MR. After excluding 7 patients who underwent mitral valve replacement, 50, 44, 62, and 48 patients underwent CABG, CABG+MVRe, CABG+SVR, and CABG+SVR+MVRe, respectively. Four-year mortality rates were lower following CABG+MVRe than CABG alone (16% vs. 55%; adjusted hazard ratio [HR] 0.30; 95% CI 0.13-0.71). In contrast, the CABG+SVR+MVRe and CABG+SVR groups had similar 4-year mortality of 39% vs. 39% (adjusted HR 0.88; 95% CI 0.46-1.70). MVRe had a more favorable effect on survival in patients undergoing CABG alone compared to CABG+SVR (p=0.013). Baseline MR severity was similar between patients that received CABG+MVRe and those that underwent CABG+SVR+MVRe. A larger proportion of patients demonstrated a reduction in MR between 4 and 24 months after CABG+MVRe compared to CABG+SVR+MVRe (50.0% versus 25.0%, p=0.023).

Conclusion

In patients with moderate or severe MR and ischemic cardiomyopathy undergoing CABG, MVRe appears to have a favorable effect on survival. The addition of SVR to CABG may attenuate the anticipated benefits of MVRe by limiting the long-term reduction of MR with MVRe.