Cath Lab Digest

LONDON, UK (GlobalData), 4 October 2012 - A study released by the Journal of the American College of Cardiology has highlighted an additional benefit of treating resistant hypertension with renal denervation (RDN). The study found that using RDN in patients who were not responding well to their prescription of three or more antihypertensives proved more cost effective in the long run than simply treating patients with the medications alone. The health economics analysis was published after a large collection of clinical trials had validated the positive effect the therapy had on reducing blood pressure in this small segment of the hypertensive population. GlobalData, a global business intelligence provider, believes future clinical trials will continue focusing on these small and targeted segments before they begin investigating its effects in the much larger ‘mild to moderate’ population.

Hypertensive patients typically exhibit a hyperactive sympathetic nervous system (SNS). This neural system is responsible for the body’s fight or flight response to stimuli, including blood vessel constriction and increased heart rate. It has been shown that surgical disruption of these SNS nerve fibers, which are primarily found in the kidney, can significantly contribute to an improvement in blood pressure. The procedure uses a catheter that is threaded through a patient’s femoral artery to access their kidneys. The catheter then emits a low power radiofrequency wave to disable targeted nerves. The leading denervation systems are the Symplicity by Medtronic, EnligHTN by St. Jude Medical and the Paradise System by ReCor Medical.

The device utilized in the cost effectiveness study was Medtronic’s Symplicity system. The team behind the research utilized a Markov model to determine the improvements in cost effectiveness that RDN would bring in the long run. The study’s results predicted that the discounted incremental cost-effectiveness ratio of treatment with renal denervation would be $3,071 per Quality Adjusted Life Year (QALY). QALY is a measure used to compare different treatments for the same or different conditions. It provides a measure of how many years of life of reasonable quality a person might gain as a result of the treatment. When combined with a cost measure, the cost-effectiveness ratio provides a measure of how much a particular treatment costs to produces a single quality life year. The standard recognized measure of this in the US is $50,000/QALY and is much higher than the number discovered in this study.

In addition to predictive modeling studies, clinical trials have highlighted the physiological advantages of RDN-incorporated therapy. Clinical trials for Medtronic’s Symplicity system have demonstrated blood pressure decreases of 32/12mmHg at six months. Similar results were shown in trials for St. Jude Medical’s Enlightn system, with 78% of patients having systolic BP drops of >10mmHg in one month.

However, these clinical trial results only apply to a small portion of the hypertensive community. In the United States, for example, there are over 60 million adults living with hypertension. Of that group only 8.9%, or 5.3 million adults, have resistive hypertension. That’s a very small fraction of a disease that affects over a sixth of the country’s population. It’s no coincidence, though, that this patient population was targeted. A common strategy used by device manufacturers is to conduct initial safety and efficacy trials on the sickest patient population who have exhausted their treatment options. If improvements are seen in the sickest patients, then a stronger argument is built for FDA approval. Both ReCor Medical and St. Jude Medical are in the midst of IDE clinical trials assessing their RDN systems in resistive hypertensive patients. Additionally, Medtronic began studying the effects of their Symplicity system in patients with chronic heart failure – a condition affecting approximately 4–5 million individuals in the United States.

GlobalData believes these manufacturers will continue studying their device’s effect in small, specific patient populations to increase its indication portfolio and obtain a competitive edge. Secondary hypertension related to glandular disorders will likely be explored in subsequent trials. Hyperthyroidism is the oversecretion of thyroid hormone in the body. Too much of this hormone results in increased cardiac contractions and subsequent hypertension. Researchers may find that RDN plays a role in alleviating hypertension in the 3.9 million patients this condition afflicts in the United States. Additionally, two forms of adrenal gland disorders (hyperaldosteronism and pheochromocytoma) lead to excessive production of hormones (aldosterone and adrenaline, respectively) that subsequently increase blood pressure. Both conditions are listed as rare diseases by the National Institutes of Health, indicating they affect fewer than 200,000 patients in the United States.

Once the indication portfolios of RDN systems have expanded, device manufacturers will then begin exploring its effects in the larger ‘mild to moderate’ population. RDN is currently being studied in conjunction with a regimen of antihypertensive medications. Trials for the ‘mild to moderate’ population may investigate the potential for RDN to replace these medications altogether. Some studies estimate that up to 60% of hypertensive patients do not take their medications as prescribed. This implies that patients may be developing further health-related complications of their own accord. If results of these trials prove positive, then patients who were not responding well to an antihypertensive therapy as a result of non-compliance could be renally ablated and free of future missed prescriptions. Not only would there be a significant cost saving to national healthcare systems, but the treatment would decrease the risk probability of additional cardiovascular complications.

While these clinical trials will take years to initiate and conduct, the potential for this new treatment modality is huge and may help better treat a condition that is becoming ever more prevalent. Time invested in exploring this potential is well worth it.