Reviews of the St Jude Medical EnligHTN Multi-Electrode Renal Denervation System | Which Medical Device

 

The St Jude Medical EnligHTN renal denervation catheter is a monopolar multipoint electrode radiofrequency ablation catheter. There are 4 radiopaque electrodes that are arranged in an expandable basket like configuration with 2 electrodes on opposite sides of the distal basket and two further electrodes more proximally in the same arrangement. The tip of the device features a smooth nitinol cone that allows smooth passage of the catheter into the renal artery. 

 

The tip of the catheter can be deflected by an extendable mechanism on the device handle and the basket is expanded via a turnable dial on the device handle. The catheter is compatible with an 8Fr guiding catheter and comes in two sizes. The smaller sized catheter is suitable for 4-6mm and the larger 5.5-8mm renal arteries.  

 

 

 

The generator displays readings for each individual electrode displaying the temperature and impedence. There is a counting timer for each ablation point and the next electrode automatically turns on once the ablation for the previous electrode finishes. The generator is not as modern in appearance and design as other CE marked systems and requires some training/experience to operate properly and to interpret the temperature and impedence readings. The generator is also quite large in size compared to other CE marked devices. 

 

Once the catheter is positioned within the renal artery and the basket expanded injection of contrast is performed to confirm positioning in the renal artery (below). A test run of the generator should demonstrate a small increase in temperature as well as a stable impedence reading to indicate good wall contact. If there is poor wall contact the basket can be collapsed and the catheter slightly repositioned before expanding and repeating the test run. Individual electrodes can be turned off if required. 

 

 

 

 

 

 

After the first set of ablations have been performed, the catheter is collapsed and then retracted 1cm before being turned approximately 90 degrees and then re-expanded to ensure different locations for the 8 ablation points. Each ablation lasts 90 seconds per electrode and the company recommends 2 sets of 4 ablations per renal artery, totalling 16 ablation points with a total ablation time of 24 minutes. This is on the longer side compared with the other currently available CE marked devices and generally requires more sedation and analgesia, if no general anaesthetic administered,due to the longer procedure time.

 

Results:

The enligHTN-I is a single arm observational study. Inclusion criteria was: 18-80 years old, patients with office systolic blood pressure ≥160mmHg and stable use of ≥3 antihypertensive medications concurrently at maximally tolerated doses for a minimum of 14 days prior to enrolment, one of which was a diuretic or was on a diuretic previously but documented to be diuretic intolerant. Exclusion criteria was: previous renal artery intervention or evidence of renal artery disease (diameter stenosis >30%), renal arteries <4mm or <20mm in length, eGFR <45mL/min/1.73m2 , secondary hypertension, Type 1 diabetes mellitus or haemodynamically significant valvular heart disease. Primary objectives were safety (adverse events) and efficacy (office BP reduction).

 

62 patients were enrolled with 46 patients undergoing renal artery denervation, 67% males. The average number of anti-hypertensive blood pressure medications was 4.1 ± 0.6, office systolic blood pressure 176 ±16 and diastolic blood pressure 96±14. Blood pressure reductions were -28/-10 at 1 month, -27/-10 at 3 months and -26/-10 at 6 months (P<0.0001).  There were 12 non responders (24%) defined as <10mmHg systolic reduction from baseline. 

 

There was 1 reported worsening of pre-existing renal artery stenosis however there were no other renal artery or vascular access complications. Other complications included 1 episode of symptomatic hypotension and 1 worsening of pre-existing proteinuria. There was no significant change in renal function at 1, 3 and 6 months post denervation measured by eGFR, serum creatinine and cystatin C. The blood pressure results are comparable to the Simplicity I registry and Simplicity II trial results at 6 months where blood pressure drops were -22/-10 and -32/-12 respectively (1, 2). 

 

Overall the St Jude Medical EnligHTN renal denervation system is easy to use and early 6 month results are promising. Catheter placement is straight forward once an 8Fr guiding catheter has engaged the renal artery ostium and the catheter responds well to user manipulation.  Training to operate the generator and interpret the readings is required but easy to master. Ablation times are on the longer side and the generator is a little complex to use and bulky however these issues are likely to be addressed in the next generation device.

 

1. Catheter-Based Renal Sympathetic Denervation for Resistant Hypertension. Symplicity HTN-1 Investigators; Krum H, Barman N, Schlaich M, et al. Hypertension. 2011;57:911-917.

2. Esler ME, Krum H, Schlaich M, Schmieder RE, Böhm M and Sobotka PA. One-Year Results From the Symplicity HTN-2 Randomized, Controlled Trial Renal Sympathetic Denervation for Treatment of Drug-Resistant Hypertension. Circulation. 2012;126:2976-2982.