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
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
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.