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Biomedical subjects

M Riha

Publications and source records attributed to M Riha.

15 recordsLinked to original sources
PubMed1992

Dynamic changes of the QRS complex in unstable angina pectoris.

Despite intensive medical treatment to control chest pain, about one-third of patients with unstable angina have an unfavourable outcome within a period of 1 to 2 months. Holter monitoring can identify patients with silent myocardial ischaemia that are at a high risk of sustaining a major cardiovascular event. The present paper describes the use of dynamic, continuous, computerized on-line vectorcardiography for real-time monitoring of QRS-complex and ST-segment changes in patients with unstable coronary disease. In many patients a pattern of frequent repetitive episodes of QRS change was observed, with or without concomitant ST change. Whereas no patient had episodes of ST-vector change without also having episodes of significant QRS change, 15 patients had several episodes of QRS changes without any episode of significant ST change. The number of episodes of significant increase of the QRS vector difference correlated weakly but significantly with the number of episodes of significant ST-vector magnitude change (r = 0.34, p less than 0.05). The present study suggests that myocardial ischaemia will influence the QRS complex as well as the ST segment. The mechanism behind the QRS changes observed is not clear but episodes of QRS change without ST change or chest pain, may reflect sudden depressions of left ventricular function, as has been reported by others to occur in patients with coronary artery disease. Dynamic vectorcardiography offers the opportunity to monitor all parts of the QRST complex in real time.

Adult↗
PubMed1992

Exercise-induced QRS changes in healthy men and women: a multivariate analysis on their relation to background data and exercise performance.

Changes in the QRS segment during exercise have repeatedly been suggested to provide diagnostic information with respect to ischaemic heart disease, but the subject is controversial. In order to study the possibly confounding effects of gender, age, resting ECG and exercise performance, 50 healthy subjects were investigated with computerized vectorcardiography during a maximal ergometer exercise test. The overall change in the QRS complex decreased significantly with age and female gender (P < 0.001). However, these responses were better explained by baseline QRS size, change in heart rate and systolic blood pressure (adjusted r2 > 0.70, vs adjusted r2 > 0.41). Effects of age were seen in the Y-lead, and gender effects in the X- and Z-leads (P < 0.0001). In multivariate analyses, X- and Y-lead alterations correlated negatively to change in heart rate and resting QRS size (X-lead; adjusted r2 > 0.50, Y-lead; r2 > 0.44). Z-lead alterations correlated negatively with female gender and resting Z-lead QRS size (adjusted r2 > 0.31). ST changes correlated with QRS changes in the X- and Y-leads (P < 0.05). QRS changes immediately after exercise correlated with alterations during exercise (P < 0.004), maximal load (P < 0.01) and time to hypotension post-exercise (X- and Z-lead; P < 0.02). In conclusion, QRS changes appear to be related to baseline QRS size, change in heart rate and ST change, factors which may have important confounding effects. Consideration of these factors may help in resolving the controversy surrounding QRS changes.

Adult↗
PubMed1992

Ischaemic heart disease and the changes in the QRS and ST segments during exercise: a pilot study with a novel vectorcardiographic system.

In order to find new ischaemic parameters, the spatial changes of the Frank vectorcardiogram were continuously analysed with a new, highly precise vectorcardiographic method during, and immediately after a maximal exercise test. This was done in 18 young healthy males, and 18 patients with scintigraphic reversible ischaemia. During exercise, different patterns between the groups were noted for the changes in the mean QRS magnitude in the Y-lead (P less than 0.005), the QRS-integral (P less than 0.05), and the QRS-duration (P less than 0.05). Immediately after exercise, several QRS parameters in the normal group continued to change according to the same pattern as during exercise (P less than 0.05), which was in contrast with the patterns of the ischaemic group (P less than 0.01). The spatial ST difference at J+20 ms discriminated well between the groups, especially when corrected for QRS-magnitudes at rest and heart rate (P less than 0.0005). In short, this pilot study supports previous findings in that changes in amplitude and duration of the QRS complex during exercise discriminated between healthy young males and patients with ischaemic heart disease. Moreover, rapid discriminating changes were seen in the QRS segment during cessation of exercise. These changes deserve attention since they may be of importance for the conflicting results on the diagnostic value of QRS changes during exercise.

Coronary Disease↗
PubMed1991

Dynamic QRS-complex and ST-segment monitoring in acute myocardial infarction during recombinant tissue-type plasminogen activator therapy. The TEAHAT Study Group.

Changes of the QRS complex are the electrocardiographic expression of irreversible injury of the myocardium. In humans, the process of infarction occurs over several hours. A more rapid development of QRS changes has been reported in patients treated with thrombolytic agents. Patients with strongly suspected acute myocardial infarction (AMI) included in a placebo-controlled trial of 100 mg of recombinant tissue-type plasminogen activator (rt-PA) were monitored for 24 hours with continuous, on-line vectorcardiography. The magnitude of the QRS vector changes correlated with infarct size estimated by the maximal value of lactate dehydrogenase-1 (r = 0.69, p less than 0.001) as well as with left ventricular ejection fraction 30 days after randomization (r = 0.49, p less than 0.001). Treatment with intravenous rt-PA limited total QRS vector change but the QRS vector changes observed occurred more rapidly and reached a plateau 131 minutes earlier in patients treated with rt-PA than in those receiving placebo (p less than 0.01). A certain pattern of highly variable ST vector magnitude was identified and was associated with higher maximal lactate dehydrogenase-1 values (23 +/- 13 vs 14 +/- 10 mu kat/liter, p less than 0.001) and a tendency to higher 1-year mortality (24 vs 9%, p = 0.08) than in patients without this pattern. In patients with this pattern, rt-PA did not affect maximal lactate dehydrogenase-1, time to maximal creatine kinase and final magnitude of QRS vector change.

Double-Blind Method↗
PubMed1987

A computerized system for handling renal size measurements from urograms.

The size of a kidney, as measured on a urogram, is a sensitive indicator of renal damage in a child with urinary tract infection and renal surface area correlates well with glomerular filtration rate. Sequential measurements can be invaluable in evaluating the efficacy of a regimen of treatment. A system utilizing a personal microcomputer has been developed to facilitate the measuring procedure and the handling and analysis of data.

Adolescent↗
PubMed1980

Impedance cardiographic assessment of symptomatic patent ductus arteriosus.

A modified impedence cardiographic technique was developed using a tetrapolar apnea monitor and minicomputer system. Evaluation of this technique in premature infants with and without symptomatic patent ductus arteriosus indicates that the magnitude of the cardiac-related deflection in the impedance signal is useful in the assessment of ductus shunting. Since the infant under study is involved only by the attachment of two double electrodes to the thorax, continuous assessment of ductur shunting is possible without disturbing routine care.

Cardiography, Impedance↗
PubMed1977

Clinical application of evoked electroencephalographic responses in newborn infants. I: Perinatal asphyxia.

Evoked electroencephalographic responses are useful for the study of cerebral maturation in full-term and pre-term newborn infants. In an attempt to achieve wider clinical application, 57 newborn infants with differing degrees of perinatal asphyxia were examined. Altogether 154 examinations were performed. In all of them photostimulation was used, and in 72 investigations somatosensory evoked responses were also recorded. The following results were obtained: (1) Visual evoked responses were affected in 85 per cent of the cases. Somatosensory evoked responses were affected less often - in 65 per cent of the newborn babies examined. The incidence and degree of deviations were related to the degree of asphyxia. (2) The most characteristic features of the evoked responses in asphyxiated infants were abnormal response patterns, increase of latency and poor photic driving. (3) On the basis of all alterations observed, a scoring system was developed which enabled quantitative evaluation. The evoked response risk-score correlated well with the degree of asphyxia. (4) Repeated observations were important: a permanently high risk-score at repeated investigations was a serious prognostic sign.

Asphyxia Neonatorum↗