Novel Antihypertensive Therapies: Renal Sympathetic Nerve Ablation and Carotid Baroreceptor Stimulation

The efficacy of antihypertensive drugs in chronic intermittent hypoxia conditions

Sleep apnea/hypopnea disorders include centrally originated diseases and obstructive sleep apnea (OSA). This last condition is renowned as a frequent secondary cause of hypertension (HT). The mechanisms involved in the pathogenesis of HT can be summarized in relation to two main pathways: sympathetic nervous system stimulation mediated mainly by activation of carotid body (CB) chemoreflexes and/or asphyxia, and, by no means the least important, the systemic effects of chronic intermittent hypoxia (CIH). The use of animal models has revealed that CIH is the critical stimulus underlying sympathetic activity and hypertension, and that this effect requires the presence of functional arterial chemoreceptors, which are hyperactive in CIH. These models of CIH mimic the HT observed in humans and allow the study of CIH independently without the mechanical obstruction component. The effect of continuous positive airway pressure (CPAP), the gold standard treatment for OSA patients, to reduce blood pressure seems to be modest and concomitant antihypertensive therapy is still required. We focus this review on the efficacy of pharmacological interventions to revert HT associated with CIH conditions in both animal models and humans. First, we explore the experimental animal models, developed to mimic HT related to CIH, which have been used to investigate the effect of antihypertensive drugs (AHDs). Second, we review what is known about drug efficacy to reverse HT induced by CIH in animals. Moreover, findings in humans with OSA are cited to demonstrate the lack of strong evidence for the establishment of a first-line antihypertensive regimen for these patients. Indeed, specific therapeutic guidelines for the pharmacological treatment of HT in these patients are still lacking. Finally, we discuss the future perspectives concerning the non-pharmacological and pharmacological management of this particular type of HT.

Neuroadrenergic disarray in pseudo-resistant and resistant hypertension

Several studies have investigated the behavior of sympathetic cardiovascular drive in essential hypertension, providing conclusive evidence of the adrenergic activation characterizing this condition. These studies have also shown the importance of neuroadrenergic overdrive in the development and progression of the hypertensive state as well as in the pathogenesis of hypertension-related end-organ damage. The information available on the sympathetic nervous system's behavior in 'pseudo-resistant' and 'true resistant' hypertension is much more scarce. This paper will review the available knowledge on this issue by examining the data collected via indirect and direct approaches to investigate adrenergic function in resistant hypertension as well as the effects of pharmacological and non-pharmacological interventions.

Heated water-based exercise training reduces 24-hour ambulatory blood pressure levels in resistant hypertensive patients: a randomized controlled trial (HEx trial)

BACKGROUND

Regular exercise is an effective intervention to decrease blood pressure (BP) in hypertension, but no data are available concerning the effects of heated water-based exercise (HEx). This study examines the effects of HEx on BP in resistant hypertensive patients.

METHODS

This is a parallel, randomized controlled trial. 125 nonconsecutive sedentary patients with resistant hypertension from a hypertension outpatient clinic in a university hospital were screened; 32 patients fulfilled the study requirements. The training was performed for 60-minute sessions in a heated pool (32°C), three times a week for 12 weeks. The HEx protocol consisted of callisthenic exercises and walking inside the pool. The control group was asked to maintain habitual activities. The main outcome measure was change in mean 24-hour ambulatory BP (ABPM).

RESULTS

32 patients (HEx n=16; control n=16) were randomized; none were lost to follow-up. Office BPs decreased significantly after heated water exercise (36/12 mmHg). HEx decreased 24-hour systolic (from 137±23 to 120±12 mmHg, p=0.001) and diastolic BPs (from 81±13 to 72±10 mmHg, p=0.009); daytime systolic (from 141±24 to 120±13 mmHg, p<0.0001) and diastolic BPs (from 84±14 to 73±11 mmHg, p=0.003); and nighttime systolic (from 129±22 to 114±12 mmHg, p=0.006) and diastolic BPs (from 74±11 to 66±10 mmHg, p<0.0001). The control group after 12 weeks significantly increased in 24-hour systolic and diastolic BPs, and daytime and nighttime diastolic BPs.

CONCLUSION

HEx reduced office BPs and 24-hour ABPM levels in resistant hypertensive patients. These effects suggest that HEx may be a potential new therapeutic approach in these patients.