Headache response to glyceryl trinitrate in patients with and without obstructive coronary artery disease

Amplification of glyceryl trinitrate-induced headache features by noxious craniofacial stimuli in pain-free healthy humans

AIM

Glyceryl trinitrate (GTN) provokes an immediate migraine-like headache, followed by a delayed migraine attack in migraineurs. In healthy volunteers, only an immediate, less severe and shorter headache occurs. The presence of an already sensitized nervous system in migraineurs may underlie the more intense and prolonged GTN-evoked headaches. We tested if in healthy humans, application of noxious cutaneous and/or mechanical stimulation within craniofacial region would enhance or prolong GTN-evoked headache.

MATERIALS & METHODS

Noxious stimuli with a capsaicin patch on forehead, a mechanical headband, or both were applied prior to sublingual GTN (0.5 mg) in 20 healthy volunteers. GTN-induced headache characteristics and sensory responsiveness were recorded.

RESULTS

A more intense GTN-evoked headache was produced following application of headband.

CONCLUSION

Noxious mechanical stimulation prior to GTN resulted in a more intense GTN-evoked headache.

Effects of dietary nitrate supplementation on the response to extremity cooling and endothelial function in individuals with cold sensitivity. A double blind, placebo controlled, crossover, randomised control trial

Individuals with cold sensitivity have low peripheral skin blood flow and skin temperature possibly due to reduced nitric oxide (NO•) bioavailability. Beetroot has a high concentration of inorganic nitrate and may increase NO-mediated vasodilation. Using a placebo-controlled, double blind, randomised, crossover design, this study tested the hypotheses that acute beetroot supplementation would increase the rate of cutaneous rewarming following a local cold challenge and augment endothelium-dependent vasodilation in cold sensitive individuals. Thirteen cold sensitive participants completed foot and hand cooling (separately, in 15 °C water for 2 min) with spontaneous rewarming in 30 °C air whilst skin temperature and cutaneous vascular conductance (CVC) were measured (Baseline). On two further separate visits, participants consumed 140 ml of either concentrated beetroot juice (nitrate supplementation) or nitrate-depleted beetroot juice (Placebo) 90 min before resting seated blood pressure was measured. Endothelial function was assessed by measuring CVC at the forearm, finger and foot during iontophoresis of 1% w/v acetylcholine followed by foot and hand cooling as for Baseline. Plasma nitrite concentrations significantly increased in nitrate supplementation compared to Placebo and Baseline (502 ± 246 nmol L^-1; 73 ± 45 nmol L^-1; 74 ± 49 nmol L^-1 respectively; n = 11; P < 0.001). Resting blood pressure and the response to foot and hand cooling did not differ between conditions (all P > 0.05). Nitrate supplementation did not alter endothelial function in the forearm, finger or foot (all P > 0.05) compared to Placebo. Despite a physiologically meaningful rise in plasma nitrite concentrations, acute nitrate supplementation does not alter extremity rewarming, endothelial function or blood pressure in individuals with cold sensitivity.

Novel contrast-injection protocol for high-resolution abdominal CT-angiography: vascular visualization improvement with vasodilator

PURPOSE

To evaluate the usefulness of a novel contrast-injection protocol for high-resolution abdominal computed tomography angiography (CTA) using nitroglycerin (NTG).

METHODS

Abdominal CTA was performed in 80 patients using two 64-detector-row CT scanners. Forty patients were examined after administration of sublingual NTG (NTG group), while 40 were examined without NTG administration (non-NTG group). Arterial phase images were acquired with maximum intensity projection and volume rendering. Reduction rates: vessel cross-sectional areas ratio of 10 cm distal to origin at the superior mesenteric artery, contrast enhancements, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were assessed. Three reviewers evaluated degree of depiction of the peripancreatic vasculature using a four-point scale (1 = poor, 4 = excellent).

RESULTS

Reduction rates were significantly lower in the NTG group (P < 0.001), while there were no significant differences in contrast enhancements, SNR, or CNR between groups. Visual evaluation results of the NTG group were significantly better than those of the non-NTG group (P < 0.01).

CONCLUSION

Abdominal CTA using NTG improved visualization of the abdominal peripheral vessels. This improved arterial view may be beneficial for preoperative evaluation of the arterial anatomy.

The Role of Adenosine Signaling in Headache: A Review

Migraine is the third most prevalent disease on the planet, yet our understanding of its mechanisms and pathophysiology is surprisingly incomplete. Recent studies have built upon decades of evidence that adenosine, a purine nucleoside that can act as a neuromodulator, is involved in pain transmission and sensitization. Clinical evidence and rodent studies have suggested that adenosine signaling also plays a critical role in migraine headache. This is further supported by the widespread use of caffeine, an adenosine receptor antagonist, in several headache treatments. In this review, we highlight evidence that supports the involvement of adenosine signaling in different forms of headache, headache triggers, and basic headache physiology. This evidence supports adenosine A_2A receptors as a critical adenosine receptor subtype involved in headache pain. Adenosine A_2A receptor signaling may contribute to headache via the modulation of intracellular Cyclic adenosine monophosphate (cAMP) production or 5' AMP-activated protein kinase (AMPK) activity in neurons and glia to affect glutamatergic synaptic transmission within the brainstem. This evidence supports the further study of adenosine signaling in headache and potentially illuminates it as a novel therapeutic target for migraine.

Relationship between Nitrate-Induced Headache and Coronary Artery Lesion Complexity

OBJECTIVE

The aim of the present study was to investigate the association between nitrate-induced headache (NIH) and the complexity of coronary artery lesions in patients with stable coronary artery disease (CAD).

SUBJECTS AND METHODS

Two hundred and seventy-five patients with anginal chest pain who underwent coronary angiography were enrolled in the present study. NIH was defined as the presence of headache due to nitrate treatment (isosorbide mononitrate 40 mg) after excluding confounding factors. Coronary artery lesion complexity was assessed by the SYNTAX score (SXscore) using a dedicated computer software system.

RESULTS

The mean SXscore was lower in the patients with NIH than in patients without NIH (7.3 ± 5.2 vs. 14.4 ± 8.5, respectively; p < 0.001). Additionally, patients with NIH had a lower rate of multivessel disease compared with those without NIH (the mean number of diseased vessels was 1.5 ± 0.7 and 2.0 ± 07, respectively; p < 0.001). In multivariate analysis, increasing age (p = 0.02) and headache (p = 0.001) were found to be independent determinants of SXscore.

CONCLUSION

The present study demonstrated an independent inverse association between NIH and SXscore. The NIH could provide important predictive information about coronary artery lesion complexity in patients with stable CAD.

Headache-type adverse effects of NO donors: vasodilation and beyond

Although nitrate therapy, used in the treatment of cardiovascular disorders, is frequently associated with side-effects, mainly headaches, the summaries of product characteristics of nitrate-containing medicines do not report detailed description of headaches and even do not highlight the possibility of nitrate-induced migraine. Two different types of nitrate-induced headaches have been described: (i) immediate headaches that develop within the first hour of the application, are mild or medium severity without characteristic symptoms for migraine, and ease spontaneously; and (ii) delayed, moderate or severe migraine-type headaches (occurring mainly in subjects with personal or family history of migraine), that develop 3-6 h after the intake of nitrates, with debilitating, long-lasting symptoms including nausea, vomiting, photo- and/or phono-phobia. These two types of headaches are remarkably different, not only in their timing and symptoms, but also in the persons who are at risk. Recent studies provide evidence that the two headache types are caused by different mechanisms: immediate headaches are connected to vasodilation caused by nitric oxide (NO) release, while migraines are triggered by other actions such as the release of calcitonin gene-related peptide or glutamate, or changes in ion channel function mediated by cyclic guanosine monophosphate or S-nitrosylation. Migraines usually need anti-attack medication, such as triptans, but these drugs are contraindicated in most medical conditions that are treated using nitrates. In conclusion, these data recommend the correction of summaries of nitrate product characteristics, and also suggest a need to develop new types of anti-migraine drugs, effective in migraine attacks, that could be used in patients with risk for angina pectoris.

Side effects of using nitrates to treat angina

Nitrates are very effective antianginal and anti-ischaemic agents. Provision of a long nitrate-free interval or low plasma nitrate levels prior to the morning dose prevents the loss of clinical efficacy by preventing the development of tolerance. However, side effects during nitrate therapy are common. Headache is the most common side effect of nitrates; often dose-related and reported by up to 82% of patients in placebo-controlled trials. Nearly 10% of patients are unable to tolerate nitrates due to disabling headaches or dizziness. In others, headaches are mild-to-moderate in severity and either resolve or diminish in intensity with continued nitrate therapy. Nitrate-induced hypotension is common, but often asymptomatic. In rare instances, nitrate-induced hypotension is severe and accompanied by marked slowing of the heart rate and syncope. Use of nitrates in patients who experience syncope after administration of nitrates is contraindicated. Nitrates rarely cause coronary steal and myocardial ischaemia. Nitrate rebound may occur and patients may experience nocturnal anginal episodes during intermittent therapy with nitroglycerin patches. Administration of nitrates is contraindicated with concomitant use of phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction, as combination therapy may lead to profound hypotension and even death. There are disturbing observational reports in the literature that continuous, prolonged use of nitrates may lead to increased mortality and recurrent myocardial infarctions. Large, randomised, placebo-controlled studies are needed to confirm or refute these reports; until then, the use of nitrates to treat angina is here to stay.