Electrocardiograph Tracings Research Articles

The effect of eye stimulation using graded external weights on the oculocardiac reflex in beagle dogs

The objective of this study was to determine to what extent the oculocardiac reflex (OCR) progressively rises with increasing external pressures over the superior eyelid. Controlled external weights were applied to the left eyelid of ten conscious healthy adult beagle dogs, using an electronic von Frey aesthesiometer with a modified probe. Four different weights (200 g, 300 g, 400 g and 800 g) were applied on four different non-consecutive days (with one-week intervals). Pressure was applied by pushing the device against the superior eyelid. The baseline heart rate was primarily recorded using an electrocardiograph (ECG). Then, indices of heart rate variability such as R-R intervals and vasovagal tonus index (VVTI) were calculated from the ECG tracings using twenty consecutive QRS complexes from each dog, before and after a selected set of graded weights were applied to the eye. Median R-R interval significantly increased when an external weight of 200 g was applied and peaked at 300 g. VVTI values peaked at 400 g. With higher pressures, the proportional increase was smaller in both R-R intervals and VVTI. We concluded that external eye pressure using a weight of 200 g or more is sufficient to elicit an OCR response in conscious dogs. Pressures above 400 g started to activate compensatory mechanisms that counteracted with the OCR, probably linked to an adrenergic response induced by the animal’s discomfort. Changes in R-R intervals might be used as an early OCR marker, while VVTI apparently was less influenced by potential sympathetic responses.

Diagnostic accuracy of a smartphone electrocardiograph in dogs: Comparison with standard 6-lead electrocardiography

The diagnostic accuracy of a smartphone electrocardiograph (ECG) in evaluating heart rhythm and ECG measurements was evaluated in 166 dogs. A standard 6-lead ECG was acquired for 1 min in each dog. A smartphone ECG tracing was simultaneously recorded using a single-lead bipolar ECG recorder. All ECGs were reviewed by one blinded operator, who judged if tracings were acceptable for interpretation and assigned an electrocardiographic diagnosis. Agreement between smartphone and standard ECG in the interpretation of tracings was evaluated. Sensitivity and specificity for the detection of arrhythmia were calculated for the smartphone ECG. Smartphone ECG tracings were interpretable in 162/166 (97.6%) tracings. A perfect agreement between the smartphone and standard ECG was found in detecting bradycardia, tachycardia, ectopic beats and atrioventricular blocks. A very good agreement was found in detecting sinus rhythm versus non-sinus rhythm (100% sensitivity and 97.9% specificity). The smartphone ECG provided tracings that were adequate for analysis in most dogs, with an accurate assessment of heart rate, rhythm and common arrhythmias. The smartphone ECG represents an additional tool in the diagnosis of arrhythmias in dogs, but is not a substitute for a 6-lead ECG. Arrhythmias identified by the smartphone ECG should be followed up with a standard ECG before making clinical decisions.

Revisiting ‘Measuring the process of solving clinical diagnostic problems’

Revisiting ‘Measuring the process of solving clinical diagnostic problems’

Twisted Leads: The Footprints of Malpositioned Electrocardiographic Leads

Malposition of electrocardiograph (ECG) leads is poorly recognised even by cardiologists who report tracings. When ECG tracings are regularly performed by doctors, nurses or technicians, lead malposition is very uncommon particularly if the operator can also interpret the findings. However, a significant proportion of 12-lead ECG tracings are today performed in a doctor's surgery or by private pathology services, often in haste without sufficient attention to correct lead positioning. As a result, a variety of malposition combinations occur, which in turn may confuse the interpreter of the ECG tracing, leading to incorrect diagnoses. To investigate various combinations of ECG lead malposition and determine if characteristic findings can be summarised into identifiable footprints. In 10 normal subjects, 12-lead ECGs were performed with normal lead positioning as well as six limb lead malpositions and reversal of chest leads. In all subjects, there was consistency in the ECGs performed allowing the creation of five characteristic and easily identifiable footprints. A summary of the footprints of ECG lead malposition should be readily available for those who perform ECGs, those who interpret the tracings and those responsible for clinical care.

Electrocardiograma en edad pediátrica

A properly interpreted electrocardiogram (ECG) provides important information and is an inexpensive and easy test to perform. It continues to be the method of choice for the diagnosis of arrhythmias.Although the principles of cardiac electrophysiology are the same, there are anatomical and physiological age-dependent changes which produce specific alterations in the paediatric ECG, and which may be misinterpreted as pathological.The intention of this article is to address in a systematic way the most relevant aspects of the paediatric ECG, to propose a possible reading scheme of the ECG and to review the electrocardiograph tracings most frequently found in the paediatric age group.

Estimation of parasympathetic nerve function during sleep in patients with obstructive sleep apnea by instantaneous time–frequency analysis

Background and objectivesThe pathophysiologic aspects of parasympathetic nerve (PN) function during sleep in patients with obstructive sleep apnea (OSA) studied by classical power spectrum analysis on heart rate variability (HRV) are highly controversial. The controversy is attributed to methodologic concerns, such as poor time resolution involved in power spectrum analysis. We aimed to establish the appropriate method for the investigation of PN function in OSA patients with apneas and hypopneas using instantaneous time–frequency analysis with complex demodulation (CD) and sufficient time resolution. MethodsA total of 30 patients with PSG-confirmed mild to severe OSA were recruited for the analysis of frequency spectra contained in R-R intervals (RRI) of overnight electrocardiograph (ECG) tracings. High-frequency (HF) domains ranging between 0.15 and 0.40Hz were selected for analysis. Among these domains, the HF domain with the maximum instantaneous amplitude was defined as the main HF peak and was used as the surrogate marker of PN discharge. Based on density spectrum array (DSA) map for main HF peak constructed with a time scale of 1s and a frequency resolution of 0.002Hz (HF-DSA map), the shift in central frequency (CF) of main HF peak over time was continuously monitored. When the main HF peak with the same CF lasted for more than 20s or 5min on HF-DSA map, the PN function was considered to be stable or very stable. The measurements were then repeated after continuous positive airway pressure (CPAP) treatment. ResultsThe extent of PN-evoked modulation of RRI was enhanced in nonrapid eye movement (NREM) sleep, though the stability was reduced in both NREM and rapid eye movement (REM) sleep. These peculiar behaviors of PN function were reversed by CPAP treatment. ConclusionWe found that instantaneous time–frequency analysis allowed estimation of transitional changes in PN function during sleep in OSA patients.

Disruption to Recovery Metabolism in the Fence LizardSceloporus occidentalisInfected with the Malarial ParasitePlasmodium mexicanum

Abstract Western Fence Lizards, Sceloporus occidentalis, are frequently parasitized by the malaria-causing protozoan Plasmodium mexicanum, reducing hemoglobin concentrations, increasing reliance on anaerobic metabolism, and elevating the cost of recovery. We examined the influence of malarial infections in Fence Lizards on aerobic capacity, blood metabolites, and cardiopulmonary activity following activity (<2 min of maximal activity) on a treadmill at 35.0 ± 1.0°C. Aerobic capacity was determined from resting and maximal oxygen uptake. Blood glucose and lactate were measured before activity and at 15 min intervals during 60 min of recovery. Heart rate and ventilation rate were determined from electrocardiograph tracings. Maximal aerobic capacity was over 35% higher in uninfected lizards compared to both malaria-infected lizards and anemic-uninfected animals. Malarial infection decreased lizard resting blood glucose levels, yet induced hyperglycemia during recovery; blood glucose levels were elevated by a...

Hickam 2000: The maturation of, and linkages between, medical informatics and bioinformatics

I have always been infatuated with computers and convinced of their potential for solving problems in biologic research and clinical care. In the 1960s I thought we could use the computer to predict the shape of macromolecules from their chemical formulas and fundamental physical chemical principles. However, with the computers of the 1960s that was a fantasy. So I focused on the use of computers to manage medical record content and to assist with clinical care. The Electronic Medical Record (EMR) we began developing in 1972 with 33 diabetes patients now carries nearly 300 million separate results for more than 3 million patients. The data include lab and other diagnostic studies, dictated notes, orders, encounter records, radiology images, electrocardiograph tracings, and motion cardiac echoes, and the care provider at Indiana University and Wishard Hospital is accessed 10 million times per year. We have also agitated for standards to make the collection of these data easier. This work has become part of a field called medical informatics. In the meantime, the application of computers to biology has rapidly matured into a field called bioinformatics, and researchers in this field now provide annotated databases for many categories of molecules, programs for “matching” newly discovered genomic sequences with previously studied sequences, and systems for storing and processing massive amounts of genomic and molemic data. They have developed sophisticated methods for predicting the shape of biologic macromolecules and other important insights about biology and evolution. Medical informatics and bioinformatics intersect at many points. The most important intersection is between electronic medical records and the human specimen databases that can link genotype to the phenotype, as needed, to unravel polygenetic disease causality. The National Cancer Institute is embarking on an intriguing effort to use EMRs (phenotype) to link to paraffin blocks (genotype) in pathology laboratories where opportunities for cancer genomic discovery are open. We will participate in this effort and look forward to bending the EMR we developed for clinical use to bioinformatics uses as well. (J Lab Clin Med 2001;138: 359-66)

Heart rate responses to deep breathing and 4-seconds of exercise before and after pharmacological blockade with atropine and propranolol.

Two autonomic tests which evaluate cardiac vagal activity, the respiratory sinus arrhythmia and the newer 4-second exercise test, have been compared. From electrocardiograph tracings, respiratory sinus arrhythmia was quantified by the ratio between the longest R-R interval during expiration and the shortest one during inspiration (E/I ratio), and the 4-second exercise test by the ratio between the last R-R interval before and the shortest one during exercise (B/C ratio). In 29 healthy subjects there was a correlation (R = 0.60, p less than 0.05) between the responses to the two tests. In a group of six healthy subjects the same tests were performed after autonomic blockade with intravenous atropine and/or propranolol. The heart rate rise during the 4-second exercise test was nearly abolished by atropine (mean +/- SD) (B/C: control = 1.53/0.33; after atropine = 1.04/0.03), whereas RSA was diminished to a lesser extent (E/I: control = 1.59/0.24; after atropine = 1.13/0.07). beta-adrenoceptor blockade did not affect the test ratios (after propranolol: B/C = 1.51/0.33 and E/I = 1.45/0.14). Successive tests during the following hour after atropine infusion showed a somewhat faster recovery of the respiratory sinus arrhythmia than the heart rate acceleration induced by the 4-second exercise test (p less than 0.05). We conclude that there may be some difference in the mechanisms which contribute to the heart rate changes in these two autonomic cardiovascular tests; these remain to be clarified. The 4-second exercise test may be an alternative to the respiratory sinus arrhythmia test in the non-invasive evaluation of cardiac parasympathetic activity.

Physiological Changes in Middle-Aged Men following a Ten-Week Jogging Program

Abstract Twenty-one middle-aged males who participated in a jogging program performed a 6-minute submaximal exercise bout on a bicycle ergometer to determine if any differences existed between the results of heart rate and blood pressure tests taken before and after 10 weeks of training. Heart rates were obtained from electrocardiograph tracings and blood pressures were measured by a manual sphygmomanometer. The t test for differences between the means of related measures of heart rates and blood pressures was used with the .01 level selected for significance. Differences between the means of pre-and post tests of heart rate, under pre-exercise, submaximal exercise, and postexercise conditions, were all statistically significant. The jogging program did not produce any significant change in either systolic or disastolic blood pressure. It was concluded that 10 weeks of participation in a systematic jogging program will produce reductions in heart rates for middle-aged men at rest, during submaximal exerci...

The elimination from the electrocardiogram of the effects of alternating current of power and lighting lines

Information is presented which, it is believed, should prove of value in eliminating, from electrocardiograph tracings, the effects of disturbances from electric lighting and power circuits. The direct cause of the disturbance was found to consist in certain defective electric motors or similar devices receiving current from the same lines as the building in which the electrocardiograph is situated. The solution of the problem lies in the location and repair or elimination of the defective machines.