Passive leg-lifting in heart failure patients predicts exercise-induced rise in left ventricular filling pressures

AIM

The aim of this study was to assess PCWP with passive leg-lifting (PLL) and exercise, in two groups of patients presenting with normal left ventricular ejection fraction (LVEF); one group with elevated NT-proBNP (eBNP), and one with normal NT-proBNP (nBNP) plasma concentration.

METHODS AND RESULTS

Fifty-one patients with eBNP (NT-proBNP ≥ 125 ng/l) and LVEF > 50%, were investigated and compared with 34 patients with nBNP (NT-proBNP < 125 ng/l) and LVEF > 50%. Both groups underwent right heart catheterization (RHC) at rest, PLL and exercise. From RHC, mean pulmonary arterial pressure (mPAP), cardiac output (CO), and PCWP were measured. All nBNP patients had PCWP < 15 mmHg at rest, and a PCWP of < 25 mmHg with PLL and during exercise. Patients with eBNP had higher (p < 0.01) resting mPAP, PCWP, and mPAP/CO. These values increased with exercise; however, CO increased less in comparison with nBNP patients (p = 0.001). 20% of patients with eBNP had a PCWP > 15 mmHg at rest, this percentage increased to 47% with PLL and 41% had a PCWP > 25 mmHg during exercise. Of those with PCWP > 25 mmHg during exercise, 91% had a PCWP > 15 mmHg with PLL. A PCWP > 15 mmHg on PLL had a 91% sensitivity and 92% specificity in predicting exercise-induced PCWP of > 25 mmHg.

CONCLUSION

In patients presenting with eBNP, PLL can predict which patients will develop elevated PCWP with exercise. These findings highlight the role of stress assessment.

The coronary calcium score is a more accurate predictor of significant coronary stenosis than conventional risk factors in symptomatic patients: Euro-CCAD study

AIMS

In this retrospective study we assessed the predictive value of the coronary calcium score for significant (>50%) stenosis relative to conventional risk factors.

METHODS AND RESULTS

We investigated 5515 symptomatic patients from Denmark, France, Germany, Italy, Spain and the USA. All had risk factor assessment, computed tomographic coronary angiogram (CTCA) or conventional angiography and a CT scan for coronary artery calcium (CAC) scoring. 1539 (27.9%) patients had significant stenosis, 5.5% of whom had zero CAC. In 5074 patients, multiple binary regression showed the most important predictor of significant stenosis to be male gender (B=1.07) followed by diabetes mellitus (B=0.70) smoking, hypercholesterolaemia, hypertension, family history of CAD and age but not obesity. When the log transformed CAC score was included, it became the most powerful predictor (B=1.25), followed by male gender (B=0.48), diabetes, smoking, family history and age but hypercholesterolaemia and hypertension lost significance. The CAC score is a more accurate predictor of >50% stenosis than risk factors regardless of the means of assessment of stenosis. The sensitivity of risk factors, CAC score and the combination for prediction of >50% stenosis when measured by conventional angiogram was considerably higher than when assessed by CTCA but the specificity was considerably higher when assessed by CTCA. The accuracy of CTCA for predicting >50% stenosis using the CAC score alone was higher (AUC=0.85) than using a combination of the CAC score and risk factors with conventional angiography (AUC=0.81).

CONCLUSION

In symptomatic patients, the CAC score is a more accurate predictor of significant coronary stenosis than conventional risk factors.

Regional changes in cerebral blood flow oxygenation can indicate global changes in cerebral blood flow during coronary artery occlusion in juvenile pigs

Near infrared spectroscopy (NIRS) is a widely employed method for assessment of regional cerebral oxygenation (RcStO2). RcStO2 values are expected to vary with changes in the relative amount of oxyhaemoglobin. The present experimental study aimed to assess the response of RcStO2 to controlled alterations of carotid blood flow (CQ). Landrace pigs were anesthetized followed by surgical preparation. Cyclic variations in cardiac output were accomplished by intermittently occluding the main stem of the left coronary artery. A flow measurement probe for assessing CQ was placed around the left carotid artery. One NIRS probe was placed on the left ipsilateral forehead to assess regional cerebral oximetry. Simultaneous registration of CQ and RcStO2 was conducted. There was a strong correlation for variation in CQ and RcStO2 signal values. Based on coherence analysis the fraction of power of the RcStO2 that was coherent with the CQ signal reached 0.84 ± 0.12 (P < 0.05) for frequencies lower than 0.1 Hz. The agreement of the sample-to-sample co-variation, as assessed by the Pearson correlation coefficient, was 0.83 ± 0.08 (P < 0.05). One explanatory component for variations in cerebral oxygenation verified by NIRS should be attributed to variations in the cerebral blood flow.

Gastric emptying in hereditary transthyretin amyloidosis: the impact of autonomic neuropathy

BACKGROUND

Gastrointestinal (GI) complications are common in hereditary transthyretin amyloidosis and an autonomic dysfunction has been considered to explain these symptoms. The aim of this study was to investigate the impact of autonomic neuropathy on gastric emptying in hereditary transthyretin amyloidosis and to relate these findings to nutritional status, GI symptoms, gender, and age at disease onset.

METHODS

Gastric emptying was evaluated with gastric emptying scintigraphy. Spectral analysis of the heart rate variability and cardiovascular responses after tilt test were used to assess the autonomic function. The nutritional status was evaluated with the modified body mass index (s-albumine × BMI).

KEY RESULTS

Gastric retention was found in about one-third of the patients. A weak correlation was found between the scintigraphic gastric emptying rate and both the sympathetic (rs = -0.397, P < 0.001) and parasympathetic function (rs = -0.282, P = 0.002). The gastric emptying rate was slower in those with lower or both upper and lower GI symptoms compared with those without symptoms (median T(50) 123 vs 113 min, P = 0.042 and 192 vs 113 min, P = 0.003, respectively). Multiple logistic regression analysis showed that age of onset (OR 0.10, CI 0.02-0.52) and sympathetic dysfunction (OR 0.23, CI 0.10-0.51), but not gender (OR 0.76, CI 0.31-1.84) and parasympathetic dysfunction (OR 1.81, CI 0.72-4.56), contributed to gastric retention.

CONCLUSIONS AND INFERENCES

Gastric retention is common in hereditary transthyretin amyloidosis early after onset. Autonomic neuropathy only weakly correlates with gastric retention and therefore additional factors must be involved.

Investigation of boundary conditions for biomimetic HA deposition on titanium oxide surfaces

To improve the clinical outcome of metal implants, i.e. earlier loading and reduction of the incidence of revision surgery, better bone bonding ability is wanted. One method to achieve this is to change the surface chemistry to give a surface that facilitates bone bonding in vivo, i.e. a bioactive surface. Crystalline titanium oxide has recently been proven to be bioactive in vitro and is an interesting option to the more common hydroxylapatite (HA) coatings on implants. A materials possible in vitro bioactivity is tested through soaking in simulated body fluid and studies of possible HA formation on the surface. For bioactive materials, the formed HA layer can also be used as a coating. The aim of the current paper is to investigate some boundary conditions for HA formation on crystalline titanium oxide surfaces regarding influence from coating thickness, soaking time and soaking temperature. The influence from soaking time and temperature on the HA growth were investigated on oxidised Ti samples, (24 h at 800 degrees C) resulting in a rutile surface structure. The oxidised samples were tested at three temperatures (4, 37 and 65 degrees C) and four times (1 h, 1 day, 1 week and 4 weeks). The influence from titanium coating thickness on the HA growth was investigated via depositing thin films of crystalline titanium dioxide on Ti plates using a reactive magnetron sputtering process. Four different PVD runs with coating thicknesses between 19 and 74 nm were tested. The soaking temperature had an effect on the HA formation and growth on both rutile surfaces and native oxide on Ti substrates. Higher temperatures lead to easier formation of HA. It was even possible, at 65 degrees C, to grow HA on native titanium oxide from soaking in PBS. The coating quality was better for HA formed at 65 degrees C compared to 37 degrees C. All PVD-coatings showed HA growth after 1 week in PBS at 37 degrees C, thus even very thin coatings of crystalline titanium oxide coatings are bioactive.

Can analysis of heart rate variability predict arrhythmia in children with Fontan circulation?

The aim of this study was to examine whether changes in heart rate variability (HRV) can predict arrhythmias in children who have undergone the Fontan procedure. The study included 15 children with total cavopulmonary connection. All examinations included echocardiography and 24-h ambulatory electrocardiogram with power spectral analysis of HRV and Poincaré plots (plots of each R-R interval as a function of the previous R-R interval). Six patients developed supraventricular tachycardia (four or more consecutive supraventricular beats). One patient was excluded from the study due to the development of bradycardia, necessitating placement of a pacemaker. Compared to the arrhythmia group, the patients without arrhythmias (n = 8) exhibited a significant difference in the standard deviation of instantaneous beat-to-beat R-R interval variability (p = 0.02). Poincaré plots of patients without arrhythmias showed a typical torpedo- or comet-shaped pattern, whereas the arrhythmia group showed a more complex pattern. Although this study examined only a few subjects, needing confirmation by larger studies, it does indicate that patients who develop arrhythmias after receiving the Fontan procedure show a different Poincaré pattern compared to the nonarrhythmic group-even before the arrhythmia can be detected using the conventional Holter procedure. Routine follow-up using the Holter procedure and Poincaré plot analysis could help detect early arrhythmias.

Adaptive spatio-temporal filtration of bioelectrical signals

In this paper we show how independent component analysis (ICA) algorithms can be used to perform spatio-temporal filtration of electromyographic (EMG) and electrocardiographic (ECG) signals. The technique was used to decompose the EMG signals into motor unit action potential (MUAP) trains. From the 88 outputs of the adaptive spatio-temporal filtration, three groups of different MUAP train patterns were found. The technique was also used to obtain a fetus' ECG and showed better result compared to using ICA.

Wireless system for real-time recording of heart rate variability for home nursing

Modern wireless communication technologies offer new possibilities for patient monitoring in hospitals, as well as at home or in outdoor environments. In this paper, we present a wireless system for ECG recordings and real-time analysis of heart rate variability (HRV). The system also makes it possible for distance consultation, for example with a specialist in cardiology, with the help of a WEB-solution.

Does the autonomic nervous system play a role in the development of insulin resistance? A study on heart rate variability in first-degree relatives of Type 2 diabetes patients and control subjects

AIMS

To investigate dysregulation of the autonomic nervous system as a potential mechanism for early insulin resistance in the development of Type 2 diabetes.

METHODS

Thirteen healthy individuals with first-degree relatives with Type 2 diabetes (R) were compared with 14 control subjects without family history of diabetes (C), matched for age, body mass index and sex. An oral glucose tolerance test and a hyperinsulinaemic euglycaemic clamp were performed. Analysis of heart rate variability during rest, controlled breathing, an orthostatic manoeuvre and a standardized physical stress (cold pressor test (CPT)), were used to evaluate the activity of the autonomic nervous system.

RESULTS

Fasting blood glucose, HbA1c and serum insulin were similar in the R and C groups. The M-value, reflecting insulin sensitivity, did not differ significantly between the groups. Total spectral power and high-frequency power were lower in R during controlled breathing (P = 0.05 and P = 0.07, respectively), otherwise there were no significant differences between R and C in heart rate variability. However, low-frequency (LF)/high-frequency (HF) spectral power ratio during CPT, reflecting sympathetic/parasympathetic balance, was negatively associated with insulin sensitivity (r = -0.53, P = 0.006). When all subjects were divided into two groups by the mean M-value, the low M-value group displayed an overall higher LF/HF ratio (P = 0.04). HF power was lower in the low M-value group during controlled breathing and CPT (P = 0.01 and P = 0.03, respectively).

CONCLUSION

An altered balance of the parasympathetic and sympathetic nervous activity, mainly explained by an attenuated parasympathetic activity, might contribute to the development of insulin resistance and Type 2 diabetes.

Sleep-disordered breathing and coronary artery disease: long-term prognosis

The evidence linking sleep-disordered breathing to increased mortality and cardiovascular morbidity has been conflicting and inconclusive. We hypothesized that a potential adverse effect of disordered breathing would be more obvious in patients with established vascular disease. In a prospective cohort study 408 patients aged 70 yr or younger with verified coronary disease were followed for a median period of 5.1 yr. An apnea-hypopnea index (AHI) of > or = 10 and an oxygen desaturation index (ODI) of > or = 5 were used as the diagnostic criteria for sleep-disordered breathing. The primary end point was a composite of death, cerebrovascular events, and myocardial infarction. There was a 70% relative increase and a 10.7% absolute increase in the primary composite end point in patients with disordered breathing defined as an ODI of > or = 5 (risk ratio 1.70, 95% confidence interval [CI] 1.15-2.52, p = 0.008). Similarly, patients with an AHI of > or = 10 had a 62% relative increase and a 10.1% absolute increase in the composite endpoint (risk ratio 1.62, 95% CI 1.09-2.41, p = 0.017). An ODI of > or = 5 and an AHI of > or = 10 were both independently associated with cerebrovascular events (hazard ratio 2.62, 95% CI 1.26-5.46, p = 0.01, and hazard ratio 2.98, 95% CI 1.43-6.20, p = 0.004, respectively). We conclude that sleep-disordered breathing in patients with coronary artery disease is associated with a worse long-term prognosis and has an independent association with cerebrovascular events.

Endoscopic transthoracic sympathicotomy affects the autonomic modulation of heart rate in patients with palmar hyperhidrosis

BACKGROUND

Palmar hyperhidrosis has been associated with an increased activity of the sympathetic nervous system. The objective of this study was to assess the immediate and long-term effects of endoscopic transthoracic sympathicotomy on the autonomic modulation of the heart rate in patients with palmar hyperhidrosis.

METHODS

Power spectrum analysis of heart rate variability in the lying position and after passive tilt to the upright position was performed in thirteen patients the day before and after sympathicotomy. A follow-up recording was performed in ten patients approximately six months later. Recordings from 26 healthy subjects were used as a reference group.

FINDINGS

The patients had a tendency to higher power of the low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF; above 0.15 Hz) components than controls in the upright position. After sympathicotomy LF power was reduced, but HF power was unchanged. At follow-up LF power remained at a lower level, but now HF power was reduced.

INTERPRETATION

Patients with palmar hyperhidrosis have a sympathetic overactivity but also a compensatory high parasympathetic activity. Sympathicotomy results in an initial sympathovagal imbalance with a parasympathetic predominance, which is restored on a long-term basis.

Pre- and post-season heart rate variability in adolescent cross-country skiers

To investigate the effects on cardiac autonomic control after a competitive cross-country skiing season, 9 females and 8 males, 16-19 years old, performed tilt-table heart rate variability (HRV) recordings and incremental treadmill tests before (August), and after (April the following year) the most intensive period of training and competition. Spectral analysis of HRV showed increased total variability at rest and reduced low frequency variability in the tilted position (LFtilt) at the second test (P<0.05). The female subgroup showed consistently higher high frequency (HF) and total heart rate variability than males. Total run time (RunT) increased from 18.5+/-1.9 min to 19.4+/-1.7 min (mean+/-SD) in the entire group (P<0.05), while VO2max only showed a non-significant increase (0.05<P<0.10). Submaximal heart rates (HRsubm) were reduced by an average of 4 beats (P<0.01) but maximal HR was unchanged. Performance data suggest a positive training effect. Following training, the increased total HRV the reduced LFtilt (both at rest), and the lower submaximal heart rates indicate an altered control of heart rate both at rest and during exercise. The consistently higher HF and total variability in the females indicate an increased parasympathetic activity in females compared with males.

Cardiac autonomic imbalance in an overtrained athlete

PURPOSE

In order to investigate overtraining-related adaptations in the autonomic nervous system, cardiac autonomic activity was examined in a junior cross-country skier who presented with reduced performance in competitions, early breathlessness during training sessions, and accumulated central fatigue.

METHODS

Power spectral analysis of heart rate variability (HRV) was performed before, when overtrained (OT), and after recovery (Rec).

RESULTS

In the overtrained state, high frequency (HF) and total powers in the lying position were higher compared with before and after. In normalized units, the increased HF in OT was even more prominent and clearly higher than in any control subject, and it was reversed in Rec. Resting heart rate was slightly reduced in OT and returned to baseline in Rec.

CONCLUSIONS

The shift toward increased heart rate variability, particularly in the HF range, together with a reduced resting heart rate suggest a cardiac autonomic imbalance with extensive parasympathetic modulation in this athlete when overtrained.

Short-term overtraining: effects on performance, circulatory responses, and heart rate variability

PURPOSE AND METHODS

Nine elite canoeists were investigated concerning changes in performance, heart rate variability (HRV), and blood-chemical parameters over a 6-d training camp. The training regimen consisted of cross-country skiing and strength training, in total 13.0+/-1.6 h, corresponding to a 50% increase in training load.

RESULTS

Time to exhaustion (RunT) decreased from 19.1+/-1.0 to 18.0+/-1.2 min (P < 0.05). VO2max and max lactate (La(max)) both decreased significantly (P < 0.05) over the training period (4.99+/-0.97 to 4.74+/-0.98 L x min(-1) and from 10.08+/-1.25 to 8.98+/-1.03 mmol x L(-1) respectively). Heart rates (HR) decreased significantly at all workloads. Plasma volume increased by 7+/-7% (P < 0.05). Resting cortisol, decreased from 677+/-244 to 492+/-222 nmol x L(-1) (P < 0.05), whereas resting levels of adrenaline and noradrenaline remained unchanged. The change between tests in RunT correlated significantly with the change in HRmax (r = 0.79; P = 0.01). There were no group changes in high or low frequency HRV, neither at rest nor following a tilt.

CONCLUSIONS

The reduced maximal performance indicates a state of fatigue/overreaching and peripheral factors are suggested to limit performance even though HRmax and La(max) both were reduced. The reduced submaximal heart rates are probably a result of increased plasma volume. HRV in this group didn't seem to be affected by short-term overtraining.

Cardiac rhythm in patients with sleep-disordered breathing and coronary artery disease

We examined the effect of sleep-disordered breathing on heart rates and arrhythmias in men and women with disabling angina pectoris and verified coronary artery disease by an overnight sleep study and Holter recording. The number of oxyhaemoglobin desaturations > or =4% (ODI) and number of apnoea-hypopnoeas per hour of sleep (AHI) were recorded. ODI > or =5 and AHI > or =10 were used as measures of disordered breathing and patients below these limits formed the control groups. One-hundred and forty-one men and 98 women < or =70 years of age were randomly included. Thirty-eight percent of the men and 36% of the women had an ODI > or =5. No serious ventricular arrhythmias occurred. Women with disordered breathing (ODI > or =5) had higher heart rates (mean 63.3 vs 59.1, p < 0.05) and a higher occurrence of ventricular premature contractions (VPCs) during sleep (75th percentiles 2.5 vs 0.5 per hour, p < 0.01). In men, however, no significant association between disordered breathing and heart rates or arrhythmias was found. We conclude that serious arrhythmias are infrequent in unselected patients with coronary artery disease and mild to moderate sleep-disordered breathing. Disordered breathing in women is associated with higher heart rates and a higher occurrence of VPCs during sleep.

Sleep-disordered breathing and myocardial ischemia in patients with coronary artery disease

STUDY OBJECTIVES

To examine the occurrence of nocturnal myocardial ischemia and its relationship to sleep-disordered breathing (apneas and oxygen desaturations) in randomly selected men and women undergoing coronary angiography because of angina pectoris.

DESIGN

An observational study using an overnight sleep study and Holter recording to examine disordered breathing (oxyhemoglobin desaturations > or = 4% and apnea-hypopneas), heart rates, and ST-segment depressions (> or = 1 mm, > or = 1 min).

SETTING

University Hospital, Umeå, a teaching hospital in northern Sweden.

PATIENTS

One hundred thirty-two men and 94 women referred for consideration of coronary intervention were randomly included, by lot.

RESULTS

ST-segment depressions occurred in 59% (134 of 226) of the patients, and nocturnal ST-segment depressions occurred in 31% (69 of 226). A ST-segment depression occurred within 2 min after an apnea-hypopnea or desaturation in 12% (27 of 226) of patients. This temporal association was seen in 19% of nocturnal ST-segment depressions (71 of 366), more frequently in men (p < 0.01) and in more severely disordered breathing (p < 0.001). Most of these ST-segment depressions were preceded by a series of breathing events: three or more apnea-hypopneas or desaturations or both in 70% (50 of 71).

CONCLUSION

Episodes of nocturnal myocardial ischemia are common in patients with angina pectoris. However, a temporal relationship between sleep-disordered breathing and myocardial ischemia is present only in a minority of the patients, but occurs more frequently in men and in more severely disordered breathing.

Autonomic cardiovascular regulation in patients with obstructive sleep apnoea: a study based on spectral analysis of heart rate variability

The aim of this study was to assess the function of the autonomic nervous system in patients with obstructive sleep apnoea syndrome (OSAS). The study was designed as a cross-sectional case-control study. Fifty-one patients were included, and the findings were compared with those in 66 controls. Spectral analysis of heart rate variability (HRV) during supine rest, during controlled breathing and after tilting was performed in each patient and control case. The patients performed overnight sleep recordings the night before the HRV recordings. Individuals with an apnoea-hypopnoea index (AHI) above 20 were regarded as OSAS patients and those with AHI lower than 20 as snorers. Differences in HRV and blood pressure between patients and controls were analysed by multiple linear regression with age, body mass index and sex as independent variables. During free and controlled breathing there was a significant decrease in indices reflecting vagal modulation, indicating parasympathetic dysfunction in OSAS patients compared with controls. The mid-frequency component was also significantly reduced in OSAS patients after tilting but not in the lying position. This may be related to the parasympathetic dysfunction, but could also indicate a decreased sympathetic reserve capacity. We found no significant relation between AHI and indices of vagal modulation in the patient group. Our findings show an autonomic dysfunction in patients with OSAS. The dysfunction involves the parasympathetic system, and may be related to the increased cardiovascular mortality and malignant arrhythmia described in OSAS.

Heel lancing in term new-born infants: an evaluation of pain by frequency domain analysis of heart rate variability

The aim of the investigation was to assess pain by frequency domain analysis of heart rate variability (HRV) during a routine heel lancing procedure in term new-born infants. Beat-to-beat heart rate (HR) was recorded in 23 healthy new-born infants on the maternity ward during blood sampling for neonatal screening. A sham heel prick prior to the sharp lancing procedure was performed randomly in half of the infants. Spectral analysis of HRV was assessed for each of the following sequences: (1) baseline (2) sham heel prick (3) sharp heel prick and (4) squeezing the heel for blood sampling. The response to the sham prick did not differ significantly from the sharp prick. Compared with the baseline, sharp lancing gave rise to minor increases in HR and variability in the low frequency band of the spectral analysis. A clear stress response was provoked when the heel was squeezed for blood sampling, indicated by an increased HR and a decreased spectral power in the high frequency band (i.e. lower vagal tone). The different stress responses during the lancing and the squeezing of the heel were clearly illustrated when principal component analysis was applied and the vectors for the changes in HR and spectral pattern were indicated. In conclusion, the squeezing of the heel is the most stressful event during the heel prick procedure.

Spectral analysis of heart rate variability in patients with irritable bowel syndrome

BACKGROUND

Autonomic dysfunction, both adrenergic and cholinergic, has been associated with the irritable bowel syndrome (IBS). The accuracy of the methods in use, however, has been limited by the need for active co-operation by the patients, with consequent difficulties in standardization. The aim of this study was to investigate the function of the autonomic nervous system in patients with IBS by using spectral analysis of the heart rate variability, an accurate method depending very little on patient cooperation.

METHODS

Eighteen patients with IBS were compared with 36 sex- and age-matched controls. Spectral analysis of heart rate variability was performed to quantify sympathetic and parasympathetic nerve activity.

RESULTS

The patients with IBS had significantly higher sympathetic activity than controls (P = 0.005). There was no significant (P = 0.308) increase in parasympathetic activity. There were no significant differences in heart rate or blood pressure between the patients and controls.

CONCLUSION

Spectral analysis of heart rate variability has been used to assess the function of the autonomic nervous system in patients with IBS. IBS patients have significantly increased symphathetic activity, whereas parasympathetic activity does not differ from that of controls.

Impact of liver transplantation on autonomic neuropathy in familial amyloidotic polyneuropathy: an evaluation by spectral analysis of heart rate variability

OBJECTIVES

To evaluate the impact of liver transplantation on familial amyloidotic polyneuropathy type I (FAP) patients' autonomic neuropathy.

DESIGN

An open study.

SETTING

A tertiary referral centre.

SUBJECTS

Twelve liver-transplanted FAP patients evaluated before and one year or longer after liver transplantation.

INTERVENTIONS

Spectral analysis of heart rate variability. The low-frequency band after tilting (sympathetic), and the high-frequency band in supine position (parasympathetic) were analysed, as were the pulse and blood pressure reaction to tilting. Clinical symptoms related to autonomic disturbances were recorded.

MAIN OUTCOME MEASURES

Spectral band power for sympathetic and parasympathetic activity.

RESULTS

No statistically significant improvements in sympathetic or parasympathetic band power after liver transplantation was found (sympathetic band power: 2.7 (2.2-3.2) before, 2.9 (2.2-3.6) after; parasympathetic 2.0 (1.6-2.4) before and 2.0 (1.7-2.3) after. A significant correlation was noted between orthostatic blood pressure reaction and sympathetic activity before transplantation, but not after the operation. A trend was noted for improved orthostatic blood pressure reaction. Symptomatic improvements in bowel function and orthostatic symptoms were reported by several patients.

CONCLUSIONS

Although improvements in autonomic symptoms are reported after liver transplantation, no significant improvement is noted in sympathetic or parasympathetic spectral band power of heart rate variability. However, the follow-up period of 17 months may be too short. Further evaluation after an additional two and four years is needed.

Assessment of acute pain in preterm infants by evaluation of facial expression and frequency domain analysis of heart rate variability

In ten preterm infants (postconceptional age 27-35 weeks) facial expression and heart rate variability (HRV) were investigated during three situations: (a) the infant at rest in its crib or incubator, (b) provocation of the withdrawal flexor reflex by application of von Frey's hairs, and (c) lancing and squeezing for blood sampling. Video recordings of facial expressions, mixed at random, were categorised as the baby being either undisturbed, disturbed or in pain and a detailed scoring for each situation was performed. Mean heart rate (HR) was calculated and power spectral analysis was assessed on data from segments of 45-s duration from the three procedures. Flexor withdrawal did not evoke visual signs of pain or influence HRV, but caused a slight increase in HR. The lancing and squeezing of the heel evoked a facial expression of pain in all infants. The HR increased and a reduction in both total HRV and power in the low frequency band of the HRV spectrum was seen during blood sampling. The differentiation between painful and non-painful procedures was more apparent when principal component analysis of HRV was applied.

Impact of autonomic neuropathy on circulatory instability during liver transplantation for familial amyloidotic polyneuropathy

BACKGROUND

Circulatory instability with severe hypotension frequently complicates liver transplantation in patients with familial amyloidotic polyneuropathy. Autonomic dysfunction is found early in the course of the disease by analysis of beat-to-beat heart rate variability (HRV). The aim of the present study was to investigate the impact of autonomic neuropathy on intraoperative circulatory instability during liver transplantation for familial amyloidotic polyneuropathy.

METHODS

Twenty-two patients were evaluated at the Department of Medicine, Umea University Hospital, by spectral analysis of HRV and later received liver transplants at Huddinge University Hospital. The low-and high-frequency bands obtained by spectral analysis of HRV in the supine and upright positions, respectively, were used as representative of sympathetic and parasympathetic activity. Circulatory instability during transplantation was defined as a fall in systolic arterial blood pressure below 70 mmHg for more than 5 min during the preanhepatic phase.

RESULTS

Both arrhythmia preventing spectral analysis of HRV and a sympathetic variability peak below 2.5 mHz2 were significantly more common among patients with intraoperative circulatory instability (P=0.03 and 0. 004, respectively). A diminished increase in pulse rate when tilting the patients from the supine to the upright position was also more pronounced among patients with circulatory instability (P<0.05).

CONCLUSIONS

The majority of patients who will develop circulatory instability with a pronounced fall in arterial blood pressure can be identified by Poincare plots of R-R intervals and spectral analysis of HRV. A low sympathetic peak or arrhythmia precluding spectral analysis of HRV is significantly related to operative circulatory instability.

Sleep-disordered breathing in women: occurrence and association with coronary artery disease

PURPOSE

To examine the occurrence of sleep apnea and nocturnal hypoxemia in women with and without coronary artery disease (CAD) and to investigate the relationship between sleep-disordered breathing and coronary artery disease.

PATIENTS AND METHODS

In a case-control study, 102 cases were randomly selected among women with angina pectoris and angiographically verified coronary disease. Fifty age-matched controls without known heart disease were selected from the population registry. Pulse oximetry, oronasal thermistors, body position indicator, and recording of body and respiratory movements were used to quantify oxygen desaturations (the number of desaturations > or = 4% per hour of sleep, oxygen desaturation index [ODI]) and apneas (the number of apneas or hypopneas per hour of sleep, apnea-hypopnea index [AHI]).

RESULTS

Women with CAD had a high occurrence of disordered breathing measured as AHI > or = 5, 54% (n = 54), AHI > or = 10, 30% (n = 30) or ODI > or = 5, 34% (n = 35) while the same proportions in controls were 20% (n = 10, P < 0.0001), 10% (n = 5, P < 0.01) and 18% (n = 9, P < 0.05), respectively. In a multiple logistic regression model, sleep apnea (AHI > or = 5), hypertension, and smoking habits were independent predictors of CAD with odds ratios of 4.1 (95% confidence interval [CI] 1.7 to 9.7, P < 0.01), 3.4 (CI 1.3 to 8.9, P < 0.05) and 2.4 (CI 1.0 to 5.7, P < 0.05), respectively.

CONCLUSION

Sleep apnea is common in women with CAD and remains as a significant predictor of coronary disease after adjustment for age, body mass index, hypertension, smoking habits, and diabetes.

Assessment of autonomic nerve function in acute intermittent porphyria; a study based on spectral analysis of heart rate variability

OBJECTIVES

To assess the function of the autonomic nervous system in patients with acute intermittent porphyria by spectral analysis of the heart rate variability.

DESIGN

A cross-sectional case-control study.

SETTING

Patients were examined at the Primary Health Care Centre, Arjeplog and at Umeå University Hospital, where the controls were also examined.

SUBJECTS

Twenty-three patients with acute intermittent porphyria verified by DNA analysis and 92 healthy controls were included.

MAIN OUTCOME MEASURES

The mid-frequency band power after tilting was used to evaluate sympathetic function, and the high frequency band power during controlled breathing at 12 breaths min-1 and the mid-frequency band power during controlled deep breathing at 6 breaths min-1 were used to evaluate parasympathetic function.

RESULTS

There was no evidence of sympathetic dysfunction in the patients. The mid-frequency band power during controlled deep breathing at 6 breaths min-1 was significantly (P = 0.02) lower in the patient group.

CONCLUSIONS

Our findings indicate a parasympathetic dysfunction in patients with acute intermittent porphyria. This may be causally related to sudden cardiac death and the life-threatening arrhythmias which have been observed in this disorder.

Sleep-disordered breathing in men with coronary artery disease

OBJECTIVE

To examine the occurrence of sleep apnea and nocturnal hypoxemia in men with symptomatic coronary artery disease (CAD) and to evaluate the relationship between disordered breathing and coronary artery disease.

DESIGN

Case-control study. Cases were randomly selected from men undergoing coronary angiography because of angina pectoris. Controls were age matched and selected from the population registry. Pulse oximetry, oronasal thermistors, body position indicator, and recording of body and respiratory movements were used to quantify desaturations and apneas.

SETTING

Norrland University Hospital, a referral center for northern Sweden.

SUBJECTS

One hundred forty-two men with angina pectoris and angiographically verified CAD and 50 controls without known heart disease.

MAIN OUTCOME MEASURES

The number of arterial oxygen desaturations of 4% or more per hour of sleep, oxygen desaturation index (ODI), and the number of apneas or hypopneas per hour of sleep, apnea-hypopnea index (AHI).

RESULTS

Men with CAD had a high occurrence of sleep-disordered breathing measured as ODI of 5 or more, 39% (n=55), or AHI of 10 or more, 37% (n=50), while, the same proportions in controls were 22% (n=11, p<0.05) and 20% (n=10, p<0.05). Mean values of ODI in cases and controls were 6.4 and 2.7, respectively (p<0.001). Multiple logistic regression analysis identified ODI, AHI, body mass index, and hypertension as significant predictors of CAD (p<0.05).

CONCLUSION

Sleep- disordered breathing is common in men with CAD. A significant association between sleep apnea with nocturnal hypoxemia and CAD remains after adjustment for age, hypertension, body mass index, diabetes, and smoking.

Computer-assisted evaluation of dipyridamole thallium-201 SPECT in patients with aortic stenosis

Dipyridamole SPECT detects significant coronary artery disease (CAD) in patients without aortic stenosis. This study was done to establish normal 201Tl distribution limits in patients with aortic stenosis and to apply these normal limits to patients with aortic stenosis and angiographically significant CAD (> or = 75% area reduction).

METHODS

Fifty-two patients (mean age 68 yr; mean valve area 0.67 cm2) were examined with 201Tl SPECT after dipyridamole infusion (0.56 mg/kg during 4 min). After tomographic reconstruction, basal, mid-ventricular and apical short-axis slices were selected. The highest activity in each six-degree segment was normalized to the maximal activity of each slice.

RESULTS

Significant CAD was found in 24 patients. Five patients without CAD, but with localized hypokinesia or left bundle-branch block, were excluded from the reference group which finally consisted of 16 patients. Sensitivity for CAD was 88% when the lowest relative activity in each segment was used as the lower limit of normal. With -2 s.d. and -2.5 s.d. curves the sensitivity was 83% and 75%, respectively. Gender-specific limits were not used. Nonsignificant CAD was found in seven patients (< 75% stenoses).

CONCLUSIONS

This study presents the normal distribution of 201Tl uptake for patients with aortic stenosis, using dipyridamole SPECT. The range method had the highest sensitivity for detection of significant CAD.

Heart-rate variation: what are we measuring?

Many methods have been proposed during the last two decades for the assessment of autonomic nervous system function by quantification of the heart-rate variation (HRV). Relatively little has been written about the HRV in relation to physiological models of the heart-rate regulation. The integral pulse frequency model (IPFM) is a simple model that describes the genesis of heartbeats under the influence of the autonomic nervous system. By comparing simulated HRV data generated with the IPFM model with data from healthy volunteers we found similarities indicating that the model accurately reflects real data. Furthermore, we found a considerable difference between HRV measurements based on beat-by-beat heart-rate and measurements based on the heartbeat interval. Our results suggest that the commonly used electrocardiographic RR interval representation of heart-rate variation might possess an inherent nonlinear, mean heart-rate-dependent property indicating that analysis directly based on RR intervals can give biased results with respect to the underlying autonomic activity. The conclusions embrace all measurements of variation that are directly based on RR intervals including simple indices as well as higher-level quantification such as spectral analysis.