Multiparametric analysis of heart rate variability used for risk stratification among survivors of acute myocardial infarction

A multiparametric heart rate variability analysis was performed to prove if combined heart rate variability (HRV) measures of different domains improve the result of risk stratification in patients after myocardial infarction. In this study, standard time domain, frequency domain and non-linear dynamics measures of HRV assessment were applied to 572 survivors of acute myocardial infarction. Three parameter sets each consisting of 4 parameters were applied and compared with the standard measurement of global heart rate variability HRVi. Discriminant analysis technique and t-test were performed to separate the high risk groups from the survivors. The predictive value of this approach was evaluated with receiver operator (ROC) and positive predictive accuracy (PPA) curves. Results--The discriminant analysis shows a separation of patients suffered by all cause mortality in 80% (best single parameter 74%) and sudden arrhythmic death in 86% (73%). All parameters of set 1 show a high significant difference (p < 0.001) between survivors and non-survivors based on two-tailed t-test. The specificity level of the multivariate parameter sets is at the 70% sensitivity level (ROC) about 85-90%, whereas HRVi shows maximum levels of 70%. The PPA in the all cause mortality group is at the 70% sensitivity level twice as high as the univariate HRV measure and increases to more than fourfold as high within the VT/VF group. In conclusion, in this population, the multiparametric approach with the combination of four parameters from all domains especially from NLD seems to be a better predictor of high arrhythmia risk than the standard measurement of global heart rate variability.

Angiotensin-converting enzyme and angiotensinogen gene polymorphisms and heart rate variability in twins

Decreased heart rate variability (HRV) is associated with congestive heart failure, post-myocardial infarction, ventricular arrhythmias, sudden cardiac death, and advancing age. A deletion/insertion polymorphism in the angiotensin-converting enzyme (ACE) gene and a substitution (M235T) in the angiotensinogen gene have been associated with risk for heart disease. The aim of this study was to determine the heritability of HRV and related parameters in monozygotic and dizygotic twins and to assess the influence of ACE and angiotensinogen polymorphisms. We studied 95 MZ pairs and 46 DZ pairs. We measured HRV and related parameters, ACE and angiotensinogen levels, plasma norepinephrine, ACE, and angiotensinogen genotypes. We found that HRV and related parameters were significantly influenced by genetic variability, although nonshared genetic effects were also important. Angiotensinogen and plasma norepinephrine were generally correlated with decreased HRV, whereas ACE was correlated with perturbances of normal rhythmic HRV. Nevertheless, the DD ACE genotype was associated with increased HRV (p <0.05), whereas angiotensinogen polymorphisms had no effect. We conclude that HRV and related parameters are in part heritable. Interestingly, the DD ACE genotype is associated with increased HRV.

Multiparametric analysis of heart rate variability used for risk stratification among survivors of acute myocardial infarction

A multiparametric heart rate variability analysis was performed to prove if combined heart rate variability (HRV) measures of different domains improve the result of risk stratification in patients after myocardial infarction. In this study, standard time domain, frequency domain and non-linear dynamics measures of HRV assessment were applied to 572 survivors of acute myocardial infarction. Three parameter sets each consisting of 4 parameters were applied and compared with the standard measurement of global heart rate variability HRVi. Discriminant analysis technique and t-test were performed to separate the high risk groups from the survivors. The predictive value of this approach was evaluated with receiver operator (ROC) and positive predictive accuracy (PPA) curves. Results--The discriminant analysis shows a separation of patients suffered by all cause mortality in 80% (best single parameter 74%) and sudden arrhythmic death in 86% (73%). All parameters of set 1 show a high significant difference (p < 0.001) between survivors and non-survivors based on two-tailed t-test. The specificity level of the multivariate parameter sets is at the 70% sensitivity level (ROC) about 85-90%, whereas HRVi shows maximum levels of 70%. The PPA in the all cause mortality group is at the 70% sensitivity level twice as high as the univariate HRV measure and increases to more than fourfold as high within the VT/VF group. In conclusion, in this population, the multiparametric approach with the combination of four parameters from all domains especially from NLD seems to be a better predictor of high arrhythmia risk than the standard measurement of global heart rate variability.

[Priapism. Etiology, diagnosis and treatment]

Priapism is a condition of prolonged penile erection which often causes pain and is unrelated to sexual desire. There is a high risk of impotence despite immediate intervention. The incidence has doubled since the introduction of intracorporeal injection therapy for impotence. Two subtypes of priapism have been described, depending on the underlying cause. The more common type, termed low flow, is characterised by inadequate venous outflow, leading to a hypoxic painful prolonged erection. The etiology is either idiopathic or related to intracorporeal injection therapy. Treatment consists of aspiration and instillation of a diluted alpha-adrenergic agent, or surgery, depending on the degree of hypoxia. The less common subtype, high flow, is arteriogenic, and causes less pain and no ischemia. Injury to a cavernous artery leads to a fistula between the artery and the corpora cavernosa. Treatment is either conservative with immediate ice pack and compression, or delayed selective embolization of the fistula.

The application of methods of non-linear dynamics for the improved and predictive recognition of patients threatened by sudden cardiac death

OBJECTIVES

This study introduces new methods of non-linear dynamics (NLD) and compares these with traditional methods of heart rate variability (HRV) and high resolution ECG (HRECG) analysis in order to improve the reliability of high risk stratification.

METHODS

Simultaneous 30 min high resolution ECG's and long-term ECG's were recorded from 26 cardiac patients after myocardial infarction (MI). They were divided into two groups depending upon the electrical risk, a low risk group (group 2, n = 10) and a high risk group (group 3, n = 16). The control group consisted of 35 healthy persons (group 1). From these electrocardiograms we extracted standard measures in time and frequency domain as well as measures from the new non-linear methods of symbolic dynamics and renormalized entropy.

RESULTS

Applying discriminant function techniques on HRV analysis the parameters of non-linear dynamics led to an acceptable differentiation between healthy persons and high risk patients of 96%. The time domain and frequency domain parameters were successful in less than 90%. The combination of parameters from all domains and a stepwise discriminant function separated these groups completely (100%). Use of this discriminant function classified three patients with apparently low (no) risk into the same cluster as high risk patients. The combination of the HRECG and HRV analysis showed the same individual clustering but increased the positive value of separation.

CONCLUSIONS

The methods of NLD describe complex rhythm fluctuations and separate structures of non-linear behavior in the heart rate time series more successfully than classical methods of time and frequency domains. This leads to an improved discrimination between a normal (healthy persons) and an abnormal (high risk patients) type of heart beat generation. Some patients with an unknown risk exhibit similar patterns to high risk patients and this suggests a hidden high risk. The methods of symbolic dynamics and renormalized entropy were particularly useful measures for classifying the dynamics of HRV.

[Thromboembolic complications in ambulatory surgery. A retrospective study of 1691 patients]

The risk of thromboembolic complications in outpatient surgery is regarded as being low. Thromboembolic prophylaxis is seldom administered as a routine. A retrospective study in our outpatient department, based upon patients readmitted for clinical thromboembolism, showed an incidence of deep vein thrombosis of 0.05% (8/1 691) and of pulmonary embolism 0.0006% (1/1 691). None of the patients received prophylaxis for thrombosis, and all operations were performed under regional anaesthesia of the lower extremity. 50% of the operations were performed using a tourniquet. 2/3 of the patients were women and 2/3 were over the age of 50. Operation time was usually 30-45 minutes. Our study indicates that patients undergoing knee arthroscopy, and operations for varicose veins and hallux valgus are at risk of thromboembolism. Prospective studies of these risk groups are necessary to figure out the need for thrombosis prophylaxis.

[Spontaneous retroperitoneal hemorrhage]

Spontaneous retroperitoneal haemorrhage is most frequently due to rupture of an abdominal aortic aneurysm. Pathology in other retroperitoneal organs, most often the kidney and the adrenal gland, may cause retroperitoneal haemorrhage. Spontaneous rupture of veins, especially the iliac vein, and haemorrhage secondary to anticoagulant therapy, are less common causes. The symptoms are variable and non-specific, but most often include acute abdominal pain, hypotension, peritoneal irritation and a palpable abdominal mass. The diagnosis is confirmed by ultrasonography, computerized tomography, and if relevant angiography or scintigraphy. We discuss three patients with spontaneous retroperitoneal haemorrhage, examine the clinical approach and the role of the various diagnostic aids, and consider how the various conditions should be dealt with.

Familial and genetic influences on heart rate variability

The authors tested the hypothesis of a genetic influence on heart rate variability (HRV). This genetic influence was assessed in 62, twin pairs (30 monozygotic, 32 dizygotic). From all twins, long-term electrocardiographic records were obtained, edited, and analyzed. Heart rate variability analysis was performed on the basis of parameters from time-domain, frequency-domain, and nonlinear dynamics. First, the parameter distances between the two twins of a pair and between one of the two and a third randomly selected person of another age-matched twin pair (ST1) were compared. Second, the parameter distances between the two twins and the averaged parameter distances of these two twins to all other age-matched persons (ST2) were compared. Finally, the averaged differences in parameter values between monozygotic and dizygotic age-matched twin pairs were compared. For statistical analysis, the nonparametric Wilcoxon's matched-pair signed rank test and parametric t-test for paired samples were used. Twin pairs show a significant lower difference in parameter values than other randomly selected and age-matched couples (P < .001 in ST1 and ST2). This reflects a considerable familial influence. Most parameters of the time-domain, none of the frequency-domain, and half of the nonlinear dynamics show significant differences between twin pairs and nontwin pairs. As a result of the comparison between monozygotic and dizygotic twin pairs, a significant lower parameter difference in the monozygotic pairs (P < .05) is found. These results suggest that there is a genetic component in heart rate generation and HRV, in addition to family environmental influences. Analysis of HRV might become a useful method in phenotyping severe genetic changes in cardiovascular diseases.

[Bladder rupture. Diagnosis, etiology and treatment]

The majority of bladder ruptures (80-90%) are caused by major blunt abdominal trauma. Penetrating injuries account for the rest. Bladder rupture is seen most often in patients with pelvic fracture. More seldom, the rupture can be caused by energetic blunt abdominal trauma. The rupture can either be intraperitoneal or extraperitoneal. The symptoms are macroscopic haematuria, suprapubic pain and, in some patients, an inability to avoid. Retrograde cystography is the diagnostic procedure of choice. An intravenous infusion pyelogram does not provide adequate examination of the bladder. The rupture is treated by operative closure and drainage by catheter. Extraperitoneal rupture may be treated with only catheter drainage and close clinical evaluation. We describe two patients with intraperitoneal bladder rupture after low energetic abdominal trauma.

[Should oral contraceptives and postmenopausal hormonal substitution be withdrawn prior to surgery? A questionnaire study in departments of surgery and gynecology]

We conducted a survey among the surgical and gynaecological departments of all Norwegian hospitals, about today's practice concerning oral contraceptives and surgery. Most of the surgical and gynaecological departments recommend discontinuance of the pill two and four weeks prior to surgery, and reintroduction upon mobilisation postoperatively. In surgical emergencies amongst women who use the pill, 4/5 surgical and 2/3 gynaecological departments would prefer to give thrombosis prophylaxis. Low molecular weight heparin was recommended most. Surgical departments especially recommend stopping the use of the progestogene only contraceptive pill, and post menopausal oestrogen substitution, before elective surgery. Both gynaecological and surgical departments give inadequate information about the use of alternative birth control during the period when the pill is not taken. The survey did not show any difference between university and central/county hospitals.

Quantitative analysis of heart rate variability

In the modern industrialized countries every year several hundred thousands of people die due to sudden cardiac death. The individual risk for this sudden cardiac death cannot be defined precisely by common available, noninvasive diagnostic tools like Holter monitoring, highly amplified ECG and traditional linear analysis of heart rate variability (HRV). Therefore, we apply some rather unconventional methods of nonlinear dynamics to analyze the HRV. Especially, some complexity measures that are based on symbolic dynamics as well as a new measure, the renormalized entropy, detect some abnormalities in the HRV of several patients who have been classified in the low risk group by traditional methods. A combination of these complexity measures with the parameters in the frequency domain seems to be a promising way to get a more precise definition of the individual risk. These findings have to be validated by a representative number of patients. (c) 1995 American Institute of Physics.

Improved analysis of heart rate variability by methods of nonlinear dynamics

The traditional analysis of heart rate variability (HRV) in the time and frequency domains seems to be an independent predictive marker for sudden cardiac death. Because the usual applied methods of HRV analysis describe only linear or strong periodic phenomena, the authors have developed new methods of HRV analysis based on nonlinear dynamics. In that way, parameters are extracted that quantify more complex processes and their complicated relationships. These methods are symbolic dynamics that describes the beat-to-beat dynamics and renormalized entropy that compares the complexity of power spectra on a normalized energy level. In an initial investigation, the HRV of 35 healthy subjects and 39 cardiac patients have been analyzed. Using discriminant functions, the authors found an optimal (100%) differentiation between the group of healthy subjects (even using only an age-matched subgroup of 12 subjects) and that of patients after myocardial infarction with a high electrical risk (Lown 4b). Applying this discriminant function to a group of patients with low electrical risk, four patients show the same behavior indicative of a high risk score, which might be a sign for a hidden high risk, two patients show healthy behavior, and the remaining patients show a separate pattern. The use of new methods of nonlinear dynamics in combination with parameters of the time and frequency domains in HRV offers possibilities for improved classification of HRV behavior. It is suggested that this could lead to a more detailed classification of individual high risk.

[New methods for the detection of high risk patients in cardiology]

Common non-invasive diagnostic methods like Holter monitoring or the analysis of high-resolution ECG and heart rate variability are unable to accurately assess the individual risk for sudden cardiac death, since they describe only statistical, linear or strictly periodic parameters. Using new methods of non-linear dynamics one can now calculate parameters which much better describe the dynamic behaviour of complex systems. The application of these new methods should therefore lead to an improved identification of high-risk patients. The results of this first pilot investigation show on the one hand that ventricular arrhythmias are quick detectable using phase space plots, and on the other hand that the new methods of non-linear dynamics could lead to a new classification of high-risk patients.

[Acute idiopathic scrotal edema]

A history of acute idiopathic scrotal oedema is described, for the first time in Norway. A four year-old boy with acute scrotal swelling and erythema was operated on. The operative findings were oedema in subcutis and dartos muscle. Acute idiopathic scrotal oedema is observed most often in prepubertal boys. It is recognized by acute uni/bilateral scrotal swelling, erythema and mild scrotal discomfort. The aetiology is unclear but the disorder is probably allergic in origin. It is best treated with rest in bed and observation.

The prevalence of hepatitis A and B in Norwegian merchant seamen--a serological study

The prevalence of viral hepatitis in Norwegian merchant seamen in overseas trade was studied in 523 volunteers during compulsory health control before embarkation from the port of Oslo. The prevalence of hepatitis B markers was 9.4%, which is significantly higher than in the general Norwegian population. The prevalence increased with the number of years of occupation. It was associated with frequent casual sexual contacts in foreign countries, but not significantly increased in participants who had been exposed to tattooing or different types of medical treatment under poor hygienic conditions in foreign areas. The prevalence of antibodies against hepatitis A (HAV) was 36% in seamen born in 1945 or earlier and 5% in younger individuals, an age-dependent pattern which is essentially similar in the general Norwegian population. However, the prevalence of hepatitis A antibodies seemed to increase with years in foreign trade. The incidence of viral hepatitis infections in the occupation was noticeably high, suggesting that vaccination of seamen in certain areas of trade should be considered.