QRS Amplitude Research Articles

Concurrent atrioventricular block, sinus arrest and pneumothorax in a dog secondary to vehicle accident

Summary In human several kinds of electrocardiographic findings have been reported in association with pneumothorax such as decreased and/or alternating QRS amplitude (electrical alternans). However, electrocardiographic changes concurrent with pneumothorax have rarely been discussed in veterinary literature. A 3-year-old male crossbreed dog was presented with a history of car accident. Thoracic auscultation revealed decreased lung sounds. Heart sounds were also markedly muffled bilaterally. An electrocardiogram revealed sinus arrest in association with first degree atrioventricular block. Pneumothorax was the main finding in thoracic radiographs. Seven days after initial admission, thoracic radiographs revealed that pnuemothorax was resolved and all electrocardiographic abnormalities returned to normal limits.

Effects of breath-holding position on the QRS amplitudes in the routine electrocardiogram

Background The effects of different breath-holding positions during electrocardiographic (ECG) recording on the QRS complex are unknown. Methods In 73 subjects, ECG recordings were made in 3 different breath-holding positions: normal expiration (rest), maximum inspiration, and maximum expiration. QRS wave excursions and changes in the frontal electrical heart axis were analyzed. Results The mean effect of respiration in most leads was small (≥1 mm only in the S wave in V 4 and in the R wave in V 5), but the degree of interindividual variability was often substantial, with standard deviations of ≥1.5 mm in multiple leads. Conclusion The effect of different extreme breath-holding positions on the QRS complex is on average small but may be substantial in individuals. Lack of standardization of breathing instructions during recording of the ECG may result in differences in application of amplitude criteria and poorer reproducibility.

The decrease in QRS amplitude after aortic valve replacement in patients with aortic valve stenosis

Purpose The purpose of this study was to evaluate the effect of aortic valve replacement on electrocardiogram (ECG) in patients with aortic valve stenosis. Methods Serial 12-lead ECGs were obtained in 15 patients with aortic valve stenosis who underwent aortic valve replacement. Three ECG indexes for left ventricular hypertrophy were manually measured in each ECG: Sokolow-Lyon index (sum of S wave in V 1 and R wave in V 5), Cornell voltage index (sum of R wave in aVL and S wave in V 3), and Gubner index (sum of R wave in I and S wave in III). Results After aortic valve replacement, Sokolow-Lyon index gradually decreased during 2 years (51.1 ± 17.9 to 34.8 ± 12.5 mm, P < .01). Cornell voltage index (25.6 ± 7.0 to 15.0 ± 4.8 mm, P < .01) and Gubner index (15.8 ± 7.6 to 10.3 ± 5.5 mm, P < .01) also gradually decreased during 2 years. ST depression in V 6 was found in 14 patients (93%) before aortic valve replacement. It resolved in 9 of 14 patients during 2 years. Conclusions Electrocardiographic evidence of left ventricular hypertrophy gradually resolved after aortic valve replacement in patients with aortic valve stenosis.

Principal Component Analysis as a Tool for Analyzing Beat-to-Beat Changes in ECG Features: Application to ECG-Derived Respiration

An algorithm for analyzing changes in ECG morphology based on principal component analysis (PCA) is presented and applied to the derivation of surrogate respiratory signals from single-lead ECGs. The respiratory-induced variability of ECG features, P waves, QRS complexes, and T waves are described by the PCA. We assessed which ECG features and which principal components yielded the best surrogate for the respiratory signal. Twenty subjects performed controlled breathing for 180 s at 4, 6, 8, 10, 12, and 14 breaths per minute and normal breathing. ECG and breathing signals were recorded. Respiration was derived from the ECG by three algorithms: the PCA-based algorithm and two established algorithms, based on RR intervals and QRS amplitudes. ECG-derived respiration was compared to the recorded breathing signal by magnitude squared coherence and cross-correlation. The top ranking algorithm for both coherence and correlation was the PCA algorithm applied to QRS complexes. Coherence and correlation were significantly larger for this algorithm than the RR algorithm(p < 0.05 and p < 0.0001, respectively) but were not significantly different from the amplitude algorithm. PCA provides a novel algorithm for analysis of both respiratory and nonrespiratory related beat-to-beat changes in different ECG features.

Case Report: Escherichia coli Septic Shock Masquerading as ST-Segment Elevation Myocardial Infarction

Elevated cardiac biomarkers in conjunction with electrocardiographic (ECG) changes are valuable in diagnosing acute coronary syndrome (ACS). Elevated troponin I (TnI), while commonly seen in ACS, can also occur in entities such as sepsis and pulmonary thromboembolic disease. Raised TnI levels in patients with sepsis result from various mechanisms, including hypoperfusion or direct extension of infection to cardiac tissue, and can also serve as an important prognostic indicator. Electrocardiographic changes in sepsis are not as well described. Some of the ECG findings associated with septic shock include loss of QRS amplitude, increase in QTc interval, bundle branch blocks, and development of narrowed QRS intervals with deformed, positively deflected J waves (commonly known as Osborn waves). ST-segment elevations in sepsis are rare and have only previously been noted in a handful of case reports involving patients with septic shock. We present a case of a 59-year-old woman with ST-segment elevations and increased levels of cardiac troponin from Escherichia coli septic shock in the setting of normal coronary angiography.

Support Vector Machines for Automated Recognition of Obstructive Sleep Apnoea Syndrome from Electrocardiogram Recordings

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular morbidity as well as excessive daytime sleepiness and poor quality of life. In this study, we apply a machine learning technique [support vector machines (SVMs)] for automated recognition of OSAS types from their nocturnal ECG recordings. A total of 125 sets of nocturnal ECG recordings acquired from normal subjects (OSAS<formula formulatype="inline"><tex Notation="TeX">${-}$</tex> </formula>) and subjects with OSAS (OSAS<formula formulatype="inline"><tex Notation="TeX">${+}$</tex></formula>), each of approximately 8 h in duration, were analyzed. Features extracted from successive wavelet coefficient levels after wavelet decomposition of signals due to heart rate variability (HRV) from RR intervals and ECG-derived respiration (EDR) from R waves of QRS amplitudes were used as inputs to the SVMs to recognize OSAS<formula formulatype="inline"> <tex Notation="TeX">${+/-}$</tex></formula> subjects. Using leave-one-out technique, the maximum accuracy of classification for 83 training sets was found to be 100% for SVMs using a subset of selected combination of HRV and EDR features. Independent test results on 42 subjects showed that it correctly recognized 24 out of 26 OSAS <formula formulatype="inline"><tex Notation="TeX">${+}$</tex></formula> subjects and 15 out of 16 OSAS<formula formulatype="inline"> <tex Notation="TeX">${-}$</tex></formula> subjects (accuracy <formula formulatype="inline"><tex Notation="TeX">${=}$</tex></formula> 92.85%; Cohen's <formula formulatype="inline"><tex Notation="TeX">$\kappa$</tex></formula> value of 0.85). For estimating the relative severity of OSAS, the posterior probabilities of SVM outputs were calculated and compared with respective apnea/hypopnea index. These results suggest superior performance of SVMs in OSAS recognition supported by wavelet-based features of ECG. The results demonstrate considerable potential in applying SVMs in an ECG-based screening device that can aid a sleep specialist in the initial assessment of patients with suspected OSAS. </para>

Support Vector Machines for Automated Recognition of Obstructive Sleep Apnea Syndrome From ECG Recordings

Obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular morbidity as well as excessive daytime sleepiness and poor quality of life. In this study, we apply a machine learning technique [support vector machines (SVMs)] for automated recognition of OSAS types from their nocturnal ECG recordings. A total of 125 sets of nocturnal ECG recordings acquired from normal subjects (OSAS - ) and subjects with OSAS (OSAS +), each of approximately 8 h in duration, were analyzed. Features extracted from successive wavelet coefficient levels after wavelet decomposition of signals due to heart rate variability (HRV) from RR intervals and ECG-derived respiration (EDR) from R waves of QRS amplitudes were used as inputs to the SVMs to recognize OSAS +/- subjects. Using leave-one-out technique, the maximum accuracy of classification for 83 training sets was found to be 100% for SVMs using a subset of selected combination of HRV and EDR features. Independent test results on 42 subjects showed that it correctly recognized 24 out of 26 OSAS + subjects and 15 out of 16 OSAS - subjects (accuracy = 92.85%; Cohen's kappa value of 0.85). For estimating the relative severity of OSAS, the posterior probabilities of SVM outputs were calculated and compared with respective apnea/hypopnea index. These results suggest superior performance of SVMs in OSAS recognition supported by wavelet-based features of ECG. The results demonstrate considerable potential in applying SVMs in an ECG-based screening device that can aid a sleep specialist in the initial assessment of patients with suspected OSAS.

Increased beat-to-beat ‘ R’ amplitude variability in patients with panic disorder

In patients with panic disorder, an anxiety disorder, isoproterenol increases beat-to-beat QRS amplitude variability much more than in normal controls. In this pilot study, we found that patients with panic disorder had significantly higher beat-to-beat QRS amplitude variability compared to controls in resting supine and standing postures. This may be partly due to myocardial electrical instability or irregular respiration in this patient group. These findings are important in view of the association between panic disorder and increased cardiovascular mortality.

Pleiotropic effects in Eya3knockout mice

BackgroundIn Drosophila, mutations in the gene eyes absent (eya) lead to severe defects in eye development. The functions of its mammalian orthologs Eya1-4 are only partially understood and no mouse model exists for Eya3. Therefore, we characterized the phenotype of a new Eya3 knockout mouse mutant.ResultsExpression analysis of Eya3 by in-situ hybridizations and β-Gal-staining of Eya3 mutant mice revealed abundant expression of the gene throughout development, e.g. in brain, eyes, heart, somites and limbs suggesting pleiotropic effects of the mutated gene. A similar complex expression pattern was observed also in zebrafish embryos.The phenotype of young adult Eya3 mouse mutants was systematically analyzed within the German Mouse Clinic. There was no obvious defect in the eyes, ears and kidneys of Eya3 mutant mice. Homozygous mutants displayed decreased bone mineral content and shorter body length. In the lung, the tidal volume at rest was decreased, and electrocardiography showed increased JT- and PQ intervals as well as decreased QRS amplitude. Behavioral analysis of the mutants demonstrated a mild increase in exploratory behavior, but decreased locomotor activity and reduced muscle strength. Analysis of differential gene expression revealed 110 regulated genes in heart and brain. Using real-time PCR, we confirmed Nup155 being down regulated in both organs.ConclusionThe loss of Eya3 in the mouse has no apparent effect on eye development. The wide-spread expression of Eya3 in mouse and zebrafish embryos is in contrast to the restricted expression pattern in Xenopus embryos. The loss of Eya3 in mice leads to a broad spectrum of minor physiological changes. Among them, the mutant mice move less than the wild-type mice and, together with the effects on respiratory, muscle and heart function, the mutation might lead to more severe effects when the mice become older. Therefore, future investigations of Eya3 function should focus on aging mice.

Body mass index and the relationship between QRS amplitude and left ventricular mass in hypertensive patients and patients with metabolic syndrome

minutes). A statistical classifier was developed to detect AF based on RR interval irregularity and inconsistency in P-wave location and morphology. The algorithm was trained using 633 ambulatory Holter recordings. The 48 prospective recordings were used only for testing. The algorithm determined if the patient had any AF (primary diagnostic) and quantified the amount of AF (monitoring). A patient was assumed to have AF burden if more than 10 minutes per day of the ECG was AF. For ECGs not 24 hours long, this is equivalent to being in AF for more than 0.69% of the record length. Results: Atrial fibrillation burden was detected on all 10 patient records (sensitivity of 100%) with 9 of 10 AF burden values within 10% of the true value. Average duration sensitivity and specificity, which represent the ability to measure true AF and reject non-AF periods, were 98.8% and 99.7%, respectively. Conclusion: We have described a highly sensitive and accurate method for the assessment of AF burden using a miniaturized prototype ECG recorder with a novel AF detection algorithm. Using this device potentially increases patient comfort and compliance for long-term AF monitoring compared to Holter systems. It may be possible to enhance the algorithm further by finding the optimum location for the device placement and using devicespecific data to train the algorithm.

Features of an exceptionally narrow QRS data set

Background Little attention has been directed to the characteristics of electrocardiograms (ECGs) with brief QRS durations (BD). Methods From a database of 859 977 computer-analyzed (Marquette 12SL, GE Healthcare, Milwaukee, WI, USA) ECGs of 216 148 patients, 1805 patients (data set of BD: 19 718 ECGs; age, >18 years, unpaced), had, in at least one ECG, a QRS duration of less than 62 milliseconds, a prevalence of 0.8%. Results The QRS duration ranged from 46 to 188 milliseconds; values fluctuated between excessive brevity and the traditionally normal (80-95 milliseconds), with many values in the 60's. The average age at first acquisition was 56 years (range, 18-96 years); 1371 were female (76%) and 433 were males (24%); and 416 were white (23%), 1243 African American (69%), 109 other (6%). The summed 12-lead QRS amplitude (ΣQRS) ranged from 2800 to 32 929 μV (mean ± SD, 11 154 ± 4101), and heart rate ranged from 40 to 269 (98 ± 26). There was a statistically positive relationship between QRS duration (in the range 52-105 milliseconds) and ΣQRS ( P < 0001): for each 1000 μV increment, duration increased by 0.7 milliseconds (95% confidence interval [CI], 0.66-0.73 milliseconds). Conversely, for each 5-millisecond increment in duration, ΣQRS increased by 475 μV (95% CI, 450-498 μV). There was an inverse relationship between QRS duration and heart rate ( P < .0001): for every 10 beat rate increase, the duration dropped by 1.14 milliseconds (95% CI, 1.09-1.19 milliseconds). An additional data set of normal QRS durations ND consisted of 2902 subjects, none of whose 40 327 ECGs showed a QRS duration less than 62 milliseconds; 2.8% of ND ECGs had durations in the 62–69 millisecond range, 26% in BD. Sinus tachycardia was 43% in BD and 24% in ND. The average age of ND was 58 years (range, 18-100 years); 44% were male and 56% female; and 39% were white and 57% were African American. A positive relationship between duration and amplitude was found among ND subjects as well: for each 1000 point increase in ΣQRS, duration increased by 0.45 milliseconds ( P < .0001; 95% CI, 0.42-0.47 milliseconds). The duration amplitude relationship did not hold for durations greater than 105 milliseconds in either data set. Conclusion Over the full extended span of QRS durations (46-106 milliseconds), the value of the latter is directly related to the total summed amplitude of the 12-lead QRS. An inverse relationship is demonstrable with heart rate.

Effects of limb electrode placement on the 12- and 16-lead electrocardiogram

The effects of three common limb electrode placement configurations on ECG signal morphology were examined, including the standard electrode placement of the electrodes on the extremities, the Mason-Likar placement, and the Lund placement. A non-traditional asymmetric configuration of placing the LA electrode on the upper arm with the RA electrode on the torso (below the clavicle) was also investigated. A series of 16-lead ECGs were acquired from 150 subjects representing a broad range of diseases. Effects of the limb electrode placement on axis measurements, QRS amplitudes, ST levels, and infarctions were studied. On average, the P, QRS, and T axes all exhibited rightward shifts as the electrodes were moved away from the extremities, but more generally, the axis became more vertical, with the largest shifts occurring when the standard ECG axis measurement was close to 0 degrees and tending to exhibit leftward shifts for ECGs with a standard axis measurement between 0 and –90 degrees. Voltage changes were consistent with axis shifts in the frontal plane (decreased lateral and increased inferior lead voltages), with the largest mean change a reduction in R wave amplitude of lead I going from the standard to the Mason-Likar configuration. In the precordial leads, Q and/or S magnitudes decreased in right-sided leads (V4r, V1, V2, V3) and R magnitudes increased in lateral leads (V3 – V9) as the arm electrodes moved toward the trunk, suggesting a posterior shift in the mean QRS axis. ST deviations in the lateral and posterior precordial leads tended to be mimicked in lead III when the electrodes were moved from the extremities to the torso. Over half (13 of 25) of the ECGs exhibiting criteria for inferior infarct in the standard configuration had that criteria erased when the electrodes were moved to the Mason-Likar positions. The largest single effect on the ECG resulted from moving the LA electrode from the shoulder to the clavicle. The asymmetric configuration with the RA electrode on the torso and the LA electrode on the upper arm may offer some compromise between noise and faithfulness to the standard configuration in noisy environments such as exercise testing or monitoring.

Electrocardiography of Grevy's Zebras (Equus grevyi)

Electrocardiograms (ECGs) are a good baseline test for assessing cardiac rhythm. ECGs have not been reported in any zebra species and in very few Perissodactyla species. Standard limb, six-lead ECGs were recorded in 23 anesthetized Grevy's zebras (Equus grevyi). Heart rate, RR interval, P-wave duration, RR maximum/minimum, PR interval, QRS duration, QT interval, ST segment deviation, P-wave amplitude, QRS amplitude, and T-wave amplitude were measured and calculated from lead II ECGs from these Grevy's zebras. Several variables were tested, including gender, age (0-24, 24-48, 48-180, and >180 mo), weight (<350 kg or >350 kg), pregnancy status, and anesthetic differences (standard dose or supplemented dose), to see if they affected ECG values in these animals. There were no significant differences in any of the ECG parameters between genders. RR and QT intervals were longer in older zebras; heart rates were faster in younger zebras. The RR and PR intervals, as well as the QRS duration, were greater in heavier zebras; heart rates were faster in lighter zebras. The RR interval was significantly longer in pregnant zebras. There were no significant differences in any of the ECG parameters for zebras anesthetized with a standardized dose of the drug combination etorphine-detomidine-acepromazine compared to those receiving additional supplements of these drugs and/or ketamine. All other parameters were not significantly different among groups, except where noted previously. The results of this research indicate that differences in ECG parameters in zebras may occur between animals of different ages, weights, and pregnancy status and that these factors should be considered when interpreting the respective ECGs of these zebras.

Online Digital Filter and QRS Detector Applicable in Low Resource ECG Monitoring Systems

The present work describes fast computation methods for real-time digital filtration and QRS detection, both applicable in autonomous personal ECG systems for long-term monitoring. Since such devices work under considerable artifacts of intensive body and electrode movements, the input filtering should provide high-quality ECG signals supporting the accurate ECG interpretation. In this respect, we propose a combined high-pass and power-line interference rejection filter, introducing the simple principle of averaging of samples with a predefined distance between them. In our implementation (sampling frequency of 250 Hz), we applied averaging over 17 samples distanced by 10 samples (Filter10x17), thus realizing a comb filter with a zero at 50 Hz and high-pass cut-off at 1.1 Hz. Filter10x17 affords very fast filtering procedure at the price of minimal computing resources. Another benefit concerns the small ECG distortions introduced by the filter, providing its powerful application in the preprocessing module of diagnostic systems analyzing the ECG morphology. Filter10x17 does not attenuate the QRS amplitude, or introduce significant ST-segment elevation/depression. The filter output produces a constant error, leading to uniform shifting of the entire P-QRS-T segment toward about 5% of the R-peak amplitude. Tests with standardized ECG signals proved that Filter10x17 is capable to remove very strong baseline wanderings, and to fully suppress 50 Hz interferences. By changing the number of the averaged samples and the distance between them, a filter design with different cut-off and zero frequency could be easily achieved. The real-time QRS detector is designed with simplified computations over single channel, low-resolution ECGs. It relies on simple evaluations of amplitudes and slopes, including history of their mean values estimated over the preceding beats, smart adjustable thresholds, as well as linear logical rules for identification of the R-peaks in real-time. The performance of the QRS detector was tested with internationally recognized ECG databases (AHA, MIT-BIH, European ST-T database), showing mean sensitivity of 99.65% and positive predictive value of 99.57%. The performance of the presented QRS detector can be highly rated, comparable and even better than other published real-time QRS detectors. Examples representing some typical unfavorable conditions in real ECGs, illustrate the common operation of Filter10x17 and the QRS detector.

Effects of mechanical ventilation on the electrocardiogram in adults.

The effects of mechanical ventilation on the surface electrocardiogram (ECG) have not been systematically investigated and the anticipated changes such as rightward P and QRS axes shifts, reduced QRS voltage, and slow R-wave progression are not supported by definitive data. We sought to determine the effects of mechanical ventilation on the surface ECG in hemodynamically stable adults without active cardiopulmonary disease. Seventeen patients in good overall health who were undergoing elective outpatient surgery had serial ECGs done preoperatively, intraoperatively, and postoperatively. No clinically significant changes in QRS or P-wave axis were detected. R-wave progression was not altered and there were no significant differences in the QRS amplitudes pre-, intra-, or postoperatively in either the precordial or limb leads. The present study shows that hemodynamically stable patients without active cardiopulmonary disease undergoing elective surgery demonstrate relatively minor ECG changes from baseline despite the addition of positive pressure ventilation. Clinicians should not assume that substantial changes in P wave or QRS axis or amplitude in patients undergoing mechanical ventilation are due to the effects of positive pressure ventilation alone.

Standardizing electrocardiographic leads: introduction to a symposium

Since Einthoven introduced the string galvanometer in 1902, electrocardiography has evolved as one of the most widely used tests in the practice of medicine. The routine 12-lead electrocardiogram (ECG), comprising limb leads, augmented frontal plane leads, and precordial leads, has been standardized for half a century. Routine electrocardiography is a fundamental tool for establishing cardiac rhythm and for the diagnosis of acute and chronic diseases of the heart. Comparison of serial ECGs is important in clinical decision making, and this requires technical consistency to minimize nonbiologic variability. Important elements of technical consistency include choice of leads and accuracy of electrode placement. To identify Q waves of prior myocardial infarction and to quantify QRS amplitudes to diagnose ventricular hypertrophy, proper lead placement of the standard electrodes can be extremely important. Electrode placement can have a profound effect on the quantitative variability of serial ECG findings. For example, to evaluate changing ST-segment deviation in patients with acute coronary syndromes, consistent electrode placement is essential. For most rhythm diagnoses, precise lead placement is less critical, but electrode placement is important when QRS morphology is used to determine whether a wide QRS complex tachycardia is ventricular tachycardia or supraventricular tachycardia with aberrancy or bundle branch block. Before the modern era of acute coronary care and hospital-based monitoring and telemetry, nearly all ECGs recorded in the course of practice used a standard 12-lead electrode array that evolved by empirical consensus in the 1930s and 1940s. Early exercise tests conducted with the master 2-step protocol used supine limb lead tracings recorded before and after effort, but exceptions began to occur in the last third of the 20th century when bipolar torso electrodes were introduced to allow activity-compatible

Electrocardiogram voltage discordance: interpretation of low QRS voltage only in the limb leads

Introduction Low voltage on the surface electrocardiogram (ECG) is defined as QRS voltage less than 5 mm in all limb leads and less than 10 mm in all precordial leads. The clinical correlate of an ECG with low voltage in the limb leads but normal precordial QRS amplitudes is unclear. Methods Twelve-lead ECGs with QRS voltage less than 5 mm in all limb leads and more than 10 mm in at least 2 contiguous precordial leads were collected. Presence of clinical conditions associated with low voltage was determined from clinical data and chest imaging. Results Fifty-one of 100 patients had voltage discordant ECGs that correlated with conditions known to cause diffuse low voltage. Among those without associated conditions, 63% had dilated ventricles, with an average ejection fraction of 33%. Conclusions Low voltage isolated to the limb leads is associated with the same conditions that cause diffuse low voltage in only half of patients. In the remainder, more than 60% have dilated cardiomyopathies.

Blood Pressure and Electrocardiographic changes During Face Immersion in Water in Young Men on Regular Exercise

The cardiovascular responses in non-exercising and regularly exercising young men (22.0-32.0 yr) to breath-holding and face immersion in water at 210C or 400C is reported. The possibility of a myocardial oxygen conserving effect of face immersion in water is also investigated. Blood Pressure (BP) and electrocardiographic (ECG) measurements were made at the same time with the subject standing, neck flexed and immersed in water with the breath held. Results show that in both groups of subjects face immersion in water (at either temperature) with breath-hold significantly increased BP, QRS amplitude, PR interval, QT interval and R-R interval. Face immersion thus caused a significant reduction in heart rate (HR). However, in both groups of subjects, the changes in BP and HR due to face immersion at 210C were greater than the changes brought about by face immersion at 400C. The rate-pressure product (RPP) or myocardial oxygen demand fell by the same amount in the two groups of subjects at 400C. At 210C, the fall in myocardial oxygen demand was significantly greater in exercising subjects than in non-exercising subjects (p

Cardiac and autonomic responses to change in posture or vitamin C supplementation in sickle cell anemia subjects

Autonomic function following change in posture with or without vitamin C supplementation was studied in ten (10) sickle cell anemia (SCA) and twelve (12) non-sickle cell anemia (NSCA) subjects. Arterial blood pressure and electrocardiographic measurements were taken in the supine position on a couch 80 cm high and immediately on assumption of the upright position. Vitamin C was then administered orally (300 mg/day for 6 weeks). At the end of the period, blood pressure and ECG measurements were again made in the supine position and in response to change in posture. Change in posture significantly decreased QRS amplitude, QRS duration, PR interval, RR interval and MABP but increased HR and rate pressure product (RPP) in both groups of subjects. The HR and RPP responses were significantly higher in NSCA than in SCA subjects ( p < 0.001, respectively). Vitamin C caused greater reductions in QRS duration ( p < 0.01), PR duration p < 0.001) in the NSCA subjects than in SCA subjects. It caused, however, greater reduction in RR duration ( p < 0.001) and MABP in SCA subjects than in NSCA subjects. It also caused significantly greater increases in HR and RPP ( p < 0.001, respectively) in the SCA subjects than in NSCA subjects. After vitamin C supplementation, change in posture decreased RR interval ( p < 0.001), QT interval ( p < 0.01) and MABP ( p < 0.05) but increased RPP ( p < 0.01) in NSCA subjects. In SCA subjects, there was a fall in RR interval ( p < 0.001) and MABP ( p < 0.01), but elevated RPP ( p < 0.001). Changes (Δ) in MABP, HR and RPP were similar between NSCA and SCA subjects. In conclusion, these findings indicate a blunted cardiovascular autonomic response to change in posture in sickle cell anemia subjects. Chronic, oral, low-dose vitamin C supplementation equilibrates this response with those of non-sickle cell anemia subjects.

Early stage of hypertrophy development in spontaneously hypertensive rats is characterized by decrease in QRS amplitude and attenuated expression of connexin 43

Early stage of hypertrophy development in spontaneously hypertensive rats is characterized by decrease in QRS amplitude and attenuated expression of connexin 43