Determining the status of small arteries (the microvasculature of the brain

Guy M. McKhann, M.D.

Johns Hopkins University

Funded in December, 2011: $150000 for 2 years
LAY SUMMARY .

LAY SUMMARY

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Assessing stroke risk in patients undergoing non-surgical aortic valve replacement

This study will assess whether the risk of stroke following a non-surgical catheter-based approach to replacing the aortic valve in older patients is associated with the procedure or with patients’ underlying vascular risk factors.   

The aortic valve lies between the heart’s left ventricle and the aorta. When this ventricle contracts, the aortic valve’s three “leaflets” open and blood ejected from the ventricle flows from the aorta to blood vessels throughout the body. Following contraction, the leaflets close the valve and prevent reflux of blood back into the heart. About five percent of people aged 75 and older, though, have a narrowing (stenosis) of the aortic valve. When heart failure from aortic stenosis occurs, 50 percent of these people die within two years. Because these patients are sicker and older, they are not good candidates for open heart surgical replacement with either artificial or animal tissue valves. Instead, many of them undergo a recently developed non-surgical alternate procedure called transcatheter aortic valve replacement (TAVR). This transcatheter approach compares favorably to surgery in recovery time (hours to days), is equally effective, and studies suggest both surgery and TAVR are superior to medical therapy.   Nonetheless, strokes occur about twice as often with TAVR as with surgical or medical intervention.   The investigators will determine whether stroke and the occurrence of ischemic embolic events are associated with the TAVR procedure or with patients’ underlying risk factors, such as: age, hypertension, diabetes, history of previous stroke, and evidence of peripheral vascular disease.

They will use the same design as in a similar Dana-funded study they conducted to determine whether cognitive decline was associated with coronary artery by-pass graft (CABG) surgery that either did or did not involve use of an oxygen pump (“on-pump” or “off-pump,” respectively). Theirs was the first study of that specific question to use a control heart-healthy group as well as the two CABG surgical groups (on-pump and off-pump) and a medically treated group. It also was the first to utilize cognitive testing and MRI imaging prior to and following the therapeutic interventions in patients, and during similar time frames in the healthy volunteers.  They found that long-term cognitive decline in patients following CABG surgery—whether or not an oxygen pump was used—was associated with patients’ underlying vascular risk factors rather than the surgery. Additionally, however, they found a risk of stroke associated with CABG surgery on-pump and off-pump. They then developed a paradigm for calculating a patient’s risk, based on factors known prior to surgery, which can be used to choose among therapeutic options, modify the surgery, and predict outcomes.  Similarly, for this TAVR study the investigators will employ cognitive testing and MRI imaging in heart-healthy volunteers and in about 50 patients undergoing TAVR and in patients receiving surgical valve replacement. Patients undergoing surgery or the TAVR procedure will be enrolled at Johns Hopkins but additional TAVR-group patients also may be enrolled at Harvard-Beth Israel Hospital in Boston. The investigators will determine: 1) the incidence of stroke by clinical evaluation prior to, and immediately and one month following TAVR or valve replacement surgery; and 2) the presence of recent embolic ischemic events in the brain using Diffusion-Weighted MRI following the surgical or catheter-based procedure. Investigators then will develop a predictive paradigm for stroke and embolic ischemic events following TAVR, consisting of the potential risk factors identified.  

Significance: Results will determine whether stroke and ischemic embolic events are associated with the non-surgical TAVR procedure for aortic valve replacement or with underlying risk factors, and lead to improved methods for predicting treatment outcomes and minimizing risks.

This information will help both physicians and patients decide the best choice for therapy.