Research Spotlight

Sapir-Pichhadze, R. and B. Kaplan (2020). “Seeing the Forest for the Trees: Random Forest Models for Predicting Survival in Kidney Transplant Recipients.” Transplantation 104(5): 905-906.

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Most practice guidelines are geared toward the “average patient.” Machine learning tools can capture the complexity of individual patients’ characteristics and aid transplant clinicians with patient-specific care decisions. As these tools become more prevalent, it is important to develop best practice guidelines and ensure there is regulatory oversight on their development and application. (Excerpt from text; no abstract available.)

Rooney, M., T. Bottiglieri, B. Wasek-Patterson, A. McMahon, C. F. Hughes, A. McCann, G. Horigan, J. J. Strain, H. McNulty and M. Ward (2020). “Impact of the MTHFR C677T polymorphism on one-carbon metabolites: Evidence from a randomised trial of riboflavin supplementation.” Biochimie Apr 21. pii: S0300-9084(20)30074-2. [Epub ahead of print].

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Homozygosity for the C677T polymorphism in MTHFR (TT genotype) is associated with a 24-87% increased risk of hypertension. Blood pressure (BP) lowering was previously reported in adults with the TT genotype, in response to supplementation with the MTHFR cofactor, riboflavin. Whether the BP phenotype associated with the polymorphism is related to perturbed one-carbon metabolism is unknown. This study investigated one-carbon metabolites and their responsiveness to riboflavin in adults with the TT genotype. Plasma samples from adults (n 115) screened for the MTHFR genotype, who previously participated in RCTs to lower BP, were analysed for methionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), betaine, choline and cystathionine by liquid chromatography tandem mass spectrometry (LC-MS/MS). The one-carbon metabolite response to riboflavin (1.6 mg/d; n 24) or placebo (n 23) for 16 weeks in adults with the TT genotype was also investigated. Plasma SAM (74.7 +/- 21.0 vs 85.2 +/- 22.6 nmol/L, P = 0.013) and SAM:SAH ratio (1.66 +/- 0.55 vs 1.85 +/- 0.51, P = 0.043) were lower and plasma homocysteine was higher (P = 0.043) in TT, compared to CC individuals. In response to riboflavin, SAM (P = 0.008) and cystathionine (P = 0.045) concentrations increased, with no responses in other one-carbon metabolites observed. These findings confirm perturbed one-carbon metabolism in individuals with the MTHFR 677TT genotype, and for the first time demonstrate that SAM, and cystathionine, increase in response to riboflavin supplementation in this genotype group. The genotype-specific, one-carbon metabolite responses to riboflavin intervention observed could offer some insight into the role of this gene-nutrient interaction in blood pressure.

Roberts, C. S., R. C. Stoler and W. C. Roberts (2020). “The Case for Primary Prevention of Atherosclerotic Events from Study of a Single Patient.” Am J Cardiol 125(9): 1443-1445.

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This report describes a 64-year-old woman who presented with unstable angina pectoris, her first atherosclerotic event, and who underwent coronary bypass including endarterectomy of the entire right coronary artery which was diffusely and severely narrowed by atherosclerotic plaque. Preoperatively, she fulfilled none of the present-day criteria for lipid-lowering drug therapy. The report demonstrates the deficiency of present-day lipid-lowering drug guidelines and emphasizes the need to switch emphasis from decreasing risk of an atherosclerotic event to the prevention of arterial plaques, a goal which will require a much lower threshold of low-density lipoprotein cholesterol to initiate drug therapy.

Pineda, E. D., I. C. Liao, P. J. Godley, J. B. Michel and K. L. Rascati (2020). “Cardiovascular Outcomes Among Patients with Type 2 Diabetes Newly Initiated on Sodium-Glucose Cotransporter-2 Inhibitors, Glucagon-Like Peptide-1 Receptor Agonists, and Other Antidiabetic Medications.” J Manag Care Spec Pharm 26(5): 610-618.

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BACKGROUND: Cardiovascular disease (CVD) remains the most prevalent cause of morbidity and mortality in patients with type 2 diabetes (T2D) and is a primary driver for health care costs associated with diabetes management. Sodium-glucose cotransporter-2 inhibitors (SGLT-2is) and glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have demonstrated significant reductions in cardiovascular endpoints in clinical trials compared with placebo. However, it is uncertain whether these findings can be applied to the broader T2D population because these trials specifically included high-risk patients with established CVD. OBJECTIVE: To evaluate and compare cardiovascular outcomes among adults with T2D newly initiated on SGLT-2is, GLP-1 RAs, and other antidiabetic medications (oADMs) in a real-world setting. METHODS: This retrospective new-user cohort study used administrative claims and electronic health record data from an integrated delivery network in Texas. Patients aged >/=18 years with T2D and >/=1 prescription claim for an SGLT-2i, a GLP-1 RA, or an oADM filled between April 2013 and December 2018 were included. Patients were divided into three 1:1 propensity-matched groups according to index medication identified. Primary outcomes were heart failure hospitalization and a composite end-point of myocardial infarction, stroke, unstable angina, or coronary revascularization. Cox proportional hazards regression was used to compare cumulative incidence of all outcome variables. RESULTS: Among 9,477 patients, 1,134 were initiated on SGLT-2is, 1,072 on GLP-1 RAs, and 7,271 on oADMs. Patients initiating SGLT-2is versus oADMs had significantly lower risk of the composite endpoint (HR = 0.64, 95% CI = 0.46-0.90), heart failure hospitalization (HR = 0.56, 95% CI = 0.39-0.81), and unstable angina requiring hospitalization (HR = 0.56, 95% CI = 0.39-0.81). Patients initiating GLP-1 RAs compared with oADMs had significantly lower risk of the composite endpoint (HR = 0.71, 95% CI = 0.52-0.98) and unstable angina requiring hospitalization (HR = 0.60, 95% CI = 0.41-0.86). No differences in cardiovascular outcomes were found between SGLT-2is and GLP-1 RAs. CONCLUSIONS: Both SGLT-2is and GLP-1 RAs showed significant reductions in the composite outcome and unstable angina requiring hospitalization versus oADMs. However, only SGLT-2is were associated with a lower risk for heart failure hospitalizations. Nevertheless, cardiovascular outcomes were similar between SGLT-2is and GLP-1 RAs. DISCLOSURES: No outside funding supported this study. The authors have no conflicts of interest to report.

Pibarot, P., E. Salaun, A. Dahou, E. Avenatti, E. Guzzetti, M. S. Annabi, O. Toubal, M. Bernier, J. Beaudoin, G. Ong, J. Ternacle, L. Krapf, V. H. Thourani, R. Makkar, S. K. Kodali, M. Russo, S. R. Kapadia, S. C. Malaisrie, D. J. Cohen, J. Leipsic, P. Blanke, M. R. Williams, J. M. McCabe, D. L. Brown, V. Babaliaros, S. Goldman, W. Y. Szeto, P. Genereux, A. Pershad, M. C. Alu, K. Xu, E. Rogers, J. G. Webb, C. R. Smith, M. J. Mack, M. B. Leon and R. T. Hahn (2020). “Echocardiographic Results of Transcatheter Versus Surgical Aortic Valve Replacement in Low-Risk Patients: The PARTNER 3 Trial.” Circulation Apr 10. [Epub ahead of print].

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Background: The objective of this study is to compare echocardiographic findings in low risk patients with severe aortic stenosis (AS) following surgical (SAVR) or transcatheter aortic valve replacement (TAVR). Methods: The Placement of Aortic Transcatheter Valves 3 (PARTNER 3) trial randomized 1000 patients with severe AS and low surgical risk to undergo either transfemoral TAVR with the balloon-expandable SAPIEN 3 valve or SAVR. Transthoracic echocardiograms obtained at baseline, and at 30 days and 1 year post-procedure were analyzed by a consortium of 2 echocardiography core laboratories. Results: The percentage of moderate/severe aortic regurgitation (AR) was low and not statistically different between TAVR vs. SAVR groups (30 days: 0.8% vs. 0.2%; p=0.38). However, mild AR was more frequent following TAVR vs. SAVR (30 days: 28.8% vs. 4.2 %; p<0.001). At 1 year, mean transvalvular gradient (13.7+/-5.6 vs. 11.6+/-5.0 mmHg; p=0.12) and aortic valve area (1.72+/-0.37 vs. 1.76+/-0.42 cm(2); p=0.12) were similar in TAVR vs. SAVR. The percentage of severe prosthesis-patient mismatch (PPM) at 30 days was low and similar between TAVR and SAVR (4.6 vs. 6.3%, p=0.30). Valvulo-arterial impedance (Zva), which reflects total left ventricular hemodynamic burden, was lower with TAVR vs. SAVR at 1 year (3.7+/-0.8 vs. 3.9+/-0.9 mmHg/mL/m(2) ; p<0.001). Tricuspid annulus plane systolic excursion (TAPSE) decreased and the percentage of moderate/severe tricuspid regurgitation increased from baseline to 1 year in SAVR, whereas remained unchanged in TAVR. Irrespective of treatment arm, high Zva and low TAPSE, but not moderate/severe AR or severe PPM, were associated with increased risk of the composite endpoint of mortality, stroke and re-hospitalization at 1 year. Conclusions: In patients with severe AS and low surgical risk, TAVR with the SAPIEN 3 valve was associated with similar percentage of moderate/severe AR compared with SAVR, but higher percentage of mild AR. Transprosthetic gradients, valve areas, percentage of severe PPM, and LV mass regression were similar in TAVR versus SAVR. SAVR was associated with significant deterioration of RV systolic function and greater tricuspid regurgitation, which persisted at 1 year. High Zva and low TAPSE were associated with worse outcome at 1 year whereas AR or severe PPM were not.