Management of resistant hypertension in patients with carotid stenosis: high prevalence of renovascular hypertension

Focus on blood pressure levels and variability in the early phase of acute ischemic stroke with hypertension and carotid stenosis

To investigate the optimal blood pressure (BP) levels and relative importance of BP and BP variability in the early phase of acute ischemic stroke (AIS) for hypertensive patients with carotid artery stenosis (CAS). A single‐center cohort study included 750 AIS patients with hypertension and tests were performed for CAS. Participants were categorized to Group 1 (SBP < 140 mm Hg and DBP < 90 mm Hg), Group 2: (SBP: 140–159 mm Hg and or DBP: 90–99 mm Hg), and Group 3: (SBP ≥160 mm Hg and/or DBP ≥100 mm Hg) according to the guidelines. The associations of mean BP levels and variability with outcomes (recurrent stroke, all‐cause death and the composite cardiovascular events) at 6 months were analyzed by Cox proportional hazard models. The associations of BP variability with BP levels and cerebral blood flow (CBF) were analyzed by linear regression and generalized additive models. Both for primary and secondary outcome, more events occurred in Group 1 compared with Group 2, while no significant difference was found in Group 3 with higher BP levels. Lower systolic BP variability showed better prognosis and higher CBF. The associations were more significant in patients with CAS ≥50%. BP variability exhibited a linear negative relationship with BP levels. In the early phase of AIS with hypertension and CAS, maintaining low blood pressure variability may be important to improve outcomes while low BP levels (SBP/DBP < 140/90 mm Hg) were harmful, especially in those patients with CAS ≥ 50%.

Optimal Medical Management of Asymptomatic Carotid Stenosis

Asymptomatic carotid stenosis (ACS) due to atherosclerosis is a risk factor for ipsilateral ischemic cerebrovascular events and cognitive impairment. The prognosis of ACS has improved over the past 4 decades due largely to improvements in medical management. Most patients with ACS can be managed without revascularization, but some patients with vulnerable plaque should be considered for revascularization. Regardless of the decision to refer for revascularization, all patients with ACS should receive intensive medical management. This includes lifestyle modification (Mediterranean diet, exercise, and smoking cessation) and pharmacological therapy (antiplatelets, lipid-lowering agents, blood pressure reduction, and glycemic control). Patients with ACS often have atherosclerosis in other critical locations, and thus optimal medical therapy is likely to reduce events outside the carotid arteries. The nature of optimal medical therapy is described.

Management of asymptomatic carotid stenosis

Patients with asymptomatic carotid stenosis (ACS) are at very high risk of coronary events, so they should all receive intensive medical therapy. What is often accepted as “best medical therapy” is usually suboptimal. Truly intensive medical therapy includes lifestyle modification, particularly smoking cessation and a Mediterranean diet. All patients with ACS should receive intensive lipid-lowering therapy, should have their blood pressure well controlled, and should receive B vitamins for lowering of plasma total homocysteine (tHcy) if levels are high; a commonly missed cause of elevated tHcy is metabolic B12 deficiency, which should be diagnosed and treated. Most patients with ACS would be better treated with intensive medical therapy than with either carotid endarterectomy (CEA) or stenting (CAS). A process called “treating arteries instead of treating risk factors” markedly reduced the risk of ACS in an observational study; a randomized trial vs. usual care should be carried out. The few patients with ACS who could benefit (~15%, or perhaps more if recent evidence regarding the risk of intraplaque hemorrhage is borne out) can be identified by a number of features. These include microemboli on transcranial Doppler, intraplaque hemorrhage, reduced cerebrovascular reserve, and echolucency of plaques, particularly “juxtaluminal black plaque”. No patient should be subjected to CAS or CEA without evidence of high-risk features, because in most cases the 1-year risk of stroke or death with intervention is higher with either CEA (~2%) or CAS (~4%) than with intensive medical therapy (~0.5%). Most patients, particularly the elderly, would be better treated with CEA than CAS. Most strokes can be prevented in patients with ACS, but truly intensive medical therapy is required.

Recanalization of the Chronically Occluded Internal Carotid Artery: Review of the Literature

Introduction

We reviewed the literature on interventions for patients with medically refractory chronically occluded internal carotid artery (COICA) to assess the risks and/or benefits after recanalization via an endovascular technique (ET) or hybrid surgery (HS, i.e., ET plus carotid endarterectomy).

Methods

A systematic search of the electronic databases was performed. Patients with COICA were classified into 4 different categories according to Hasan et al classification.

Results

Eighteen studies satisfied the inclusion criteria. Only 6 studies involved an HS procedure. We identified 389 patients with COICA who underwent ET or HS; 91% were males. The overall perioperative complication rate was 10.1% (95% confidence interval [CI]: 7.4%-13.1%). For types A and B, the successful recanalization rate was 95.4% (95% CI: 86.5%-100%), with a 13.7% (95% CI: 2.3%-27.4%) complication rate. For type C, the success rate for ET was 45.7% (95% CI: 17.8%-70.7%), with a complication rate of 46.0% (95% CI: 20.0%-71.4%) for ET and for the HS technique 87.6% (95% CI: 80.9%-94.4%), with a complication rate of 14.0% (95% CI: 7.0%-21.8%). For type D, the success rate of recanalization was 29.8% (95% CI: 7.8%-52.8%), with a 29.8% (95% CI: 6.1%-56.3%) complication rate. Successful recanalization resulted in a symmetrical perfusion between both cerebral hemispheres, resolution of penumbra, normalization of the mean transit time, and improvement in Montreal Cognitive Assessment (MoCA) score (ΔMoCA = 9.80 points; P = 0.004).

Conclusions

Type A and B occlusions benefit from ET, especially in the presence of a large penumbra. Type C occlusions can benefit from HS. Unfortunately, we did not identify an intervention to help patients with type D occlusions. A phase 2b randomized controlled trial is needed to confirm these findings.

Effects of blood pressure lowering in patients with acute ischemic stroke and carotid artery stenosis

BACKGROUND

The Scandinavian Candesartan Acute Stroke Trial (SCAST) showed no beneficial clinical effects of blood pressure lowering with the angiotensin receptor blocker candesartan in the acute phase of stroke. In the present analysis we wanted to see if the effects of blood pressure lowering are harmful in the subgroup of patients with carotid artery stenosis.

METHODS

SCAST was a randomized- and placebo-controlled, double-masked trial of 2029 patients with acute stroke and high systolic blood pressure (≥ 140 mmHg). Of 1733 patients with ischemic stroke 993 underwent carotid artery imaging, and the degree of stenosis was categorized as no/insignificant (0-49%, n = 806), moderate (50-69%, n = 97) or severe (≥ 70%, n = 90). The trial's two co-primary effect variables were the composite end-point of vascular death, stroke or myocardial infarction, and functional outcome at six-months, according to the modified Rankin Scale.

RESULTS

Among patients with moderate or severe carotid artery stenosis the vascular end-point occurred in 9 of 87 patients (10.3%) treated with candesartan and in 17 of 100 controls (17.0%), and there was no evidence of a different risk in patients with severe stenosis (adjusted hazard ratio 0.74, 95% confidence interval 0.28-1.96, P = 0.54). For functional outcome there was also no clear difference, although in patients with severe stenosis the risk of a poor outcome was somewhat higher than in any of the other groups (adjusted odds ratio 2.24, 95% confidence interval 0.71-7.09, P = 0.16). Progressive stroke also occurred more often in patients with carotid artery stenosis treated with candesartan (10 of 87 patients (11.5%) vs. 4 of 100 patients (4.0%)), with a trend towards an increased risk with increasing severity of stenosis (P-value for linear trend = 0.04).

CONCLUSIONS

There is no clear evidence that the effect of candesartan is qualitatively different in patients with carotid artery stenosis, but there are signals that patients with severe stenosis are at particularly high risk of stroke progression and poor functional outcome.

Resistant hypertension and target organ damage

Cardiovascular (CV) complications such as myocardial infarction, heart failure, stroke and renal failure are related to both the degree and the duration of blood pressure (BP) increase. Resistant hypertension (RH) is associated with a higher risk of CV complications and a higher prevalence of target organ damage (TOD). The relationship between CV disease and TOD can be bidirectional. Elevated BP in RH may cause CV structural and functional alterations, and the development or persistence of left ventricular hypertrophy, aortic stiffness, atherosclerotic plaques, microvascular disease and renal dysfunction, may render hypertension more difficult to control. Specifically, RH is related to several conditions, including obesity, sleep apnea, diabetes, metabolic syndrome and hyperaldosteronism, characterized by an overexpression of humoral and hormonal factors that are involved in the development and maintenance of TOD. Optimal therapeutic strategies, including pharmacological treatment and innovative invasive methodologies, have been shown to achieve adequate BP control and induce the regression of TOD, thereby potentially improving patient prognosis.

Stroke prevention in the high-risk patient

Strokes are increasing in number due to an ageing population and are largely preventable. In the highest risk patients, a 90% relative risk reduction for stroke is attainable by appropriately using all the measures proven to reduce stroke: smoking cessation, a Mediterranean diet, control of hypertension, anticoagulants or antiplatelet agents, lipid lowering drugs and appropriate carotid endarterectomy. Vitamin therapy to lower homocysteine and carotid stenting are additional measures that may yet prove beneficial. Diet, smoking cessation and appropriate carotid endarterectomy reduce stroke by more than do pharmacotherapies. Blood pressure control depends more on selecting appropriate therapy individualised for the patient, than on using any particular drug class. This review, therefore, places pharmacotherapy in perspective as part of, but not all of, stroke prevention.

New treatment options for hypertension during acute ischemic or hemorrhagic stroke

Widespread reluctance to treat hypertension during acute stroke is based on historical accounts of unfavorable outcomes of treatment that were badly done: therapies that cannot be controlled, such as sublingual nifedipine, oral or intramuscular antihypertensive drugs may drop blood pressure precipitously, leading to worsening of ischemia. Case fatality in stroke obeys a U-shaped relationship: blood pressures that are either too low or too high are associated with worse outcomes both in ischemic stroke and in intracerebral hemorrhage. Very high blood pressures should be lowered in acute stroke, and there are some circumstances in which high blood pressure must be treated despite the presence of stroke. To avoid worsening of ischemia by reduction in cerebral blood flow, it is necessary to treat high blood pressure in acute stroke with drugs that can be controlled; this usually means giving drugs by intravenous infusion; however, there is recent evidence that transdermal administration of nitrates, which can be removed if pressure is too low, is a convenient alternative that does not reduce cerebral blood flow in acute stroke.

Clinical characteristics of resistant hypertension: the importance of compliance and the role of diagnostic evaluation in delineating pathogenesis

Resistant hypertension is defined as failure to achieve goal blood pressure despite adherence to 3 different antihypertensive medications, one of which must be a diuretic. True resistant hypertension must be distinguished by apparent resistant hypertension, of which an important cause is medication nonadherence, which can be recognized through a variety of monitoring strategies and may be improved through better patient education. A thorough history and examination should focus on evaluating for associated factors such as medication and illicit drug use, alcoholism, obesity, and obstructive sleep apnea. Further evaluation to differentiate apparent resistant hypertension from true resistant hypertension should include consideration of ambulatory blood pressure monitoring to rule out white coat hypertension. Routine laboratory work will reveal chronic kidney disease, which is the most common associated factor in resistant hypertension. Secondary or identifiable causes of resistant hypertension include primary aldosteronism, renovascular disease, and pheochromocytoma. Diagnostic evaluation for identifiable causes should be tailored for each patient and guided by signs and symptoms, as well as risks and benefits.

Effective Stroke Prevention in Patients with Symptomatic Carotid Stenosis

Patients with recently symptomatic carotid stenosis require effective medical treatment, and some require surgical removal of the carotid plaque. Randomized controlled trials have shown that endarterectomy reduces the overall risk of stroke in patients with severe carotid stenosis and, to a lesser extent, in patients with moderate stenosis. However, operating on all patients is not necessarily the most effective approach. The effectiveness of endarterectomy could be improved by selecting patients more rigorously. To do this, we first need to use data from existing randomized controlled trials to precisely determine the overall effect of surgery for different degrees of stenosis, identify subgroups in which benefit is increased, and use risk modeling to identify individuals at particularly high risk of stroke without surgery. Such an approach will also be useful in targeting angioplasty and stenting in patients in whom endarterectomy is not possible.

Relationship Between Blood Pressure and Stroke Risk in Patients With Symptomatic Carotid Occlusive Disease

Background and Purpose— Blood pressure lowering in patients with a previous transient ischemic attack (TIA) or stroke reduces the risk of recurrent stroke and coronary vascular events. However, there is uncertainty about the risks and benefits in patients with severe carotid occlusive disease, particularly those with a carotid occlusion or bilateral ≥70% carotid stenosis in whom cerebral perfusion is often impaired and may depend directly on systemic blood pressure. Therefore, we studied the effect of carotid artery disease on the relationship between blood pressure and stroke risk in patients with recent TIA or stroke.

Methods— We compared the relationship between blood pressure (systolic and diastolic blood pressures, pulse pressure) and stroke risk in TIA and stroke patients with documented stenosis of at least 1 carotid artery [European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET)] with that in TIA and stroke patients with a low prevalence of carotid disease [United Kingdom Transient Ischaemic Attack (UK-TIA) Aspirin Trial]. In ECST and NASCET, we also determined the relationship between blood pressure and stroke risk in patients with unilateral carotid occlusion and patients with bilateral ≥70% carotid stenosis.

Results— Stroke risk on medical treatment increased with blood pressure in ECST and NASCET, but the relationships were less steep than in the UK-TIA trial. The relationship between blood pressure and stroke risk was not affected by the presence of a unilateral carotid occlusion but was significantly affected by the presence of bilateral carotid stenosis ≥70% (interaction: systolic blood pressure, P =0.002; diastolic blood pressure, P =0.03; pulse pressure, P =0.003). In this group, the relationship was inverted because of the high stroke risks at lower blood pressures. This interaction was not present after carotid endarterectomy and was not present for the risk of myocardial infarction.

Conclusions— The risk of stroke increases with blood pressure in the great majority of patients with symptomatic carotid artery disease, but the relationship is less steep than in other patients with TIA or stroke. The relationship is unaffected by unilateral carotid occlusion alone but is inverted in patients with bilateral ≥70% carotid stenosis, suggesting that aggressive blood pressure lowering may not be advisable in this group. These patients represent only a few percent of all patients with TIA or stroke but have a high risk of recurrent stroke.

Treatment options for renovascular hypertension

Renovascular hypertension is usually caused by atherosclerotic narrowing of the origin of the renal artery and is much more common than is thought among patients with peripheral vascular disease, carotid stenosis or heart failure. Renovascular hypertension must be distinguished from renal artery stenosis. In true renovascular hypertension, the kidney takes charge of the blood pressure and will do what it takes to push blood pressure high enough to force blood through the blocked artery. This can be diagnosed with functional tests that measure glomerular filtration rate before and after blockade of the renin-angiotensin system with angiotensin converting enzyme inhibitors or antagonists of the AT(1) subtype of the angiotensin receptor. There is insufficient data on which to make evidence-based recommendations on the management of renovascular hypertension. Only two randomised trials exist of angioplasty versus medical therapy and of these the larger was severely contaminated by angioplasty among the group initially assigned to medical therapy. Only one trial exists of angiotensin converting enzyme inhibition versus alternative medical therapy. The drugs that are most effective in medical management of renovascular hypertension--angiotensin converting enzyme inhibitors and angiotensin receptor-1 blockers--tend to be avoided because of fear of a very rare complication (acute renal failure in patients with severe stenosis of both renal arteries, or the artery to a single remaining kidney). This fear is misplaced not only because it is rare (< 5% of patients with renovascular hypertension) but because it is reversible and treatable by revascularisation. Patients with renovascular hypertension should be evaluated by nuclear medicine differential glomerular filtration rate, enhanced by blockers of the renin-angiotensin system. If medical therapy is ineffective or causes severe impairment of renal function, revascularisation is required. Some experts favour surgical revascularisation because of occasional angioplasty failure and the risk of deterioration of renal function after angioplasty.