ROME – Weekly lipoprotein apheresis in patients with highly refractory angina accompanied by high plasma lipoprotein(a) without elevated LDL cholesterol led to significantly improved myocardial blood flow in a randomized, blinded, sham-controlled clinical trial, Tina Khan, MD, reported at the annual congress of the European Society of Cardiology.
Participants also experienced clinically meaningful improvements in the secondary endpoints of quality of life, angina symptoms, exercise capacity, and atheroma burden, added Dr. Khan of Imperial College London.
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Dr. Tina Khan
Angina pectoris that is refractory to maximal pharmacologic, percutaneous, and surgical interventions is a major and growing problem. More than 100,000 new cases occur per year in the United States.
“We have a desperate need to develop new therapeutic options,” she said.
Lipoprotein(a), or Lp(a), is a potent independent cardiovascular risk factor. And it figures prominently in refractory angina. Indeed, 60% of the patients with refractory angina screened by Dr. Khan for her clinical trial had an isolated plasma Lp(a) level of 50 mg/dL or more, the threshold at which cardiovascular risk sharply increases. Statins have no effect on Lp(a) levels.
While a couple of observational cohort studies have suggested that reducing elevated Lp(a) in patients with cardiovascular disease is associated with a decrease in major adverse cardiovascular events, until now there have been no randomized controlled trials of apheresis as Lp(a)-lowering therapy in patients with refractory angina, according to Dr. Khan.
She presented a randomized, crossover design study in 20 patients with severe refractory angina and an Lp(a) in excess of 50 mg/dL but no elevation in LDL. They underwent 3 months of blinded weekly extracorporeal lipoprotein apheresis using a dextran sulfate filtration system or sham apheresis, followed by a month-long washout period. Participants were then crossed over to the other study arm to increase the statistical power of this small study.
The primary study endpoint was change in myocardial perfusion reserve as measured by cardiovascular magnetic resonance imaging at baseline and after 3 months of true or sham apheresis. The myocardial perfusion reserve index improved by a net of 0.63 after apheresis from a baseline of 1.45. This effect was strongly driven by a substantial increase in stress myocardial perfusion, with very little change in perfusion at rest.
Significant improvements were also recorded after apheresis in the secondary endpoints of change in carotid atheroma as reflected in total carotid wall volume, improvement on various domains of the Seattle Angina Questionnaire, physical limitations as scored on the SF-36, and exercise capacity as measured on the 6-minute walk test.
Discussant Peter Libby, MD, was effusive in his praise for Dr. Khan’s study.
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Dr. Peter Libby
“This is a wonderful example of how we may be able to offer new hope for patients and families with high Lp(a),” declared Dr. Libby, chief of cardiovascular medicine at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School, Boston.
He approved of the methodology and embraced what he called “the intriguing preliminary picture of benefit for lowering Lp(a).”
Most of all, he was pleased that Dr. Khan’s well conducted albeit small study has thrown a spotlight on Lp(a), which he characterized as a greatly underappreciated causal risk factor for a range of cardiovascular diseases.
“Lp(a) stands out like a Manhattan skyscraper as the major driver of calcific aortic stenosis, an epidemic that we see in our aging population,” he observed.
He added that topics worthy of further research with regard to Lp(a)-lowering apheresis as a treatment for refractory angina include the question of whether the mechanism of benefit involves structural changes in atherosclerosis or functional changes. And if it’s the latter, is it a matter of changes in microvascular function, macrovascular function, or a combination of the two?
Apheresis is extremely costly, inconvenient, and invasive, and there are only several dozen apheresis centers in the United States. So the future of Lp(a)-lowering to treat refractory angina, calcific aortic stenosis, and other cardiovascular conditions where elevated Lp(a) is an important player may lie in pharmacotherapy with the PCSK9 inhibitors, Dr. Libby predicted.
He cited “very promising” data showing that evolocumab (Repatha) and alirocumab (Praluent) lower Lp(a) in dose-dependent fashion. Ongoing very large clinical trials with hard clinical endpoints should eventually provide key information regarding the cardiovascular benefits of lowering Lp(a).
“We may be entering an era where we may be able to offer our patients and families – because this is often a familial problem – a non-apheresis approach to controlling what we are learning is a very important causal risk factor for atherosclerosis,” Dr. Libby said.