Chest pain as a consequence of abnormal visceral nociception

What Is the Future of Impedance Planimetry in Gastroenterology?

The gastrointestinal (GI) tract is efficient in transporting ingested material to the site of delivery in healthy subjects. A fine balance exists between peristaltic forces, the mixing and delivery of the contents, and sensory signaling. This fine balance is easily disturbed by diseases. It is mandatory to understand the pathophysiology to enhance our understanding of GI disorders. The inaccessibility and complex nervous innervation, geometry and mechanical function of the GI tract make mechanosensory evaluation difficult. Impedance planimetry is a distension technology that assesses luminal geometry, mechanical properties including muscle dynamics, and processing of nociceptive signals from the GI tract. Since standardized models do not exist for GI muscle function in vivo, models, concepts, and terminology must be borrowed from other medical fields such as cardiac mechanophysiology. The review highlights the impedance planimetric technology, muscle dynamics assessment, and 3 applied technologies of impedance planimetry. These technologies are the multimodal probes that assesses sensory function, the functional luminal imaging probe that dynamically measures the geometry of the lumen it distends, and Fecobionics that is a simulated feces providing high-resolution measurements during defecation. The advanced muscle analysis and 3 applied technologies can enhance the quality of future interdisciplinary research for gaining more knowledge about mechanical function, sensory-motor disorders, and symptoms. This is a step in the direction of individualized treatment for GI disorders based on diagnostic subtyping. There seems to be no better alternatives to impedance planimetry, but only the functional luminal imaging probe is currently commercially available. Wider use depends on commercialization of the multimodal probe and Fecobionics.

Barostat or dynamic balloon distention test: which technique is best suited for esophageal sensory testing?

Esophageal sensation is commonly assessed by barostat-assisted balloon distension (BBD) or dynamic balloon distension (DBD) technique, but their relative merits are unknown. Our aim was to compare the usefulness and tolerability of both techniques. Sixteen healthy volunteers (male/female = 6/10) randomly underwent graded esophageal balloon distensions, using either BBD (n= 8) or DBD (n= 8). BBD was performed by placing a 5-cm long highly compliant balloon attached to a barostat, and DBD by placing a 5-cm long balloon attached to a leveling container. Intermittent phasic balloon distensions were performed in increments of 6 mm Hg. Sensory thresholds and biomechanical properties were assessed and compared. Sensory thresholds for first perception (mean ± standard deviation; 21 ± 6 vs. 21.2 ± 5, mm Hg, P= 0.9), discomfort (38 ± 8 vs. 35 ± 9, P= 0.5), and pain (44 ± 4 vs. 45 ± 3, P= 0.7) were similar with BBD and DBD techniques. However, more subjects tolerated DBD (7/8, 88%) when compared with BBD (4/8, 50%). Forceful expulsion of balloon into stomach (n= 4), pulling around the mouth (n= 4), chest discomfort (n= 2) and retching (n= 2) were overlapping reasons for intolerance with BBD. Esophageal wall distensibility was similar with both techniques. Both techniques provided comparable data on biomechanical properties. However, DBD was better tolerated than BBD for evaluation of esophageal sensation. Hence, we recommend DBD for performing esophageal balloon distension test.

Noncardiac chest pain: epidemiology, natural course and pathogenesis

Noncardiac chest pain is defined as recurrent chest pain that is indistinguishable from ischemic heart pain after a reasonable workup has excluded a cardiac cause. Noncardiac chest pain is a prevalent disorder resulting in high healthcare utilization and significant work absenteeism. However, despite its chronic nature, noncardiac chest pain has no impact on patients' mortality. The main underlying mechanisms include gastroesophageal reflux, esophageal dysmotility and esophageal hypersensitivity. Gastroesophageal reflux disease is likely the most common cause of noncardiac chest pain. Esophageal dysmotility affects only the minority of noncardiac chest pain patients. Esophageal hypersensitivity may be present in non-GERD-related noncardiac chest pain patients regardless if esophageal dysmotility is present or absent. Psychological co-morbidities such as panic disorder, anxiety, and depression are also common in noncardiac chest pain patients and often modulate patients' perception of disease severity.

The hypersensitive esophagus: pathophysiology, evaluation, and treatment options

Visceral hypersensitivity plays a key role in the pathogenesis of esophageal functional disorders such as functional heartburn and chest pain of presumed esophageal origin (noncardiac chest pain). About 80% of patients with unexplained noncardiac chest pain exhibit lower esophageal sensory thresholds when compared to controls during esophageal sensory testing (ie, esophageal barostat, impedance planimetry). Such information has led to prescription of peripherally and/or centrally acting therapies for the management of these patients. This review summarizes and highlights recent and significant findings regarding the pathophysiology, evaluation, and treatment of the hypersensitive esophagus, a central factor in functional esophageal disorders.

Theophylline improves esophageal chest pain--a randomized, placebo-controlled study

BACKGROUND/AIM

The treatment of esophageal (noncardiac) chest pain is unsatisfactory and there is no approved therapy. A previous uncontrolled study suggested that theophylline may be useful. Our aims were to investigate the effects of theophylline on esophageal sensorimotor function and chest pain.

METHODS

In a double-blind study, sensory and biomechanical properties of the esophagus were assessed using impedance planimetry in 16 patients with esophageal hypersensitivity, after intravenous theophylline or placebo. In a second, randomized 4-wk crossover study, oral theophylline and placebo were administered to 24 patients with esophageal hypersensitivity. Frequency, intensity, and duration of chest pain episodes were evaluated.

RESULTS

After IV theophylline, chest pain thresholds (P=0.027) and esophageal cross-sectional area (P=0.03) increased and the esophageal wall became more distensible (P=0.04) compared with placebo. After oral theophylline, the number of painful days (P=0.03) and chest pain episodes (P=0.025), pain duration (P=0.002), and its severity (P=0.031) decreased. Overall symptoms improved in 58% on theophylline and 6% on placebo (P<0.02). There was no order effect.

CONCLUSIONS

Theophylline relaxed the esophageal wall, decreased hypersensitivity, and improved chest pain. Theophylline is effective in the treatment of functional chest pain.

Central sensitization in patients with non-cardiac chest pain: a clinical experimental study

OBJECTIVE

Patients with non-cardiac chest pain (NNCP) suffer from unexplained and often intractable pain which can pose a major clinical problem. The aim of this study was to investigate nociceptive processing in NNCP patients and their response to experimentally acid-induced oesophageal hyperalgesia using a multimodal stimulation protocol.

MATERIAL AND METHODS

Ten highly selected patients with NCCP (mean age 43 years, 1 M) were compared with an age- and gender-matched group of 20 healthy subjects. After preconditioning, the distal oesophagus was painfully distended with a balloon using "impedance planimetry". This method assesses the luminal cross-sectional area of the oesophagus based on the electrical impedance of the fluid inside the balloon. The baseline distensions were done before and after pharmacological relaxation of the smooth muscle with 20 mg butylscopolamine. After baseline distensions, a series of up to 10 mechanical stimuli was performed (temporal summation). The stimulations were repeated after sensitization of the oesophagus induced by acid perfusion. The sensory intensities were assessed during the stimulations and the referred pain area was mapped.

RESULTS

At baseline distensions, no differences were seen between patients and controls before and after relaxation of the smooth muscles. The patients tolerated fewer repeated distensions than controls (4.8+/-0.5 versus 9.1+/-0.9; p=0.04) and had an increased size of the referred pain areas to the mechanical stimulations (32.9+/-6.2 versus 64.9+/-18.3 cm2; p=0.01). After sensitization with acid, the patients developed hyperalgesia (p<0.001), whereas no significant changes were seen in controls.

CONCLUSIONS

NCCP patients showed facilitated central pain mechanisms (temporal summation and visceral hyperalgesia after sensitization). This could be used in the diagnosis and understanding of the symptoms in these patients.

Experimental human pain models in gastro-esophageal reflux disease and unexplained chest pain

Methods related to experimental human pain research aim at activating different nociceptors, evoke pain from different organs and activate specific pathways and mechanisms. The different possibilities for using mechanical, electrical, thermal and chemical methods in visceral pain research are discussed with emphasis of combinations (e.g., the multimodal approach). The methods have been used widely in assessment of pain mechanisms in the esophagus and have contributed to our understanding of the symptoms reported in these patients. Hence abnormal activation and plastic changes of central pain pathways seem to play a major role in the symptoms in some patients with gastro-esophageal reflux disease and in patients with functional chest pain of esophageal origin. These findings may lead to an alternative approach for treatment in patients that does not respond to conventional medical or surgical therapy.

Day-to-day variability in acid reflux patterns using the BRAVO pH monitoring system

BACKGROUND & GOALS

The wireless pH monitoring system such as the BRAVO pH system is a significant advancement in the evaluation of patients with gastroesophageal reflux because of its potentially better tolerability and the ability to record data over a 48-hour period. The aim of our study was to evaluate safety, performance, tolerability, and day-to-day variability in acid reflux patterns using the BRAVO pH system.

METHODS

A total of 90 consecutive patients (48 men and 42 women) with persistent reflux symptoms underwent BRAVO pH capsule placement from October 2002 to August 2003 at a tertiary care hospital. The BRAVO pH capsule was deployed 6 cm proximal to the squamocolumnar junction under endoscopic guidance. The pH recordings over 48 hours were obtained after uploading data to a computer from the pager-like device that recorded pH signals from the BRAVO pH capsule.

RESULTS

Successful pH data over 48 hours was obtained in 90% of patients. Nearly two thirds of patients experienced a variety of symptoms ranging from a foreign body sensation to chest discomfort or pain. Four patients had severe chest pain, 3 of whom required endoscopic removal of the BRAVO pH capsule. In 74.4% of patients, number of reflux events as well as time (%) pH<4 correlated from the first 24-hour period to the second 24-hour period. However, in 28% of patients, no predictable pattern of (%) time pH<4 in the supine position was reproduced from one 24-hour period to the next 24-hour period.

CONCLUSIONS

The BRAVO pH system appears a safe and effective method of recording esophageal acid exposure. It is an acceptable alternative for patients who are unwilling or unable to tolerate nasopharyngeal catheter-based pH studies, and it has a potential advantage of the 2-day recording period.

A prospective study of gastric acid analysis and esophageal acid exposure in patients with gastroesophageal reflux refractory to medical therapy

A number of factors have been proposed to account for the lack of response to medical therapy in patients with gastroesophageal reflux; however, no controlled studies are available in the literature. The goal of this study was to determine possible causes of medical refractoriness in patients with gastroesophageal reflux. Gastric acid output and esophageal acid exposure were measured in patients who continue to have reflux symptoms despite aggressive antisecretory therapy. In addition, an upper endoscopy was also performed in each patient. Patients with a drug-controlled acid output < 1 mEq/hr and a supine total esophageal pH < 4 for less than 1.7% of the time measured were considered responsive to therapy; on the other hand, those with a drug-controlled gastric acid output > 1 mEq/hr and a supine esophageal pH < 4 for more than 1.7% of the time measured were considered resistant to therapy. Twenty-four patients met the inclusion criteria (13 male and 11 female; mean age, 52). Drug-controlled gastric acid output was more than 1 mEq/hr in 25% of patients and less than 1 mEq/hr in the remainder. Of those patients with a gastric acid output of less than 1 mEq/hr (18 patients), 8(44%) had a supine esophageal pH < 4 for more than 1.7% of the time, suggesting that factors other than gastroesophageal reflux likely contributed to their reflux-like symptoms. Acid suppression appears adequate in the majority of patients with gastroesophageal reflux refractory to medical therapy. The exact cause of persistent reflux-like symptoms in patients who fail medical treatment is uncertain but may be related to non-acid-related factors such as esophageal hypersensitivity to physiologic reflux, increased intake of air resulting in aerophagia, or other factors such as bile reflux.

Functional chest pain: nociception and visceral hyperalgesia

Functional chest pain is a common, yet poorly understood entity. The focus of this review is to explore the evolving research and clinical approaches with a particular emphasis on the sensory or afferent neuronal dysfunction of the esophagus as a key player in the manifestation of this pain syndrome. Although once regarded as a psychologic or esophageal motility disorder, recent advances have shown that many of these patients have visceral hyperalgesia. Whether visceral hypersensitivity is a central or peripheral perturbation of the gut-brain axis remains debatable. Response to empirical therapy with high-dose proton pump inhibitors, upper endoscopy, or prolonged recording of esophageal pH may identify gastroesophageal reflux disease as a source of chest pain. Esophageal balloon distension study can serve as a useful test for identifying hypersensitivity. Newer techniques, including functional magnetic resonance imaging, magnetoencephalogram, and cortical evoked potentials, are being investigated. High doses of proton pump inhibitors and low doses of tricyclic antidepressants or trazadone remain the mainstay of therapy, although several new approaches including theophylline have been shown to be beneficial.

Sex-based differences in gastrointestinal pain

Recent interest has focused on sex-related differences in irritable bowel syndrome (IBS) physiology and treatment responsiveness to novel pharmacologic therapies. Similar to a variety of other chronic pain conditions and certain affective disorders, IBS is more prevalent amongst women, both in population-based studies as well as in clinic-based surveys. Non-painful gastrointestinal symptoms, constipation and somatic discomfort are more commonly reported by female IBS patients. While perceptual differences to rectosigmoid stimulation are only observed following repeated noxious stimulation of the gut, sex-related differences in certain sympathetic nervous system (SNS) responses to rectosigmoid stimulation are consistently seen. Consistent with experimental findings in animals, current evidence is consistent with a pathophysiological model which emphasizes sex-related differences in autonomic and antinociceptive responses to certain visceral stimuli.

Effect of pantoprazole on the course of reflux-associated laryngitis: a placebo-controlled double-blind crossover study

BACKGROUND

The optimal management of patients with reflux-associated laryngitis is unclear. We performed a placebo-controlled crossover trial in patients with proven reflux disease and associated laryngitis to determine the effect of pantoprazole and to gain information on the natural course of the disease.

METHODS

Sixty-two consecutive non-smoking patients with hoarseness and proven laryngitis were examined. Scores with respect to the larynx and for subjective complaints were determined and 24-h pH-metry to assess acid reflux in the lower oesophagus and pharynx was performed. Patients with pathologic reflux were given the chance to enter a double-blinded randomized crossover trial with pantoprazole 40 mg b.i.d. and placebo for a duration of 3 months each, separated by a 2-week washout period.

RESULTS

Twenty-four of 62 patients showed pathological reflux; 21 patients were included in the study and 14 concluded all parts of the study. Both pantoprazole and placebo resulted in a marked improvement in laryngitis scores (decrease of 8.0 +/- 1.4 versus 5.6 +/- 2.6; no significant difference between the 2 treatments) and symptoms after the first 3 months (decrease of oesophageal symptom score of 2.2 +/- 1.4 versus 5.4 +/- 2.8; decrease of laryngeal scores of 8.3 +/- 3.6 versus 10.3 +/- 3.9; also no significant difference between the 2 treatments). A second pH-metry 2 weeks thereafter proved the persistence of reflux in most of these patients. Switching to pantoprazole led to a further improvement of scores. In the group switched to placebo there was recurrence only in a minority of patients.

CONCLUSIONS

The self-limited nature of reflux-associated laryngitis in non-smokers is largely underestimated. Laryngitis improves despite the persistence of reflux. Pantoprazole may be helpful especially in relieving acute symptoms, but the advantage of long-term treatment over placebo has been greatly overestimated.

Afferent vagal modulation. Clinical studies of visceral sensory input

The frequency composition of a continuous time series of R-R intervals may be viewed as the phasic output of a central processing system intimately dependent on sensory input from a variety of afferent sources. While different measures of heart rate variability permit a glimpse into the autonomic efferent limb of this complex system, direct access of afferent fibers in humans has remained elusive. Using a specially designed esophageal catheter/manometer probe, we have been able to gain access to vagal afferent fibers in the distal esophagus. Our studies on the effect of vagal afferent electrostimulation on both cerebral evoked potentials (EvP) and the power spectrum of heart rate variability have yielded the following observations: 1. Stimulation of esophageal vagal afferents dramatically and reproducibly increases the high frequency (HF) vagal power and reduces the low frequency (LF) power of the heart rate autospectrum. 2. This effect is constant across stimulation frequencies from 0.1 to 1.0 Hz and across stimulation intensities from 2.5 to 20 mA. 3. Regardless of the stimulation parameters, there are only minimal changes in heart rate (2-6 bpm) and no change in respiratory frequency. 4. There is a linear correlation between electrical stimulation intensity and the amplitude of cerebral evoked potentials, whereas there is a non-linear relationship with all short-term power spectral indices. 5. While cerebral evoked potentials are only elicited at stimulation intensities above perception threshold, there is already a significant shift to increased vagal efferent modulation well below perception threshold.

CONCLUSION

These studies support the concept that power spectral indices of heart rate variability represent phasic output responses to tonic afferent viscerosensory signals in humans. These studies also demonstrate the feasibility of accessing vagal afferents in humans.

Cardioesophageal reflexes: an invasive human study

Neural reflex arcs from the esophagus and heart have been shown in both animals and man. The purpose of this study was to further investigate these pathways in individuals undergoing cardiac catheterization. A total of 298 patients undergoing cardiac catheterization were asked to participate in the protocol. Thirty patients were able to complete the study. Esophageal manometry and pH were monitored throughout the cardiac procedure. Afterwards, esophageal provocation with ice water, hydrochloric acid, and balloon inflation was performed with observation of cardiac rate and rhythm. Twelve patients with normal coronary arteries developed diffuse esophageal spasm on either esophageal or cardiac provocation. In one patient with abnormal coronary arteries, coronary angioplasty precipitated diffuse esophageal spasm. Esophageal acid sensitivity was increased in patients with normal coronaries as compared to those that were abnormal. The esophageal pain threshold was significantly lower in patients undergoing angioplasty versus those undergoing coronary angiography alone. There was no significant change in esophageal pH during invasive cardiac maneuvers and manipulations. In conclusion, cardiac manipulation can induce esophageal motility abnormalities, but not gastroesophageal reflux. Coronary angioplasty is associated with esophageal hyperalgesia.

Randomized trial of sertraline in patients with unexplained chest pain of noncardiac origin

BACKGROUND

Between 10% and 30% of patients with symptoms similar to angina and sufficient to justify cardiac catheterization are found to have normal coronary angiograms. Treatment of patients with chest pain with no apparent cardiac cause is a major clinical problem. Our hypothesis was that sertraline would reduce the severity of pain in patients with chest pain of noncardiac origin.

METHODS AND RESULTS

This was a single-site, double-blind, placebo-controlled study of the efficacy, tolerability, and safety of sertraline in the treatment of noncardiac chest pain in outpatients. Thirty patients were enrolled in the study. After 1 week of single-blind placebo washout, patients were randomly assigned in a double-blind fashion either to drug or placebo. The Beck Depression Inventory was administered at baseline and at completion of study. Daily pain diaries (visual analogue scale, rating pain on a scale of 1 to 10) were selfadministered and evaluated at baseline and at follow-up visits. Statistical measures were performed with an intention-to-treat approach. Patients who received sertraline over the course of the study showed a statistically significant reduction in pain compared with those who were receiving placebo.

CONCLUSIONS

The use of sertraline in patients with noncardiac chest pain produced clinically significant reduction of daily pain. These results suggest the need for further studies of the efficacy and tolerability of sertraline and other selective serotonin reuptake inhibitors in the long-term management of noncardiac chest pain.

Emerging disease model for functional gastrointestinal disorders

In response to perceived or experienced change that is considered threatening to the individual, the central nervous system mounts a stereotypic response that decreases the sensitivity to pain, modulates the autonomic nervous system outflow, and activates the hypothalamic-pituitary-adrenal (HPA) axis. This response of the "emotional motor system" may or may not be associated with the conscious experience of feelings of fear or anxiety. Alterations in these response systems (either up- or downregulation) may produce symptoms, such as viscero-somatic hypersensitivity, altered bowel habits, or increased anxiety.

Effects of octreotide on esophageal visceral perception and cerebral evoked potentials induced by balloon distension

OBJECTIVE

Octreotide, a somatostatin analog, is antinociceptive and increases perception threshold in the rectum. The aim of this study was to determine whether octreotide alters esophageal sensory thresholds and cortical evoked potentials (CEPs) resulting from intraesophageal balloon distension.

METHODS

Twelve healthy volunteers (six men and six women, median age 25 yr, range 21-60 yr) underwent a randomized, double-blind, placebo-controlled trial of octreotide 100 microg s.c. versus saline. A 30-mm balloon was inserted 5 cm above the lower esophageal sphincter without topical anesthesia. The balloon was inflated at a rate of 170 cc/s to a maximum of 30 cc in 2 cc steps. Both pressure and volume were recorded. Patients reported first sensation (S1) and maximally tolerated pain (S2). Two cycles were performed both preinjection and 40 min postinjection. Evoked potentials were recorded from Cz to linked ears over 50 balloon inflation cycles (volume = S2).

RESULTS

Threshold volume to first sensation (S1) was significantly increased after octreotide injection [median (interquartile range): 24 (14-26) cc vs 13 (9-21) cc, p < 0.02]. No significant alteration in volume causing pain (S2) was noted after octreotide injection [29 (25-30+) cc vs 22 (19-29) cc]. Neither were volumes causing either first sensation [18 (11-24) cc vs 13 (9-18) cc] or pain [27 (23-30) cc vs 23 (21-25) cc] significantly altered by placebo injection. Neither amplitude nor latency of any of the three peaks of the evoked potential recordings differed significantly between postplacebo and postoctreotide recordings.

CONCLUSION

Octreotide significantly increased esophageal perception thresholds to balloon distension. It did not alter pain thresholds, nor were cortical evoked potentials to painful stimulation altered in normal subjects.

Sustained esophageal contraction: a marker of esophageal chest pain identified by intraluminal ultrasonography

BACKGROUND & AIMS

Intraluminal pressure recording systems have not demonstrated predictable esophageal motor correlates of unexplained chest pain. This study used continuous high-frequency intraluminal ultrasonography to characterize esophageal contraction at the time of spontaneous and provoked chest pain.

METHODS

Intraluminal pressure, pH, and ultrasound images of the esophagus were recorded for a maximum of 24 hours in 10 subjects with unexplained chest pain. Changes in esophageal muscle thickness were measured as a marker of muscle contraction. Ten additional subjects with suspected esophageal chest pain were studied after edrophonium chloride injection to provoke symptoms. Ten healthy subjects were studied as controls.

RESULTS

Eighteen of 24 spontaneous chest pain episodes were preceded by a sustained esophageal contraction (SEC) detected on ultrasonography (mean duration, 68.0 seconds). This motor pattern was not accompanied by changes in intraluminal pressure. Four of 24 asymptomatic control periods were accompanied by SEC, although these contractions were of shorter mean duration (29.0 seconds; P < 0.001). SEC was observed in 5 subjects with a positive chest pain response to edrophonium and in none of the 5 subjects with a negative response. SEC was not detected in normal subjects.

CONCLUSIONS

There is a strong temporal correlation between a previously unrecognized esophageal motor event, SEC, and both spontaneous and provoked esophageal chest pain.

Fedotozine blocks hypersensitive visceral pain in conscious rats: action at peripheral kappa-opioid receptors

The effect of fedotozine on visceral hypersensitivity was evaluated in conscious rats. One hour after colonic irritation (0.6% acetic acid intracolonically), a 30 mmHg colonic distension was applied for 10 min. Irritation increased the number of abdominal contractions induced by colonic distension (23.4 +/- 4.1 versus 4.8 +/- 1.4 in saline-treated rats, P < 0.001). Facilitation of colonic pain was reversed in a dose-dependent manner by fedotozine ((+)-(-1R1)-1-phenyl-1-[(3,4,5-trimethoxy)benzyloxymethyl]-N ,N-dimethyl-n-propylamine), (+/-)-U-50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N-(2-1-pyrrolidinyl]cyclohexyl)benzen eacetamide) and morphine (respective ED50 values 0.67, 0.51 and 0.23 mg/kg s.c.). The kappa-opioid receptor antagonist, nor-binaltorphimine, abolished the effects of fedotozine and (+/-)-U-50,488H but not those of morphine. Low doses of naloxone (30 microg/kg s.c.) blocked the effect of morphine but not of fedotozine or (+/-)-U-50,488H. After intracerebroventricular administration, morphine was very potent (ED50 1.7 microg/rat), (+/-)-U-50,488H poorly active (58% of antinociception at 300 microg/rat) and fedotozine inactive up to 300 microg/rat. These results show that fedotozine blocks hypersensitive visceral pain by acting on peripheral kappa-opioid receptors in animals.

Pain perception and brain evoked potentials in patients with angina despite normal coronary angiograms

OBJECTIVE

To evaluate the role of nociception in patients with angina despite normal coronary angiograms and to investigate whether any abnormality is confined to visceral or somatosensory perception.

METHODS

Perception, pain threshold, and brain evoked potentials to nociceptive electrical stimuli of the oesophageal mucosa and the sternal skin were investigated in 10 patients who had angina but normal coronary angiograms, no other signs of cardiac disease, and normal upper endoscopy. Controls were 10 healthy volunteers. The peaks of the evoked potential signal were designated N for negative deflections and P for positive. Numbers were given to the peaks in order of appearance after the stimulus. The peak to peak amplitudes (P1/N1, N1/P2) were measured in microV.

RESULTS

(1) Angina pectoris was provoked in seven patients following continuous oesophageal stimulation. (2) Distant projection of pain occurred after continuous electrical stimulation of the oesophagus in four patients and in no controls. (3) Patients had higher oesophageal pain thresholds (median 16.3 mA v 7.3 mA, P = 0.02) to repeated stimuli than controls, whereas the values did not differ with respect to the skin. There were no intergroup differences in thresholds to single stimuli. (4) Patients had substantially reduced brain evoked potential amplitudes after both single oesophageal (P1/N1, median values: 7.2 microV, controls: 29.0 microV; N1/P2: 16.5 microV, controls: 66.0 microV; P < 0.001 for both) and skin (N1/P2: 13.5 microV; controls: 76.0 microV; P < 0.001) stimuli despite the similar pain thresholds.

CONCLUSION

Central nervous system responses to visceral and somatosensory nociceptive input are altered in patients who have angina despite normal coronary angiograms.

Heightened visceral sensation in functional gastrointestinal disease is not site-specific. Evidence for a generalized disorder of gut sensitivity

Alteration in visceral sensation locally at the site of presumed symptom origin in the gastrointestinal tract has been proposed as an important etiopathological mechanism in the so-called functional bowel disorders. Patients presenting with one functional gastrointestinal syndrome, however, frequently have additional symptoms referable to other parts of the gut, suggesting that enhanced visceral nociception may be a panintestinal phenomenon. We measured the sensory thresholds for initial perception (IP), desire to defecate (DD), and urgency (U) in response to rectal balloon distension, and the thresholds for initial perception and for discomfort in response to esophageal balloon distension in 12 patients with irritable bowel syndrome (IBS) and 10 patients with functional dyspepsia (FD), in comparison with healthy controls. As expected, IBS patients exhibited lower rectal sensory thresholds than controls (P < 0.0001), but in addition had significantly lower sensory thresholds for both perception and discomfort evoked by balloon distension of the esophagus (mean +/- SEM: 8.8 +/- 1.3 ml vs 12.1 +/- 1.5 ml (P < 0.05) and 12.2 +/- 1.4 ml vs 16.4 +/- 1.4 ml (P < 0.02) respectively. Patients with FD showed similarly enhanced esophageal sensitivity, with thresholds for perception and discomfort of 8.1 +/- 0.9 ml (P < 0.02), and 10.1 +/- 1.0 ml (p < 0.001), respectively, but were also found to have sensory thresholds for rectal distension similar to those observed in the IBS group, significantly lower than in controls: IP 45.0 +/- 17.6 vs 59.3 +/- 1.5 ml (P < 0.001), DD 98.0 +/- 17.9 vs 298.7 +/- 9.0 ml (P < 0.0001), U 177.2 +/- 25.4 vs 415.1 +/- 12.6 ml (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Lowered oesophageal sensory thresholds in patients with symptomatic but not excess gastro-oesophageal reflux: evidence for a spectrum of visceral sensitivity in GORD

Some patients undergoing ambulatory oesophageal pH monitoring to investigate symptoms suggestive of gastro-oesophageal reflux disease (GORD) are found to have oesophageal acid exposure within the physiological range but show a close correlation between their symptoms and individual reflux episodes. It is suggested that these patients might exhibit enhanced oesophageal sensation, akin to the heightened perception of both physiological and provocative stimuli in the gut that has been described in patients with functional gastrointestinal disorders. This study tested the hypothesis by measuring the sensory thresholds for oesophageal balloon distension and discomfort in 20 patients with symptoms of GORD, in whom ambulatory pH monitoring had shown normal acid exposure times, but in whom the symptom index for reflux events was 50% or greater, and compared these with 15 healthy volunteer controls, and with control groups with confirmed excess reflux. The study group showed lower thresholds both for initial perception of oesophageal distension, and for discomfort, compared with healthy controls (median ml (range)); 7.5 (2-19) v 12 (6-30) (p = 0.002) and 10 (5-20) v 16 (8-30) (p < 0.0001), respectively. Sensory thresholds in the study group were also significantly lower than in patients with excess reflux, and than patients with Barrett's oesophagus, who also exhibited significantly higher sensory thresholds than healthy controls. No differences in sensory thresholds for somatic nerve stimulation were found between the study group and health controls. The results show a spectrum of visceral sensitivity in GORD, with enhanced oesophageal sensation in patients with symptomatic but not excess gastro-oesophageal reflux, suggesting that their symptoms result from a heightened perception of normal reflux events.

Basic and clinical aspects of visceral hyperalgesia

Although physiological stimuli in the healthy gastrointestinal tract are generally not associated with conscious perception, chronic abdominal discomfort and pain are the most common symptoms resulting in patient visits with gastroenterologists. Symptoms may be associated with inflammatory conditions of the gut or occur in the form of so-called functional disorders. The majority of patients with functional disorders appear to primarily have inappropriate perception of physiological events and altered reflex responses in different gut regions. Recent breakthroughs in the neurophysiology of somatic and visceral sensation are providing a series of plausible mechanisms to explain the development of chronic hyperalgesia within the human gastrointestinal tract. A central concept to all these mechanisms is the development of hyperexcitability of neurons in the dorsal horn, which can develop either in response to peripheral tissue irritation or in response to descending influences originating in the brainstem. Taking clinical characteristics and the concept of central hyperexcitability into account, a model is proposed by which abdominal pain from chronic inflammatory conditions of the gut and functional bowel disorders such as noncardiac chest pain, nonulcer dyspepsia, and irritable bowel syndrome could develop by multiple mechanisms either alone or in combination.

Southwestern Internal Medicine Conference: the syndrome of angina pectoris: role of visceral pain perception

Angina pectoris is a pain syndrome caused by coronary arteriosclerosis but also by a number of other disorders, including microvascular angina, gastroesophageal reflux (GER), and esophageal dysmotility. The relationship between abnormal physiology and pain in these conditions is complex. Simultaneous ambulatory monitoring of esophageal pH and motility has demonstrated that patients may have identical episodes of chest pain with acid reflux, dysmotility, both types of events, or neither. Patients may have anginal chest pain with inflation of an esophageal balloon, and patients with microvascular angina may have pain with catheter manipulation in the right atrium. Recent evidence suggests that disorders of visceral pain perception may play a role in both chest pain of esophageal origin and microvascular angina. The physiology of visceral pain is reviewed, including concepts of convergence of somatic and visceral afferent input, descending modulation of pain perception, and sensitization of visceral pain afferents. An approach to evaluation and treatment of chest pain in patients with angiographically normal coronary arteries is outlined.