Confounding Factors Which Lead to Unexpected Results of Renal Denervation Trial

A new analysis of the SYMPLICITY HTN-3 trial, aimed at lowering the blood pressure with a procedure called as renal denervation, has identified factors like variations in the way the procedure was performed and changes in patients' medications and drug adherence, which may have had a significant impact on the results, eventually halting the renal denervation procedure.

Renal denervation is a minimally invasive procedure which involves deactivating the renal nerves with radiofrequency ablation, a series of 2 minute blasts of radiofrequency energy, with a catheter inserted via an artery in the groin to reach the renal arteries. This nerve disruption reduces the sympathetic nerve drive, and a significant and sustainable reduction in blood pressure is achieved.

Results of the SYMPLICITY HTN-3 trial appeared to show that there was no significant difference in patient outcome between renal denervation and a sham procedure among patients with drug resistant hypertension, which resulted in referrals for the procedure drying up completely, making further trials almost impossible.

Sub-analysis by Prof Kandzari, director of interventional cardiology and chief scientific officer at Piedmont Heart Institute, Atlanta, USA, and his colleagues found a link between the number of ablations and the subsequent reduction in blood pressure. Prof Kandzari said, "Patients who received between 11 and 14 or more renal ablations had reductions in systolic blood pressure (as measured during visits to the clinic) of 5-14 mmHg more than similar patients having the sham procedure. However, a greater effect of renal denervation compared with the sham procedure was not seen in patients who had ten or fewer ablations. Overall, the number of ablation attempts ranged from one to 26, with most patients receiving at least eight ablations. Giving four ablations in a spiral (helical) pattern in both renal arteries was also associated with greater reductions in systolic blood pressure, but this was only done in 19 patients."

Other confounding factors were changes in medications and patient adherence to their drugs. The protocol for the SYMPLICITY HTN-3 trial specified that from the time of enrollment to the end of the 6-month follow-up period, patients should be maintained on several anti-hypertensive medications at highest possible doses, without any changes unless clinically necessary. During this time, approximately 40 percent patients required medication changes; nearly 70% of which were due to patients experiencing adverse events or side-effects related to the maximally-tolerated dosage of their hypertension medications.

This analysis published in the European Heart Journal, opens the field for new clinical trials to confirm that more ablations delivered in a spiral pattern are able to provide an effective denervation.

Source: Medindia

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