Renal denervation in a patient with two renal accessory arteries: A case report

Abstract

Percutaneous renal denervation has emerged as an effective adjunct in the management of resistant hypertension. However, the limits of the renal anatomical criteria that can be successfully treated are still unknown. In this report, we describe the case of a middle-aged man with essential resistant hypertension and two small left accessory renal arteries that underwent renal denervation of both principal renal arteries. He responded well with a progressive reduction in blood pressure measuring of 16/10, 32/17 and 45/24 mmHg at 1, 6 and 12 months, respectively. At 12 months, 94% of ambulatory measurements were below 140/90 mmHg and the number of anti-hypertensive medications had decreased from six to three. Thus, it would appear that the presence of two non-ablated left accessory renal arteries does not influence the response to renal denervation.

Key Words::

• resistant hypertension
• renal denervation
• renal accessory artery

Introduction

Current guidelines define resistant hypertension as blood pressure (BP) values exceeding the goal despite medical therapy with at least three drugs (including a diuretic) in adequate doses (1). The global incidence of resistant hypertension is 1.5% and represents about one-third of patients with hypertension. This condition leads to a doubled risk of cardiovascular disease compared with non-resistant hypertension (2). A novel approach to treat essential resistant hypertension based on percutaneous renal denervation (RDN) has been validated in the last few years (3,4). In this report, we present the long-term outcome of a patient with resistant hypertension and two left accessory renal arteries, who underwent denervation of both principal renal arteries.

Case presentation

We present a 61-year-old man with a normal BMI and no history of alcohol abuse or inappropriate salt intake. He had a 20-year history of uncontrolled hypertension despite a combination of six different antihypertensive drugs at target dose (bisoprolol 10 mg, ramipril 10 mg, candesartan 32 mg, hydrochlorothiazide 25 mg, minoxidil 10 mg and piretanide 6 mg) with optimal patient compliance to therapy. The average ambulatory BP was 162/102 mmHg with a non-dipper night pattern. During ambulatory BP monitoring (ABPM), several systolic peaks (SBP > 220 mmHg) were recorded. Regarding hypertensive target organ damage, he exhibited mild left ventricular concentric hypertrophy and a previous lacunar stroke with secondary vascular parkinsonism. Renal function was preserved (glomerular filtration rate, GFR = 122 ml/min) and fundoscopy did not show any retinopathy. The patient underwent the recommended work-up to rule out all possible causes of secondary hypertension: laboratory tests (creatinine 0.7 mg/dl, renin 3.3 μIU/ml, aldosterone 195 pg/ml, urinary sodium excretion 77.5 mEq/24 h, normal values of urinary cortisol and urinary metanephrines) and imaging exams (abdomen ultrasound scan, sequential renal scintigraphy, total body angio- magnetic resonance imagining (MRI), renal arteries Doppler, sequential renal scintigraphy, night oximetry) in order rule out all possible causes of secondary hypertension. Magnetic resonance angiography (MRA) showed the presence of two small left accessory arteries originating directly from the abdominal aorta and excluded the presence of renal artery stenosis. Given the essential nature of the resistant hypertension, the patient was eligible for percutaneous renal denervation. In May 2011, he underwent percutaneous renal sympathetic denervation with the Ardian Symplicity radiofrequency ablation catheter (Medtronic Inc., Minneapolis, MN) as previously described (3,4). Aortography confirmed the presence of two left renal accessory arteries with a diameter < 4 mm, which is a technical contraindication for catheter ablation (Figure 1). A total of six ablation points were performed in a spiral fashion in both principal renal arteries. Final angiography of both main renal arteries showed no vasospasm, stenosis or dissection. During hospitalization, no vascular or renal complications were observed.

Figure 1. Aortography: arrows indicate two left renal accessory arteries.

At 1 month follow-up, ABPM showed a significant decrease in blood pressure: mean values were 146/92 mmHg, a reduction of 16/10 mmHg. These results improved at 6 months ABPM follow-up with mean values of 130/85 mmHg (− 32/− 17 mmHg) and at 12 months ABPM follow-up with 117/78 mmHg (− 45/− 24 mmHg) (Figure 2). The percentage of ABPM under target values of 140/90 mmHg were 26%, 70.5% and 94.4%, respectively at 1, 6 and 12 months follow-up (Figure 3). No systolic peaks were recorded at 1-year ABPM with evidence of conserved dipper night pattern. Antihypertensive therapy was gradually reduced from six to three drugs and at 12 months the patient was taking spironolactone 25 mg die, bisoprolol 5 mg die and aliskiren 300 mg die. This specific regimen was chosen as it provided the antihypertensive combination that produced the greatest efficacy/tolerance profile in this challenging patient who suffered numerous side-effects from the other antihypertensive drugs.

Figure 2. Systolic and diastolic blood pressure reduction at 1, 3, 6 and 12 months follow-up.

Figure 3. Percentage of blood pressure measurements under target blood pressure value of 140/90 mmHg or leading to stage I, II or III of hypertension, prior to renal denervation (RDN) and at 1, 6 and 12 months follow-up.

No changes in renal function were noted during the follow-up (serum creatinine at 1-year was 0.9 mg/dl, GFR > 120 ml/min). Urinary salt excretion and renin concentration were normal at 1 month, showing values comparable with those before the procedure (urinary salt excretion 93 mEq/24 h, renin 7.20 μIU/ml in orthostatic position, 3.60 μIU/ml in supine position). There was also no evidence of post-ablation renal artery injury on the repeat MRA performed 6 months after the procedure.

Discussion

Since 1930, surgical sympathectomy was proposed as an effective treatment for resistant hypertension (5). Because of the high risk, invasiveness and morbidity of this technique and the discovery of new effective antihypertensive drugs, surgical sympathectomy was abandoned. The rationale of interfering with sympathetic overdrive in order to reduce blood pressure was revisited in the last few years with the development of a percutaneous renal denervation procedure. The trans-catheter approach allows selective radiofrequency ablation of nervous termination lying in the renal arterial wall. Some studies, evaluating muscle nerve activity and norepinephrine spillover, confirmed that a reduction of sympathetic nerve activity is associated with blood pressure drop after renal denervation (6). The Symplicity HTN-1 pilot study demonstrated the feasibility and the safety of percutaneous renal denervation in patients with resistant hypertension. The results at 24 months show a reduction in blood pressure of 32/14 mmHg, without significant adverse events (3). The Symplicity HTN-2 study, a multicenter, prospective, randomized controlled trial, randomly assigned patients to renal denervation or medical therapy. In the ablated group, a statistically significant decrease of 32/12 mmHg was present at 6 months follow-up, whereas in the control group, no changes in blood pressure were observed. No deterioration in renal function or renal artery stenosis has been described (4).

We would also like to highlight the fundamental role of an antialdosteronic drug in our patient, despite the exclusion of a primary hyperaldosteronism. Several studies demonstrate the efficacy of spironolactone in treating resistant hypertension and show a substantial blood pressure reduction after its addition (ranging from 21.7 to 25 mmHg systolic and from 8.5 to 12.5 mmHg diastolic office blood pressure) (7–9). The most recent randomized study (ASPIRANT trial) assessed the effect of the addition of spironolactone 25 mg on blood pressure in patients with resistant arterial hypertension who were randomly assigned to receive spironolactone or a placebo. At 8 weeks, systolic values were significantly decreased by spironolactone compared with control group (10).

Our case report supports previous data on effective and significant blood pressure reduction after renal denervation in patients with medically resistant hypertension. We describe a unique case of successful sympathetic renal denervation in a patient with two accessory renal arteries. Accessory renal arteries are aberrant arterial branches originating directly from the aorta and usually serving a small portion of the kidney found in 25–50% of normal patients at autopsy (11). Some studies support the hypothesis that accessory renal arteries may lead to systemic arterial hypertension by the activation of the renin–angiotensin system as a consequence of higher resistance across the accessory artery (12,13). On the other hand, some studies demonstrate that there is no statistically significant difference in the prevalence of hypertension between patients with and without renal accessory arteries, meaning that accessory arteries are vascular anomalies but not a direct cause of hypertension (14). Actually, the presence of multiple renal arteries is considered an exclusion criterion for renal denervation. With our case, we demonstrate that the presence of small accessory arteries is not a relevant mechanism in resistant hypertension pathogenesis and does not influence the long-term outcome of the procedure.

Conclusions

Renal denervation appeared safe and effective in this patient despite the presence of non-ablated small accessory arteries, which did not undergo ablative treatment.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.