Evaluation of six-lead electrocardiograms obtained from dogs in a sitting position or sternal recumbency

OBJECTIVE: To compare 6-lead ECG traces in clinically normal conscious dogs in a sitting position and sternal recumbency to that of right lateral recumbency. ANIMALS: 31 healthy dogs with no history of cardiac disease. PROCEDURE: Six-lead ECGs were recorded for dogs in right lateral recumbency, a sitting position, and sternal recumbency. Q-, R-, and S-wave amplitudes as well as QRS-complex duration were measured in all leads. Additionally, P-wave amplitude and duration, PR interval, ST-segment elevation or depression, and OT interval were measured in lead II. RESULTS: Compared with measurements in right lateral recumbency, the sitting position resulted in increased Q-wave amplitude (lead III), increased R-wave amplitude (leads I and aVL), decreased R-wave amplitude (leads III and aVF), increased S-wave amplitude (lead aVR), decreased S-wave amplitude (lead aVL), increased P-wave amplitude (lead II), and a leftward shift in the mean electrical axis. Compared with measurements in right lateral recumbency, sternal recumbency resulted in decreased Q-wave amplitude (leads I, II, and aVF), increased R-wave amplitude (leads 11, III, and aVF), decreased R-wave amplitude (lead aVR), increased S-wave amplitude (lead aVR), increased P-wave amplitude (lead II), and decreased ST-segment depression (lead II). Compared with right lateral recumbency, the sitting position or sternal recumbency did not result in significant differences in PR interval, QT interval, or QRS-complex duration. CONCLUSIONS AND CLINICAL RELEVANCE: Significant changes are found in ECG measurements in the sitting position and sternal recumbency, compared with right lateral recumbency. In dogs, many ECG reference range values for right lateral recumbency are not valid for ECGs obtained in the sitting position or sternal recumbency.     

Effect of body position on feline electrocardiographic recordings

The aim of this study was to determine whether changes in body position alter feline electrocardiographic parameters. Forty-seven cats referred to the Feline Unit of the University of Bristol had electrocardiograms (ECGs) recorded. Only cats presenting in sinus rhythm were included in the study (n = 41). ECGs were recorded either as part of the investigation for potential cardiac disease (n = 38) or as a preanesthetic screen (n = 3). Standard 6-lead ECGs (leads I, II, III, aVR, aVL, and aVF) were recorded in 3 different recumbent positions in the 41 cats. Recordings were 1st made in right lateral (RL) recumbency, followed by sternal (ST) and then left lateral (LL) recumbency. Measurements were taken of the amplitude and duration of P waves and QRS complexes and duration of PQ and QT intervals from lead II was taken in the 3 different positions. Mean electrical axis (MEA) also was calculated. Repeated measures analysis of variance was performed and identified a significant difference in R wave amplitudes (P = .009) and MEA (P = .037) among the 3 different body positions. Two-tailed paired t-tests demonstrated that the R wave amplitude differed significantly both in ST (P = .025) and LL recumbency (P = .009). The mean R wave amplitude was reduced in both ST and LL recumbency when compared with RL recumbency. The MEA only was significantly different in LL recumbency (P = .037). ST and LL recumbencies should not be used for recording ECGs in cats if amplitudes and MEA are to be compared with standard references.     

Electrocardiography of rock partridges (Alectoris graeca) and chukar partridges (Alectoris chukar).

Standard limb, six lead (I, II, III, aVR, aVL, and aVF) electrocardiograms (ECGs) were recorded in 10 awake mature rock partridges (Alectoris graeca) and 10 chukar partridges (Alectoris chukar). Durations and amplitudes of P and T waves and QRS complexes, durations of P-Q and Q-T intervals, and mean heart rates were calculated from the lead II ECGs. All observable P and T waves were negative in aVR and aVL, whereas they were positive in all remaining leads. The most frequent forms of QRS complex were r-s (r-S) and q-r (q-R). A Q wave was observed in all aVR and aVL leads in both species. Chukar partridges had significantly higher amplitudes of P and T waves and QRS complexes than rock partridges. Mean heart rates were 310+/-15 beats/min and 317+/-19 beats/min for chukar partridges and rock partridges, respectively. Mean electrical axes, calculated from leads II and III, were -99+/-6.3 degrees and -95+/-1.7 degrees for chukar partridges and rock partridges, respectively. Clear ECGs were easily obtainable without anesthesia or sedation.     

Electrocardiographic parameters of free-ranging roe deer (Capreolus capreolus).

Electrocardiographic parameters were measured in 28 free-ranging roe deer (Capreolus capreolus). The electrocardiograms (ECGs) were recorded in base-apex lead, standard bipolar limb leads (I, II, III), and augmented unipolar limb leads (aVR, aVL, aVF). Morphology and amplitude of P waves, QRS complexes, and T waves were analyzed in all seven leads. Cardiac rhythm, heart rate, and durations of P, QRS, and T waves, PR interval, QTc interval, and ST segment were calculated in the base-apex lead. The mean electrical axis for each individual was determined from the net amplitude of the QRS complex in leads I and II. All of the animals had a sinus rhythm. Heart rates ranged from 60-180 beats per minute, with a mean +/- SD of 104.8 +/- 44.1. The electrical axis was 100 degrees-220 degrees, with a mean +/- SD of 169.5 degrees +/- 40.8 degrees. The base-apex lead provided the most uniform ECG patterns and higher mean amplitudes than did standard leads.     

Electrocardiographic reference values in whippets

The aim of this study was to determine the electrocardiographic characteristics of whippets and to compare the results with published reference values for a general dog population. Electrocardiographic parameters from 105 healthy whippets were used to establish reference values for the breed.The most important differences compared to published reference values were the higher median R-wave amplitudes in leads II, CV₆LL and CV₆LU. For some parameters (P-wave amplitude, ST-segment deflection and T-wave amplitude in lead II; R-wave amplitude in CV₅RL), a marked percentage of the whippet values were above the published maximum reference data. The results confirmed that whippets have electrocardiographic characteristics similar to those reported in athletic heart syndrome in humans. Some of these characteristics could be erroneously taken as evidence of cardiac disease and clinicians should be aware of these factors to prevent unnecessary investigations in healthy dogs.     

Electrocardiographic Parameters in the Normal Lactating Holstein Cow

Electrocardiographic parameters in the normal lactating Holstein cow have been measured, computed and analyzed. The study was conducted on 32 animals of a mean age of 4.7 years. The recordings of the 12 leads (I, II, III, aVR, aVL, aVF, CV₆LU, CV₆LL, CV₆RL, CV₆RU, V₁₀ and base-apex) were made with a three channel electrocardiograph calibrated at 20 mm/mV and 25 mm/s. Conduction parameters, waves, intervals and segments have been measured. The recordings were analyzed as to shape, polarity and amplitude of the P and T waves and the components of the QRS complex. The results are discussed in respect to the morphophysiological characterestics of the bovine heart.     

The normal electrocardiogram of the unanesthetized peregrine falcon (Falco peregrinus brookei)

The mean duration and amplitudes of the lead II electrocardiogram were determined in the peregrine falcon (Falco peregrinus brookei) using 10 birds ranging in age from 1 to 5 yr. Electrocardiograms were performed on unanesthetized falcons in order to avoid the anesthesia effect on the electrocardiogram, by a method which seems to induce a tonic immobility-like reaction. All the falcons had a normal sinus rhythm, with a mean heart rate of 268 beats per minute. Mean durations of PR, ST, QT, and RR intervals were higher (but not statistically significant) in females than in males, except for the ST segment, with similar values in both sexes. P-wave deflections were positive in I, II, III, aVL, and aVF and negative in aVR. The normal patterns of wave forms of the QRS complexes in all leads were of QS and rS types, except for aVR and aVL, which presented an R configuration. The mean electrical axis was negative, with an average of -99.9 degrees. T-wave deflections were positive in I, II, III, and aVF leads II and negative in aVR and aVL. The data collected in this study may serve as a guide for electrocardiographic monitoring of peregrine falcons.     

Effects of endurance training on standard and signal-averaged electrocardiograms of sled dogs

OBJECTIVE: To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval. ANIMALS: 100 sled dogs in Alaska. PROCEDURE: Dogs were examined in early September (before training) and late March (after training). During the interim, dogs trained by pulling a sled with a musher (mean, 20 km/d). Standard and signal-averaged ECG were obtained before and after training. RESULTS: Endurance training significantly increased mean QRS duration by 4.4 milliseconds for standard ECG (mean +/- SEM; 62.3 +/- 0.7 to 66.7 +/- 0.6 milliseconds) and 4.3 milliseconds for signal-averaged ECG (51.5 +/- 0.7 to 55.8 +/- 0.6 milliseconds) without changing body weight. Increase in QRS duration corresponded to a calculated increase in heart weight (standard ECG, 23%; signal-averaged ECG, 27%). Signal-averaged QRS duration was correlated with echocardiographically determined left ventricular diastolic diameter for the X orthogonal lead (r = +0.41), Y orthogonal lead (r = +0.33), and vector (r = +0.35). Training also increased QT interval (234 +/- 2 to 249 +/- 2 milliseconds) and R-wave amplitude in leads II and rV2, increased peak-to-peak voltage and S-wave amplitude in the Y orthogonal lead, and decreased Q-wave amplitude in the Y orthogonal lead. CONCLUSIONS AND CLINICAL RELEVANCE: Electrocardiographic changes reflected physiologic cardiac hypertrophy in these canine athletes in response to repetitive endurance exercise. The QRS duration increases in response to endurance exercise training and, therefore, may be of use in predicting performance in endurance activities.     

The effects of intravenous ciprofloxacin on the electrocardiogram of healthy dogs

The purpose of this study was to evaluate the electrocardiographic effects of single intravenous dose of ciprofloxacin in dogs. Ten adult cross-breed dogs of both sexes were selected as the sample population. Baseline electrocardiographic values were recorded just before drug administration. Then the dogs received intravenous infusion of ciprofloxacin (10 mg/kg) over the fifteen minutes. The ECGs recorded at 15, 30, 60 and 120 minutes after ciprofloxacin administration. The ECG measurements of heart rate, PR interval, QRS interval, ST segment, T-wave amplitude and QT interval were taken from lead II. There was a small but significant increase in the longest QT intervals over baseline at T₆₀ (P = 0.041). The mean PR intervals, QTc intervals, JT intervals, ST segment, T-wave amplitude did not differ significantly before and after ciprofloxacin except for JT intervals at T₆₀ (P = 0.041). At this measurement point_, there was an increased QT interval value of 0.02 second or 9.51 % in comparison to the baseline. In Conclusions, Only minor QT intervals changes were observed after ciprofloxacin injection. Despite the occurrence of ECG changes following intravenous ciprofloxacin administration neither dangerous rhythm disturbances nor serious ECG changes were seen in this study.     

Effect of acute haemorrhage on QRS amplitude of the lead II canine electrocardiogram

OBJECTIVE: To examine the effect of acute haemorrhage on the QRS amplitude of the canine lead II surface electrocardiograph (ECG). DESIGN: Ten adult racing Greyhounds were tranquilised, anaesthetised, positioned in right lateral recumbency and connected to recording electrodes of an ECG unit. Baseline six-lead ECG traces were recorded, and further traces were obtained after one unit (460 mL) of blood, and then a second unit, were collected from the femoral artery. RESULTS: There was a consistent and progressive reduction in amplitude of the QRS complex in all leads during acute haemorrhage. QRS amplitude in lead II after removal of two units of blood averaged 74% of the baseline voltage, with individual values of 61 to 91% (P < 0.0001). There were even greater reductions in QRS amplitudes in lead aVL during haemorrhage. In three additional dogs, reductions in QRS voltages were shown to be accompanied by reductions in end-diastolic left ventricular internal dimensions measured echocardiographically. Furthermore, the effects of haemorrhage on the QRS amplitude and echocardiographic measurements were reversed when circulating blood volume was restored by re-infusion of blood removed previously. CONCLUSION: Acute haemorrhage corresponding to an approximately one-third reduction in blood volume caused a substantial reduction in QRS voltage of the surface ECG. It is postulated that this resulted from diminished ventricular distension as a consequence of reduced venous return. A similar mechanism may account for the small-amplitude ECG complexes associated with pericardial effusion, severe dehydration and hypovolaemia.     

ST segment depression and ventricular fibrillation in a dog after contrast agent administration

An 11-year-old Toy Poodle underwent a computed tomography examination with contrast (iohexol) enhancement under anesthesia. Heart rate and R-wave amplitude on electrocardiogram (ECG) increased 2.5 min after iohexol administration, and end-tidal carbon dioxide decreased to 12 mmHg. A progressive ST segment depression was observed on ECG. Subsequently, the ECG waveform changed to ventricular fibrillation. However, spontaneous circulation returned following cardiopulmonary resuscitation. Myocardial ischemia or anaphylactic shock was suspected in the dog, which explains the ST segment depression observed on ECG. When performing radiological examinations with a contrast agent, the ECG waveform changes, such as an increase in heart rate, R-wave amplitude, or ST segment depression, should be carefully monitored. This might enable early detection of cardiac dysfunction and the ensuing cardiac arrest in dogs.     

Effects of graded pleural effusion on QRS in the dog

Six anesthetized healthy dogs were placed in right lateral recumbency. Electrocardiographic leads I, aVF, V10, rV3, V3, and V5 were obtained during a control period and after introduction of pleural effusions ranging between 0.66 and 55 ml of isotonic saline solution/kg of body weight. Peak-to-peak amplitudes of QRS were measured, and the effusion required to decrease this amplitude by more than 1 SD from the mean of healthy dogs was determined for each lead tested. Sensitivity of detecting pleural effusion was greatest in lead I in which an effusion of 2.75 ml/kg could be detected. The QRS amplitudes in leads V10 and aVF were decreased to a significant level only at large effusions. Leads V3 and V5 were "blind," even to the greatest pleural effusions. Radiographs taken with the graded pleural effusion documented that the heart "floated" away from rV3 and toward V3 and V5, thus explaining the sensitivity of rV3 and insensitivities of V3 and V5. It seems that pleural effusion can be detected by using these leads in dogs in right lateral recumbency, that detection is best if serial recordings are taken, and that relatively high sensitivities are achieved using lead I.     

The normal electrocardiogram of the unanaesthetized competition "Spanish Pouler" pigeon (Columba livia gutturosa)

This investigation was carried out on 64 healthy adult competition pigeons (Spanish Poulers) to determine reference values of electrocardiographic parameters in standard lead II; a comparative study between males and females was also performed to find changes in the electrocardiographic patterns related to sex. P wave was positive and monophasic; PR segment depression was present in 64% of records; the QRS pattern obtained was in most cases of the rS type, followed by the QS configuration. ST slurring (absence of ST) was observed in 47% of records and the mean electrical axis was in all cases negative. Statistically significant differences related to sex were found for P-wave, R-wave and T-wave amplitudes, showing the males have greater amplitudes than females, associated with the increase of cardiac tissue mass. No sex-related differences were found in heart rate and mean electrical axis.     

Echocardiographic characterization of dilatation cardiomyopathy in the English cocker spaniel

The echocardiographic characterization of a dilatation cardiomyopathy in small-breed dogs is reported. Twelve clinically healthy adult English Cocker Spaniel dogs (between 2 and 9 years old and weighing 11.5 to 15.4 kg [mean 12.9 +/- 1.00 kg]) from a kennel population with a history of cardiomyopathy were assessed, using M-mode echocardiography. The dogs were selected on ECG and/or radiographic evidence of ventricular enlargement. Nine dogs had R-wave amplitude in lead 11 of greater than 3.0 mV. Two dogs had an unusual right-axis deviation, the result of deep Q waves in the limb leads and deep S waves in chest leads CV6LL and CV6LU, indicating that there was right ventricular enlargement. All dogs had increased end-systolic dimensions (mean 3.0 +/- 0.6 cm). End-diastolic dimensions were increased in 9 dogs (mean 4.0 +/- 0.5 cm), and there was a decrease of left ventricular (LV) function as measured by fractional shortening in 8 dogs. Mean fractional shortening for the 12 dogs was 25.4 +/- 5.7%. There was significant correlation between LV dimensions and age at echocardiographic assessment, indicating that LV dilatation was progressive. Three of the oldest dogs had severe dilatation of the LV, and in 2 of these, LV function was severely decreased. Left ventricular function in the 3rd dog, however, was within the acceptable range. Fractional shortening and thickness of the LV caudal wall and interventricular septum were significantly correlated (P less than 0.01 for interventricular system and P less than 0.05 for LV caudal wall).(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrocardiographic changes in the growing Mastín Español

Serial electrocardiograms were recorded from 70 Mastín Español dogs in right lateral recumbency, aged between one day and three years, in order to observe the changes in the waveform and intervals, QRS morphology, cardiac rhythm and heart rate caused by their growth. Age and bodyweight caused a gradual increase in the duration and amplitude of the P wave, duration of the PR, QT and RR intervals, amplitude of the R wave and duration of the QRS complex and ST segment. Q wave was observed in nearly all the recordings with different amplitudes. The S wave was only significant in one-day-old animals and QRS morphology showed significant important changes from qrS and rS to qR and qRs morphologies during the first two weeks of life. The T wave increased its amplitude until the age of two months and changed its polarity (from negative to positive) from five months of age onwards. The heart rate decreased until the age of seven months, reaching stabilised values of 110 ± 7-3 beats per minute. Sinus tachycardia was commonplace in animals under one month old and respiratory sinus arrhythmia was found from six months of age. Sex only influenced the duration and amplitude of the T wave. Males had higher mean values than females.     

Unipolar thoracic electrocardiography that induces QRS complexes of relative uniformity from male horses

Electrocardiograms were obtained from 100 male crossbred horses. In addition to standard limb leads, leads were taken from 12 points on the thorax. The QRS complexes were categorized into 1 of 8 forms on the basis of configuration and amplitudes of component deflections. Relative uniformity of QRS was determined for each lead, using the percentage of horses that possess a particular configuration. All unipolar thoracic leads, except those coplanar with the frontal plane, and lead aVR had great uniformity, with greater than 80% of the horses with a QRS of similar contour.     

A comparison of the brainstem auditory evoked response in healthy ears of unilaterally deaf dogs and bilaterally hearing dogs

Aims

Auditory plasticity in response to unilateral deafness has been reported in various animal species. Subcortical changes occurring in unilaterally deaf young dogs using the brainstem auditory evoked response have not been evaluated yet. The aim of this study was to assess the brainstem auditory evoked response findings in dogs with unilateral hearing loss, and compare them with recordings obtained from healthy dogs.

Methods

Brainstem auditory evoked responses (amplitudes and latencies of waves I, II, III, V, the V/I wave amplitude ratio, wave I-V, I-III and III-V interpeak intervals) were studied retrospectively in forty-six privately owned dogs, which were either unilaterally deaf or had bilateral hearing. The data obtained from the hearing ears in unilaterally deaf dogs were compared to values obtained from their healthy littermates.

Results

Statistically significant differences in the amplitude of wave III and the V/I wave amplitude ratio at 75 dB nHL were found between the group of unilaterally deaf puppies and the control group. The recordings of dogs with single-sided deafness were compared, and the results showed no statistically significant differences in the latencies and amplitudes of the waves between left- (AL) and right-sided (AR) deafness.

Conclusions

The recordings of the brainstem auditory evoked response in canines with unilateral inborn deafness in this study varied compared to recordings from healthy dogs. Future studies looking into electrophysiological assessment of hearing in conjunction with imaging modalities to determine subcortical auditory plasticity and auditory lateralization in unilaterally deaf dogs are warranted.

     

警犬正常心电图研究

描记了９０只警犬标准肢导联、加压单极肢导联、单极胸导联、Ａ－Ｂ导联等共２４个导联的心电图。结果显示，被检警犬皆为窦性心律，其心电图的性别差异不明显。此外，还分析了两种单极胸导联法的差异。     

Comparison of P-wave dispersion in healthy dogs,dogs with chronic valvular disease and dogs with disturbances of supraventricular conduction

Background

P-wave dispersion (P_d) is a new ECG index used in human cardiology and veterinary medicine. It is defined as the difference between the maximum and the minimum P-wave duration recorded from multiple different ECG leads. So far no studies were performed assessing the importance of P-wave dispersion in dogs.

Methods

The current study was aimed at determining proper value of P_d in healthy dogs (group I), dogs with chronic valvular disease (group II) and dogs with disturbances of supraventricular conduction (group III). The tests were carried out in 53 healthy dogs, 23 dogs with chronic valvular disease and 12 dogs with disturbances of supraventricular conduction of various breeds, sexes and body weight from 1,5 to 80 kg, aged between 0,5 and 17 years, submitted to the ECG examination. ECG was acquired in dogs in a standing position with BTL SD-8 electrocardiographic device and analyzed once the recording was enlarged. P-wave duration was calculated in 9 ECG leads (I, II, III, aVR, aVL, aVF, V1, V2, V4) from 5 cardiac cycles.

Results

The proper P-wave dispersion in healthy dogs was determined at up to 24 ms. P-wave dispersion was statistically significant increased (p < 0.01) in dogs with chronic valvular disease and dogs with disturbances of supraventricular conduction. In dogs with the atrial enlargement the P-wave dispersion is also higher than in healthy dogs, although no significant correlation between the size of left atria and Pd was noticed (p = 0.1, r = 0,17).

Conclusions

The P-wave dispersion is a constant index in healthy dogs, that is why it can be used for evaluating P wave change in dogs with chronic valvular disease and in dogs with disturbances of supraventricular conduction.     

Pulmonary arterial pressure and electrocardiograms in broiler chickens infused intravenously with L-NAME,an inhibitor of nitric oxide synthase,or sodium nitroprusside (SNP), a nitric oxide donor

1. Broilers were divided at 42 to 44 d of age into a Control group (n=30) and a Treatment group (n=30). The mean pulmonary arterial pressure (mPAP) and electrocardiogram (ECG) leads II and aV(F) were measured 1, 2 and 4 h after an intravenous injection of 0.9% saline (Control group) or Nomega-nitro-L-arginine methyl esther (L-NAME), an inhibitor of nitric oxide synthase and thus an inhibitor of endothelial nitric oxide (NO) production (Treatment group). 2. At 1 and 2 h but not 4 h post-injection, L-NAME significantly increased the mPAP and the amplitudes of the ECG S-wave and RS-wave leads II and aVF when compared with Control values. 3. The correlation coefficients between the mPAP and the ECG S-wave and RS-wave amplitudes for lead II within the Treatment group were -0.848 and -0.553 at 1 h and -0.798 and -0.512 at 2 h, respectively. The corresponding coefficients for lead aVF were -0.735, -0.596, -0.663 and -0.724, respectively. 4. After suitable mPAP and ECG values had been recorded at each time interval, sodium nitroprusside (SNP), which acts as a short-lived NO donor molecule, was injected intravenously via a right-cardiac catheter. Within 5 min after the SNP injection, the mPAP and the ECG lead II S-wave and RS-wave amplitudes were transiently reduced to levels that, at 1 and 2 h after L-NAME injection, did not differ from Control values. Within 10 min after the SNP injection, all values returned to the levels previously induced by L-NAME. 5. These results demonstrate that L-NAME increased the myocardial contractility and PAP, whereas SNP transiently reversed the effects of L-NAME on myocardial contractility and PAP. It appears likely from these results that the pulmonary vascular endothelium releases NO that in turn reduces the pulmonary vascular resistance or attenuates myocardial contractility in broiler chickens.